Interview — John Maguire, Nordson MARCH
With over 25 years of continuous innovation, Nordson MARCH designs and manufactures a complete line of award-winning and patented plasma processing systems. An expert staff of scientists and engineers is available to assist in the development of plasma processes that improve product reliability and increase production yields.
Plasma is becoming more and more important in the wire-bonding process. Can you tell our viewers some of the reasons it’s becoming so important to clean probably, and why plasma’s fairly essential?
What you see in the market today are a couple of trends. They’re not new. It’s miniaturization, it’s higher I/O density, it’s the need for greater yield, for better reliability in the long term. What plasma can do for you is ensure that you get better wire bond statistics, that you get a reduction of your nonsticks, and if you then look at long-term reliability, we’re removing all kinds of contaminants from the surface, so you get no corrosion in long-term. Those are our two biggest contributions to the wire-bond process: better statistics, better long-term reliability.
By eliminating the corrosion.
As you said earlier, the number of I/Os that we’re getting nowadays is increasing all the time, the density’s increasing, and it’s becoming even more important to use something like plasma to get the level of cleanliness.
Yes. Absolutely yes. People are shifting the goal posts. If you think about a few years ago, an automobile was designed to run for a thousand hours. Today most people are designing for four thousand hours. The demands for reliability are much higher. At the same time, there are much, much more electronics and many, many more connections, many more I/Os, and you only have to lose one connection, one wire bond somewhere, and there you are, stuck in the rain, the wind, in the middle of somewhere with a car that doesn’t work anymore. That’s what’s driving it. It’s the shifting goal posts, which means that people need to do the same as they did before, only better. And plasma enables you to do it better.
Let’s talk a little bit about the systems themselves and how they work. What is the process like?
We run all our processes at low pressure, so the first thing we do is we take our parts, we put them in a chamber, and then we’ll drop the pressure down to normally 100, 250 millitorr, which is quite a deep vacuum. Then we’ll introduce process gases. Which gases depends on the application. We start to activate the gas using a radio frequency. What this does is it splits the gas into component parts. The chemistries may be a bit complicated, but essentially into ions and electrons, and then we can use accelerated ions to clean the surface. That’s the basis. That’ll clean the surface. When the process is finished, we come back to atmospheric pressure, and we take the parts out.
The radio frequency you use is fairly low.
We use 13.56 MHz. The nice thing about that is that actually we use two processes. We use the free radical process, which is a kind of…call it a decomposition of a gas, and we use the ionization process. One of these is a more aggressive process, you could say, and the other is actually a chemical etching process. The nice thing about using the megahertz range is that we can change the balance between those two processes. We have quite a large number of applications that people do, and depending on the application we’ll change that balance. A more physical plasma, more use of ions; a more chemical plasma, more use of the free radicals.
What you’re trying to achieve, though, the finish before the bonding is a roughness, basically.
The key thing for wire bonding is cleaning, so we’re striving for a clean surface to bond to. That’s going to give us improved bonding statistics. We’re striving to clean, particularly, things like halogens, which cause corrosion in the long term. What we can also do with plasma is we can change the surface. For some applications, this is important. But you have to think, it’s topography in the nanometer range we’re looking for. That’s very important, for instance, for coating, for adhesive bonding. That brings you a big improvement in your adhesion strength.
Roughly, what’s the cycle time when we’re doing this process?
It depends on the application. Plasma before wire bonding in a batch machine like this, you’re talking about a few minutes. Five minutes, ten minutes, depending on the application. In a fully automatic machine, you’re talking 60 seconds, 90 seconds, that kind of time frame.
Finally, John, I see from your publicity poster, which you’ve got behind you, that you’ve got a “Get It Right First Time” thing with Henry VIII.
He did it six times, but the first time he was talking to the wrong girl, right?
He took a more radical approach.
That’s right. You know, the machine, really, is a relatively simple instrument, but plasma, for most people, even long-term users, is rather exotic. It’s very, very important if you want to be successful, particularly at world level, that you bring more to the party than just a machine. March has a lot of experience, we have a lot of highly educated and experienced people. We help our customers, we educate them. We tell them what plasma is, what you can do with it, what you can’t do with it, and we help them to develop their applications. We really are a solution provider, because if you buy a machine, but you don’t understand plasma, you won’t get the best out of it.
March has certainly been a major player in this market for a long time. Thank you very much for giving us a walk-through on it, John. We look forward to having more animated discussions in the future.