Print Parameters

Optimal Print Parameters:

I have responded to a similar question in the thread titled �Stencil Printing For 0201 Applications�, posted by markt and will refer you to that for addressing this question. If you seek clarification on any of those points, please reply with another query.

Stencil Design Layout Considerations:

The aperture size that produced the best results for me matched the pad dimensions very closely (15 mils long x 11 mils wide rectangle aperture), although it was 0.5 mils narrower on two sides. Thickness of the stencil was selected to be 5-mils based on the idea that:

- 6 mil thick stencil may not produce acceptable transfer efficiency for such a small aperture size (i.e. approaching area ratio violation threshold).

- 4 mil thick stencil may not comply with the larger solder volume requirements for other common surface mount components.

A laser cut stencil was used exclusively for the evaluation of the complete 0201 assembly process, which addressed printing, placement, and reflow. However, I have also conducted off-line 0201 print tests using an electroformed stencil. The print deposits using the electroformed stencil do appear to look nicer and may produce marginally better volume repeatability and transfer efficiency. You will probably be able to get away with using the under stencil cleaning system less frequently with an electroformed stencil compared to laser cut. These marginal gains may not, I suspect, have an overwhelming influence on the overall assembly yield. Hence, armed with what I know currently, my decision to use laser vs. electroformed for 0201 assembly would be primarily driven by cost.

-Jeff

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