PASTE PRINTING AND CHARACTERIZATION FOR CHIP SCALE PACKAGE ASSEMBLIES
Author: Julian Partridge Company: XeTel Corporation Date Published: 8/23/1998
Surface Mount International
Abstract: A study of solder paste printing applied to typical CSP geometries is discussed. Apertures applicable to 0.5 mm pitch and 0.75 mm pitch CSPs include 10, 12, 14 and 16 mil diameter with nominal stencil foil thickness of 6 mil. Results are presented for the effect of paste and stencil type on paste release in addition to the effect of aperture aspect ratio on the paste release characteristics. Two in- line automated paste measurement systems were evaluated for their suitability for measuring paste volumes as low as 150 cu. mils per pad. Analyses of the results by standard statistical methods show the limitations of each tool at various aperture sizes and recommendations are made for application of such tools to the high speed measurement of small CSP paste deposits.