Given the rise in variations to PCB designs and the need to introduce new materials to the fold; it becomes imperative to use the right substrates. Also called PCB materials, these substrates help one to optimize the circuit board accordingly. Alumina substrate is one of the most-popular.
In this article, you will learn what an alumina substrate PCB is.
The Meaning of Alumina Substrate?
Alumina is one of the different substrates used in Printed Circuit Board (PCB) production. It is also a type of ceramic substrate, hence, the naming as alumina ceramic substrate.
Alumina (AI203) substrate has become one of the most-used circuit board materials because of the excellent breaking strength, the improved heat and insulation properties and the thermal conductivity.
It is also worth noting that this substrate is the favorite for manufacturing circuit boards that have a need for good mechanical and chemical resistances.
The Properties of Alumina Ceramic Substrates
The properties cut across the principal requirements for making reliable circuit boards. These include thermal conductivity and heat insulation.
Here is a list of some of the most-important properties of the alumina material:
1. Excellent Mechanical Strength
The mechanical strength is based on the substrates ability to provide resistance and durability to the shocks, mechanical stress and vibrations.
2. Improved Thermal Conductivity
The ability of a PCB substrate to conduct heat effectively is also one of the major factors worth considering when deciding on the one to go for. In this regard, the alumina substrate has an improved thermal conductivity, which aids in an excellent dissipation of heat in electronic device.
The good thermal conductivity also reduces the chances of overheating in these devices. This way, it helps to prolong the electronic components’ lifespan, while maintaining the optimal performance of the same.
3. Good Electric Insulation
Just as the substrate helps to dissipate heat, it also helps to insulate the devices. As such, the good electric insulation properties help in isolating or creation a division between the several circuit board elements.
By this, the electric insulation capabilities help in the provision of safe and reliable operation, as well as the prevention of short-circuiting.
4. Good Smoothness
The material provides a combination of good smoothness and less porosity – a feature that supports an excellent adhesion with both thick film and thin film materials.
5. Stable Breaking Strength
Alumina ceramic substrate has a very stable breaking strength, as well as less variances in the dimensions and shapes.
The following are some of the additional properties of an alumina substrate:
- Smooth surface and small warpage
- Corrosion resistance
- Excellent fire resistance properties
- High-light reflection
- Small dielectric loss and;
- Stable physical and chemical properties.
- Very low adherence
- Excellent dimensional stability, even in higher temperatures.
- Resistance to oil and chemical products.
- Higher resistance to wear and corrosion.
- Lesser variances in the slit pitch, outline and plate thickness.
Types of Alumina Substrates
You will find two (2) different types of alumina substrates in use. These are the Sintered High-Density Alumina and the Sintered Porous Alumina.
Before we go into the differences, let us quickly point out that alumina is the main composition of the alumina substrate.
1. Sintered High-Density Alumina
This type of alumina ceramic substrate has the alumina content ranging between 96% and 99.6%. It also has the substrate readily available in two (2) products.
For this type of alumina substrate, you will find it available in different thicknesses, such as:
- 0.15 to 0.25
- 0.38 – 0.5
- 0.75 to 1
- 1.27 to 1.52 and;
- 2 mm.
For the dimension, you will have the Sintered High-Density Alumina Substrate can be found in different options, including:
- 50.8 x 50.8 mm and;
- 168 x 168 mm.
The features include:
- Good thermal conduction.
- Usable as electrical insulators.
- Higher resistances to abrasion and corrosion.
- Exceptional flatness and;
- Low adherence.
2. Sintered Porous Alumina Substrate
This is the second type of alumina substrate. The Sintered Porous Alumina Substrate is lighter than the former (Sintered High-Density Alumina Substrate); even though it shares similar properties – chemical, mechanical and electrical.
The Sintered Porous Alumina Substrate thickness includes:
- 1 to 1.5 mm and;
- 2 mm
You will also find this material available in different dimensions, such as 100 by 100 mm and 168 by 168 mm.
The major attribute of this substrate is the porosity, which supports the following:
- Homogenous diffusion of a fluid.
- Filtration of liquids and gases.
