Process Toolkit - Brazing, Welding & Soldering

Brazing	Automatic brazing can be performed with a variety of heating sources - flame, induction, oven or resistance. The process used depends on the parts to be joined. Braze filler can be delivered as a paste, pre-form or as a wire. Automation can be used to assemble and prepare the assembly for brazing, or it can be used in a complete system with an integral brazing station. Typically, integral brazing works best with small to medium sized parts which can be processed on a rotary indexing table.
Contact Soldering (Iron)	Contact soldering with an iron is one possible approach to automatic soldering. The technology is well understood, and simple to deploy. However, achieving zero defects with contact automatic soldering can be problematic. To work well, the solder tip must be wetted with soldering during the process to conduct heat to the joint. This leads to degradation and contamination of the tip. Normally, with a manual operator, the variation in the process can be absorbed by varying the soldering time. However, with automatic soldering, this is not the case. There is no feedback loop to cause changes in the process. Wiping the soldering tip can help, but generally one must overwhelm the joint with soldering and heat to achieve reasonable quality. When precision soldering of delicate joints is required, this is often not a viable solution.
Laser Soldering	Laser soldering is an effective non-contact soldering method that will work with a variety of solder delivery systems including wire, preforms and screened paste. Small diode lasers are available which can provide the necessary beam geometry and power in an package suitable for industrial applications. Several systems for printed circuit board assembly are readily available. Custom system can be integrated from off-the-shelf equipment that has been optimized for the soldering process. Laser soldering is quick, repeatable and accurate.
Laser Welding	Laser welding is commonly used for precision welding of small parts. The process is fast, exact, precise and compatible with inert environments. The time required to complete a weld and the depth of the weld can be configured by the selection of laser technology and power. Laser technology is not inexpensive, but it is unrivaled for precision and capability. Many applications can be serviced by off-the-shelf laser stations. However, integrating a laser process into a larger assembly line requireds expert knowledge to create a safe, secure and effective installation.
Light Soldering	An attractive alternative to laser soldering is soldering by concentrated light. The Panasonic Softbeam delivers concentrated light for point soldering applications. Panasonic offers a variety of systems for printed circuit-board assembly. A modular unit is available for custom applications. The softbeam works in reflowing operations or with a wire feed. The system has very good repeatability, and is suitable for most small point soldering applications.
Resistance Soldering	In resistance soldering, current is passed between the pieces to be joined through soldering, raising the joint temperature. Resistance soldering can be used for reflow soldering or point soldering. Resistance soldering is attractive because the electrodes work best without wetting with solder. This can reduce the need to clean the electrodes as part of an automatic process.
Resistance Spot Welding	In resistance spot welding, current is used to locally melt to components to form a weld joint. Current is typically applied through electrodes, which are pressed into contact with the components to create a current loop. Resistance spot welding is effective at many scales, from microjoining to large scale welding. It also works with many metals provided that the component design allows for good contact pressure across the joint.

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