Hi Steve,
By the time the pallet is aleady made this situation is tough to fix. If
you can afford new pallets, rotating the assembly and soldering at 45
degrees to the conveyor direction will virtually eliminate the problem.
Maybe the board is small enuf to make an angled pallet for the original
pallet (confused?). Also, solder cheaters on the board can be added to
relieve the 'snap off' problem if you would like to redesign the board (Ha
Ha)
Jim.
> -----Original Message-----
> From: Paul Klasek [SMTP:[log in to unmask]]
> Sent: Monday, July 26, 1999 11:09 PM
> To: [log in to unmask]
> Subject: Re: [TN] Selective Wave Solder Pallet Problems
>
> Hmmm ,'m not a pallet guy , but we could screw a little (countersunk self
> taper through a decent copper shim) ;
> could we ?
> Pallet folks may have a problem with this is fairly specific .
> Good to see you in coat again .
>
> paul
>
> -----Original Message-----
> From: Stephen R. Gregory [mailto:[log in to unmask]]
> Sent: Tuesday, 27 July 1999 13:05
> To: [log in to unmask]
> Subject: Re: [TN] Selective Wave Solder Pallet Problems
>
>
> 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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