Thermal stress of PWB coupons is different than what I'm referring to. The thermal shock I'm talking about is typically performed in an environmental chamber (or chambers). Basically, you have two chambers, one ant a low temperature, the other at a high temperature. After a predetermined time in one chamber, the test sample is removed and placed into the other. The temperature change rate (ramp) is quite high (fast). Thermal cycling, on the other hand, usually takes place in a programmable chamber with pre-programmed high and low temperature extremes and a controlled ramp rate like 5 degrees C per minute. Hope this clarifies things. Jim Marsico Senior Engineer Production Engineering EDO Electronics Systems Group [log in to unmask] <mailto:[log in to unmask]> 631-595-5879 -----Original Message----- From: Paulus, Jim [SMTP:[log in to unmask]] Sent: Wednesday, June 23, 2004 9:37 AM To: [log in to unmask] Subject: Re: [TN] Antw: [TN] Shock vs. Cycling What is the difference between "thermal shock" and "thermal stress", which is generally a coupon that is floated or dipped into solder for 10 or 20 secs at 500 or 550F? Thanks, Jim Paulus at Itron: 507-837-4326 at office: 608-787-0817 -----Original Message----- From: Guenter Grossmann [mailto:[log in to unmask]] Sent: Wednesday, June 23, 2004 2:28 AM To: [log in to unmask] Subject: [TN] Antw: [TN] Shock vs. Cycling James The results you will achieve will be totally different and specific to the test. In thermal shock deformation and degradation mechanisms will be activated that are irrelevant in thermal cycling and vice versa. - Degradation in solder joints depends on the strain rate - The degradation path in solder joints can be influenced by the stress applied. And, the higher the strain rate the higher the stress. - Thermal shock can lead to the destruction of the components something that will not occur in thermal cycling - Due to thermal shock the substrate will bend or warp and bring in additional stress into the component and the joints not occurring in thermal cycling If your application includes thermal shock you must test the specimen accordingly if the stress is thermal cycling, thermal cycling is the test you have to do otherwise it is impossible to make any connection between the test results and the real application. I do have even doubts about the validity of comparative tests done with thermal shock if no thermal shock occurs in the application (see above). Best regards Guenter EMPA Swiss Federal Laboratories for Materials Testing and Research Centre for Reliability Guenter Grossmann, Senior Engineer 8600 Duebendorf Switzerland Phone: xx41 1 823 4279 Fax : xx41 1 823 4054 mail: [log in to unmask] --------------------------------------------------- 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 847-509-9700 ext.5315 ----------------------------------------------------- This message was scanned for viruses!! --------------------------------------------------- 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 847-509-9700 ext.5315 ----------------------------------------------------- --------------------------------------------------- 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 847-509-9700 ext.5315 -----------------------------------------------------