SMTA International Conference Proceedings

Characterization and Failure Analysis Techniques for Ball Grid Array Solder Joints

Authors: Adam W. Mortensen, Maria C. Lee and Roger M. Devaney
Company: Hi-Rel Laboratories
Date Published: 9/28/2014   Conference: SMTA International

Abstract: The necessity for smaller complex assemblies in Printed Circuit Board (PCB) manufacturing has given rise to the use of Ball Grid Array (BGA) devices, primarily due to their density of solder connections over a small area. Other devices, such as pin grid arrays and surface mount integrated circuits, have become difficult to use because of potential electrical shorting from limited spacing between the solder connections. While the number of solder connections on BGA’s is an advantage regarding space and size, the devices do have potential issues. Reduced mechanical strength of the solder connection due to the small surface area of each joint can result in fracture. Coefficient of Thermal Expansion (CTE) mismatch during reflow or thermal cycling can cause flexure between the component and board, putting additional stress on the solder joints. The transition to lead (Pb) free solder driven by RoHS has created additional problems (e.g. Head-in-Pillow {HiP}, black pad defect, pad cratering, etc.). Characterization of BGA solder joints is critical in determining the quality of an assembly and when identifying the cause of a failure. This paper will describe techniques used for BGA solder joint characterization and failure analysis. Non-destructive techniques, such as visual examination and radiography, are typically the first tests performed and are used to identify such things as misshaped solder joints and voiding, but are limited in their ability to locate failures and defects. Further testing with destructive techniques, including Dye & Pry analysis, cross sectional evaluation, and subsequent examination in a Scanning Electron Microscope (SEM) with analysis by Energy Dispersive Spectroscopy (EDS), is typically used for interfacial analysis and can identify the majority of failures in BGA solder joints. While most of these techniques are common, the success of an analysis is based on the implementation and interpretation of each test.

Key Words: 

Ball Grid Array, Printed Circuit Board, Head in Pillow, Black Pad Defect, Pad Cratering, Dye and Pry

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