Folks, I have been reviewing all the issues/problems that were faced by my host company and its supplier ? before I arrived. I would like to share some for comment as well as my observations, if you would be so kind. We have one board design using seven .8 mm ceramic CSP?s made by TI. The first issue facing my company was cracking or separation of balls from the device. I have reports from Rockwell, who did the F/A and from TI both pointing to the failure mechanism as possible excessive IMC formation as in the following without the photos, of course: Attached are four photos: CSP-1 shows multiple insertions into sockets. CSP-2 shows x-section of stock unit CSP-3 shows magnified x-section of stock unit. Ni/Sn intermetallic layer appears thick. CSP-4 shows x-section of device which broke off the PCB - clean break at the intermetallic layer. Because of the multiple insertions into sockets, as evidenced by indentations on the balls, it is considered that multiple thermal excursions contributed to IMC growth. As the clean break occurred at the IMC interface, again, this is thought to be the failure mechanism. This may be so, but other things must be considered as well. This issue possibly was resolved with TI?s "prototype" parts and we?ve seen no repeat of this occurrence. No reason is available to me, at least, concerning the part?s improvement. No matter, there now exist other issues. I believe, as in a few comment trades, with others (Dave Fish for one), that our assembler?s inexperience profiling and soldering these devices has been responsible for poor quality/reliability solder joints. In their defense, there aren?t/weren?t many suppliers with this experience. Simply, cold solder joints probably contributed to unacceptability and complete failure as received ? evidenced by the infamous "C" clamp. The ceramic portion of the device is extremely massive compared to ball size and the ability to get required heat to the solder medium and balls to effect acceptable solder joints. This means, I believe based on past experience, the reflow profile must be "maxed" out in terms of solder paste performance and joint formation. I don?t think this was done. To add to the situation, the CTE mis-match of ceramic and PCB material certainly has been known to ruin even good solder joints. This may account to the failure at the IMC interface as well as at the board level. Therefore, a "too thick" IMC layer probably is/was not the failure mechanism, or was it? All solder pads have been re-evaluated and now definitely meet alignment and size requirements. Stencil apertures are as specified. Solder paste now is Kester?s 562R, solder volume is acceptable, surface solderability is as required. What remains is developing a solder reflow profile that will effect acceptable solder joints for the CSP?s as well as all other devices on the board. I realize this should not be a big issue, but having had to go way back to visit initial failures at the device ball interface, I have some concerns about whoever builds our next lot of boards. Steve, are you listening. I would appreciate any comments concerning this small part of the picture. I would appreciate anyone sharing experiences with what should be another BGA success story but for what I have presented here. Thank you all much, Earl --------------------------------------------------------------------------------- Technet Mail List provided as a free service by IPC using LISTSERV 1.8d 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 delivery of Technet send e-mail to [log in to unmask]: SET Technet NOMAIL To receive ONE mailing per day of all the posts: send e-mail to [log in to unmask]: SET Technet Digest Search previous postings at: www.ipc.org > On-Line Resources & Databases > E-mail Archives Please visit IPC web site (http://www.ipc.org/html/forum.htm) for additional information, or contact Keach Sasamori at [log in to unmask] or 847-509-9700 ext.5315 ---------------------------------------------------------------------------------