From personal past experiences, the removal, addition, or reworking of
components or wires after assembly is prone to cause disaster. Usually the
solder attachment method used (typically a soldering iron) is uncontrolled
and not monitored to the levels required.

I have seen exactly the failure that you are talking about. In this case a
wire jumper was hand soldered into a via using a soldering iron. The via in
questions was connected to signal in an 8 layer pwb. After attachment, the
via was showing open. Microsection analysis resulted in a total detachment
of the inner layer plated barrel to the inner layers, IE total interconnect
separation! Also evident were pad lifting, laminate voids in ZONE A and
resin recession, all evidence of extreme thermal abuse. What was most
revealing was the fact that in the same cross section, a via less than 0.040
inches away from this hole was perfect! A brief review of the hand soldering
process revealed that although the procedures specified a maximum soldering
iron tip temperature of 600 deg. F., the actual temperature setting was 750
deg.F on the shop floor.

I suspect from your brief description, that the barrel integrity is
destroyed during the localized thermal abuse of hand soldering and/or wire
removal. If not, then the general product quality of the bare board may be
suspect. Cross section analysis of 'unaffected' vias should establish which
of the two scenarios are most likely occuring.

Dave Rooke
Circo Craft - Pointe Claire
a division of Viasytems
= = = = =
>We seem to have a minor problem when working on select components.
>
>Boards are 8-layer GIL 2 planes at layers 2 and 7.  We solder in test leads
>to the select component locations determine the select value required
>through testing,  remove the test leads and install the selected device.
>
>Periodically we have had opens after soldering the device in place and have
>determined that it is always at a signal interface on an inner layer.  That
>is to say not where there is a thermal pad on a plane.  We attribute this to
>the soldering process, dwell, temp.,etc.  What I'm concerned with is the
>mechanism.  After x-sectioning the areas in question, it appears as though
>the barrel copper has separated from the layer.  IE electroless copper bond
>is weak or some other cause.
>
>What experience have you had and what did you do to fix it?
>
>"Thanks for your support" (B&J)
>
>Richard MacCutcheon
>BFGoodrich Aerospace
>Data Systems Div.
--- EOF ---

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