GaN With the Wind...

On Sunday, June 21, 2020 at 9:58:56 PM UTC-4, dagmarg...@yahoo.com wrote:
I don\'t have a microscope & haven\'t needed one. I just did it
caveman-style. (Are we still allowed to say \'caveman\'?)

I don\'t think so:

<https://en.wikipedia.org/wiki/GEICO_Cavemen>

<https://en.wikipedia.org/wiki/Cavemen_(TV_series)>
 
On Monday, June 22, 2020 at 5:51:14 PM UTC+2, jla...@highlandsniptechnology.com wrote:
On Mon, 22 Jun 2020 10:12:30 +0200, Gerhard Hoffmann <dk4xp@arcor.de
wrote:

Am 22.06.20 um 01:32 schrieb dagmargoodboat@yahoo.com:
As I design yet another little switcher, I notice it\'s getting
more and more tempting to swap ye olde MOS FET for a shiny
new GaN-speck.

Electrically superior in almost every respect, the GaN FETs\'
drawbacks are thermal (not a problem in this case), and their
tee-nine-sie .9x.9mm bare-chip packages.

e.g.
T.I. CSD19831Q3: 100V, Rds(on)=50mohm, Cin=350pF, Coss=70pF, Crss=13pF
EPC EPC2036: 100V, Rds(on)~=60mohm, Cin=43pF, Coss=25pF, Crss<1pF

I re-worked a chip-scale part with hot air and a hot plate by hand.
Took me a zillion tries to get it done--that was a nuisance.


I was more lucky. My first 2 tries worked immediately with just a
little bit of hot air. Very little, or they fly away.
That was a test structure from a corner of a larger board made
by PCBWAY. HAL, I removed the excess tin with some unsolder braid
and used paste then.
PCBWAY spotted the mask on the pad as designed by EPC\'s Altium example.
Worked after declaring it OK.



https://www.flickr.com/photos/137684711@N07/50032925082/in/dateposted-public/

between the 4 1210 caps and the 2 fat vias.


cheers, Gerhard

I wasn\'t happy with my PCBWAY board. Resolution and registration were
bad, and they didn\'t read my stackup specs. Their default 4-layer
stack has *four mils* of dielectric between layers 1 and 2, and
between 3 and 4. That is really nasty. That stack is common in cheap
chinese proto houses.

https://www.dropbox.com/s/p3vpbaofzqurebz/Z462_PCB_Way_2.png?raw=1

https://www.dropbox.com/s/v6isv7k1t3fre0w/PCBWAY_Mask.jpg?raw=1

That would be OK for slow, not very demanding stuff.

Our max frequencies are normally 2-300 MHz from fast edges in inverter drives, so from that point, that is really not so bad, I guess, if we were to use such a stackup

We also do some BLE, that gets trickier

Cheers

Klaus
 
I\'ve got the fabricated board on Friday. :-(
Fabricated here in .de. 10 minutes of drive between my
customer and the board house.

All I wanted was 0.635mm of Rogers TMM6 between Layer1 and 2
because on layer 1 there live the coplanar waveguides.

Rest of the stack was don\'t care: 2, 3 are gnd, 4 is just
the lowpass of the synthesizer PLL. The rest could be FR4
of because TMM6 is mechanically stable like candle wax.

They succeeded to put the Rogers layer between layer 3 & 4
which carries just some AF.

AAARGHHHH!


I have cracked the first sample of the 10 GHz puck oscillator
board which is only 0.65mm TMM6 when I fastened the first SMA
connector. OK, my fault. TMM6 is like wax.

I have TDRed the longish coplanar WG output line of the 2nd sample.
No difference to the internal 50 Ohm line of the Agilent
54754A. ADS line calc seems to work as promised.
Just the SMA laucher needs a smaller footprint and less tin.
Dips down to 40 Ohms over some mm.

Gerhard



Am 22.06.20 um 20:26 schrieb Gerhard Hoffmann:
Am 22.06.20 um 19:34 schrieb Jeroen Belleman:
On 2020-06-22 17:51, jlarkin@highlandsniptechnology.com wrote:
[...]
I wasn\'t happy with my PCBWAY board. Resolution and registration were
bad, and they didn\'t read my stackup specs. Their default 4-layer
stack has *four mils* of dielectric between layers 1 and 2, and
between 3 and 4. That is really nasty. That stack is common in cheap
chinese proto houses.

