Taguchi design of experiment for wafer bumping by stencil printing

Taguchi experiments are designed and carried out with five critical factors that influence the solder bumping of a 200 mm (8") wafer by stencil printing method. These factors are: paste types (type 3 and type 4), squeeze forces (9 and 12 lbs.), snap-off heights (0 and 5 mils), aperture shapes (square and circle), and aspect ratios (2.5 and 2.75). They are varied to form a two-level L8 orthogonal array experiment. Analysis of mean (ANOM) and analysis of variance (ANOVA) are used to choose the most influential factors. After fixing the most influential factors, a two-level L4 orthogonal array experiment is followed to optimize the other material and process parameters. Important results are summarized in this paper which could be very useful for wafer bumping with stencil printing method