1. What is an Aluminum PCB

Aluminum PCB is a metal-based copper-clad board with good heat dissipation function. Generally, a single panel is composed of a three-layer structure, which is a circuit layer (copper foil), an insulating layer and a metal base layer. For high-end use, it is also designed as a double panel with a structure of circuit layer, insulation layer, aluminum base, insulation layer and circuit layer. Very few applications are multilayer boards, which can be made by laminating ordinary multilayer boards with insulating layers and aluminum substrates.

2. Working principle of Aluminum PCB

The power device is surface-mounted on the circuit layer. The heat generated during the operation of the device is quickly conducted to the metal base layer through the insulating layer, and then the heat is transferred by the metal base layer to achieve the heat dissipation of the device.

3. Structure of Aluminum PCB

Aluminum-based copper clad board is a metal circuit board material consisting of copper foil, thermally conductive insulation layer and metal substrate. Its structure is divided into three layers:
CIREUITL LAYER: equivalent to the copper-clad board of ordinary PCB, the thickness of the line copper foil LOZ to 10OZ
DIELCCTRIC LAYER: Insulation layer, is a layer of low thermal resistance thermally conductive insulating material
BASE LAYER: Metal substrate, usually aluminum or copper. Aluminum-based copper clad laminates and traditional epoxy glass cloth laminates.

The circuit layer (ie copper foil) is usually etched to form a printed circuit, so that the various components of the component are connected to each other. In general, the circuit layer is required to have a large current carrying capacity, so a thicker copper foil should be used, and the thickness is generally 35 & MU; M ~ 280 & MU; M; The thermal insulation layer is the core technology of the aluminum substrate. It is generally composed of a special polymer filled with a special ceramic. It has a small thermal resistance, excellent viscoelastic properties, and has the ability to resist thermal aging and to withstand machinery. And thermal stress.
The high-performance aluminum substrate's thermally conductive insulating layer uses this technology to make it have excellent thermal conductivity and high-strength electrical insulation. The metal base layer is a supporting member of the aluminum substrate and requires high thermal conductivity. Generally, it is an aluminum plate. Copper plates can also be used (where copper plates can provide better thermal conductivity), which is suitable for conventional machining such as drilling, punching and cutting.
PCB materials have incomparable advantages compared to other materials. Suitable for surface mount SMT technology of power components. No heat sink is needed, the volume is greatly reduced, the heat dissipation effect is excellent, and the good insulation performance and mechanical performance.

4. Performance characteristics of Aluminum PCB

1) Using surface mount technology (SMT);
2) Extremely effective treatment of thermal diffusion in circuit design schemes;
3) Reduce product operating temperature, increase product power density and reliability, and extend product service life;
4) Reduce product size, reduce hardware and assembly costs;
5) Replace the fragile ceramic substrate to obtain better mechanical durability.

5. Process capability of Aluminum PCB

Process of aluminum substrate and process related vocabulary
5.1 Undercut: The etching of the side wall of the wire under the resist pattern is called undercut. The degree of side etching is expressed by the width of the side etching.
Side etching is related to the type and composition of the etching solution and the etching process and equipment used.
Etching coefficient: The ratio of the thickness of the wire (excluding the thickness of the plating layer) to the amount of side etching is called the etching coefficient.
Etching coefficient = V / X
Use the level of the etch coefficient to measure the amount of side etch. The higher the etch coefficient, the less the side etch. In the etching operation of printed boards, it is desirable to have a high etching coefficient, especially for printed boards with high-density fine wires. Widening of the plating layer When the pattern is plated, the width of the wire is increased because the thickness of the plated metal layer exceeds the thickness of the plating resist layer, which is called plating widening. The widening of the plating layer is directly related to the thickness of the plating resist and the total thickness of the plating layer. In actual production, we should try to avoid the widening of the coating.
5.2 Plating edge: The sum of the widening of the metal resist coating and the amount of side erosion is called the plating edge. If the coating is not widened, the plating flange is equal to the side erosion amount.
5.3 Etching rate: The depth of the metal (often expressed in μm / min) or the time required to dissolve a certain thickness of metal (min) by the etchant in a unit time.
5.4 Copper dissolving amount: the amount of copper dissolved by the etching solution at a certain allowable etching rate. It is often expressed in grams of copper (g / l) dissolved per liter of etching solution. For certain etching solutions, its copper dissolving ability is certain.

