Metcal Brings Big Science and High Reliability to Hand Soldering
Recently, I met with Metcal’s Product Support Engineer Robert Roush. Metcal, an OK International brand, unveiled a patented hand-soldering technology at this year’s IPC APEX EXPO, in San Diego. It sounds like a real game-changer, from a reliability and process control standpoint, and promises to bring a new level of science and control to the world of hand-soldering.
Judy Warner: Robert, why don't you start by giving me a brief description of Metcal's history and product focus?
Roush: Metcal's been around for a little more than 35 years. They came to market with SmartHeat®, a new technology at the time, which used Curie point heating to really change how soldering was traditionally performed. Over the years, we've expanded our focus into convection rework, capital equipment, and fume extraction. Overall, our product line has evolved, and today we’re focusing on risk mitigation, process control, and automation—key industry pain points.
Those are seen to be the key tenets of the industry that everyone is focusing on—the bread and butter of hand-soldering rather than just getting a piece of iron hot, which has been traditionally the focus of industry players. There's been an element of keeping up with the Joneses, but the core technology hasn't advanced much in more than 30 years. It has just become more competitive, with minor changes in power and features overall. The evolution has not really moved the needle much in terms of technology and delivery on key customer needs.
SmartHeat has always been the outlier in that realm and just one of many solutions. Metcal has always done things a little differently. We've held several patents over the years and every one of the patents has done something differently; or, we've taken a different focus and tried to solve a problem with a new product, that may not have been known to the customers at large.
Warner: Sounds like Metcal has been driving hand-soldering technology, which is a great position to be in the marketplace. I understand there are some inherent challenges relative to process control and reliability. How do those impact the final product?
Roush: Many challenges are associated with hand soldering. There's hardware, materials, and the personnel side. On the hardware end, you do a lot of things to control the type of solder, the amount of heat, the time on the joint, the flux chemistry, the solder chemistry, and the components that go into it. All those factors are controlled going into the soldering process.
Pair that up with operator training to an industry standard. Production supervisors hope that with tight process control and well-trained operators, at the end of the day, when they put the hot iron to the joint, they get a good solder joint. That’s really what happens on the production line. You strive for a good, consistent result every time. Then you inspect and move on to the next stage.
Warner: I visited a high-end EMS company that focused on NPI and prototypes recently. One thing they pointed out to me was that there was not a single soldering iron in the place—which surprised me. They had instead bought selective soldering equipment to address their own risk mitigation. Is this an effective strategy?
Roush: Selective soldering has some advantages over hand soldering, but there's also some disadvantages that can't be solved with a selective soldering machine. With a selective soldering machine, it's possible to program many of the variables into the process and eliminate some of the risks that an operator may add to the mix.
Even the best solderer has a bad day from time to time. Hitting that joint 100% of the time and making sure the standard is adhered to is challenging even with the best of operators. A selective soldering machine, in that case, can just be programmed; ideally, at the end of the day, it is successful.
But the selective soldering machine has expenses too. There's a lot of programming involved. There are still components that are either temperature sensitive, or sensitive to some of the solders. You're trading one risk for another. You're trading the operator's risk versus whether the selective solder machine can accomplish the task without damaging the board.
In a prototyping house, where parts may be one-offs, or a batch of few that could cost thousands of dollars, it's important to mitigate risk as much as possible. I'm sure they feel that eliminating the operator and going to something more automated helps mitigate that risk. What they’ve done is removed the human element, but introduced more process control and hardware risk, with the hope that they come out the other side with a product that can go into mass production.
Warner: That's interesting. Before we move on, you mentioned standards. Are the IPC standards clear and straightforward? Has anyone at Metcal gotten involved in collaborating on those standards?
Roush: The IPC standards, especially when it comes to hand soldering, are primarily visual based, whether it’s IPC 610, or the J-STD-001. They provide reference materials for what every type of solder connection should look like.
The standards assume that if you control process variables and an operator has been properly trained, and the solder joint looks good at the end of the day, it will be a good joint. But because the standards are visual based, there’s no inherent guarantee. The standards just provide a visual to compare whether the operator has met the standard and whether the inspector or the automated inspection equipment employed afterward has met this visual standard. In that context, that's as far as standards have gone.
