Adhesion Matters - From Heat to Miniaturization: How Adhesives Are Reinventing PCB Manufacturing

Episode Date: August 10, 2025

Welcome back to Adhesion Matters. Adhesives have quietly evolved from simple bonders into indispensable, high-performance materials in PCB manufacturing—critical for thermal management, electrical performance, and environmental resilience.  In this episode, we explore how adhesives empower modern electronics: enabling miniaturization, supporting flexible and high-density circuits (think HDI and flex PCBs), and meeting rising demands in consumer tech and electric vehicles.You’ll discover how specialized adhesive families—epoxies, acrylics, silicones, polyamides, polyurethanes—each offer unique strengths, from rigidity and heat-resistance to flexibility, reworkability, and flame protection. Hear how engineers tailor selections based on criteria like thermal conductivity, environmental durability, and the ability to withstand mechanical or thermal stress over time.Learn about real-world applications across the PCB manufacturing spectrum: surface mount adhesive placement, underfills, die attaches, conformal coatings, potting compounds, encapsulants, and even thermal interface materials that control heat in EV power systems.Finally, we look ahead at the future of adhesive innovation: extreme miniaturization, advanced thermal management for EVs, and a push for eco-friendlier, halogen-free, low-toxicity formulations.

What holds our advanced electronics together? You know, when you think about your smartphone or maybe the complex systems in an electric car, you probably picture intricate wiring, precise soldering. But here's the surprising, often unseen answer. It's not just solder. It's a whole world of highly sophisticated adhesives. These are the true unsung heroes working quietly behind the scenes. Today, we're taking a deep dive into that world.

Specifically, we're focusing on advanced adhesive. solutions in printed circuit board manufacturing. That's right. And our mission today really is to uncover how these adhesives have fundamentally transformed. They've gone way beyond just being simple bonding agents. They've become truly indispensable high performance materials. You should think of them as critical enablers for, well, for the miniaturization, the increased functionality, and the enhanced reliability that modern electronics demand. We're talking everything from the tiniest wearables right up to the really robust systems and electric vehicles. Okay. And to guide us through this pretty

fascinating topic. We've pulled from some comprehensive sources. We've got a detailed analysis of leading manufacturers, Dow, DuPont, Henkel, and Huntsman. And we also have some additional material from Bodo Muller Chimmy. They're a key distributor for many of these specialized adhesives. Okay, let's unpack this. So you're saying it's more than just sticking things together. What exactly are these adhesives enabling in PCBs? What's their critical function beyond just holding things in place. Well, their roles are incredibly multifaceted. They act as crucial enablers for the entire system's performance and, you know, it's longevity. First off, there's thermal management. With components getting more powerful, they generate more heat. Right.

A big issue. Exactly. So these adhesives are essential for dissipating that heat effectively. It's absolutely vital to prevent device failure and ensure, well, a long lifespan. Then you have their electrical properties. Adheses can be formulated to provide precise insulation for sensitive area. Okay, so stopping short circuits. Precisely. Or conversely, they can even offer precise electrical conductivity where needed. This gives you a flexible, often more space-efficient alternative to traditional soldered joints in certain applications. Interesting. So they can insulate or conduct? Depending on the formulation, yes. And finally, they provide robust environmental protection. These materials shield delicate components from moisture, corrosive elements, extreme temperature

changes, mechanical shock, vibration, you name it. So without this protection, our devices just wouldn't survive daily life. Honestly, no. They simply wouldn't hold up to the everyday abuses they encounter. It's really easy to overlook these unseen components. So when we talk about breakthroughs, like in device miniaturization or, say, extreme temperature tolerance, are these adhesives truly the primary enabler or just one piece of the puzzle? Oh, they are absolutely a primary enabler, particularly for how far we've pushed the boundaries. This shift is directly driven by that relentless push towards miniaturization in consumer electronics, the need for high-density

