Bond assembly can be done via 1) mechanical attachment, 2) adhesive bonding of which epoxy bonding is one form of adhesive, 3) soldering bonding using lower melting filler metals (< 450˚C), 4) brazing using filler metals melting above 450˚C, and 5) welding such as resistance welding bonding, ultrasonic welding and friction weld bonding that uses locally melted parent metal.
Bonding is done for a variety of technical reasons a) mechanical attachment, b) thermal contact, c) electrical contact d) gas or liquid seal, or e) any or all combinations thereof. The choice of bonding method will then depend on the intrinsic properties of the bonding filler materials ( i.e. hermetic, electrical conductance, thermal conductance, thermal coefficient of expansion, adhesive bond strength related to the intrinsic fillers’ mechanical properties, and their adhesive and cohesive strengths). Read more about Epoxy Bond vs. Solder Bond Applications →
Metal to metal bonding is used in many applications for fabricating components where the metallic parts are too large or too complex to make from one piece of metal or the assembly contains dissimilar metals for various functions, such as: 1) physical properties such as electrical or thermal conductivity, 2) differences in thermal coefficient of expansion, 3) differences in corrosion, 4) differences in strength and/or modulus. For designers to utilize the optimum combination of metal properties, it is useful to have metal to metal bonding properties that optimally combine metals in an assembly.
Bonding technologies include: 1)Mechanical fastening, 2) Epoxy bond, 3) other Metal Adhesives, 4) Diffusion Bonding, 5) Explosive Bonding, 6) Weld & Weld Cladding, 7) Ultrasonic Welding, 8) Brazing and Soldering and 9) specialized active solder bonding. For strength mechanical fastening and welding are favored… for low cost, epoxy and other adhesive metal bonding are best but have limitations with regard to sealing, thermal conductivity, and stability over time. Diffusion and explosive bonding perhaps provides the best strength and interfaces between metals. However; for the best combination of bond properties and the least effect on base metal properties; ultrasonic welding, brazing, or soldering are the processes of choice. The choice of bonding process also entails the area of bond required, the joints’ physical properties and the effect the bonding process has on the base metal properties… all these are considerations when selecting bonding process. Read more about Metal to Metal Bonding →
Thermal interface materials are materials used in creating heat conductive paths at interfaces between components and thus reduce thermal interface resistance. These materials permit more effective heat flow between separate components where heat is being generated to a heat dissipation components such as solid state transistors to heat sink or a high frequency device connected to a heat spreader. Thermal interface materials’ purpose is to fill the air gap that occurs at contact interfaces with more thermally conductive compounds to permit more effective heat flow than poorly conductive air.
S-Bond has demonstrated the assembly (stringing) of photovoltaic (PV) solar panels bonding aluminum or copper buss bars using their active solders (S-Bond) in combination with thermosonic bonding. Thermosonic bonding is the simultaneous application of ultrasonic agitation, pressure and heat, normally applied using commercially available ultrasonic soldering irons.
Commercial polycrystalline silicon photovoltaic (PV) cells currently utilize an aluminum powder applied metallization as the current collector for the electrons released by the incident solar energy collects at the aluminized surfaces. Commercial PV cells then require that a conductor strip be bonded to the aluminized cell back in order to transmit the electrons (current) from the cell to the adjacent cells that make up a solar power module in a solar panel assembly. The challenge has been electrically bonding to the aluminized (or otherwise coated) PV materials. Many times silver paint / plated pads has been applied to the coated PV cell followed by conventional flux soldering of pre-tinned thin copper strip to the silver pad
The S-Bond active solder process eliminates the need for pre-coating of silver (lowering cost) to the coated cell surfaces and eliminates the need to use flux (lowering cleaning costs while improving the working environment with no flux off gases). The figures below show how thermosonic bonding of S-Bond coated copper (or even aluminum) buss strip can be used to “string” PV cells together into solar panel modules. S-Bond can provide S-Bond alloys tinned with Copper (or aluminum) buss using an ultrasonic solder pot as illustrated below. For aluminum powder metallized PV cells, the ultrasonic tip is used to “burnish” and densify the areas for buss strip attachment. This treatments makes a dense well adhered, directly S-Bond solderable surface. Using a heated ultrasonically activated soldering tip, the tip can be robotically manipulated to press heat and activate the S-Bond solder in order to locally reheat, reflow and mechanically disrupt the local oxides on the melting solders such that a metallurgical bond is made direct to the coated PV surfaces.
S-Bond has demonstrated this same thermosonic method for bonding to a range of different coated PV materials including Mo coated CIGS and even bonding ceramics to the back of concentrated solar PC cells (CPV’s). Contact us and see how S-Bond thermosonic boding might be used in your solar panel manufacturing processes. To see how robotics and thermosonic bonding can be integrated with robotics take a look at https://www.japanunix.com/en/products/unit/unit_ultra_sonic.php.
Please Contact Us to inquire how S-Bond active solders and thermosonic bonding may be used in the manufacture your solar modules.
Think of the smartphone you hold in your hand, or of your tablet or laptop. The amount of processing power they contain dwarfs offerings from just a few years ago. Theoretically, the parts should be much hotter from doing so many more operations. They are not and one of the biggest reasons why is aluminum soldering and aluminum bonding applications.
Basics of Thermal Management in Manufacturing
Many of the advancements for electronics manufacturing, and other industries that benefit from aluminum soldering, revolve around miniaturization. Parts are smaller, which in some cases mean they are more fragile. In the case of solid-state lighting and LEDs, the advancement in efficiency comes at a price as well: the area of the product where the light is created can hit high temperatures of up to 150 degrees Celsius at the absolute maximum, according to Cree LED data sheets. Read more about Aluminum Bonding and Heat Management in Manufacturing →