S-Bond Joining of SiC Tiles in Microwave Beam Dampers (Absorbers)

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

Contact us to see how S-Bond joining can solve your ceramic to metal bonding challenges.

S-Bond® Solders At the Interface of the NanoBond® Process

Figure 1. Illustration of the NanoBond® / NanoFoil® heating process® (from www.indiumcorp.com)

Figure 1. Illustration of the NanoBond® / NanoFoil® heating process® (from www.indiumcorp.com)

S-Bond active solder layers have been shown in many applications to be the key ingredient that permits many ceramics and refractory metals to be bonded to largely coefficient of thermal expansion (CTE) mismatched metals such as aluminum and copper. Indium Corporation offers a NanoBond® process that uses NanoFoil ® as local heat source to remelt preplaced solder layers without the need for the bulk heating of assembled components that have large CTE mismatch. Active S-Bond solders are applied as prelayers and have Ti, Ce, Ga and Mg additions that permit them to wet any ceramic or metal surface. Once the S-Bond pre-layers are applied to ceramic and/or metallic surfaces, conventional solders can be reflowed onto the S-Bond layer to create the preplaced solder layers that are remelted and bonded via the heat emitted from an ignited NanoFoil®. Figure 1 illustrates how temperatures of over 1,400 K are generated by an ignited nano-engineered foil. Read more about S-Bond® Solders At the Interface of the NanoBond® Process

S-Bond Joining of High Brightness LEDs

S-Bond active solder joining is emerging as an effective method to bond heat sinks to the back of High Brightness Light Emitting Diodes (HBLEDs). Active solders can wet and adhere to many of the thermally conductive ceramics (AlN, BeO, etc.) that are being used in HBLED’s and enable effective and thermally stable and conductive joints. Read more about S-Bond Joining of High Brightness LEDs

Soldering Silicon Carbide (SiC) for Electronics and Optics

Figure 1. Steel fitting S-Bond joined to SIC

Figure 1. Steel fitting S-Bond joined to SIC

S-Bond active soldering of silicon carbide (SiC) has recently been demonstrated on a range of electronic and optical components, providing for metal to SiC joints in plug, mounting and/or water cooling fittings. Silicon carbide is ceramic semiconductor with good thermal conductivity (120 W/mK) and low thermal expansion ( 4 ppm / °C). Thermal conductivity is comparable to aluminum with 1/8 of aluminum’s thermal expansion coefficient (CTE), making it a very stable material. The manufacture techniques for SiC and Si:SiC have recently developed to permit more complex SiC based components. As a ceramic, SiC is very difficult to machine so normally powder sintering and infiltration and/or slip casting and sintering followed by infiltration is used making for making complex shapes. Because of its thermal, electrical and optical properties, SiC and SiC composites are seeing increased industrial application in electronics and optics thus driving an interest for robust SiC joining methods. For high temperature SiC applications vacuum active brazing has proven effective; however, for lower temperature electronic and optical applications, there has been interest in solder joining methods. Read more about Soldering Silicon Carbide (SiC) for Electronics and Optics

Ceramic to Metal Bonding

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. Read more about Ceramic to Metal Bonding