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April 27, 2011

Solder Mask Stencil Tension

By request of external auditors, we need to start recording the tension of our solder mask stencils every 5000 cycles. Can you suggest how we measure the tension, and also provide an acceptable range?

D. P.

Expert Panel Responses

Stainless steel foil has a much higher modulus of elasticity than polyester screen fabrics. Conventional mesh tension meters are designed to measure mesh tension prior to mounting the foil. The proximity of the mounted foils to the edge of the polyester screens prohibits accurate readings of the mesh tension as well. RST Gauge has recently developed a tool designed specifically for measuring the tension in SMT stencils that takes into consideration the thickness of the metal that is mounted in the frame. The deflection measurement is taken from the center of the foil for the most accurate results. In general, an acceptable tension range is 20-45 N/cm. You will find that some of the softer metals being used by some vendors will actually stretch with repeated use depending on aperture density, resulting in reduced tension.

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Stephanie Nash
Director
Integrated Ideas & Technologies, Inc.
Stephanie Nash is the Director of Technical Services & Marketing for Integrated Ideas & Technologies, Inc., a premier manufacturer of SMT stencils. She has been instrumental in the stencil design and technical support.

Four Points (772-288-3271) showed a device for measuring stencil tension at the recent APEX Exhibit.

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Bill Coleman
Vice President Technology
Photo Stencil
For over 18 years, Dr. Coleman has been the vice president of technology for Photo Stencil, working closely with customers to understand their printing requirements. His efforts have resulted in several new stencil products.
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