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stencil printing SPC

yoman

#33201

stencil printing SPC | 14 March, 2005

I'm trying to develop an spc chart for the stencil printing process but don't know which direction to go. Any suggestion?

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RDR

#33202

stencil printing SPC | 14 March, 2005

what did your D.O.E. studies show you as the critical parameters? These are the ones that you need to measure. If you did not perform DOE than you probably should prior to putting an SPC chart out there. What type of measurement capabilities regarding the print process and materials do you have?

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yoman

#33216

stencil printing SPC | 15 March, 2005

Thanks for your reply. We are using EKRA E4 Inline Automatic Stencil Printer. It is Capable of Automatic stencil inspection. 2D solder coverage inspection. Fix Squeegee angle at 45 degees angle. Programmable squeegee speeds and pressure, boards snap off speeds,etc.

We did very little DOE on squeege speeds and pressure, its very hard to see any difference till after reflow.I am looking for some sort of measurement after solder printing. Would be greatful for any recommendation for implementing a DOE.

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RDR

#33231

stencil printing SPC | 16 March, 2005

This is what I might do, I would purchase either a solder volume (preferred) or at the least a paste height measurement piece of equipmment, The most important parameters with pronting are volume and registration. You need one of these inspection devices to properly perform DOE and/or SPC. I would print a board and then take measurements of paste at certain locations and record the data on an XbarR chart. Change printer settings 1 at a time unless you are an SPC guru and can handle the fractional factorials and all of that, and then perform the same data collection. This will show you the changes in volume/height/definition. You will need to check print definition although I have found that the actual shape of the "brick" is not all that important. Although if you find that the edges are very poorly defined you will probably need to correct. SPC on the print process is very valuable but it will not guarantee the absence of any defects concerning that little aperture that got clogged on the last print unless you perform some type of AOI on the entire board.

Hope this was somewhat helpful

Russ

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