Mini stencils from Tecan Stencils Limited (TSL) ensure accurate repeatable paste deposits are produced when replacing components such as QFP’s, PLCC’s and BGA’s during PCB re-work operations.

Individual component footprints are faithfully replicated by the mini stencils, with apertures which precisely correspond to the pads on the PCB from where the original component was removed. Rework is completed in a cost effective and controlled manner with far more consistent results than traditional ‘hit and miss’ methods. In combination with a rework station, the stencils ensure human error and alignment problems are significantly reduced resulting in a controlled ‘right first time’ solution.

In operation, the stencil is simply placed in position on the ‘cleaned’ pads and paste is deposited by hand using a mini squeegee blade. The accurate apertures ensure exactly the right amount of paste is deposited, folded edges provide protection from any overspill, localised re-flow follows.

The stencils are supplied as assemblies complete with all necessary interfaces, such as articulated stalks or vacuum attachments, for the rework station or placement system adopted. Accurately folded edges and run-on/run-off areas ensure that the compact stencil does not interfere with other components on the populated PCB.

Mini stencils are also available for re-balling and fluxing BGA’s and for SM connectors and similar components. Mechanical and thermal stresses are kept to a minimum using the technique allowing devices to be re-flowed without exceeding manufacturers’ recommended stress limits.

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