What is contact welding

Contact welding is done when the heated tip or ring touches the welding point directly. The soldering tip or ring is mounted on the welding tool. The nozzle is used to heat a single spot, while the ring is used to heat multiple spots simultaneously. There are a variety of design structures for single nozzle welding tool and welding nozzle.
There are also a variety of design structures for the welding nozzle in the form of a soldering iron ring. A discrete ring with two or four sides, mainly used for component removal. The design of the ring is mainly used in multi-pin components, such as integrated circuits; However, they can also be used to disassemble rectangular and cylindrical components. Soldering rings are useful for removing components that have been glued together. After the solder is melted, the soldering ring can be twisted to break the glue connection.
Four-sided components, such as plastic pin chip carriers, create a problem because it is difficult for the soldering iron ring to contact all pins at once. If the soldering ring does not touch all the pins, no heat transfer will occur, which means that some solder joints do not melt. Especially on J-pin elements, all pins may not be on the same reference plane, making it impossible for the soldering ring to touch all pins at the same time. This situation can be disastrous because the pad still soldered to the pin will pull out of the PCB when the operator removes the component.
Welding nozzle and ring require frequent preventive maintenance. They need to be cleaned and sometimes tinned. Frequent replacement may be required, especially when using small soldering tips.
Contact welding systems can be classified from low price to high price, usually limiting or controlling temperature. The choice depends on the application. For example, surface mount applications typically require less heat than through-hole applications.
1, constant temperature system, provides continuous, constant output, continuous transfer of heat. For surface mount applications, these systems should operate in the 335 to 365°C temperature range.
2, limiting temperature system, with temperature limiting ability to help keep the system temperature in an optimal range. These systems transfer heat discontinuously, which prevents overheating, but heating recovery can be slow. This may cause the operator to set a higher temperature than desired, speeding up the welding. The operating temperature range for surface mounting applications is 285~315℃.
3, control temperature system, to provide high output capacity. These systems, like temperature limiting systems, transfer heat discontinuously. Response timing and temperature control are superior to temperature limiting systems. The operating temperature range for surface mounting applications is 285~315℃. These systems also provide a better deviation capacity, usually 10℃.
The characteristics associated with contact welding systems include that, in most cases, contact welding is the easiest and least costly method of repairing welding and component removal and replacement. Adhesive elements can be easily removed with a welding ring. Contact welding equipment is relatively low cost and easy to buy. Problems associated with contact welding systems include: Systems that do not limit the nozzle or ring are prone to temperature shocks that raise the temperature of the nozzle or ring above the desired range. The soldering ring must be in direct contact with the solder points and pins to achieve efficiency. Temperature shocks may damage ceramic components, especially multilayer capacitors.