Thermal Laminates: One More Tool in Your Toolbox

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Feature Interview by the I-Connect007 Editorial Team Jeff Brandman, president of Aismalibar of North America, discusses the company’s thermal materials and how they can help designers and engineers facing thermal challenges. He also details which segments are driving the development of these materials and offers tips for technologists who are new to dealing with thermal issues.

Andy Shaughnessy: Jeff, tell us about Aismalibar and some of your thermal materials.
Jeff Brandman: Thank you for having me. I appreciate the opportunity to speak to you. Aismalibar has been a manufacturer of PCB laminate pretty much since PCBs started being manufactured, and it has been involved in FR-1, FR-2, FR-4 materials, as well as CEM-1 and CEM-3. In the late ‘90s, Aismalibar saw that there was a huge opportunity in thermal management and became the first manufacturer to produce insulated metal substrates in Europe.

Shaughnessy: Give us some more info on the thermal laminates. What should a designer or electrical engineer look for, and what’s driving the development of these laminates?
Brandman: The largest segment for thermal laminates that we’re involved in right now is the LED market. LEDs have come a long way since they were originally introduced into the market. They’ve become extremely small and efficient, and the footprint that’s needed on a PCB for an LED right now is extremely compact. Even though the LEDs are becoming very small from a footprint perspective and efficient from a heat perspective, that just means that designers are going to cram more into a smaller space. As a result, the opportunity to move the heat outside of that area is extremely critical. A lot of our products at the moment are designed for this industry. A lot of our clients in volume use our products for the automotive industry.

If a designer is working on a board that you know has these thermal issues with LEDs or whatever it may be, how can these materials help that designer?
Brandman: Traditionally, many designers have been really focused on the thermal conductivity number, watts per meter kelvin. How much heat can you move in your PCB away from the LED? However, the thermal conductivity number is not necessarily the most important number because if you’re taking a single side of an application, where you have your copper,
dielectric layer, and heat sink, which could either be copper or aluminum, you want to move the heat from that active copper layer. If you find the material that has five mils of dielectric but has 10 watts per meter kelvin, on paper, sometimes designers get really excited about the super-high thermal conductivity number.
But the number that is important to focus on is either thermal resistance or thermal impedance, and where we try to focus our technology is to make that dielectric layer as thin as possible to be able to move the heat as quickly as possible. Sometimes, the thermal conductivity is not as high as 10, but with a solid thermal conductivity number and an ultra-thin dielectric layer, the opportunity to move the heat is
quite significant.

You mentioned that designers often over-design boards with thermal requirements, which makes the board more expensive and difficult to manufacture.
Brandman: As a laminate manufacturer, we get a lot of PCB shops reaching out to us. They say, “We have this drawing for this PCB. Which of your materials best fits this drawing?” A lot of times, I’ll see a specification in a single-sided material where the aluminum back or the copper back is a weird thickness. For example, a very common thickness for that copper or aluminum back is 1.5 millimeters, but then I’ll see people stack 2 millimeters or 78 thou, or 2.5 millimeters or 100 thou. What the designers may not realize is that although they may be getting a small percentage of other proof thermals for doing something like that, the
cost of the PCB could double or triple. Maybe you’re going to see 1–2% in the junction point temperature on the LED, but is it really worth all that extra money? Sometimes, designers design ultra-conservatively because
that’s their nature, and that’s good. But at the same time, more communication with the PCB shops and the laminate manufacturers could be really positive to value technology vs. cost.

Shaughnessy: It seems like you would have to communicate with the fabricator and the laminate maker when you’re dealing with these boards where you just see hotspots all over.

Brandman: We get a lot of designers from OEMs who reach out to us about their design, asking, “Which would be the best material to suit what we’re designing here?” In those cases, I make recommendations based on cost vs. technology. I try to remind them, “If you put 3-ounce copper here, that’s going to be a lot more expensive than you think. Is there a way that you can do this with two-ounce copper?” Most of the time, the designers are quite receptive to these recommendations.

Shaughnessy: If they’ve never dealt with this sort of material before, does it change the way the designer does the layout in any way?
Brandman: For a PCB designer who hasn’t had experience working in a heat application, there would be a learning curve, but many PCB designers who have experience with heat, whether it’s single-sided or multilayer, would be able to pick up the advantages of using these types of materials right away.

