Hi Gaby > http://alphametals.com/products/solder_solutions/pdf/pillowhead.pd > This report is interesting froma number of perspectives. The report states as the "Failure Mechanism:" It appears most reasonable that the opens have actually been created during the second soldering operation. This can be easily confirmed by comparing electrical test results on some BGA’s before and after the second soldering operation. During this second soldering operation, warpage has been experienced by the BGA package due to initial package conditions (amount and direction of ‘set’ and moisture content), and the thermal conditions of the soldering process (preheat and reflow temperatures and times). The extensive thermal environment during the second soldering operation has resulted in the liquification of the previously reflowed connections, and along with the extreme warpage in certain areas, particularly around the BGA package periphery, has extended the now molten solder connections beyond their cohesive limits. The separations thereby created, along with the lack of active flux at these locations, have resulted in a skin of oxide on the two surfaces resulting from the separation. Upon cooling, reduction of the warpage condition, and depending upon the exact timing of solidification, these two separate solder globules have made contact and have resulted in the various conditions observed during the microscopic investigation of their microstructures. The observed separations have occurred where the generated oxide films on the two solder surfaces have not fractured upon reinitiation of contact and allowing them to rejoin into one continuous globule. Instead, the significant oxide film has created both a physical and electrical barrier as detected during ICT. The observed deformation of the larger globule on the component side, is the result of the slightly faster solidification of the small solder globule left on the motherboard attachment site. Upon subsequent contact of the ‘oxide enveloped’ , and ‘still molten’ larger globule, deformation and deflection of this larger globule takes place as it is pressed against the now solid mass on motherboard attachment site. Where the oxide layers have broken, the two globules have merged to varying degrees again, forming a number of peculiar shapes as observed during microscopic examination of the microstructures and as illustrated also in the attached photomicrographs. Unfortunately, this is pure technical nonsense and physically impossible. There is no way that a second soldering operation can cause the observed problem—separating a properly formed solder joint into 2 globules, with the same volumes as the initial BGA balls and the initial solder paste volume, no less. If solder joints are liquid, component warpage can not separate them, because they will 'stretch' because of surface tension to more than double their thickness without separation. This shows that even very reputable companies, like Alpha Metals, cannot control what some of their employees publish in their name, anonymous, no less. Werner --------------------------------------------------- Technet Mail List provided as a service by IPC using LISTSERV 1.8e To unsubscribe, send a message to [log in to unmask] with following text in the BODY (NOT the subject field): SIGNOFF Technet To temporarily halt or (re-start) delivery of Technet send e-mail to [log in to unmask]: SET Technet NOMAIL or (MAIL) To receive ONE mailing per day of all the posts: send e-mail to [log in to unmask]: SET Technet Digest Search the archives of previous posts at: http://listserv.ipc.org/archives Please visit IPC web site http://www.ipc.org/contentpage.asp?Pageid=4.3.16 for additional information, or contact Keach Sasamori at [log in to unmask] or 847-615-7100 ext.2815 -----------------------------------------------------