Earl and all,

the soldering was a lot better before. We've always had the QA on our back,
checking the flux density and the settings for the problem assemblies.
Myself, I don't recall having seen so much cold solder.

The machine had been calibrated last saturday during the monthly
maintenance, when the pot is thoroughly cleaned.

It's possible that the solder mask changed, since it's darker now. Together
with the soldering problems we started experiencing discoloration of the
solder mask on the solder side. But wouldn't this randomly affect any place
on the surface? I still get the connectors OK, with bad solder joints on the
caps and resistor networks.

There has been no artwork change. However, could some changes in the
materials or manufacturing of the board affect somehow the thermal mass here
and there? I mean, maybe the connectors drain somehow the heat from the
adjoining components.

And anyway, what on earth generates cold solder in the waving process?

Ioan
> -----Original Message-----
> From: pod [SMTP:[log in to unmask]]
> Sent: Monday, October 04, 1999 5:19 PM
> To:   [log in to unmask]
> Subject:      Re: [TN] Cold solder
>
> 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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