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June 2017 • The PCB Design Magazine 15 A DEEP LOOK INTO EMBEDDED TECHNOLOGY Brandler: Yes, two things are happening: more microphones for noise cancellation to improve sound fidelity; and second, more layers for the same reason of resistive layers and capacitors. And we're still pushing on this combined prod- uct, although most of the capacitive layers and resistive layers are separate. But what you must have is both capacitors and resistors to create a filter and part of the problem of miniaturiza- tion is, if you look at a laptop, the high-speed end of it is rather far away from whatever audio stuff is going on, and the digital is in the mid- dle. But as you then squeeze it down to the cell- phone size, things get a lot closer together, and if you squeeze it down further to an ear bud, now they're right on top of each other. And all that RF interference is going right through the digital circuits. You must have a way of dealing with that and one of the ways is to put the capacitive layer right below the resistive layer to elimi- nate noise. This is where signal integrity, this is where the fact that things are all on top of each other at very high frequencies, there's all this crosstalk and parasitics going on that must be dealt with. As a result, the inevitable drive for higher densities and higher frequencies has caused the need for more applications of these embedded paths and layers, both resistive and conductive and capacitive. So it's really a design thing. I would say the driver for us now is high- er frequency, smoother copper. There are also some issues in the supply chain. The standard coppers are available in the States, but some that drives down the thickness of the resistor material, so it becomes thinner. The identical alloy that you had 10 or 20 years ago, say at 25 ohms per square cm would be 0.4 microns thick; now it's down to 0.2 mi- crons and on its way down to 0.15 microns. The only difference is the surfaces are very smooth and it's driving down resistivity. At the same time the question is: how do you improve the bond strength? Because when you get these very smooth surfaces, the bond strength starts dropping and then you're subjecting the PCB to thermal shock and so forth. The lower bond strength then turns into a reliability issue, so these two worlds are kind of like colliding. The high-speed digital is getting faster and so is the RF. Basically the bottom line is we all know about Moore's Law, but there's also this frequency thing. If frequency is increasing, it is inevitably driving down the thicknesses of these embedded layers because of the need for smoother and smoother conductors. And that's where we are now. We're look- ing at copper foils that we're going to be plating on and we're looking at chemical solutions, be- cause it's not going to be mechanical, improv- ing bonds so that we can use these very smooth conductors. We have an R&D program now di- rected at that, and it's what we think is the next big thing coming along. I don't see that stop- ping at all. Meanwhile we are very busy; 2015 was our record year. There was a slight downtick last year, but this year we think we'll beat that. Cer- tainly, year-to-date, we're in record territory in terms of business. Mostly driven by the com- bination of aerospace defense increases and the commercial has also increased. It's not that they're going to sell that many more cellphones, but we're in the China market as well as the U.S. market, and they're using more microphones per phone. Plus they're using more layers, like one to two, but to go from one to two layers per PCB doubles it right there. We're really seeing a huge upswing in these applications. Matties: For the increase, if I'm hearing you right, you're saying that people are coming in and doubling up on your material in the same application for the same board? " This is where signal integrity, this is where the fact that things are all on top of each other at very high frequencies, there's all this crosstalk and parasitics going on that must be dealt with. "