Pan Pacific Symposium Conference Proceedings


ENHANCING YIELD WITH SOLDER FLUX AND SOLDER PASTE PROCESS CONTROL

Author: Stacy Kalisz
Company: MV Technology Ltd.
Date Published: 2/13/2001   Conference: Pan Pacific Symposium


Abstract: Bump pitches and bump densities are decreasing as semiconductor process technology advances. Process control has become a key element in the success of chip scale package (CSP) and ball grid array (BGA) packaging. The ability to tightly control each assembly process to ensure high yields has given assembly houses a definite advantage in the market place.

Solder flux and solder paste deposition is a standard step during the chip attach and sphere attach portions of BGA/CSP assembly. A technique called ultra-violet fluorescence intensity mapping (UV FIM) has been introduced which allows flux measurement for system set up, process characterization, and production process control. Previous to UV FIM, commercial techniques for flux inspection were not available based on speed of inspection with standard lighting techniques and the inherent properties of solder flux. The UV FIM technique can also be utilized for solder paste inspection and is faster than most existing technologies for this application.

Existing assembly and inspection equipment can detect missing or skewed parts, UV FIM now enables material monitoring at flux and solder paste deposition. This paper includes results that demonstrate how in-line flux and paste process control can favorably impact production yields. Two-dimensional data was gathered for flux and paste location and area on board pads. This data is then utilized to flag flux deposition errors and avoid downstream defects. If errors are detected prior to chip attach or sphere attach, die and/or package yield loss is avoided since flux rework can be completed prior to attach. Maintaining process control for flux deposition can also assist in maintenance and set-up of flux deposition equipment.

Keywords: CSP, BGA, Flux Deposition, Inline Process Control



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