electronics: very low loss or ultra-low loss materials with suitable Dk and Df values. These materials are normally a bit more brittle and not that robust regarding micro-cracks like the traditional materials. Taking into account the known failure modes like CAF or microcracks, this could be challenging. In the automotive environment, temperature cycling and temperature storage are important parameters. But it is the humidity for which we have to be really careful. Vehicles have subsystems that are always on with low power consumption. There could be electrochemical migration in these systems. If you have to use these new materials due to the high-speed electronic requirements, then we have to be very careful. Therefore—at the moment—we have solutions, but for the next generation with bigger bandwidth and higher frequency, we have to go to other materials, and these have to be qualified.
Matties: Are you looking at the cleaning stan-
dards and changing the requirements as you talk about the electrochemical migration?
Klein: Cleaning is always discussed because
cleaning is quite difficult. The problem is that up to now nobody can offer the perfect cleaning solution. After assembly, some of the solder paste residuals could stay in small gaps below the QFPs and other components. That is very difficult to clean perfectly. Regarding the bare PCB itself we do not really see a problem. What is still on the board after the PCB production will evaporate during first reflow. Thereafter, it depends on the use case. If a designer makes the housing of the PCB quite tight and uses a pressure compensation element, the warm and humid air does not get directly onto the PCB itself, and dewing can be avoided. Therefore, we must be really careful in designing our units that dewing of water will not happen. Cleaning has not been a big topic because we use a specific design of our control units to avoid this dewing. 12 PCB007 MAGAZINE I MARCH 2021
Christian Klein
Matties: When you’re designing the actual circuit board? You’re taking that into consideration?
Klein: Yes, by designing the circuit board and
the housing concept. More important than the board itself is the housing. It could be in the future that we have to use some fans to cool the electronics from the outside. That will change the game. Then we will need protection methods, specific components or a protective coating on the PCB. But up to now, we try to avoid this by designing a proper housing of the electronics.
Happy Holden: Which is going to be the bigger
challenge in the future: Finding the right materials that have the appropriate cost levels, or finding the right fabricators that can consistently produce quality products if they can get those materials?
Klein: That is a very interesting question because the automotive market is under a great deal of cost pressure. We have to be careful se-
