It depends on whether it is actually being used for thermal transfer or electrical grounding. -----Original Message----- From: TechNet [mailto:[log in to unmask]] On Behalf Of Rex Waygood Sent: Tuesday, July 22, 2008 2:12 AM To: [log in to unmask] Subject: Re: [TN] Solder balls Picking up on John's point when you have sorted out (or decided to ignore) the solder balls, your thermal pad is only soldered over about 33% of its area. Many of these devices recommend a minimum of 50%. To me that would be a more serious problem. Rex Rex Waygood Technical Manager PartnerTech Poole Ltd Benson Road Poole Dorset BH17 0RY United Kingdom Tel: +44 (0)1202 674333 Fax: +44 (0)1202 678028 DDI: +44 (0)1202 338222 Mob: +44 (0)7887 997403 [log in to unmask] www.PartnerTech.co.uk -----Original Message----- From: TechNet [mailto:[log in to unmask]] On Behalf Of John Burke Sent: 21 July 2008 21:10 To: [log in to unmask] Subject: Re: [TN] Solder balls Genny, Looks to me that the via holes for the thermal management have sucked all of the solder from under the QFN leaving at best 50% of the thermal pad cross section connected? - this could be an issue. However - back to the solder balls. I have noticed a couple of things about this assembly. The first and most obvious is of course the solder ball issue. More telling is actually the extent of the voiding in the joints, together thet might be pointing to a profiling issue? I also noticed that there is very little solder build up on what would be a toe fillet in a QFP on the right and top side of the package (I also notice also that the two outside joints at the top are showing heavy metal loading at the toe , as well as the top and bottom joints on the right side - although less so - is this a touch up with a soldering iron?) this leads me to suspect that the QFN is probably not co-planar with the board but has the top right corner raised somewhat from the board, so the package may have had some rocking movement while being reflowed as the solder melted and moved around? Just my thoughts, fortunately you are able to actually look at it!! John John Burke (408) 515 4992 -----Original Message----- From: TechNet [mailto:[log in to unmask]] On Behalf Of Genny Gibbard Sent: Monday, July 21, 2008 11:56 AM To: [log in to unmask] Subject: Re: [TN] Solder balls The solder balls are near the arrows. Faint grey round objects. This device does have a heat slug, and there are plated thru holes under it for heat transfer. And yes, our X-ray does allow oblique viewing. What are you suggesting we look for? ------------------------------------------------------------------------ ------- The information contained within this e-mail and any attachments contained therein may be confidential and/or legally privileged and is for the use of the intended recipient only. If you are not the intended recipient please delete it from your system and notify the sender by return e-mail. The content of this e-mail may not be copied or disclosed to any third parties without prior permission from the sender. E-mail is susceptible to data corruption, interception, tampering and viruses. We do not accept any liability for any such incidents or any consequences thereof. --------------------------------------------------- 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 -----------------------------------------------------