Dewetting of a solder film has the appearance of water on a greasy surface.
It arises when a surface is wetted initially and the solder adheres to the
solid metal surface but retracts after a time due to an increase in the
contact angle causing the solder to collect up into discrete globules and
ridges. Although the remainder of the base metal surface retains the color
of solder, this solder layer si thin and its surface has poor
solderability.

Ruben




[log in to unmask] on 04/01/98 11:43:42 AM

Please respond to [log in to unmask]; Please respond to [log in to unmask]

To:   [log in to unmask]
cc:    (bcc: Ruben Irizarry)
Subject:  [TN] De-wetting




Hi guys,

Please help me out on this. I need your help regarding the exact
definition of de-wetting defect on smt land or pad (PCB manufacturing)
Based on the IPC definition, the way I understand it, is that,
de-wetting is a defect that is caused by the failure of solder
coating/plating process to coat the copper surface evenly. The solder
coating is unevenly distributed on the copper surface. Thus, there is
thin and thick coatings on the surface. Am I right? What's the
accept/reject criteria for this defect? What is the minimum and maximum
thickness of solder coating?
Thank you very much for your time. I'll be waiting for your responses.

regards,
Martin

P.S. I'll appreciate it very much if you can send me a photo via
attachment file.

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