interconnects, you know, HDI boards, and the increasing use of flexible and rigid flex circuits. HDI boards. Yeah, high-density interconnect. They pack more components into smaller spaces, using features like blind vias and microbius. Think of them as tiny, buried connections that allow for incredible density. Adhesives are critical here. They ensure the integrity of these complex, tightly packed designs where even a microscopic gap could cause a fault. Now, this is where it gets really interesting. We're not talking about some one-size-fits-all glue here, are we? Not at all. There's a whole palette of chemical families, each with unique strengths. Let's dive into some of the main types. Absolutely. Each chemical family offers distinct advantages for specific

use cases. First up, epoxy adhesives. Think of them as the tough guys of the adhesive world. They're key insight, unmatched rigidity and resistance. If you need a bond that absolutely won't flex and can stand up to incredible heat or harsh chemicals, epoxy is your go-to. They're literally the backbone of many devices, ensuring structural integrity where flexibility would actually be a weakness. Got it. Tough and rigid. What's next? Next, acrylic adhesives. These are more the versatile performers. They offer a great balance of flexibility and strength. They're less rigid than epoxy, which makes them superior for things like flexibly. circuits that need dynamic bending.

Imagine a foldable phone's hinge mechanism. Oh, okay. And they're also often fast curing when exposed to UV light, which really speeds up manufacturing. UV curing, right, makes sense for speed. Then we have silicone adhesives. Yeah. These are characterized by extreme flexibility and high heat resistance.

They're ideal for delicate components and for sealing things up. They offer exceptional stability across a remarkably broad temperature range, typically from, say, minus 45 degrees Celsius, all the way up to 275C in some specialized cases. Wow, that's a huge range. It is. Silicones provide superior protection against shock and vibration. They're robust under mechanical stress from thermal cycling.

And crucially, many are reworkable. Reworkable, meaning you can remove them. Exactly. Which significantly facilitates repairs and upgrades. A big deal these days. Okay, silicones for flexibility and heat range. What else? Polymide adhesives.

These are valued for their very very. very high thermal stability. They can withstand temperatures up to 300 degrees Celsius. Even higher. Yep. So they're often found in the highest reliability flexible circuit constructions where extreme heat is just a constant challenge. In aerospace, maybe some demanding automotive uses. Okay. And the last main type. And finally, polyurethane adhesives. These are incredibly adaptable. They can be formulated for almost anything high flexibility, crack resistance, flame retardancy, even thermal conductivity. This makes them excellent for encapsulation and insulation, where you need a tough, protective shell that can maybe also manage heat or prevent fire spread. So that's the core palette of chemical families.

But are there other more specialized adhesive types? Maybe ones used for very niche applications or, I don't know, even something common like super glue. Where does that fit in or doesn't it fit? That's a great question. Because yes, the specialized world is vast. beyond those main families you have things like UV adheses

which we touched on for their incredibly fast curing perfect for high speed assembly lines then there are pressure sensitive adhesives think high tech tapes basically

but they typically can't handle the high processing heat involved in making a PCB they'd melt exactly but their heat resistant cousins often called assembly resistant adhesives

can handle that heat and yes even cyanoacrolates what most people know is super glue they exist for very quick, maybe minor fixes during prototyping or something. But they're generally unsuitable for actual PCB applications involving high heat or vibration. So definitely don't try to super glue your graphics card back together. Uh-huh. Okay. Noted.

So how do engineers choose? What are the critical things they look for? Well, the selection process is highly nuanced. It really hinges on several critical performance criteria. This includes mechanical strength, obviously. You need strong, durable bonds that won't fail. Sure. than thermal stability. The adhesive can't degrade under high temperatures, both during manufacturing and, you know, when the device is actually running.

And reworkability, which we mentioned with silicones, the ability to remove a cured adhesive for repairs or component replacement. That's increasingly valued, both for serviceability and sustainability. Ah, so no more game over if one tiny component fails. That seems like a huge leap, both for the consumer's wallet and maybe the planet's recycling. efforts, right? Absolutely. It makes a massive difference. Another key aspect is CTE management.

