Stephané Menard asked: >I have a question regarding the well known problem of whiskers generation on >leadframes. > >With the concept of lead free deposit and the investigation of several >alternatives (Sn-Bi, Sn-Ag, Pure Tin, etc..) to Tin-Lead, we need to study >the risk of generation of whiskers with those substitutes. >It is generally agreed that Tin alloys (even at low percentage in the other >metal) are not prone to this problem whereas pure Tin deposits are. > >However, does anybody have a recognized method (electrochemical, physical, >etc...) which could help in predicting the apparition, or not, of this >problem (besides the standard aging test which sometimes can be quite >doubtful !) ? > >I am looking forward to your answers and comments. Michael Carano offered an interesting reply which concurs with my experience, and also: There is a method in which the electroplated coating is applied to thin coupons which may be measured post plating for mechanical strain. The concept is that whisker growth rate is a function of stress resulting from the exact manner of the coating growth. Plating electrochemistry which imparts less stress is also known to be more stable in regard to whiskers. Sorry, I don't remember the source of these coupons, but check Metal Finishing magazine (they used to have a website). Plating coupons which have right angle minimum radius bends in a dry cabinet at 120-150 degrees C will accelerate the formation of whiskers visible with 10X magnification into the range of a few days. They seem to form first on the outer bend radii. regards, Jerry Cupples Interphase Corporation Dallas, TX USA http://www.iphase.com ############################################################## 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 ##############################################################