A combination of proven design features have been brought together to ensure lead-free printing success through the adoption of stencils and squeegees from Dorset based market leader, Tecan.

A combination of proven design features have been brought together to ensure lead-free printing success through the adoption of stencils and squeegees from Dorset based market leader, Tecan.

The company manufactures polished Nickel squeegee blades which offer superior handling of lead-free solder pastes which characteristically are higher in tin content and therefore less dense than traditional leaded pastes. In addition to promoting effective paste roll, the highly polished blades ensure reduced paste hang-up on the blades themselves at the end of the print stroke – this significantly aids paste conditioning. Improved paste roll characteristics also extend the printing life of the solder paste.

A further defining feature of the Tecan squeegee blades is their reactive mobile edge. The mobile edge allows the blade to flex locally to overcome uneven substrate conditions such as proud via holes, thicker pads or poor quality silk screening to deliver clean consistent printed results. This provides significantly better and more accurately defined deposits, increased process control and improved product quality.

Stencil design is crucial to ensuring repeatable lead-free printing success. By combining its extensive industry knowledge and experience with the in-house flexibility to manufacture stencils in all formats, technologies and thicknesses Tecan can optimise any lead-free SMT printing line.

Its multi level stencils deliver appropriate thickness paste deposits for all components on the PCB, eliminating the need for expensive rework. Whatever the stencil choice a proprietary surface finish known as paste roll activation (PRA) is incorporated into all lead-free stencils including precision laser, laser-formed and electroform variants.

PRA is an effective micro-fine pattern created on the squeegee side of the stencil which has been designed to significantly improve paste roll. The PRA wave pattern assists in activating and ‘conditioning’ the paste to improve its rheology. This paste conditioning also extends the printing life of the paste. Effective paste roll is an important pre-requisite for successful solder paste printing and the PRA pattern delivers a better aperture filling capability than non-PRA stencils and is proven to be particularly beneficial for fine pitch applications.

Completing its lead-free print optimisation offering, the company recognises the appropriate aperture reduction required for lead-free applications. Aperture sizes are enhanced using its bespoke CAD system library to ensure whatever the component type or pad finish, lead-free paste deposits are entirely appropriate to individual requirements.

Its range of colour coded squeegee blade holders also provide the necessary segregation for companies using both lead-free and leaded processes to ensure there is no cross-contamination within the production environment.

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