Werner, Thanks for your response, The thinking behind the resist contolling the lateral spread of spheres in BGA lands has developed as follows:- The collapse of eutectic solder spheres means the stand off height of the device is reduced. In the earlier days of BGA (2 years ago) as we introduced a device the general thinking coming out of "American BGA groups" was the height of the standoff could be controlled by the diameter of the copper pad. A small diameter copper pad could contain the lateral spread and thus maintain a reasonable standoff. The practice of this I found to be untrue as test microsections showed that the solder spread beyond the edge of the copper pad. In various examinations I found that what did control the spread in certain cases was the solder resist. This is perfectly reasonable to assume since the inherent quality of the material is to do just that. One of the biggest BGA processor manufacturers now call for the lands to be defined in the mask(resist). I assume that this is their reason for doing so. I have seen your dimensions in action already on a large BGA processor and the balls do spread to the edge of the resist. Have you seen any situations where the solder sphere continued it's lateral progress beyond the resist's edge under the weight of the device? ############################################################## 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. For the technical support contact Dmitriy Sklyar at [log in to unmask] or 847-509-9700 ext.311 ##############################################################