Benefits of Alumina Substrate PCBs
Several advantages can be derived from using this type of substrate in your PCB. From improving heat conduction and making the electronic components less susceptible to fire; alumina substrate can be very beneficial.
We have explained in details below, some of the benefits of using alumina substrate in your circuit board.
a. Extended Lifespan
The heat conduction properties readily come in handy for the extension of the electronic applications’ lifespan. By reducing the heat trapped within the devices and components; it makes it possible for these to be used for a long time to come.
b. Efficient Thermal Management
Thermal energy or heat can be a militating factor to the performance of an electronic device. For context, excessive heat is generated by the electronic components, as the device or application operates. By doing so, the heat continues to accumulate and might go beyond the recommended temperature.
Hence, the thermal management in the alumina substrate, which is up to 30 W/m.K, makes it possible for the substrate to facilitate faster heat dissipation from the system.
c. Reliable Performance
Alumina ceramic substrate’s good electrical insulation properties makes the performance reliable. The durability that this offer is the reason why the material is highly-recommended for the applications that require stability.
d. Higher Temperature Resistance
With a higher resistance to temperatures, alumina substrate makes a good fit for the electronic devices that are used in high-temperature environments. Also, this makes the material ideal for the environments where the performance of electronic devices does not need to be compromised.
Applications of Alumina Substrates
You can use these materials in both electronic devices and applications that require optimum performance and reliability. The following are some of the typical applications:
a. LED Devices
Alumina materials are used in the Light Emitting Diode (LED) market, where they are used to improve the reliability and heat conduction of these applications.
Besides, these substrates are effective in the faster dissipation of heat and excess thermal energy generated by the LEDs. This results in improved performances and lifespan.
b. Printed Circuit Boards (PCBs)
Circuit boards are one of the use cases for the alumina substrate. The usages here range from providing stability and reliability to the electronic components, and the provision of a reliable platform for the creation of complex PCBs and mounting of the electronic components.
c. Power Electronic Devices
The alumina substrates can also be used for the power-related electronic devices. Examples are:
- Inverters
- Power modules
These materials are useful in these regards because of the excellent electrical insulation and thermal conductivity properties.
Besides these three, the alumina substrates can also be used in the following applications:
- Filtration of liquids
- Sintering equipment
- Catalyser
- Chip resistors
- FAX substrates are used for the thermal printer heads.
- Oven construction elements
- Electronic sensors and;
- Medical technology/devices.
Stages of Manufacturing Alumina Substrates
Different steps are used when producing alumina substrate. The robust and high-quality manufacturing processes include:
a. Raw Material Selection
The raw material will be selected first and the major concentrations are on the particle size distribution of the powder and the purity. By choosing a high-quality alumina powder, you are sure of getting a high-quality substrate in return.
The best raw materials to use are aluminum oxide powder, and aluminum hydroxide. Any of the two can provide you with the desired consistency and composition, provided the mixing and blending process is accurate.
b. Powder Preparation
You can also prepare the powder, by using any of the following options:
- Washing
- Grinding
- Filtering and;
- Mixing.
Note that this preparation method is utilized to control the purity, size and shape of the powder.
c. Forming Methods
These processes include the mixture of the powder to form a green sheet. Extrusion and tape casting are some of the techniques used for this purpose. Following the mixture, the green sheets would then be cut into the desired size and shape.
This method is also called molding and has to do with the shaping of the powder into the desired substrates. The techniques or processes used in the molding stage include but are not limited to:
- Compression molding
- Injection molding
- Extrusion molding
d. Sintering Process
This is also called the firing process. At this stage of alumina substrate production, we are looking at the sintering and densifying of the material.
Have in mind that the sintering process is used because the molded substrate doesn’t have the desired reliability. Hence, it is subjected to a high-temperature sintering process during which the particles are fused together and made to have the desired reliability.
The outcome is usually a molded substrate with a dense footprint, crystal structure, having the required mechanical strength, possessing the best electrical properties and having an optimal density.
Final Thoughts
Alumina ceramic substrates make PCBs and other applications, such as LEDs highly-reliable, usable across different applications and having a prolonged usage.
