Electronics Forum: qfn printing (Page 1 of 6)

QFN84 Solder Printing Issue (QFN with Inner LGA Pad)

Electronics Forum | Mon Dec 04 15:23:31 EST 2017 | kojotssss

A new stencil has been purchased. to be continued.

Solder Paste Type for QFN Printing

Electronics Forum | Wed Aug 25 15:02:04 EDT 2010 | spitkis2

I am printing solder paste directly onto a QFN device. Any recommendations on the type of solder paste to use? Namely I am concerned about getting a good release from the stencil. Thanks

Solder Paste Type for QFN Printing

Electronics Forum | Wed Aug 25 15:24:07 EDT 2010 | mikesewell

Whatever you would normally use to print that size part on the pcb should work. Same aspect ratio rules apply for release.

Solder Paste Type for QFN Printing

Electronics Forum | Tue Sep 14 13:43:25 EDT 2010 | rayguide

Use No-Clean fine-particle solder paste from Kester. http://www.suite101.com/content/solder-paste-and-its-application-in-smt-a249514

QFN84 Solder Printing Issue (QFN with Inner LGA Pad)

Electronics Forum | Sat Nov 11 11:11:28 EST 2017 | spoiltforchoice

One suggestion I have seen for packages like this is to have the device balled first.

QFN84 Solder Printing Issue (QFN with Inner LGA Pad)

Electronics Forum | Fri Dec 01 13:30:08 EST 2017 | kojotssss

Stencil thickness is 4 mil. Via's are plugging from bottom. Gas may be developed under the component? Take Reflow Ovens Thermal Profiling changes? In your opinion?

QFN84 Solder Printing Issue (QFN with Inner LGA Pad)

Electronics Forum | Fri Dec 01 14:11:24 EST 2017 | kojotssss

EMIL, The first stencil was with 4 squares. then there was a worse percentage. Changed to the circles. Is better, but still not perfect. Stencil thickness did not change. I added 2 types of stencil openings. Pictures of watch:

QFN84 Solder Printing Issue (QFN with Inner LGA Pad)

Electronics Forum | Fri Dec 01 14:50:30 EST 2017 | kojotssss

How about step down in the middle of thermo pad? I mean 0.075mm This can help?

QFN84 Solder Printing Issue (QFN with Inner LGA Pad)

Electronics Forum | Fri Dec 01 14:55:51 EST 2017 | kojotssss

Rework said that with hot air gun, heated the solder paste comes out of the middle part out to the side terminals and soldering extending beyond is perfect.

QFN84 Solder Printing Issue (QFN with Inner LGA Pad)

Electronics Forum | Fri Dec 01 15:22:46 EST 2017 | kojotssss

Recommended land and solder pattern says: VIA wall plating, via holes should be tented with solder mask on the backside and filled with solder. Solutions at this moment ? Thanks for all :)

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