The aluminum substrate is a metal-based copper clad laminate with good heat dissipation function. It is a plate-like material made of electronic glass fiber cloth or other reinforcing materials impregnated with resin, single resin, etc. as an insulating adhesive layer, covered with copper foil on one or both sides and hot pressed, referred to as aluminum-based copper-clad plate . Kangxin Circuit introduces the performance of aluminum substrate and the surface treatment of materials.
Aluminum substrate performance
1.Excellent heat dissipation performance
Aluminum-based copper-clad plates have excellent heat dissipation performance, which is the most prominent feature of this type of plate. The PCB made of it can not only effectively prevent the working temperature of the components and substrates loaded on it from rising, but also quickly heat generated by power amplifier components, high power components, large circuit power switches and other components. It is also distributed because of its small density, light weight (2.7g/cm3), anti-oxidation, and cheaper price, so it has become the most versatile and the largest amount of composite sheet in metal-based copper clad laminates. The saturated thermal resistance of the insulated aluminum substrate is 1.10℃/W and the thermal resistance is 2.8℃/W, which greatly improves the fusing current of the copper wire.
2.Improve the efficiency and quality of machining
Aluminum-based copper-clad laminates have high mechanical strength and toughness, which is much better than rigid resin-based copper-clad laminates and ceramic substrates. It can realize the manufacture of large-area printed boards on metal substrates, and is particularly suitable for mounting heavy components on such substrates. In addition, the aluminum substrate also has good flatness, and it can be assembled and processed on the substrate by hammering, riveting, etc. or bent and twisted along the non-wiring portion on the PCB made of it, while the traditional resin-based copper clad laminate cannot .
3.High dimensional stability
For various copper clad laminates, there is a problem of thermal expansion (dimensional stability), especially the thermal expansion in the thickness direction (Z-axis) of the board, which affects the quality of metallized holes and wiring. The main reason is that the linear expansion coefficients of the plates are different, such as copper, and the linear expansion coefficient of the epoxy glass fiber cloth substrate is 3. The linear expansion of the two is very different, which is easy to cause the difference in thermal expansion of the substrate, causing the copper circuit and the metallized hole to break or be damaged. The linear expansion coefficient of the aluminum substrate is between, it is much smaller than the general resin substrate, and is closer to the linear expansion coefficient of copper, which is conducive to ensuring the quality and reliability of the printed circuit.
Surface treatment of aluminum substrate material
1. Deoiling
The surface of the aluminum-based plate is coated with an oil layer during processing and transportation, and it must be cleaned before use. The principle is to use gasoline (general aviation gasoline) as a solvent, which can be dissolved, and then use a water-soluble cleaning agent to remove oil stains. Rinse the surface with running water to make it clean and free of water drops.
2. Degrease
The aluminum substrate after the above treatment still has unremoved grease on the surface. To completely remove it, soak it with strong alkali sodium hydroxide at 50°C for 5 minutes, and then rinse with clean water.
3. Alkaline etching. The surface of the aluminum plate as the base material should have a certain roughness. Since the aluminum substrate and the aluminum oxide film layer on the surface are both amphoteric materials, the surface of the aluminum base material can be roughened by using the acidic, alkaline or composite alkaline solution system. In addition, other substances and additives need to be added to the roughening solution to achieve the following purposes.
4. Chemical polishing (dipping). Because the aluminum base material contains other impurity metals, it is easy to form inorganic compounds that adhere to the surface of the substrate during the roughening process, so the inorganic compounds formed on the surface should be analyzed. According to the analysis results, prepare a suitable dipping solution, and place the roughened aluminum substrate in the dipping solution to ensure a certain time, so that the surface of the aluminum plate is clean and shiny.