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Nolan Johnson speaks with Super Dry’s Richard Heimsch about how the need for dry storage solutions has increased throughout the pandemic, including further demands for traceability and automation capabilities.
Nolan Johnson: Richard, we were just discussing that we’ve learned a lot in the industry about supply chain through a year of pandemic. Those lessons relate to what you do at Super Dry as well. What have you learned and seen?
Richard Heimsch: I think that it is closely related to issues of long-term storage of electronic components that have been in processes already in certain industry segments—automotive, military, avionics—for many years, with 10-, 20-year storage requirements that far exceed manufacturer’s guidelines. This left companies on their own to determine the usability of the components in that timeframe. Demand has been expanded into other industry segments, even without new supply chain pressures, by shortened product life cycles and component availability. Obsolescence of components and content of an end product that needs to be supported longer than the published available life of the component itself. Both of those combine to increase the need to purchase forward.
Storage times wind up exceeding the manufacturer’s guidelines. Your two primary risk factors with moisture-sensitive devices are encapsulation damage and solderability. The encapsulation damage comes from the absorption of excess amounts of water, which are then reflowed. The moisture in the component tries to escape too rapidly, bypasses the elastic limit of the plastic or the epoxy biphenyl encapsulant molding compound and causies a micro crack, which in turn manifests most typically as a field failure—more often than as an end-of-line defect. It’s seditious damage in that the moisture will escape at the weakest part of the package, which is often the underside of a BGA, for instance.
But even if you’ve controlled the components so excess absorbtion is not an issue, the oxidation that occurs from leaving components in ambient atmosphere will dramatically reduce the solderability and has to be taken into account. We do long-term storage as a service at a couple of our factories in Europe and, among other things, periodic testing has proven a couple of interesting facts. For instance, nitrogen was traditionally used to store devices safely. In fact, a dry, low-humidity atmosphere will stop oxidation better than a nitrogen atmosphere, while also stopping the absorption of moisture. But the key fact is that dry air stops oxidation better; we have a lot of data since we have been doing this storage as a service.
The principle involved is that the tightly bonded O2 molecule in the air is a less aggressive bearer of oxygen than the loosely bonded oxygen atom in a water molecule, and at the humidity that we’re storing, it’s a moisture vacuum. You’re looking at
Another area that is impacted is the intermetallic growth. Intermetallic growth is exacerbated or certainly increased by high-temperature baking, which was a traditional way to restore floor life to components that had expired. Time and temperature increase intermetallic growth. Even with the low humidity, years of storage cause the intermetallic growth to continue to occur, and there really is no workaround for those severe cases. What has been clearly proven the same way as the nitrogen and oxidation is that lowering the temperature along with the
But even in the medium term, the automation of tracking of usage, and the expired floor life, is always a critical factor. That tracking has become more and more automated over time—automated in the sense of being able to go to the extreme of robotically controlled warehouses. But in a smaller-scale, high-mix, low-volume environment, scanning and storing component reels as they go in and out of active use in final assembly will better protect and provide traceability for those components.
The storage of a mixture of MSL levels, how much time has been used, how much safely remains, identifying which part to pick, are just a few examples of what can be tracked and controlled even without large-volume, robotically operated warehouses. The shop with a half dozen lines or less can achieve the same level of control, and those are the kinds of tools that continue to be refined within our Smart Storage Management sphere of products.
Johnson: Richard, could you give a quick rundown on your products and services?
Heimsch: We are moisture management specialists. We provide a wide variety of both storage and drying environments for, in this context, electronic components. Those range from benchtop storage to walk-in dry rooms that can safely store—meaning stop the clock for unlimited periods of time as defined by the IPC standards—and also provide a floor life reset of expired or close-to-expired components that do not induce oxidation or intermetallic growth the way traditional high temperature, like 125°C or 90°C, baking will do. Combining lower temperatures, 40 to 60°C, with ultra-low humidity, 1% or less, will dry at virtually the equivalent speed but will not induce the oxidation and the intermetallics. The two benefits are: the same medium, location, room, enclosure can be used as both a floor life reset and an unlimited safe storage environment without needing a separate baking process and separate baking equipment and separate floor space; all of that is traceable.
Johnson: How does traceability fit?
Heimsch: It relates most directly to the moisture sensitivity level of a given component. Every component has an MSL which dictates the amount of floor life it is allowed before it becomes dangerous to reflow solder. And that could range from unlimited down to 24 hours in basically six stages. So especially for high-mix, low-volume environments—where portions of reels will be used at a time—the need to know how long they have been exposed, how much of this available floor life has been used, needs to be kept track of. How expired are these? Meaning, how much moisture have they absorbed? That’s the principal determinant of the MSL.
