Larry: First of all their is a ton of information on this topic in the IPC TechNet archives, take a look at it. Regarding your questions, the short answer is; it depends. There are many different OSP coatings available that produce varying performance based on the coating and it's application by the board fabricator. Environmental storage conditions will effect it. The thermal cycle time, temperature, type of oven etc will effect it. The type of flux you are using will effect it. etc etc etc... I will speak based only on what is seen for the type of OSP coating and assembly processes we use. You need to qualify the coating type and processes together. To answer your questions: 1. We have boards up to a year+ in inventory that do not have soldering problems. These are stacked together wrapped in plastic. Conditions are 68-78F, 35-55% RH. The OSP coatings are part of the Enthone 106 family. 2.The heat cycles break down the coatings protective properties that prevent oxidation of the underlying copper. Both time and temperature destroy the coating, however higher temps(>200F)are more detrimental than just time. The more thermal cycles the board sees the more oxidized the copper becomes, making it harder to activate and solder to. Our worst case process; Kester No-Clean paste with up to two reflow passes and a glue cure, all using forced air convection ovens. This is followed by wavesolder with an Alpha WSF. We do not have solderability issues but that's about as far as we can push the envelope. Any additional thermal exposure affects solderability. 3. We have gone up to a month between reflow steps and up to a month between reflow and wavesolder. Obviously you want to complete soldering operations as quickly as possible. Our goal is usually 2-3 days max, unless something unforeseen comes up. Also note that we are using a WSF at wavesolder. Hope this helps. Regards Michael Barmuta Staff Engineer Fluke Corp. Everett WA 425-446-6076 -----Original Message----- From: Larry Koens [mailto:[log in to unmask]] Sent: Friday, July 19, 2002 11:57 AM To: [log in to unmask] Subject: [TN] OSP Technet, I would like to have Technet clarify some questions that I have on OSP boards. I got into a discussion with some other of my fellow Engineers today about OSP and we had different opinions and ideas on several topics related to this. 1. What is the expected stockroom shelf life of board? The boards would sitting on a shelf, unwrapped and stacked one on top of the other. 2. What happens to the coating after each heat cycle? Does the heat dissolve the coating or does it make it just stronger and such more difficult for the flux to penetrate the coating? 3. Is there any time frame that you would try to complete the entire assembly in? Would the assembly be more difficult to solder if there was days between the reflow and wave time frames then if they were all completed within hours? thanks in advance -Larry Koens- ---------------------------------------------------------------------------- ----- 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 ---------------------------------------------------------------------------------