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Stencil Aperture Sizes



Stencil Aperture Sizes | 21 January, 2004

During a discussion about smt design one of our attendees said that he had been taught that stencil openings were typically designed .005 below the size of the copper smt pads. My experiance has been stencils are usually designed 1 to 1 with the copper, then reduced as needed by the assembler.

As a rule, are stencils normally designed with reductions or 1 to 1 and reduced later if needed???

Thanks in advance for your input.


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Stencil Aperture Sizes | 21 January, 2004

Depending on how you frame the question, either of you could be correct. Neither of you mentioned stencil thickness, which together with aperture opening [and stencil fabrication technology] define how well a paste will release. So, the key measures are: * Aspect ratio * Area ratio

Search the fine SMTnet Archives for more on these ratios

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Stencil Aperture Sizes | 22 January, 2004

Yes, 1:1 is more or less standard for gerber data provided to the assembler.

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