No-Clean Fluxes in Semiconductor Assembly

Phil Zarrow: This video is for electronics manufacturers who are interested in cleaning techniques for Internet of Things devices. It will cover water-soluble and no-clean materials and process. 

 

Andy, let's talk about cleaning and non-cleanable.

 

Andy C. Mackie, PhD, MSc: Cleaning is kind of reaching the end of its life at the moment. As flip-chips become tighter and tighter in pitch, as clearances become smaller and smaller, it becomes more and more difficult to get the cleaning solvent under the chip the way that these devices are now crowded around the central processor. It makes the cleaning process itself, particularly again with aqueous solvents, a very difficult task. That means, in many of the instances customers are looking at no-clean with all of it's implications for reliability and so on as a viable alternative to water soluble. In many instances, particularly flip-chip, for example, where it was previously only thought that a cleaning solution was possible. The enabler for that has really been the ultra-low residue materials.

 

Phil Zarrow: Tell us more about ultra-low residue.

 

Andy C. Mackie, PhD, MSc: Ultra-low residue is becoming critical. It's not an industry term that's very general, but it's something that Indium's really been talking about for the last 4 or 5 years or so. An ultra-low residue material is one that has a flux residue level after reflow of typically less than 5 or 6%, maybe as low as even less than 1% with some of our more advanced materials. That allows, particularly in let's say flip-chip application, the customer after reflow doesn't have to go through a cleaning or a de-fluxing operation. The flux residue after the reflow process that's left behind is very small. That means that when you're doing the underfilling process, after the reflow process, that the underfill can very easily flow under the chip.

 

Again, we're talking about some very tight clearances here. 60 micron is becoming standard and the road maps are now down to 40 micron or even less for many of the flip-chip devices. Underfilling those components is becoming more and more of a problem. If you have a high residue left behind, even though the material might be a no-clean, if you have a high residue left behind, the flow of material under the chip can be blocked. An ultra-low residue material leaves very little residue behind – can actually allow the easy flow of the materials without voiding in the underfill that may commonly be seen. It really is a game changer.

 

Phil Zarrow: Yes, it really is. It's a real positive impact on the manufacturing process. It's good to hear. Why purchase materials from Indium Corporation?

 

Andy C. Mackie, PhD, MSc: You and I were talking earlier about the fact that two of our independent device manufacturer customers in the USA have qualified our no-clean, ultra-low residue flip-chip fluxes, particularly the NC26A and the NC699, both of those fluxes which have extremely low residues. In the case of the 26A, that's a material that has about 4% or so of residue. The 699 has less than 1% of residue. Both of those materials are industry-leading materials. You don't see our competition able to beat us in terms of our technology.

 

It's not just about the flux residue, it's about the functionality of the material. Is it jettable? Is it dipable? Do you have a longevity of the material? Are you able to pass electrical testing? Finally, are you able to prove that you have compatibility between the residue and the underfill material? We're talking mostly about molded underfills, some capillary underfills as well. Molded underfills typically are very difficult to have compatibility with because they tend to be applied using a hot pressurized process in that very high temperature seems to decrease the compatibility with any flux residues left behind. We have now customer data that proves compatibility with the flux residues that are left after reflow.

 

Phil Zarrow: Very good. Where can we find more information about your work in this area as well as Indium's work?

 

Andy C. Mackie, PhD, MSc: www.indium.com, of course, should be everybody's first step. Very easy to find, and about once a week or so we're putting up new information, new blog posts, new product data sheets. Frankly, we're releasing new materials, I wouldn't say quite on a weekly basis, but, about on a monthly basis we have new materials coming out. For people who want to get in contact with me I can be reached at amackie@indium.com, very easy to find.

 

Phil Zarrow: Very interesting Andy. Thank you very, very much.

 

Andy C. Mackie, PhD, MSc: Phil, thank you very much. My pleasure.