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PCB007-Apr2021

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98 PCB007 MAGAZINE I APRIL 2021 be AABUS." Many people, including PCB sup- pliers, claim that IPC-6012 accepts track weld- ing. is is not correct. It has been the rule for many years that any repair shall be AABUS. 4.3: "Deviation om IPC-6012E Quality Con- formance testing SHALL be AABUS." Very few suppliers follow strictly the quality confor- mance test requirements as mentioned in IPC- 6012E Table 4-4. I recommend checking with your factory to see whether they follow this re- quirement; if not, find out why. From my ex- perience, some of these tests such as Dielectric Withstanding Voltage, and Moisture and Insu- lation Resistance, are done once only. Some of the Rare Ones Some of the AABUS requirements are very special and rarely used, such as: nickel barri- er and electroless gold, electrodeposited tin, lead-free solder coating, and heat sink materi- al. "Deviations to 6012E SHALL be AABUS," which tells us there are many variations in the market and we cannot have all such variations into a general standard. Lessons Learned—Good Product Specification e lesson learned from reading all the AA- BUS references in IPC-6012E and A-600K tells me that the burden to secure a product in com- pliance with your requirements and expec- tations lies in a good product specification, where you have answered most of the AABUS references in the standard. By doing this, you ensure that the quotation you receive is in compliance with your design and product requirements, and that you avoid unwanted surprises when you receive the first boards. PCB007 Jan Pedersen is a senior technical advisor at Elmatica. To read past columns or contact The PCB Norsemen, click here. The electron is one of the fundamental particles in nature we read about in school. Its behavior holds clues to new ways to store digital data. In a study published in Nano Letters, physicists from Michigan Technological University explore al- ternative materials to improve capacity and shrink the size of digital data storage technologies. Ranjit Pati, professor of physics at Michigan Tech, led the study and explains the physics behind his team's new nanowire design. "Thanks to a property called spin, electrons be- have like tiny magnets," Pati said. "Similar to how a bar magnet's magnetization is dipolar, pointing from south to north, the electrons in a material have mag- netic dipole moment vec- tors that describe the mate- rial's magnetization." (Source: Michigan Tech University) Photo left: Chromium-doped nanowires with a germa- nium core and silicon shell can be an antiferromagnet- ic semiconductor. Catching Electrons in Action in an Antiferromagnetic Nanowire

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