PCB Thermal Design Deep Dive with Ethan Pierce

Welcome to the Altium OnTrack Podcast! Today, we are joined by Ethan Pierce, founder of Dodec Labs. He and host Zach Peterson explore the intricacies of thermal management in PCB design. If you’ve ever faced issues with overheating PCBs or want to enhance your PCB thermal design skills, this episode is a must-watch!

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Episode Highlights:

• Importance of early thermal problem identification
• Effective PCB THERMAL DESIGN and simulation techniques
• Real-world examples and lessons from PCB East
• Strategies for optimal heat dissipation and management
• THERMAL DESIGN OPTIMIZATION Insights from industry experts

More Resources:

• Follow Ethan Pierce on LinkedIn
• Reverse Engineering Deep Dive
• Pierce Design's website
• Thermal Conductivity and Thermal Management for Printed Circuit Boards

Transcript:

Zach Peterson: If you had done a little bit of homework on the front end and maybe found a more efficient circuit, or, you know, identified that thermal problem in specific areas of the design early, you probably wouldn't have these issues with. Now my enclosures in oven and my skin temperature is so hot, I can keep my coffee warm.

Ethan Pierce: I had made this hypothesis with my self where I had said, okay, well I've got this aluminum board for this high current LED driver. And I, I made this design decision to say, oh, well, like, I'm just gonna throw a bunch of these vias at the top of this board because in my mind I want to be able to have convection currents move through to pull the heat. But what I ended up finding out from the thermal simulation is that it didn't do anything. If anything, it made it worse.

Zach Peterson: Hello everyone. Welcome to the Altium OnTrack podcast. Today we're talking with Ethan Pierce, founder of Dodic Labs. Ethan was also recently at PCB East and I'm excited to catch up with him after the conference. Ethan, thank you so much for being here today,

Ethan Pierce: Zach. I'm really happy to be on the podcast again and it was great to see you at the conference.

Zach Peterson: Yeah, I, I was a little late, so I didn't catch everything. Unfortunately, I didn't catch your talk with Thomas Chester and there were some other folks I wanted to see who unfortunately I missed 'cause I had a little detour through Canada on my way there.

Ethan Pierce: Well, at least we got to catch up towards the end. There were some really interesting talks. Early on in the week, there was a talk by Charlene and Terry. They were the design team that did the first CAM DDR five modules and they also participated in designing the cam, doing the feasibility studies on the CAM two modules. So there was a lot of interest in, hey, like, tell me more, like how did you decide what the stackup was going to be? And like, we had a lot of discussion including, you know, with the, the, the legends like Rick Hartley were having a whole conversation about, so dim how it still exists and the transition to CAM and why you need to keep the traces really tight. That was a big highlight this year. There was A-U-H-D-I forum, which included a ton of talks from some very prominent businesses, including people from KLA. I look forward to being able to go to those talks. I, because I'm a designer, I, I prioritized kind of sticking with the classic tracks of investigating more on ddr, single integrity, some refreshers from Rick Hartley. And then also talking about the, the content that Thomas Chester and I were, were discussing, which was thermal design with PCBs.

Zach Peterson: Yeah, we don't talk about thermal enough on this podcast. And I think if you look typical design conferences and you look at the agenda, there aren't usually a lot of talks on thermal. And I think a lot of designers are just like, well, you know, if it's too hot, turn down the current and throw a heat sink at it.

Ethan Pierce: Yeah, I, you know, there was, there was the talk that Thomas and I gave and there was one that I, I think Saeed had given about thermals. But one of the things that I think is interesting about thermal design is just like any other design cycle that you're going through, you should really think through it as a staged cycle and kind of jumping between phases rather than the context of, okay, well we have this hard requirement and then we need to, we need to solve it within these defined bounds. The challenge when you do that is that you don't build an intuition of what are other factors within my design space that I need to adjust?

