Surface Mount International Conference Proceedings


Author: K. Berger
Company: IBM Microelectronics
Date Published: 9/10/1996   Conference: Surface Mount International

Abstract: One key issue for ceramic ball grid array users is the use of quality packages in the bond and assembly process to minimize overall cost. Second level assembly requires good solder ball to package pad alignment in order to ensure a complete reliable solder ball fillet, ensure around future for card assembly placement vision systems, and be cosmetically acceptable. JEDEC guidelines define positional tolerances for the ball array. In order to meet the ball locational tolerances and ensure that the balls are well centered on the package pads, it is necessary to specify a pad locational tolerance. This paper will describe the work done at IBM Microelectronics in order to measure pad locations and define a pad distortion level that will give good ball to pad alignment. This evaluation was accomplished through a detailed study of the ball placement process and visual image recognition measurement techniques. Experimental results will be presented which correlate pad distortion levels with ball to pad offset. Key Words: BGA Pad, Solder Ball, Positional Tolerances, JEDEC

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