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PCB007-July2019

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26 PCB007 MAGAZINE I JULY 2019 copper morphology was reported to increase copper hardness and decrease ductility [3] . The features—those identified in the cross-sections and SEM photographs through which fractures formed and propagated during assembly re- flow thermal stress—coincided with failures. Chemical species analysis at the copper sur- face of the target pad of an actual microvia af- ter laser drill was not possible due to microvia sidewall, outer layer copper, and sample prep- aration interference. Further investigations are encouraged. Probability plots of UV-CO 2 and UV laser- drilled microvias indicate the UV laser-drilled ones frequently fail during the first reflow pass while stacked microvias formed by CO 2 laser processes survived up to 30 reflow as- sembly cycles. This suggests the UV modified copper surface of the target pad results in a weak interface that fractures during reflow assembly. Until the root cause of stacked microvia fail- ures is determined and problem solved, stag- gered microvias must be used for mission critical and high-hazard environments. The window for staggered microvias is closing as the reduction in pitch and increased circuit density forces the use of stacked microvia con- structions. PCB007 References 1. Magera, J., et al., "IPC-WP-023," May 2018. 2. Inaba, R., Kawamura, T., Akahoshi, H., Arai, K., "Stud- ies on CO 2 Laser Drilling: Formation Mechanisms of Residu- al Thin Materials at the Bottom of Laser Via," IEEE Transac- tion on Electronic Packaging Manufacturing, Vol. 24, No. 1, January 2001. 3. Duley, W. W., UV Lasers: Effects and Applications in Materials Science, University of Waterloo, Ontario, Cam- bridge University Press, 1996. 4. Zhang, J., Wang, Y., Cheng, P., Lawrence Yao, Y., "Ef- fect of Pulsing Parameters on Laser Ablative Cleaning of Copper Oxides," Journal of Applied Physics, Vol. 99, No. 1, 2006. This paper was first presented at the IPC APEX EXPO 2019 Technical Conference and published in the 2019 Technical Conference Proceedings. Jerry Magera is a senior staff chemical engineer in the Motorola Solutions Qual- ity and Reliability Group and the vice chairman of the IPC D-32 Thermal Stress Test Methodology Subcommittee. J.R. Strickland is a senior quality manager with Motorola Solutions Inc. in the Applied Technology Business Unit. Recently, our industry lost one of its veterans—Greg Beck, owner of Beck's Light Gauge Aluminum Company. He passed away unexpectedly in Lake Zurich, Illinois, on May 2, 2019. He was a passionate and committed execu- tive who built a successful business around thin-gauge steel and aluminum processing for high-technology appli- cations. The company was founded by George Beck, Greg's father, who was also very prominent in the industry. Last year, Greg and his company joined the Insulectro family of com - panies through acquisition. Greg's pioneering work with American-sourced aluminum was a perfect fit for Insulec- tro's line of business. We appreciated Greg's enthusiasm for the blending of the businesses and his guidance and di- rection as he stayed on to continue his extraordinary work. "On behalf of all my fellow teammates, we celebrate Greg's life. We salute the successes Greg accomplished for our industry, and we pay tribute to his visionary legacy which will remain a guiding light in our business. Insulec - tro will name its light-gauge metal processing line in both our Chicago-area and our Orange County, California, facili- ties in honor of Greg," Insulectro President and CEO Patrick Redfern commented. "Our thoughts and prayers continue to be with Greg's family and friends, and the business col- leagues who knew him and worked with him and recog- nized his genius." (Source: Insulectro) A Tribute to Greg Beck

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