PCB Layout for BGAs...

[gnuarm.del...@gmail.com]

On Wednesday, January 11, 2023 at 5:26:48 AM UTC-5, David Brown wrote:

On 10/01/2023 23:17, gnuarm.del...@gmail.com wrote:

Yes, sorry, they do make a few multiplier chips with FPGA tiles. I
was referring to parts that I might be able to use. They have a
couple of 8 kLUT parts, only one in a package that I could use. I
can pick between a 0.8 mm ball pitch, or 0.65 mm. Not really excited
about either, even though there\'s a bit of inventory of the 256 ball,
0.8 mm part. But no insight into future deliveries.

This looking for usable parts gets old fast, and I\'ve been doing it
for over a year now. When I find the guy responsible for this
shortage, I\'m going to give him a piece of my mind!

The reason you can parts in high-density packages, but not low-density
packages, is that there are lots of people such as yourself who are so
reluctant to use the small pitch devices. (This is not criticism - you
have solid reasons for preferring larger pitch devices, as do many
others.) Big manufacturers often prefer smaller pitch and higher
density, as it can lead to lower overall costs for their products, even
if design is more costly and the pcbs are more expensive.

There have been component supply issues for several years now, with only
gradual improvement in many areas. But there is a general pattern of
somewhat higher availability in smaller pitch parts.

The very fine pitch parts are used to save space on the board. Some applications, like cell phones, simply require it. Not sure it saves any money, really. If you save on board size, you pay that back for finer pitch and laser drilled holes.

--

Rick C.

-++ Get 1,000 miles of free Supercharging
-++ Tesla referral code - https://ts.la/richard11209

 

[gnuarm.del...@gmail.com]

On Wednesday, January 11, 2023 at 5:42:23 AM UTC-5, David Brown wrote:

On 10/01/2023 23:44, gnuarm.del...@gmail.com wrote:
On Tuesday, January 10, 2023 at 1:35:24 PM UTC-5, Michael Schwingen
wrote:
On 2023-01-09, gnuarm.del...@gmail.com <gnuarm.del...@gmail.com
wrote:

I\'m concerned about adding cost for the boards, cost for the
assembly and just an easy road forward. I spend the last two
years building 8,000 units when the CODEC factory burnt down. The
customer knows about this issue, but the previous CM turned flaky
on me and all but stopped delivering product.

I have a new CM, but I don\'t want to go through production
problems again.
0.8mm BGA should be no problem for any reputable CM - fine-pitch
QFP is usually more trouble.

Part of my problem is a lack of having designed with BGAs before. I
can find footprint recommendations, but they are different for every
manufacturer. It didn\'t occur to me that this might be because even
though they have the same pitch and ball count, they may not have the
same ball size.

The two primary choices right now are a 196 ball, 1.0 mm pitch and
256 ball, 0.8 mm pitch. Can you share the design rules you used for
these parts?

The board stackup, routing and bypassing recommendations from FPGA
manufacturers are basically bollocks. I believe it is primarily a
matter of being able to fob off complaints and support requests by
saying \"Did you follow our layout application notes, impossible though
they may be? If not, it\'s not /our/ fault that you have problems.\"

OK, that\'s a bit of an exaggeration, but you can ignore the suggestions
of 16 layers with 8 different power planes and a dozen different
capacitor sizes mounted directly below the device.

I see the opposite. When FPGA makers offer routing suggestions, they often provide one for routing of 100% of I/O pins, and another, using fewer layers, routing a portion of the I/O pins. So clearly they are trying to optimize cost of the boards for the user. No sign of CYA.

Yes, there are complications for BGA layouts. And I\'m afraid you are
going to have to do some research, some learning, and some discussions
with both PCB manufacturers (or their proxies) and board builders.

For the same pitch of BGA, there can be different sized balls, and
different sized pads on the underside of the BGA device which will
affect the shape of the ball after soldering.

I haven\'t done a survey to check this yet. Do you know this for a fact?

Pad size on the pcb has
different options. You have a key decision between solder mask defined
and non-solder mask defined pads, which affects mechanical strength,
thermal stability, solder paste masks, routeability, and manufacturing
requirements. And BGA soldering has different requirements in
production than non-BGA devices.


I have no doubt that this is something you can master quite quickly -
it\'s not /that/ hard. But it\'s not something you can learn just by a
thread on a newsgroup.

It\'s not \"hard\", it\'s \"hard\" to find the information for layout recommendations from each FPGA vendor. I\'m going to need to put together a compendium of layout information, before I can compare vendors. The vendors may make it easy for me, based on availability and pricing. Xilinx is not in the running unless I can get someone there to give assurance of better supply in six months. Right now I\'ll have to buy every part in inventory of several combinations of speed and temperature, to build the order I have coming.

--

Rick C.

+-- Get 1,000 miles of free Supercharging
+-- Tesla referral code - https://ts.la/richard11209

 

[Michael Schwingen]

On 2023-01-10, gnuarm.del...@gmail.com <gnuarm.deletethisbit@gmail.com> wrote:

Part of my problem is a lack of having designed with BGAs before. I can
find footprint recommendations, but they are different for every
manufacturer. It didn\'t occur to me that this might be because even
though they have the same pitch and ball count, they may not have the same
ball size.

The two primary choices right now are a 196 ball, 1.0 mm pitch and 256
ball, 0.8 mm pitch. Can you share the design rules you used for these
parts?

I have a 529 pin BGA with 0.8mm pitch. SMD pads for the BGA are 0.4mm, vias
are also 0.4mm with 0.2mm drill. Using these rules, a via fits nicely
between 4 BGA pads.

I have plugged/plated vias in order to put 0402/0201 capacitors underneath
the BGA, but if you can place the capacitors outside the BGA area, normal
vias should do.

Talk to your PCB manufacturer about the details before doing the final
layout - there is some fine tuning (eg. drill size, annular ring, spacing)
where different PCB manufacturers have different preferences regarding which
rules will yield good results - when doing do, 0.8mm BGA should be possible
at modest PCB costs.

You mean my CM who orders the PWBs? Yeah, I\'ve tried asking before and
they say they would need a design so they could get a quote. I know, that
sounds lame, but I used four different CMs over the last decade and they
have all said the same thing. They don\'t have design rules, that\'s for me
to know.

OK, if you do not order the PCBs yourself, you have to forward this through
your CM. You will probably have to prepare a sample design (just the BGA
area with fanout), produce gerbers, and have them ask for feedback. Same
about the layer stackup if you need controlled impedances.

cu
Michael
--
Some people have no respect of age unless it is bottled.

 

[gnuarm.del...@gmail.com]

On Wednesday, January 11, 2023 at 1:06:01 PM UTC-4, Michael Schwingen wrote:

On 2023-01-10, gnuarm.del...@gmail.com <gnuarm.del...@gmail.com> wrote:

Part of my problem is a lack of having designed with BGAs before. I can
find footprint recommendations, but they are different for every
manufacturer. It didn\'t occur to me that this might be because even
though they have the same pitch and ball count, they may not have the same
ball size.

The two primary choices right now are a 196 ball, 1.0 mm pitch and 256
ball, 0.8 mm pitch. Can you share the design rules you used for these
parts?
I have a 529 pin BGA with 0.8mm pitch. SMD pads for the BGA are 0.4mm, vias
are also 0.4mm with 0.2mm drill. Using these rules, a via fits nicely
between 4 BGA pads.

You would need to use 5 mil trace and space to get between the pads. That doesn\'t sound too bad. Via to pad is 6.5 mil, again good.

Where did you get your pad size numbers? Your via pad only gives you 4 mil annular ring. That sounds a bit tight. To make that a 5 mil annular ring would shorten the 6.5 mil via to pad space to 5.5 mil, still good. Why did you choose a 0.4 mm pad?