Zach Peterson: So factors such as

Ethan Pierce: Factors such as thinking through what your, your TDP and your EDP is for your, your system. A lot of the times as a hardware engineer, either you or somebody else on a product team is going to define what the, what the, the architecture is going to be in terms of are we building a mobile device that's a notebook, is it a phone? Sometimes it's a desktop, but typically just for the sake of the context for this conversation, we'll kind of think through like mobile, like laptop kind of devices. So you'll be stuck with, okay, well what's the class of devices this a workstation? Is this a like a, a thin and light notebook? And then you'll have sort of these hard requirements, right? Like if you wanna build something that's been enlightened, doesn't have a fan, all of a sudden there's a certain limitation in how much heat you could dissipate. The biggest challenge is, is is two things. One is you have to be able to get the, I mean there's a ton of challenges with it, but you have to be able to get the device to stay within the operating temperatures for the system. But you also have to stay within regulatory compliance. That's why, you know, if you look back at some of the older MacBooks, that first gen MacBook that had the single port with the intel chip in it, one of the hardest problems that they had was that they couldn't keep, it was very difficult to keep the skin temperature low enough. And the problem is because there was no fan, it was dissipating heat through the body is the performance would get throttled aggressively. And when you wanna keep it below 60 degrees C, you have to do a lot of limitation limiting things in your system bios and in the hardware so you, so you don't burn people. But that's just like one thing to think through is, hey, I've got these, I have a constraint of, I have so much thermal energy that I can dissipate in the system and I have so much energy that I need the system to consume. A lot of the times people have to jump quickly to like, oh well, like let's just add a blower. But the complexity is if you add a blower, it adds a lot of mechanical engineering, it adds a lot of electrical engineering, even there's some firmware and also simulation and it can blow your power budget. So it's important to think about, well what are the inputs from the design team? And I talk a lot about sort of this thermal design engine that I learned from a very well-respected designer Joe Mooch, where we kind of go through this flow of getting rough cad doing these preliminary estimates, doing these back of the napkin calculations and having those feed into doing some CFD simulations once we have more bounds around things. And then before we even release manufacturing files to a fabricator, we're cutting bare copper clad, we're using copper blocks, we're hooking things up to power supplies to simulate what the actual system's going to be. And then we can go ahead and, and collect a lot of that data either through a thermal camera or temperature probes and feed that back into the design cycle.

Zach Peterson: Yeah, the biggest problems I've had in this area and working with like a mechanical engineer, whether, you know, with a client or with just a collaborator is something you brought up, which is the form factor constraint. Because if they don't figure out what they can do early, they just say, well this is the form factor we want 'cause it looks cool and then we're gonna go on a shopping spree and put as much stuff in there as we can and then all of a sudden, oh our skin temperature is hot enough to boil your coffee.

Ethan Pierce: Yeah. And, and I think that that's, that goes in line with thinking about the design space because if you define that upfront and it's so concrete and you're not willing to flex it, then, then you have no opportunity to really change other things in the design that might be switching to a lower power transmitter that might be changing how, how you're switching your, your power rails. That might even turn into, well how are you moving heat within the system from a, from a mechanical architecture, like where is the intakes and where, where are you moving the air out? Even if you're doing passive convection cooling.

Zach Peterson: Yeah, the, the airflow issue comes up whenever I've had to, to deal with that and at some point they're just like, well now we gotta modify our enclosure to put a fan on it. And then they're blowing past that constraint and sometimes it just looks weird. 'cause they'll mount a fan on the side and they'll try and put fins around it to make it, you know, look sleek like they planned for it to be there. But you know, of course those of us that worked on it know that was not the intention at all. Then they have to cut a hole somewhere else for the outlet if they even do that. I've actually had that problem where they're like, well, you know, we're just gonna put a fan up here now we need you, Zach, to add the fan control circuit. Oh wait, there's no room on the board for that. That's a whole other problem.

