In a message dated 7/26/99 9:35:27 PM Central Daylight Time,
[log in to unmask] writes:

> Hey all-
>
>      We use selective wave solder pallets extensively to solder through-hole
>  leads, as almost all our boards are mixed tech.  A couple types boards
>  consistently show a single short on the trailing edge of large through-hole
>  connectors.  One board always shorts on the trailing pins of a PGA socket,
>  while the other always shorts on the trailing edge of a 40-pin dual-row
>  female header.  No amount of tweaking the wave machine settings affects the
>  short.  My theory is this:  When the solder leaves the larger pallet
>  openings, it has nothing to "snap" to.  Therefore, it "snaps" to the last
>  couple of pins it leaves.  I have made sure that the solder flows off the
>  back of the wave at the same speed as the conveyer.  Has anybody else seen,
>  or heard, of this problem with selective solder pallets?  The advantages of
>  reflowing bottom-side components make wave soldering the whole bottom-side
>  unfeasible.  Speaking with the pallet house has left us with grooved pallet
>  bottoms and chamfered openings; but the problem remains.  Is there a way to
>  alter the selective wave solder pallet openings to avoid these "snap-back"
>  shorts?
>

Hi ya Ryan!

Yeah, I've seen this before, and my my solution is a bit of a pain in the
butt, but if you go out and get some copper tape (you can get it at a
electronics store like Fry's, or maybe even radio shack carries it...) just
put a little strip at the trailing edge of the openings that you're having
problems with, it'll provide another surface for the solder to wet to besides
the last pins of the connectors or whatnot that's getting the bridges. You
may have to experiment with the positioning, and the amount of surface area
where you'll put these, but it'll work once you get it down. Make sure your
pallet is really clean when you put the tape down.You may have to replace
them now and again because the adhesive that's normally on these types of
tapes ain't made to go thru wave solder temperatures, but they'll hold for a
while...if you're lucky, they'll stay stuck to the pallet for a decent amount
of time before you need to replace the tape. Like I said, it IS a pain...but
you should be able to keep those pesky bridges from occuring once you get the
position of the tape down...

(HEY! WAVE SOLDER PALLET GUYS! THIS IS A PROBLEM! COME UP WITH SOMETHING SO
WE DON'T HAFTA USE THIS TAPE DEAL!)

-Steve Gregory-

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