Another successful approach for controlled X and Y and LCC is to use a Thermount based system. One major aerospace company successfully replaced its copper invar copper designs with it. ----- Original Message ----- Wrom: GMEPYOQKEDOTWFAOBUZXUWLSZLKBRNVWWCUFPEGAUTFJMVRES To: <[log in to unmask]> Sent: Wednesday, October 20, 2004 6:59 AM Subject: Re: [TN] Picture of LCCC Solder Joints... > The laminate on this is indeed FR4 (minimum Tg 140C) thus there's a huge > CTE mismatch which the solder joint can't accommodate very well! This case > was from a test board (not an actual assembly) but I wouldn't combine BT > or > Polyimide laminate materials with LCC style components - ya just can't > revise physics! I have observed the use of controlled CTE laminate > structures (like a Copper Invar Copper core construction) successfully > with > LCCs but I view that configuration as an expensive solution for not > understanding design basics. LCC's were the first type of components which > exposed the issue of using the solder joint as both the mechanical and > electrical connection to the pwa - some lessons are just learned the hard > way. > > Dave > > > > Joyce Koo > <[log in to unmask] To: [log in to unmask] > com> cc: > Sent by: TechNet Subject: Re: [TN] Picture > of LCCC Solder Joints... > <[log in to unmask]> > > > 10/20/2004 08:45 > AM > Please respond to > jkoo > > > > > > > I bet the orginal assembly is qualified using polyimide board (x-y CTE > mismatch is not much), but someone in the later stage changed to FR4 > without > knowing the impact... > Are you using FR4? No answer required...(you can take a "fifth"). > jk (1.59 cents) > > -----Original Message----- > Wrom: KPNKMBIPBARHDMNNSKVFVWRKJVZCMHVIBGDADRZFSQHYUCDDJBLVLMHAAL > Sent: Tuesday, October 19, 2004 7:32 PM > To: [log in to unmask] > Subject: [TN] Picture of LCCC Solder Joints... > > > Hi All! > > Dave Hillman so kindly sent me a picture of some LCCC solder joints after > thermal cycling > after 500 thermal cycles of -55C to +125C (per IPC-9701 guidelines). > Needless to say it has failed! (CAUTION! Parental discretion is advised > before > viewing!) Go to: > > _http://www.stevezeva.homestead.com_ (http://www.stevezeva.homestead.com) > > Look at: "LCCC after thermal cycling" > > I build assemblies using LCCC's here, 32-pins or lower...mostly radar > stuff...been putting them on assemblies for as long as I've been here. > Don't know > exactly why our customer still uses them, maybe that's the only package > they > can get the devices in...and maybe the smaller packages don't have the > same > CTE mismatch problems. > > There is a company that makes compliant SMT leads that can be attached to > LCCC components, and I think that they have a service that will do that > for > you. > It's Interplex NAS, go to: > > _http://www.interplexnas.com/index.asp_ > (http://www.interplexnas.com/index.asp) > > If you absolutely have to use LCCC's, and they're bigger than 32-pins, you > might check them out. > > -Steve Gregory- > > --------------------------------------------------- > 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 > ----------------------------------------------------- > --------------------------------------------------- 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 -----------------------------------------------------