Darrell

It seem that there is some confusion between SOLDER coverage and SOLDERMASK
coverage.  IPC-RB-276, the bare board spec, allows exposed copper (copper
that is not covered with solder) along the vertical edges and 1% of the other
conductor surface that is not covered with soldermask or meant to be
soldered.  The same specification, IPC-RB-276 Amend. 1, does not allow voids
or pinholes in the SOLDERMASK on the "conductor surfaces" of bare boards in
any area where solder mask is required, but does allow touchup; vertical
edges ARE NOT excluded from soldermask coverage.  IPC-A-600E reflects the
requirements of IPC-RB-276.

The soldermask coverage requirement on bare boards is to prevent inadvertant
solder balls attached to the conductors after soldering and which could cause
shorting.  After the soldering is done and the "soldermask" has done its job,
some defects in the soldermask coverage is allowed per IPC-A-610B Amend.1.
 Of course. the word "base copper" was omitted becasue many of the metals
under the soldermask are not always copper.  The wording now states that
these are okay after assembly if they do not bridge adjacent conductors, but
I think the intent was to line out "base copper" and leave it as "expose
conductor surfaces".  Perhaps the task group chairman of the A-610 group
needs to clarify the wording and its meaning   

Phil Hinton 
Hinton "PWB" Engineering 
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