My colleague is adament that PTFE should have larger strain even thought has less stress, because PTFE's Young's modulus is only 3 GPa compared to BT of 14.5. I really don't know if his point is true or not. My initial reaction is PTFE has less strain, but I canot convince my self let alone him. Just assume a very simple case, a 2-layer structure: one is die and BT; the other die on top of PTFE. Assuming 2 materials perfect adhesion. Cooling down from 100 to 0, assuming stress free @ 100C. Which will have higher stress? which will have higher strain? Can anyone offer some help? Thanks, Yuan Li On Fri, 9 Mar 2001, Zhang Tong Long wrote: > For Cu higher stress basically mean higher strain because it can be > considered as linear elastic material in the temperature range of -65C to > 300C. > > But be cautious about the results from simulation, which can be misleading > sometimes. > > rgds/TL > -----Original Message----- > From: TechNet [mailto:[log in to unmask]]On Behalf Of LI YUAN > Sent: Friday, March 09, 2001 5:57 AM > To: [log in to unmask] > Subject: [TN] Substrate trace crack > > > We were debating PTFE vs BT. Our simulations show that PTFE has less > stress. However, one of my colleagues argued that cu trace failures are > strain dominant failures, hence less stress does not mean better substrate > reliability. I don't know whether he is wrong or right. Please advise. > > Thanks a lot, > > Yuan Li > > ---------------------------------------------------------------------------- > ----- > 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 > ---------------------------------------------------------------------------- > ----- > > > > --------------------------------------------------------------------------------- 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 ---------------------------------------------------------------------------------