Johnson: You certainly caught my attention earlier in this conversation when you mentioned that controlling humidity was more effective than a nitrogen environment.
Heimsch: Everyone except those who’ve been involved with plating processes are typically surprised. I mean, it was the traditional way and the only available way to provide a dry enough environment to safely store in a humidity at which there’s no moisture any longer being absorbed. And so, you have 5% dictated as the unlimited safe storage, unlimited shelf life, in the J-Standards. But the fact that it reduces oxidation better is based on the chemistry and the removal of the catalyst from the corrosion process.
We are doing a lot of long-term storage as a service at a couple of European factories of ours, and part of the service is the periodic testing of components. Other tests are involved (embrittlement), and there are other things that happen in components when they’re stored for years at a time. But oxidation and intermetallics are two that we do test for, and the X-ray analysis of components stored for 12+ months was distinctly compared to a dry or ambient atmosphere and a nitrogen atmosphere.
Not only is it enormously less expensive, but it stops the oxidation better. And similarly, the low-temperature, low-humidity baking is quite a bit less expensive to run and operate, provides storage and floor life reset, and the floor life reset can be done multiple times, which can’t be done at the higher temperatures.
Johnson: To be clear for our audience, you can assist in creating an environment in their facility, as well as providing an offsite facility for storage of components?
Heimsch: Yes, the long-term storage is the service that we offer in Europe. That’s where it started. That’s where it’s been expanding. The same way that so many of the elements of this moisture management process were given birth in the European market, and then eventually worked their way over into North America. I would suspect that it is only a matter of time before the long-term storage service becomes a practical alternative for assemblers and manufacturers here in North America. The focus on moisture management five, six, seven years in front of that here was principally driven by the adoption of RoHS legislation. A component has about triple the saturated vapor pressure at the same amount of moisture absorbed at lead-free reflow profiles and temperatures as you do with eutectic reflow.
So, kind of overnight, virtually every component in a guy’s shop needed to be managed at a much greater level than ever before, and it effectively increases the moisture sensitivity level of a component. Less moisture is a more dangerous condition because the higher temperature and higher ramp rate are forcing that water vapor out more quickly, and you exceed the technical elastic limit that much more readily.
Johnson: What do you see as upcoming challenges?
Heimsch: The climate data logging and the traceability is the direction of the evolution. It’s not necessarily robots, but it is communication networked traceability of even a few dozen reels, or double-sided reflow assemblies where there’s time of significance in between the front side and the backside being reflowed, and then it broadens into other burgeoning subsegments like LED manufacturing. LED storage is significantly sensitive to moisture, so being able to keep track in a way in which you can report to customers and users the condition of a particular part on a particular date 12 months ago, is one benefit this smart connect management provides.
Johnson: Right. I can see that it does help with the provenance of parts. If you’ve got parts well documented and kept in long-term storage, then you have more certainty with regard to their being in spec and their tolerances for manufacture.
Heimsch: And it’s critical even for routine consumption. If you’ve got a 72-hour floor life, and you’re not using that full reel all at one time, it isn’t uncommon for a manufacturer to have reels of components, or a kit of reels of components, that are used over the course of six or 12 months. You have an order for 100,000 units, but those units are spaced out for delivery over a period of time. The components that go onto those assemblies are back and forth from the active assembly line numerous times. And in between that usage, if they’re not safely stored, there’s a reliability risk. It’s one thing to have an intermittent in a handset, it’s another thing to have one in your ABS or heart implant. It moves beyond warranty into significant liability issues.
Johnson: It makes a lot of sense.
Heimsch: That’s why our tagline is “More Than Just Dry air.” Creating a dry environment is relatively simple, but utilizing it effectively requires another level of understanding.
Johnson: I see. It’s one thing to take all the moisture out. It’s another thing to do it in a way that is effective for manufacturing.
Heimsch: Yes, and the raw relative humidity is less important, less significant than the usability. The analogy that I frequently use is that you can get just about any automobile to go 100 miles an hour, but how many of them can you efficiently, safely drive at 100 miles an hour? So, getting to 1% relative humidity, but under what conditions, and then can you use it? The recovery time becomes a significant performance factor, as well as then being able to track and trace the climate throughout the lifespan of its usage and introduction and removal of product.
I would say that treating it as a process is the most significant piece of advice that we could give. It’s not about a piece of equipment. It’s about establishing a process and the series of controls.
Johnson: All very appropriate as the industry actively works toward supply chain resiliency. Richard, thank you for taking the time to go through this with us.
Heimsch: I appreciate the opportunity.