Hi Jorge,
There are a number of reasons for solder beading:
        Too fast ramp rate
        Too much paste being put down (too thick stencil or too big aperture)
        Placement machines out of calibration (pushing component into paste)
        High R.H. in factory (paste absorbing moisture)
        Paste hot slump
        Poor board design, etc., etc.
I realize you're thinking your process is out of control, but is it that big
of a deal with water washable?  Just curious....

Chris @ ICA

-----Original Message-----
From: TechNet [mailto:[log in to unmask]]On Behalf Of Jorge Rodriguez
Sent: Tuesday, August 21, 2001 2:57 PM
To: [log in to unmask]
Subject: [TN] Solder Beads (not solder balls)


Fellow technetters,

We are having tons of issues with solder beading, even on boards were we
didn't have the issue before. We're clueless, we suspect of the solder paste
(63-37 Water Soluble), it looks slumpy amd watery, but we're not sure. I
know solder beading can be solved by designing the stencils with home-base
aperture, but what we're seeing here is across the board, not just one
particular assembly but several. Does anyone have experience dealing with an
issue like this?, could solder beading caused by the oven profile or is it
more like solder paste related?


Any comments would be appreciated.


Jorge Rodriguez
Process Engineer
Varian Electronics Manufacturing
E-mail: [log in to unmask]

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