The reliability or lifetime of micro-joints on printed circuit boards (PCBs) is significantly affected by fatigue processes, including fatigue crack initiation and propagation to failure. Accordingly, the industries producing electronic devices and components strongly desire a new nondestructive inspection technology, which detects micro-cracks appearing as thermal fatigue fractures in the joints. In this investigation, we applied a synchrotron radiation X-ray micro-tomography system called the SP-μCT to three-dimensionally and nondestructively evaluate the fatigue crack propagation process in complex-shaped solder joints. The observed specimens have a typical joint structure in which chip type resistors 1.0 mm in length and 0.5 mm in width are mounted on an FR-4 substrate by joining with Sn-3.0Ag-0.5Cu solder. A thermal cycle test was carried out, and specimens were collected at fixed cycle numbers. The same solder joints were observed successively using the SP-μCT at beamline BL20XU at SPring-8, the largest synchrotron radiation facility in Japan. An X-ray energy of 29.0 keV was selected to obtain computed tomography (CT) images with high contrast among some components, and a refraction-contrast imaging technique was also applied to the visualization of fatigue cracks in the solder joints. The following results were obtained. At the early stage in the fatigue process of normal joints, the main fatigue cracks were clearly observed to initiate from the region around the solder joint tip and the vicinity of the chip corner. Additionally, many micro-cracks roughly 5 to 10 μm in length also formed in the thin solder layer between the chip and substrate. The important observed fact is that these micro-cracks deform, grow, and connect to each other due to the thermal cyclic loading, prior to main crack propagation. On the other hand, in case of solder joints which included relatively larger initial voids, the voids deformed, and the fatigue cracks initiated and propagated from the surface of the voids. Furthermore, by employing the three-dimensional crack images, the crack dimensions were quantified straightforwardly by measuring the surface area of the fatigue crack, and the fatigue crack propagation process was also accurately evaluated via the average crack propagation rate. Consequently, the obtained CT images clearly illustrate the process of crack propagation due to the thermal cyclic loading of a solder joint. In contrast, such information has not been obtained in any form by industrially employed X-ray CT systems or finite element analyses.
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ASME 2011 Pacific Rim Technical Conference and Exhibition on Packaging and Integration of Electronic and Photonic Systems
July 6–8, 2011
Portland, Oregon, USA
Conference Sponsors:
- Electronic and Photonic Packaging Division
ISBN:
978-0-7918-4461-8
PROCEEDINGS PAPER
Three Dimensional and Nondestructive Evaluation of Thermal Fatigue Crack Propagation Process in Complex-Shaped Solder Joints by Synchrotron Radiation X-Ray Micro-Tomography
Hiroyuki Tsuritani,
Hiroyuki Tsuritani
Toyama Industrial Technology Center, Toyama, Toyama, Japan
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Toshihiko Sayama,
Toshihiko Sayama
Toyama Industrial Technology Center, Toyama, Toyama, Japan
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Yoshiyuki Okamoto,
Yoshiyuki Okamoto
Cosel Co., Ltd., Toyama, Toyama, Japan
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Takeshi Takayanagi,
Takeshi Takayanagi
Cosel Co., Ltd., Toyama, Toyama, Japan
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Kentaro Uesugi,
Kentaro Uesugi
SPring-8, Japan Synchrotron Radiation Research Institute, Mikazuki, Hyogo, Japan
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Takao Mori
Takao Mori
Toyama Prefectural University, Imuzu, Toyama, Japan
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Hiroyuki Tsuritani
Toyama Industrial Technology Center, Toyama, Toyama, Japan
Toshihiko Sayama
Toyama Industrial Technology Center, Toyama, Toyama, Japan
Yoshiyuki Okamoto
Cosel Co., Ltd., Toyama, Toyama, Japan
Takeshi Takayanagi
Cosel Co., Ltd., Toyama, Toyama, Japan
Kentaro Uesugi
SPring-8, Japan Synchrotron Radiation Research Institute, Mikazuki, Hyogo, Japan
Takao Mori
Toyama Prefectural University, Imuzu, Toyama, Japan
Paper No:
IPACK2011-52047, pp. 443-451; 9 pages
Published Online:
February 14, 2012
Citation
Tsuritani, H, Sayama, T, Okamoto, Y, Takayanagi, T, Uesugi, K, & Mori, T. "Three Dimensional and Nondestructive Evaluation of Thermal Fatigue Crack Propagation Process in Complex-Shaped Solder Joints by Synchrotron Radiation X-Ray Micro-Tomography." Proceedings of the ASME 2011 Pacific Rim Technical Conference and Exhibition on Packaging and Integration of Electronic and Photonic Systems. ASME 2011 Pacific Rim Technical Conference and Exhibition on Packaging and Integration of Electronic and Photonic Systems, MEMS and NEMS: Volume 1. Portland, Oregon, USA. July 6–8, 2011. pp. 443-451. ASME. https://doi.org/10.1115/IPACK2011-52047
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