Soldering surface mount components

"Terry Given" <my_name_at_ieee.org> wrote in message
news:CMOsd.22681$9A.389016_at_news.xtra.co.nz...

Larry Brasfield wrote:

...

What do you think happens when you thump a capacitor
that is not biased? If it was piezoelectric, (and read Terry's
quoted definition carefully), it would produce an electrical
signal. But it does not.

I'm gonna get a steak and cheese pie, then whack up a little test circuit - inverting amp, cap from -ve i/p to 0V, 100k feedback
and bias comp resistors, +/-5V supplies, and do a few tests. I have some nice 10uF X7R caps, and some 1nF NPOs. I think I have a
few Y5Vs too...

anything wrong with this setup? other than the fact I amp applying a VERY small bias to the cap, around the offset voltage of the
opamp - in this case about 4mV. How can I reduce this further?


Why not use a bigger capacitor to AC couple the
capacitor under test? Then you could use a large
resistor to enforce (nearly) 0 VDC bias.

I question what your setup can show. New ceramic caps
are very unlikely to exhibit a piezoelectric effect. But high
K caps that have been biased may be slightly poled and
respond to a "thump". Please see my response to Mr.
Smith where I had to back off my initial position a tad.

Larry Brasfield wrote:

"Terry Given" <my_name_at_ieee.org> wrote in message
news:CMOsd.22681$9A.389016_at_news.xtra.co.nz...

Larry Brasfield wrote:

...

What do you think happens when you thump a capacitor
that is not biased? If it was piezoelectric, (and read Terry's
quoted definition carefully), it would produce an electrical
signal. But it does not.

I'm gonna get a steak and cheese pie, then whack up a little test circuit - inverting amp,
cap from -ve i/p to 0V, 100k feedback and bias comp resistors, +/-5V supplies, and
do a few tests. I have some nice 10uF X7R caps, and some 1nF NPOs. I think I have
a few Y5Vs too...

anything wrong with this setup? other than the fact I amp applying a VERY small bias to the cap, around the offset voltage of the
opamp - in this case about 4mV. How can I reduce this further?

Why not use a bigger capacitor to AC couple the
capacitor under test? Then you could use a large
resistor to enforce (nearly) 0 VDC bias.

If I have 2 caps, how do I tell which caused the signal?

I question what your setup can show. New ceramic caps
are very unlikely to exhibit a piezoelectric effect. But high
K caps that have been biased may be slightly poled and
respond to a "thump". Please see my response to Mr.
Smith where I had to back off my initial position a tad.

I question my setup too. The X7Rs I have have all been biased to 50% rated voltage for weeks. The pie was very nice, but I got
sidetracked. Bac to the soldering iron...

Cheers
Terry

Larry Brasfield wrote:
....
Your poor microphone, at some time during its life, transitioned
from being a mere capacitor into a piezoelectric device. This
most likely occured when it was held under bias for a long
period of time. (It could occur in a short time at a temperature
higher than most electronics see.) It became poled, probably
not very well since it was inadvertant. You may have seen or
heard of dielectric absorption. High K capacitors are also
subject to it, and until their internal and only slowly available
charge is gone, they will be slightly piezoelectric, as your poor
microphone undoubtedly was.

I'm a bit out of my depth here (but still floating), but this sounds very similar to the ageing effect discussed by TDK in this
paper:

http://www.component.tdk.com/components/whatisthecapofthiscap.pdf

"over time the internal molecular structure changes in such a way as to create an alignment of electrical dipoles. This alignment
results in a structure that can hold less electrical charge than when the molecules are in a totally random state, such as at the
time of heating or mounting on a printed circuit board"

and

"heating the capacitor above its curie temperature causes the crystalline structure to return to its optimal unaligned
configuration, resulting in maximum capacitance. TDK recommends 150C/1 hour for de-aging" which alas is far too long to assert
that soldering actually REDUCES the piezoelectric effect - just as well really, considering this thread.

