PCB Blog - Discussion on Aluminum substrate

The PCB board we commonly use is coated with copper on one or both sides on the surface of the insulating board. As the specific form of PCB, the aluminum substrate is usually coated with copper on one side, and the insulating layer is very thin, and then the aluminum board is superimposed on the side without copper coating, that is, the so-called aluminum substrate, which is usually used in audio, power supply, communication electronic equipment, automobiles, computers, lamps and lighting, etc.

So, what's good about aluminum substrates?

Aluminum material

Good heat dissipation performance: the aluminum substrate can minimize the thermal resistance, have smaller thermal resistance, and the thermal expansion coefficient is closer to that of copper foil, so that the aluminum substrate has excellent thermal conductivity and heat dissipation performance, reduce the operating temperature of the module, and extend the service life.

High current carrying capacity: with the same thickness and line width, the aluminum substrate can carry higher current.

Good machinability: it can replace ceramic substrate and have better mechanical durability. At the same time, with high strength and toughness, it can realize large-area PCB manufacturing and component mounting.

Good electromagnetic wave shielding: in order to ensure the performance of electronic circuits, some components in electronic products need to prevent electromagnetic wave radiation and interference. The aluminum substrate can act as a shielding plate to shield electromagnetic waves

Environmental protection: aluminum used as raw materials is non-toxic and recyclable. Meet ROHS requirements.

Light weight: aluminum has amazing light weight and convenience under the condition of excellent strength and elasticity.

However, from the perspective of process and selectivity, aluminum substrates still have some shortcomings in the existing market, such as:

High cost: compared with parity goods, the price of aluminum substrate accounts for more than 30%.

High process difficulty: at present, it is difficult to make double-sided boards, and the process is complex. In the manufacturing process, voltage withstand and electrical strength are also prone to problems.

Plate is not unified: CPCA industry standards, national standards, international standards, etc., there is no unified standard for material specifications.

Aluminum base plate commonly used aluminum base plate mainly includes 1000 series, 5000 Series and 6000 series.

① 1000 series

It represents 1050, 1060, 10701000 series aluminum plates, also known as pure aluminum plates. Among all series, 1000 series has the most aluminum content, and the purity can reach more than 99.00%. Because it does not contain other technical elements, the production process is relatively simple and the price is relatively cheap. It is the most commonly used series in conventional industry at present. At present, most of the circulation in the market is

1050 and 1060 series. 1000 series aluminum plates determine the minimum aluminum content of this series according to the last two digits. For example, the last two digits of 1050 series are 50. According to the international brand naming principle, the aluminum content must reach 99.5% and above is regarded as qualified products. In China's aluminum alloy technical standard (gb/t3880-2006), 1050 also clearly stipulates that the aluminum content reaches 99.5%.

Similarly, the aluminum content of 1060 series aluminum plates must reach more than 99.6%.

② 5000 Series

Represents 5052, 5005, 5083, 5A05 series. 5000 series aluminum plate is a series of commonly used alloy aluminum plates. The main element is magnesium, with a magnesium content of 3-5%, which is also called aluminum magnesium alloy. The main features are low density, high tensile strength and high elongation. Under the same area, the weight of aluminum magnesium alloy is lower than that of other series, so it is often used in aviation, such as aircraft fuel tank. another

It is also widely used in conventional industries. Its processing technology is continuous casting and rolling, which belongs to the hot-rolled aluminum plate series, so it can do deep oxidation processing. In China, 5000 series aluminum plate is one of the more mature aluminum plate series.

③ 6000 Series

Representative 6061 mainly contains magnesium and silicon, so it integrates the advantages of 4000 series and 5000 series. 6061 is a cold-treated aluminum forging product, which is suitable for applications requiring high corrosion resistance and oxidation resistance. It has good usability, excellent interface characteristics, easy coating and good processability. General features of 6061: excellent interface features, easy coating, high strength and good usability

, strong corrosion resistance. Typical uses of 6061 aluminum: aircraft parts, camera parts, couplers, ship accessories and hardware, electronic accessories and connectors, etc.

Considering the texture, hardness, elongation, chemical properties and price of the material itself, 5052 alloy aluminum plate of 5000 series aluminum materials is generally used for aluminum substrates at present.

Dielcctriclayer insulating layer: the insulating layer is a layer of low thermal resistance and heat conduction insulating material.

Baselayer base: it is a metal substrate, usually aluminum or optional copper. Aluminum based copper clad laminate and traditional epoxy glass cloth laminate.

Aluminum structure

Aluminum substrate is a kind of copper clad laminate using aluminum as the substrate, which has good heat dissipation. We generally use aluminum substrates for circuit boards that need good heat dissipation. In the application of LED lamps, because the heat of LED is large, if the heat is not dissipated in time, the brightness is easy to decay, and even burn the chip. Aluminum is a metal with good thermal conductivity. LED light beads can be installed on the aluminum substrate

To dissipate the heat quickly. The aluminum substrate is designed with an insulating layer, which will not conduct electricity. If it conducts electricity, there is no way to design circuits on it.

This technology is used in the thermal insulation layer of high-performance aluminum substrate, which makes it have extremely excellent thermal conductivity and high-strength electrical insulation performance; The metal base is the supporting member of the aluminum substrate, which requires high thermal conductivity. Generally, it is aluminum plate, and copper plate can also be used (copper plate can provide better thermal conductivity), which is suitable for conventional machining such as drilling, punching and cutting.

Compared with other materials, PCB has incomparable advantages. Suitable for SMT public art of surface mounting of power components. Without radiator, the volume is greatly reduced, the heat dissipation effect is excellent, and the insulation and mechanical properties are good.

There are generally three layers of single-sided aluminum substrate, including circuit layer (copper foil), insulation layer and aluminum metal base. There is an insulating layer between the circuit layer and the aluminum base, so it will not cause a short circuit. The double-layer high-end aluminum substrate has a circuit layer on both sides, of course, the middle is aluminum. Multilayer aluminum substrates are rare.

Generally, LED lamps use single-sided aluminum substrate, and the circuit layer is pasted with LED. The aluminum substrate on the back can be in good contact with the radiator to dissipate heat.

The insulation layer in the aluminum substrate is the most critical and the core technology of the aluminum substrate. It should not only adhere to the copper foil, but also have good thermal conductivity, because the insulation layer of the aluminum substrate is the biggest thermal conductivity barrier. If the heat of the copper foil cannot be quickly transferred to the aluminum substrate, the aluminum substrate will lose its significance.

Characteristics of LED aluminum substrate

1. Adopt surface mount technology (SMT);

2. Very effective treatment of thermal diffusion in the circuit design scheme;

3. Reduce the operating temperature of the product, improve the power density and reliability of the product, and extend the service life of the product;

4. Reduce the volume of products and reduce hardware and assembly costs;

5. Replace the fragile ceramic substrate to obtain better mechanical durability.

Application of LED aluminum substrate

Purpose: Power Hybrid IC (HIC).

1. Audio equipment: input and output amplifiers, balance amplifiers, audio amplifiers, preamplifiers, power amplifiers, etc.

2. Power supply equipment: switch regulator `dc/ac converter `sw regulator, etc.

3. Communication electronic equipment: high frequency amplifier ` filter electric appliance ` sending circuit. 4. Office automation equipment: motor driver, etc.

5. Automobile: electronic regulator, igniter, power controller, etc.

6. Computer: CPU board, floppy disk drive, power supply device, etc.

7. Power module: inverter, solid relay, rectifier bridge, etc