Immersion silver is self limiting process. Can you get thicker layer as you required? How thick is the layer your vendor provide? what is the uniformity? Any pin holes or exposed nickel? we did some eval years ago (5 or 6 years ago I think) and didn't pass the initial pull test requirement and aging requirement. The technology may be different now.... good luck. jk by the way, I use 9g as minimum. the standard deviation is the one kill the thing (non-uniformity). -----Original Message----- From: TechNet [mailto:[log in to unmask]] On Behalf Of Creswick, Steven Sent: Wednesday, July 30, 2003 12:47 PM To: [log in to unmask] Subject: Re: [TN] Gold wire bond on silver finishings David, I can not say that I have bonded to immersion silver (yet), but have begun to consider it. Getting down to only 6 microinches sounds a little questionable - especially if the boards have experienced reflow, and have possibly sat around prior to die attach (another bake/cure) and wire bonding. Are you sure you are getting 6 microinches?? At 6, you might just as well ask for a "flash" and keep your fingers and toes crossed that everything will work - and that you did not get 2, 3 , maybe 4 microinches instead. With thin gold, I would expect to see lifted wedges at the bonder (no sticks), and low second bond pull strengths at wire pull. I would expect virgin boards to give better results than those boards subjected to any elevated temperatures and/or staging times prior to wire bonding. I begin to get really nervous if my 1 mil wires began to have bond failures at <6-9 grams (depending upon the tensile strength of the wire). Wire breaks I can sleep with, but the bond lifts scare me! Lastly, you have not indicated whether this is the "first time" you have bonded to these boards (and may still be seeking the optimium bond schedule and capillary face style/angle), or you have been running them all along, and just now have begun to have a problem. Is your laminate capable of handling the temperature at which you are bonding? The "fifth degree", not intended. :-) Steven Creswick Gentex Corporation - A Smarter Vision -----Original Message----- From: davidyeh [mailto:[log in to unmask]] Sent: Wednesday, July 30, 2003 10:22 PM To: [log in to unmask] Subject: [TN] Gold wire bond on silver finishings Hi, Can anyone share his experience on gold ball bonding on COB with immersion silver finishings. What sort of silver thickness to ensure a good bonding strength of min 3.5 gf? We are using a 1 mil thick gold wire on a 6 to 20 microinch silver thickness and encountered difficulty in achieving the min bonding strength in wire pull. Thanks for all inputs. Best regards, David. --------------------------------------------------- Technet Mail List provided as a free 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/html/forum.htm for additional information, or contact Keach Sasamori at [log in to unmask] or 847-509-9700 ext.5315 ----------------------------------------------------- --------------------------------------------------- Technet Mail List provided as a free 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/html/forum.htm for additional information, or contact Keach Sasamori at [log in to unmask] or 847-509-9700 ext.5315 ----------------------------------------------------- --------------------------------------------------- Technet Mail List provided as a free 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/html/forum.htm for additional information, or contact Keach Sasamori at [log in to unmask] or 847-509-9700 ext.5315 -----------------------------------------------------