Our chief technology officer is working with IPC in that regard. He discusses our future, and he's involved in the development and reviewing the standards and participating, pushing those standards forward and making sure that we have a robust set of controls in the industry.
Warner: Regarding the challenges you mentioned and all the moving parts of processes and standards, you mentioned SmartHeat. Will you explain how Metcal, as a 35-year-old company, has looked at these challenges and how you're currently addressing them in the marketplace and helping your customers mitigate risk?
Roush: Metcal introduced SmartHeat 35 years ago. As of today, Metcal soldering stations are all based on SmartHeat technology. With SmartHeat, we use Curie point heating, which allows very precise temperature control within 1.1 degree of accuracy and essentially eliminates any overshoot. It's all based on power-on-demand. We only apply enough power to effectively solder a joint. Then it backs off and you can move on to the next joint.
Over the last few years, we've looked more closely at what a good solder joint is. We've developed a new technology that we introduced at IPC APEX EXPO 2017, which looks at how a solder joint is formed. The technology is called Connection Validation (CV). CV provides real-time feedback to the operator and indicates whether they’ve successfully achieved a “good” solder joint, or if there’s been some fault during the soldering process. It’s revolutionary; current systems are open loop and always have an element of risk.
Warner: Can you tell me about the features and benefits of this new technology?
Roush: In any successful soldering process, you have an intermetallic that forms as the solder bonds with the pad composition. During soldering, they form an intermetallic alloy.
We know that one of the challenges with the visual standard is that it can look good, but still be bad from an electrical or intermetallic formation standpoint. We understand that when you have too little of an intermetallic formation, you get a cold or dry solder joint. Too much, and you have embrittlement. There's an optimum right in the middle.
What we've done is develop a technology that monitors, in real time, the solder joint as it forms, and calculates the intermetallic formation; it provides feedback to the operator that the intermetallic formation is formed at the ideal level. Coupled with the visual standard, not only does this result in an external joint that looks good and meets the visual requirements, but now you have an internal control mechanism that ensures the intermetallic is ideal. This provides a "belt-and-suspenders" approach to soldering where you've only had a "belt-and-fingers-crossed" solution in the past.
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Warner: You're really applying more science to it at the molecular or chemical level.
Roush: Absolutely. As the industry's been evolving in the last decade, technologies haven't really changed much. A company can come out next week with a little bit more power, a slightly more accurate thermocouple control loop, or some aspect to finely control the things they know they can do.
We've taken a different approach and looked at the joint and provided something that examines the process that people care about. You can add more and more power, but it doesn't tell you whether your solder joint has been formed correctly.
Warner: At what point do you find out that joint has been formed improperly? Is it in the field? Is it after multiple heat excursions through the oven? When does it usually fall apart?
Roush: If you're lucky, you'll catch it during some final inspection stage before your PC board leaves the production line. But many times, you’ll find it in real life, where it's failed at some point after it's been installed in the next assembly.
One of the major reasons we looked at what constitutes a "good" solder joint is the number of industry failures, where the solder joint was the point of failure. Could we have corrected this if we found it early enough? Because of how the processes are controlled today, it's hard to tell. You're looking at the solder joint, and it looks good. So, it must be good. But that wasn't sitting well with us. We knew we could do better. Think about solder joints going into brake assemblies, for example; lives are on the line.
Warner: That is so often the case.
Roush: There are cases in the industry when a failed solder joint might be an inconvenience, where the product was just buggy and you exchanged it with a new one. But you don't want it to happen when you’re driving and your brakes give out because the solder joint was faulty. Automotive is such a harsh environment, with temperature extremes; the demands on the electronics are so high that you want some assurances that at least the solder joints are correct and everything else was designed correctly.
You don't want it to go into an airplane or a satellite where it’s hard to repair. You don't want a failure where there's a lot of liability on the line.
Warner: What kind of testing and case studies have you done to prove out the technology? And what hurdles do you anticipate ahead, either in the technology itself, or in the industry adoption of it?
Roush: We understand there are challenges associated with any new technology. I think the biggest one associated with that is adoption from the line operator, the person who's going to be wielding the tool. We've talked to all types of people, across the industry, whether they've been in the industry for six months or 20 years; they've all done the same thing and developed their habits over time. They're stuck in their ways.