Ethan Pierce: Absolutely. And then like you've got the fan control circuit, now you have the sourcing, now you have all this other complexity and testing challenges. But one of the things that i I I wanted to do for hardware engineers is a lot of the times the way you described it is it's this opaque thing to, to a designer. And so one of the things that I did for, for P CCB East was I went ahead and I, I worked with a thermal engineer who had worked at some of the telecom companies who had done like modems and network switches and he was a thermal engineer and I was like, okay, like I have, I have hardware for the hardware company that I, that I started. Let's go through some thermal simulations. The best part is the design is, is very simple. It's just a, a single high powered LED on a board. You've got one input at five and a half bolts. And the powerful part about that was we walked through what a thermal simulation was and I understood how to, what the inputs are for the system, what is meaningful to the thermal engineer in terms of how the computation happens. And then actually looking at some of the data and a lot of the times as a hardware engineer, like somebody just tosses it to you over the wall, right? Like somebody just tells you, oh, you need to fix this. But it's like again, the more you have an intuition for, oh this is kind of how heat moves and these are the inputs that somebody on the thermal team and what are they thinking about that drives better design decisions.

Zach Peterson: I think at some point you have to go back to the fundamental circuit that you're working with because if that's the big creator of heat, there may be an opportunity there to optimize something. One of the issues I've found in power systems is that one of the regulators, for example, could be optimized and it just never was. Or it was an off the shelf module and that module is now getting too hot and they never go back to the fundamental, you know, what could we have done different at the start rather than, oh no, we have this enclosure and this enclosure is an oven, how do we deal with this? And just put a bandaid on it because the, the bandaid is, is the quick and easy way and you know, it's, it's fast but it's gonna probably make your design look look silly. Whereas if you had done a little bit of homework on the front end and maybe found a more efficient circuit or you know, identified that thermal problem in specific areas of the design early, you probably wouldn't have these issues with. Now my enclosure is an oven and my skin temperature is so hot I can keep my coffee warm.

Ethan Pierce: When you're, when you're looking at power systems, having the understanding of, well where is all of my heat being dissipated? Especially when you're doing your layout thinking about not just appropriate component placement, for example, when you have your switcher and you wanna keep your inductor and you wanna keep that loop from the switching end of your DC DC regulator as close to those pins as possible, you know, as a, as a designer, not just on the schematic side. Thinking about the board structure, you know, I, I had, I had made this hypothesis with myself where I had said, okay, well I've got this aluminum board for this high current LED driver and I, I made this design decision to say, oh well like I'm just gonna throw a bunch of these vias at the top of this board because in my mind I want to be able to have convection currents move through to pull the heat. But what I ended up finding out from the thermal simulation is that it didn't do anything. If anything it made it worse, but not for the reasons that I had thought. I had thought that okay well if I have these little holes in the board, it's going to be able to move it through convection. The challenge is that that barrier between the aluminum board and the hole where air is passing through for heat to be able to transfer that heat coefficient is it doesn't transfer very well. And so the heat for the board is going to migrate to everywhere else in the aluminum and heat up the rest of the board before it even gets to penetrating through those little vias and moving air through there. And we found that through in the thermal simulation.

Zach Peterson: Yeah, at some point you have to back that up too with a thermal measurement, right. And I think people have, you know, two tools at their disposal for that, right? It's placing some thermocouple probes everywhere and trying to monitor the data all at once, which I think is cheap. But then it takes a DAC unit and you gotta write a program for it so cheap, I guess an investment but maybe takes a little bit of time or just throw a thermal camera camera at it.

Ethan Pierce:Yeah. And you know, there is some really nice thermal cameras that exist. There's some from FLIR seek. One of the things that, that I actually use is I, I have a seek camera from when I did the iPad rehab micro soldering class with Jess Jones and it's this seek thermal camera, but it has a macro lens on it so that you can actually inspect boards and what is normally a test where you're checking for shorts and you kinda do this little tap tap test on the power inputs and you can see where the temperature rises on the board all of a sudden this is incredibly valuable for me as a designer, I can go take that same camera with this macro lens and I can go grab thermal data. And what's cool is, is a lot of these, the cameras, they actually, they will superimpose, sometimes they'll take the, just the regular camera image and they'll superimpose the thermal image data. The SEQ one actually has the high enough sensor resolution where it's collecting enough data and you can go ahead and in post you can go look at the different data, you can take videos, pictures, but the cost of access to get to this data, the bar is so low now, which is, which is fantastic. Now I I will say the, the bar to like get to the simulation, I think that that's still opaque because there's not many thermal engineers that I've interacted with or know. And then in addition, the tools are wildly expensive and out of reach for, for many people. I mean I think the gold, the gold standard is, is still ansys fluent for their CFD, but in addition to having the six figure tool, you've gotta have close to a six figure workstation and people pay pay accordingly for that work. Now I think companies like Autodesk have done a great job in terms of, you know, you have, everyone has their own feelings about how, you know, pay per use software is rather than perpetual. But for the CFD stuff to be able to pay, you know, to bound a project to be a few days and have it be a few hundred dollars, that's very economical for a business that's just trying to get some thermal data to make a decision where they can go back and and make changes.

