hi, this happens to us more than i'd like to admit. one approach you may take is to bond the power module to the pwb prior to soldering. this essentially fills the void between the power module and the pwb and eliminates the possiblility of voids forming later. if this power module dissipates a lot of heat, the bonding can improve the heat transfer from the module. phil crepeau -----Original Message----- From: Lum Wee Mei [mailto:[log in to unmask]] Sent: Monday, August 31, 1998 7:27 PM To: [log in to unmask] Subject: [TN] Bubbles from conformally coated board The test engineer came back to us to complain that bubbles are found along the edge of the power modules after going through the temperature cycling tests. This problems are found on both coated boards. The power modules are mounted completely flushed onto the board and subject to conformal coating using the diping method. The coated board undergo QC to ensure all components are completely coated, inlcuding the edges around the modules. What could be the problem? ################################################################ 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's web site (http://www.ipc.org) "On-Line Services" section for additional information. For technical support contact Hugo Scaramuzza at [log in to unmask] or 847-509-9700 ext.312 ################################################################ ################################################################ 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's web site (http://www.ipc.org) "On-Line Services" section for additional information. For technical support contact Hugo Scaramuzza at [log in to unmask] or 847-509-9700 ext.312 ################################################################