Aluminum soldering is used in making small area electrical and/or thermal connections or seals to other metal or ceramics, while aluminum bonding is used to join large areas either for thermal and/or structural purposes. Aluminum soldering finds applications in sensors, electronics, and electrical power where aluminum contact and/or wire leads are being utilized. Aluminum soldering has also been used as a means to seal and/or repair aluminum heat exchangers.
We have been contacted many times for assistance in solving the problem of small contact to aluminum without the use of aggressive chemical flux or cases where the chemical flux for aluminum was not compatible with the metals of the opposing side of the joint. Additionally, in many electronic packages the use of corrosive aluminum soldering fluxed are limiting When faced with these choices, active fluxless solders such as S-Bond become a good solution. (more…)
While it has been several years since manufacturers began moving to lead-free solder procedures, in part due to the European Union’s Restriction of Hazardous Substances Directive, some still believe myths that have long been inaccurate regarding the use of alloy joining materials that do not require flux and are based on lead and tin.
Temperatures Can Be Enough to Destroy Components
The first round of lead-free solder options to join metals and other materials were comprised of tin, silver and copper, which do have a slightly higher melting point of 217 degrees Celsius compared to existing solder’s 183 degrees Celsius. That disparity could cause problems regarding PC board damage.
However, newer products including several offered by S-Bond have significantly lower melting points that make it easier to join metals like aluminum. At the lowest temperatures, some materials can be joined at just 115 degrees Celsius.
Issues Regarding Silicon Will Require Other Materials
Argonne National Laboratories selected S-Bond active solder technology to make water cooled high power microwave beam dump in its Advanced Photon Source which is a user-facility to producing extremely brilliant x-ray photon beams. The Advanced Photon Source uses high energy microwave beams to steer and create such x-ray photon beams. These beams once started cannot be shut down or restarted easily, so to facilitate the use the various beam lines, the microwave beams are diverted to beam dumps. These beam dumps consist of microwave cavities that are lined with SiC tiles bonded to water cooled rectangular copper enclosures that are heavy water cooled. SiC is a well know high efficiency absorber of microwave energy and thus is used in dampers.
The challenge faced by the Argonne engineers and physicists was to find a stable process for bonding the SiC tiles to copper bases that would provide thermal and electrically conductive interface and be able to take the thermal expansion mismatch during the bonding processes and in service. Active brazing and active soldering were considered since active brazes and solders are able to form metallurgical bonds with the SiC tiles. Active brazing, using Cu-Ag-Ti was tested and it was found the residual stresses stemming from the coefficient of thermal expansion (CTE) mismatch of SiC and copper led to the fracture of the SiC tiles upon cooling from the 860˚C brazing temperature to room temperature. S-Bond active soldering was selected as good alternative to active brazing since the solder bonding temperature of 250˚C yielded much lower CTE derived stresses and created a more compliant bond line that would better accommodate the heating and cooling stresses in service.
Figure 1 below show the S-Bond joined SiC tiles being bonded into one half of the microwave beam damper cavity indicating how S-Bond successfully joins SiC to copper. Figure 2 is an ultrasonic C-Scan of the bonded interfaces under each tile in the damper half
The direct solder joining of silicon is difficult posing solder wetting and adherence challenges for many applications including electronic “die” packages, sensor chips and solar panels. The direct solder bonding to silicon (Si) has been limited by the wetting resistance of angstrom thick nascent silicon dioxide (SiO2) layers that naturally forms on silicon. To combat these solder bonding challenges, metal plating (vapor deposition of Ti and Ni) has been used. To address this challenge, S-Bond Technologies has developed and has recently been awarded a patent for its S-Bond 220M alloy which is a Sn-Ag-Ti-Ce-Ga + Mg alloy that has been optimized for direct Si solder bonding without flux nor plating. The new alloy bonds well to silicon, silica, and glass silicates based on a solder formulation that adds magnesium (Mg) in low enough levels that does not change the solder melt behavior but enhances the “active” nature of S-Bond alloys to interact with oxides of silicon and many other metals even more effectively than other active solders. These Mg modified active solders wet and adhere very well to silicon based on mechanical activation used in other active solders. (more…)
What is meant by “active solder”? The term evolves from active brazing; I assume that does not really help you…. But it is true that active brazing was the key technology that led to the development of active solders. (more…)
S-Bond® active solder enables the joining of sapphire to metals and provides an alternative to other sealing processes. S-Bond joining of sapphire/metal seals is proving to be a more robust and reworkable joining process while being simpler than many of the existing sapphire widow sealing processes, as this article presents. (more…)
S-Bond® active solders enable graphite bonding and the joining of other carbon or carbide based materials to each other and to most metals within the constraints of thermal expansion mismatch. S-Bond alloys have active elements such as titanium and cerium added to Sn-Ag, Sn-In-Ag, and Sn-Bi alloys to create a solder that can be reacted directly with the carbon surfaces prior to bonding using specialized S-Bond treatments prior to solder joining. Reliable joints have been made between graphite and carbon based materials with all metals including steel, stainless steels, titanium, nickel alloys, copper and aluminum alloys… (more…)
S-Bond® active solders enable ceramic to metal bonding and sapphire to metal bonding as well as to each other. S-Bond alloys have active elements such as titanium and cerium added to Sn-Ag, Sn-In-Ag, and Sn-Bi alloys to create a solder that can be reacted directly with the ceramic and sapphire surfaces prior to bonding. S-Bond alloys produce reliable, hermetic joints with all metals…including steel, stainless steels, titanium, nickel alloys, copper and aluminum alloys. (more…)