[sdiy] ASM Capacitors/Bench Power Supplies

[Jay Schwichtenberg]

Ian and all,

Digikey has had the Panasonic lines ECW-U (PEN) and ECH-U (PPS) for quite
some time. I used ECH-U caps in audio DAC filters. I don't know if they
added to the sound characteristics. I do think that they made a difference
in the consistence between boards.

A word of warning when using these puppies (at least the Panasonic ones).
Read the data sheet before using them!

When we were using them there was an issue with pad size. I went back to see
if I could find a reference to this on Panasonic's WEB site but couldn't.
They do spec the pad size in the data sheet but I no longer have the
standard sizes around so I can't compare them. If you aren't going to have
boards flow soldered it's probably irrelevant anyway. But they were having
problems with the caps floating. Got looking into it and in the data book
from Panasonic they recommended a slightly bigger pad size.

Next remember this things are plastic and plastic melts. If you are hand
soldering them be very, very, very careful. You can melt them and if you are
using something to hold them down it can deform them very easily. I would
take a round tooth pick, clip the end off with dykes, squeeze the end with
my needle nose to flatten it and very carefully (ie as lightly as possible)
put pressure on the opposite pad I was soldering to hold it down. Also I
found if you have to remove these it will probably be toasted in the
soldering/desoldering process. Toss the part and get a new one. Also if you
a choice of size, use a bigger part.

I would solder a few on a test/junk board before I would go to a real board.
Another thing is I'd save soldering these to after the board has had the
final wash and until the last possible point in assembly soldering them with
no-clean flux solder.

When building SMT by hand it gets weird and you have to be smart about how
you lay things out and build them. Since you can't just stick parts in a
board and have easy access to the bottom to solder it gets a lot trickier.
SMT stuff is all soldered on one side and you have to be critical of access
(getting that big soldering iron tip close to the solder joint) issues. You
typically build from the bottom (lower components) up (bigger components)
just because of access. There is an issue of thermal conductivity when doing
surface mount by hand too. You can have a bunch of parts down on a board and
go to solder another part down and the heat is transferred to the other
parts pads desoldering it. This is more of a problem with boards that don't
have a solder mask. So be smart when you do your board layout. Don't go for
max density on your first board.

Sometimes thru hole is so much easier.
Jay

> -----Original Message-----
> From: owner-synth-diy at dropmix.xs4all.nl
> [mailto:owner-synth-diy at dropmix.xs4all.nl]On Behalf Of Ian Fritz
> Sent: Thursday, July 31, 2003 9:50 AM
> To: Neil Johnson; Steven Downhill
> Cc: Synth DIY (E-mail)
> Subject: Re: [sdiy] ASM Capacitors/Bench Power Supplies
>
>
> At 03:32 AM 7/31/2003, Neil Johnson wrote:
> >Steven,
> >
> >1. Polystyrene capacitors are needed for the oscillators because of their
> >excellent low leakage and stability.  As is the way, they are therefore
> >more expensive than polyester or ceramics, which are fine in other places
> >(I use polyester for audio path, and ceramic for decoupling).
>
> Does anyone know of a reason not to use NP0 ceramics for the integrating
> cap? I briefly tried both NP0 and polystyrene in my last VCO and
> didn't see
> any difference in waveshape or tracking.  The NP0 has a smaller
> tempco.  Also it seems to me that the high-grade mica units, although
> expensive, should work better than polystyrene.
>
> Also, PEN (polyethylene naphthalate) and PPS (polyphenylene sulfide) look
> interesting.  Mouser has some CD PPSs in chips, the only ones I have seen
> readily available.
>
>    Ian
>