Computer professionals know all about the little blights such as viruses and bugs that can wreak havoc with computer systems, but according to Ralph Mitchell there may be another category of culprits: fungi.
Under laboratory testing conditions, fungi, and in particular a strain known as Aspergillus versicolor, have been found to corrode the polymer layers used to coat and insulate the complex integrated circuits within computer processors.
Mitchell, the Gordon McKay professor of applied biology at Harvard University, cautions that so far the findings are preliminary and strictly laboratory-based. Having said that however, he explained that if the results can be demonstrated under real-world conditions, it might be proven that fungi growth could account for at least some of the sudden, unexplained electrical failures that can occur in computer and electrical systems.
Mitchell, and his research colleagues working at both Harvard and the Massachusetts Institute of Technology (MIT), first came upon the fungi theory after noticing something odd.
“The MIT materials research lab was looking at polymer packaging (insulation) and they were getting failures, and they noticed that the stuff was slimy. So they called us,” Mitchell said.
“When we looked at it, we found the packaging materials were really heavily contaminated by microbes, and so we isolated the microbes, took some fresh packaging material, and (found that) the microbes grow on this material and penetrate through the packaging material, which happened to be polyimides. Of course, they ruined the dielectric. What you are really seeing is that they are not necessarily chewing the polymers themselves, but these polymers are heavily contaminated with chemicals in the manufacturing process. They are not pure.
“Probably the organisms are using the impurities, but if you get one fungus running down through an insulator, that fungus is 99 per cent water, and you’ve essentially ruined the insulation. You’ve essentially punched a hole through with water running down, and so you’ve lost your insulation. That’s what’s happening with these things, as far as we can tell. “
Mitchell explained that the growth of fungus on computer and electronics equipment only occurs under certain environmental conditions.
“The question that you need to ask in all of this is why doesn’t it happen all the time. The answer almost certainly is because computers are kept dry. The real problem in all of these situations is if you have an open machine, where you have high humidity. Let’s say you’re in Florida with no air conditioning on, or more typically, you have a machine in storage and you turn it on and it doesn’t work. The question is did it fail because there was something wrong with it in the first place, or is it possible, using the vernacular, that it went mouldy? It’s a huge problem for stored equipment.”
Mitchell said fewer and fewer large systems are sealed in order to accommodate component changes, and that could lead to fungi growth. He also added that the larger and more complex the system, the greater the possibility of contamination.
“I’m thinking of industrial machines where you’ve layered electronics, that’s where these polyimides are important. If you have any very large layered electronics machine, you’ve got a lot of insulation and that’s when you need to worry where these things are stored.”
So far the scientists have only found fungi growing on insulating material, but that is the only place that they have looked. Mitchell said that unless an electronics manufacturer offers them equipment to experiment with and examine, the research into this topic is likely to go no further.
“What I would love to see tested is whether material that has been stored for prolonged periods fails. I really don’t know the answer to that question, but I think it is an important question. This is a potential source of serious problems that hasn’t been investigated in the electronics world.”
