Hi Bill,
A solderball is basically a "glob" of solder that is either stuck to the surface or
entrenched in a material where it should not be (sorry, as generic as I can put it). There are
different types of solderballs (depending on how and where they are stuck) and caused by
different issues. Some examples and causes are: 1) solderball stuck on the surface of the
soldermask- Many causes including, flux density or preheat too high, undercured soldermask
(typically more entrenched). soldermask tooooo Thinnnnn. Poor postclean. 2) solderball stuck
on the edge of a mask clearance- Exposed circuit from excessive undercut, cleaning, mask curing,
etc, etc. Instead of boring you with all the history, It is possible that a poorly aligned
solderpaste stencil can cause a solderball, but Look at the placement of the solderball, Webbing
characteristics between the SMT pads, and cross section the area to find out where it is attached
to. This may give you a clue as to the cause. Sounds like they may also be depositing a heavy
amount of paste and possibly using a noclean environment? There are other causes on SMT
technology also to include the profile of the smt reflow unit, solderpaste itself, cleanliness of
the board, etc. I am not an assembly guru (far from it), but have seen some "interesting"
solderballs. (No jokes please, I was being good about it). JOHN WAITE
[log in to unmask] wrote:
> Hi all I have what I am sure amounts to a dumb question but I have to
> know.I have a customer that I talked to and they told me that they
> thought that the stencil step was off from the panel step and it was
> causing solder balls.I have read in the past on this site a little about
> solder balls but paid no mind to them (silly me) but now I have to.
> My question is what is a solder ball? And does or can an off step cause
> them.
>
> Thank you Bill Dworak
>
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