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Step-up areas-- Used to increase the volume and height of the solder deposit. Useful for ‘pin in paste’ and large format devices with co planarity consistency problems.
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Step-down areas--- Used to reduce the volume and height of the paste deposit (or possibly increase the volume depending on aperture area ratio and transfer efficiency). Useful to improve Deposit Volume Repeatability in fine line and micro package attachment.
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"Stepless" steps --- Ramped step-up areas, produced by the electroforming process, to increase paste deposits in selected areas of the stencil for large components or large features such as antenna’s or shieldings. Formed on the PCB side of the stencil to provide a smooth print surface for enclosed printheads etc while minimising smearing.
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Step-relief cavities Used to overcome board surface irregularities such as raised pads, vias, legends such as bar codes and edge clamping issues. These features also afford relief for paste print deposits in two step stencil printing processes… where the use of a thin stencil is followed up by a thicker stencil in order to achieve multi height deposits without the need for "keep out areas1".
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In order to print successfully, apertures must be designed to be a minimum distance from the step edge. This distance is dependent on the step dimensions and is known as known as a "keep out area"
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