Electronics Forum | Sat Oct 07 16:31:56 EDT 2000 | Elfego
Tray the electroform stencil.
Electronics Forum | Sat Oct 07 11:14:39 EDT 2000 | Aaron
1. It is hard to tell, but your PCB vendor should test the PCB. 2. I think the important thing is the width of the apertures. You should have it laser-cut, and control the width no more than 90% of half pitch. Good luck.
Electronics Forum | Mon Oct 09 19:56:41 EDT 2000 | Dave F
CJ: Arturo and the others make good suggestions. Consider: IPC-7525 Stencil Design Guidelines
Electronics Forum | Sat Oct 07 04:02:50 EDT 2000 | C.J. Long
Good morning, All: I am from PCB shop and one of our customer is experiencing solder bridge on 16 mil pitch QFP( immersion gold finish). Land width requirement is 8 +/- 1 mil measured over top of of land and our mean is 7 mil. Bottom land width is 8
Electronics Forum | Tue Oct 10 20:14:01 EDT 2000 | Dason C
Hi! CJ. Please advise what is your pitch size ie 15.7 mil or what is your capabiliy can you build the board with pitch 15.75 mil (please note that the actual dimension of the package is 0.4mm), and how many lead on the package. The pad width of Ind
Electronics Forum | Sun Oct 08 00:18:05 EDT 2000 | Arturo
We are working with a 16mil TSOP Land width=0.2mm(8mil) and use: 1.Type 4 particle size solder paste. 2.Laser cut electropolished stencil: Aperture width=0.19mm (we tried lower than this but had solder insufficiency). Thickness=0.005"(130 microns)
Electronics Forum | Mon Apr 07 11:39:55 EDT 2003 | russ
How thick is your stencil? We print 16mil every day with type 3 paste 2 of which you have tried (Alpha and Kester) Stencil should be 5 mil. Russ
Electronics Forum | Mon Apr 07 09:52:07 EDT 2003 | kmorris
I have just started an assembly which uses a 16 mil pitch QFP. We ran on Saturday, using a type 3 solder paste. (working Sat's really sucks) We really struggled with paste release after the stencil sat for 15 minutes without printing. Apertures clog
Electronics Forum | Mon Apr 07 13:02:30 EDT 2003 | kmorris
Sorry, I forgot to include the stencil thickness. It is 5 mil. Thanks for the input, everbody. I just checked with our stencil supplier & I thought that Electro-polish was standard with lazer, but I now find out it is not. Our stencil did not get
Electronics Forum | Mon Apr 07 12:21:02 EDT 2003 | davef
Russ is correct. A 5 thou thick stencil should give good release. Here's how you run through it: * You want at least 5 solder particles across the smallest aperture. So in your case, 8 thou wide, which equals to 0.20mm gives us 0.20/5=40 microns.
