LED lamp cooling failure analysis - Database & Sql Blog Articles

1. Case background The LED lamp samples show the failure phenomenon shown in Figure 1 during the aging process: a, the surface of the lamp bead is black; b, the encapsulation colloid of the lamp bead is off; c, the lamp encapsulation colloid is black. The customer asks to analyze the cause of the failure and determine if there is a connection between the failures. Fig.1 Lamp failure phenomenon2. Brief description of analysis method The black substance on the surface of the failure phenomenon a is easily erased during the visual inspection. It is found to be inorganic by FTIR test, and the result of further SEM/EDS analysis shows brown. The carbon content of the material is extremely high, and its morphology is very similar to that of the graphite material used for heat dissipation. Therefore, it is judged that it is derived from the heat-dissipating material graphite of the lamp; the structural thermal resistance and the infrared temperature measurement show that the failure phenomenon a does not cause heat dissipation of the lamp. influences.
Figure 2 FTIR test results Composition Conc Units C 96.4 wt.% O 3.6 wt.% Figure 3 SEM / EDS test results

Figure 4 Thermal test The profile analysis of the lamp encapsulant colloid with failure phenomenon c shows that the blackened part extends from the LED chip to the surface of the lamp bead, and the closer to the surface of the chip and the outer surface of the glue, the more serious the blackening phenomenon occurs. The finite element analysis results are consistent; subsequent simulation experiments of the convection environment of the luminaire found that the heat dissipation performance of the luminaire is susceptible to the environment and the ability to dissipate heat downward is poor. 3. Conclusions Abnormal phenomena occur in the aging process of LED lamps. The black material on the surface of the lamp bead is foreign material. The heat conductive material graphite from the back of the sample has no effect on the heat dissipation of the lamp and the lamp. The encapsulant is black and falling off. The failure phenomenon is caused by the poor heat dissipation capability of the lamp in the light-emitting direction, and the colloid is generated by the dual action of heat of the chip and heat accumulated in the sealed space in a relatively closed space.