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 | Mon Apr 04 12:16:32 EDT 2005 | DasonC
We make a custom mini stencil to print the paste onto the QFN and flip over to load on the rework station. The mini-stencil was designed for SRT to pick up the QFN. Check BeamOn (stencil house) for detail. Good luck
Electronics Forum | Mon Nov 13 09:40:01 EST 2017 | philc
Just a few thoughts, as we use similar quite frequently without issues. Ensure correct support when pasting the board, especially if it is thin. Correct support when placing the part. Is it placed correctly by the machine? If it is very slightly of
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 | Fri Dec 01 12:56:33 EST 2017 | emeto
It seems that it will work with 5 mil stencil. To be safe use 4 mil if the rest of the design allows it. 10x20mil apertures for both rows. If you have bigger footprint in the corners, make bigger apertures there. For the ground plane, I would use ver
Electronics Forum | Mon Dec 04 08:43:39 EST 2017 | bandjwet
If you are looking to rework (after all of the previous suggestions are taken and tried....you have some solid ones in there). When a device like this is placed and is hard to get to we use the 7721 bumping process using a controlled heat source (no
Electronics Forum | Wed Nov 15 12:52:21 EST 2017 | georgetruitt
IMO – Look into nano-coatings for your stencil and radius all square apertures This should help out with solder paste releasing from the stencil helping with insufficient solder QFN LGA aperture design, try a stencil cut with a few different apertur
Electronics Forum | Mon Oct 26 06:27:50 EDT 2009 | bandjwet
SMTnetters: Does anyone have experience in the average programming time that they use for calculating costs on using a solder dispense and place process for QFN rework? How about average cycle time from start to finish for same? We are comparing it
Electronics Forum | Fri Dec 01 14:40:02 EST 2017 | emeto
Very interesting pictures. It shows paste height of 200um - which is at lest 6mil stencil deposit. That on the other hand posts another question. Can you measure the ground pad level in relation to the solder mask level with the SPI? I had assemblies
Electronics Forum | Fri Dec 01 15:06:54 EST 2017 | emeto
I am not sure that is doable. Ground Aperture is very small(for the stencil blade to get in there) and very close to the other apertures. I want to say the minimum requirement for step is 6mm clearance from other apertures for the stencil houses that
