Electronics Forum | Wed Nov 14 01:00:20 EST 2007 | reypal
recently, we also have problem with QFN around 3% defect related to soldering. from the cross section it turns out to be solder crack. it could be the paste volume on the center pad is too much causing QFN to float that eventually will cause crack on
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?
Electronics Forum | Fri Jul 19 13:09:55 EDT 2019 | edhare
Hi, Are you referring to the condition illustrated here? ... https://www.semlab.com/qfn-solder-fillets In this case, the solder was wicked down an attached un-filled PTH via. Ed Hare SEM Lab, Inc.
Electronics Forum | Fri Dec 01 13:55:44 EST 2017 | emeto
Brikainis, it looks like these vias are not plated and closed. I would say that thickness of your paste is lifting the part. Are you willing to try another stencil with ground pad apertures matching the via holes? It is probably worth trying. Anothe
Electronics Forum | Fri Nov 09 10:37:38 EST 2007 | devajj
We have started using QFN packages in large volume and are having problems with no-solders. We are using 6mil stencil with 1x1 paste print to pad. These also have thermal pads with thru vias that we reduce the stencil aperture by 1/4. Board also ha
Electronics Forum | Sat Nov 10 23:46:36 EST 2007 | mika
BTW, The surrounded QFN fine pitch terminals should have the normal aperture reduction of 7 % in case of RoHS Senju solder paste. This works for our Telecom customer. The vias in the ground pad will be somewhat filled with solder and makes it diffi
Electronics Forum | Thu Jun 10 06:15:45 EDT 2010 | muarty
We currently have a project requiring us to place multiple QFN devices (of various sizes). The pick an place is not a problem at all, where we are seeing 'problems' is that 3 of the devices are being place on locations where the ground pad have plugg
Electronics Forum | Sat Dec 02 10:23:47 EST 2017 | tomh
Have you ever heard of "Solder Mask Defined Thermal Pads"? I wrote a short blurb on this here - https://www.pcblibraries.com/forum/ipc7093a-btc-qfn-solder-mask-defined-thermal-pad_topic2154.html This technology saves fabrication costs by not havi
Electronics Forum | Sat May 18 10:21:09 EDT 2013 | davef
isd.jww: Comments are: * Current thinking has flux volatiles being the major contributor to voiding, not scavanging by via * I have no reason to think that 0.3mm via won't gladly accept solder. Plug them, if that's a concern. * If your concern is ina
Electronics Forum | Wed May 22 19:47:30 EDT 2013 | anvil1021
Also, I was just thinking that most of the large companies we work with do not consider via drain an actual void. As a matter of fact our high dollar super fantastic Xray system actually has a switch to turn off the vias during void detection so that
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