IDENTIFYING SOURCES OF SOLDER DEFECTS IN PRINTED CIRCUIT ASSEMBLIES INCORPORATING BALL GRID ARRAY PACKAGES
Author: David Moore Company: Celestica Date Published: 8/23/1998
Surface Mount International
Abstract: This paper discusses the root-cause analysis of E-PBGA open solder defects on a mixed technology Printed Circuit Assembly (PCA). The problem solving techniques were based on Shainin Statistical Engineering principles, and can be applied to quality improvement, product development, process control, and reliability engineering. Statistical Engineering allows for rapid convergence to the root cause, based on a process of elimination. During pre-production prototype builds, an unusually high level of open solder joints on eutectic ball plastic BGAs were identified at the customer's functional test. It was concluded that the defect was a strength-strain problem due to the configuration of the “bed-of-nails” probes in the In-Circuit Test (ICT) future. This equipment was used in the product's test strategy as an electrical test for identifying solder defects. Unlike many studies in which test vehicles are used to simulate the factors that will affect the assembly process, the fact that this work arose under production conditions resulted in a significant amount of information being gathered about an aspect of the process not usually studied in this context.