PCB manufacturer reflow soldering machine heating system
The full hot air and infrared heating used by PCB manufacturers are currently the two most widely used reflow heating methods, which will be highlighted introduced in this section.
The heating system of the PCB manufacturer‘s full hot air reflow soldering machine is mainly composed of hot air motor, heating tube, thermocouple, solid state relay SSR, temperature control module etc.
The PCB manufacturer’s reflow soldering furnace is divided into a number of independently temperature controlled zones, each of which is divided into upper and lower temperature zones. The temperature zone is provided with a heating pipe, and the hot air motor drives the wind wheel to rotate, and the formed hot air passes through the air passage of the special structure and is blown out through the rectifying board, so that the hot air is evenly distributed in the temperature zone.
Generally, there is an opening at the periphery of the rectifying board as an air inlet, and small opening is distributed in the middle of the rectifying board as an air outlet, hot air is blown out from the middle air outlet to ensure that the temperature is not easily combined between adjacent temperature zones.
The temperature control of the heating system of the PCB manufacturer is mainly achieved by adjusting the heating time of the heating wire. Heating system control process:
Thermocouple → Temperature Control Module → Solid State Relay SSR → Heating Components
Each temperature zone has thermocouple. The PCB manufacturer installs it at the tuyere of the rectifier board, detecting the temperature in the temperature zone, and transmits the signal to the temperature control module in the control system. After receiving the signal, the temperature control module performs the real-time operation. The data is processed to determine whether the output signal of the output end is output to the solid state relay.
If the solid state relay SSR control signal end A2 receives the output signal of the temperature control module, its switching end L1, T1 are turned on, and the heating components are controlled to heat the temperature zone; if the solid state relay SSR control signal terminal A2 does not receive the output signal of the temperature control module, the switching end L1, T1 are not conducting, and the heating components does not heat the temperature zone.
For example, when the detection temperature of the thermocouple is lower than the setting value, the temperature control module will control the heating component to heat the temperature zone through the solid state relay; otherwise, the heating is stopped.
In addition, the speed of the hot air motor of the furnace will directly change the hot air flow rate per unit area. Therefore, the fan speed is also an important factor affecting the temperature in the temperature zone. In hot air reflow, the increasing in wind speed will enhance the heat conduction capability of the furnace and increase the temperature in the temperature zone, but the stronger wind speed will also cause the position of small components to shift and fall inside the furnace. Therefore, to achieve the desired temperature control state, PCB manufacturers must also reasonably set the motor fan speed.
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