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Quality performance specifications

marys

#23607

Quality performance specifications | 3 March, 2003

How do I determine what the quality performance specifications are for my SMT equipment?

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#23615

Quality performance specifications | 3 March, 2003

Hello marys, To determine the quality performance specification of your printers, dispensers or placement equipment, you must first know the operational accuracy and repeatability criteria from the equipment manufacturer. Only then can you determine theoretical capability performance values. For instance, let's assume a printers vision alignment system has an accuracy and repeatability specification of +/- 25 micron (+/- 0.001 in) at 4 sigma. When evaluating machine performance, the standard deviation, or measure of variability, is a critical value in assessing a machines ability to accurately and repeatedly perform the same function over time with minimal influence from variability. To determine the standard deviation's theoretical performance threshhold, we divide the specification by our desired quality indice. In this particular case our threshhold value is 6.25. For this printer, all calculated standard deviation values considering multiple observations must fall well below 6.25 for each functional axis of the machine. Only then will the machine meet the desired Cp and Cpk performance specifications. Let me know if you require additional assistance. Thanks!

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