Shaughnessy: Automotive is one of the big drivers. I just read that automotive sales are up this year in North America, despite COVID-19 Do you see that?
Brandman: We’re involved in several North America-driven automotive programs in the full cycle, from supporting design, prototyping, and production. The year started really strong, where pretty much all of the programs we’re involved in were at either full capacity or close to full capacity. Then COVID-19 happened. Because automotive is not part of the critical supply chain, a lot of that business was completely shut down for 4–6 weeks.

April was a very scary month for everybody because no one really knew what was going on in the world and the impact COVID-19 was really going to have. Globally, when everyone understood where things are at with COVID- 19, the factories opened back up. When they opened back up, they didn’t go from 0% to 25%. They went from 0% to 125% because they needed to make up the time on these programs from having the factory shut down. Other than being shut down on these programs for a short period of time, it has been a very strong year, production-wise.

Barry Matties: On the automotive side, what trends do you see? We see a lot of e-cars coming out. How is that playing into your market? Do you see more demand in that area?
Brandman: We’re looking at that right now. We have people reaching out to us with respect to e-cars, but keep in mind the production of e-cars at the moment is only a small fraction of what gasoline cars are, so many of those opportunities are still in their infancy. And a typical design cycle for the electronics and automotive industry until it goes to production is a few years.

Matties: It seems like an emerging sector.
Brandman: There’s a huge opportunity for growth. There are a lot of opportunities for prototypes floating around right now, which is really in a power conversion side of things. The top market we’re focused on is LEDs. Power conversion is also another market where we do a lot of business, and that’s moving heat, but it’s really focused on electrical installation and assurance of that electrica installation.

Matties: Are the heat demands greater or less for e-car aside from the LEDs?
Brandman: Like power conversion, you need to have a solid dielectric to ensure electrical installation. You’re going to be able to move heat, but there are going to be some barriers as far as how much you can move because you need to have that electrical installation. On the lighting side, a lot of the high-end, high-power LED headlights work with a pedestal light design where the LED has an isolated thermal pad, and they’re putting the isolated thermal pad right on top of the copper heat sink. The electrical pads are still on top of the dielectric. They’re moving the heat from the LED right into the heat sink with no dielectric. The capability to move heat in that pedestal lighting scenario is significantly greater than in the typical power design because in power, you’re going to have pretty solid dielectric, and you’re going to be pretty limited by it.

There are also environmental aspects of thermal that will never go away.
Brandman: Typical automotive testing for laminates and PCBs is about -40°C to +125°C, and they do a lot of thermal cycles in this area. I’d say automotive is one of the markets where they do the largest amount of thermal reliability testing on the PCBs. It’s very hot in Arizona, but on the other side, people are driving the car in Alaska in the winter, and it has to work in both scenarios, no matter what.

Matties: That’s a tall order to fill. You mentioned more communication around the 74 DESIGN007 MAGAZINE I SEPTEMBER 2020 designers with fabricators and material suppliers. We’ve been hearing this for years. Is it happening, or is that still just a wish?
Brandman: It’s happening. We’re in communication with a lot of designers. They contact us all the time, but I also run into a lot of cases where the designs weren’t well thought through, and I wish that the designer had reached out to a PCB shop or a laminate manufacturer. Sometimes, designers design things that are great on paper but are not always great in reality. When you talk to front-end engineering people in a PCB shop, a lot of the time they’re going back to the customer, saying, “Can we change this on your design? It was really hard for us to manufacture that.” That’s pushing the limits on that process for anybody. Those conversations right now are mainly happening organically. There’s no formal communication. People are just designing something. They like our material or someone
else’s, and they go on Google to contact us out of the blue, which is great, but I’d love to be involved in promoting that communication.

Matties: How is everything going from a business perspective?
Brandman: Business is good, and our people are doing well. Our factories are in Spain. That was a scary time, especially when the [COVID- 19] numbers were going crazy in Spain, but we never closed or stopped going to the office. We were able to stay open, but we had to reduce our shifts and really be smart about it.

What advice would you give to somebody who is new to designing boards with thermal issues?
Brandman: My best advice is to reach out to your PCB shop and even reach out to the laminate that you’re specifying. When you’re designing, ask them if there’s any input that they would have specifically on the design that would be helpful. If that conversation happens, it will really help them in the long run.

Shaughnessy: Communication eliminates a lot of problems.
Brandman: Everybody has expertise and experience. When you engage other people who know what they’re talking about and what you’re trying to do, you’re always going to learn quickly.

Matties: Jeff, it has been great to catch up with you. Brandman: Thank you so much. I look forward to meeting you again when things look a little better globally. DESIGN007