6. Packaging of Aluminum PCB

LED packaging is mainly to provide a platform for LED chips, so that LED chips have better light, electrical, and thermal performance. Good packaging can allow LEDs to have better luminous efficiency and a good heat dissipation environment. Life. LED packaging technology is mainly built on five main considerations, namely optical extraction efficiency, thermal resistance, power dissipation, reliability and cost performance (Lm / $).
Each of the above factors is a very important link in the package. For example, light extraction efficiency is related to cost performance; thermal resistance is related to reliability and product life; power dissipation is related to customer applications. On the whole, the better packaging technology must take into account every point, but the most important thing is to think from the customer's standpoint, which can meet and exceed customer needs, which is good packaging.
Single or double-layer aluminum substrates are usually used as heat sinks. A single chip or multiple chips are directly fixed to the aluminum substrate (or copper substrate) with die-bonding adhesive. A thin copper plate on the surface of a substrate. The number of LED chips arranged on the base is determined according to the required power, which can be combined and packaged into 1W, 2W, 3W and other high-brightness high-power LEDs. Finally, high-refractive-index materials are used to package the integrated LEDs in the shape of the optical design.

7. Use of Aluminum PCB

Uses: Power Hybrid IC (HIC)
7.1 Audio equipment: input, output amplifier, balanced amplifier, audio amplifier, preamplifier, power amplifier, etc.
7.2 Power supply equipment: switching regulator, DC / AC converter, SW regulator, etc.
7.3 Communication electronic equipment: high-frequency amplifiers, filter appliances, and transmission circuits.
7.4 Office automation equipment: motor drivers, etc.
7.5 Automobile: electronic regulator, igniter, power controller, etc.
7.6 Computer: CPU board, floppy disk drive, power supply unit, etc.
7.7 Power module: converter, solid state relay, rectifier bridge, etc.

8. Aluminum PCB sheet

The aluminum-based plates commonly used for aluminum substrate plates are mainly 1000 series, 5000 series, and 6000 series. The basic characteristics of these three series of aluminum materials are as follows:
8.1 1000 series: stands for 1050, 1060, 1070. The 1000 series aluminum plate is also called pure aluminum plate. Among all the series, the 1000 series is the most aluminum-containing and the purity can reach 99.00% or more. 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.
8.2 5000 series: Represents 5052, 5005, 5083, 5A05 series. 5000 series aluminum plate belongs to the more commonly used alloy aluminum plate series. The main element is magnesium with a magnesium content of 3-5%. It 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 other series, so it is often used in aviation, such as aircraft fuel tanks. In addition, it is widely used in conventional industries.
8.3 6000 series: represents 6061, mainly contains two elements of magnesium and silicon, so the advantages of the 4000 series and the 5000 series are concentrated. 6061 is a cold-treated aluminum forged product, which is suitable for applications with high requirements for corrosion resistance and oxidation. Good workability, excellent interface characteristics, easy coating, and good processability. 6061 general characteristics: excellent interface characteristics, easy coating, high strength, good workability, strong corrosion resistance. Typical uses of 6061 aluminum: aircraft parts, camera parts, couplers, marine accessories and hardware, electronic accessories and connectors.

9. Led Aluminum PCB

Led aluminum refers to the aluminum substrate used in the special led industry. The introduction of LED aluminum substrate products has opened the development of heat dissipation applications. Due to the heat dissipation characteristics of LED aluminum substrates, plus aluminum substrates have high heat dissipation, low thermal resistance, long life, and voltage resistance. And other advantages, and further expand the application area of the LED industry, such as aluminum substrates for home appliances, aluminum substrates for automotive lights, aluminum substrates for street lamps, and large-scale outdoor signage.
The thermal conductivity of the led aluminum substrate is related to the insulation layer in the middle of the aluminum substrate (generally PP, and now there is a thermal conductive adhesive, etc.). It is one of the three major standards for measuring the quality of the aluminum substrate (the thermal resistance value and the withstand voltage value are The other two properties). The thermal conductivity of the aluminum substrate can be obtained by testing the test equipment after the plates are laminated. At present, the high thermal conductivity is generally ceramics, copper, etc. However, due to the consideration of cost, the mainstream aluminum electronic substrate is currently on the market. The corresponding thermal conductivity of the aluminum substrate is a parameter that everyone is concerned about, and the higher the thermal conductivity is one of the signs that indicates better performance.
The led aluminum substrate is the PCB, which is also the meaning of the printed circuit board, but the material of the circuit board is aluminum alloy. Previously, the material of our general circuit board was glass fiber.

10. Delivery time of Aluminum PCB

Attention should be paid to the production of aluminum substrates:
10.1 Delivery (usually 3-5 days for proofing) Batch (5-7 days)
10.2 Quality requirements (size, thickness, workmanship, are there any special requirements?)
10.3 Is there a post-production batch of aluminum substrates and is there a long-term cooperation?

