Electronics Forum | Thu Mar 19 20:12:32 EDT 2020 | slthomas
Stephen, you are spot on with your description. Here's a .jpg with paste layer, copper, and solder mask.
Electronics Forum | Mon Mar 23 16:38:09 EDT 2020 | emeto
Steve, On 16mil pitch I would try 12mil diameter on 5mil stencil, unless the BGA ball size is something unexpectedly huge.
Electronics Forum | Fri Mar 27 03:42:17 EDT 2020 | sssamw
Did you try 0.12 or 0.1mm nano coated stencil @ 10 mil aperture? A soak time type profile with long reflow time could help.
Electronics Forum | Tue Jun 02 21:27:22 EDT 2009 | davef
We've never heard of a situtation where oversized pads caused voiding. Your supplier is correct that the pads on the board should be the same size as the pads on the interposer, but this is to improve reliability issues. Search the fine SMTnet Archi
Electronics Forum | Thu Jun 04 20:06:30 EDT 2009 | davef
Since posting the above comment extolling the virtues of NSMD pads and disparaging SMD pads, we've learned that the points apply to all array devices, but in spite of that some designers of fine pitch [eg, 0.4, 0.5mm pitch] array devices choose SMD w
Electronics Forum | Thu Mar 19 16:06:29 EDT 2020 | stephendo
Imagine a circle. Now imagine a line attached to that circle. A line almost as wide as the circle. Or look at a regular BGA pattern now imagine if the traces were almost as wide as the pads. I have not seen any quite as bad as he describes but I have
Electronics Forum | Tue Mar 24 10:34:03 EDT 2020 | slthomas
My experience with our process is that those parameters would result in a big bridging problem. I'm working with a stencil designer at our fabricator on an asymmetrical aperture design that hopefully balances forces enough to keep the parts centered.
Electronics Forum | Thu Feb 02 09:07:28 EST 2023 | charles_nguyen
Two types of land patterns used for surface mount pads are non-solder mask defined or NSMD pads and solder mask defined or SMD pads.Each type has its own advantages and disadvantages. There is a statement that SMD pad type may introduce stress concen
Electronics Forum | Wed Mar 18 11:27:24 EDT 2020 | slthomas
I am about to order a stencil and I can already see that I'm going to have issues. I'm hoping someone has a recipe for this scenario that we haven't tried yet. The parts are 16 mil pitch bga's, the pads are NSMD (10 mil dia. with 12.6 mil mask open
Electronics Forum | Thu Oct 25 13:35:47 EDT 2012 | davef
Here's a paper that may help http://www.ipcoutlook.org/pdf/assembly_challenges_bottom_terminated_ipc.pdf Temperature Impact * Profile didn’t have a significant impact on voiding. * Voids slightly increased with higher temperature. Reflow Atmosp
