Inspection and Design for Testability

Estimated reading time: 13 minutes

Müller: Yes, through-hole technology. When it comes to high energies, high voltage PCBs, especially for solar energy or electronic cars, for instance.

Matties: Right. The automotive industry for sure.

Müller: There are still big components, huge solder joints, and it's not always getting smaller, so sometimes you need to rely on the bigger issues.

Matties: As we talk about automotive, you mentioned you had an inspection. In the automotive industry, 50% of the value or more is going to be electronics and vehicles are turning into computers with wheels.

Müller: Yes, even more.

Matties: I would think that this sort of testing is becoming more and more critical.

Müller: I think the automotive industry is one of the most important industries in electronics manufacturing because the number of products and the amount of throughput they have is so amazing and huge that they need reliable inspection systems for their production lines. Even in the middle-class cars, the electronics are increasing, and I don’t think that will change in the near future.

Matties: The cost of failure is so expensive and catastrophic. It could lead to the recall of millions of cars. The idea is to avoid this with inspection upfront, right?

Müller: Yes, that is the idea. Goepel not only offers solutions for the test of the PCBs themselves or for the electronics in the car, but we also have a division that just focuses on the automotive industry. Modern cars have hundreds of ECUs in a complex network. You have to test not only whether the ECUs in the car are working, but also if they’re working correctly in the environment. We offer software and hardware solutions to create the environment of a car. This is also a huge market.

Matties: When you're looking at the automotive industry and testing, it really starts with the circuit board design, doesn't it? Do you ever get involved with the circuit designers as they’re designing board?

Müller: Not especially in the automotive industry, but more in the EMS industry. It's always an issue between developers and the production people because the production people want the best possibilities to test their PCBs and the designer wants to make it small. And that's a problem.

Matties: It’s not always aligned.

Müller: Right. When it gets smaller, it's more difficult to test electronics. We help customers in the design process by providing information that can help them design their electronics smarter for the later inspection and test processes.

Matties: Test-friendly designs, basically.

Müller: Design for testability, we call it. There are some things you must think of when you design electronics and PCBs. When you have done this, you can make your inspection and test process easier afterwards.

Matties: A designer with this sort of knowledge becomes far more valuable to the automotive manufacturers or the developers of automotive electronics, or any electronics for that matter, because we should be always thinking of design for testability, right?

Müller: Yes.

Matties: Is testing a value-added process?

Müller:  In the first place, not. But recall actions are more expensive, which means, no way without testing.

Matties: For the insurance policy.

Müller: Yes, it’s insurance policy, and it's also important for the traceability. Imagine if there is a problem with the car or even with an entire range of cars. Someone has to find out why and where, so when it comes to the electronics manufacturer, they can say, "Okay, give me the PCB I can find out if there has been anything in the process or not."

Matties: You mentioned solder joints, and I also see you are introducing a new SPI system here. Can you tell us about that?

Müller: Most of the problems in the electronics manufacturing process appear on the soldering, in the paste printing process. It's statistically clear and you have to have 3D SPI because you have to measure the volumes of the printed solder paste. I think every electronics production needs to have an SPI system.

Matties: There's a lot of systems on the market place, so what's new in your system here?

Müller: What’s new is that we have more detailed optics to inspect even the lowest heights for soldering pastes and for PCB substrates. You can have a reliable SPI inspection up to 30 microns, which is getting more and more important because it's not always the big solder paste, it's the smaller ones that are getting important today.

Matties: Right. And when a company uses a system like this, what sort of gains do you think they receive in yield? Is there some empirical data where you've done analysis that says SPI will add a given percentage to your yield, for example?

Müller: What we can say is that a good inspection system lowers the fault calls, and this is an important thing. If the inspection system finds a fault and someone has to go there to verify this fault, and if the system is not working correctly and the PCB is done great, then it's a fault call.

Matties: A lot of wasted of time.

Müller: Yes. They have to go there to look. It's a waste of time. A good inspection system lowers these fault calls. With a smart factory, you can sit in one place and see all the data. You don't have to go there, you just click on a screen, find it, and see if there is a fault or not. It is important to lower these fault calls because it saves time and money.

Matties: Ultimately, it saves defects too, right? Because some are actual faults?

Müller: Yes, some are. You will always have that. That’s normal, but you can save a lot of time.

Matties: Definitely. Is there anything we haven't talked about yet that you feel like we should cover today?

Müller: Earlier, I mentioned the X-ray system is getting more and more important. Some years ago, only a few customers had X-ray inspection because it was expensive, but PCBs are getting smaller. Solder joints are more underneath the components and not just around the components, so there is no way to inspect it via 3D AOI or whatever. You can't see it.

You may have an electrical test that shows it's working fine, but for how long? X-ray inspection is very important for the automotive, military, and aerospace industries. Then we have the two strategies I mentioned before. You can have a complete inspection of the entire PCB, of every solder joint, or you can just quickly inspect some of the components, like processors, VGAs, or FPGAs in high resolution and 3D. You have to have 3D inspection of the X-ray inspection.

Let me give you an example for when I talked about 3D AXI and providing value. We had a customer that had problems with his PCBs. They were broken at the end. He had taken a normal X-ray system and found voids in the bigger components. We didn’t think there was a void between the component and the PCB, so we used 3D AXI where you have layers upon layers. We found out that the void was not inside the solder joint between the component and the PCB, but it was inside the component. There was a component with a package and contact, and the void was inside this package. We called the customer and he said that he had changed his supplier for these components to a cheaper one.

Matties: You get what you pay for.

Müller: It didn't work. We found out that it wasn’t a problem with his production process, so we gave him valuable advice.

Matties: Very valuable. You're revealing a world that's never been seen.

Müller: It’s very interesting to see voids or head-in-pillow defects even in the smaller solder joints where the solder joint isn't correct. This is a big issue.

Matties: I know we don't look at inspection as a value-added process, but there’s no doubt it adds value because it adds data and data is incredibly valuable.

Müller: Yes, data is very important, but you don't just collect data. You have to do something with it.

Matties: You have to interpret it, understand it, and then act upon it.

Müller: Yes, and then you can add value to your entire process.

Matties: Right. And ultimately increase yields, capacity, and capability.

Müller: Yes.

Matties: Thank you so much for sitting down and chatting with us. We appreciate it very much. It's always good to hear from you.

Müller: Thank you. It was great talking with you.

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