In a message dated 09/06/2000 11:43:51 AM Central Daylight Time, [log in to unmask] writes: > Thechneters, > > I'd like to know if there are special design rules for the solder mask on > PCB. > Most of PCBs I have seen have pads surrended with a gap and solder mask. > In our case I have got a PCB with solder mask on the periphery of BGA pads > (to prevent bridging according to the customer). > It seems to me that the solder mask on the periphery of pads is not so > efficient as expected to prevent bridging and it seems to be also > responsible of the poor mechanical properties of the joint. > Does anybody have experience with this weird technique (solder mask on the > periphery of pads)? > > Thanks in advance, > > > Walter Horaud Hi Walter! I believe you're referring to Solder mask defined pads vs. Non Solder mask defined pads. You're right when you say that it reduces reliabilty of a BGA solder joint. Go to: http://extra.ivf.se/ngl/E-BGA/ChapterE2.htm and you'll find an article that addresses that very issue. The article also states that there maybe an occasion in which it is better to use a solder mask defined pad on the PCB, that is if the BGA device has solder mask defined pads to which the balls are attached. -Steve Gregory- ############################################################## TechNet Mail List provided as a free service by IPC using LISTSERV 1.8d ############################################################## 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 ##############################################################