Issue link: https://iconnect007.uberflip.com/i/1350598
32 PCB007 MAGAZINE I MARCH 2021 ey normally ask us to offer them the best solutions, which are always focused on two main aspects. First, what Aismalibar can offer in terms of releasing heat from the electronics through metal PCB boards. at's one direc- tion. e other direction is how much power can be applied to these inverters, AC/DC con- verters or DC/DC converters, granting the di- electric strength at the initial point and through the aging of the material. is is a big topic to- day. Let me give you a very clear example. When designers want to increase the power of the boards, they normally tend to increase the voltage up to, let's say 600 or 800 volts constant on a power module. By applying this much current through such a thin dielectric layer, their main concern is how to keep the dielectric strength during X amount of thousand hours, combined with high temperature and high humidity. ey are concerned with how to keep these high volt- ages running on the devices, and at the same time, keep the device stable and capable of run- ning for a long time. is is a challenge today. Our R&D team is working very hard on how to achieve these goals, to avoid copper migration and other aspects that influence the long run of the dielectric layer in a metal PCB board. Johnson: You touched on just a couple design and reliabili- ty challenges. What other chal- lenges are you working through? Benmayor: Mainly, it is the mis- match between the metal PCB boards and the solder. e mis- match is big and as temperature changes are big the problem tends to appear faster than in other electronic designs. Pow- er boards on vehicles are operat- ing at -110°C to +120°C, and this generates a very big mismatch between the metal core and the solder joint; the solder is affect- ed, and we are challenged with reducing this mismatch and giv- ing a longer lifetime to the solder joint. It's a constant challenge, and we see customers tak- ing different directions. Copper migration on metal PCBs is a chal- lenge that has only come up in the past year. It appears faster when we apply a high current through the functional copper and at the same time apply high temperature, 65-70°C with constant voltage around 1,000 V, and humidity in the 95–98% range. When these conditions happen over a long period of time, say 1,000 to 2,000 hours, we start to see copper migration. is is well- known in the PCB industry, but with these high currents, we see the migration growing much faster than with the standard electronic PCB designs. We have dedicated people working on the recent technology as there are many different ways to approach the reduction of copper mi- gration. Our approach, generally, is to increase the Tg of the polymers used in our laminates. By increasing the Tg, we normally see a reduc- tion in the copper migration. is is one thing we see right now and which we have tested multiple times. A second approach is to reduce the ionic charges on the resin, which is easy to An example EV drive train and battery platform.