Stencil Apertures and Board Finish Requirements

Is there any reason to alter apertures on stencils if board finishes change from ENIG to OSP?

R.W.

Expert Panel Responses

As long as no other process variables are changed, i.e. solderpaste type, reflow oven profile, etc,the wettability of ENIG and OSP finishes are very similar. There is no compelling reason to alter the stencil apertures. However, if one is switching from lead-based solderpaste to lead-free paste, stencil apertures should be altered. Lead-free solderpaste does not wet as well to ENIG or OSP finishes and require additional flux for proper wetting. In this case, apertures are increased to provide additional solderpaste volume. If you need any additional information, please feel free to contact me.

Robert Dervaes
V.P. Technology & Engineering
Fine Line Stencil, Inc.

Robert Dervaes has worked in the electronics industry since 1992 in both design and manufacturing. Over the past 11 years he has established the technical foundation of Fine Line Stencil, Inc. - a premier stencil supplier to the electronics industry.

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