I had a quick squiz thru "surface wave filters", Mathews, John Wiley & Sons, but no real info on the piezoelectric materials
themselves. I probably have the info kicking around (50 years of UFFC publications on 20 CDROMs) but digging it out looks time
consuming.

It sounds like some sort of "forming" process is required for piezoelectric devices - is that what you are referring to when you
say "poled" Larry? Care to describe the process a bit please?

You may also have heard biased capacitors, when subject to
AC currents having components in the audio range, make a
sound. In all likelyhood, that sound is not due to piezoelectric
effect. (A very small fraction of it could be, but not enough
to reach audibility.) It is due to simple compression of the
dielectric, by opposing charges, which varies in degree as
the AC occurs.

I would reason that electrolytics would be worse in this regard, as the dielectric is not a solid.

"Terry Given" <my_name_at_ieee.org> wrote in message news:NrSsd.22767$9A.390821_at_news.xtra.co.nz...

Larry Brasfield wrote:


"Terry Given" <my_name_at_ieee.org> wrote in message
news:CMOsd.22681$9A.389016_at_news.xtra.co.nz...


Larry Brasfield wrote:

...


What do you think happens when you thump a capacitor
that is not biased? If it was piezoelectric, (and read Terry's
quoted definition carefully), it would produce an electrical
signal. But it does not.

I'm gonna get a steak and cheese pie, then whack up a little test circuit - inverting amp,
cap from -ve i/p to 0V, 100k feedback and bias comp resistors, +/-5V supplies, and
do a few tests. I have some nice 10uF X7R caps, and some 1nF NPOs. I think I have
a few Y5Vs too...

anything wrong with this setup? other than the fact I amp applying a VERY small bias to the cap, around the offset voltage of the
opamp - in this case about 4mV. How can I reduce this further?

Why not use a bigger capacitor to AC couple the
capacitor under test? Then you could use a large
resistor to enforce (nearly) 0 VDC bias.

If I have 2 caps, how do I tell which caused the signal?


Thump just one? Acousticly isolate the one with 4 mV
on it, and use a modern low Eios opamp. Maybe thump
both caps to bound the confounding factor.

I question what your setup can show. New ceramic caps
are very unlikely to exhibit a piezoelectric effect. But high
K caps that have been biased may be slightly poled and
respond to a "thump". Please see my response to Mr.
Smith where I had to back off my initial position a tad.

I question my setup too. The X7Rs I have have all been biased to 50% rated voltage for weeks. The pie was very nice, but I got
sidetracked. Bac to the soldering iron...


Are you attempting to see how good a microphone an
unbiased capacitor can be? That would require some
selection of capacitors with various histories. Are you
attempting to show that not all ceramic capacitors are
piezoelectric? That would require new parts, maybe
even a few that were baked above the Currie point.

Regards,

That would require new parts, maybe even a few that
were baked above the Currie point.

I think the problem with mechanics is that it initially is more
accessible than electronics. By that I mean it is easy to get a handle
on say torque - lean on a bar, whereas getting a handle on an electron
is a bit trickier - you cant see it, feel it etc. most of the
electronics people I meet have a fair understanding of second order
systems, stuff like that. but few so-called mechanical engineers do. I
have been fortunate enough to work with some brilliant mechanical
engineers, people who are every bit as clever and creative as the
smartest electronics guys I know (some guys I very briefly worked with
at Penn State were incredible), but most seem a bit thick. Hell, try
getting a sheet metal shop to fold up a box accurately.

Then when you really get into it, mechanics is a lot more complex than
(most) electronics - nothing is isotropic, or homogeneous, or perhaps
even well characterised. Everything is as non-linear as all hell, and
the measurements are a lot harder. I suspect all the clever mech
engineers go work on the really tricky stuff, and leave the rest of the
work to the metal-shop dropouts.

