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|A Study of Solder Joint Failure Criteria|
|Keywords: failure criteria, solder joint, gauge repeatability and reproducibility|
|One of the challenges in an experimental study of solder joint reliability is to determine when cracks occur in a solder joint or a solder joint fails. Cracks in a real solder joint are difficult to identify using an X-Ray system. Cross-sectioning and scanning electron microscopy (SEM) is a destructive method. A common non-destructive test method is to monitor resistance increase in a solder joint or a daisy-chain. However, different researchers have used different failure criteria, for example, a resistance threshold of 450Ω, a threshold of 1000Ω, an increase in resistance of 10Ω or greater, the resistance change of 5Ω, or the resistance change of 20%. In a sense, all of these criteria are subjective, because, at this time, no scientific research has been done on the interconnection failure criteria. This paper reports the results of a study on solder joint failure criteria. The principles of defining failure criteria are to be able to detect failure of solder joints as early as possible with no false detection because of data acquisition error/variation. First, a gauge repeatability and reproducibility (GR&R) study of a resistance measurement system was conducted. Then, a dozen solder joints that were observed to have increase in resistance were cross-sectioned and inspected using SEM. The relationship between the crack and the resistance change was established. This study confirms that a full crack of an interconnection occurs when the increase of resistance in the interconnection by 2 ohms measured by a system with GR&R of +/- 0.2 ohm. The results of this study could be used to revise the failure definition in IPC 9701.|
|Jianbiao Pan, Associate Professor
California Polytechnic State University
San Luis Obispo, CA