I have plugged/plated vias in order to put 0402/0201 capacitors underneath
the BGA, but if you can place the capacitors outside the BGA area, normal
vias should do.
Talk to your PCB manufacturer about the details before doing the final
layout - there is some fine tuning (eg. drill size, annular ring, spacing)
where different PCB manufacturers have different preferences regarding which
rules will yield good results - when doing do, 0.8mm BGA should be possible
at modest PCB costs.

You mean my CM who orders the PWBs? Yeah, I\'ve tried asking before and
they say they would need a design so they could get a quote. I know, that
sounds lame, but I used four different CMs over the last decade and they
have all said the same thing. They don\'t have design rules, that\'s for me
to know.
OK, if you do not order the PCBs yourself, you have to forward this through
your CM. You will probably have to prepare a sample design (just the BGA
area with fanout), produce gerbers, and have them ask for feedback. Same
about the layer stackup if you need controlled impedances.

I asked my CM the general question of their BGA assembly experience and an estimated cost increment for going from a 100QFP to the 196 ball, 1.0 mm pitch BGA and 256 ball, 0.8 mm BGA. We\'ll see what they come up with. If they can give me a dollar figure, they should be able to give me dimensions they are comfortable working with.

Thanks for discussing this with me.

--

Rick C.

+-+ Get 1,000 miles of free Supercharging
+-+ Tesla referral code - https://ts.la/richard11209

 

[David Brown]

On 11/01/2023 13:49, gnuarm.del...@gmail.com wrote:

On Wednesday, January 11, 2023 at 5:42:23 AM UTC-5, David Brown
wrote:
On 10/01/2023 23:44, gnuarm.del...@gmail.com wrote:
On Tuesday, January 10, 2023 at 1:35:24 PM UTC-5, Michael
Schwingen wrote:
On 2023-01-09, gnuarm.del...@gmail.com
gnuarm.del...@gmail.com> wrote:

I\'m concerned about adding cost for the boards, cost for the
assembly and just an easy road forward. I spend the last two
years building 8,000 units when the CODEC factory burnt down.
The customer knows about this issue, but the previous CM
turned flaky on me and all but stopped delivering product.

I have a new CM, but I don\'t want to go through production
problems again.
0.8mm BGA should be no problem for any reputable CM -
fine-pitch QFP is usually more trouble.

Part of my problem is a lack of having designed with BGAs before.
I can find footprint recommendations, but they are different for
every manufacturer. It didn\'t occur to me that this might be
because even though they have the same pitch and ball count, they
may not have the same ball size.

The two primary choices right now are a 196 ball, 1.0 mm pitch
and 256 ball, 0.8 mm pitch. Can you share the design rules you
used for these parts?

The board stackup, routing and bypassing recommendations from FPGA
manufacturers are basically bollocks. I believe it is primarily a
matter of being able to fob off complaints and support requests by
saying \"Did you follow our layout application notes, impossible
though they may be? If not, it\'s not /our/ fault that you have
problems.\"

OK, that\'s a bit of an exaggeration, but you can ignore the
suggestions of 16 layers with 8 different power planes and a dozen
different capacitor sizes mounted directly below the device.

I see the opposite. When FPGA makers offer routing suggestions, they
often provide one for routing of 100% of I/O pins, and another, using
fewer layers, routing a portion of the I/O pins. So clearly they are
trying to optimize cost of the boards for the user. No sign of
CYA.

Fair enough. Certainly you want to look at all the information you can
here - you just have to be aware that some of it will be conflicting,
and some of it will be overkill. I read somewhere (a long time ago, and
I\'ve forgotten the details) of someone who initially made their design
following application notes for bypass capacitors. Then to save costs,
they depopulated about 90% of these capacitors, basically at random.
There were no measurable differences in signal integrity, EMC results,
or any functionality.

Yes, there are complications for BGA layouts. And I\'m afraid you
are going to have to do some research, some learning, and some
discussions with both PCB manufacturers (or their proxies) and
board builders.

For the same pitch of BGA, there can be different sized balls, and
different sized pads on the underside of the BGA device which will
affect the shape of the ball after soldering.

I haven\'t done a survey to check this yet. Do you know this for a
fact?

Yes.

BGA balls are attached to circular pads on the underside of the BGA
package, and the size of these pads can be different for different
packages with the same pitch. In general, you get the mechanically
strongest bond when the pads on the pcb (or the opening in the solder
mask, for solder mask defined pads) is the same size. But that does not
mean you /always/ want them to be the same as there are other factors in
the trade-offs, and it\'s quite rare that mechanical strength is
critical. (If you are gluing on a large heatsink, without screws, and
then mounting the board upside down in a high vibration environment,
you\'ll have different requirements from a \"normal\" usage.)

Pad size on the pcb has different options. You have a key decision
between solder mask defined and non-solder mask defined pads, which
affects mechanical strength, thermal stability, solder paste masks,
routeability, and manufacturing requirements. And BGA soldering has
different requirements in production than non-BGA devices.


I have no doubt that this is something you can master quite quickly
- it\'s not /that/ hard. But it\'s not something you can learn just
by a thread on a newsgroup.

It\'s not \"hard\", it\'s \"hard\" to find the information for layout
recommendations from each FPGA vendor. I\'m going to need to put
together a compendium of layout information, before I can compare
vendors. The vendors may make it easy for me, based on availability
and pricing. Xilinx is not in the running unless I can get someone
there to give assurance of better supply in six months. Right now
I\'ll have to buy every part in inventory of several combinations of
speed and temperature, to build the order I have coming.

That\'s the unfortunate reality these days. Find out what you can get
hold of, check if it looks good enough, then buy the stock. There\'s no
point in finding out that vendor X has good layout and manufacturing
information, or vendor Y has good toolchains, if you can only get parts
from vendor Z. (This is not news to you, of course - I\'m just
sympathising.)

 

[Michael Schwingen]

On 2023-01-12, gnuarm.del...@gmail.com <gnuarm.deletethisbit@gmail.com> wrote:

I have a 529 pin BGA with 0.8mm pitch. SMD pads for the BGA are 0.4mm, vias
are also 0.4mm with 0.2mm drill. Using these rules, a via fits nicely
between 4 BGA pads.

You would need to use 5 mil trace and space to get between the pads. That
doesn\'t sound too bad. Via to pad is 6.5 mil, again good.

Trace width in the BGA area is 0.11mm (for data lines).

Where did you get your pad size numbers? Your via pad only gives you 4
mil annular ring. That sounds a bit tight.
To make that a 5 mil annular
ring would shorten the 6.5 mil via to pad space to 5.5 mil, still good.
Why did you choose a 0.4 mm pad?

That is the minimum given by our PCB manufacturer - small via pads allow for
bigger traces where needed (power traces, despite using a 8-layer PCB).

That is the area where you can fine tune after discussion with your PCB
manufacturer. Some may like a bigger annular ring, some may prefer smaller
ring and more pad-to-trace clearance.

https://www.nxp.com/docs/en/package-information/PBGAPRES.pdf

has some information about the BGA pad design. Our BGA has 0.45mm pads on
the BGA side, so the 0.4mm pads are on the lower end of the recommended
range.

I asked my CM the general question of their BGA assembly experience and an
estimated cost increment for going from a 100QFP to the 196 ball, 1.0 mm
pitch BGA and 256 ball, 0.8 mm BGA. We\'ll see what they come up with. If
they can give me a dollar figure, they should be able to give me
dimensions they are comfortable working with.

I would expect pick & place to be easier for the 0.8mm BGA than the TQFP.
Cost increase will probably happen at the PCB level (small annular ring, or
more expensive surface finish - TQFP may work with HASL, BGA needs a flatter
finish. However, ENIG is not that expensive nowadays.)

cu
Michael
--
Some people have no respect of age unless it is bottled.

 

[David Brown]

On 12/01/2023 14:36, Michael Schwingen wrote:

On 2023-01-12, gnuarm.del...@gmail.com <gnuarm.deletethisbit@gmail.com> wrote:

I asked my CM the general question of their BGA assembly experience and an
estimated cost increment for going from a 100QFP to the 196 ball, 1.0 mm
pitch BGA and 256 ball, 0.8 mm BGA. We\'ll see what they come up with. If
they can give me a dollar figure, they should be able to give me
dimensions they are comfortable working with.