Zach Peterson: You know, you brought up the thermal engineers, I don't think I've ever seen a job title for thermal engineer. I think it usually BRI gets, gets lumped into the mechanical engineer, right? Because they're gonna be the ones designing the enclosure anyways, right? So it makes sense that they also have to do the thermal side of it and that's when they start doing the CFD simulation, they start doing, you know, conduction cooling simulations, that kind of thing.

Ethan Pierce: It, it's, it's funny because in the organizations that I've worked with, the, the mechanical engineers or the product architects, they would kind of dabble in it but they hone they would give it to somebody else who, who understood it better, who understood how to drive the tool, who understood what they were looking for. And yeah, even the, the last project that I was working on with a radar system, the mechanical guy like, oh there's, we gotta go talk to this thermal engineer. Like I don't know how it works, I just give him the CAD and I give him the inputs. That being said, I think it is really interesting to think about the way that the CFD tools work in terms of doing the computation. So as you have more complex geometry, it actually makes the simulation take longer because you have more points along a mesh that need to be computed. And traditionally, you know, when whenever we look at doing things with CAD models, it's like it's gotta be higher resolution, give me more, give me more detail in it. And all of a sudden when you start running through a CFD simulation, the lowest effective resolution that you can give for a model and still get relevant data, that's where you want to be. You don't wanna be using a more complex mo a more complex geometry in order to generate that. Another thing that I wanted to mention that I think is interesting is there are, there are tools in different CAD packages. Like I know that this exists in Altium with the MCAT co-designer. And this is really just to point out I, where I think things are moving is to be able to get copper into a CAD tool, into a mechanical CAD tool and be able to run a thermal simulation on it. Because right now the way that it works is we've got the, right now the way it works is we've got this system and you have your key components with the heat that's going to be dissipated and the thermal engineer is going to basically assign values to those components, but then for the board and the substrate, they just basically say, eh, it's kind of this, it's this average thing. So they give it a value of FR four or they give it a value of whatever the IMS material is. But we don't yet have, it's sort of newer in the industry, at least from when I've interacted with teams is okay, now we have the opportunity to get the copper and via structures and as we have devices that are going into these miniaturized sips and chips and you've got chips that are stacked on chips with substrates, all of a sudden this is now valuable where I have copper and I have my copper and via structures to be able to get that data into a CAD tool and run A-C-F-D-I, I think we're going to see over the next five to 10 years, I think you're gonna start to see simulations get much more detailed and start to look at, okay, well how is over time in these short windows before we get to steady state, where is the heat flowing? I mean it's important for battery systems when you build battery controllers to understand like, yeah you might have three FETs that are rated up to 30 amps each and you've got 60 amps flowing through the copper, but if you don't set up your copper such that the way the current's going to flow for those fields is going to hit all three of those vets at the same time, you're gonna blow up the first one that it hits. And I think we're going to start to see teams doing more detailed thermal simulation as designs get more compact and miniaturized. Every single piece of copper is going to matter, every single component, every single ball, it's going to start to matter as we continue to drive down the power consumption.