CTE. Coefficient of thermal expansion. It's about how adhesives minimize stress caused by different materials expanding and contracting at different rates when the temperature changes. Think of the adhesive acting as a kind of stress reliever, preventing components from basically tearing themselves apart as temperatures fluctuate. That's fascinating, like a tiny shock absorber between materials. What's one common pitfall, though, or maybe a misconception engineer's face when

choosing. What's the biggest gotcha these different types are designed to overcome? A big gotcha is probably underestimating the long-term environmental stress. An adhesive might look fantastic in initial lab tests, right? Strong bond looks good. But if it can't withstand

repeated thermal cycles, heating up, cooling down day after day or humidity or vibration over years of use, then it's ultimately a failure. The distinct types we talked about are designed to overcome exactly that. To create a bond that is not just strong initially, but predictably strong for the entire expected lifespan of the device under the specific, often harsh conditions it will actually

face. Right. Reliability over the long haul. Okay, now that we know what these adhesives are made of, let's see them in action. Where are they actually used across the PCB manufacturing process day to day? Okay, yeah, they're integral at numerous stages. Let's start with component attachment. In surface mount technology or SMT bonding, adhesives are frequently, used to attach chips, SMDs, surface-mounted devices, to the PCB before the soldering step. Before soldering, why? To hold them in place, especially for double-sided boards going through reflow evans. UV curing adhesives are often preferred here because they cure so quickly, which is crucial for high-volume production lines. Then a truly critical application is flip-chip

underfill. This is absolutely vital for mechanically stabilizing delicate flip chips and also for compensating for material stresses. Underfill. So it flows underneath the chip. Exactly. The underfill literally flows into those minute gaps beneath the chip. It reinforces the tiny solder joints and minimizes stress from thermal mismatches between the chip and the board. And importantly, some underfill formulations are designed to be reworkable. That allows for repair or replacing a faulty chip, which is a massive benefit for complex, expensive components. Okay, that makes sense. What other attachments? You also have dye attach adhesives, used specifically for bonding the semiconductor dye itself.

These often require very low war page, you don't want the chip bending, and sometimes precise electrical conductivity. And for applications where maybe a full underfill isn't needed or is too costly, there's edge bonding and corner bonding. Here, adhesives are just applied to the outer sections of a package, offering a more cost-effective solution for targeted mechanical stability. So different levels of securing components, what about protection?

Right. Beyond attachment, adheses provide crucial protective layers. Things like glob top ceiling compounds and potting materials. These are used to fully encapsulate electronic components. Like burying them in protective goo. Kind of, yeah. It provides robust environmental protection and mechanical stabilization. Then you have conformal coatings. These are applied as thin protective layers to shield entire PCBs from moisture, corrosion, and temperature fluctuations. It really extends their operational life. And for high-power electronics, think inverters. Batteries in EVs, encapsulation resin systems are specifically engineered. They provide extreme mechanical and electrical protection.

They help improve thermal management by dissipating heat. And crucially, they help prevent flame propagation if there's a short circuit. That's paramount for safety, obviously. Absolutely critical in things like cars. Definitely. Adheses are also fundamental to the structural integration of multi-layer PCBs. They're critical for bonding flexible interlayers together. or bonding rigid cap layers in these complex constructions.

And solder masks, those green or sometimes other colored layers you see on PCBs. Those are essentially permanent adhesive inks. They provide long-term protection, ensure high reliability, and precisely define the areas where solder connections are made. I never thought of solder mask as an adhesive, but it makes sense. It functions like one, providing that permanent protective layer. Finally, their functional role in thermal and electrical management is rapidly expanding. We have thermally conductive adhesives essential for efficiently dissipating heat from power electronics.

