Vishay MEPIC: The Chip Component Built to Burn
イチケン / ICHIKEN
At first glance, the Vishay MEPIC looks like an ordinary chip resistor. In this video, the presenter, Ichiken, explains that it is actually designed to be burned. He bought a few from DigiKey and wanted to answer two questions: what happens when you push current through one, and why would anyone need a part whose job is to destroy itself? His view is that hobbyists will almost never choose this part, but it may be doing important work in emergency situations.
A Sesame-Seed-Sized Part With a Thin Conductor
The MEPIC is very small. It comes in an 0805 package, which measures 2 mm × 1.25 mm, and the presenter compares it to a sesame seed. Up close, a thin conductor runs across the center of its surface. He measured its resistance at about 2.1 ohms. His working guess was that passing current through this fine line would make it glow and then burn.
Burning It Gradually, Then All at Once
He started at 0.3 A, about 0.2 W of power, and nothing visible happened. He then raised the current little by little. At 0.4 A the line began to glow faintly red, and at 0.42 A it was clearly red. At around 0.45 A the glowing line snapped and the part failed. He admitted the result felt a bit underwhelming compared with what he had expected. In close-up footage, the part reddens as current increases and then cuts out with a small click.
Next he applied enough current to break it immediately, switching it on in one step. The part snapped open with a small "pop" almost instantly.
The First Link in an Explosive Train
The presenter then explained the part's purpose. It is the very first component used to ignite gunpowder, by which he means industrial explosives and similar materials. In mining, for example, workers drill long, narrow holes, pack them with explosives, and set them off. These systems usually begin with a small trigger and amplify the energy step by step until it ends in a large explosion. This chain from a small energy source to a large one is called an explosive train. The MEPIC sits at the very start of that chain and sets everything in motion.
He also mentioned fireworks. Large displays often set off fireworks in time with music, and keeping the two properly in sync requires control at the millisecond level. Pointing back to the demonstration, where the MEPIC burned through in an instant, he argues that electronic ignition timing, rather than mechanical timing, is a real advantage here.
Airbags and Seatbelt Pretensioners
The example closest to everyday life is cars. The presenter says parts like this might be used in airbags and seatbelt pretensioners, and he is careful not to claim that MEPIC specifically is used in any particular product.
He described the airbag's structure. Inside the airbag is an inflator, which contains a gas generant and an igniter. The gas is produced by burning the gas generant. That combustion is started by a transfer charge, which he says is also called an enhancer, and the transfer charge is in turn ignited by an igniter called a squib or initiator. The initiator contains its own ignition charge (a primer), which is also an explosive that must be set off. Some initiators do this with a fine bridge wire: current through the wire heats it and ignites the heat-sensitive charge.
The presenter's point is that a MEPIC works on essentially the same principle. Current through a fine line on its surface makes the line burn. That is why a purpose-built burning part could fill this role.
He then walked through the crash sequence. Suppose a car traveling at fairly high speed hits a wall, a utility pole, or the car in front:
- The ECU sends a signal that energizes the bridge wire.
- Heat from the wire ignites the ignition charge.
- The flame spreads to the transfer charge.
- The transfer charge ignites the gas generant, which produces the gas.
Using a cutaway illustration, he showed how a tiny amount of heat at the moment of energization is passed through the ignition charge, transfer charge, and gas generant, growing larger at each stage. Seatbelt pretensioners work the same way: in a collision, gas generated by an explosive inside the device tightens the belt and presses the occupant against the seat.
How It Burns Differently From a Resistor
Finally, the presenter compared the MEPIC with an ordinary resistor pushed to failure. He admits the difference is hard to see on video. The resistor heats up gradually, and it looks as if the resistive coating is slowly burning away. The MEPIC's conductor seems to catch fire and melt almost instantly.
In his view, characteristics like how consistently the part burns and how long it generates heat are important parameters. If a component is not properly designed for these, it cannot serve as the starting point of an ignition chain. Because specialized parts like the MEPIC exist, he concludes, that first trigger can be produced with proper reproducibility.
Takeaway
The presenter says that when he first saw the MEPIC on DigiKey, he wondered what on earth it was for. Learning that such a tiny, self-destructing part may sit at the very start of systems like industrial blasting, synchronized fireworks, and automotive safety devices was the real surprise of the experiment.
This video is brought to you by DigiKey.
At first glance, this component looks like a resistor, but actually, it's a part designed to be burned.
