HI BRETON, First, your quest to find information on this subject probably exists, and no doubt is the result of numerous stress analyses and DOE's performed by countless individuals for their specific application, but quite frankly, I have not seen this type of data openly published in any industry technical literature during my career. If it has been published I would appreciate knowing how to obtain it as well. Nevertheless, as you probably already know, the strain values that you are looking for with respect to the limits SMT components can withstand during temperature exposures is in fact, the result of the components material and the components mounting media's materials mechanical properties, their physical geometry's and their TCE's in conjunction with the temperature extremes which these elements are exposed to with respect to the soldering/temperature profile being used. Also, it has been my experience that when components with these type flaws go undetected (some components do get through environmental screening processes) during the manufacturing and testing phases of a product the historical evidence has shown that the high strain/stress results can have very serious implications on the reliability of these type components when allowed to be delivered and exposed to field natural and induced environmental conditions. Secondly, I assume that you are mostly concerned with the strain and stress values associated with SMT passive "leadless" type components, because personally I have not seen a cracking problem with "leaded" type active or passive components such as QFP's, Hybrids, discrete and etc. Unfortunately because my experience up to this point-in-time with BGA's has been very limited, I can't offer any constructive comments with respect to this issue for these types of component styles. Perhaps some other Technetters can respond on-line regarding their experience with types of component styles. Perhaps some other TechNetters can respond on-line regarding their experience with this type of component style? In essence, when a component has both ends fixed, such as SMT passive components (chip capacitors, resistors, etc.) soldered to a PWB and/or some mounting media, the elongation taking place during the temperature changes will cause the component to bow due to the solidification of the soldering operation. Moreover, depending upon the relative magnitudes of the TCE's of the component and its mounting media, the force generated will either be compressive or tensile in nature. The stress is normally determined using HOOKE's LAW, and my personal experience has shown that when the stress calculated exceeds the allowable tensile and/or compressive strength properties of the component's body material, catastrophic fracturing/cracking has the potential to occur when the physical size of the component's body is greater than 250-mils square, and exposed to the normal soldering operations. However, my experience has also shown that using HOOKE's LAW to calculate the stress usually results in stress values that are often higher than those observed empirically. This is true primarily because there are several factors which can contribute to the reduction in the stress that are either often overlooked and/or not accounted for correctly in performing the analysis, and consequently, this is the reason why good engineering practices dictate the performance of verification testing to prove or disprove the components reliability issue. In summary, since this topic is one of great depth, I suggest that you may want to consider contacting an expert in this field like Mr. Werner Engelmaier (904-437-8747). Or better still, regarding this subject, perhaps Mr. Engelmaier would be receptive to sharing his comments on-line with us fellow TechNetters? Nevertheless, although I don't know how much help, if any, I can be, please don't hesitate to contact me off-line. Best regards, Dan Fazioli Engineering Technical Mgr. Smiths Industries Aerospace, IMS Clearwater, Florida 33762 e-mail: [log in to unmask] ph: 727-532-6333 ############################################################## TechNet Mail List provided as a free service by IPC using LISTSERV 1.8c ############################################################## To subscribe/unsubscribe, send a message to [log in to unmask] with following text in the body: To subscribe: SUBSCRIBE TECHNET <your full name> To unsubscribe: SIGNOFF TECHNET ############################################################## Please visit IPC web site (http://www.ipc.org/html/forum.htm) for additional information. If you need assistance - contact Gayatri Sardeshpande at [log in to unmask] or 847-509-9700 ext.5365 ##############################################################