I would expect pick & place to be easier for the 0.8mm BGA than the TQFP.
Cost increase will probably happen at the PCB level (small annular ring, or
more expensive surface finish - TQFP may work with HASL, BGA needs a flatter
finish. However, ENIG is not that expensive nowadays.)

Yes, BGAs can often be easier to place than TQFP\'s - you have a bigger
pitch, and they \"float\" to the correct place even if there is a slight
placement error.

On the other hand, you need better control of the soldering parameters,
and they are harder if you have a board that has awkward heat flow -
many high components nearby, or big thermal masses. And it is harder to
check connectivity and good quality soldering.

A good production facility will have tools to help here. They will do
the first boards with temperature probes between the balls, and X-Ray to
check the quality of the soldering. Make sure you have a production
house that is not scared to give you feedback - many far eastern places
will just do their best with what you give them, and never tell you how
to improve your layout.

Re-work is, obviously, far more difficult with BGAs.

 

[John Larkin]

On Sat, 7 Jan 2023 09:49:24 -0800 (PST), \"gnuarm.del...@gmail.com\"
<gnuarm.deletethisbit@gmail.com> wrote:

A small board with a 100QFP is being redesigned for a new FPGA due to obsolescence. Gowin makes a 100QFP device that would be a good fit, but my customer has said \"no\" to the 100% Chinese brand... US government customers, ya know!

So now I\'m looking at a BGA. I don\'t want to get into fine PCB design rules, so 1.0 mm ball pitch is my preference. The only devices I can find that fit on the board have 196 or 256 pins. But the real problem is availability.

Digikey has a few of the XC7S15-1FTGB196I and more a scheduled for delivery in April. Add in the various speed and temperature flavors trickling in (mostly in April) and I should be ok for the initial delivery in August... if I can get my hands on those. I don\'t know if Digikey factors in the backlog orders in these counts.

Mouser shows great inventory of Efinix parts, particularly the T13 and T20 in a 0.8 mm 256 pin BGA, 10s of thousands in stock. But I\'d rather work with a 1.0 mm BGA. Oddly enough, LCSC shows part numbers, but zero inventory.

Anyone work with 0.8 mm BGAs? What PWB feature dimensions did you use? Did this impact the PWB cost?

The 0.8 mm 256-ball T20 isn\'t bad...

https://www.dropbox.com/s/xjqgj2pz9mdhtma/P941_FPGA.jpg?raw=1

The BGA pads are 16 mils. 8 mil drills on the BGA vias. 6 mil traces
mostly, except for the 50 ohm monsters. No big deal these days. Works
great.

We considered a T8 for a simpler application, but its 0.5 mm ball
pitch looked nasty.

The efinix tool chain looks like it was developed in someone\'s garage,
which is actually praise. It\'s free and simple and just works without
200 gbyte downloads and doing battle with FlexLM.

 

[gnuarm.del...@gmail.com]

On Saturday, January 14, 2023 at 12:39:49 AM UTC-4, John Larkin wrote:

On Sat, 7 Jan 2023 09:49:24 -0800 (PST), \"gnuarm.del...@gmail.com\"
gnuarm.del...@gmail.com> wrote:

A small board with a 100QFP is being redesigned for a new FPGA due to obsolescence. Gowin makes a 100QFP device that would be a good fit, but my customer has said \"no\" to the 100% Chinese brand... US government customers, ya know!

So now I\'m looking at a BGA. I don\'t want to get into fine PCB design rules, so 1.0 mm ball pitch is my preference. The only devices I can find that fit on the board have 196 or 256 pins. But the real problem is availability.

Digikey has a few of the XC7S15-1FTGB196I and more a scheduled for delivery in April. Add in the various speed and temperature flavors trickling in (mostly in April) and I should be ok for the initial delivery in August... if I can get my hands on those. I don\'t know if Digikey factors in the backlog orders in these counts.

Mouser shows great inventory of Efinix parts, particularly the T13 and T20 in a 0.8 mm 256 pin BGA, 10s of thousands in stock. But I\'d rather work with a 1.0 mm BGA. Oddly enough, LCSC shows part numbers, but zero inventory.

Anyone work with 0.8 mm BGAs? What PWB feature dimensions did you use? Did this impact the PWB cost?
The 0.8 mm 256-ball T20 isn\'t bad...

https://www.dropbox.com/s/xjqgj2pz9mdhtma/P941_FPGA.jpg?raw=1

I can\'t really see much detail. It looks like there are virtually no pads on the vias under the BGA. What size are they?

The BGA pads are 16 mils. 8 mil drills on the BGA vias. 6 mil traces
mostly, except for the 50 ohm monsters. No big deal these days. Works
great.

Yeah, 0.8 mm pad centers are doable, but I don\'t know where the line is for higher pricing on the PWB. The via pads seem to be pushing the technology line at JLCPCB. Not that I\'m using them, but if they can do it, pretty much anyone should be able to do it. They build 0.45 mm via pads and 0.2 mm drills (5 mil annular ring and 8 mil drill), but charge extra for a 0.4 mm via pads (4 mil annular ring).

We considered a T8 for a simpler application, but its 0.5 mm ball
pitch looked nasty.

I didn\'t price the T8, because they use the logic cells for routing in a way they don\'t explain, so no way to factor it in. The T12 would be gravy for my design I expect, but it\'s only $1 more for the T20, so why not? If it saves a day of work, it\'s a break even for 1,000 units. If it enables a future expansion, it\'s worth much more than that! Both parts seem to have the same pin out, including I/O counts, so switching between them should only be a recompile.

The efinix tool chain looks like it was developed in someone\'s garage,
which is actually praise. It\'s free and simple and just works without
200 gbyte downloads and doing battle with FlexLM.

The large downloads are from the support for the many, many products the big three FPGA companies sell. Don\'t expect Efinix tools to continue to be small... and they aren\'t really free. You have to buy a board. That\'s more than I\'ve paid for tools from FPGA vendors.

I\'d really like to use the Gowin parts (LQFP100). But the customer is hinky about parts from a Chinese company. They sell stuff to the US Government..

--

Rick C.

++- Get 1,000 miles of free Supercharging
++- Tesla referral code - https://ts.la/richard11209

 

[John Larkin]

On Fri, 13 Jan 2023 21:20:50 -0800 (PST), \"gnuarm.del...@gmail.com\"
<gnuarm.deletethisbit@gmail.com> wrote:

On Saturday, January 14, 2023 at 12:39:49 AM UTC-4, John Larkin wrote:
On Sat, 7 Jan 2023 09:49:24 -0800 (PST), \"gnuarm.del...@gmail.com\"
gnuarm.del...@gmail.com> wrote:

A small board with a 100QFP is being redesigned for a new FPGA due to obsolescence. Gowin makes a 100QFP device that would be a good fit, but my customer has said \"no\" to the 100% Chinese brand... US government customers, ya know!

So now I\'m looking at a BGA. I don\'t want to get into fine PCB design rules, so 1.0 mm ball pitch is my preference. The only devices I can find that fit on the board have 196 or 256 pins. But the real problem is availability.

Digikey has a few of the XC7S15-1FTGB196I and more a scheduled for delivery in April. Add in the various speed and temperature flavors trickling in (mostly in April) and I should be ok for the initial delivery in August... if I can get my hands on those. I don\'t know if Digikey factors in the backlog orders in these counts.

Mouser shows great inventory of Efinix parts, particularly the T13 and T20 in a 0.8 mm 256 pin BGA, 10s of thousands in stock. But I\'d rather work with a 1.0 mm BGA. Oddly enough, LCSC shows part numbers, but zero inventory.

