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68 SMT007 MAGAZINE I OCTOBER 2018 Article by Ranjit Pandher, Matthew Siebenhuhner, Gyan Dutt, Mitch Holtzer, T.W. Mok, Amit Patel ALPHA ASSEMBLY SOLUTIONS Abstract Solder voiding is a common phenomenon across all semiconductor packaging and elec- tronic board assemblies. Voids are a trou- blesome defect in assemblies created using surface mount technology. Voids can interfere with electric signals, can be insulators when heat dissipation is required, and they can also be the source of crack propagation and early failure of an assembly when occurring near the pad surface. The acceptable levels for void- ing vary upon on the end-application and envi- ronment it's used in. In the case of thermally demanding harsh environment applications such as automotive and outdoor LED light- ing void control is required in order to opti- mize the performance and extend the lifetime of these components. The lower the voiding on these thermal and electrical pads, the better the connection to the PCB and subsequent layers. Process, Design and Material Factors for Voiding Control for Thermally Demanding Applications There are many factors that influence void frequency and size. This study focuses on several process, design and materials selec- tion considerations which control or poten- tially reduce voiding to meet industry and end- market acceptance criteria. More specifically, package design, reflow profiles, and solder paste chemistry are discussed in the form of application studies. Commercial mid-power PLCC and high-power ceramic LED packages on aluminum metal core PCBs additionally BGA, D-Pak, and MLF on FR4 PBCs were used for these case studies. Introduction The global acceptance of LED-based light sources has propelled the energy efficient technology to enter numerous markets and end applications including high power light- ing segments. Examples include exterior auto- motive headlamps, roadway/street lighting, industrial high bay lights, architectural and entertainment lighting. As a result, customer expectations of maintaining efficiency, govern-

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