Stencil Design Guidelines

The IPC organization publishes a Stencil Design Guideline. See: http://www.ipc.org/TOC/IPC-7525A.pdf Is this the standard most often used for designing stencils? Are there any other stencil design guidelines or references?

N. N.

Expert Panel Responses

The IPC stencil guidelines are the most commonly used and are a good starting point, however they do not take into account outside variables that regularly come up in all manufacturing lines, such as environmental conditions, oven profile, printing variables (squeegee pressure, under-board support, squeegee speed, etc.) which all play an important role in eliminating re-work. Sound confusing? Well it is and that is why so many manufacturers have day to day issues with their manufacturing lines and defects. Can you learn all of these different variables? The answer is yes, at least for your individual line once you have detected all of the variables at your facility. However, it takes having a great relationship with a knowledgeable stencil vendor that can help you determine what defects are occurring, what the variables most likely are and how to adjust your aperture openings to help correct these variables. We have helped countless customers address these variables by addressing issues as simple as room climate, wiping materials, squeegee pressure and countless other issues. Sometimes it is a matter of good housekeeping at your facility, sometimes it is beyond good housekeeping and requires an analysis of aperture openings to the component, analyzing the issue at hand and redesigning the apertures to accommodate the issue, because the outside variable is indeterminate. Companies such as ours are more than happy to take a look at your data, or an existing assembly to help you determine what may be causing issues at your facility. If you would like further assistance please feel free to contact me.

Michael Ray
President
Integrated Ideas & Technologies, Inc.

Mike Ray is founder and president of Integrated Ideas & Technologies, Inc., a manufacturer of SMT stencils. Mike Ray developed the first successful universal frame and holds patents on the AXIS laser system.

It is definitely a very good place to start, you may find that for your particular process a modification from this standard is necessary to reduce the odd mid chip ball or stop a component from floating (LGA) but if you start with this and consult with your stencil provider then generally it works. Your stencil provider probably has some ideas on improving design of certain apertures to overcome specific issues as will your solder provider so if you have any concerns do not be afraid to ask for advice.

Richard Boyle
Global Product Champion
Henkel Electronics

Richard Boyle is a Global Product Champion at Henkel Electronics. He has over 25 years experience in the electronics assembly industry and is responsible for the global technical service of all of Henkel's solder materials.

IPC is releasing rev B of 7525. This as well as stencil vendor guidelines are used in the industry

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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