Cooling your electronics is pretty important. I know this because part of my laptop’s motherboard melted once. I bought a new top of the line computer back in 2010 to try out a new graphics intensive video game. It came with an amazing graphics card, but an undersized thermal management system. I should have known there was a problem when the keyboard got too hot to touch when I started playing games. Soon afterward, my computer was on the fritz. I took it into a repair shop, where they told me that some of the insides had melted. Luckily it was still under warranty, so the manufacturer had to foot the bill. Maybe if it had been designed with a more powerful cooling system the whole debacle could have been avoided. If you don’t want to design something that melts, it might help you to review a few of the different cooling techniques that can keep your circuits chilled. These include such things as fans, ionic wind generators, and piezoelectric bellows. Each thermal management process comes with its own pros and cons that can help you decide which is best for your application.
Not only do you want to keep your boards from catching fire, you want to do it in an optimal way. If you’re working in embedded systems or other applications with a low power budget, then you’ll need the most efficient kind of cooling system. You also don’t want your cooling process to take up too much space or need lots of maintenance. That’s why I’ll discuss the power usage, size, and maintenance of each system as I go through them.
I would not recommend this cooling system.
After my laptop melted, they replaced the graphics card with a less powerful one to beat the heat. However, my computer still overheats. So now I’ve taken to putting a desk fan next to it when it’s on. Let’s take a look at the fans that go inside computers.
Power Usage - Fans are the most common type of active cooling scheme because they’re simple and fairly inexpensive at the outset. However, fans use a relatively large amount of electricity. If you’re designing a low power PCB I wouldn’t recommend cooling it with your average fan. That being said, there are some exceptions to the rule, such as Sandia Laboratories’ Sandia Cooler. This fan is very efficient and uses up to 7% less energy than a normal fan.
Size - If you’re looking for something small, look elsewhere. Fans have a large form factor, and also require some kind of mounting frame and motor. These guys are better for macro than micro.
Maintenance - While they may not need as much maintenance as other schemes, fans do need to be cleaned fairly often. Dust settles on them, reducing their performance and increasing the likelihood of a meltdown. Again, though, the Sandia Cooler has mitigated this issue. It spins much faster than a normal fan, flinging off any dust particle that attempts to land.
Ionic Wind Generators
When I hear “ionic wind” I think of some terrifying gust flying through space. The reality is slightly less interesting. Ionic wind generators (also known as corona discharge or ionic jets) consist of a positively charged plate and negatively charged plate. The resulting electric field between the plates creates a gentle wind. Since the breeze is generated with no moving parts, this solution is silent.
Power Usage - On the power scale, ionic wind rates above traditional fans. They are definitely more efficient, though exactly how much more efficient is yet to be determined. This makes them appropriate for low power applications.
Size - Ionic wind generators simply consist of two charged plates, making them more easy to fit inside an enclosure than a fan. You can put the plates close together, you can put them far apart, you can do whatever you want. The power supply for these might be a bit hard to fit, as you’ll need to convert your incoming supply to a much higher voltage.
Maintenance - If ionic jets were putting some wind in your sails, prepare to be disappointed. Reliability is a major problem for these. The positive plate oxidizes quickly due to its charge, reducing the efficiency of the generator, and leaving this technology dead in the water.
You can go for normal bellows if you’re feeling old school.
Instead of using an oscillating fan to cool my laptop, I could have used some bellows. The only problem with bellows is that they require someone to pump them, and I don’t have any blacksmith’s apprentices on hand. Also, you can’t even fit a bellows inside a PCB. So how do these work? Piezoelectric bellows consist of two plates made from piezoelectric material that vibrate when you run a charge through them. This vibration forces air in and out, just like a fan. GE’s model measures in at 4 mm, making it a very slim solution
Power Usage - Folks, we have a winner. This strange system is estimated to consume 1/10th the power of conventional fans. If you need an energy efficient solution, this is the one.
Size - Piezoelectric bellows can take up as little space as an ionic wind generator. This making it perfect for small form factors.
Maintenance - To be honest, I’m not quite sure what kind of maintenance is needed for this cooling process. However, no articles I’ve read mention any maintenance, so I wouldn’t worry too much about it.
If you’re a gamer like me I’m sure you’re familiar with liquid cooling. For those who are a little more mature than I, liquid cooling systems use some kind of liquid (water, refrigerant, non-conductive oil) instead of air to move heat around. Air is effectively an insulator and is thus a poor choice for conducting heat. Liquid cooling systems can remove heat from electronics 2-10 times more quickly than a conventional setup.
Power Usage - On a large scale, liquid cooling can be much more efficient. When I say large scale, I’m talking server farm large. For smaller applications, any money you save on operating costs will probably be spent in up-front costs.
Size - These things are big, and I mean big. Typically people like to show off their liquid cooling systems, so they take up as much space as possible. Even if you’re a little more modest, this arrangement will eat up lots of space. If you’re running something like a data center you might have space, but for mobile applications, this is a deal breaker.
Maintenance - Liquid cooling has a lot of moving parts that may eventually break down. There’s also the huge risk of leaks, which can destroy your electronics. I wouldn’t really recommend this system to anyone who can’t handle their circuit kicking the bucket.
So, now that we’ve explored 4 active cooling technologies, which one should you use? If you’re looking for big cooling in a small package, go for the piezoelectric bellows. They have an extremely sleek form factor that will save you space. If there is no limit to the size of your system, liquid cooling will probably be a more optimal solution for you. On the maintenance end, I would call it a tie between the bellows and traditional fans, simply because it’s unclear what kind of upkeep the bellows need.
Now that you’ve got several cooling systems to choose from, you need to design a hot PCB. The perfect solution for that is CircuitStudio. It has more features than you’ll know what to do with and will make layout a breeze.
Have more questions about cooling? Call an expert at Altium.
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