Conductive silver paste is a composite material with thermal conductivity, electrical conductivity and bonding properties formed by filling micron or nano silver powder into epoxy resin. Silver plastic physical, chemical properties and solid crystal technology play an important role in the bonding and heat dissipation of silver glue. The performance of silver glue directly affects the reliability of the chip. Therefore, strengthening the quality control of the silver glue can effectively improve the reliability of the LED .
Customer service: LED packaging factory, lighting factory
Detection means: sectioning, scanning electron microscopy (SEM), energy spectrum analysis (EDS)
Test content:
1. Silver powder particle morphology, particle size, filling amount
The particle size, shape and filling amount of the silver powder affect the thermal conductivity and electrical conductivity of the silver paste. After the good conductive silver paste is cured, the epoxy resin is less, and the silver powder particles are in close contact, and a good conductive path can be formed. The silver powder with a small sheet size and small particle size has better thermal conductivity and better electrical conductivity than a round one and a large particle size.
2. Whether there is delamination or void after solid crystal
The internal basic structure of the silver gel after curing is a mixture of epoxy resin and silver powder. The poor quality of the silver glue or the solid crystal process may cause delamination and voids, which may affect the heat dissipation effect.
case analysis:
A company's LED lamp bead reliability problems, pass LM-80 certification, commissioned the gold check to find the cause of failure. By slicing and SEM analysis of unaged and aged lamp beads, it was found that the unaged lamp bead solid glue had two defects:
1. There are obvious voids in the junction of the solid crystal glue and the support, and the combination of the chip back gold and the solid crystal glue. These voids will affect the bonding, thermal and electrical conductivity of the silver paste, reduce the heat dissipation capability, and thus affect the luminous efficiency of the chip.
2. The solid crystal glue has serious delamination phenomenon, that is, the resin sinks underneath, the silver powder floats on the top, and the silver powder is not in contact with the substrate, but the resin, which increases the thermal resistance of the lamp bead and reduces the reliability of the product.
It is recommended that the company strengthen the inspection of incoming glue and standardize the use of glue.
Conductive silver glue incoming inspection (SEM scanning electron microscope)
Scanning electron micrograph shows silver cracking and delamination
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