The structure and functions of each part of the semiconductor cooling sheet

I. Core functional unit: PN semiconductor p-n junction pair

This is the core component for achieving the cooling effect, consisting of pairs of P-type semiconductor and N-type semiconductor, usually with bismuth telluride (Bi₂Te₃) as the base material:​

P-type bismuth telluride semiconductor: Formed by doping tellurium sulfide (Sb₂Te₃), with "holes" as the main carrier, and current moves directionally through holes to absorb heat;​

N-type bismuth telluride semiconductor: Made by doping bismuth selenide (Bi₂Se₃), with free electrons as the carrier, and having a higher electron mobility, responsible for heat transfer;​

Structural design: Each single cooling sheet contains tens to hundreds of pairs of PN junctions, arranged in a matrix, designed with "electrical series connection and thermal parallel connection", ensuring continuous current conduction and enhancing heat transfer efficiency.​

II. Structural support and insulation layer:

Ceramic substrate As the "framework" of the cooling sheet, it adopts a double-layer symmetrical design, sandwiched at the outermost layer of the entire structure, with the following core characteristics and functions:​

Main materials: Al₂O₃ ceramic (with a temperature resistance of >160℃), for high-end scenarios, AlN ceramic is used, with better thermal conductivity;​

Three main functions: ① Mechanical support: Fixing the internal PN junctions and the metal connection structure to ensure the stability of the overall structure;

② Electrical insulation: Isolating the external circuit from the internal conductive components to avoid short-circuit risks;

③ Heat conduction channel: Quickly conducting heat between the cold and hot surfaces, reducing thermal resistance.

III. Current Distribution and Heat Conduction Layer: Metal Conductors

1. Located between the ceramic substrate and the PN junction pair, it serves as the key carrier for transmitting both electrical and thermal signals:

2. Metal Current Distributor: Primarily made of copper or copper alloys, it boasts high electrical conductivity and thermal conductivity. Its functions include:

① Connecting adjacent PN semiconductors in series to form a closed circuit;

② Distributing the input current evenly to each pair of junctions to prevent local current concentration;

③ Transferring the heat generated by the PN junction pair to the ceramic substrate;

3. Auxiliary Connection: Some high-end products use gold-tin or indium-tin solder paste for welding, enhancing connection stability and thermal efficiency, and reducing contact thermal resistance.

IV. Auxiliary Components and Integrated Design Apart from the core components, the practical application of the cooling chip also relies on the following auxiliary structures:

1. Electrode Terminal: Located at the edge of the ceramic substrate, it is connected to the external DC power supply through metal pins or pads, providing current input for the entire junction array;

2. Packaging Protection: Some products use silicone grease at the edge to prevent moisture intrusion and mechanical damage, extending the service life;

3. Multi-layer Composite Optimization: Large-power cooling chips adopt a multi-layer junction array stacking design to further increase cooling capacity, while optimizing the thickness of the ceramic substrate (typically 0.5-1mm) to balance thermal conductivity and mechanical strength.