Anyone work with 0.8 mm BGAs? What PWB feature dimensions did you use? Did this impact the PWB cost?
The 0.8 mm 256-ball T20 isn\'t bad...

https://www.dropbox.com/s/xjqgj2pz9mdhtma/P941_FPGA.jpg?raw=1

I can\'t really see much detail. It looks like there are virtually no pads on the vias under the BGA. What size are they?

The BGAVIAs are 12.5 mil OD with 8 mil drills. The other vias on the
board STANDARDVIA and POWERVIA are bigger.

I have seen vias with no annullar ring, just a trace falling into a
hole, but the PCB houses don\'t like that.

Filled via-in-pad would be cool but that\'s complex and expensive. As
is buried vias.

The BGA pads are 16 mils. 8 mil drills on the BGA vias. 6 mil traces
mostly, except for the 50 ohm monsters. No big deal these days. Works
great.

Yeah, 0.8 mm pad centers are doable, but I don\'t know where the line is for higher pricing on the PWB. The via pads seem to be pushing the technology line at JLCPCB. Not that I\'m using them, but if they can do it, pretty much anyone should be able to do it. They build 0.45 mm via pads and 0.2 mm drills (5 mil annular ring and 8 mil drill), but charge extra for a 0.4 mm via pads (4 mil annular ring).

We use US suppliers for production boards, and they seem to think this
6-layer board is within the normal range. One advantage to using a big
FPGA (256 balls in this case) is that you don\'t have to go deep to hit
enough balls, so may save a PCB layer or two. The T20-256 is a nice
part and Digikey has 29,000 in stock.

Another project used a 484 ball Zynq and we used almost every ball.
Lots of different power pours too. That took 10 layers. Another recent
board has a 400-ball ZYNQ with a few unused PS pins and fits on 8
layers.

The ZYNQ has analog inputs but, crazily, they are all differential so
they make you ground a perfectly good i/o pin for every analog input
that you want.

We considered a T8 for a simpler application, but its 0.5 mm ball
pitch looked nasty.

I didn\'t price the T8, because they use the logic cells for routing in a way they don\'t explain, so no way to factor it in. The T12 would be gravy for my design I expect, but it\'s only $1 more for the T20, so why not? If it saves a day of work, it\'s a break even for 1,000 units. If it enables a future expansion, it\'s worth much more than that! Both parts seem to have the same pin out, including I/O counts, so switching between them should only be a recompile.


The efinix tool chain looks like it was developed in someone\'s garage,
which is actually praise. It\'s free and simple and just works without
200 gbyte downloads and doing battle with FlexLM.

The large downloads are from the support for the many, many products the big three FPGA companies sell. Don\'t expect Efinix tools to continue to be small... and they aren\'t really free. You have to buy a board. That\'s more than I\'ve paid for tools from FPGA vendors.

$150! That\'s in the noise, and an eval board is good anyhow.

I\'d really like to use the Gowin parts (LQFP100). But the customer is hinky about parts from a Chinese company. They sell stuff to the US Government.

Yeah, we have a lot of aerospace customers and avoid Chinese parts.

 

[gnuarm.del...@gmail.com]

On Saturday, January 14, 2023 at 12:08:03 PM UTC-4, John Larkin wrote:

On Fri, 13 Jan 2023 21:20:50 -0800 (PST), \"gnuarm.del...@gmail.com\"
gnuarm.del...@gmail.com> wrote:

On Saturday, January 14, 2023 at 12:39:49 AM UTC-4, John Larkin wrote:
On Sat, 7 Jan 2023 09:49:24 -0800 (PST), \"gnuarm.del...@gmail.com\"
gnuarm.del...@gmail.com> wrote:

A small board with a 100QFP is being redesigned for a new FPGA due to obsolescence. Gowin makes a 100QFP device that would be a good fit, but my customer has said \"no\" to the 100% Chinese brand... US government customers, ya know!

So now I\'m looking at a BGA. I don\'t want to get into fine PCB design rules, so 1.0 mm ball pitch is my preference. The only devices I can find that fit on the board have 196 or 256 pins. But the real problem is availability.

Digikey has a few of the XC7S15-1FTGB196I and more a scheduled for delivery in April. Add in the various speed and temperature flavors trickling in (mostly in April) and I should be ok for the initial delivery in August.... if I can get my hands on those. I don\'t know if Digikey factors in the backlog orders in these counts.

Mouser shows great inventory of Efinix parts, particularly the T13 and T20 in a 0.8 mm 256 pin BGA, 10s of thousands in stock. But I\'d rather work with a 1.0 mm BGA. Oddly enough, LCSC shows part numbers, but zero inventory.

Anyone work with 0.8 mm BGAs? What PWB feature dimensions did you use? Did this impact the PWB cost?
The 0.8 mm 256-ball T20 isn\'t bad...

https://www.dropbox.com/s/xjqgj2pz9mdhtma/P941_FPGA.jpg?raw=1

I can\'t really see much detail. It looks like there are virtually no pads on the vias under the BGA. What size are they?
The BGAVIAs are 12.5 mil OD with 8 mil drills. The other vias on the
board STANDARDVIA and POWERVIA are bigger.

2.25 mil (0.057 mm) is a pretty narrow via ring. Why not have a larger via pad? You have just over 0.2 mm (8 mil) clearance between via pad and BGA pads. Is this narrow annular ring buying you something? You could use a 0..4 mm (16 mil) via pad for an annular ring of 0.1 mm (4 mil) and still have 0.165 mm (6.5 mil) clearance between ball pads and via pads. Do you feel that\'s not enough?

I have seen vias with no annullar ring, just a trace falling into a
hole, but the PCB houses don\'t like that.

No, and they don\'t like small annular rings, because that\'s a small target to drill. I run into boards that the PCB fab house made badly at the vias and they are disasters. The tiny cracks that develop are hard to find and don\'t repair well.

Efinix recommends 0.46 mm (18.1 mil) ball pad, 0.5 mm (20 mil) via pad and a 0.25 mm (10 mil) drill, with 0.1 mm (4 mil) trace/space and 0.085 mm (3.3 mil) clearance between ball pad and via pad. The trace/space seems fine, but I\'d like more clearance between via and ball pads. The question is, where to shave it from? Shaving 2 mil from the via pad leaves 4 mil annular ring and 4.3 mil clearance. Shaving from the ball pad seems like a bad idea. But if it works...

This is something that should have a spreadsheet, with a diagram that adjusts the image to show the details. All the tradeoffs become apparent very quickly. lol

Filled via-in-pad would be cool but that\'s complex and expensive. As
is buried vias.


The BGA pads are 16 mils. 8 mil drills on the BGA vias. 6 mil traces
mostly, except for the 50 ohm monsters. No big deal these days. Works
great.

Yeah, 0.8 mm pad centers are doable, but I don\'t know where the line is for higher pricing on the PWB. The via pads seem to be pushing the technology line at JLCPCB. Not that I\'m using them, but if they can do it, pretty much anyone should be able to do it. They build 0.45 mm via pads and 0.2 mm drills (5 mil annular ring and 8 mil drill), but charge extra for a 0.4 mm via pads (4 mil annular ring).
We use US suppliers for production boards, and they seem to think this
6-layer board is within the normal range. One advantage to using a big
FPGA (256 balls in this case) is that you don\'t have to go deep to hit
enough balls, so may save a PCB layer or two. The T20-256 is a nice
part and Digikey has 29,000 in stock.

I don\'t follow that exactly. If I could get a 100 ball BGA on 1.0 mm centers, I would have zero trouble with routing and breakout. That could be routed 100% on a double sided board. One side gets the two outer rings of pads leaving 6x6. The other layer routes the remainder. But FPGA companies don\'t like small packages. They have much more demand at the larger I/O counts. Xilinx has a 196 ball, 1.0 mm package, but not much inventory and lead time is the standard 52 weeks.

The real problem is having to use the packages that are in stock. Everything other than Efinix is 52 week lead time, which is not a real forecast, rather just the point where they stop counting.

Another project used a 484 ball Zynq and we used almost every ball.
Lots of different power pours too. That took 10 layers. Another recent
board has a 400-ball ZYNQ with a few unused PS pins and fits on 8
layers.

