Technetters,

We have a lot of a 12 layer PWB made from a High Tg Epoxy material, some 75 mil thick overall.  The board has 3 sequential laminations, and four drill operations to get the three Blind vias (BV) and thru holes in the board.  The BVs from
layer 1 - 10 terminations are visible thru the material from the Layer 12 side.  During the assembly prebake  process the tops of these little BVs delaminate.  A patteren of little white dots which closely matchs the 1-10 BV drill pattern
emerges.  I believe the BV drill size was 10 mil

Boards are 20 months old.  Assemblier was aware of the age of the boards, and the delamination occured during the pre-bake process, and thermal profile set up.

Would anyone want to discuss why a BV would be more prone to delamination than the rest of the board?

                         *** Warning: the follow contains sarcasm.***
*** For those unable or unwilling to understand sarcasm, please read no further.***

Current corrective action proposals:
1) Don't assembly old PWBs.
2) Add a ground plane between layer 11 and 12 to prevent the layer 10BV  terminations (and delaminations) to be visible from the outside of the board.
3) Blame the PWB supplier, and get them to replace the boards.
4) Willing to entertain other options.

Thanks,

George Franck

##############################################################
TechNet Mail List provided as a free service by IPC using LISTSERV 1.8c
##############################################################
To subscribe/unsubscribe, send a message to [log in to unmask] with following text in
the body:
To subscribe:   SUBSCRIBE TECHNET <your full name>
To unsubscribe:   SIGNOFF TECHNET
##############################################################
Please visit IPC web site (http://www.ipc.org/html/forum.htm) for additional
information.
If you need assistance - contact Keach Sasamori at [log in to unmask] or
847-509-9700 ext.5315
##############################################################