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 and provide its corrosion resistance, aggressive chemical fluxes and/or vacuum furnaces must be used. As such, aluminum brazing in furnaces require precise controls and atmospheres. After brazing, the high processing temperature considerably softens and lowers the base aluminum strength.
Alternatively, “dip brazing” is 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 aluminum structures that have been fixtured to hold part positions in the bath. As in furnace brazing, the high temperatures of the brazing process softens 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 can be conventionally soldered or solder-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 (normally below 250ºC) preserves the hardness and strength of the base aluminum making the finished component more robust.
S-Bond may be an excellent substitute to your current aluminum bonding or joining processes. S-Bond is very effective in soldering aluminum to aluminum as well as soldering aluminum to copper. 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 Technology & Applications White Papers, our Blog or our Products section.