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TQFN Solder Issues (56 contact) ZF

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#60147

TQFN Solder Issues (56 contact) ZF | 20 October, 2009

Having some issues with 56 contact TQFN. This is low-run prototype situation so no second chances - unfortunately.

Part is 5mm X 11mm with .30X .63 perimeter lands and 2.5 X 8.5 thermal pad in center.

Issues noted are intermittency at test (basically a power up situation)Component and process are pb free with peak of approx 250 C. There is evidence of wetting, although also appears parts are not completely parallel with board surface as well.

1) is there 'trick' to designing stencil to facilitate flatness and optimum solder connection on all leads?

2) I was told by part mfg to reach peak of 360-380C -- This sounds insane to me - any comments?

3) Any placement tricks (z-adjustment etc...) that would give best results?

We have been suffering through rework on our current run, and will likely see next generation in several weeks. Any and all input is appreciated.

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#60154

TQFN Solder Issues (56 contact) ZF | 21 October, 2009

Make sure the ground pad is reduced on the stencil and window paned. The solder on the thermal pad can lift the part up, especially if it traps gas.

360-380C does sound insane. I would believe a manufacturer saying 360-380F before I could believe 360-380C.

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#60158

TQFN Solder Issues (56 contact) ZF | 22 October, 2009

To find suggestions like: "Go 1:1 on leads and 50% reduction on the body pad. Works every time no matter what QFN," search the fine SMTnet Archives.

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#60166

TQFN Solder Issues (56 contact) ZF | 23 October, 2009

use electropolish 5 mils stencil & bonetype aperture

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#60173

TQFN Solder Issues (56 contact) ZF | 23 October, 2009

FOR YOUR NEXT RUN CONTACT STEVE @ USA STENCILS INC, HE WILL MAKE ONE SAMPLE FOR YOU - THEIR TEAM HAVE SOLID EXPERIENCE IN STENCIL DESIGN ESPECIALLY PCB WITH CRITICAL COMPONENT. HIS EMAIL IS STEVE@USASTENCILS.COM

GOOD LUCK!

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#60174

TQFN Solder Issues (56 contact) ZF | 23 October, 2009

Check that you are following the moisture sensitivity requirements for the part. I've seen the part swell underneath. You can contact me at wenroth@reconsales.com for more information. I am an 'ol reflow guy from the CM world. Wes

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