Guenter, Do you really believe that TSOPs can be used in an application where the daily temperature swing is 40 C ? Bev Christian Nortel >---------- >From: Guenter Grossmann[SMTP:[log in to unmask]] >Sent: Monday, December 01, 1997 2:57 AM >To: [log in to unmask] >Subject: Re: [TN] TSOP, TQFP reliability > >Hi Sven-Eric > >It is a matter of fact that the solder joints of TSOP's are less reliable >than the ones of packages with high standoff since it is the length of the >leads which absorbs most of the deformation due to the CTE mismatch of >component and PCB. Long leads deform easier than short leads. Additionally >if the leadframes of TSOP's are made of Alloy 42 than the leads are stiff >compared to copper leads. Using copper leads instead of Alloy 42 eases the >problem to a certain extend. > >However, I believe it is important to consider the environment the product >is used in. Namely the temperature swing, the temperature extremes the >temperature gradient and the reliability goal of the solder joints ( As >Werner already mentioned, there is nothing wrong with TSOP's per se ). In >my opinion the reliability of these solder joints has to be estimated for >the application their used in, since even a material combination that is >potentially harmful might lead to a reliability of the solder joints that >is well within the requirements for a given stress. >Let's say one uses TSOP's on FR 4 in an office environment 20- 30deg. C and >the equippment sees a temperature swing of 40deg.C with a ramp of 1 deg. >C/min. When switched on and off once a day. I don't see a point why not >using TSOP's unless the thing has to live 100 years. > >Reliability testing does not always mean to find the evil part in an >assembly corrupting the reliability of the whole equippment but also to >find out whether a technology that is absolutely disastrous for some >applications but has advantages ( price, space ) may be used in an >application with moderate stress. Therefore I think it doesn't make sense >to use data from tests with extreme testconditions to estimate the >reliability for a much less severe application without checking whether the >testconditions are applicable to the real stress. > >Besides that's the work Werner and I are living of so it's got to be >important. > > >Best regards > >Guenter Grossmann >Swiss Federal Institute of Technology >Reliability Laboratory > >############################################################## >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. >For the technical support contact Dmitriy Sklyar at [log in to unmask] or >847-509-9700 ext.311 >############################################################## > ############################################################## 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. For the technical support contact Dmitriy Sklyar at [log in to unmask] or 847-509-9700 ext.311 ##############################################################