Now, I assume that U are covering those gold finger pads with capton prior printing and if U do that at the same area as printing equipment, Ur problem can simply lie in contamination by soldering paste.
Those gray dots are most likely the solder balls that the stencil or support pins are contaminated with.
Try to clean Ur printing equipment and wash Ur stencil and if U dont get those gray dots at the first printing than U know for sure...
BTW, Why do U cover finger pads with capton?
Does Ur supplier do that for U or does the operators do that?
*************************************************************************
Sasha Miladinovic - Production Engineering
Amersham Biosciences, PCB Production, Umeå
Tel: +46 (0) 90 150 232
Fax: +46 (0) 90 138 372
E-mail: [log in to unmask]
*************************************************************************
2003-04-22 08:59
Please respond to "TechNet E-Mail Forum."; Please respond to Prashant Chopra
To: [log in to unmask] cc:
Subject: [TN] problem with gold pads of the pcb
hi all,
we are using gold finger pads on the pcb. but after going thru smt process
of screen printing,component insertion, reflow and aqueous wash we are
facing the problem of grey color dots on the pads.
This problem is with the pads where no components are being placed.
There is no solder paste printing on these pads nor any components are
place there and they are being covered with Kapton tape thru out the above
process.
Can anyone point to some reasons for this problem?????
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