Loan,

Are you sure this is really a cold solder joint or is it just a dull
looking solder joint?  It also sounds like you are having some problems
with getting good topside fillets.  This all sounds like it could be a
solderability problem with the components in question or a fluxing problem.
I don't understand the 2 passes though.  Why wouldn't you flux, preheat and
solder in 1 pass?

Ken Kirby
Speedline Technologies




 (Embedded
 image moved   "Tempea Ioan" <[log in to unmask]>
 to file:      10/04/99 03:45 PM
 pic30847.pcx)




To:   [log in to unmask]
cc:    (bcc: Kenneth Kirby/ElectrovertUS/Cookson)
Subject:  [TN] Cold solder




Hi Technos,

I'm in big trouble with a backplane.

It's a 13.5"x19.5", 3.7mm thick. The connectors are disposed in parallel
lines, forming two columns a the two extremities. In the middle we have no
components. In between the connectors there are some TH caps and resistors.

______________________________
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_______________________________ I

For a long time the soldering was OK, with small problems in the four
corners ( a couple of holes not 100% full).

For about a week or so, the solder joints of many caps or resistors present
cold solder. There are no significant cold solder problems with the
connectors, which present though a little less wetting (some of the fillets
are not what they used to be).

The question is: why do I get the cold solder and how can I get read of it?

We use :
- no-clean technology
- Multicore Sn63 solder
- Multicore X33 flux
- strong radiation preheating ( two top preheaters at 700F and two bottom
at
750F); we spent a lot of time tweaking to avoid damaging the board
- two passes, one for fluxing only, no wave, the second one right after
with
no fluxing, but with wave
- no chip wave (that's what I have, hehehe), just omega on our Electrovert
Econopak II

Any help would be greatly appreciated.

Thanks,      Ioan

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