A ceramic PCB, also known as “ceramic hybrid circuit devices”, has become the industry’s new standard for electrical components. Although this technology was first introduced by ceramic capacitors, it is now used in many different applications.
The properties of ceramic materials used in the manufacturing process of ceramic circuit boards make them durable, reliable, and a great alternative to other electrical components. It is not the usual ceramic we can find as house decors, potteries, or flooring, as these ceramic boards are made of high-quality industrial materials with metal cores. They may also be called green boards, not because of the color, but because they use less toxic chemicals and have a smaller carbon footprint than their traditional counterparts.
You might then be wondering, are ceramic base material PCBs any good? What are the advantages of ceramic PCB material and its drawbacks? When should someone use a ceramic PCB? In this article, we will go through all of these questions and provide the answer. Read along as this also covers the materials used to make it to the different ceramic PCB types available today, how they are produced, and where to source and find ceramic PCB manufacturers.
What is a Ceramic PCB?
A ceramic printed circuit board is a type of PCB made of a ceramic material base or substrate, usually an inorganic dielectric, instead of the traditional fiberglass or epoxy resin base. It is an electronic circuit board made of a thin insulating layer of ceramic material with a metal component.
Basic Components of Ceramic PCBs
First is the highly integrated circuit board, which has become a trend that we cannot avoid with the advancement of electronic technology. Modern technology and electronics have hundreds or thousands, even millions, of transistors and resistors coupled in a complex assembly built on a small silicon chip or integrated circuit, widely known as IC.
These integrated circuits need a base where tiny electronic materials and connections are built, usually known as a substrate. It also needs a structure that isolates the circuit from its external surroundings and turns it into just one compact and solid unit, known as the package.
Substrates and packages are required for the integrated circuits to maintain their reliability. ICs need insulating materials, and these two serve that purpose. These packages will then be mounted on a printed circuit board.
Ceramics are well known for their insulating properties. This advanced ceramic material’s protection property is a significant factor for it to be used as substrates and packages. This is what makes a ceramic printed circuit board or PCB stands out from the rest of its kind.
Due to its excellent heat conductivity and gas tightness performance, ceramic PCB has been widely used in power electronics, hybrid microelectronics, electronics packaging, and multi-chip modules. Its excellent conductivity is of utmost importance in applications such as power generation, where large currents must be passed through the material.
The aerospace and automotive industries, in particular, are best suited to employ these PCBs since they have high-power-density circuit designs used in harsh environments.
High temperature, high pressure, as well as corrosive or vibratory circuit conditions, are all suited for ceramic PCB substrate material. They are used in high-temperature applications where a regular PCB cannot be used as it would not be able to withstand high temperatures.
What are the Materials Used in a Ceramic PCB?
A variety of ceramic materials are used to make ceramic PCBs. When choosing ceramic materials, the two essential characteristics to pay attention to are the PCB thermal conductivity and coefficient of thermal expansion (CTE).
Alumina or Aluminum Oxide (Al₂O₃), Aluminum nitride (AlN), beryllia or beryllium oxide (BeO), silicon carbide (SiC), and boron nitride (BN) are a few examples of the substrate materials that fall under the category of ceramic materials used in ceramic PCBs. These ceramic materials have comparable physical and chemical characteristics. Three of the most widely used materials in ceramic PCBs are the following.
Aluminum Oxide (Al₂O₃)
Aluminum Oxide is an inorganic compound, also known as alumina. It is an advanced material made of aluminum and oxygen. It usually appears white in color but varies depending on purity. The color can be pink to almost brown. This compound has no smell and comes in a crystalline powder form but does not dissolve in water.
Of all the oxide ceramics, alpha-phase alumina is the stiffest and strongest. With higher than 95% alumina content, it is an exceptional electrical insulator and has a high electrical resistivity of approximately 1 × 1014 Ω·cm. The common purity ranges from 94% to 99%. The desired color, solidity, size, and shape should be easily achieved. It is considered beneficial for engineering production since the composition can be altered.
This industrial oxide ceramic has outstanding thermal and corrosion stability, great mechanical and dielectric strength, and even the capacity to create airtight seals. The common, 96% alumina has a thermal conductivity property value of 25.0 W/(m·K) and CTE of 4.5 to 10.9 x 10-6/K. No wonder it is very popular, with all these benefits aside from its affordability and cost-effective price.
