Point Soldering Technology Principle (I)
Point soldering is a kind of soldering technology widely used in electronic industry. Its essence is to make the soldering material melt, fill the contact surface between electronic components and printed circuit boards, and bind them together. The method of making soldering material melt and filling surface of contact points is by applying high temperature heat source with a certain shape, size and dwell time at appropriate position.
Generally speaking, point soldering has the following basic principles:
1.1 Selective soldering
In most electronics manufacturing industries, the size of soldering area usually varies greatly. Selective soldering is a successively linear soldering technology that is suitable for soldering components with large concentration area and relatively large temperature range. This technology uses one or two rows of tips to manually feed or automatically spray soldering wire on the contact surface between the component and the substrate, so as to realize selective soldering and maintain the quality of the product.
1.2 Continuous soldering
Continuous soldering is mainly used for the soldering processing of high-precision and high-density electronics components. Generally, it is used before the insertion process, and it is suitable for soldering of components or groups on both ends of PCB with high solder joint density or poor insertability. The soldering method is mainly based on the generation of heat waves between two rows of soldering heads placed close to each other.
1.3 Reflow soldering
The reflow soldering method requires to spread the solder paste uniformly on the components of the board. Then, the board is sent to the oven, heated by the preheating zone of the oven. The smearing layer of solder paste is melted, the solder on the surface of the component diffusion joint is melt, fill the gap and solidify together. This soldering method is the most tested and used in high-volume production process.
1.4 Spot soldering
Spot-welding is a technology with long history, spot soldering is the same, commonly known as single welding, as its name suggests, spot-welding process is completed by spot energy delivery, mainly used for small components and terminal welding, through spot-welding current make welding material (generally refers to tin or tin and lead alloy) melting, welding into larger parts or components, bonded parts after work in progress, ensure the reliability of welding parts, such as special parts such as insulation and shell, will be further processed.
1.5 Paste soldering
Paste soldering is also a typical soldering technology in PCB assembly. The general paste soldering is to perform wave soldering after printing paste to print circuit board, in order to better control soldering process quality and reduce labor cost, realize automated assembly. The so-called paste soldering is to add solder paste to the pad and component pins of PCB components before PCB mount; After heating the PCB in solder wave or oven, the solder paste is melted to realize the connection of components and PCB substrate.
1.6 Dip soldering
Dip soldering is to put circuit board into solder containing flux in molten solder pot,heat a certain temperature and dwell time in molten solder, then take out and cool to complete the connection of circuit board and component.
1.7 Hot Air soldering
Hot air leveling process is to send hot air on the solder paste coated circuit board, let the pre-coated solder paste melt, flow, cover the pad and components, and the solder paste is cooled and formed a complete interconnection. This process is characterized by fast and efficient, high quality, suitable for some SMD components, lift packages, SOIC, PLCC and BGA, so as to achieve mass production needs.
The above are all the commonly used point soldering technology, of which the most common ones in the electronic industry are selective soldering, continuous soldering, reflow soldering, paste soldering, etc. Point soldering technology is not only used in electronic product assembly and packaging, but also widely used in automotive industry, civil industry, military industry and so on. It is an important technology for industrial automation assembly.