Yeah, when you have that many I/Os, it\'s tough to keep the layer count down..

The ZYNQ has analog inputs but, crazily, they are all differential so
they make you ground a perfectly good i/o pin for every analog input
that you want.


We considered a T8 for a simpler application, but its 0.5 mm ball
pitch looked nasty.

I didn\'t price the T8, because they use the logic cells for routing in a way they don\'t explain, so no way to factor it in. The T12 would be gravy for my design I expect, but it\'s only $1 more for the T20, so why not? If it saves a day of work, it\'s a break even for 1,000 units. If it enables a future expansion, it\'s worth much more than that! Both parts seem to have the same pin out, including I/O counts, so switching between them should only be a recompile.


The efinix tool chain looks like it was developed in someone\'s garage,
which is actually praise. It\'s free and simple and just works without
200 gbyte downloads and doing battle with FlexLM.

The large downloads are from the support for the many, many products the big three FPGA companies sell. Don\'t expect Efinix tools to continue to be small... and they aren\'t really free. You have to buy a board. That\'s more than I\'ve paid for tools from FPGA vendors.
$150! That\'s in the noise, and an eval board is good anyhow.

I\'d really like to use the Gowin parts (LQFP100). But the customer is hinky about parts from a Chinese company. They sell stuff to the US Government.
Yeah, we have a lot of aerospace customers and avoid Chinese parts.

Where exactly are Efinix parts made? Their parts say China on them.

--

Rick C.

+++ Get 1,000 miles of free Supercharging
+++ Tesla referral code - https://ts.la/richard11209

 

[John Larkin]

On Sat, 14 Jan 2023 10:05:33 -0800 (PST), \"gnuarm.del...@gmail.com\"
<gnuarm.deletethisbit@gmail.com> wrote:

On Saturday, January 14, 2023 at 12:08:03 PM UTC-4, John Larkin wrote:
On Fri, 13 Jan 2023 21:20:50 -0800 (PST), \"gnuarm.del...@gmail.com\"
gnuarm.del...@gmail.com> wrote:

On Saturday, January 14, 2023 at 12:39:49 AM UTC-4, John Larkin wrote:
On Sat, 7 Jan 2023 09:49:24 -0800 (PST), \"gnuarm.del...@gmail.com\"
gnuarm.del...@gmail.com> wrote:

A small board with a 100QFP is being redesigned for a new FPGA due to obsolescence. Gowin makes a 100QFP device that would be a good fit, but my customer has said \"no\" to the 100% Chinese brand... US government customers, ya know!

So now I\'m looking at a BGA. I don\'t want to get into fine PCB design rules, so 1.0 mm ball pitch is my preference. The only devices I can find that fit on the board have 196 or 256 pins. But the real problem is availability.

Digikey has a few of the XC7S15-1FTGB196I and more a scheduled for delivery in April. Add in the various speed and temperature flavors trickling in (mostly in April) and I should be ok for the initial delivery in August... if I can get my hands on those. I don\'t know if Digikey factors in the backlog orders in these counts.

Mouser shows great inventory of Efinix parts, particularly the T13 and T20 in a 0.8 mm 256 pin BGA, 10s of thousands in stock. But I\'d rather work with a 1.0 mm BGA. Oddly enough, LCSC shows part numbers, but zero inventory.

Anyone work with 0.8 mm BGAs? What PWB feature dimensions did you use? Did this impact the PWB cost?
The 0.8 mm 256-ball T20 isn\'t bad...

https://www.dropbox.com/s/xjqgj2pz9mdhtma/P941_FPGA.jpg?raw=1

I can\'t really see much detail. It looks like there are virtually no pads on the vias under the BGA. What size are they?
The BGAVIAs are 12.5 mil OD with 8 mil drills. The other vias on the
board STANDARDVIA and POWERVIA are bigger.

2.25 mil (0.057 mm) is a pretty narrow via ring. Why not have a larger via pad?

I don\'t know. My PCB guy decides stuff like that. I\'d guess that he
wanted it to pass some design rule check, or maybe he started metric.
The board houses haven\'t complained as far as I know.

You should do your own thing and check with whoever will make your
boards.

 

[gnuarm.del...@gmail.com]

On Saturday, January 14, 2023 at 3:17:24 PM UTC-4, John Larkin wrote:

On Sat, 14 Jan 2023 10:05:33 -0800 (PST), \"gnuarm.del...@gmail.com\"
gnuarm.del...@gmail.com> wrote:

On Saturday, January 14, 2023 at 12:08:03 PM UTC-4, John Larkin wrote:
On Fri, 13 Jan 2023 21:20:50 -0800 (PST), \"gnuarm.del...@gmail.com\"
gnuarm.del...@gmail.com> wrote:

On Saturday, January 14, 2023 at 12:39:49 AM UTC-4, John Larkin wrote:
On Sat, 7 Jan 2023 09:49:24 -0800 (PST), \"gnuarm.del...@gmail.com\"
gnuarm.del...@gmail.com> wrote:

A small board with a 100QFP is being redesigned for a new FPGA due to obsolescence. Gowin makes a 100QFP device that would be a good fit, but my customer has said \"no\" to the 100% Chinese brand... US government customers, ya know!

So now I\'m looking at a BGA. I don\'t want to get into fine PCB design rules, so 1.0 mm ball pitch is my preference. The only devices I can find that fit on the board have 196 or 256 pins. But the real problem is availability.

Digikey has a few of the XC7S15-1FTGB196I and more a scheduled for delivery in April. Add in the various speed and temperature flavors trickling in (mostly in April) and I should be ok for the initial delivery in August... if I can get my hands on those. I don\'t know if Digikey factors in the backlog orders in these counts.

Mouser shows great inventory of Efinix parts, particularly the T13 and T20 in a 0.8 mm 256 pin BGA, 10s of thousands in stock. But I\'d rather work with a 1.0 mm BGA. Oddly enough, LCSC shows part numbers, but zero inventory.

Anyone work with 0.8 mm BGAs? What PWB feature dimensions did you use? Did this impact the PWB cost?
The 0.8 mm 256-ball T20 isn\'t bad...

https://www.dropbox.com/s/xjqgj2pz9mdhtma/P941_FPGA.jpg?raw=1

I can\'t really see much detail. It looks like there are virtually no pads on the vias under the BGA. What size are they?
The BGAVIAs are 12.5 mil OD with 8 mil drills. The other vias on the
board STANDARDVIA and POWERVIA are bigger.

2.25 mil (0.057 mm) is a pretty narrow via ring. Why not have a larger via pad?
I don\'t know. My PCB guy decides stuff like that. I\'d guess that he
wanted it to pass some design rule check, or maybe he started metric.
The board houses haven\'t complained as far as I know.

You should do your own thing and check with whoever will make your
boards.

Sounds good, but I\'ve never been able to get a board house to even discuss these issues. They always take the approach that they will work with what I give them, which means, if it gives poor results, it\'s my problem.

There are a number of board companies with published capabilities, but they all vary, enough that there seems to be no consensus. Just like your via pad size. I\'ve never seen a board house that says that would be a standard board. I was just looking at one company who wants 10 mil annular ring on inner layers and 7 mil annular ring on surface layers. That\'s a huge difference from 2.25 mil. On the other hand, they will print 2.5 mil trace/space!

I guess that\'s why we make prototypes.

--

Rick C.

---- Get 1,000 miles of free Supercharging
---- Tesla referral code - https://ts.la/richard11209

 

[Richard Damon]

On 1/14/23 7:20 PM, gnuarm.del...@gmail.com wrote:

On Saturday, January 14, 2023 at 3:17:24 PM UTC-4, John Larkin wrote:

You should do your own thing and check with whoever will make your
boards.

Sounds good, but I\'ve never been able to get a board house to even discuss these issues. They always take the approach that they will work with what I give them, which means, if it gives poor results, it\'s my problem.