It is the most commonly used substance in ceramics as it has many applications in electronics, including substrates and packages. When the application does not require the maximum level of thermal performance, this is the go-to material in use. It is one of the most researched and thoroughly characterized advanced ceramic materials now available.
Aluminum Nitride (AIN)
Aluminum nitride (AIN) is a non-oxide, semiconductor technical grade ceramic material. The structure of this compound is a hexagonal crystal, and the color is blue-white in its pure form. The aluminum nitride, a synthetic ceramic compound, is commonly white or gray in color and may also sometimes appear as a pale yellow.
One of the best ceramic substrate materials available right now is aluminum nitride (AlN). Its electrical resistivity ranges from 10 to 12 10x Ω-m, and the thermal conductivity value is from 80 to 200 W/(m·K) that may even go up to 300 W/(m·K). With these features alone, without a doubt, it is the most attractive and one of the best options to use as a PCB substrate.
It has electrical insulation properties and a low coefficient of thermal expansion (CTE), 4 to 6×10-6K1 (between 20 and 1000°C), which is very close and resembles that of a silicon wafer. This compound has a lot higher values than alumina, but it certainly comes with a higher cost as well. It is best suited for use in high-current and high-temperature environments.
Beryllium Oxide (BeO)
Beryllium Oxide (BeO) or beryllia, which was also known, historically, as glucan or glucinium oxide. As the name suggests, it is derived from beryl or the mineral bromellite. It is a solid crystalline inorganic compound that appears white in color.
In addition to its great electrical insulating property, its thermal conductivity is higher than that of any other nonmetal [(209 to 330 W/(m·K)], with the diamond as the only exception, and it even surpasses that of some metals. Beryllium oxide has rigid bonds between its atoms, much like a diamond does. It transmits heat as vibrations across these strong bonds, and as a result, energy loss is minimal.
This refractory compound has a high melting point of 2506.85 °C to 2575 °C, a boiling point of 3905 °C, and a CTE of 7.4 to 8.9 x 10-6/K. Given these exceptional properties of beryllium oxide, it is a valuable resource in the electronics sector with its widespread applications. Even other industries benefit from it due to its high melting point, excellent heat conductivity, and good electrical resistance.
For over 60 years, beryllium oxide has demonstrated its outstanding chemical and thermal stability in challenging conditions and harsh environments. BeO is utilized to provide air or liquid cooling in applications where the PCB is exposed to high temperatures or in high-density PCBs with space constraints.
What are the types of ceramic PCBs?
There are different types of ceramic PCBs based on the manufacturing process. Below are the widely known and commonly used varieties that are currently available in the market.
Laser Activation Metallization PCB or LAM PCBs
The ceramic substance and the metal are ionized during the LAM process using a high-energy, powerful laser drill. They are growing together in the process, and as a result, it creates a bond or deep link. Then after, it achieves a better and smoother texture of the surface. LAM and DPC methods are getting more popular and being used these days.
Direct Plate Copper PCB or DPC PCB
This is an advanced coating technique, a new type of ceramic substrate processing where track printing and etching are carried out using thin copper, and it is plated to the ceramic substrate. The physical vapor deposition (PVD) method, a vacuum, and sputtering innovation are used to fabricate DPC to bond copper to substrates at high temperatures and pressures. The range of copper thickness with this process is 10 μm (≈ 1/3oz) to 140 μm (4oz).
Direct Bonded Copper PCB or DBC PCB
With the DBC method, an appropriate amount of oxygen is introduced between copper and ceramic before or during the deposition process. This is utilized when there is a need to have a high copper thickness of 140 μm (4oz)-350 μm (10oz).
Low-Temperature Co-fired Ceramic PCB or LTCC PCBs
For this type, manufacturing can be done with or without glass. The conventional method is that a ceramic substance is combined with glass material in amounts ranging from 30% to 50% to create LTCC PCBs. Organic binders are incorporated into the mixture to bond the materials properly. Once the mixture is spread out on sheets to dry, through-holes are drilled following the design layout of each layer. Screen printing is used to print the circuit and fill the holes. 850 and 900 °C are the temperature range to finish it in an oven. Traces on this method are usually gold.