11. Thermal conductivity of high thermal conductivity Aluminum PCB
As the name implies, the thermal conductivity of aluminum substrate is a kind of heat dissipation parameter of aluminum substrate. It is one of the three major standards for measuring the quality of aluminum substrate (thermal resistance value and withstand voltage value are the other two properties). The thermal conductivity of the aluminum substrate can be obtained by testing the instrument after the plates are laminated. The current high thermal conductivity is generally ceramics, copper, etc., but due to the consideration of cost, most of the aluminum substrates on the market are currently corresponding. The thermal conductivity of the aluminum substrate is a parameter that everyone is concerned about, and the higher the thermal conductivity is one of the indicators of better performance. Aluminum substrate is a unique metal-based copper-clad aluminum substrate, which has good thermal conductivity, electrical insulation properties and machining performance.
Under normal circumstances, aluminum substrates are used in LED design and various electronic designs, while LED thermal design is based on fluid dynamics software simulation and basic design. This is very important for the production of aluminum substrates. necessary.
The so-called fluid flow resistance is due to the viscosity of the fluid and the solid boundary, which causes the fluid to receive a certain resistance during the flow process. This resistance is called flow resistance, which can be divided into two types of resistance along the path and local resistance; The path resistance is the area where the boundary changes rapidly, such as the sudden enlargement or sudden reduction of the section, the elbow and other local positions. It is the flow resistance caused by the sudden change of the fluid flow state.

Generally, the heat sink used in the LED aluminum substrate is natural heat dissipation. There are three main steps in the design process of the heat sink:
11.1 Design the outline drawing of the radiator according to the relevant constraints;
11.2 Optimize the tooth thickness, tooth shape, tooth pitch, and thickness of the aluminum substrate according to the relevant design guidelines of the aluminum substrate radiator;
11.3 Perform check calculations to ensure the heat dissipation performance of the radiator.

12. Thermal design of Aluminum PCB

12.1 Why thermal design?
The impact of high temperature on electronic products: degradation of insulation performance; damage to components; thermal aging of materials; cracking of low-melting welds and falling of solder joints.
The effect of temperature on components: Generally speaking, the resistance value of the resistance decreases when the temperature increases; the high temperature will reduce the service life of the capacitor; the high temperature will reduce the performance of the transformer and choke insulation materials; To be lower than 95C; too high temperature will cause changes in the alloy structure of the solder joint-IMC thickens, the solder joint becomes brittle, and the mechanical strength decreases; the increase in junction temperature will cause the current magnification of the transistor to increase rapidly, resulting in collector current Increasing it will further increase the junction temperature and eventually lead to component failure.
The purpose of thermal design is to control the temperature of all electronic components inside the product so that it does not exceed the maximum temperature specified by standards and specifications under the working environment conditions. The calculation of the maximum allowable temperature should be based on the stress analysis of the components and should be consistent with the reliability requirements of the product and the failure rate assigned to each component.
12.2 Solutions to heat dissipation problems of Aluminum PCB
The heat dissipation problem of LED is the most headache problem for LED manufacturers. However, an aluminum substrate can be used because aluminum has a high thermal conductivity and good heat dissipation, which can effectively dissipate internal heat. The aluminum substrate is a unique metal-based copper-clad board, which has good thermal conductivity, electrical insulation properties, and machining properties. Design the PCB as close to the aluminum base as possible to reduce the thermal resistance of the potting compound.

13. Application and characteristics of Aluminum PCB

The Aluminum PCB is constructed by itself and has the following characteristics: very good thermal conductivity, copper binding on one side, devices can only be placed on the copper binding surface, and electrical connection holes cannot be opened, so jumpers cannot be placed like single panels.
SMD devices, tubes, and output rectifier tubes are generally placed on the aluminum substrate to conduct heat through the substrate. The thermal resistance is very low and high reliability can be achieved. The transformer adopts a flat patch structure and can also dissipate heat through the substrate. Its temperature rise is lower than the conventional one. The transformer with the same specifications using the aluminum substrate structure can obtain larger output power.

Due to the excellent thermal conductivity of the aluminum substrate, it is more difficult to solder manually in a small amount, the solder is cooled too quickly, and it is prone to problems. A simple and practical method is available. An ordinary iron for ironing (preferably a temperature adjustment function), Turn it over, iron the side up, fix it, adjust the temperature to about 150 ° C, place the aluminum substrate on the iron, warm it up for a while, and then attach and solder the components according to conventional methods. The iron temperature should be easy to solder. If it is too high, the device may be damaged, or even the copper substrate of the aluminum substrate is peeled off. If the temperature is too low, the soldering effect is not good, so you must be flexible.