Phil Zarrow: What are some of the printing differences between no-clean and water-soluble solder paste?
Ed Briggs: Interesting question, because you may not think there may be a difference between the two.
Phil Zarrow: Right.
Ed Briggs: Actually the water-solubles don't print as well as the no-cleans. All the testing that we've done across the particle size – type 3, type 4, 5, and 6 – we find that the no cleans print better than the water-solubles. Some of the thought behind that is that perhaps the rosin, which is basically tree sap, does a very good job at stencil roll, once it fills the aperture, and then maintaining that shape once it's printed into the aperture. The rosin does a very good job in doing that.
Phil Zarrow: Ed, what are some of the reflow differences between no-clean and water-soluble solder paste?
Ed Briggs: A lot of people think that the water-soluble chemistries are a lot more active and therefore give a lot better results in reflow profile. That's not necessarily always the case. They're very active in the frontend, yes and they are very good at removing existing surface oxide. As you get further down the process in the reflow profile, they don't do very good job in the oxidation barrier. As things begin to re-oxidize, the no-cleans, the rosins that you find in them are excellent oxidation barriers and therefore do a much better job. Especially on really small apertures that are very sensitive to the oven environment.
Phil Zarrow: Very interesting topic, Ed. Where can we go for more information?