I have an individual posing a theoretical question to me.  Any comment or
experience would be greatly appreciated:

Our electroless Ni/immersion Au plating process takes place after
>outerlayer etch and tin strip.  Until recently, higher Tg material was the
only laminate that would develop shadow plate in this
>process.  Shadow plate is an unacceptable, granular texture plating.
>It is not uniform across the plated surface; but is concentrated along
>the lower horizontal edge of the (copper) feature being plated.
>
>For some time we have been correcting the high Tg materials' tendency
>to shadow plate by giving it a bake (310 deg. F, 50 min). We are not
>certain of the mechanisms. However, the conventional wisdom is that
>shadow plate is caused when something comes out of the laminate during
>electroless Ni plating; then rises with the outgassing.  This is
>consistent with the a concentration of the shadow plate at the lower
>horizontal edge of the feature.

Do you agree that this phenomenon is a result of a chemical release from
the laminate?

Recently, this defect has been noticed on normal FR-4 (lower Tg) material.
If you believe the shadow plating is caused by a chemical release from the
high Tg material, what could be some reasons for the emergence of the
defective condition on normal FR-4?

Thank you for your interest,

Joel Fillion

################################################################
TechNet E-Mail Forum 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://jefry.ipc.org/forum.htm) for additional information.
For the technical support contact Dmitriy Sklyar at [log in to unmask] or 847-509-9700 ext.311
################################################################