Light attenuation of white LED lamps (4)

Packaging technique:

In the process of package, every step may cause an effect on the performance of LED street light chips. In which bonders and bonding wires (empty solders) are most likely to raise resistances and thermal resistances. If bonders are too tick, or with air bubble, impurities, virtual sticky in them, the resistance and heat resistance also will be increased. However, since the degeneration of fluorescent powder is too obvious. The influence from this kind of packaging defects can be ignored.

 

In the process of package, every step may cause an effect on the performance of LED chips. In which bonders and bonding wires (empty solders) are most likely to raise resistances and thermal resistances.

 

Light attenuation caused by misuses:

  1. Improper power suppliers. This situation may happen when users are not familiar with electric parameters of white LED lamps. Improper power suppliers will cause LED chips working outside the ASO, and consequently light attenuation. Surrounding temperature is measured when LED chips are working in stable conditions. For example, a piece of LED high bay lamp has been installed in the middle of a room, wait until it is in the stable condition, measure the internal temperature of the lamp (near LED chips) rather than the room temperature. If the surrounding temperature exceeds a threshold, lamp will be degenerated or even damaged.
  2. Insufficient cooling methods: the radiation of heat requires enough area for contact surfaces. Some people prefer to add copper blocks on PCBs or aluminum plates, which is meaningless. It cannot solve the heat problem but raise the cost and heavy of products. Most heat generated by PCBs or aluminum plates will be gathered in these copper blocks. When they reach the peak of their thermal capacity, no more heat will be absorbed. Using thermal capacities of materials to help radiate heat cannot solve this problem thoroughly. It can only cool the device for a short time. Designers should not choose auxiliary cooling materials according to their thermal capacities but their specific heat capacities. Water has powerful specific heat capacities, which is widely used cooling materials. The specific heat capacity is only half of aluminum. However, neither copper blocks nor aluminum blocks are unsuitable for white LED lamps. The best way is natural cooling. Natural cooling relies on the area of radiators’ surface not the volume. If these heat generated by white LED lamps can be radiated in time, the light attenuation phenomenon will be slowed down effectively.