There are a number of board companies with published capabilities, but they all vary, enough that there seems to be no consensus. Just like your via pad size. I\'ve never seen a board house that says that would be a standard board. I was just looking at one company who wants 10 mil annular ring on inner layers and 7 mil annular ring on surface layers. That\'s a huge difference from 2.25 mil. On the other hand, they will print 2.5 mil trace/space!

I guess that\'s why we make prototypes.

IF you contact a \"Good\" board shop, they should be able to give you
their specification to make the board.

They may have several levels (of cost) with different requirements.


If you board shop is NOT giving you a promise that the boards theya have
built will be \"successful\", then I would not touch them.

Yes, capabilities do vary a lot, so I always like to talk with my CMs
about what shops they use for the sort of class board we are working on,
and check with the shop on their requirements.

We also keep a general idea of capabilities, so if one shop is a bit
better on one spec, we might try not fully using that so other shops are
likely able to handle it.

 

[John Larkin]

On Sat, 14 Jan 2023 16:20:53 -0800 (PST), \"gnuarm.del...@gmail.com\"
<gnuarm.deletethisbit@gmail.com> wrote:

On Saturday, January 14, 2023 at 3:17:24 PM UTC-4, John Larkin wrote:
On Sat, 14 Jan 2023 10:05:33 -0800 (PST), \"gnuarm.del...@gmail.com\"
gnuarm.del...@gmail.com> wrote:

On Saturday, January 14, 2023 at 12:08:03 PM UTC-4, John Larkin wrote:
On Fri, 13 Jan 2023 21:20:50 -0800 (PST), \"gnuarm.del...@gmail.com\"
gnuarm.del...@gmail.com> wrote:

On Saturday, January 14, 2023 at 12:39:49 AM UTC-4, John Larkin wrote:
On Sat, 7 Jan 2023 09:49:24 -0800 (PST), \"gnuarm.del...@gmail.com\"
gnuarm.del...@gmail.com> wrote:

A small board with a 100QFP is being redesigned for a new FPGA due to obsolescence. Gowin makes a 100QFP device that would be a good fit, but my customer has said \"no\" to the 100% Chinese brand... US government customers, ya know!

So now I\'m looking at a BGA. I don\'t want to get into fine PCB design rules, so 1.0 mm ball pitch is my preference. The only devices I can find that fit on the board have 196 or 256 pins. But the real problem is availability.

Digikey has a few of the XC7S15-1FTGB196I and more a scheduled for delivery in April. Add in the various speed and temperature flavors trickling in (mostly in April) and I should be ok for the initial delivery in August... if I can get my hands on those. I don\'t know if Digikey factors in the backlog orders in these counts.

Mouser shows great inventory of Efinix parts, particularly the T13 and T20 in a 0.8 mm 256 pin BGA, 10s of thousands in stock. But I\'d rather work with a 1.0 mm BGA. Oddly enough, LCSC shows part numbers, but zero inventory.

Anyone work with 0.8 mm BGAs? What PWB feature dimensions did you use? Did this impact the PWB cost?
The 0.8 mm 256-ball T20 isn\'t bad...

https://www.dropbox.com/s/xjqgj2pz9mdhtma/P941_FPGA.jpg?raw=1

I can\'t really see much detail. It looks like there are virtually no pads on the vias under the BGA. What size are they?
The BGAVIAs are 12.5 mil OD with 8 mil drills. The other vias on the
board STANDARDVIA and POWERVIA are bigger.

2.25 mil (0.057 mm) is a pretty narrow via ring. Why not have a larger via pad?
I don\'t know. My PCB guy decides stuff like that. I\'d guess that he
wanted it to pass some design rule check, or maybe he started metric.
The board houses haven\'t complained as far as I know.

You should do your own thing and check with whoever will make your
boards.

Sounds good, but I\'ve never been able to get a board house to even discuss these issues. They always take the approach that they will work with what I give them, which means, if it gives poor results, it\'s my problem.

We always specify bare-board testing and warpage and tolerances, so we
don\'t get bad boards. What we can get is expensive boards.

There are a number of board companies with published capabilities, but they all vary, enough that there seems to be no consensus. Just like your via pad size. I\'ve never seen a board house that says that would be a standard board. I was just looking at one company who wants 10 mil annular ring on inner layers and 7 mil annular ring on surface layers. That\'s a huge difference from 2.25 mil. On the other hand, they will print 2.5 mil trace/space!

Zero annular ring seems to be OK on inners. That reduces capacitance.
5 or even 4 mil traces are usually standard price. I don\'t know why my
guy used 6 on the board that I posted.

We do email our board houses and often they answer!

I guess that\'s why we make prototypes.

We don\'t prototype actual products; just go for it.

 

[gnuarm.del...@gmail.com]

On Saturday, January 14, 2023 at 8:39:59 PM UTC-4, Richard Damon wrote:

On 1/14/23 7:20 PM, gnuarm.del...@gmail.com wrote:
On Saturday, January 14, 2023 at 3:17:24 PM UTC-4, John Larkin wrote:

You should do your own thing and check with whoever will make your
boards.

Sounds good, but I\'ve never been able to get a board house to even discuss these issues. They always take the approach that they will work with what I give them, which means, if it gives poor results, it\'s my problem.

There are a number of board companies with published capabilities, but they all vary, enough that there seems to be no consensus. Just like your via pad size. I\'ve never seen a board house that says that would be a standard board. I was just looking at one company who wants 10 mil annular ring on inner layers and 7 mil annular ring on surface layers. That\'s a huge difference from 2.25 mil. On the other hand, they will print 2.5 mil trace/space!

I guess that\'s why we make prototypes.

IF you contact a \"Good\" board shop, they should be able to give you
their specification to make the board.

Ok, which are the \"good\" ones? I assume you mean a place that makes the bare boards. A CM typically buys bare boards and assembles the parts. Like I said, they work with what you give them and will do their best. They expect the designers to do the design work.

They may have several levels (of cost) with different requirements.


If you board shop is NOT giving you a promise that the boards theya have
built will be \"successful\", then I would not touch them.

They don\'t charge for boards that don\'t work, of course. But the parts that get thrown out are mine. I was a bit surprised to find out they actually expect to see 20% fall out because of parts not properly picked up. They get pulled off the tape, but if they are not aligned well enough, they get flung into space. One of the parts on my previous build had a $200 part on it. We lost some 40 or so, I don\'t recall the exact number. They recovered a few of them from various nooks and crannies. I\'ve always been told about losses, but I thought that was mostly the tiny passives that don\'t matter. This was a pretty small, TSSOP-20.

Yes, capabilities do vary a lot, so I always like to talk with my CMs
about what shops they use for the sort of class board we are working on,
and check with the shop on their requirements.

We also keep a general idea of capabilities, so if one shop is a bit
better on one spec, we might try not fully using that so other shops are
likely able to handle it.

I got the \"Award Letter\" the other day and with the onerous conditions, I may not be able to accept the order. Two years ago, we went through this via a third party CM who did their integration. It took months to resolve the issues. They want prototypes in May. Ain\'t gonna happen.

They want me to guarantee all manner of things that I can\'t guarantee, such as being able to manufacture the boards for 10 years. They want indemnifications for all manner of things. They even claim ownership of any \"unpatented knowledge or information\" that is disclosed to them is considered to be \"part of the consideration for this Agreement\". I believe this is what is called \"trade secrets\".

This is far more onerous than what had been negotiated previously though their CM. Now, I have to start all over again.

--

Rick C.