Hello. I bought some interesting electronic components from DigiKey again, so let me introduce them to you. This is from Vishay. It's a component called MEPIC. What exactly are parts designed to be burned used for? You'll hardly ever choose to use this part on your own, but it might actually be used in an emergency. Today, I'll try it out as I explore what exactly it does.
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First, I'd like to try using this MEPIC. It is a very small part. The size is 0805, measuring 2 mm × 1.25 mm. It's about the size of a sesame seed. If you look closely, you can see what looks like a conductor running through the center. When I measured the resistance this way, it turned out to be 2 ohms. It's 2.1 ohms. I guess you pass an electric current through this thin line to make it glow.
Let's actually go ahead and burn it. Here we go. Currently, 0.3 A is flowing. In terms of power consumption, it is currently using 0.2 W. Let's increase the current little by little.
There's nothing happening yet. 0.4 A. I'm passing 0.4 A through it, and it's a little red. Can you see this? It looks something like this. It's actually turning a little red. We'll continue to apply current. 0.42 A. It's gotten pretty red. Is this okay? It broke. It's about 0.45 A. When I passed that current through it, this red thing snapped. It actually seemed kind of underwhelming compared to what I expected.
Here's what it looks like up close. As you gradually increase the current, it turns red like this, then breaks with a click. Next, let's see what happens if we suddenly pass enough current to make it break. It will look like this. Turn on the switch. It snapped with a little pop.
That's how I was burning it, but what exactly is this part used for? Actually, this is the very first component used to ignite gunpowder. When I say gunpowder, I'm referring to industrial explosives and the like. For example, in mining, you dig a long, narrow hole, pack explosives in there, and blow it up. With those explosives, it starts with a small trigger. It is common practice to gradually amplify the energy until it culminates in a massive explosion. This transfer of energy from a small source to a large one is sometimes referred to as an explosive train. This part is what sets things in motion right from the very beginning.
There are also fireworks. At large-scale fireworks displays, they set off fireworks in sync with the music. As you saw in the video of the MEPIC burning earlier, it burned in an instant. In order for the music and fireworks to be properly synchronized, control at the millisecond level is required. Being able to control the timing electronically instead of mechanically is actually pretty nice.
Then there's something closer to all of you: automotive airbags and seatbelt pretensioners. This might be used in those, too.
If we take a closer look at the structure of an airbag, inside the airbag is a component called an inflator, which generates gas. It contains a gas-generating agent and an electric detonator. First, let's talk about how the gas is produced. The inflator contains a gas-generating agent. It generates gas by burning it. To burn the gas-generating agent, there's an ignition charge, also known as an enhancer, inside, and we burn that. The combustion of the ignition charge spreads to the gas-generating agent.
How do you ignite the ignition charge? An igniter is used for this. These are called squibs or initiators. The initiators also contain a primer. This is also an explosive, and it needs to be burned as well. Inside the initiator is a wire called a bridge wire. An electric current is passed through it, and the heat causes the primer to ignite. This means that components like MEPIC, which are designed to burn, can be used in that area. This also works by passing an electric current through the fine lines on the surface to burn them, so it's essentially the same. It was a part that could be used in that kind of application.
Now let's take a look at how the inflator inside the airbag actually works. For example, if a car is traveling at a fairly high speed and hits a wall, a utility pole, or the car in front, you want to inflate the airbag. First, a signal is sent from the ECU to energize the bridge wire. The heat generated by the bridge wire causes the primer to burn. The flames then spread to the ignition charge, which, in turn, causes the gas-generating agent to burn, producing gas.
Here's what it looks like in a transparent view. It all started with something small: heat generated when the power was first turned on. I think you can see how it spreads through the primer, the ignition charge, and the gas-generating agent.
I was just using airbags as an example, but seat belts also use gas in the same way. In the event of a collision, the belt tightens a bit to press a person against the seat. That, too, uses explosives inside to generate gas.
Let's compare how a resistor and a component designed to burn behave when burned. It's actually pretty hard to tell the difference. With the resistor, it gradually gets warm, and it feels like the coating that creates the resistance is burning up. With MEPIC, the wires catch fire instantly, so to speak. It feels like they're melting.
Things like the consistency of the burning and the duration of heat generation are pretty important parameters. If this isn't properly designed as a component, it can't be used as the very first starting point. Since there are specialized parts like this, I think that means we can create that trigger with proper reproducibility.
I found a strange part on DigiKey, MEPIC, and actually tried burning it. When I first saw it, I thought, "What on earth is this?" But I realized that the part was used in a rather important section. That was a surprise. I plan to keep buying interesting components from DigiKey in the future.
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