More Information: The press cycles are a controlled ramp from room temperature to 340F over approx. 45 minutes, cure for 70 minutes, controlled ramp down to room over approx. 35 minutes. Pressure approx. 50 psi. If it was nickel diffusion would that be approx. even across all pads or can it be highly variable- most pads bond - the customer is only having issues with a few (120 pads in the row - 8 mil pitch) Regards Steve Kelly -----Original Message----- From: TechNet [mailto:[log in to unmask]] On Behalf Of Leo Higgins Sent: Friday, December 12, 2003 1:11 PM To: [log in to unmask] Subject: Re: [TN] Cleaning of Wire Bondable Gold Hello all, Ni movement through Au porosity generally starts as Ni(OH)2, and no diffusion through bulk or Au grain boundaries is involved. The hydroxide is black in appearance. With adequate humidity, the hydroxide will 'grow' out over the Au surface surrounding the void in the Au that exposed the underlying Ni. Over time/temperature the oxide will form from the hydroxide. Ni diffusion through Au thin films does not occur at high rates until well over the 230-235C reflow temp noted below, and Ni diffusion through Au (along GBs as noted below) would not be occuring at any measurable rate at the rigid/flex lamination temperatures associated with the question that initiated this string, but the hydroxide/oxide could be forming in Au pores that exposed Ni. The diffusion of Ni through Au was studied heavily in the mid to late 80s when hermetic sealing of ceramic packages with kovar lids was very common, and Au-Sn eutectic material was used. This eutectic melts at 280C and it is in the approximate 270 - 300C range where Ni diffuses very rapidly through void-free Au. Below 250C it should not be an issue unless soak time is very long. Best regards, Leo -----Original Message----- From: Vladimir Igoshev [mailto:[log in to unmask]] Sent: Friday, December 12, 2003 11:18 AM To: [log in to unmask] Subject: Re: [TN] Cleaning of Wire Bondable Gold Hi Steve, What kind of "surface nickel/diffusion" data are you looking for? I'm a little bit "confused" with diffusion "accelerated" (or promoted) by possible voiding in the gold layer. I think the temperature isn't high enough to have something like surface self-diffusion so, it doesn't look like the presence of pores should affect possible diffusion of Ni through the Au layer. I agree with Joe, that some organic layer may be present on the surface and could cause the problem (let say "develops" over time/temperature exposure). Vladimir Igoshev Research in Motion (519)888-7465, x5283 -----Original Message----- From: Steve Kelly [mailto:[log in to unmask]] Sent: December 12, 2003 11:24 AM To: [log in to unmask] Subject: Re: [TN] Cleaning of Wire Bondable Gold Hi Joe, I have some answers: 1) soldering is normal no-clean - not lead free . We normally re-flow at 230-235 C (sees this temperature for approx. 40-45 seconds) 2) I am in the process of looking for surface nickel/diffusion. Will know later today 3) the components are at one end of the flex - wire bond pads are about 4.5 inches away. 4) I am receiving a lot of opinions about how much gold should be there but in general people are leaning to more - how much more is a good question 5) we also build another part for this same customer that only sees one press cycle after gold and no re-flow - construction is a little different (but gold/nickel/copper is on top of an AP in both cases). To the best of my knowledge they have no issues with this part for over 4 years. Regards Steve Kelly -----Original Message----- From: TechNet [mailto:[log in to unmask]] On Behalf Of Joe Fjelstad Sent: Friday, December 12, 2003 11:07 AM To: [log in to unmask] Subject: Re: [TN] Cleaning of Wire Bondable Gold Hi Steve, Interesting discussion you have brought to the fore and you have gotten some excellent advice on cleaning. It was not stated but I am assuming gold wire bonding based on the thickness and as well assuming that the gold is not selectively plated on the wire bonding pads. My experience from past lives was that 1 micron was normally enough, however, there were not two extra press cycles (with attendant volatilization and deposition of organic materials and a reflow operation that preceded wire bonding). I have worked with folks wherein millions of devices were wire bonded post reflow assembly using aluminum wedge bonding. The gold for such was about 1/5 micron Brian has suggested and it has been seconded that porosity might be in the mix. I am left with a few questions whose answers that might lead me to ask better questions. Is the soldering leadfree? (higher temperatures? volatilized organics? ) Have you looked at the positity/diffusion issue? (i.e. Is Ni really there?) Or is the offending layer organic by analysis? Last (for the moment anyway... ;-) what thickness of gold would be considered pore free? 1.5 microns?, 2.0? 2.1? (I know that there are plating related issues that mitigate any answer) and would that work for all steps in the process? (embrittlement has already been cited as a concern but where is the wall for this process combination?) Gold is expensive but not so expensive as the board. I have had customers in the past that specified 1.5 microns and never had a problem (make that never reported back a problem) We all like a good problem but the real objective is to find a way to make them never show their faces in production. It's pretty boring but very cost effective :-) Good luck, Joe --------------------------------------------------- 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 847-509-9700 ext.5315 ----------------------------------------------------- --------------------------------------------------- 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 847-509-9700 ext.5315 ----------------------------------------------------- --------------------------------------------------- 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 847-509-9700 ext.5315 ----------------------------------------------------- --------------------------------------------------- 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 847-509-9700 ext.5315 ----------------------------------------------------- --------------------------------------------------- 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 847-509-9700 ext.5315 -----------------------------------------------------