I cannot fully understand your question, but it appears that the construction you describe is not that of a typical TBGA. A normal wire bonded TBGA is constructed as follows: The polyimide flex circuit film is adhesively bonded to a copper stiffener with an opening in it to expose the die attach and wire bond area. The silicon die is die attached to the film using a fairly typical epoxy-based material. The die is wire bonded to the flex. The die and wire are encapsulated. Solder balls are applied to the bottom side of the flex. There are many variants to this construction to provide die-down configurations and flip chip configurations. In one variation, the copper has a depression formed to act as a die attach cavity, and the flex unit (with an opening to match the die attach cavity) is bonded to the cavity side of the copper stiffener. The die is then wire bonded to the flex and encapsulated. Here the stiffener also acts as a heat spreader. In all designs the copper stiffener keeps the solder balls coplanar, and allows the TBGA thermal expansion to be reasonably close to the motherboard CTE. Regards, Leo Higgins -----Original Message----- From: Louis, Edwin @ CSE [mailto:[log in to unmask]] Sent: Wednesday, October 02, 2002 8:30 AM Subject: TBGAs Does anyone have experience using TBGAs? I understand that a thermal bond is made between the lands on a ceramic chip and a Copper laminate tape to which is added solder balls on the bottom of the tape to make bond to PWBs. This is supposed to solve the CTE difference problem. What is the nature of the chip bond to tape and how and why does it survive CTE differences? Does anyone out there have thermal cycling data on them and assembly experience with them? ---------------------------------------------------------------------------- ----- Technet Mail List provided as a free 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/html/forum.htm for additional information, or contact Keach Sasamori at [log in to unmask] or 847-509-9700 ext.5315 ---------------------------------------------------------------------------- ----- --------------------------------------------------------------------------------- Technet Mail List provided as a free 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/html/forum.htm for additional information, or contact Keach Sasamori at [log in to unmask] or 847-509-9700 ext.5315 ---------------------------------------------------------------------------------