Abstract:

Ball grid array package (BGA) warpage due to mismatch of the coefficients of thermal expansion and the asymmetric package geometry, has created some solder joint reliability problems, especially for chip scale packages. Methods to assess the design and process factors influencing warpage include electronic speckle pattern interferometry (ESPI), shearography and moire However, these methods are generally time consuming and expensive.

A non-contact and material independent determination of deformation and strain using three-dimensional (3-D) image correlation method and high-resolution digital CCD cameras has now been successfully implemented for measuring package warpage. This method significantly reduces the cost and time-consuming preparation necessary. For fast measurements, standard cameras can gather data at up to 20 fps as necessary, and for high-speed manufacturing tests, high-speed cameras can gather data at 485 fps to rates of up to 10M fps, or in real-time. Therefore this technology can collect data 30 times faster. It also has a much higher dynamic range of deformation measurements and is hundreds of times less sensitive to vibration interference than ESPI.

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