Hi, Edward As was proven in a lawsuit last week in which I was the expert witness, the general underfill process itself is in the public domain, but a certain amount of process development is required to get to the right material, the optimum cure schedule, the optimum dispense rate and board temperature/material temperature when dispensed, etc., to ensure that you have the best possible process for your particular application or product. You are going down the right path in developing a process, which is to first gather as much information as you can. The second is to secure samples and develop a plan for the process. The third step is trying the different materials and carrying out the plan and testing to get results (data). Once you have optimized and qualified the process you document it. Some applications are much more difficult than others. The results are manifest during qualification as shown by the increase in cycles before failure (or lack thereof). So when you are developing your underfill process you want to qualify and validate the results with some type of thermal cycling, using the guidelines in Werner's article. Your finished and documented process IS proprietary material (intellectual property), and should be protected. -----Original Message----- From: TechNet [mailto:[log in to unmask]] On Behalf Of Whittaker, Dewey (EHCOE) Sent: Thursday, June 04, 2009 10:00 AM To: [log in to unmask] Subject: Re: [TN] When not to underfill Guidelines in of themselves are merely the under fill of the great belly of knowledge that is Technet. Dewey -----Original Message----- From: TechNet [mailto:[log in to unmask]] On Behalf Of Edward Rios Sent: Thursday, June 04, 2009 7:50 AM To: [log in to unmask] Subject: Re: [TN] When not to underfill Thanks Werner. Yes, your column was very helpful. Sounds like my question may be a bit naive and that I am trying to simplify things too much. I was searching for an IPC guideline or to at least start a discussion on the subject, but maybe this is a proprietary area. Fellow TechNetters: is that the case? Have a great day, Ed Werner Engelmaier /* wrote: > Hi Ed, > Underfill makes solder attachments sufficiently reliable in cases where without it solder joint failures would occur prematurely for the application in question. As work by Motorola [see my reliability column Engelmaier, W., "Reliability Improvement with Underfill," Global SMT & Packaging, Vol. 6, No. 3, March 2006, pp. 66-67] has shown, not all underfills are of equal benefit and that increases of up to 6x are achievable in praxis. > If the reliability without the underfill is sufficient-because of small component size, high solder joint stand-off, built-in component compliancy [Tessera patents], small CTE-mismatch, small delta-T, then there is no need for underfills. > Werner > > > > > > > > -----Original Message----- > From: Edward Rios <[log in to unmask]> > To: [log in to unmask] > Sent: Wed, 3 Jun 2009 5:45 pm > Subject: [TN] When not to underfill > > > > > > > > > > Hi TechNet, > > > OK I'll admit it, I'm fairly new to the field of solder joint > reliability. ;) Therefore, the recent thread about underfill inspection > criteria prompted me to do additional reading on the subject. It seems > like there is consensus on the positive effect of underfilling on BGA > solder joint reliability. On the other hand, are there cases where > underfill doesn't have a significant impact? Maybe in smaller BGA > components? > > > Thanks, > > > Ed Rios > > > --------------------------------------------------- > > Technet Mail List provided as a service by IPC using LISTSERV 15.0 > > To unsubscri > be, 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 847-615-7100 ext.2815 > > ----------------------------------------------------- > > > > > > > --------------------------------------------------- > Technet Mail List provided as a service by IPC using LISTSERV 15.0 > 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 847-615-7100 ext.2815 > ----------------------------------------------------- > > --------------------------------------------------- Technet Mail List provided as a service by IPC using LISTSERV 15.0 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 847-615-7100 ext.2815 ----------------------------------------------------- --------------------------------------------------- Technet Mail List provided as a service by IPC using LISTSERV 15.0 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 847-615-7100 ext.2815 ----------------------------------------------------- --------------------------------------------------- Technet Mail List provided as a service by IPC using LISTSERV 15.0 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 847-615-7100 ext.2815 -----------------------------------------------------