Highly-polished squeegees boost lead-free paste performance

Citation

(2004), "Highly-polished squeegees boost lead-free paste performance", Soldering & Surface Mount Technology, Vol. 16 No. 2. https://doi.org/10.1108/ssmt.2004.21916bad.008

Highly-polished squeegees boost lead-free paste performance

Highly-polished squeegees boost lead-free paste performance

Keywords: Lead-free soldering, Solder paste

Printed circuit board producers are again set to benefit significantly from advanced manufacturing techniques introduced by Dorset based specialist, Tecan, as part of its ongoing initiative to deliver lead-free manufacturing solutions.

The company has now developed a range of "highly-polished" squeegee blades that outperform traditional blades. They offer advantages such as true compatibility with lead- free pastes, optimised aperture fill and paste- conditioning characteristics that extend print life.

Highly-polished electroformed squeegee blades have been developed to address the rheology problems associated with less dense lead-free and "no-clean" pastes. Effectively, these pastes have a tendency to "cling" to a conventional unpolished blade resulting in "paste hang-up" at the end of the print stroke, thereby reducing the paste bead on subsequent print strokes. The new squeegees deliver a proven solution to all these problems and are particularly beneficial for mixed-component and fine-pitch applications, allowing manufacturers to achieve the most consistent and repeatable performance possible from existing printing machines. The improved "paste-roll" characteristics aided by reduced surface tension also extend the printing life of the paste.

Furthermore, successful printing can only be achieved with the selection of the most appropriate stencil, solder paste and paste delivery system, says the company. To achieve the best results, the blades should also possess flexibility to consistently deliver the expected paste volumes. To this end, Tecan has developed "reactive" metal squeegee blades with a mobile "feathered" edge.

These durable reactive blades have been tested against a range of single thickness metal blades, coated metal blades and traditional polyurethane materials. In the tests they were proved to provide significant improvements to printed results, when used with either simple single thickness stencils or multi-level stencils featuring both raised and recessed areas.

These mobile-edge squeegees enhance the performance of today's printers by delivering repeatable results, which match the demands of fine pitch printing. They also provide the solution to the problems of scooping or scavenging that polyurethane squeegees create with larger apertures. The mobile edge allows the blade to flex locally, to overcome uneven surfaces such as proud via holes, thicker tracks and poor silk- screening – recovering quickly to deliver clean consistent printed results.

This provides significantly better and more accurately defined deposit formations increased process control and improved product quality.

The blades are an effective solution for printers that use trailing edge squeegees. They can either be positioned in front of an existing polyurethane squeegee, where the metal edge becomes the printing edge, or, used as a direct replacement for polyurethane squeegees where the holder permits.

For further information, visit the Web site: www.tecan.co.uk