Zach Peterson: Yeah, that's interesting you bring that up because I think a, well if you look at what a thermal engineer does when they're building a simulation, they take a lot of pains to simplify the geometry and it's, it's partially 'cause of the reason you brought up with CFD, right? If you can make the model simpler and in doing so you're making your mesh simpler, reduces that computation time and you can do so without sacrificing the accuracy in the region where you need it. Which is essentially, you know, in this case airflow prediction and then what's the temperature along that airflow,

Ethan Pierce: You know, that's where it's important as the, as a designer to or understand like, okay, they're gonna do the simplified geometry. But it's important to note that if you do have something that's more complex, which I, this is something that I'm just realizing now is as a designer there may be times when you want to call out a geometry that's, that's important or a section of the board that's important in addition to not just the detail in that geometry for the CFD meshes that are on the board calling out where hey, maybe we want to get a higher density mesh so that we can get, we can get a better map of actually how heat's gonna flow in this section.

Zach Peterson: Yeah, yeah. I, I agree. And one thing that's, that's is interesting here that since you bring this up is, you know, you brought up going to the higher complexity to to look at, you know, more advanced packages I think some of the vendors are, are already trying to, to move things in that direction and it's because one of the big issues in some of those advanced packages are things like those via stacks and their reliability. So now there's a mechanical element too, right? 'cause of that thermal, you know, thermal expansion during the devices operation that puts a lot of stress on certain parts of the package. And then of course if that fails, you now have a package that no one wants to use.

Ethan Pierce: Yeah, and I, I think that one of the things that happened at PCB East was one of the, one of the vendors that does the miniaturization, they were talking about like, hey, you know, reach out to us like whatever you're working on, whatever you're trying to do, reach out to us and we can kind of help you. And I think in line with being able to do the thermal design is understanding as an engineer, how do I get resources to design and think through, whether it's thermal design or it's doing things where you're, you're working with substrates, working closely with not just the classic work with your fabricator, but understanding where the resources, where the resources to help you level up how to think through the design problem.

Zach Peterson: So I have to ask you, what was the response from folks who watched your talk? I bring that up because you know, I think a lot of people come to PCB West because there, there's a few things, right? I mean they get to, to see folks who they're fans of, right? So you know, maybe they get to see Rick or maybe they get to see Dan Beaker or something and you know, they're gonna get that SI or EMI kind of, you know, experience firsthand or they're coming because they're gonna learn, you know, about like DFM, you know, we get a lot of fabrication folks who come in and you know, they give some really great presentations on DFM and and DFA too. Like I said earlier, you know, thermal is not always on the menu, so, so I'm wondering what was the response from the, from the crowd when you gave your talk?

Ethan Pierce: People were very engaged. They were engaged with it because they had never seen a thermal simulation. You know, Thomas did a excellent job talking through different structures and boards talking about things like copper coin and also like via structures that you're gonna have in an IMS board and thinking through like heat transfer that happens when you have an IMS board and you're doing your via drills. The response, the response that we had was that people, it, it was interesting to them because all of a sudden their design decisions that they were making, they realized had an impact and then they could also see from a thermal simulation like, oh when I, when I use FR four over when I'm using the IMS material or an aluminum board, we can see a real simulation of where are we actually getting stuck? Like, hey, we've got heat that's stuck under this component and it's not able to move anywhere. It touched on this before, which was, hey, I showed my rev one design where I threw a bunch of vias in there and then I showed my rev two design where I said, okay, I have all the necessary copper to move the appropriate currents, but I'm not throwing as many vias in there. That was all a sudden something that was helping the designers say, oh, okay. That's not something that I intuitively would've thought. I would've thought, hey, well like if I just put these in here, like I'm gonna be able to get more convection through here. So people were engaged and I I I think that for west it'll be an interesting talk. There's some amendments that I, that I'd like to do to it or maybe in the future be able to actually cover that advanced copper and via structures. Because I think that, I think that there's some real value in being able to map like, hey, well here's what these people are recommending in terms of whether that's like via structures and doing something like square grids versus diamond grids in terms of transferring heat and then being able to say, oh, well what does that translate to in a simulation? Because I think as soon as you have some empirical or, or like simulation data where you can say, I did this and here's the result. I think that resonates with people more than if they're a, there's a concept that's explained to them and then they kind of have to just either trust it or there's math associated with it. Especially in the, in the layout space where it's traditionally been a a technician or associates' role. I mean we do have more with, with all of the engineers that are retiring. We've got more hardware engineers that are starting to take on the the PCB layout work. But again, it's, it's, it's being able to, like I mentioned in the beginning, understand your design decisions have an impact and getting an intuition built about when I do this, I'm gonna get that. And I think PCB East and West are a great way to communicate that from basically whenever we're designing a boards we're controlling EMF fields. But I, I think that this also, that's why I we were so excited to give this talk was because it's in the same vein of okay, well there's something that is, you're also going to have an impact when you design and thinking about a system. Thermally heat's going to transfer the reward maybe in a way that you don't have the intuition for. And this is where when we show you when you make these design decisions, here's how the heat's gonna flow through the board.