"Ken Smith" <kensmith_at_green.rahul.net> wrote in message
[...]
Ok, I am going to have to take a more nuanced position here.

You and I were addressing two different phenomena.

My issue is with incorrectly calling any instance of mechanical
transduction in a capacitor "piezoelectric". As my point about
vacuum should make clear, that usage is sloppy and at odds
with the accepted definition. (Of course, with enough usage,
sloppier definitions become accepted. Such is language.)

I might squirm out here by insisting that your capacitor was in fact
biased, even if you could not measure DCV at its terminals. That
would be a fair description of the condition of a poled PZT, (from
which your capacitor was likely made). But that would not be an
out, because my original position, "[C]ommon ceramic capacitors
are not actually piezoelectric.", is not quite right, as your experience
shows. So I will grant your point without negating the essential
truth of what I was stating.

Your poor microphone, at some time during its life, transitioned
from being a mere capacitor into a piezoelectric device. This
most likely occured when it was held under bias for a long
period of time.

You may also have heard biased capacitors, when subject to
AC currents having components in the audio range, make a
sound. In all likelyhood, that sound is not due to piezoelectric
effect. (A very small fraction of it could be, but not enough
to reach audibility.) It is due to simple compression of the
dielectric, by opposing charges, which varies in degree as
the AC occurs.

How about now?

How about not sufficiently nuanced?

You may also have heard biased capacitors, when subject to
AC currents having components in the audio range, make a
sound. In all likelyhood, that sound is not due to piezoelectric
effect. (A very small fraction of it could be, but not enough
to reach audibility.) It is due to simple compression of the
dielectric, by opposing charges, which varies in degree as
the AC occurs.

I would reason that electrolytics would be worse in this regard, as the
dielectric is not a solid.

On Mon, 06 Dec 2004 17:05:55 +1300, Terry Given <my_name_at_ieee.org
wrote:



I think the problem with mechanics is that it initially is more
accessible than electronics. By that I mean it is easy to get a handle
on say torque - lean on a bar, whereas getting a handle on an electron
is a bit trickier - you cant see it, feel it etc. most of the
electronics people I meet have a fair understanding of second order
systems, stuff like that. but few so-called mechanical engineers do. I
have been fortunate enough to work with some brilliant mechanical
engineers, people who are every bit as clever and creative as the
smartest electronics guys I know (some guys I very briefly worked with
at Penn State were incredible), but most seem a bit thick. Hell, try
getting a sheet metal shop to fold up a box accurately.

Then when you really get into it, mechanics is a lot more complex than
(most) electronics - nothing is isotropic, or homogeneous, or perhaps
even well characterised. Everything is as non-linear as all hell, and
the measurements are a lot harder. I suspect all the clever mech
engineers go work on the really tricky stuff, and leave the rest of the
work to the metal-shop dropouts.



When I was in engineering school, everyone took pretty much
the same core curriculum for the first 2 years. Then you got
to select whether you were going to be an EE, ME, or IE
(Industrial Engineer). The administration tried to steer you
into one of these based on your grade average: EE if you got
good grades, ME if mediocre, else IE. (With my average, I
had to *fight* for an EE slot!)

Best regards,




Bob Masta
dqatechATdaqartaDOTcom

D A Q A R T A
Data AcQuisition And Real-Time Analysis
www.daqarta.com

On Mon, 06 Dec 2004 17:05:55 +1300, Terry Given <my_name_at_ieee.org
wrote:


I think the problem with mechanics is that it initially is more
accessible than electronics. By that I mean it is easy to get a handle
on say torque - lean on a bar, whereas getting a handle on an electron
is a bit trickier - you cant see it, feel it etc. most of the
electronics people I meet have a fair understanding of second order
systems, stuff like that. but few so-called mechanical engineers do. I
have been fortunate enough to work with some brilliant mechanical
engineers, people who are every bit as clever and creative as the
smartest electronics guys I know (some guys I very briefly worked with
at Penn State were incredible), but most seem a bit thick. Hell, try
getting a sheet metal shop to fold up a box accurately.

