Indium Blog

Specifying Solder Preforms – Flux

Flux... It would be great to live in a world where we didn’t need it. Unfortunately, that same oxygen that keeps us alive slowly erodes the solderability of surface finishes on most components, preforms, and circuit boards. At Indium Corporation, we fully embrace flux. Our R&D department works on the most challenging flux projects for customers around the world. What they learn is often used in our main flux offerings.

For most preforms, no-clean flux is applied directly to the solder. We cure the flux so it forms a hard coating on the solder. During reflow this coating liquefies and reacts with the oxides currently inhibiting solder spread and bonding. Once the solder joint is formed, the flux is designed to remain on the solder joint for the life of the product, as a harmless residue.

More info about choosing flux coatings and using flux-coated preforms can be found here: Flux Coated Preforms

In addition we offer LV series flux, which is a next generation coating. (LV = Low-Voiding)

Seth Homer has written about this type of flux and it’s advantages, which include the ability to provide a very uniform, thin, powerful coating which is still classified as halide-free. This was made possible by looking at flux design and application in a completely different way.

When preforms are specified, it is critical for us to know which flux (if any) will be desired, and what weight % of that flux to provide. This is a key component to specifying solder preforms.


*This post is part of the World of Solder Preforms series

Authored by previous Indium Application Manager Jim Hisert