We just had an experience that may be similar. Our surface mount touch-up
operators noticed that many of the vias of a particular board were plugged
with solder and some of the vias actually had solder sticking out of the
holes appearing to look like solder balls. When they tried to pick some of
the ball off they realized that they weren't normal solder balls. I don't
have any bare boards to examine but it sounds similar to what Steve
described.

Is having the vias plugged with solder a major concern as long as the solder
is not coming out of the vias and causing loose solder balls or shorts??

Tim Stammely


> -----Original Message-----
> From: Stephen R. Gregory [SMTP:[log in to unmask]]
> Sent: Friday, June 05, 1998 10:46 AM
> To:   [log in to unmask]
> Subject:      Re: [TN] SOLDERBALLS on bareboards
>
>
>      As with Cobey, I've not seen solderballs on bare boards. However, I
> have
> seen what one might consider to be solderballs, but it really wasn't
> "solderballing" in the normal sense.
>
>      What had occured on the boards I'm referring to was that the fab had
> been
> HASL'ed and then after the fact, the vias were tented with plugs of mask.
> During reflow the plating became liquidous and outgassed thru a break in
> the
> mask and a little ball of solder would form, attaching itself  to the
> via's
> anular pad.
>
>        I couldn't build the second side of the board because I couldn't
> print
> with the balls being attached to the via the way they were. But not only
> that,
> the concern was that there would be contaminates trapped inside the tented
> vias.
>
> -Steve Gregory-
>
>

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