Advanced directory solves the problems of solder stencil efficiency

Citation

(2007), "Advanced directory solves the problems of solder stencil efficiency", Soldering & Surface Mount Technology, Vol. 19 No. 3. https://doi.org/10.1108/ssmt.2007.21919cab.003

Advanced directory solves the problems of solder stencil efficiency

Advanced directory solves the problems of solder stencil efficiency

Electronic assemblies today often contain diverse component populations making it essential to ensure the solder paste volume, deposited by the stencil used, matches the individual component requirements. World- leading specialist, Tecan, has announced the publication of “The Highway Code of Stencils” which the company says offers the electronics industry a comprehensive reference source of how to achieve the best possible printed results from the stencil to enhance the whole surface mount process.

“Failure to optimise paste volumes to achieve the appropriate deposits required only leads to subsequent expensive rework,” said Tony Weldon, Tecan Stencil Manager. “For example, continued miniaturisation of electronic components has resulted in a greater use of thinner stencils to achieve improved paste release for fine-pitch and small apertures. Simply reducing the general stencil thickness however can leave surface-mount connectors, ceramic BGAs and components requiring more paste with reduced or starved solder fillets. To ensure optimised stencil performance these and other considerations must be taken into account.”

“It is widely appreciated that a stencil is far more than just a thin metal sheet with apertures that represent the copper features of a printed circuit board; it is in fact a dedicated tool, the design of which is critical to the success of the printing process itself,” continued Tony Weldon. “With all stencils, no matter which method of production used to create them, the apertures have to be considered as three-dimensional. The Highway Code of Stencils takes the user through in-depth performance considerations and presents the choice of solutions available that can be tailored for individual manufacturers' needs.”

The new publication explores in- depth the essential characteristics that “optimised” stencils must possess, including:

• •

  tapered aperture walls to increase deposit stability and promote improved paste transfer;

• •

  smooth aperture walls to reduce paste “stiction” and thereby improve deposit consistency;

• •

  multi-level or locally appropriate stencil thicknesses to deliver tailored paste volumes;

• •

  enhanced paste-roll characteristics to enable the solder paste to fill the stencil apertures; and

• •

  expected aperture shape and positional accuracy required.

The Highway Code of Stencils explores the variety of challenges presented to the surface mount assembler in easy to understand sections offering suggestions and guidelines for optimum stencil printing performance – asking the reader to consider questions such as:

1. 1.

   Is it possible to improve paste release for fine-pitch components and also maximise solder deposits for the remainder of the component population?

2. 2.

   Does one particular stencil technology offer advantages over another?

This comprehensive publication details every aspect of printing performance and offers in-depth insights into associated surface mount technology issues, including: the printing process, stencil types (precision-etched/laser-cut/ electroformed/laser-formed) including single- and multi-level stencils, as well as the differences between leaded and lead-free pastes, the importance of paste roll activation, the solder paste alloys available, enhanced squeegee technology and a great deal more.

For further information, please visit: www.tecan.co.uk