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April 2001

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Subject:
From:
"Tempea, Ioan" <[log in to unmask]>
Reply To:
TechNet E-Mail Forum.
Date:
Wed, 4 Apr 2001 14:43:24 -0400
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text/plain (48 lines)
Hi,

some time ago, Mike Bailey brought up a situation of random non-wetting on
the secondary side. Well, I run into a somewhat similar problem right now.

After wave soldering, I see SMT passives that are on the solder side
exhibiting either non-wetting at all, or one side soldered while the other
one looks just like before the wave, no sign of wetting. Even on the pads
without components, the situation is the same, some pads have absolutely no
trace of solder, while the adjacent ones collect solder without any problem.
Not related to shading, since bad spots are even far from any component. Not
related to glue contamination either, since I have trouble even with pads
without components.

To make it even more complicated, there is no problem to hand solder the
non-wetted pads, after the wave.

I refreshed the flux, ran the assemblies on two totally different machines
(different preheating, fluxing), with the same poor result.

The process is:
glue & insertion + reflow at 120C for the bottom side, only passives
populated
paste & insertion, reflow for the top
wave with no-clean X33 flux from Multicore and regular eutectic solder
board is HASL

I know this is a mild flux, but it does a great job for us on much more
demanding assemblies. I will try a stronger one, but cleanliness is a big
issue.

Now, I would like to know if Mike found something and if he could fix
anything.
Besides that, any hint that Technet could give would be largely appreciated.

Thank you,
Ioan

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