Electronics Forum | Tue Apr 10 08:37:36 EDT 2018 | davef
Hi Steve ... I found nothing in the manufacturers "paper" to help. Comments are: * I agree. No blobs. Solder on the thermal pad should me minimized. Too much solder will float the component. Old timers used to talk about 50-80% coverage. * If you'
Electronics Forum | Tue Feb 04 17:24:07 EST 2003 | jonfox
we have some pretty tight 0402 placements and our best fix was to reduce the pad (vertically speaking) from .030x.022 to .020x.022. Fewer tombstones and the paste flows out to the edge of the pads nicely. Only difference is that we have a 6mil sten
Electronics Forum | Wed Feb 05 14:20:45 EST 2003 | Stephen
One thing that worked for me was simply rounding off the pads, making square pads into circlesfor the stencil. It worked but did seem a little strange turning squares into circles for 0603's and 0402's and turning cirlces for BGA's into squares, (bu
Electronics Forum | Thu Jul 21 09:43:10 EDT 2005 | davef
We agree with Russ. The solderballs are probably the result of printing too much paste on the board. In designing your 5 thou thick stencil: * Aperatures for the pads should be identical to a IPC-7351 - SO8 [or worst case http://www.vishay.com/docs
Electronics Forum | Mon Apr 09 13:53:45 EDT 2018 | dleeper
I've never placed one of these before, but it looks like a poorly designed part. It has pads scattered asymmetrically around the body of the part. when it reflows this is going to apply uneven forces to the component, causing it to skew. I guess hav
Electronics Forum | Wed May 22 02:35:26 EDT 2002 | ianchan
hussman, hi, mebbe we get the stencil fab house guys who spend more time in the workshop making more stencils = more revenue, whereas your stencil fab house is more learned and refined? we make it a point to use an inhouse MS-Excel format to key in
Electronics Forum | Wed Feb 22 08:02:56 EST 2006 | dj44
I was looking for an stencil design for a 0.5mm pitch uBGA. Pad size is 0.38mm in diameter. We have been using 5mil stencil with type 3 no clean paste. What size aperture should we be using? Any suggestions?
Electronics Forum | Wed May 22 12:32:49 EDT 2002 | pwrgroup
which stencil vendor can deliver aspect ratio and area ratio and the statistical information to the user?It's difficult if the pad is modified.
Electronics Forum | Tue Jul 19 11:21:50 EDT 2005 | russ
You may want to try reducing the large center aperture on your stencil to 50-70% of the area of the pad. This is what we do with QFNs and it may be applicable in this case also.
Electronics Forum | Wed Feb 05 21:24:35 EST 2003 | davef
Stephen's correct. Radiased outer corners on 0402 pads really do seem to improve things. We aim to try "squared-up semicircles".
winsouce.jpg)
.gif)
