Issue link: https://iconnect007.uberflip.com/i/1243344
12 SMT007 MAGAZINE I MAY 2020 to print once, wipe the board, and print it again because the solder paste stiffens up. That's called a poor response to pause. A better sol- der paste—and this is one of the things my col- leagues at Indium Corporation understand—has a good response to pause. In other words, you can leave the solder paste on the stencil for an hour or more, and it doesn't make a difference. One customer changed to Indium Corpora- tion's solder paste and no longer had to do this wiping of the board when they stopped the line every couple of hours to do something. In the past, each of these times, the paste would stiffen, and they had do to the "print-and-wipe" proce- dure. At the end of the day, it ended up being 20 minutes or more of lost production in an eight- hour shift; it was a bigger deal than might first appear. The new solder paste improved their productivity a couple of percentage points, but it improved their profitability 8–9%. With cost estimating software I had developed, I was able to calculate all this, and we ended up writing a paper on the topic. Feinberg: Do you see a significant change in the volume of solder that is being used as a per- centage basis—not by tonnage or anything— for a solder paste versus bar solder for wave soldering? Lasky: Solder paste has become more domi- nant, and that's the case because certainly sur- face-mount technology, for a lot of our prod- ucts, is the only thing used. I don't think there are any cellphones that use wave soldering. Feinberg: No, I wouldn't think so at all. Lasky: But don't discount bar solder. Twenty-five years ago, some people said, "Wave soldering and through-hole are going to go away. We shouldn't even pay attention to those," but that's nonsense. They're not going to go away probably ever. Feinberg: One of the things with through-hole is that with the change in the last decade to lead-free solder, the flexibility of the solder has reduced significantly. And when you have a component that's mounted through a through- hole and then soldered versus placed on a pad and then soldered, the reliability is signifi- cantly better with the through-hole. This behavior hasn't mattered so much until the reliability needs have increased, which they have increased significantly in the last 36 months, thanks to autonomous driving and the volume of electronics in transportation. That may be slowing down the decrease in wave soldering, although—from an economic stand- point—it makes no sense. We're kind of at a crossroads right now. Lasky: I have to push back a little bit on that. I would agree that one of the reasons wave sol- dering is not going to go away is some of our electronics products have a lot of plugs. Some of those plugs want through-hole for mechani- cal strength. Feinberg: That's true. Lasky: A lot of the components that are made that are critical for autonomous driving only come in surface mount formats because you can't beat SMT's interconnectivity. If some- body said, "We want to make an Intel micro- processor be through-hole," it wouldn't be possible because there are too many intercon- nects, and you can't make through-holes that small. I agree with most of your thoughts on through-hole, but we're going to have to make surface-mount reliable enough for situations like this. Feinberg: Some military components are going back to leaded solder. It's a temporary fix, but it is a fix in some cases. Lasky: They never had to go lead-free, of course, but a problem for the military applica- tions is getting something in a tin-lead format. Matties: When you look at the solder paste arena, what do you think the critical knowl- edge is that people need to have today? Lasky: It doesn't appear to me that new alloys are going to be embraced by the industry for