The soldering furnace is the heart of the whole soldering machine. It contains a tin bath, a tin pump, and a tin spray port. The solder furnace is usually immersed in tin. The tin furnace is made of stainless steel, and the U-shaped heating wire The bottom and both sides of the tin furnace are used to melt tin and maintain the temperature of the tin. The upper heating wire is used for melting tin and the lower heating wire is used for constant temperature control.
The solder bath is a container that must be able to withstand the temperature of the solder. Typical solder used in the electronics industry is full of gold; its operating temperature is within 260 degrees, its structure must be able to withstand the weight without deformation, and the material is resistant to corrosion. Cast iron or stainless steel is generally used. .
1, the solder furnace heating is divided into three categories:
1) External heating method;
2) internal heating method (called cassette heater);
3) The immersed heater is directly immersed in the tin bath to contact the solder.
Tin tank capacity should take into account solder contamination, thermal stability, and tin wave surface stability. The ratio of the degree of contamination of the solder must be inversely proportional to the amount of the solder, and the thermal stability of the tin wave is affected by the size of the solder bath.
2, solder automatic replenishment device
Can be installed in the soldering machine visual tin indicator, or when the molten tin surface reaches the upper and lower limits, the signal display. An ordinary method for measuring the molten tin surface is to use a float made of stainless steel, operate the switch and warning lamp with the height of the tin surface, or start an automatic tinning mechanism.
3, solder pump
A tin pump can be generated by driving a simple exhaust pump with a motor. The molten solder is pressurized and flows through the nozzle. The height of the tin wave is usually controlled in three ways: First, to change the speed of the tin pump; First, the high and low position of the tin pump; or to combine the two methods.
4, solder wave
The two main problems caused by tin wave are the excessive amount of solder in the solder joints and the short circuit, tin spikes, etc. This is because the excess solder has not been dropped back into the tin wave; the other is that the solder effect is not ideal, such as the through hole on the top of the substrate. The phenomenon that the surface is not filled with solder and the solder is not clean is because the tin wave fails to transmit enough heat to the solder joint. This can be solved by slowing down the solder speed. The following problems are solved:
1) The use of oil in the tin wave reduces the surface tension and allows the excess solder on the substrate to flow back into the tin wave.
2) Increase the contact surface between the tin wave and the substrate, so that the solder joint has more heating time.
3) The use of natural gravity and surface tension allows excess solder to be easily reflowed into the tin wave, even if the substrate contacts and decouples from the tin wave at an angle of 5° to 8°.
According to the type of spray nozzle tin waves are divided into:
1) Symmetrical tin-wave; is the earliest kind of tin wave, and it is easy to produce short circuit and tin tip with the horizontal type conveying mechanism.
2) Wide Symmetrical Tin Wave: Increases the tin wave plane and improves solder speed.
3) Adjustable symmetric tin-wave: Suitable for any special purpose, can be used for welding large heat-dissipation area substrates, and for simple substrates, it can be quickly welded.
4) Asymmetrical tin wave: It is formed by adding an extension plate on the side of the spray nozzle, and the contact surface between the outlet end and the substrate has been greatly improved.
5) Adjustable asymmetrical tin wave:
Usually with 5°~8° tilted conveying mechanism, most of the dissolved tin flowing out of the soldering tin flows in the opposite direction to the substrate, and a small amount of tin is flowing in the same direction as the substrate travels. The middle and back halves form an almost stationary wave surface, which has a very significant effect in the soldering process of ultra-dense circuit boards, properly meeting the correct process variable settings, and can achieve the highest quality and nearly zero defects solder joint requirements. .
If the tin stove used is a double tin wave, he consists of two parts. The first is a narrow and spoiled tin wave, which is easy to penetrate and cover all corners of the substrate's solder surface. The second part is a standard one. Symmetrical tin waves are used to flatten the solder joints that have been soldered and to rework excess solder back into the tin wave, which is suitable for substrates with extremely dense wafer circuit traces.
1) Bubble Tin Wave: Designed for substrate components with wafer components.
2) Oscillation Tin Wave: Another kind of tin wave that develops for the problem of soldering of wafer parts. The advantage is that it does not need to use double tin waves, no disturbing current wave, and reduces the opportunity for molten tin to overflow to the substrate part surface.
How to choose the right tin wave: The most reliable method is to take the substrate to the actual soldering machine for actual test welding.