You and Werner make excellent points. For those same reasons, I have forbidden the use of these parts for many years. If they must be used, I require special mounting instructions and a disclaimer on any long-term reliability commitments. Dewey -----Original Message----- From: TechNet [mailto:[log in to unmask]] On Behalf Of JaMi Smith Sent: Tuesday, November 07, 2006 2:31 PM To: [log in to unmask] Subject: Re: [TN] Gold Embrittlement Werner, Looking strictly at the top pictures, it can be seen that the leads are bent slightly downwards, and only contact the PCB traces at the ends. Additionally, the ground leads are pathetically short, and do not even appear to be in full contact with the traces across their width. In this specific instance, trying to argue thermal mismatch between the base material of the leads and the copper of the PCB trace doesn't even appear to be applicable, due to the minimal contact. Respecting any thermal mismatch of your Alloy 42 and Cu, we have been building RF Amplifiers and other curcuits for years, even in spacecraft, without having the problems you espouse, especially to the extent that you imply, and once again I would argue that the ground leads shown in the pictures are way way too short, and I might add that cutting them at an angle does absolutely nothing for them except make for much less thermal transfer and electrical transfer. Having the lead flat on the copper trace, is not only an electrical issue (current transfer), but also an RF issue (impedance mismatch), and while I can accept that the leads should not be excessively long, neither should they be excessively short. Now as for the gold embrittlement itself, I have a few questions. Does the length of time that the joint is held at solder flow/reflow temperature allow for more of the gold to go into solution with the solder? Does the amount of solder that is added to the solder joint allow for more of the gold to go into solution with the solder? What does gold embrittlement look like, or does it even happen, and if so to what extent, with the new solders that are being used as we go 'lead free'? Are there any specific 'lead free' solders that are better in avoiding gold embrittlement that the others, and why? JaMi ----- Original Message ----- From: "Werner Engelmaier" <[log in to unmask]> To: <[log in to unmask]> Sent: Tuesday, November 07, 2006 12:44 PM Subject: Re: [TN] Gold Embrittlement > Hi 'JaMi,' > While I agree with you about the appearance of these solder joints, I cannot > agree with you regarding what would happen in the absence of Au. > If you make the leads and their attachment area larger [which from electrical > and thermal conductivity considerations is advantageous], you run into > another problem. > For this type of devices, the lead material is typically Alloy 42, not Cu. > Thus, large soldered areas will suffer from local expansion mismatches in > combination with the global expansion mismatches. > In any case, the excessive amount of Au does not help. > > Werner > > --------------------------------------------------- > 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 ----------------------------------------------------- --------------------------------------------------- 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 -----------------------------------------------------