Of course, thermal interface materials, or Tim's. Tim's right. Like Hankles' well-known Burquistie brand products, for instance. These are essential. They're designed to dramatically improve heat transfer between heat sources like a powerful CPU or battery cells, and their cooling systems, like a heat sink. Think of them as everything from soft, compliant pads that fill microscopic air gaps on uneven surfaces, to advanced liquid gap fillers, and even phase-change materials that liquefy slightly when hot

to ensure maximum contact and dermal conductivity. So filling every tiny gap for better cooling. Exactly. And naturally, electrically conductive adhesives offer a solution for creating electrical contacts or maybe performing repairs without traditional soldering. This is particularly valuable for temperature-sensitive components or substrates where the heat from soldering could cause damage. Okay, wow, they really are everywhere in the process.

Now, let's look at the major players. The company's pushing the boundaries here. You mentioned four big ones. It's not quite head-to-head competition, you said, but more an ecosystem of specialization. That's a great way to put it. It's like an ecosystem. Let's call them the four horsemen of adhesion for our deep dive. I like it.

Let's go. Okay. First up, Dow. They are really the silicone specialists, known for their high-performance silicone solutions under the Dow's old brand. Their key insight, or strength, is superior stability across extraordinary wide temperature ranges. Remember that negative 45 degrees C to 275 degrees C range we mentioned? Yeah, that was impressive. That's Dow's territory. This means robust protection against mechanical

and environmental stress, and they offer flexible, often reworkable options. Dow focuses on diverse curing mechanisms too, like one part and two-part RTVs, room temperature vulcanizing adhesives, and also heat-cured systems. For example, their Dowsell 7dero 91 provide strong flexible bonds, and Dow Sol T.C. 2035 CV is a key product for high-performance thermally conductive applications. Okay, Dow, silicones, and temperature range. Who's next? Then there's DuPont, often seen as the integrated innovators, especially strong in materials for flexible circuits. They offer a really comprehensive portfolio, particularly excelling in adhesive solutions for flexible and high-speed circuits. Their materials enable complex, multi-layer designs,

like their well-known Pyrillux brand products. The Pyrillux. Right. Heard of that. Their expertise spans acrylic-based solutions for dynamic bending, epoxy-based for high peel strengths and chemical resistance, and even flora-polymer solutions, which are crucial for high-speed and high-frequency performance.

Think Pyrlex HP, which you find in demanding military, automotive, and medical applications. So DuPont-integrated solutions, especially for flex and high-speed. Got it. Number three. Next we have Henkel. They are a real. powerhouse and assembly protection. They are recognized globally as a leader in qualified materials

for semiconductor packaging and PCB assembly. Think brands like Locktite, Echabond, Technovelty, multi-core. Hinkle holds a dominant position in things like underfills and encapsulence that are crucial for today's miniaturized high-density packages. Their underfills are engineered to enhance mechanical strength, meet tough shock and bending requirements, and extend product lifespan. And again, they offer valuable options for reworkability. Reworkability keeps coming up. Seems important. It really is. Hinkle also provides comprehensive conformal coatings, SMT adheses

we talked about earlier, and a very wide range of thermal interface materials under their Bergquistie brand. Ah, Berkwistie. That's the Tim brand you mentioned. That's the one. And it's worth noting here that connection to distributors like Boto Miller-Kami. They are a key channel for many of these specialized adhesives, including Henkel's Burkwisting Tims. That's a fascinating point about the distributors playing such a crucial role, it really highlights how these industry giants, the four horsemen we're discussing, interact, maybe not just competing directly. But let's introduce Huntsman first, and then maybe circle back to that ecosystem dynamic. Absolutely. Good point. And finally, Huntsman. Think of them as the high-performance system engineers. They contribute robust epoxy and polyurethane systems under their erudite and erythane brands. These are vital for really demanding applications like power electronics encapsulation.

Their products, like Aeroldite 2014-2, which is known for high chemical and temperature resistance, feature robust thermal conductivity, excellent electrical insulation, and critical flame retardancy. This is absolutely crucial for safety and reliability, especially in things like electric vehicles. Right, EV safety is huge. Exactly. Huntsman also provides highly reliable solder masks, like their ProBimer brand. They actually have over 40 years of experience just in solder mask development alone. 40 years just on solder masks.

