Wave soldering is to make the welding surface of the plug-in board directly contact with the high temperature liquid tin to achieve the purpose of welding. Its high temperature liquid tin keeps an inclined plane, and the liquid tin forms a similar wave phenomenon by special devices. So it's called wave soldering, and the main material is solder bar.
Brief introduction of development
Wave soldering refers to the solder melting (Pb Sn alloy), the electric pump or the electromagnetic pump jet into the solder wave design requirements, can also be formed by injecting nitrogen into the solder pool, the printed circuit board with components through pre solder wave components, welding end or pin soldering printed and mechanical and electrical the connection between the board.
Wave soldering process: insert components into the corresponding element holes, precoating the flux, preheating (temperature 90-100 degrees, length 1-1.2m) to wave soldering (220-240 degrees) cooling, removing redundant plug feet to check.
The reflow soldering process is the paste soldering solders that are pre allocated to the PCB pad by remelting, and the soldering of mechanical and electrical connections between the solder joints of the surface mounting components and the PCB pads is realized.
With the enhancement of people's awareness of environmental protection, the wave soldering has a new welding process. Before the use of tin lead alloy, but lead is heavy metal harm to the human body. Thus, the lead free process was promoted, using the Sn, silver, copper alloy * and special flux, and the higher preheating temperature was required for the welding temperature.
In most of the products that do not need miniaturization and high-power, TH or hybrid technology boards are still being used, such as televisions, home audio and video equipment, and digital set-top boxes. Perforating components are still being used, so wave soldering is needed. From a technical point of view, the wave soldering machine can provide only a little of the most basic adjustment of the operating parameters of the equipment.
Process of wave soldering
After the circuit board enters the wave soldering machine through the conveyor belt, it will pass through a certain form of flux coating device, where the flux is coated on the PCB by means of wave crest, foaming or spraying. Because most of the flux must be kept and activated at an activation temperature to ensure the full wetting of the solder joints, the PCB must pass through a preheating zone before entering the crest trough. The preheating after coating flux can gradually increase the temperature of PCB and activate the flux. This process can also reduce the thermal shock produced by group members entering the crest. It can also be used to evaporate moisture absorption may all carrier solvent or dilution of flux, if these things are not removed, they will be in the wave crest when boiling and cause solder sputtering, or produce steam in solder pad or blisters formed inside the hollow. In addition, due to the larger heat capacity of the double plate and multi laminate, they need higher preheating temperature than the single panel.
At present, the wave soldering machine is basically preheated by thermal radiation. The most commonly used preheating methods for wave soldering are forced hot air convection, electric heating plate convection, heating rod heating and infrared heating. In these methods, forced air convection is usually considered to be the most effective method of heat transfer in most process wave soldering machines. In the warm-up, circuit board using single wavelength (lambda wave) or double waves (disturbance waves and lambda wave) for welding. For perforated components, the single wave is enough. When the circuit board enters the crest, the direction of soldering flow is opposite to the direction of the plate, and eddy current can be generated around the component pin. This is like a kind of brush that removes all the welding flux and oxide film on the surface, forming infiltration at the penetration temperature of the solder joint.
The general assembly for hybrid technology, is used in a disturbing wave front. This wave is relatively narrow, and has high vertical pressure when it is disturbed, so that solders can penetrate well into the compact pins and the surface mounting elements (SMD) pad, and then use the lambda wave to finish the solder joint forming. Before evaluating any future equipment and suppliers, all technical specifications of plates that are soldering with wave crest should be determined, which can determine the performance of the required machines.