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PCB007-Aug2018

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48 PCB007 MAGAZINE I AUGUST 2018 the AREA Consortium (Advanced Research in Electronics Assembly). This is a comprehen- sive evaluation program for assembly process- ing including lab research, text vehicles, metal- lurgical evaluations and reliability evaluations, including a full scope of environmental stress testing (ATC, drop shock, vibration, thermal shock and corrosion). He relayed to us many of their findings after doing extensive assem- bly level testing for solder joint reliability that included: Mechanical robustness • Isothermal shear fatigue • Drop shock testing • Vibration testing Thermomechanical reliability • Environmental thermal cycling • Thermal shock (air-to-air, liquid-to-liquid) • Power cycle Included were the effects of various PCB surface finishes and various components like BGAs, LGAs, TBGAs and QFNs of various pitches and ball configurations and sizes. The number of slides was impressive and num- bered over 50. Suffice it to say, the AREA Con- sortium is testing most of the variables that are used in lead-free assembly today for their ef- fect on SMT reliability. The last talk of the conference was by Rich- ard Bellemare of MacDermid Enthone Elec- tronics on "A Review of Metallization Interfac- es on Microvia Reliability." Rich entertained us with a compelling talk on factors affecting reliability of microvias and the interfaces encountered in microvia processing. There are numerous fac- tors contributing to micro- via reliability: • Number of vias, stack/ staggered, and level of the via within panel • Via size, aspect ratio and shape • Drilling and microvia shape • Cleanliness of the target pad and desmear • Type of primary metallization • Quality of the primary metallization • Quality of the secondary metallization • Plating processes • Via filling • Test methods—thermally induced stress Bellemare then went on to discuss how crit- ical the understanding is of each process and the underlying steps of each process. Although he could not pin down the 'root cause' we were talking about over the last two days, it certainly educated us as to the complex nature of finding such a root cause. It was a fitting end to two days of presentations and discus- sions about microvia failures and other SMT failures. PCB007 Happy Holden is technical editor with I-Connect007. To read past columns or to contact Holden, click here. The BGU researcher draws his inspiration from the 1960s movie "Fantastic Voyage." In the movie, a shrunk- en submarine swims through a scientist's bloodstream to repair his brain. "You can call it a gut bot," says Dr. Zarrouk. Source: Ben-Gurion University of the Negev Dr. David Zarrouk, director of Ben-Gurion Universi- ty of the Negev's Bio-Inspired and Medical Robotics Lab carefully places the tiny robot into a cleaned-up pig intestine on his table and flips on the switch. About the size of a thumb, the miniature robot comes to life and starts worming through the intestine, all the way through the other end. Robots Are Racing Through Our Blood to Cure Disease Richard Bellemare

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