The conductive silver paste is a composite material having thermal conductivity, electrical conductivity and bonding properties formed by filling silver powder into a matrix resin. After the matrix resin is cured, as the molecular skeleton of the conductive paste, the mechanical properties and bonding properties of the conductive silver paste are determined. The silver powder forms a network of bonds in the matrix resin to conduct electricity and conduct heat, but is also affected by the matrix resin. Therefore, the selection of the materials of each component and the determination of the amount of addition have a great influence on the performance of the conductive silver paste.
The physical and chemical properties of the conductive silver paste and the solid crystal process play an important role in the bonding and heat dissipation of the silver paste. The performance of the silver paste directly affects the reliability of the LED chip . To this end, Jinjian Testing has launched the LED conductive silver adhesive incoming inspection business, helping LED packaging and lighting fixtures to strengthen quality control and thus improve LED reliability.
Service customers: LED packaging factory, lighting factory
Test content:
1. Size, shape and filling amount of silver powder
The particle size, morphology and filling amount of the silver powder affect the thermal conductivity, electrical conductivity and bonding strength 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 and heat conduction path can be formed.
The particle size affects the resistivity of the conductive silver paste. The conductive paste prepared by using the silver powder with a large particle size has less conductive paths formed per unit volume, which reduces the conductivity, and the conductive powder is made of silver powder with a small particle size. Glue, there are more conductive paths formed per unit volume, and the conductivity of conductive paste is better. Therefore, it is most suitable to select flake silver powder from the viewpoint of conductivity.
The general selection principle of particle morphology based on the principle of conduction is that particles can form a larger contact area with each other. The form of silver particles mainly includes four types: spherical, phosphorous, branch-like, and rod-shaped. In order to obtain a larger contact area between the particles, the preferred order of silver particle morphology is: leaf-like, phosphorus-like, rod-shaped, spherical. Among them, the phosphor flakes and the rods are relatively close. Further, the phosphor flakes and the dendrites are sometimes collectively referred to as flakes. It can be seen from various forms that the contact area is the largest to test the flaky particles. Since the flake silver powder is in line contact or surface contact when forming the conductive path, it is more advantageous for electron transport, thereby improving the utilization efficiency of the silver powder, saving silver powder, and reducing production cost. Therefore, the silver powder with a small particle size and a small particle size has better thermal conductivity and better electrical conductivity than a round one and a large particle size.
The silver powder is filled in a large amount, the volume resistivity of the conductive silver paste is low, and the thermal conductivity is high, but the bonding strength is decreased at the same time, so the filling amount of the silver powder affects the resistivity, thermal conductivity and bonding strength of the colloid.
2. Whether there is stratification or uneven distribution of silver powder after solid crystal
The silver powder particles are dispersed in the slurry system in a suspended state, and the density difference, charge, and cohesion between the silver powder and the matrix are affected.
The influence of many factors such as the force and the structure of the dispersion system often leads to the stratification of silver powder. If the sedimentation is too fast, the product will sag during the hanging of the slurry, the thickness of the coating will be uneven, and even affect the physical properties of the coating film. Performance, delamination also affects the heat dissipation, bond strength and electrical conductivity of the device. A, B
The two-component conductive silver paste needs to be mixed and stirred uniformly before use. Due to the large number of bubbles generated during the stirring process, if these bubbles cannot be eliminated, voids will appear after the solid crystal, which affects the heat dissipation, bonding strength and electrical conductivity of the device.
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