Use the DC power supply to adjust the non-lighting LED light to 3V for testing or use a 3 volt button battery to connect the positive and negative electrodes to the LED. If the LED light can light up at this time, but the LED light changes from bright to off as the lead temperature decreases , This proves that the LED light is a virtual solder. The reason why the heating can light up is the use of the principle of metal thermal expansion and contraction. When the LED lead is heated, the expansion and extension is connected to the internal solder joint. At this time, the power is turned on, the LED can normally emit light, and the LED lead shrinks as the temperature drops. After returning to normal temperature and disconnecting from the internal solder joints, the LED light will no longer light up. This method is effective after repeated attempts.

Weld the two lead wires of the dead lamp with this kind of virtual welding on a metal strip, soak it with concentrated sulfuric acid to dissolve the external colloid of the LED. After all the colloid is dissolved, take it out. Observe the welding condition of each solder joint under a magnifying glass or a microscope. You can find out whether the problem is the first or second welding, whether the parameter setting of the gold wire ball welding machine is incorrect, or other reasons, so as to improve the method and process to prevent the phenomenon of false welding from happening again.

Users who use LED products will also encounter the phenomenon of dead lights. This is the phenomenon of dead lights after LED products have been used for a period of time. There are two reasons for dead lights. Open dead lights are due to poor welding quality or the quality of bracket plating. If there is a problem, the increase of the leakage current of the LED chip will also cause the LED light to not light up. Nowadays, many LED products do not have anti-static protection in order to reduce the cost, so it is easy to damage the chip by induced static electricity. Lightning on rainy days is prone to high-voltage static electricity induced by the power supply line, as well as spikes superimposed on the power supply line, which will cause different degrees of damage to the LED products.