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Show-and-Tell-2020

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REAL TIME WITH... IPC APEX EXPO 2020 SHOW & TELL MAGAZINE I I-CONNECT007 119 is critical for realizing the best performance and alleviating any signal loss. The paper discusses an innovative nickel-less approach involving a proprietary nano-engineered barrier designed to coat copper contacts, then finished with an outermost gold layer. This new technique has shown superior results in realizing the opti- mum performance and in providing better reli- ability for electronic assemblies. Right away, I would also like to thank and acknowledge John Coonrod and his team at Rogers Corpo- ration for their assistance with insertion loss testing and invaluable technical discussions. Johnson: In your paper, you detail a nano-coat- ing to create a nickel-less process. How does that work? Shah: The nano-engineered barrier layer is designed to passivate the copper substrate. This prevents diffusion through the gold layer to the surface and ensures wettability, even in harsh environmental conditions or through multiple reflow cycles. Moreover, the barrier layer prevents diffusion of copper atoms into the solder during the reflow process to ensure a thin intermetallic layer. This results in robust solder joints for better reliability of electronic assemblies overall. Johnson: How did you come up with this par- ticular coating? Shah: My background involves nano-engineering of interfaces and materials. I have been involved in the electronics materials area for more than two decades. Because I understood the chal- lenges faced in the area of electronics reliabil- ity, we knew the solution to improve electrical performance/signal integrity and improve reli- ability was essential. We have been working on developing these solutions for a few years now, along with the support of a U.S. federal agency, the National Science Foundation. It will be inter- esting to see how PCB manufacturers, assem- blers, and OEMs put this technology to work. Johnson: What motivated you to do this research? Were you responding to pain points? Shah: Currently, there are two main pain points. As the electronic industry overall moves toward high-speed, high-frequency applica- tions (i.e., 5G, automotive, aerospace, medi- cal electronics), one pain point is signal loss as the frequency increases. Another pain point is reliability concerns, especially brittle solder joint failures. We have addressed both of these issues with this technology. It provides opti- mum signal integrity as well as offering better reliability with robust solder joints. Johnson: What were your test methods? Shah: Our test methods included insertion loss testing (conducted in conjunction with Rogers Corporation), contact resistance testing to evaluate for copper diffusion, solder joint evaluation through cross-section and electron microscopy, and shear test-pull test (according to JEDEC standards) to evaluate the robustness of solder joints. I encourage readers to access the paper to learn more details. Johnson: What do you see as the most impor- tant industry implications from what you've published? Shah: This technology has direct implica- tions for high-frequency applications; mobile devices/networks (e.g., 5G, 6G, and onward), automotive electronics, RF/microwave appli- cations, space/aerospace applications, etc. Johnson: Will there be further research? Shah: Yes, there will be. Our ongoing research involves fine-tuning the solution to cater to specific applications and the industry. We will continue to explore next-generation surface finish solutions for better performance and reliability of electronic assemblies, which are also cost-effective. Johnson: Thank you, Kunal. Shah: Thanks for the opportunity. S&T

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