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August 2008

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Subject:
From:
"Kane, Amol (349)" <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, Kane, Amol (349)
Date:
Wed, 27 Aug 2008 08:13:25 -0400
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Dear Technetters,
I am looking for some information about using step stencils in production. I have a 16 mil pitch QFN component with 7.8 mil square pads. This gives me unacceptable area ratio using a 5 mil stencil. Looks like I am going to have to use a 3 mil thick stencil with this component. I was thinking of using a 5 mil stencil with a 3 mil step.  There are chip components around the QFN device. The board is Lead-Free with ENIG finish. Using a Type 4 solderpaste.

I was looking for inputs from folks who are using step stencils on the squeegee types (metal vs. poly), changes in print parameters (speed, pressure, Snap off etc,), board design considerations (keep out areas around the component needing the step), resources I could go thru to obtain more information, stencil houses who specialize in this process, and common pitfalls.

Any inputs will be greatly appreciated.

Thanks,
Amol





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