We must consider a few fundamental parameters when calculating aluminum PCB thermal conductivity. These variables include the thermal resistance of the aluminum substrate, the metal via, and the thermal resistance of the top and bottom metal sheets. The corresponding equations are LJ, T, ts, bs, a, and Tf.
Heat dissipation
Aluminum PCBs are commonly helpful in electronic devices requiring extremely high heat dissipation. In addition to being more stable than other materials, aluminum PCBs are also far less expensive to produce. As a result, we can find them in various applications, from audio equipment to power supply equipment.
The main difference between aluminum and FR-4 PCBs is thermal resistance. The former has a thermal resistance of approximately 20-22 W/mK, while the latter is one to two W/mK. As a result, high temperatures cause localized heating of electronic devices, leading to components burning or failing altogether. Aluminum PCBs can mitigate this issue and improve the durability of the entire machine.
Another advantage of aluminum PCBs is that they have a low coefficient of thermal expansion, making them suitable for applications requiring high mechanical stability. This feature makes aluminum boards much more efficient than their fiberglass counterparts, enabling higher power and density. This is especially useful in applications requiring high temperature and dimensional tolerances.
To calculate the aluminum PCB heat dissipation of a PCB, you must first understand how thermal energy moves to the aluminum PCB. We can do this by using equations relating to the thermal resistance of a PCB and its junction. Once you have this data, you can use it to calculate the total power dissipated.
Thermal relief
We calculate aluminum PCB thermal conductivity using a unique formula. The material typically heats to about 140 to 150 degrees C. At that temperature, it loses its mechanical strength and begins to soften. This characteristic enables engineers to reduce labor and production costs and board size.
This formula uses the thermal resistance of a metal to determine its thermal conductivity. Copper, for instance, has a thermal resistance of c. When considering thermal conductivity, you need to consider the amount of metal in the board and the number of prepregs used.
Another important factor is heat dissipation. High-power components require heat sinks to dissipate heat from the board effectively. Heat sinks are the most effective way to dissipate heat, especially during reflow and operation. The lower the thermal resistance of a circuit board, the better it is for heat dissipation.
A four-layer aluminum PCB consists of two copper layers and two PP layers. The heat from LED components passes through the aluminum base, the first copper layer, and the second PP layer. As a result, these four layers all have lower thermal conductivity than single-layer or dual-sided aluminum PCBs.
The thermal resistance of aluminum substrates is an essential indicator of the quality of the substrate. Copper and ceramic materials have high thermal conductivity, and aluminum substrates are one of the most common types. Aluminum substrates are ideal because of their excellent thermal conductivity and electrical insulation properties. In addition, aluminum substrates have excellent mechanical processing properties.
Thermal vias
When choosing the suitable substrate for your PCB, thermal conductivity is an essential factor to consider. Generally, a high thermal conductivity aluminum substrate will have a smaller thermal resistance value than a low thermal conductivity aluminum substrate. However, aluminum PCBs can also have higher thermal resistance values than other materials.
Whether or not your board has the right thermal resistance depends on several factors, including the materials used to make the board and the components used in its construction. If you choose components with favorable temperature parameters for the components you are using, you can minimize the effects of thermal resistance on your PCB. For example, FR-4 is an excellent insulator, but it can have very low thermal conductivity and can easily be overheated when operating at high temperatures.
We can measure thermal conductivity in Watts per meter Kelvin. Copper and aluminum are conductive metals and have different thermal properties. Copper conducts heat very quickly, while aluminum is more difficult to heat. The difference between copper and aluminum is in the PP layer. A PP layer consists of a polymer filled with ceramics, and this layer determines how well aluminum circuit boards can conduct heat.
The thermal resistance of a PCB depends on how many thermal vias it has. One thermal via is 0.6 mm in diameter. Therefore, the thermal resistance of a board further increases with the increase in the number of thermal vias. For example, a board with five 0.6 mm thermal vias has 12 degC/W thermal resistance.
Thermal pads
Thermal conductivity in a circuit board determines how the heat will move around the board. The copper conductors and substrate will affect how much heat will generate and transfer and how much will be radiated away from critical components. Copper traces are used for circuit boards because they provide low-resistance flow paths and shield against EMI. Copper pads below the components direct the heat away from the surface layer.
The aluminum core PCB has a lower thermal conductivity than copper-based circuit boards. Therefore, it is difficult to penetrate the aluminum oxide layer, which makes two-wire resistance measurements difficult. As a result, contact resistance is the primary source of error. To get accurate measurements, it is essential to factor in the resistivity value r of aluminum. The resistivity value r of aluminum is 28nO*m. For low-temperature aluminum circuit boards, we use the alloy 3003-H18.
Thermal resistance and withstand voltage are also important indicators of aluminum substrate quality. We can measure them with an instrument. Aluminum PCBs with high thermal conductivity is more expensive than low-quality aluminum substrates.
Circuit board structure
Aluminum PCB Thermal Conductivity is the measure of how well a material conducts heat. Copper and aluminum PCB boards have varying thermal conductivities, ranging from 200W/mK to 400W/mK. The thermal resistance of the PCB also has to be taken into account when calculating thermal conductivity.
The metal backing plate is the thickest material on the board. It is typically 1mm or 1.5mm thick. This provides rigidity to the circuit and sufficient thickness for mounting hardware. The exposed side of the metal plate is typical without a solder mask or surface finish. This is because the aluminum layer has poor thermal conductivity.
Two different methods determine the aluminum PCB Thermal Conductivity. One involves measuring the trace resistance of aluminum with two wires. However, this method is more complex than that used for copper. This is because surface aluminum oxide may prevent the copper trace from penetrating it. Furthermore, the contact resistance will override the line resistance and lead to errors.
Thermal resistance is the measure of how heat flows around the circuit board. It is necessary to determine the most effective heat management techniques. For example, copper conductors are the most effective for heat transfer from LEDs, while aluminum is better for transferring heat from high-power SMD parts. The lower the resistance, the better for heat dissipation.
Summary
The effective aluminum PCB Thermal Conductivity measures its ability to conduct heat—the higher its thermal conductivity, the better the performance of the electronic circuit. Insulating layers can influence this property on the aluminum substrate. Copper and ceramics are commonly essential as aluminum substrates, but aluminum is also an excellent material for this purpose.
The thermal conductivity of a material depends on its composition, temperature, apparent density, porosity, and moisture content. Materials with high porosity, low moisture content, and a low apparent density will have better heat insulation properties. There are various kinds of aluminum, and their thermal conductivity can vary from one type to another.
Effective thermal conductivity of aluminum PCB measures the thermal performance of aluminum substrate after lamination. Copper and ceramics have high thermal conductivity. However, aluminum is unique because it is a metal-based copper-clad aluminum substrate. In addition, Multilayer aluminum PCBs are made of several layers, making it difficult to dissipate heat.