---+ Get 1,000 miles of free Supercharging
---+ Tesla referral code - https://ts.la/richard11209

 

[gnuarm.del...@gmail.com]

On Saturday, January 14, 2023 at 9:34:09 PM UTC-4, John Larkin wrote:

On Sat, 14 Jan 2023 16:20:53 -0800 (PST), \"gnuarm.del...@gmail.com\"
gnuarm.del...@gmail.com> wrote:

On Saturday, January 14, 2023 at 3:17:24 PM UTC-4, John Larkin wrote:
On Sat, 14 Jan 2023 10:05:33 -0800 (PST), \"gnuarm.del...@gmail.com\"
gnuarm.del...@gmail.com> wrote:

On Saturday, January 14, 2023 at 12:08:03 PM UTC-4, John Larkin wrote:
On Fri, 13 Jan 2023 21:20:50 -0800 (PST), \"gnuarm.del...@gmail.com\"
gnuarm.del...@gmail.com> wrote:

On Saturday, January 14, 2023 at 12:39:49 AM UTC-4, John Larkin wrote:
On Sat, 7 Jan 2023 09:49:24 -0800 (PST), \"gnuarm.del...@gmail.com\"
gnuarm.del...@gmail.com> wrote:

A small board with a 100QFP is being redesigned for a new FPGA due to obsolescence. Gowin makes a 100QFP device that would be a good fit, but my customer has said \"no\" to the 100% Chinese brand... US government customers, ya know!

So now I\'m looking at a BGA. I don\'t want to get into fine PCB design rules, so 1.0 mm ball pitch is my preference. The only devices I can find that fit on the board have 196 or 256 pins. But the real problem is availability.

Digikey has a few of the XC7S15-1FTGB196I and more a scheduled for delivery in April. Add in the various speed and temperature flavors trickling in (mostly in April) and I should be ok for the initial delivery in August... if I can get my hands on those. I don\'t know if Digikey factors in the backlog orders in these counts.

Mouser shows great inventory of Efinix parts, particularly the T13 and T20 in a 0.8 mm 256 pin BGA, 10s of thousands in stock. But I\'d rather work with a 1.0 mm BGA. Oddly enough, LCSC shows part numbers, but zero inventory.

Anyone work with 0.8 mm BGAs? What PWB feature dimensions did you use? Did this impact the PWB cost?
The 0.8 mm 256-ball T20 isn\'t bad...

https://www.dropbox.com/s/xjqgj2pz9mdhtma/P941_FPGA.jpg?raw=1

I can\'t really see much detail. It looks like there are virtually no pads on the vias under the BGA. What size are they?
The BGAVIAs are 12.5 mil OD with 8 mil drills. The other vias on the
board STANDARDVIA and POWERVIA are bigger.

2.25 mil (0.057 mm) is a pretty narrow via ring. Why not have a larger via pad?
I don\'t know. My PCB guy decides stuff like that. I\'d guess that he
wanted it to pass some design rule check, or maybe he started metric.
The board houses haven\'t complained as far as I know.

You should do your own thing and check with whoever will make your
boards.

Sounds good, but I\'ve never been able to get a board house to even discuss these issues. They always take the approach that they will work with what I give them, which means, if it gives poor results, it\'s my problem.
We always specify bare-board testing and warpage and tolerances, so we
don\'t get bad boards. What we can get is expensive boards.

There are a number of board companies with published capabilities, but they all vary, enough that there seems to be no consensus. Just like your via pad size. I\'ve never seen a board house that says that would be a standard board. I was just looking at one company who wants 10 mil annular ring on inner layers and 7 mil annular ring on surface layers. That\'s a huge difference from 2.25 mil. On the other hand, they will print 2.5 mil trace/space!
Zero annular ring seems to be OK on inners. That reduces capacitance.
5 or even 4 mil traces are usually standard price. I don\'t know why my
guy used 6 on the board that I posted.

We do email our board houses and often they answer!

You aren\'t paying attention. I don\'t use a PWB fabricator, I use a Contract Assembly house to assemble my boards. They are a middle man between me and the PWB fabricator. Once, no twice I\'ve had to get on the phone with the actual PWB fabricator to convince him that he should not clip my silk screen. The use such a large clip radius that they made half the refdes illegible. That really makes the board hard to debug.

I guess that\'s why we make prototypes.
We don\'t prototype actual products; just go for it.

I don\'t have a choice, the customer wants 16 early protos, then 146 protos, then 100 pieces for pilot and 1100 FRS. So there is no \"go for it\". I\'m sure I\'ll munge something up. Replacing the two main parts on the board and moving the connectors to the other side, means it\'s a complete redesign, at least for the artwork, if not the schematic.

--

Rick C.

--+- Get 1,000 miles of free Supercharging
--+- Tesla referral code - https://ts.la/richard11209

 

[Richard Damon]

On 1/14/23 8:44 PM, gnuarm.del...@gmail.com wrote:

On Saturday, January 14, 2023 at 8:39:59 PM UTC-4, Richard Damon wrote:
On 1/14/23 7:20 PM, gnuarm.del...@gmail.com wrote:
On Saturday, January 14, 2023 at 3:17:24 PM UTC-4, John Larkin wrote:

You should do your own thing and check with whoever will make your
boards.

Sounds good, but I\'ve never been able to get a board house to even discuss these issues. They always take the approach that they will work with what I give them, which means, if it gives poor results, it\'s my problem.

There are a number of board companies with published capabilities, but they all vary, enough that there seems to be no consensus. Just like your via pad size. I\'ve never seen a board house that says that would be a standard board. I was just looking at one company who wants 10 mil annular ring on inner layers and 7 mil annular ring on surface layers. That\'s a huge difference from 2.25 mil. On the other hand, they will print 2.5 mil trace/space!

I guess that\'s why we make prototypes.

IF you contact a \"Good\" board shop, they should be able to give you
their specification to make the board.

Ok, which are the \"good\" ones? I assume you mean a place that makes the bare boards. A CM typically buys bare boards and assembles the parts. Like I said, they work with what you give them and will do their best. They expect the designers to do the design work.

There are a number of them, As I said, If you are using a CM, you will
need to talk with them and find who they use and talk to them about
their requirements.

They may have several levels (of cost) with different requirements.


If you board shop is NOT giving you a promise that the boards theya have
built will be \"successful\", then I would not touch them.

They don\'t charge for boards that don\'t work, of course. But the parts that get thrown out are mine. I was a bit surprised to find out they actually expect to see 20% fall out because of parts not properly picked up. They get pulled off the tape, but if they are not aligned well enough, they get flung into space. One of the parts on my previous build had a $200 part on it. We lost some 40 or so, I don\'t recall the exact number. They recovered a few of them from various nooks and crannies. I\'ve always been told about losses, but I thought that was mostly the tiny passives that don\'t matter. This was a pretty small, TSSOP-20.

So, you aren\'t using a good CM, as they aren\'t using a good board shop,
or at least didn\'t give you their expected failure rates up front. Yes,
there are loss factors for parts, but if they didn\'t give you those when
you started to negotiate the contract when you indicated you will be
supplying some of the parts, they aren\'t doing their job.

Yes, it may be \"cheaper\" to use a shop like that, but you pay for it in
those sorts of costs.

Yes, capabilities do vary a lot, so I always like to talk with my CMs
about what shops they use for the sort of class board we are working on,
and check with the shop on their requirements.

We also keep a general idea of capabilities, so if one shop is a bit
better on one spec, we might try not fully using that so other shops are
likely able to handle it.

I got the \"Award Letter\" the other day and with the onerous conditions, I may not be able to accept the order. Two years ago, we went through this via a third party CM who did their integration. It took months to resolve the issues. They want prototypes in May. Ain\'t gonna happen.

They want me to guarantee all manner of things that I can\'t guarantee, such as being able to manufacture the boards for 10 years. They want indemnifications for all manner of things. They even claim ownership of any \"unpatented knowledge or information\" that is disclosed to them is considered to be \"part of the consideration for this Agreement\". I believe this is what is called \"trade secrets\".

This is far more onerous than what had been negotiated previously though their CM. Now, I have to start all over again.

Yes, some \"customers\" are not worth it.

