Heat-sink devices and technology have many aspects, but I am hooked on basic models of varying sizes and fabrication technologies.
I’ve always been fascinated by heat sinks, ever since I began “messing around” with electronics. This involvement began with a simple, stamped-metal clip-on unit, shown in Figure 1, which solved my problem of a “too hot to touch” transistor in a can with wire leads (so ancient).
From there, I saw the possibilities in the larger extruded or cast sinks that rested on top of an IC, and which clearly said, “I’m a serious heat sink.” When a co-worker was tossing out an Intel Pentium II CPU (roughly 1997 to 2001 vintage) with its black, custom-designed heat sink, I grabbed it — not for the Pentium, for which I had no use, but for that elegant, fitted unit of Figure 2.
The finned heat-sink for a power MOSFET of Figure 3 is a silent but strong work of art as well, in its own way.
My interest in passive cooling devices didn’t stop with heat sinks. I soon discovered the joys of the heat pipes and their associated partner, the cold plate. Heat pipes amazed me with their ability to move heat energy to a colder end using just the phase change of the internal working fluid; no pump, no fan, no motor, no noise, nothing except their implementation of some basic principles of physics. Stick a heat pipe into a cup of boiling water alongside a metal rod of the same diameter, and you’ll be impressed at how quickly the exposed end of the heat pipe gets hot compared to the plain rod.
Of course, there’s more to heat sinks than the metal alone. Using a heat sink opens you up to a world of thermal grease, thermal pads, and even small clips that hold the big sink to an IC. Further, for some power devices with integral extended tabs, you can even get heat sinks that attach using a small screw that goes through a hole in the tab.
I’m not sure why I have always found heat sinks to be so fascinating. Perhaps it’s because they make the invisible “goings-on” in the electronic components somewhat tangible and real, to be seen and felt as the heat these components dissipate. Or maybe it’s because they do one thing, they do it well (if sized and applied properly), they don’t require software or initialization, they need no maintenance, they don’t get unwanted upgrades, and they don’t push back on your circuit or system. Instead, they just silently do their job of getting your IC’s heat away from its die, thus saving its life, so to speak, while all they ask for in return is some unrestricted airflow.
Still, I wonder if there is a deeper reason beyond their simplicity, physical reality, and effectiveness that they appeal to me. My cynical view (unfortunately based on experience) is that a heat sink is a symbol of the mindset and attitude of too many people today.
How so? The heat sink allows the person who selected and designed-in that overheated IC to make his or her heat problem into someone else’s problem by transferring the IC’s heat to that mystical place called “away,” and so evade direct responsibility for the consequences of that heat.
Of course, “away to where?” is the next question, as the heat sink doesn’t provide actual cooling or lower-power operation. It just moves the heat from one neighborhood to another, thus making it someone else’s problem — a very clever move. I think that’s why heat sinks are classified as thermal “management” components.
It’s too bad that heat sinks don’t get the respect they deserve, even though they don’t depend on nanometer process technology or billion-dollar fabs. Even in today’s world of low-power and ultra-low-power ICs, there’s still a huge need for these “ancient” passive devices, which range in size from tiny wings to imposing hunks.
The latter heat sinks sometimes remind me of the stone statues on Easter Island, looking out instead onto an expanse of a PC board rather than the Pacific Ocean. Their mass and configuration — which is what they are all about — speaks louder than the invisible flow of electrons in the circuit, and is a silent testimony to the role they play.
In many cases, these sinks alone can’t manage or solve the entire heat problem. It may also take more active solutions, such as fans, liquid cooling, submerged cooling, and many other advanced systems, to provide a complete answer. But in many cases, the heat-flow path starts with a heat sink.
Of course, even passive heat-sink technology is not static. We are seeing technical advances and the use of quasi-heat sink components in commercial products, using thermal principles that were known for centuries and formally analyzed and understood by the late 1800s.
For example, researchers at the University of California at San Diego have developed a new cooling material that could significantly improve the energy efficiency of passive evaporative cooling. The UCSD technology features a specially engineered fiber membrane that passively removes heat through evaporation of moisture, as shown in Figure 4.
The low-cost fiber membrane has a network of tiny, interconnected pores that draw cooling liquid across its surface using capillary action. As the liquid evaporates, it efficiently removes heat from the electronics underneath, with no extra energy required. The membrane sits on top of microchannels above the electronics, pulling in liquid that flows through the channels and efficiently dissipating heat. Their work is detailed in the paper “High-flux and stable thin-film evaporation from fiber membranes with interconnected pores” published in Joule.
Another approach is vapor-chamber cooling, a technique used to remove heat from a local source via a flat, sealed chamber filled with a small amount of liquid (de-ionized water) that evaporates when exposed to heat, shown in Figure 5.
Vapor chamber cooling evenly distributes the heat across the entire chamber, allowing for more efficient cooling. While it has been on graphics and CPU cards as well as chassis, its use is spreading to truly mass-market consumer devices such as gaming consoles and smartphones. Apple is using it to move heat away from the powerful A19 processor used in their models 17 and 17 Pro smartphones and even touting it in some of their ads (you can see the commercial video here.). I’ll bet that users don’t know that there is water — albeit a tiny amount — in their smartphones.
All these “heat-sink” cooling advances are welcome, of course. But I’ll think I’ll restrict my attentions to basic, carefully shaped, stamped, machined, or extruded hunks of metal, as it doesn’t get simpler or more to-the-point than those.
References
What is Vapor Chamber Cooling?, Radian Thermal Products
Heat Pipes vs. Vapor Chambers, Dai Nippon Printing Co (DNP)
Here’s what we know about the iPhone’s vapor chamber cooling system, Computerworld
Water Vapor Could Cool Your Next iPhone, IEEE Spectrum
Here’s how the iPhone 17 Pro vapor chamber actually works, 9to5Mac
Apple unveils iPhone 17 Pro and iPhone 17 Pro Max, the most powerful and advanced Pro models ever, Apple
High-flux and stable thin-film evaporation from fiber membranes with interconnected pores, Joule
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