Hi "WTHAYER," Yes, using low-CTE PCBs can be a solution to SJ reliability problems for large ceramic components, particulalrly when done in combonation with large solder joint heights [high-melt solder balls, solder columns] or conpliant leads. But as you point out, you may be trading for other issues. Werner In a message dated 4/28/06 14:26:20, [log in to unmask] writes: > If you HAVE TO use parts like that, try a low CTE PCB material, such as > Arlon 85NT. This is nice stuff, with a listed CTE under 10ppm/C. It goes up a > bit with high copper loading. Very stable, Tg over 200C, but sucks up > moisture and is hell to board route without the edge fuzzing due to the aramid > fibers. > > >>> [log in to unmask] 4/28/2006 1:47:58 pm >>> > Hi Ioan, > Castellated ceramic leadless chip carriers were a bad idea when the were > developed in the '80s, and nothing has changed*oops, I forgot about that > SAC-stuff > making things worse. > The problem is not the 'castellations' per se, but the fact that they will > not allow the CC to swim up. Thus, the solder joint thickness is at a > minimum, > producing the worst-possible SJ reliability geometry--if you shim up the CC > to > increase SJ height, you can get about the same as what you get with BGAs > with > the same ball dimension. > Putting large ceramic components on FR-4, castellated or not, is not a good > idea. --------------------------------------------------- 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 ----------------------------------------------------- >