 

[John Larkin]

On Sat, 14 Jan 2023 17:52:45 -0800 (PST), \"gnuarm.del...@gmail.com\"
<gnuarm.deletethisbit@gmail.com> wrote:

On Saturday, January 14, 2023 at 9:34:09 PM UTC-4, John Larkin wrote:
On Sat, 14 Jan 2023 16:20:53 -0800 (PST), \"gnuarm.del...@gmail.com\"
gnuarm.del...@gmail.com> wrote:

On Saturday, January 14, 2023 at 3:17:24 PM UTC-4, John Larkin wrote:
On Sat, 14 Jan 2023 10:05:33 -0800 (PST), \"gnuarm.del...@gmail.com\"
gnuarm.del...@gmail.com> wrote:

On Saturday, January 14, 2023 at 12:08:03 PM UTC-4, John Larkin wrote:
On Fri, 13 Jan 2023 21:20:50 -0800 (PST), \"gnuarm.del...@gmail.com\"
gnuarm.del...@gmail.com> wrote:

On Saturday, January 14, 2023 at 12:39:49 AM UTC-4, John Larkin wrote:
On Sat, 7 Jan 2023 09:49:24 -0800 (PST), \"gnuarm.del...@gmail.com\"
gnuarm.del...@gmail.com> wrote:

A small board with a 100QFP is being redesigned for a new FPGA due to obsolescence. Gowin makes a 100QFP device that would be a good fit, but my customer has said \"no\" to the 100% Chinese brand... US government customers, ya know!

So now I\'m looking at a BGA. I don\'t want to get into fine PCB design rules, so 1.0 mm ball pitch is my preference. The only devices I can find that fit on the board have 196 or 256 pins. But the real problem is availability.

Digikey has a few of the XC7S15-1FTGB196I and more a scheduled for delivery in April. Add in the various speed and temperature flavors trickling in (mostly in April) and I should be ok for the initial delivery in August... if I can get my hands on those. I don\'t know if Digikey factors in the backlog orders in these counts.

Mouser shows great inventory of Efinix parts, particularly the T13 and T20 in a 0.8 mm 256 pin BGA, 10s of thousands in stock. But I\'d rather work with a 1.0 mm BGA. Oddly enough, LCSC shows part numbers, but zero inventory.

Anyone work with 0.8 mm BGAs? What PWB feature dimensions did you use? Did this impact the PWB cost?
The 0.8 mm 256-ball T20 isn\'t bad...

https://www.dropbox.com/s/xjqgj2pz9mdhtma/P941_FPGA.jpg?raw=1

I can\'t really see much detail. It looks like there are virtually no pads on the vias under the BGA. What size are they?
The BGAVIAs are 12.5 mil OD with 8 mil drills. The other vias on the
board STANDARDVIA and POWERVIA are bigger.

2.25 mil (0.057 mm) is a pretty narrow via ring. Why not have a larger via pad?
I don\'t know. My PCB guy decides stuff like that. I\'d guess that he
wanted it to pass some design rule check, or maybe he started metric.
The board houses haven\'t complained as far as I know.

You should do your own thing and check with whoever will make your
boards.

Sounds good, but I\'ve never been able to get a board house to even discuss these issues. They always take the approach that they will work with what I give them, which means, if it gives poor results, it\'s my problem.
We always specify bare-board testing and warpage and tolerances, so we
don\'t get bad boards. What we can get is expensive boards.

There are a number of board companies with published capabilities, but they all vary, enough that there seems to be no consensus. Just like your via pad size. I\'ve never seen a board house that says that would be a standard board. I was just looking at one company who wants 10 mil annular ring on inner layers and 7 mil annular ring on surface layers. That\'s a huge difference from 2.25 mil. On the other hand, they will print 2.5 mil trace/space!
Zero annular ring seems to be OK on inners. That reduces capacitance.
5 or even 4 mil traces are usually standard price. I don\'t know why my
guy used 6 on the board that I posted.

We do email our board houses and often they answer!

You aren\'t paying attention.

That\'s because you\'re obnoxious.

 

[gnuarm.del...@gmail.com]

On Sunday, January 15, 2023 at 12:10:54 AM UTC-4, John Larkin wrote:

On Sat, 14 Jan 2023 17:52:45 -0800 (PST), \"gnuarm.del...@gmail.com\"
gnuarm.del...@gmail.com> wrote:

On Saturday, January 14, 2023 at 9:34:09 PM UTC-4, John Larkin wrote:
On Sat, 14 Jan 2023 16:20:53 -0800 (PST), \"gnuarm.del...@gmail.com\"
gnuarm.del...@gmail.com> wrote:

On Saturday, January 14, 2023 at 3:17:24 PM UTC-4, John Larkin wrote:
On Sat, 14 Jan 2023 10:05:33 -0800 (PST), \"gnuarm.del...@gmail.com\"
gnuarm.del...@gmail.com> wrote:

On Saturday, January 14, 2023 at 12:08:03 PM UTC-4, John Larkin wrote:
On Fri, 13 Jan 2023 21:20:50 -0800 (PST), \"gnuarm.del...@gmail.com\"
gnuarm.del...@gmail.com> wrote:

On Saturday, January 14, 2023 at 12:39:49 AM UTC-4, John Larkin wrote:
On Sat, 7 Jan 2023 09:49:24 -0800 (PST), \"gnuarm.del...@gmail..com\"
gnuarm.del...@gmail.com> wrote:

A small board with a 100QFP is being redesigned for a new FPGA due to obsolescence. Gowin makes a 100QFP device that would be a good fit, but my customer has said \"no\" to the 100% Chinese brand... US government customers, ya know!

So now I\'m looking at a BGA. I don\'t want to get into fine PCB design rules, so 1.0 mm ball pitch is my preference. The only devices I can find that fit on the board have 196 or 256 pins. But the real problem is availability.

Digikey has a few of the XC7S15-1FTGB196I and more a scheduled for delivery in April. Add in the various speed and temperature flavors trickling in (mostly in April) and I should be ok for the initial delivery in August... if I can get my hands on those. I don\'t know if Digikey factors in the backlog orders in these counts.

Mouser shows great inventory of Efinix parts, particularly the T13 and T20 in a 0.8 mm 256 pin BGA, 10s of thousands in stock. But I\'d rather work with a 1.0 mm BGA. Oddly enough, LCSC shows part numbers, but zero inventory.

Anyone work with 0.8 mm BGAs? What PWB feature dimensions did you use? Did this impact the PWB cost?
The 0.8 mm 256-ball T20 isn\'t bad...

https://www.dropbox.com/s/xjqgj2pz9mdhtma/P941_FPGA.jpg?raw=1

I can\'t really see much detail. It looks like there are virtually no pads on the vias under the BGA. What size are they?
The BGAVIAs are 12.5 mil OD with 8 mil drills. The other vias on the
board STANDARDVIA and POWERVIA are bigger.

2.25 mil (0.057 mm) is a pretty narrow via ring. Why not have a larger via pad?
I don\'t know. My PCB guy decides stuff like that. I\'d guess that he
wanted it to pass some design rule check, or maybe he started metric.
The board houses haven\'t complained as far as I know.

You should do your own thing and check with whoever will make your
boards.

Sounds good, but I\'ve never been able to get a board house to even discuss these issues. They always take the approach that they will work with what I give them, which means, if it gives poor results, it\'s my problem.
We always specify bare-board testing and warpage and tolerances, so we
don\'t get bad boards. What we can get is expensive boards.

There are a number of board companies with published capabilities, but they all vary, enough that there seems to be no consensus. Just like your via pad size. I\'ve never seen a board house that says that would be a standard board. I was just looking at one company who wants 10 mil annular ring on inner layers and 7 mil annular ring on surface layers. That\'s a huge difference from 2.25 mil. On the other hand, they will print 2.5 mil trace/space!
Zero annular ring seems to be OK on inners. That reduces capacitance.
5 or even 4 mil traces are usually standard price. I don\'t know why my
guy used 6 on the board that I posted.

We do email our board houses and often they answer!

You aren\'t paying attention.
That\'s because you\'re obnoxious.

Wow! Talk about sensitive. What is going on with you???

--

Rick C.

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