The book-to-bill ratio for North American chip equipment makers was 1.05 in May, according to SEMI's preliminary estimate. That represents a decline from March's 1.12 and April's 1.10, and suggests the recent rebound in chip equipment orders (fueled by strong demand from TSMC and other foundries) is losing steam. The weak guidance delivered on Tuesday by FSI International (NASDAQ:FSII) heightened fears of an industry slowdown.