Zach Peterson: Now you alluded to something important here in that, in that answer, and I think it's something important because I think a lot of designers don't realize this, but there are different things you can do in the board that actually help you with heat transfer. Like I said earlier, I think most people just when they have a thermal problem, they just throw a fan at it or throw a heat sink at it and then you know that fan has enough airflow, the heat problem goes away. But there are actually things you could do in the board to, for example, aid heat transfer to the enclosure. 'cause your enclosure could be a big heat sink too. So you brought up copper coin and then I think there's also heavy copper and then you've brought up some, some stuff with vias. So maybe if you could just explain some of those options.

Ethan Pierce: Sure. So one of the things is we can start backwards. It's like copper coin is actually embedding into your, your stackup a slug of copper and there's different geometries that you can use. There's embedded coins that are gonna get embedded into the board. There's also like press FITT coins that have these like not, they're tapered so that when you, when they actually get physically inserted into the board, they get pressed in. And then also they can be attached into the board as well from from the top. These are, I mean they're, they're very expensive but if you have like sometimes people do them with like bus bars, so you've got high current, but also you need to move a substantial amount of, of heat in addition. So that's, that's copper coin and that's something where you've really gotta communicate with your fabricator for it. In terms of the, the via structures you can, if you drill all the way through your board, the planes where you've got copper attached to them, that's really where you're going to have the heat transfer. So there is a possibility that when you have a high current part is if you can flood out a plane, not just for making conductivity better and reducing the inductances, but also in order to, to conduct heat away from the component as you move down in the layers to like layer 2, 3, 4, what wherever it is, if you've got those pores there, you can dissipate the heat out of the, out of that component and away additionally with your design if you have solder. So the solder mask is going to have some type of insulating property heat wise. And so what you'll see a lot of the times is designers will expose, they'll do a solder mask cutout on the board where there's exposed copper and then they may or may not attach with a thermal pad and then some type of heat sink on there. But exposing that copper can make a huge impact in terms of getting heat away from the system. The thing that you want to consider is you want to be able to move heat away from the components as fast you can and keep them within the operating temperatures. So whether that's a copper coin, whether that's via structures and planes that you're pouring that are flooding and pulling away, those are just some options that you can do. And also exposing that solder mask, those are just some options that you can leverage in order to get heat away from your components.

Zach Peterson: Yeah, those are always really good points. And I, like I said, I, I think a lot of people don't know what all those options are and we just kind of assume that they're gonna, you know, pick it up somewhere through osmosis. I think there's also some maybe non-traditional or less well known active or passive cooling mechanisms, for example, like heat pipes,

Ethan Pierce: Anything where you're adding more surface area and and my experience with heat pipes isn't as substantial as I'd, I'd like it to be. But to be able to basically like spread material, I mean you don't have to have an active cooling system to leverage a heat pipe. You just need to have a heat spreader and like I mentioned, so you've got your component and you're gonna have some type of, of thermally conductive pad material and then above that you're going to have some type of thermally conductive material. Hopefully that's gonna be something like copper. And you've got this huge, you know, heat sink if you've ever opened or seen something like a game console. 'cause typically they're more cost effective in putting down the heat spreaders and heat pipes is, you'll have, you'll have a heat spreader and you've got a heat pipe which has, I think it's like, it's a, it's a vapor gas or it's like a, there's like a material, there's some type of substance that's inside the heat pipe that helps promote transferring the heat throughout the heat pipe. And then on the other side of the heat pipe, you can have whatever you want in terms of like fins or you, if you want to have the blower, sure, but you can also just add a slug and change the geometry because we have different, a ton of different ways, whether it's off the shelf or off the shelf or low volume aluminum cncs. Like you can actually move, move that heat away from that system very quickly just using a heat pipe, heat spreader and, and something with a lot of surface area and fins. There's one thing that we, we haven't chatted about, which is sort of, there's a handful of new companies that are basically leveraging semi semiconductor technology in order to build fans that sort of have this like membrane that moves at these insanely high speeds and basically is like a mini jet. But there the, the profile is super low, obviously, like you mentioned before, there's like the, there's the power control circuitry, but it's interesting to see businesses leverage semiconductor technology to make super high density active cooling thermal systems that are going to be start leveraged in things like notebooks and maybe even things like phones in, in some period of time, especially tablets too.

