How inane, but what's changed? What processes as solder or flux composition,
or board configurations, or handling, or plating, or maintenance, or
calibration - have changed? If it worked before, didn't it, what is
different in the process.

Of course, the board thickness and thermal mass is "impossible" but it
worked before, right? How well did it really?

Earl Moon
----- Original Message -----
From: Tempea, Ioan <[log in to unmask]>
To: <[log in to unmask]>
Sent: Monday, October 04, 1999 3:45 PM
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.
>
> ______________________________
> ______                                ______  I
> ______                                ______  I
> ______                                ______  I
> ______                                ______  I
> ..                                          ..
> ..
> ______                                ______  I
> _______________________________ 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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