When you introduce a new technology that may require the operator to stay slightly longer on a joint to make sure it has formed the intermetallic compound, it may be challenging to adjust, simply based on their entrenched habits. It makes it challenging for any operator, myself included. I've been soldering for decades. It takes a while to let go a little bit and trust that the tool is doing its job. That's probably the biggest challenge—getting the operators to rely on the feedback from the hand piece.
When you're a pioneer, it's always challenging to get people to accept a new idea that really works. You must really prove it. From a testing standpoint, that's what we've done with the development of this technology. We've done numerous joints, and then we’ve gone back out and cross-sectioned them. We've controlled every other variable, and then cross-sectioned using this tool, to make sure it is meeting our requirements.
In every case, it has absolutely performed right in that optimal zone of IMC formation.
This new technology allows errors to be found that customers didn't even realize existed in other aspects of the soldering process; they didn't bother to do cross-sectioning because it looked good.
One example: Barrel fill is always a challenge with through-hole components—making sure there is enough solder through the entire barrel so that it meets requirements. We've had customers come back and say, "We used your tool and then we cross-sectioned it and we realized that we weren't getting barrel fill even." So an added benefit is that it’s prompting customers to go back and look at how they’re doing their soldering processes.
Warner: Giving them verifiable feedback is crucial. Like you said, "Old habits die hard," and trusting something new can be challenging. However, taking the time and discipline to cross-section and check their work will help build confidence in time, I would think.
Roush: It really harkens back to the fundamentals of soldering—proper tip selection and proper application of solder. When you do that, and use the new technology we've developed, it works in conjunction and it prompts you. Ironically, we've had production managers and line supervisors saying the technology is great, while operators initially push back, because it exposes the bad habits they’ve developed and didn't realize they had. Inherently, they have developed bad habits over time, and that is really the challenge associated with our new technology. Fortunately, process engineers are seeing the benefit, staying with it, and helping their operators work through the initial adoption stage.
Warner: Will Metcal provide a training program or something similar? As new customers adopt this technology, will you have people help walk customers through that?
Roush: Absolutely. We spent a lot of time developing the technology, but also training our own internal staff. We've done numerous training sessions to really understand and delve into analyzing the application itself, and then matching the new tool to their application, to make sure that they're getting the most out of it. And we're developing programs to optimize tip selection and expanding our cartridge and product selection in conjunction, to make sure customers can go to this tool box and pull out what they need to solve a problem. Compare that to today, where the common solution is to use a 2.5 mm chisel in most cases.
We've fine-tuned our tip selections going forward to really optimize the system to match the joints and loads, to increase chances of best performance and decrease issues where it seems to take a little longer. We want to make sure that customers are getting the same performance today. You may be happy with today’s system, but with the new system tomorrow, you're getting the same performance plus the added benefit of knowing that the inner metallic formation has been correctly formed.
Warner: What an amazing story. How did you demonstrate this technology in your booth at APEX?
Roush: CV was the centerpiece of our newly designed booth. We did live demos, and walked people through exactly how this technology works. We had multiple stations where people came up and experienced the technology live.
In conjunction, we have also developed a technical white paper, "Risk Mitigation in Hand Soldering," which is clearly at the crux of what our new product addresses. You can download it on our website at: metcal.com/cv.
Warner: The stations in your booth were hands-on?
Roush: Yes, hands-on. We walked people through exactly what’s happening and demonstrated the results. We're extremely excited about it; we’ve been working on it for about three and half years. It’s been a long time coming to get the technology to the point where we’re comfortable and excited to take it to market. We think it’s going to shake up the status quo in such a positive way.
Warner: Do you have any final thoughts on our discussion?
Roush: Yes, at APEX we also revealed our new brand and logo. We're really excited about it, and we feel that it much better represents Metcal and our brand essence and values in the market. Also, we see this new Connection Validation technology as a foundation for lots of new developments. You will hear much more about this technology as it evolves, and as we roll out other features and benefits in the coming months and years.
Warner: This has been fun to learn about, Robert. Thank you so much for your time. Good luck with your new product; it sounds like you’re bringing something great to market.
Roush: Thank you.
About Robert Roush
Robert Roush is a 9-year veteran of Metcal. He learned soldering applications and techniques first hand while spending 11 years in the U.S. Marine Corps prior to obtaining both a BS and an MBA. Robert is responsible for getting Metcal's top NPIs to market.
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