Just Ask Greg: Advice on Purchasing SMT Stencils

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We asked you to send in your questions for Happy Holden, Joe Fjelstad, Eric Camden, and John Mitchell in our “Just Ask” series. Now, Greg Smith, an SMT007 columnist, gets a chance to answer a question.

Greg Smith has worked in the electronics industry since 1989. He was the owner and president of a stencil manufacturing company for 23 years before joining Fineline Stencil. After the merger of Fineline Stencil and MET, he became the manager of stencil technology for BlueRing Stencils. Greg writes and presents white papers, works with customers on stencil design, and performs root-cause analyses to improve customer yields.

We hope you enjoy “Just Ask Greg.” 

Q: Should we buy just the foil, or do you think that it’s better to buy and keep them on the same frame for repeat orders?

A: There are several options when purchasing SMT stencils. The first option is framed stencils, where a polyester mesh is mounted to an aluminum frame, and the stencil foil is then mounted to the polyester mesh. The mesh is then removed within the stencil foil, leaving a very uniform tension on the foil from all four sides. This is historically the best method for using SMT stencils. When the stencil is needed, it can be placed directly into the printer, used, cleaned, and then placed back in storage.

With this traditional framed stencil, there are no worries about tensioning bladders that can leak during the mounting or de-mounting process or springs that can become week over time. However, some of these frames require more storage space than the non-traditional “frameless” systems available.

The second type of frame option is foils with tensioning systems around the sides of the foils, such as DEK VectorGuard™, Apshen, and QTS systems. These fit into “master frames,” and tension is applied to the foils before printing. These are good options when stencil storage is at a premium while still providing even tension on the stencil foil during the print process. It is not recommended to order stencils that are not tensioned in some way during the print process. 

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