CERAMIC SUBSTRATE THICKNESS, TEST BOARD THICKNESS, AND PART SPACING: A SCREENING DOE
Author: Thomas Koschmieder Company: Motorola SPS Date Published: 9/12/1999
Abstract: A screening design of experiment (DOE) on the reliability effects and interactions of ceramic BGA substrate thickness, board thickness, and part spacing was completed. The substrates used were 32.5x32.5 mm sq. and had thicknesses of 0.8, 1.8 and 2.85 mm. The board thicknesses were 0.79, 1.57, and 2.36 mm, each type being 4 layers with 2 ground planes. Spacing between parts varied from 5.0, 10.0, to 15.0 mm. Two daisy chains existed for each substrate, one including the corner regions and the other including the other BGA joints. Results showed that ceramic substrate thickness dominated board level CBGA reliability with thinner leading to higher reliability. In general the thickness effect followed the trends seen in other experiments. Test board thickness and part spacing were not significant in influencing the board level reliability obtained. Analysis of failed joints showed that the 0.8 mm substrates failed on the substrate side while the 1.8 and 2.85 mm substrates had the joints fail on the test board side.