Issue link: https://iconnect007.uberflip.com/i/565949
64 The PCB Magazine • September 2015 over 120°C. We've taken molded sensors and put them through a thermal cycle. What we no- ticed is, with plasma, after 5,000 thermal cycles, we didn't see any delamination or any failures within the mold. On the non-treated plasma samples, after 5,000, you already see the edges starting to delaminate. You see weaknesses in those areas. Let's imagine if you had 10,000 cycles—or even 50,000 cycles, depending upon how often your car goes from low temp to high—those sensors can easily fall apart and fail. If you have a failed sensor, you can have a problem with the car. These are the types of things that we look at. Matties: So you have em- pirical data that justifies the expense or the process step. What's the cycle time in the plasma? Doan: Cycle time is fair- ly quick, depending upon what the customer is treat- ing. That's the good part. If they're trying to do bulk re- moval, it may be longer. It can be as much as say, five minutes, or it could be as lit- tle as 10–20 seconds. A lot of the treatments, in the case that you're talking about, with the head-in-pillow example, it's a 10-second process for most people to use plasma to treat. You send your part in for 10 seconds, you clear off the ox- ide and any contaminants, and then the part's ready to be treated. Matties: Because you have to start with a clean board, have a great stencil, bring in the right amount of paste, and so on. The idea is to elimi- nate every variable at each step, and that's what you guys are all about. Doan: Yes, that's our goal. Matties: Anything that we didn't talk about that we should be sharing, or that someone should know about plasma? Doan: What we're doing now, beyond just doing surface cleaning and activation, is we're also using plasma to coat. This is from a fin- ished product reliability standpoint. Let's say you have a finished board or a finished circuit. What we can do, instead of just using a tradi- tional conformal coating—which is fairly thick—is use a plasma coat- ing that's very thin, and then you can package this easily. It offers a nice resistance to hu- midity and water and such. It's minimal, it's not as thick as your traditional conformal coating, but at the same time it offers good enough protec - tion for your package device. Matties: Is this good enough for high-reliability automotive, or is it shelf life? Doan: It's more for shelf life. In automotive, I think you would still need a thicker coating. With this, it's thin and it's not scratch resistant— you can easily scratch it off. This is more to keep the shelf life and protect the circuit from any type of oxidation or any type of degradation. It's good for when you're manufac- turing large parts and you're not shipping and packaging them instantly. Matties: Because if we let them sit around, then contamination creeps back in. Doan: That's right, so that's what it's really there for. Matties: Jonathan, it was nice talking to you today. Doan: It was good talking with you. PCB CARMAKERS NOW EMBRACING PLASMA TREATMENT continues FEAturE IntErvIEw on the non-treated plasma samples, after 5,000, you already see the edges starting to delaminate. you see weak- nesses in those areas. let's imagine if you had 10,000 cycles—or even 50,000 cycles, depending upon how often your car goes from low temp to high— those sensors can easily fall apart and fail. If you have a failed sensor, you can have a problem with the car. " "