The Benefits of Vapor Phase Reflow Soldering

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JB Byers, vice president of technical support services at A-Tek Systems in Longmont, Colorado, recently gave a presentation on vapor phase reflow soldering at the SMTA Boise Expo & Tech Forum. After his presentation, I-Connect007 briefly talked with him about how the process can help reduce voids and lower operating cost. 

Barry Matties: In your session on vapor phase reflow soldering, you did a great job of explaining how you're able to eliminate voids through a vacuum in the process. Talk to us about that and its other benefits.

JB Byers: With power or structural applications, if you don’t have the right amount of solder designed by the engineers, you don’t get the structure, energy, or heat transfer that’s necessary. While the solder is under a liquidous condition, the vacuum process within the reflow of vapor phase, reduces the voids that can overcome those problems had the voids been left in. When you reduce the atmospheric pressure around the voids, it causes them to grow and break the surface tension of the liquid solder bubble. As you return them back to atmospheric pressure, the voids are dramatically reduced.

Matties: We're now seeing some alternate technologies, like laser technology. How would this compare?

Byers: They all have a specific role to fill. I like the vapor phase because it's fairly broad on what it covers. It is a great technology for manufacturers that struggle with the convection oven due to dissimilar sizes, material board layouts, etc. In a vapor environment, the applied heat and energy to the board is very homogeneous and very even throughout the board.

Matties: All things are equal.

Byers: Yes, and that's a real benefit. With a convection oven and some of your larger heatsinks, it takes a lot of energy to get them up to temperature and to reflow the solder. By the time they're at temperature, the small surface mount components around them may have dramatically overheated. 

Another benefit of the vapor phase is that the maximum temperature—the boiling temperature of the fluid—is limited. No matter how long you’re in the reflow chamber of a vapor phase, the maximum temperature your board will reach is 230°F.


Matties: The temperature doesn't continue to climb.

Byers: That’s right.

Matties: Interesting. How widely used is the vapor phase?

Byers: It's growing in the United States because, in my opinion, we've actually decided to start making things here again. We're bringing back a lot of production lines. Throughout my 30 years in this industry, I watched production lines continually move away every year, but I believe their numbers have increased in the last two years—for the first in a very long time. 

Matties: Why hasn't this technology been adopted on a wider scale?

Byers: It is growing, but because many of these products are easy to manufacture, there's no reason to change from convection.

Matties: Is this for more high-end medical, high reliability?

Byers: Mostly high reliability. The big players are starting to look at it from the technology side.

Matties: The cost of utilities has gone through the roof. Does this lower the cost?

Byers: Yes. Typically, a vapor phase will use less than a third of the energy than a standard convection oven uses. With vapor phase, we only need to create energy when we're actually reflowing boards. When we're not doing that work, we set it at a very low boiling temperature, the minimal amount of energy. If we need energy, we create it. That’s unlike convection ovens, where all zones maintain heat at the same time.

Matties: What will prompt more exploration of this, particularly when the infrastructure is already in place and it's hard to pull something that's generally working.

Byers: We see customers want to upgrade their processes. Many of them are well aware of vapor phase and are looking to learn more.

Matties: Is this an automated process? Does it require a certain skill set? 

Byers: Only a minimal skill set is needed. Maintenance technicians need a general understanding of, for example, reading schematics—lefty loosey, righty tighty. Process engineers can be trained to operate the machines and certain features of its software. 

Matties: In today's world, data collection, statistical process control is a factor. I'm sure you have traceability.

Byers: Yes, we can download, dump data, or whatever is needed.

Matties: JB, thank you very much. This has been very informative. 

Byers: Thank you.


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