Free calculator eases surface finish dilemma.

ATLANTA -- A new Excel spreadsheet tool aids users in determining the best surface finish for a particular design. The tool was created by Bob Lazarra, a former designer and now vice president of business development for PWB fabricator CircuitConnect (circuit-connect.com).

Lazarra, who calls the new tool SurfaceCalc, explains his motivation: "I'm often asked by frustrated assemblers, 'What's the best Pb-free surface finish for me?' By the time I go through the laundry list of variables, influences and exceptions, I feel more like a defense attorney and less like their go-to guy for tech support. So I created a spreadsheet surface finish calculator that empowers assemblers to make their own decisions."

SurfaceCalc compares five popular Pb-free surface finishes (ENIG, HAL, OSP, immersion silver and immersion tin) with 17 factors affecting overall surface finish performance (including cost). Default scores and factors are based on 35 related research reports presented at the 2006 SMTA International conference. Scores are user addressable, and factors are user selectable, with a provision to add an additional three factors. Users can select which of the factors to include, and can change default scores assigned to each finish.

SurfaceCalc produces both statistical and graphical comparisons. Lazarra, who makes the tool available for free ([e-mail]), plans to update it annually.