Vacuum Brazing

Vacuum brazed assemblies can be found in a wide array of markets and applications. These assemblies can range from oil coolers for automotive applications to highly complex environmental control systems with reduced weights for the aerospace and defense industries. The vacuum brazing process is especially ideal for products where high quality joints, lightweight assemblies and high thermal and mechanical performances are required.

Vacuum Brazing

Vacuum brazing is a manufacturing process for joining components that allows for higher thermal performance and lighter solutions. Braze alloys have a lower melting temperature than the materials that they are joining. Prior to the heating process, the braze alloy is applied between close fitting components of the parent alloy that are fixtured into place. The parts are placed in a vacuum furnace that is heated to at least 450°C, a level that will melt the braze alloy but not the main material. As the furnace is a vacuum environment, there is no risk of oxidation and no need for flux. The molten braze alloy fills in gaps between the components through capillary action so that when the part is cooled, it forms a joint through atomic attraction and diffusion. The end result is a clean, one-piece construction with strong joints.

Depending on application requirements of the part and its complexity, a helium leak check can verify the leak tightness of brazed joints. Parts that require T4 or T6 hardness stage undergo heat treatment after leak tight tests. This enables machining at similar feeds and speeds as those for untreated aluminum. Depending on individual part geometries, additional processes such as straightening may allow more effective ways of machining the finished components when required.

Although it can be limited by fixturing or oven size, vacuum brazing is an extremely versatile and clean process. As such, it tends to be the preferred manufacturing process used to produce lightweight, high performance assemblies with increased internal surface areas. Additionally, vacuum brazing can be used to produce larger assemblies with complex geometries, benefiting from the low distortion introduced by the process itself. These structures can range from plank type assemblies with internal channels to electronic enclosures, with or without internal features such as cold walls.

Aavid specializes in Brazed Heat Exchangers, Liquid Cold Plates, Heat Sinks, Chassis, and Enclosures.

Aavid braze furnaces are certified to braze per AWS C3.7 Class A, B, and C.

 

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Benefits

Vacuum brazing offers significant benefits over other joining technologies:
  • Flux free process leads to clean parts

  • Highly repeatable and controllable batch process

  • Uniform material properties during and after brazing

  • Ability to produce internal joints, even in complex structures, increasing the part’s overall strength

  • High temperature resistance of joints

  • Common braze materials have excellent thermal properties

  • Process enables highly enhanced surface structures to enhance thermal transfer

 

Aluminum Brazing Alloys and Fillers Available

Brazeable Alloys include:
• Wrought Aluminum 6061, 6063, 6082, 6951 (heat treatable) and 1100


• 3000 Series (non heat treatable)


• Cast Alloys A356, A357 and 443, 700 Series (less typical)

 

• 2000 and 7000 Series materials not typically brazed due to alloy limitations


• 5000 Series due to magnesium content

 

Filler Metals

• Silicon, copper, zinc and others added in small quantities to aluminum to lower its melting point


• Magnesium also for vacuum brazing


• Typical Corrosion Resistant Filler Alloys include 4047, 4343 and 4045


• Comes in sheet, wire and powder forms

 

• Clad Brazing Sheet (filler alloy embedded on aluminum surface) also used


• No. 21 through 24 can be used for vacuum brazing