Printed Circuit Board Assembly & PCB Design SMT Electronics Assembly Manufacturing Forum

Printed Circuit Board Assembly & PCB Design Forum

SMT electronics assembly manufacturing forum.


Raymond

#16834

Solder Printing Stencil design | 22 January, 1998

I have the following questions with regards to the solder printing stencil design : 1) Is the Electro-polish process recommended for laser cut stencil ? 2) Should the aperture walls be slanted at an angle or straight wall, i.e. trapezoidal openings vs rectangular opening from vertical cross section ?

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Mike McMonagle

#16838

Re: Solder Printing Stencil design | 26 January, 1998

| I have the following questions with regards to the solder printing stencil design : | 1) Is the Electro-polish process recommended for laser cut stencil ? | 2) Should the aperture walls be slanted at an angle or straight wall, i.e. trapezoidal | openings vs rectangular opening from vertical cross section ? 1) Electropolish is normally required only on chem-etch stencils to smooth the walls. 2) Trapezoidal apertures are a good idea if the board contains fine pitch components to assist in paste release and minimize stencil aperture clogging.

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Jon Medernach

#16837

Re: Solder Printing Stencil design | 27 January, 1998

| I have the following questions with regards to the solder printing stencil design : | 1) Is the Electro-polish process recommended for laser cut stencil ? | 2) Should the aperture walls be slanted at an angle or straight wall, i.e. trapezoidal | openings vs rectangular opening from vertical cross section ? The smoother the aperture wall the better, most laser cut stencils are polished as a matter of course, Trapezoidal aperatures are required for ultra fine pitch, we print .012" pitch with .006" thick stencil, no step down.

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Steve Gregory

#16836

Re: Solder Printing Stencil design | 28 January, 1998

Raymond, Have you ever heard of Band-Etch, or another term called Band-width Etch? It's a trademarked process of stencil etching from a company named BeamOn Technology, they're out here in "Silly-con" valley (408) 982-0161. They way they etch their stencils produces very smooth sidewalls without the need for electropolishing. I've used their stencils for pitches down to 15.7 mils. In fact, I'll be using their stencils at NEPCON this year. I work for Zevatech and we'll be building a little "keychain" board that has a 128-pin 15.7-mil QFP, a Tessera Micro-BGA, and a bunch of 0402's and 0603's on it. We used the stencil at SMI this past year and it works GREAT!

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fxb

#16835

Re: Solder Printing Stencil design | 23 February, 1998

| I have the following questions with regards to the solder printing stencil design : | 1) Is the Electro-polish process recommended for laser cut stencil ? | 2) Should the aperture walls be slanted at an angle or straight wall, i.e. trapezoidal | openings vs rectangular opening from vertical cross section ? Ithink the laser cut stencil is good enough.What the Electro-polish process?Who can do it?

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