It is possible to change you resin desmear process (e.g. permanganate) to "roughen" the filled resin surface before the electroless plating. Several photoimageable dielectric processes (e.g. IBM SLC) uses this technique to achieve improved copper peel strength. Mason Hu Zycon Corporation ______________________________ Reply Separator _________________________________ Subject: GEN: Blind via Fill Author: [log in to unmask] at corp Date: 12/2/96 9:38 AM Hello all, I have a question on blind via which fill / partially fill with prepreg resin during lamination. Assume an 8 layer board, blind via 1-6, SMOBC, .062", standard in other ways.... ASCII Graphic _______ _______ Copper Layer 1 xxxxxx|___A___|xxxxxx A = Copper Layer 1 in partially filled via hole xxxxxx|xxxxxxx|xxxxxx FR-4 | resin |FR-4 FR-4 "x" and plated via hole wall "|" xxxxxx| blind |xxxxxx -------x via x------- Copper layer 6 xxxxxxxxxxxxxxxxxxxxx ---------------------- Copper layer 8 In area "A", above, the resin fill does not go the the surface of the board. This is a partially filled blind via, and is an acceptable condition. However.... The surface of "A" is plated with electroless and pattern plated. The electroless/plated copper has very poor adhesion on the resin in the hole, and peels off in various subsuquent processes, especially solder coat. I understand that the "fill" resin surface is very smooth which causes the adhesion failure. It is my assumption that this is a typical condition for "unfilled" vias. Is this a vaild assumption? Are there any situations when this condition poses is a problem? Do others allow partially filled vias? IPC-RB-276 accepts a 60% fill for buried vias, but silent on blind vias. I know that others are trying to use this filled via construction as a surface mount pad (God help you), what experiences do you have with partially filled vias? Thanks for the responces. -- George Franck Jr Raytheon E-Systems Product Assurance Engineer Falls Church Va *************************************************************************** * TechNet mail list is provided as a service by IPC using SmartList v3.05 * *************************************************************************** * To unsubscribe from this list at any time, send a message to: * * [log in to unmask] with <subject: unsubscribe> and no text. * *************************************************************************** *************************************************************************** * TechNet mail list is provided as a service by IPC using SmartList v3.05 * *************************************************************************** * To unsubscribe from this list at any time, send a message to: * * [log in to unmask] with <subject: unsubscribe> and no text. * *************************************************************************** * If you are having a problem with the IPC TechNet forum please contact * * Dmitriy Sklyar at 847-509-9700 ext. 311 or email at [log in to unmask] * ***************************************************************************