Brazed fin heat sinks

What is brazing?

Brazing is the process of melting a metal between two other pieces of metal in order to join them. Common metals for this process in the thermal management world include copper and copper based alloys, aluminum-silicon based alloys and nickel alloys. This process allows us to create brazed fin heat sinks , liquid cold plates, heat exchangers and chassis, which expands our thermal management technology toolbox.

Brazing, if applied well, can generate tight joints since the process relies on capillary action wicking the braze material between the parts. Braze material is an alloy that melts at a temperature lower than the parts you’re joining together. Stronger and more consistent joints are made with materials that closely match the mating parts. In all brazing processes, mating parts are fixtured together to ensure they retain their geometric relationship to each other during the brazing process. Once parts cool, they’re either ready or need finishing like residual flux removal, straightening or machining.

What’s the difference between brazing and soldering?

Brazing is a similar process as soldering, just at a much higher temperature (above 450°C or 840°F). The higher temperature enables a bigger material selection, which includes aluminum. Both soldering and brazing use a filler material, like a solder, to join the metal pieces together. If the metals and atmosphere require it, flux is also added to the mix to prevent oxidation of the joint.

Brazed fin vs bonded fin heat sinks

Different types of brazing

While they’re many types of brazing, we’ll go over the common ones used in thermal management.

Controlled atmosphere brazing

Vacuum brazing

As the name suggests, vacuum brazing is conducted in a vacuum chamber. This removes oxygen which can oxidize the braze joints or other gasses that could get caught in tiny pockets in the joints. In practice, vacuum brazing has an advantage over other types of brazing since it doesn’t require flux to prevent oxidation. That makes vacuum brazing popular for complex assemblies like heat exchangers and liquid cold plates, since residual flux is tough to remove from tight, enclosed spaces.

Torch brazing

In a few occasions, we’ll use torch brazing to make tricky prototypes, proofs of concept or complex, small production runs. Torch brazing utilizes a gas flame to melt the filler material between the two metal parts being joined. Since this typically is a manual process, it’s reserved for small quantities. Since we’re not using a tightly controlled atmosphere that aluminum brazing requires, this process is normally reserved for copper and nickel alloy brazing.

All in all

Brazing gives us a whole bunch of options when it comes to constructing high quality or high complexity thermal management products.

Are you looking help designing or manufacturing a brazed assembly? We can help with either your brazed heat sinks, heat exchangers or liquid cold plates. Contact us today for assistance!