Failure analysis of LED lamp bead with silicone packaging rubber softening

Background:

Light-emitting diode (LED) is widely used in the field of lighting due to its advantages of high efficiency, energy saving and environmental protection.Silicone has excellent heat resistance, aging resistance, high refractive index and low stress, making it an ideal LED packaging material.However, in the process of LED use, there are often phenomena of luminescent instability, dead lamp and lamp failure. This situation may be caused by poor heat dissipation caused by unreasonable internal structure of LED, or stress cracking caused by aging of packaging adhesive, or expansion and softening of packaging adhesive.In order to find out the reasons for the softening of the packaging glue, the silicone packaging glue in LED lamp beads was characterized by means of X-ray, scanning electron microscope, energy spectrum analysis, infrared analysis, thermogravity analysis, etc.In order to solve the LED in the process of use due to the softening of packaging glue caused by unstable light, dead lamp and other problems.

Conclusion:

In the process of using the LED lamp strip, the phenomena of light instability and dead lamp appeared. When the LED lamp strip was disbanded, the packaging adhesive was found to be sticky and soft. In order to find the reason, the packaging adhesive and the inner and outer packaging adhesive in the LED lamp bead were analyzed.Before aging, the surface of LED packaging adhesive was relatively smooth, containing C, O, Si and other elements. After aging, the packaging adhesive showed protruding and swelling phenomenon, accompanied by granular material on its surface. The content of C in the packaging adhesive increased, the content of O and Si decreased, and contained a small amount of Cl.The infrared spectrum showed that both the aging encapsulation adhesive and the inner and outer encapsulation particles contained ester groups, and this result was also confirmed by GC-MS.Therefore, it can be concluded that the fundamental reason for the softening of LED packaging adhesive is that the inner packaging adhesive and the outer packaging adhesive contain more small molecules such as phthalic plasticizer, methyl palmitate and ci-9, 10-epoxyocatecanoate methyl ester. During the use of LED, they migrate to the packaging adhesive, making the packaging adhesive soft and causing poor luminescence of lamp beads.