Zach Peterson: That's really interesting. I was not aware of that kind of, of cooling system like a, a little mini jet inside of inside your device, but that sounds really interesting. So yeah, maybe once we get off or once we get done with this episode, you'll have to make an introduction or recommend a a company so that we can learn more about

Ethan Pierce:  That. Oh yeah, yeah, yeah. There's there's a couple.

Zach Peterson: Yeah. Yeah, that's, yeah, that's really interesting. Going back just a moment to metal backed or metal substrate boards, I think the most common type PCB that I see brought up for operating in high heat situations, whether it's in a, you know, high temperature environment or you know, the board is gonna have components that reach high temperature is definitely insulated metal substrate. I think that one has its own manufacturing challenges, doesn't it? Because the issue is that if you're doing, let's say, you know, routing on both sides of the board, you have to get those vias through that substrate. And my understanding from, from having done this one time was that the, the yield can be really bad on those boards, is that correct?

Ethan Pierce: My my understanding, yeah, is that from, at least when I did my boards too, is that the, you have to really be strategic about where you're placing the vias and understanding why you're, why you're drilling through it. There's a, there's a couple different ways that you can leverage A-I-I-M-S stack up and that's, you know, through a single layer sided board where you've got, you've got the pre, or I think it's pre or post bonded copper in a pre preg on the top. And then you've got the material, there's also multi-layered, single-sided where you've got copper in prereg and then you have this insulating material that's on on top of it. And then, like you mentioned, there are multi-layered double-sided IMS boards, but it just, it adds a lot of complexity, especially when you're doing, what's the word that I'm looking for? The drill registration and also being able to, like, you have to do these multiple cycles of drilling, what is it? You've got to, you've got to drill and plate multiple times through, through metal. So the yield can not be so great, but typically these are not high speed boards that are, are being leveraged for this. It's a lot of the times it's something that's simple, it's low speed, it's some LED drivers, some LED board, some other high powered power supply system. So in terms of getting, like I've yet to see someone where it's like, hey, you know, I need to run controlled impedances on, I'm sure people do it. I, you know, I heard today somebody did a 70 layer board that was the size of a table and I've never heard of anything past 40. So things are moving really fast and, and there's stuff that people build that, you know, I've never heard of before.

Ethan Pierce: Yeah. I'm waiting for someone to produce a design with a prime number of, of layers. So we'll see if that ever happens.

Zach Peterson: Yeah, yeah, exactly.

Zach Peterson: Well this has been really cool. Thank you so much for talking with us today and you know, I'm sure I'm gonna catch up with you at definitely at PCB West probably beforehand and yeah, hopefully we can get some more insights on some of those companies and, and techniques that you mentioned for thermal control in your PCB.

Ethan Pierce: Yeah, absolutely. Zach, thank you again for having me on the podcast. It's always a blast and I look forward to seeing what, what people come up with next.

Zach Peterson: Awesome. Thank you so much to everyone that's been watching and listening. We've been talking with Ethan Pierce, founder of Dote Labs. If you're watching on YouTube, make sure to hit the subscribe button and hit the like button. If you subscribe, you'll be able to keep up with all of our podcast episodes and tutorials as they come out. And last but not least, don't stop learning, stay on track and we'll see you next time. Thanks everybody.