Issue link: https://iconnect007.uberflip.com/i/1166358
SEPTEMBER 2019 I PCB007 MAGAZINE 13 standards. The DoD decided not to run it any- more, so they were taken over by IPC. They started off great when there were three or four resin systems, which was pretty simple, but things have moved on. Goodwin: Agreed. The way the specification is written has nothing to do with polymer/resin chemistry. Morgan: It was a conve- nient way when there were only a handful of systems. There was phe- nolic resin, which was generally married with paper as a reinforce- ment; there was epoxy resin, generally married with glass fiber; and there was the high-end polyimide, high-temper- ature resin married with glass. Everything was shoehorned into those three. It's entirely sensible the way it was set off, but not anymore. A specialist is not going to understand all of it, so as a designer, you don't have any hope. It's time to define what all of this stuff means. All that matters is how it works and performs. Goodwin: All that matters is electrical, physical, and thermal performance. Morgan: The rest doesn't matter at all. We're looking under the hood too much, specify- ing chemistry and all kinds of stuff. But who cares? You need to be able to categorize it somehow. Goodwin: A simple first step, though, would be to move to the performance characteristics we already have around electrical and thermal performance, and remove this link to the un- der-hood, the resin chemistry. That would be a very big and relatively simple step to take with no performance risk for the end user because the performance is defined. Morgan: Yes, the military is hesitant to change, but people in the automotive and electromobil- ity segments are interested. Designers want a bit of help. I gave a talk/consortium in Janu- ary this year, and it was fantastic. There was a great group of people there who wanted to hear something about this because they look down the standards list to try and pick the ma- terial for an application that's going to work. They don't know because there's such a range of materials. You have thousands of them now. Somebody could say, for example, "We're an automotive OEM, and we want an international standard that we can use rather than using our industry-specific standards. We have one group that we call under-hood, one that we call cabin, and one that's mission-critical." Then, you de - fine within the industry the areas of concern; under-hood, for example, would need to have a high thermal performance. As an industry, you could say to the designers, "What do you need?" and they would come to that kind of group. You would have confidence that it would work. Goodwin: I'm sitting here counting up the num- ber of slash sheets in IPC-4101, I'm up to 97, and now I'm giving up. If, as a designer, I have an interest in epoxy woven glass, and there are 21 slash sheets or more for epoxy woven glass. How am I supposed to work my way through that? This is the problem, and if, for example, we took the resin chemistry definitions out of the specification, you take away half of these slash sheets in one go because there will be one brominated epoxy and one unbrominated epoxy for each Tg range. Andy Shaughnessy: Designers can't possibly know the differences between all of them and understand them all, and they're not all manu- factured with the same process. Goodwin: Right, and not even a laminator could decipher this. If you put six members of the IPC Materials Committee in a room, you'd have at least seven opinions. Morgan: It's impossible, and that's the issue. These standards came out of the old DoD MIL Mark Goodwin