Aluminum Bonding

Aluminum structures are normally brazed, welded or soldered. Braze joining of aluminum uses Si-rich Al alloys that have brazing temperatures ~ 25 - 50 ºC below the melting points of the base aluminum. Additionally, to disrupt the aluminum oxides that form naturally on aluminum, aggressive chemical fluxes and/or vacuum furnaces must be used for bonding aluminum. As such, aluminum brazing in furnaces requires precise controls and atmospheres. After brazing, the high processing temperature considerably softens and lowers the base aluminum strength.

Alternative to Brazing

S-Bond can be an alternative lower temperature joining process and replace brazing in some applications. S-Bond is very effective in soldering aluminum to aluminum as well as soldering aluminum to copper. In many cases, “dip brazing” is also used in joining aluminum. Dip brazing uses similar Si-rich aluminum filler metals and pre-places performs or aluminum pastes with chemical fluxes into a salt bath that heats the aluminum components which have been fixtured to hold the part positions in the bath. As in furnace brazing, the high temperatures of the brazing process soften the base aluminum and the parts must be rinsed of the flux and salt that comes from the bath exposure. Due to the aggressiveness of the chemicals and salts, work environment and waste disposal issues are now limiting available dip brazing sources.

Aluminum Bonding

Aluminum can be conventionally soldered or  joined using active S-Bond® alloys. Conventional soldering to aluminum normally requires initially plating the aluminum to cover the aluminum oxide surface, or the use of aggressive fluxes or mechanical techniques (heavy scrubbing or ultrasonics) to break through the natural surface oxide film and allow bonding.

Active S-Bond® solders easily react with and break through the oxide layers on aluminum and copper to react quickly and irreversibly with the metal without the use of plating or fluxes, thus lowering the cost of solder joining aluminum and also eliminating aggressive chemicals that create environmental hazards. Additionally, S-Bond’s low joining process temperature (typically below 250ºC) preserves the hardness and strength of the base aluminum making the finished component more robust.

S-Bond aluminum bonding may be an excellent substitute to your current aluminum joining processes. Cycle times may be reduced and, especially with thermally sensitive applications or low piece lots, the limited tooling and ease of set up for S-Bond joining can significantly reduce costs.

There are a range of S-Bond alloys available with different service temperatures from 100°C to 390°C. These same products also join well to copper, aluminum silicon carbide, and other thermal management materials and allow cost effective, fluxless assembly of complete thermal management systems.

Please Contact Us for assistance with your aluminum bonding application or consult our Products section.