PCB News - What is aluminum substrate

What is aluminum substrate

Aluminum substrate (English translation is Aluminum substrate) is a metal-based copper-clad laminate with good heat dissipation function. Generally, a single-sided board 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-sided board, and the structure is circuit layer, insulating layer, aluminum base, insulating layer, and circuit layer. Very few applications are multi-layer boards, which can be formed by bonding ordinary multi-layer boards with insulating layers and aluminum bases.
The working principle of aluminum substrate

The surface of the power device is mounted on the circuit layer, and the heat generated during the operation of the device is quickly transferred to the metal base layer through the insulating layer, and then the heat is transferred from the metal base layer to realize the heat dissipation of the device

The structure of the aluminum substrate
Aluminum-based copper clad laminate is a metal circuit board material, composed of copper foil, thermally conductive insulating layer and metal substrate. Its structure is divided into three layers:
CIREUITL.LAYER circuit layer: equivalent to the copper clad laminate of ordinary PCB, the thickness of the circuit copper foil is LOZ to 10OZ
DIELCCTRICLAYER insulating layer: the insulating layer is a layer of low thermal resistance thermally conductive insulating material
BASELAYER base layer: is a metal substrate, generally aluminum or copper can be selected. Aluminum-based copper clad laminates and traditional epoxy glass cloth laminates, etc.
The circuit layer (that is, copper foil) is usually etched to form a printed circuit to connect the various components of the component. Generally, the circuit layer requires a large current-carrying capacity, so thicker copper foil should be used, the thickness is generally 35Μ M~280ΜM; The thermal insulation layer is the core technology of the aluminum substrate. It is generally composed of a special polymer filled with special ceramics. It has low thermal resistance, excellent viscoelasticity, thermal aging resistance, and can withstand mechanical And thermal stress.
The thermal insulation layer of the high-performance aluminum substrate uses this technology to make it have extremely excellent thermal conductivity and high-strength electrical insulation performance; the metal base layer is the supporting member of the aluminum substrate and requires high thermal conductivity, generally aluminum plate, Copper plate can also be used (the copper plate can provide better thermal conductivity), which is suitable for conventional machining such as drilling, punching and cutting.
Compared with other materials, PCB materials have incomparable advantages. Suitable for surface mount SMT public art of power components. No radiator is needed, the volume is greatly reduced, the heat dissipation effect is excellent, and the insulation performance and mechanical performance are good.

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

Process and process-related vocabulary explanation of aluminum substrate
Undercutting: The etching that occurs on the sidewall of the wire under the resist pattern is called undercutting. 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 coating) to the amount of side etching is called the etching coefficient.
Etching coefficient=V/X
The level of etching coefficient is used to measure the amount of side etching. The higher the etching coefficient, the smaller the amount of side etching. In the etching operation of printed boards, it is desirable to have a higher etching coefficient, especially for printed boards with high-density fine wires. Plating widening During pattern electroplating, because the thickness of the electroplated metal layer exceeds the thickness of the electroplated resist layer, the width of the wire increases, which is called widening of the plating. The broadening 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, try to avoid the broadening of the coating.
Coating edge: The sum of the broadening of the metal anti-corrosion coating and the amount of side etching is called the coating edge. If there is no widening of the coating, the edge of the coating is equal to the amount of side erosion.
Etching rate: the depth of the etching solution to dissolve metal in a unit time (usually expressed in μm/min) or the time required to dissolve a certain thickness of metal (min).
Dissolved copper amount: The amount of copper dissolved in the etching solution at a certain allowable etching rate. It is often expressed in terms of how many grams of copper are dissolved per liter of etching solution (g/l). For a specific etching solution, its ability to dissolve copper is certain.

Aluminum substrate packaging
LED packaging is mainly to provide a platform for LED chips, so that LED chips have better light, electricity, and heat performance. Good packaging can make LEDs have better luminous efficiency and a good heat dissipation environment, and a good heat dissipation environment will improve the LED Service life. LED packaging technology is mainly based 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 packaging. 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 best packaging technology must take into account every point, but the most important thing is to think from the customer's standpoint, and can meet and exceed customer needs, which is a good packaging.
Usually a single-layer or double-layer aluminum substrate is used as a heat sink, and a single chip or multiple chips are directly fixed on the aluminum substrate (or copper substrate) with die-bonding glue, and the p and n electrodes of the LED chip are bonded to the aluminum The thin copper board on the surface of the substrate. Determine the number of LED chips arranged on the base according to the size of the required power, which can be combined and packaged into high-brightness high-power LEDs such as 1W, 2W, and 3W. Finally, use high refractive index materials to package the integrated LED in the shape of the optical design.

Use of aluminum substrate
Purpose: Power Hybrid IC (HIC)
1. Audio equipment: input and output amplifiers, balanced amplifiers, audio amplifiers, pre-amplifiers, power amplifiers, etc.
2. Power supply equipment: switching regulators, DC/AC converters, SW regulators, etc.
3. Communication electronic equipment: high-frequency amplifiers, filter appliances, and transmission circuits.
4. Office automation equipment: motor drives, etc.
5. Automobile: electronic regulator, igniter, power controller, etc.
6. Computer: CPU board, floppy disk drive, power supply unit, etc.
7. Power modules: inverters, solid state relays, rectifier bridges, etc.