Indium Blog

Semiconductor Fluxes: Part 1

  • Semiconductor Packaging

  • A lot of people who are not familiar with semiconductor products find them intimidating. I was one of those who found them daunting, but now I realize that semiconductor fluxes should not be “scary”. In fact, as an engineer, they can be a great resource to keep in your back pocket.

    Some of the semiconductor fluxes that we offer include flip-chip fluxes, wafer bumping fluxes, and ball attach fluxes.

    I’ll start out by talking about flip-chip fluxes for a bit. Flip-chip flux is typically a low to medium viscosity flux. It is applied to the “flipped” die by dipping it in flux, hence the name flip-chip flux. These fluxes can be water-soluble or no-clean and help to remove oxides during the reflow process from the solder bumps or the Cu pillar micro-bumps.

    Cu pillars topped with solder micro-bumps are becoming more and more popular. However, as these devices become smaller and more fine-pitch the package becomes more prone to warpage during the reflow process. This, in conjunction with wetting of the surface and the amount of oxidation on the surface, can make flip-chip assembly challenging. To address all these new challenges, you need a proper flux that can wet the surface, clean the oxides, and still keep the flip-chip in place during reflow. This is where the rheology, as well as the chemistry, plays a critical role. Indium Corporation has devoted significant resources to fully understand the rheology and chemistry of our fluxes so we can recommend just the right flux for your application – whether you need a water-soluble, no-clean or even an ultra-low residue flux.

    Let us know how we can help you. You can reach out to me or anyone in the Technical Support Team by emailing