Preparation method of tin and silver composite plating layer with high reflectivity

Abstract

The invention relates to a preparation method of a tin and silver composite plating layer with high reflectivity, and belongs to the technical field of semiconductor illumination. The preparation method comprises the following steps of (1) electrically depositing a tin plating layer onto the surface of a copper substrate by tin sulfate and concentrated sulfuric acid; (2) electrically depositing asilver plating layer onto the surface of the tin plating layer by a nicotinic acid system; (3) annealing the obtained tin and silver composite plating layer, and enabling tin and silver atoms to disperse in a tin and silver solid-solid interface, so as to obtain an Ag3Sn thin film with high reflectivity. The preparation method has the advantages that after annealing, the plating layer is uniformlydistributed; the bonding strength between the plating layers is improved; the Ag3Sn thin film is formed at the surface of the plating layer, so that an HRBE (high reflective back electrode) with highreflectivity and excellent antioxidation property and sulfurizing property is obtained.

Description

technical field [0001] The invention belongs to the field of semiconductor lighting sources, and in particular relates to a preparation method of a high-reflectivity tin-silver composite coating. Background technique [0002] Light Emitting Diode (LED) is a new type of solid-state light source that can directly convert electrical energy into light energy efficiently. Compared with traditional light sources, it has long life, small size, energy saving, high efficiency, fast response, shock resistance, and no pollution. It is a new generation of semiconductor lighting source after incandescent lamps and fluorescent lamps, and has become a green industry that promotes rapid economic development. However, due to the influence of the LED chip package, usually only the light emitted from the front can be effectively used, while the light emitted from the bottom and sides needs to be reflected to the front through the reflective cup. In order to avoid light absorption by the solid...

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Problems solved by technology

However, experiments have shown that the temperature rise process in the subsequent packaging process and the heat transfer at the interface under LED working conditions will cause the Ag atoms at the interface to reunite, greatly changing the flatness of the interface and causing diffuse reflection of photons; and the presence of elements such as S in the environment It is easy to trigger a reaction at the silver interface to generate the corresponding compound, which will cause a sharp increase in contact resistance while affecting the reflectivity.

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