Forwarded from:

     Andy Brannen - Applications Engineer
     Rogers - Circuit Materials Unit
     Tel: (602) 917-5204
     Fax: (602) 917-5256
     E-Mail: [log in to unmask]


______________________________ Forward Header __________________________________
Subject: Re[2]: Dendritic Growth?
Author:  Andy Lloyd Brannen at Rogers-MCD
Date:    10/9/95 8:31 AM



The below paragraph leads me to wonder if the PWA had soldermask or coverlay
on the top surface or was merely solder coated as many boards are.  If it were
merely solder coated, failure to meet minimum standoff values of Mil-Std-2000A
would have resulted in insufficient flux cleaning beneath the chip and the
resultant short.  Flux, even RMA, if not properly removed after soldering,
will act as a facilitator in developing the condition described (latent shorts).

     _
   "Analysis of the PWA revealed a short had developed between two
parallel traces underneath an IC.  The traces are .006" wide and .010"
apart.  The short was not visible (even under a microscope).  The short
was approximately 2 1/2 ohms in value.  Once a razor was run between the
traces the short was eliminated and the PWA was functional once again."