That\'s nasty indeed. Who\'d use a stackup like that?

Jeroen Belleman

Someone who wants narrow microstrips on the top level?

In fact, I\'m just asking a local board maker for sth. similar,
with the middle of the stack made from thick FR4 for stability
and on the outside thin Rogers 4003 or whatever for thin micro-
strips and low radiation loss at 10 GHz.

It looks like the eval board of the ADF5356 has a similar stack,
just from visually inspecting the milled sides.

Up to now I had no single problem with PCBWAY other than that they
use DHL express which leads to some fee f*cking here in .de and
constant trouble with the customs in Leipzig.
I did not let them make multilayers up to now.

I made a test run with JLCPCB, they have now a proxy man here
in .de. That adds theoretically 2 days or so, but the proxy
handles the customs which may result in an speedup over all.
The proxy gets a pack with the daily production for the EU and
relays it per local mail with a new tracking number.

It is now technically an inland buy, they collect the local VAT
in advance. Works nicely.

Gerhard
 
On Mon, 10 Aug 2020 00:28:49 +0200, Gerhard Hoffmann <dk4xp@arcor.de>
wrote:

I\'ve got the fabricated board on Friday. :-(
Fabricated here in .de. 10 minutes of drive between my
customer and the board house.

All I wanted was 0.635mm of Rogers TMM6 between Layer1 and 2
because on layer 1 there live the coplanar waveguides.

Rest of the stack was don\'t care: 2, 3 are gnd, 4 is just
the lowpass of the synthesizer PLL. The rest could be FR4
of because TMM6 is mechanically stable like candle wax.

They succeeded to put the Rogers layer between layer 3 & 4
which carries just some AF.

AAARGHHHH!


I have cracked the first sample of the 10 GHz puck oscillator
board which is only 0.65mm TMM6 when I fastened the first SMA
connector. OK, my fault. TMM6 is like wax.

I have TDRed the longish coplanar WG output line of the 2nd sample.
No difference to the internal 50 Ohm line of the Agilent
54754A. ADS line calc seems to work as promised.
Just the SMA laucher needs a smaller footprint and less tin.
Dips down to 40 Ohms over some mm.

Gerhard



Am 22.06.20 um 20:26 schrieb Gerhard Hoffmann:
Am 22.06.20 um 19:34 schrieb Jeroen Belleman:
On 2020-06-22 17:51, jlarkin@highlandsniptechnology.com wrote:
[...]
I wasn\'t happy with my PCBWAY board. Resolution and registration were
bad, and they didn\'t read my stackup specs. Their default 4-layer
stack has *four mils* of dielectric between layers 1 and 2, and
between 3 and 4. That is really nasty. That stack is common in cheap
chinese proto houses.

That\'s nasty indeed. Who\'d use a stackup like that?

Jeroen Belleman

Someone who wants narrow microstrips on the top level?

In fact, I\'m just asking a local board maker for sth. similar,
with the middle of the stack made from thick FR4 for stability
and on the outside thin Rogers 4003 or whatever for thin micro-
strips and low radiation loss at 10 GHz.

It looks like the eval board of the ADF5356 has a similar stack,
just from visually inspecting the milled sides.

Up to now I had no single problem with PCBWAY other than that they
use DHL express which leads to some fee f*cking here in .de and
constant trouble with the customs in Leipzig.
I did not let them make multilayers up to now.

I made a test run with JLCPCB, they have now a proxy man here
in .de. That adds theoretically 2 days or so, but the proxy
handles the customs which may result in an speedup over all.
The proxy gets a pack with the daily production for the EU and
relays it per local mail with a new tracking number.

It is now technically an inland buy, they collect the local VAT
in advance. Works nicely.

Gerhard

I made some boards with microwave lam in just the top layer. They came
curled up like potato chips.

https://www.dropbox.com/s/yibz36f0ex7z1sp/MOV02429.MPG?dl=0
 

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