Electronics Forum | Thu Nov 07 09:23:05 EST 2002 | russ
What would the considerations be in utilizing a type 4 paste as opposed to type 3? We have an assembly that has a large amount of uBGAs (12 mil diam pad)along with 50 mil pitch BGAs assorted fine pitch etc... We are experiencing difficulty in paste
Electronics Forum | Fri Nov 08 17:10:04 EST 2002 | rspoerri
Is that square inscribed or circumscribed with respect to the pad? It sounds like you're saying circumscribed (overprint) given the volume comment. Wanted to confirm though. Kim
Electronics Forum | Fri Nov 08 17:20:52 EST 2002 | davef
You need to get as much paste on the board as you can get. A BIG opening gives: * Better release. * More paste. You may be able to cheat further by rotating the square so that it is on the diagonal.
Electronics Forum | Fri Nov 08 14:48:58 EST 2002 | davef
Yours is (12 thou x12 thou)/(2x(12 thou +12 thou)x5 thou) = 0.60 * Aspect=W/T for electroformed stencils SB GT 1.1 => Yours is 12 thou/5 thou = 2.40 So, we kind of think of what you�re trying do as maybe printing a 16 pitch QFP, which gives you simi
Electronics Forum | Thu Nov 07 10:59:11 EST 2002 | pjc
IPC-7525 "Stencil Design Guidelines" is a good reference document to have. Here are notes from a Tessera, (a major mBGA mfg.), study- "Application Note Solder Stencil Requirement for mBGA" The stencil aperture is to be square, equal in size to the l
Electronics Forum | Wed Nov 13 04:36:46 EST 2002 | iman
does anyone know what environment factors(specifications?) and process control parameters(printer & reflow?) are optimal for running SMT using type 4 and type 5 solder paste respectively? Any pitfalls to avoid? The product we have been asked to use
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 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 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.
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
