Aluminum oxide PCB is a ceramic PCB that uses aluminum oxide as the substrate material. It is the most popular and inexpensive common ceramic PCB, including aluminum oxide, aluminum nitride, beryllium oxide, and silicon carbide. Aluminum oxide PCB is most widely used in places where the expected operating environment is corrosive or high temperature. There are three types of aluminum oxide PCB boards based on the purity of the aluminum oxide used. They are-

96% alumina PCB - it is the most popular among the three variants. Its small grain size helps maintain its high thermal conductivity, good chemical toughness, and structural integrity. It is popular because its usability and cost-effectiveness can be said to be the highest among the three variants. Its color is clearly white.

99% alumina PCBs - they have higher purity alumina ceramics. The grain size of 99% aluminum PCB is lower than that of 96% alumina, so most of its thermal and mechanical properties are much better than 96% alumina. It is not as widely used as the other two variants because it is more expensive than 96% alumina PCB and can be used with 99.5% alumina, which is a high-quality ceramic, for just a little extra money. 99% of aluminum PCB boards are light beige in color.

99.6 Aluminum Oxide PCB - It is the purest of the three PCB variants. Its grain size is the smallest, therefore its mechanical, chemical, and electrical properties are superior to the other two variants. It is the most expensive of the three variants, used for very specialized applications. 99.6% of aluminum oxide PCBs have a dense beige color.

Some characteristics of aluminum oxide PCB include:

Thermal stability - This PCB performs almost unchanged at extreme temperatures and can operate at temperatures as high as 300 ° C and as low as -55 ° C in a short period of time.

Thermal conductivity - Aluminum oxide has a very high thermal conductivity. Its thermal conductivity range is 18 to 30 W/mK, which varies depending on the batch and type of aluminum oxide PCB board used. In contrast, the thermal conductivity of ordinary FR4 used in most general-purpose PCBs is 0.25 W/mK, the thermal conductivity of expensive high-speed dielectric material Isola Tachyon 100G is 0.42 W/mK, and the thermal conductivity of ordinary metal core PCBs ranges from 1 W/mK to 9 W/mK

Water absorption rate - The water absorption rate of alumina PCB is 0%. The porosity of alumina is extremely low, making its surface impermeable, which also contributes to its corrosion resistance. In contrast, the water absorption rate of FR-4 is about 0.1% to 0.2%.

Mechanical strength - Aluminum oxide ceramic PCB has a compressive strength of 300 MPa to 450 MPa, similar to the forced strength of FR-4. For mechanical strength, 300 Mpa is an impressive number.

Density - The matrix is very dense. Their density ranges from 3.6 g/cm ³ to 3.9 g/cm ³ depending on the variant of aluminum PCB. In contrast, the density of FR-4 is 1.8 g/cm ³, which is about half of that of an alumina PCB board.

Chemical inertness - Aluminum oxide PCB boards can withstand a variety of solvents, whether alkaline, acidic, or organic. PCB is also less prone to corrosion over a long period of time.

Dielectric constant - The dielectric constant range of ceramic PCBs is 9 to 10, which is quite high. In contrast, the dielectric constant of FR4 is approximately 4 to 4.6, while the dielectric constant of Isola Tachyon 100G is 3.02. A high dielectric constant means that the electrical energy storage of the PCB substrate is higher.

Dissipation factor - The dissipation factor (Df) of aluminum oxide PCB ranges from 0.0001 to 0.001, depending on the type of aluminum oxide and the frequency of the signal. The dissipation factor of alumina PCB is extremely low and lower than most PCB substrate materials. In contrast, the dissipation factor of FR4 is 0.015 to 0.025, while the Df of Isola Tachyon 100G is 0.0025 to 0.0035.

Aluminum oxide PCB has many advantages, making it a popular choice in the industry. Some of the advantages include:

High thermal conductivity - Aluminum oxide PCB is one of the PCBs with the highest thermal conductivity among most PCBs. High thermal conductivity can achieve high and uniform heat dissipation. High power and LED PCBs require high thermal conductivity because PCBs generate high heat during operation.

High thermal stability - Aluminum oxide PCB has a low thermal expansion rate and can provide dimensional stability even at relatively high temperatures. High thermal stability also means reliable connection at different temperatures. If the PCB needs to operate in a high-temperature environment, it requires high thermal stability.

PCBs that support multi-layer and complex circuits - metal core PCBs and other hard substrates typically do not support multi-layer or complex circuits, or if used, may reduce the thermal performance of the PCB. On the other hand, aluminum oxide PCBs support multiple layers and can support complex circuits.

High corrosion resistance - Aluminum oxide PCB has strong corrosion and chemical resistance, with a water absorption rate of basically 0%. Its inertness makes it reliable and stable over a long period of time.

High dielectric constant - Aluminum oxide PCB has a high dielectric constant, which is necessary for high-power applications. If a separate layer is used as the power layer, the high dielectric constant PCB substrate can act as a decoupling capacitor, thereby reducing noise in the power network. High dielectric constant can also reduce crosstalk between adjacent traces.

Stability performance under extreme conditions - they are known for their ability to maintain mechanical and electrical performance even in extremely harsh environments.

Environmentally friendly - Aluminum oxide PCBs and even most ceramic PCBs are generally considered environmentally friendly. Aluminum oxide is an oxide of aluminum, non-toxic and harmless. After treatment, it will not cause too much pollution and can be recycled.

The cheapest among all ceramic PCB substrates - alumina PCB is the cheapest and most widely used ceramic PCB on the market.

The drawbacks of aluminum oxide PCBs are limited, and some of the limitations of these PCBs are-

Cost - Although aluminum PCB may be the cheapest ceramic material, it is much more expensive than FR-4 PCB.

The production difficulty is high - producing alumina printed circuit boards requires extremely high temperatures and additional special equipment to produce, which leads to high costs.

Limited production quantity - Aluminum oxide PCBs require aluminum oxide ceramics, which are not as common as specialized laminates such as FR-4 or Rodgers PCB substrates. The limited supply and manufacturing difficulties make large-scale production of ceramic PCBs quite challenging. This also limits the economies of scale of aluminum oxide PCBs.

Better availability of ceramic PCBs - Although aluminum oxide PCBs are the cheapest ceramic PCBs, their performance is not as good as other more expensive ceramic materials such as aluminum nitride. For example, the thermal conductivity of alumina is 30 W/mK, which seems high, while the thermal conductivity of ceramic PCBs made of aluminum nitride is about 170 W/mK

LED PCB - LED is a high heat generating component. The power consumption of each high-power LED ranges from 1 watt to 20 watts, generating a large amount of heat that needs to be dissipated, otherwise the overall lifespan and performance of the LED will decrease.

High power PCB - High power PCBs use aluminum oxide to process high-power AC and DC power supplies. High power applications require excellent heat dissipation, high dielectric insulation, and high operating temperatures. Aluminum oxide PCB is very common in inverters and AC main power switch boards.

Automotive PCB - Automotive PCB uses ceramic PCB because it is sturdy and reliable at high temperatures. The engine control unit and engine inspection sensor modules need to withstand high vibrations, high temperatures, and mechanical impacts while maintaining the highest reliability standards,

RF/Microwave Applications - Ceramic PCBs are widely used in microwave and radio wave applications due to their extremely low dissipation factor and excellent signal integrity characteristics. Some industrial wireless network devices also use ceramic PCBs.

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