Hi, Gregg We use a contract manufacturer who has a really good process for adding compliant S and C leads to QFNs using a process that does not subject the components to heat. They do really good work for us and it very effectively fixes the problem. We inspect 100% and then X-ray the parts when they send them back to us, and we have yet to find a bad solder joint on the components. Check out www.analog-tech.com. -----Original Message----- From: TechNet [mailto:[log in to unmask]] On Behalf Of Temkin, Gregg Sent: Wednesday, July 30, 2008 4:27 PM To: [log in to unmask] Subject: [TN] Use of QFN devices in high reliability applications Our team is working on several new electronic devices whose application is primary, flight critical hardware for commercial aircraft. Our initial component selection includes many QFN packaged devices (leadless, bottom side termination only) which will be mounted on .063" FR4 boards using SN63. The devices range from 20 to 44 terminations. From studies that are available on the web, a picture has emerged that QFN packages have reduced long term solder joint reliability when compared with leaded or some of ball grid array devices. Board thickness, flexing and whether the device has a central solderable heat sink seem to have a significant affect on reliability. Problem is there are no absolute numbers, so for critical applications it seems that thorough testing is required. We'd rather not wait until the end of a lengthy test regimen to find we've gone down the wrong path. Is there newer information abbailable? Two of the studies stated that further testing was being performed to support the reliability requirements for aerospace and other high-rel applications however I cannot find any updated information on the web. We have decided to replace several of the QFN's with leaded devices, however there are no direct crosses for 3 of the devices. One of them will require a number of components to create the same function; possibly an additional circuit card. Is anyone aware of information or recommendations that would be useful for our assessment? Is there any specific information that would drive us to use or not use them? Thanks for your help Gregg --------------------------------------------------- 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 -----------------------------------------------------