Indium Blog

Electronics Assembly: An Introduction to Particle Size and Printing Smaller Area Ratios

Phil Zarrow: This video is for anyone interested in the role of solder paste particle size with regard to reflow and printing. 
Ed, what's the role of particle size with regard to printing challenging area ratios?
Ed Briggs: Typically, we see people looking at small particle sizes when the area ratio becomes very small, so 0.66 typically is the area ratio that people are shooting for.
Phil Zarrow: Right.
Ed Briggs: Once you get below that, people are typically looking at smaller particle sizes. The testing that we've done shows that you can actually print smaller area ratios with a finer particle solder paste. We can get down to 0.5 area ratio very often, with a smaller particle solder paste.
Phil Zarrow: We are still talking about the old Five-Ball Rule?
Ed Briggs: When you're looking at aspect ratio as far as laying the particles side by side ...
Phil Zarrow: Right.
Ed Briggs: ... and the narrowest part of the ... Yes.
Phil Zarrow: Yeah.
Ed Briggs: Absolutely.
Phil Zarrow: What are some of the trade-offs of the reflowing of things?
Ed Briggs: On the reflowing of things, and there's always a trade-off.
Phil Zarrow: Of course.
Ed Briggs: With the finer particles, typically you see there's more surface area, and so that means there's more increased surface oxide. That oxide makes it more difficult for the flux to work; so, typically you see your process window for the reflow gets a little smaller with the smaller particle sizes; and when you get down to a Type 6, you very often need nitrogen ...
Phil Zarrow: Oh, okay.
Ed Briggs: ... to help the flux out.
Phil Zarrow: That's where nitrogen starts to come in.
Ed Briggs: Okay.
Phil Zarrow: Very interesting topic, Ed. Where can we go for more information?
Ed Briggs: Visit us at, or email me at
Phil Zarrow: Ed, fascinating as usual. Thank you.
Ed Briggs: Thank you.


Keywords: Phil Zarrow, Ed Briggs,, particle size, area ratios, particles, reflowing, flux, nitrogen, Type 6, surface oxide, Indium Corporation