Hi Bob, Have yet to see any QFN reliability data according to IPC-9701----I'm waiting like you. Werner -----Original Message----- From: Robert Kondner <[log in to unmask]> To: 'TechNet E-Mail Forum' <[log in to unmask]>; 'Werner Engelmaier' <[log in to unmask]> Sent: Fri, May 21, 2010 9:02 am Subject: RE: [TN] Solder joint height Werner, The other day I saw the reference to any solder joint of less than 50um being composed mostly of intermetallics I almost fell from my chair. I guess I should have thought that one out but this realization made me wonder about QFN and leadless package reliability. Can you point me to any data on reliability of leadless packages compared to Gull Wing? Thanks, Bob Kondner -----Original Message----- From: TechNet [mailto:[log in to unmask]] On Behalf Of Werner Engelmaier Sent: Thursday, May 20, 2010 6:30 PM To: [log in to unmask] Subject: Re: [TN] Solder joint height Hy Wayne, Well, those QFNs and LCCs are deja vu all over again. With LLCCCs we had an obvious huge CTE-mismatch between ceramic and FR-4, with QFNs it is not so obvious since the CTE-mismatch comes from the die--so die size and die attach are a big part of the equation. So it depends on the stresses developed by the thermal expansion mismatch from the product of DNPxDCTExDT whether the thin SJs will survive long enough for reliability. Werner -----Original Message----- From: Thayer, Wayne - IIW <[log in to unmask]> To: [log in to unmask] Sent: Thu, May 20, 2010 4:17 pm Subject: [TN] Solder joint height Should there be a spec for minimum solder joint height for leadless components? An old paper from Werner (mid 90's, I believe) popped up on the Internet when I queried this, and Werner has a statement in it that joints less than about 50 microns thick are basically all intermetallics, but that is not necessarily a bad thing since the intermetallics are stronger than the solder (but more brittle). I figured since we often try to get additional height for BGA joints to improve reliability, we should be concerned about QFNs and LCCs. I grabbed a 1.5mil (37 micron) tungsten rod out of our cleanroom (used for clearing clogged wirebond capillaries)and started seeing if I could get that under my leadless components. Couldn't get it under any of them, likewise with the QFNs. Checked Technet archives and didn't see an obvious thread, but maybe I didn't have the correct search parameters--if you just enter "height" you get a couple of thousand hits. Wayne Thayer This e-mail and any files transmitted with it may be proprietary and are intended solely for the use of the individual or entity to whom they are addressed. If you have received this e-mail in error please notify the sender. Please note that any views or opinions presented in this e-mail are solely those of the author and do not necessarily represent those of ITT Corporation. 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