Super Dry’s Novel Approach to the Drying Process

Estimated reading time: 12 minutes

Starkey:

Heimsch: No, vacuum was a method used to create a similar kind of acceleration that the low humidity does. Vacuum ovens were used for a long time, and in the early days of the introduction, 10–12 years ago, of these low temperature drying machines, customers compared them to their vacuum ovens. Saturated, weighed, used the same procedures, and found them to be virtually equivalent across a variety of component configurations and tape. There were some occasions where the vacuum oven was a little quicker and some where the dry cabinet was quicker.  The other reason that it's really significant is because previously, (and still people do), the only way to salvage overexposed components that are on tape and reel was to take them off the tape and reel, bake them, and then have them re-taped. The tape can't handle more than usually 50°C. But at 50°C and 1% or 0.5% RH, they will dry. Not only is it a better process from oxidation and all that we were talking about before, but it eliminates the time and expense of de-taping, de-reeling, re-taping, re-reeling components.  

Starkey: How does the system integrate with your established systems of component storage and component logistics management? Is it fully integrated?

Heimsch: It is. In the automated warehouses, there will be, if chosen, a floor life reset area, and then the rest of it is safe storage below 5%. The system, when it is approaching an expiration time, because time in and out of the safe storage is kept track of, will say, “This one needs to be put into a reset area.” And then when it's ready, the system knows and when it has a spare moment will go get that out and move it.

Starkey: But effectively managing this system, you've got above it an automated management system.

Heimsch: That's right. And if you have a more manual shop, you can do similar things with handheld scanners to keep track of the in and out. The inception of the cabinet was also for the purpose of not having to move components just because they were dried. Because there's no damage occurring by leaving it in there longer than what it needs. Some people choose to do that, depending on their volume and mix; that was the original, "Gee, I need something that I can do both with." And of course requirements, concepts and factory logistics have moved us on into other offerings. We have one that offers two different temperatures at 1% humidity and tracks 20 different batches. So, you can have some at 40°C, the safest of drying temperatures and some at 50° or 55°C maybe because of the tape and reel issue. To me, that's more of an iteration. The real process change was finding something that dropped that temperature. The same way that process change of eliminating nitrogen and yet still not oxidizing was a major threshold in the drying technology.

Another thing that’s always been there but is now growing in need and demand is very long term storage. I mean, years beyond those that the component manufacturers have any handling recommendations for. Military people and automotive people have certainly needed to do this and have for a long time. Because even moisture-barrier bags alone are not good enough for five to 10 years. We've got customers that need to keep things for 20 years. They pretty much understand that the 5% storage environment is a solution. They've also discovered, having done it, that it very well arrests the oxidation, but that intermetallics still grow over time and can render a large percentage of stored devices useless. So, having seen this empirically, we've had customers ask us to add a capability to go below ambient with their long-term storage environment. Because by dropping the temperature you can significantly reduce the intermetallics.

You have to be careful. You can't just freeze it. You can't just keep going low because you got the tin whisker issue. But just like the 60°C/40°C oxidation time compromise, empirically it's been determined by a number of users that 10 to 12°C is a useful yet still safe temperature. So, we had our original insulated enclosures with the 0.5% drying capability with refrigeration to take them down to that temperature. Now, 0.5% relative humidity at 23°C room temperature is 3%, or 4% at 10°C, but it comfortably stays below 5%. There's no more moisture in that environment than there was at the higher temperature, but technically speaking, it's a higher relative humidity. Now, whether that is a problem, nobody's really had the time or the reason to see yet. But you think about it, there's no more moisture, and this is an environment that you're not opening and closing the doors. It's just staying there. So, you're down to a half percent, now you lower the temperature. Yes. You raise the relative humidity. But is relative humidity a suitable measurement for the application? It's not a rhetorical question, but it’s one of those questions that’s out there.

We’ve developed or had developed and utilized quite a different zeolite crystal in our high-temperature 60°C drying cabinets than we do in the ones that are only ambient. It's much more difficult to get down under 1% at 40°C or particularly at 60°C for the recovery time. So, it's a different desiccant in those cabinets. So, who knows, maybe a different desiccant in the lower temperature ones. But to me, the question I haven't had adequately answered is if there are no more water molecules in that environment than there were 10 degrees ago. I agree. It's higher relative humidity, but does it matter? Is that really the guideline?

It's no longer just military and automotive; with shorter product life cycles and component availabilities, more and more people are forced to buy components forward. Especially with the counterfeiting ramifications, you just can't go at the last minute and trust finding a component or finding it and then trusting where it came from. The need to have long-term storage is beginning to spread out to less classic applications. To be able to get electronic parts for a car 20 years old overnight is pretty amazing, but they've been at it for a long time. So that's another demand that’s evolving.

Starkey: Rich, it's been a really fascinating few minutes conversation.  I've learned an awful lot from it.

Heimsch: Great. Very nice to see you.

Starkey: I'm sure our readers will enjoy it as well. Many thanks.

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