Then when you really get into it, mechanics is a lot more complex than
(most) electronics - nothing is isotropic, or homogeneous, or perhaps
even well characterised. Everything is as non-linear as all hell, and
the measurements are a lot harder. I suspect all the clever mech
engineers go work on the really tricky stuff, and leave the rest of the
work to the metal-shop dropouts.


When I was in engineering school, everyone took pretty much
the same core curriculum for the first 2 years. Then you got
to select whether you were going to be an EE, ME, or IE
(Industrial Engineer). The administration tried to steer you
into one of these based on your grade average: EE if you got
good grades, ME if mediocre, else IE. (With my average, I
had to *fight* for an EE slot!)

2 further items to assist a good light source and a magnifierliquid flux
helps too

In message <jmfAd.86$By2.50_at_newsfe6-win.ntli.net>, Steven McGahey
steve.shirt.mcgahey_at_virgin.shorts.net> writes

On 27-Dec-2004, "Steven McGahey" <steve.shirt.mcgahey_at_virgin.shorts.net
(remove two items of clothing)> wrote:

Plus, I can't imagine using a soldering iron with such small
components and gaps.

I meant "desoldering iron", not "soldering iron".

- Steve.

On Tue, 28 Dec 2004 17:00:46 +0000, dd wrote:

2 further items to assist a good light source and a magnifierliquid flux
helps too

I once actually found a use for liquid rosin - I used it to make my
hands sticky so I could get a grip on some cable-bundling tape in a
piece of equipment that was all covered with hydraulic fluid.

All I've ever been able to accomplish with it in electronics is gum
up the board and make it harder to clean.

But I do recommend a good magnifier, and a good source of light.

Good Luck!
Rich


In message <jmfAd.86$By2.50_at_newsfe6-win.ntli.net>, Steven McGahey
steve.shirt.mcgahey_at_virgin.shorts.net> writes

On 27-Dec-2004, "Steven McGahey" <steve.shirt.mcgahey_at_virgin.shorts.net
(remove two items of clothing)> wrote:

Plus, I can't imagine using a soldering iron with such small
components and gaps.

I meant "desoldering iron", not "soldering iron".

- Steve.

On Tue, 28 Dec 2004 17:00:46 +0000, dd wrote:

2 further items to assist a good light source and a magnifierliquid
flux helps too

I once actually found a use for liquid rosin - I used it to make my
hands sticky so I could get a grip on some cable-bundling tape in a
piece of equipment that was all covered with hydraulic fluid.
All I've ever been able to accomplish with it in electronics is gum
up the board and make it harder to clean.

But I do recommend a good magnifier, and a good source of light.

Good Luck!
Rich


In message <jmfAd.86$By2.50_at_newsfe6-win.ntli.net>, Steven McGahey
steve.shirt.mcgahey_at_virgin.shorts.net> writes

On 27-Dec-2004, "Steven McGahey"
steve.shirt.mcgahey_at_virgin.shorts.net
(remove two items of clothing)> wrote:

Plus, I can't imagine using a soldering iron with such small
components and gaps.

I meant "desoldering iron", not "soldering iron".

- Steve.

On Tue, 28 Dec 2004 20:02:45 GMT, Rich Grise <richgrise_at_example.net
wrote:

On Tue, 28 Dec 2004 17:00:46 +0000, dd wrote:

2 further items to assist a good light source and a magnifierliquid flux
helps too

I once actually found a use for liquid rosin - I used it to make my
hands sticky so I could get a grip on some cable-bundling tape in a
piece of equipment that was all covered with hydraulic fluid.

Hmmm...the solid stuff is put to good use by violinists, and baseball
pitchers use the powdered version. I wonder how much stickier liquid
rosin is than pine tar, or is it?