For alternative finish boards we do not reduce the apertures we go 1:1
Dave Chapman
Manufacturing Engineer
Circuit Service Inc.


-----Original Message-----
From: Tempea, Ioan [mailto:[log in to unmask]]
Sent: Wednesday, October 23, 2002 1:23 PM
To: [log in to unmask]
Subject: [TN] Nonwetting on ImAu, REAL message


Sorry, the finger hit send too fast.

Hi Technos,

I just saw a copy of the desk reference manual IPC-DRM-SMT-C, in normal
language the Surface Mount Solder Joint Evaluation excerpt from IPC-A-610C.
I would need your opinions on the paragraph treating the nonwetting (page
35).

The manual shows a fine pitch IC, on ImAu pads, with pretty uniform and well
wetted joints, but the solder does not go all the way to cover the whole
pad. The tips still show the gold. This is presented as a defect.

Is it really a defect? With extra large pads for fine pitch, we all reduce
the apertures of the stencils. In this situation, there will not be enough
solder to wet all the surface of the pads. What about the homeplated
apertures? No way that the chopped corners will be covered with solder.

So, I guess you know, there are big issues with the inspection.

Please let me know what your experience is with non HASL finishes. Do have
the solder covering 100% of the pad after reflow?

Thank you,
Ioan

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