1. The damage caused by static electricity to the light-emitting diode chip The heat generated by the instant electric field or current causes the light-emitting diode to be locally damaged, which is manifested as a rapid increase in leakage current. Sometimes it can work, but the brightness is reduced or the white light is discolored, and the life is damaged. When the electric field or current breaks down the PN junction of the light-emitting diode, the inside of the light-emitting diode is completely destroyed and the lamp is dead. In the light-emitting diode packaging production line, all equipment is required to be grounded, the general grounding resistance is 4Ω, and the grounding resistance of high-requiring places is ≤2Ω. LED application assembly line equipment and poor grounding of personnel can also cause damage to the LED. According to the standard of the LED user manual, the lead of the LED should be no less than 3～5mm away from the colloid for bending or soldering. However, most application companies cannot do it. They are soldered only with a PCB thickness (≤2mm) Will cause damage to the light-emitting diodes. Excessively high soldering temperature will deteriorate the chip characteristics, reduce the luminous efficiency, and even die. Especially some small companies use a 40W ordinary soldering iron for manual soldering, which cannot control the soldering temperature. The soldering iron temperature is generally 300℃～400℃. The high temperature expansion coefficient of the LED lead is several times higher than the expansion coefficient of about 150℃. The internal gold wire solder joints The solder joints will be pulled apart due to thermal expansion and contraction, resulting in dead lights.
2. The advantages and disadvantages of the open-circuit bracket row in the internal connection line of the light-emitting diode device is the key to the performance of the light-emitting diode. The bracket row is made of copper or iron stamped by precision molds. Because copper is more expensive, cold-rolled low-carbon steel is used to stamp the LED bracket row, and the iron bracket row is silver-plated. Silver plating has two functions: (1) prevent oxidation and rust; (2) facilitate welding. Because the air humidity is high for a period of time every year, it is easy to cause the poorly plated metal parts to rust and cause the light-emitting diode components to fail. The packaged light-emitting diodes will have poor adhesion due to the thin silver plating layer, and the solder joints will detach from the bracket and cause dead lights. In addition, each process of packaging must be strictly operated, and negligence in any link will cause dead lights.
3. Reliability testing and evaluation of high-power light-emitting diodes. The failure modes related to high-power light-emitting diode devices and packaging structures and processes include optical failure (such as yellowing of potting glue, deterioration of optical performance, etc.), electrical failure (such as short circuit and open circuit) and Mechanical failure (such as lead breakage, desoldering, etc.). The average failure time is used to define the service life of a light-emitting diode, which generally refers to the use time of the light-emitting diode's output luminous flux attenuation to 70% of the initial value (usually 50% of the initial value for display screens). Accelerated environmental testing is usually used for reliability testing and evaluation. The test content includes high temperature storage (100℃, 1000h), high temperature and high humidity (85℃/85%, 1000h), low temperature storage (-55℃, 1000h), high Low temperature cycle (85℃～-55℃), thermal shock, solvent resistance, corrosion resistance, mechanical shock, etc.
