It is both for assembly and performance when considering some past applications and studies. The EMPF used to be part, or all, of the Navy labs in Indy. I and others were involved with building some of the first digital engine controls for Pratt & Whitney evolutionary engine technologh. Some planes and pilots were lost when first launched with the product. I can't remember everything, as I'm sure many of you can, but the FA findings came down to, basically, one thing. Polyimide MLB's had a problem because they were being cured/burned/cooked in the press too long trying to reach their maximum Tg of 270 C. It also was found that the initial foil and innerlaminar bond strength were reduced siginificantly over short periods at that Tg. Foil bond strength, as an example, was reduced from about 7 pounds to less than 1. Shocking enough unto itself but consider all the other 80's type historical facts concerning polyimide wiring insulation and its problems associated with fly by wire technology early on the the F-16 prgram where, again, several planes and pilots were lost. For me, though not a normal personal trait, moderation is the key to success in taking any design to successful verification and validation. Lowering the final cured Tg of polyimide, to about 250 C, enhances both its foil and innerlaminar bond strengths. The reason, to put it simply, is reduced oxidation of all materials in the MLB structure. In my most recent endeavors, as well as many others, a BT/epoxy blend, providing a "good" all around Tg is the material of choice. This is evidenced by my work, with many others, concerning very high layer count, very complex MLB's in excess of 50 layers with all manner of blind, buried, and micro vias. Still, as having before said, there is nothing like polyimide in an open press like some of the old PSI version. Again, to specify high Tg materials for high Tg's sake, without taking into critical consiserations and plating thickness and ductility, is ludicrous. Earl Moon --------------------------------------------------------------------------------- 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 the following message: SET Technet NOMAIL 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 ---------------------------------------------------------------------------------