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July 9, 2018

Recommended Solder Paste Aperture Configuration

What aperture shape/configuration do you recommend with our solder paste stencils for 008004 and 01005 pad sizes?


Experts Comments

Successful ultra-fine pitch printing as required for 008004 and 01005 components pushes the boundaries of current paste, stencil and equipment technologies. Multiple input variables need to be optimized to achieve the desired result. Chief amongst these are solder paste, stencil materials and aperture designs. Extensive print testing indicates that a 'squircle' aperture (a square with a radius corner) consistently outperforms either a round or square aperture.
Tim O'Neill
Technical Marketing Manager
Tim O'Neill is the Technical Marketing Manager for AIM Products. AIM is a global supplier of materials for the PCB assembly industry including solders, fluxes and thermal management materials. Tim has a B.A. from Assumption College and post-graduate studies in education. He has 20 years of experience in the electronics soldering industry, beginning his career in 1994 with EFD and was key in business development of their fine pitch solder paste dispensing technology. Tim joined AIM in 1997 and has since assisted many clients with assembly challenges, specializing in Pb-Free process development and material selection.

008004 .004 x .005 oblong with .003 space
01005 .005 x .006 oblong with .004 space

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.

Unfortunately there is not an industry standard for these smaller components at this time. Several big name users have developed and optimized their own pad stack that works best for them.

For the stencil, I would recommend something in the .003" (75 micron) range for a thickness and nanocoating is a must.

The aperture can then be 1 to 1 with the pad.
Eric Bastow
Senior Technical Support Engineer
Indium Corporation
Eric is an SMTA-certified process engineer (CSMTPE) and has earned his Six Sigma Green Belt from the Thayer School of Engineering at Dartmouth College. He is also a certified IPC-A-600 and 610D Specialist. He has an associate's degree in Engineering Science from the State University of New York and has authored several technical papers and articles.
I will follow the manufacturer's recommended pad shape. However, when dealing with such small components, your solder type and stencil release will be the key players in your process.
Edithel Marietti
Senior Manufacturing Engineer
Northrop Grumman
Edithel is a chemical engineer with 20 year experience in manufacturing & process development for electronic contract manufacturers in US as well as some major OEM's. Involved in SMT, Reflow, Wave and other assembly operations entailing conformal coating and robotics.
A 15% reduction on the pad size and 2 mil stencil worked for the applications that I have done. The used shape for the aperture is the classic square.
Georgian Simion
Engineering and Operations Management
Independent Consultant
Georgian Simion is an independent consultant with 20+ years in electronics manufacturing engineering and operations.
Contact me at georgiansimion@yahoo.com.
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