Guenter, Here is my two cents (2/100 euro) on part of your discussion. I worked for a thick film contract house for a while and we always used solder with some silver in it to slow down the diffusion process (leaching) of the thick film. The 62/36/2 alloy worked great. We also used a 95/5 alloy that I believe is 96.5 wt.% Sn and 3.5 wt.% silver. This had a melting point of 221 degrees centigrade. It worked quite well in production as long as the surface mount components could withstand a higher peak reflow temp of around 250 centigrade. There were two designers that had been with the company for 20 or 30 years and when I asked them why they would spec out one alloy and why the other alloy, the reply was always that the 95/5 alloy was 'too brittle' and could not withstand thermal cycle. It seems that everything gets thermocycle, so I think it was the range or number of thermocycles that the product had to withstand that was important in determining which solder alloy could or could not be used. Regards Wade Oberle [log in to unmask] P.S. Steve and the guys, keep up the stories. I'm compiling a book of bed-time stories for children of technoheads (GRIN). -----Original Message----- From: Guenter Grossmann [SMTP:[log in to unmask]] Sent: Tuesday, February 02, 1999 6:56 AM To: [log in to unmask] Subject: [TN] Lead removal again Hi Ed The question is about alternatives to what we are talking. 1) Alternatives to HAL 2) Alternatives to Tin/Lead solder And combinations of both Now, since Bob asked me what pad surfaces I tested let me begin with these: I am sure that a lot of new surfaces are around. OSP's, NiAu, Omicron, Alphalevel are about the ones I know of ( hey Bob since you are reading this too, that might be the slot for your 2 cents ). We did test OSP ( don't want to mention a brand name), NiAu ( but that's 5 years ago and the Au thickness was not very well controlled ), galvanic tin and solid solder deposition ( SIPAD ). The test we run was -20/100 deg. C with a gradient of 2 deg C /minute and dwell times of 30 minutes. We removed the specimen from the test chamber after 4000 cycles and compared the crack length in the solder joints of some components with those on HAL. OSP's and NiAu showed a higher average crack length than HAL, Sipad or tin. But again, these data are not suitable for a reliability prediction since they don't allow it to make a statement about the evolution of the damage. Alternatives to Tin lead solder many too. And also lots of problems are there , as Oxonfenuk ( sorry fella didn't get your Christian name on the mail ) pointed out. Just imagine all the world would start to solder with any Indium solder. I'm sure the world recourses wouldn't last long. There are Tin-Copper , Tin-Silver binary alloys but they all tend to have a high liquidus temperature. So ternary alloys are used ( Tin/Copper/Silver, Tin/Silver/Bismuth etc.) to lower the melting temperature. I have no data in hand but you see, one big advantage of Tin/Lead solder is its ductility which allows it to combine materials with high differences of the CTE. Maybe Bob Willis or Collin Lea of ITRI ( are you on the Net Collin?) could give some contributions. Principally there are now problems to be expected with the use of ternary alloys ( Sn62Pb36Ag2 is a ternary alloy too ). I believe that alloys on tin/copper or tin/silver base can meet the demand of the world market. I don't know whether anyone made thermal cycling tests with new alloys. I mean thermal cycles not thermal shock, nor do I know who made research on the deformation/degradation behaviour of these alloys. I think the fluxes are not a big problem. What I see so far, tin will be the main content of all lead-free alloys. And all the surfaces I saw so far work well with fluxes used presently. Best regards Guenter ################################################################ TechNet E-Mail Forum 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 To unsubscribe: SIGNOFF TechNet ################################################################ Please visit IPC's web site (http://www.ipc.org) "On-Line Services" section for additional information. For technical support contact Hugo Scaramuzza at [log in to unmask] or 847-509-9700 ext.312 ################################################################ ################################################################ TechNet E-Mail Forum 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's web site (http://www.ipc.org) "On-Line Services" section for additional information. For technical support contact Hugo Scaramuzza at [log in to unmask] or 847-509-9700 ext.312 ################################################################