Okay. So, Huntsman, high-performance systems, encapsulation, safety, and solder masks. So now that we've met all four, you hinted earlier at this complementary ecosystem. How exactly do these specialized companies collaborate or maybe differentiate themselves to serve the whole PCB industry? Because it sounds like a manufacturer might pick and choose across these players for one board. Exactly right. What's really fascinating here is that these companies don't necessarily compete head-to-head across the board. Instead, they genuinely create a complementary ecosystem. A manufacturer, for instance, might choose DuPont specifically for their flexible circuits, where DuPont's expertise really shines. Okay.

Then they might turn to Huntsman for the high-performance encapsulation needed for their power electronics section, and then maybe rely on Henkel for the critical underfills required for complex chip packages on that same board. It suggests that no single company offers a universally best solution for every single single. single adhesive application. Instead, each provides optimized, specialized solutions for particular segments and challenges within the huge PCB industry. It's really about finding the right tool for the specific job at hand. So specialization is key. Okay. What does this all mean for the future then? How are adhesives continuing to evolve? What are the big demands driving innovation now?

Well, adhesives are actively addressing several major challenges, and they are definitely at the forefront of innovation. There's the continued relentless drive for even greater miniaturization. Smaller and smaller. Enabling higher component density, finer pitches between connections than ever before. And with increased power density comes heat, so thermal management is paramount. Adhesives are becoming even more sophisticated for heat dissipation and crucially preventing catastrophic thermal runaways, especially in batteries. There's also a constant push for enhanced reliability and durability. Adhesives are being formulated to withstand ever more extreme conditions, repeated thermal cycling, severe mechanical shock,

harsh chemical exposure, ensuring products last longer in tougher environments. Makes sense. What about greener solutions? Yes, absolutely. A significant and growing trend driven by both regulation and consumer demand is sustainability and regulatory compliance. We're seeing a strong shift towards halogen-free and low-toxicity formulations. We saw examples from Henkel and Huntsman focusing on this. It reflects an industry-wide emphasis on reducing environmental footprint. print that really goes beyond just ticking compliance boxes. It's becoming a responsible innovation. Good to hear. And finally, the automotive electronics sector, especially electric

vehicles, EVs, is a critical bellwether for adhesive innovation. It's really driving things forward. How so? Well, adhesives and EVs face unique, really demanding environments. You've got high operating temperatures from batteries and power electronics, substantial vibration from the road, diverse materials needing to be bonded reliably, and extremely stringent safety requirements. Think about preventing thermal runaways and battery packs. Adhesives play a role there, too. This drives intense innovation in thermal management, those advanced gap pads, liquid fillers we talked about, and also in developing ultra-fast curing mechanisms to keep up with rapid automotive production demands.

Wow. So EVs are really pushing the envelope. Looking ahead, it sounds like adhesives are becoming even more multifunctional. You could almost imagine materials that sense and respond to their environment or cure instantly. It almost sounds like science fiction becoming engineering reality, doesn't it? It really does. The potential is huge for adhesives to do even more than just bond and protect. So we've taken a deep dive today into the incredible, often unseen role that adhesives play in our electronics. It's amazing, really.

From the smallest wearable device you might have on right now to the complex, critical systems in an electric vehicle, these materials are absolutely fundamental enablers. They enable performance, reliability, and miniaturization. They are truly the invisible strength holding our digital world together. And just to reiterate, adhesives are definitely no longer just glue. They are sophisticated functional materials, particularly tailored for very specific engineering challenges. The distinct specializations of companies like Dow, DuPont, Henkel, and Huntsman,

this whole ecosystem, it creates a robust, and innovative industry, providing optimized solutions for pretty much every segment of PCB manufacturing. So next time you pick up your phone, or maybe you get into an electric vehicle, just take a second to consider how much of our daily technological marvels rely on these invisible, yet utterly indispensable bonds. It makes you wonder what other hidden heroes might be out there, quietly enabling the next big leap in technology, just waiting for us to shine a light on them.