Reasons for high reflow soldering temperature and inability to rise temperature

After the start of reflow soldering, the temperature in the temperature zone loses control, and the temperature continues to rise or does not rise, resulting in unqualified welding product quality. Here, JEENOCE will analyze the reasons for the high reflow soldering temperature alarm and the reasons why the temperature cannot rise:

Reasons for not removing or melting tin at reflow soldering temperature:

1. Check if the reflow soldering hot air motor is rotating. As reflow soldering belongs to hot air conduction, the motor does not transfer heat, resulting in the inability to transfer heat to the product. However, the software interface actually shows normal temperature. This is due to a defect caused by the thermocouple in each temperature zone being close to the heating zone. Even if the hot air motor is not rotating, the temperature can still be displayed as normal. The air heated by the electric heating wire cannot be blown out, the heat cycle process cannot be completed, and the temperature cannot rise. But over time, adjacent temperature zones will overflow towards it and eventually rise, but will slowly fluctuate up and down;

2. Measure whether the electric heating wire is open circuit; After turning off the device power, use a multimeter to measure the resistance value of the heating wire. If there is no resistance value, it may cause the heating wire to burn out and open circuit.

3. Check the control part of the equipment and detect and control the heating. Is there an output from the solid-state relay? If unsure, switch between relays in adjacent temperature zones to determine if the relay is faulty.

4. Check if the solid-state relay in the faulty temperature zone has an AC 220V input. All solid-state relays control the live wire, and check if there is an AC 220V voltage between the input terminal and the N line of the power supply. If the voltage is below 190V or does not display voltage, it is a problem with the front power input. Use the same method to troubleshoot single-stage switches, contactors, air switches, and input power lines until the problem is identified. The solid-state relay will display a red indicator light when outputting, but it cannot rule out that the indicator light is damaged. Using a multimeter can better identify the problem.

5. There is no problem with the heating wire and electrical troubleshooting. If there is a three-phase power outage and phase loss, this situation can also occur. Check if it is an external power supply phase loss.

Reasons for high reflow soldering temperature:

1、 We need to use a multimeter to test whether the solid-state relay is broken down. Breaking down will cause the solid-state relay to be in a normally closed state, which will cause the heating wire to remain in a heating state if it is not controlled.

2、 Check if the reflow soldering hot air motor rotates. If the motor does not transfer, the temperature will be instantly pulled down when passing through the product. At this time, the PLC will control the solid-state relay to keep heating. Because the motor does not rotate, the heat cannot be transmitted to the temperature measurement line, and the heat will be transmitted in a lagging form, causing the temperature in the temperature zone to fluctuate.

3、 PLC controller malfunction and inaccurate temperature control result in continuous output of solid-state relay, uncontrolled temperature rise, requiring replacement of PLC for processing.

Generally, the reflow soldering temperature is too high due to the above three reasons. When operating reflow soldering, it is necessary to be familiar with the working principle of the machine and related parts, and then gradually eliminate them. If confirmed, it can be processed and verified by replacing parts.