High-Temperature Co-fired Ceramic PCB or HTCC PCBs
HTCC PCBs are built from the ground up utilizing raw ceramic substrate material. At no point in the production process that a glass material is added. The only distinction between the HTCC and LTCC production processes is that HTCC PCBs are baked at a temperature of roughly 1600–1700 °C in a gaseous atmosphere. HTCC PCBs have such high co-firing temperatures that circuit traces made of metals with high melting points, such as tungsten, molybdenum, or manganese, are employed. At high temperatures, these PCBs will function without any damage as they are designed to operate even in harsh environments.
Thick Film Ceramic PCB
This type of PCB is utilized when oxidation is a concern. That is why the material is baked up to 1000 degrees Celsius in a nitrogen atmosphere after coating the ceramic base with dielectric, gold, silver, or the widely used copper. Since it is prevented from oxidation, the electric capacitors, resistors, conductors, and semiconductors can all be interchanged on the ceramic board. Its conductor layer can be made from 10 up to 13 microns in thickness.
Ceramic PCBs Benefits and Drawbacks
Ceramic PCBs have been in use for a while now, and they have been getting a lot of feedback. There are advantages to this type of PCB, such as its being more durable than other types of PCBs. However, there are some drawbacks to ceramic PCBs as well. However, with the remarkable set of qualities ceramic PCBs have, the benefits might outweigh the disadvantages.
They are often recognized as the superior choice for various applications due to the many benefits offered by ceramic PCBs. It even has a lot of advantages over traditional FR-4 PCBs. The main benefit of ceramic PCB is that it is much more heat-resistant than traditional PCB. Below, we summarize some of the advantages ceramic PCBs have.
Advantages of Ceramic PCBs
High Thermal Conductivity – Depending on the material used (alumina to beryllia, as stated earlier), the values range from 25 to 330 W/(m·K). It is way beyond that of FR-4 PCB, more than 20x higher. With its ability to dispel heat, ceramic performs better and can prevent a device from being damaged by high temperatures.
Low Coefficient of Thermal Expansion (CTE) – It has solid and outstanding interatomic bonds, so it can withstand high temperatures and is still firm, stable, and steady even under changing temperatures.
Excellent Thermal Insulation – Ceramic is incredibly insulating; therefore, heat will be less likely to flow through the substrate, preserving the circuit board’s components from getting damaged or harmed.
Inorganic – Due to its inorganic materials, it can work and be of use for a longer period of time. Also, the chemical resistance to erosion is impressive.
Multi-Layering – A multi-layer ceramic PCB can do a more complicated task. With the toughness of its material, another layer can be added easily and still keep the other components safe. It is excellent for heavy-duty applications.
High Frequency – High frequency can be handled by a ceramic PCB with its dimensional and thermal stability. Industries requiring high-frequency data and electrical signal transmissions, such as the medical and aerospace sector, will surely benefit from this.
Cost Efficiency – It may not come cheap outright compared to FR-4, but with its improved performance and service life, it will surely last longer. With its simple design and reduced fabrication, the overall system cost is still lower than metal core PCBs.
Disadvantages of Ceramic PCBs
Ceramic printed circuit boards (PCBs) have a number of advantages over other types of PCBs. However, there are also some potential drawbacks that need to be considered and carefully looked at. Maybe, they can be better in the future.
Handling – Ceramics can be delicate and fragile; therefore, it requires more attention and special handling during assembly and testing.
Affordability – Ceramic is a reasonably priced material. However, with all things considered, it is still more expensive than other materials used to make a traditional circuit board. It is a bit more costly in that case as its production requires special equipment.
When is It Ideal to Use Ceramic PCB?
Ceramic PCBs can be used in many applications but are not the best solution for all. With all factors considered, they may not be appropriate in all cases.
It is essential to understand the factors that determine whether a ceramic PCB is a right choice for your project or application. Some factors to consider when deciding whether or not to use ceramic PCBs are their cost, weight, and thermal conductivity.
They are resistant to corrosion, have a low thermal expansion, and can be manufactured with very thin layers and high aspect ratios. Hence, they are much lighter and have better thermal conductivity, making them ideal for applications where size, weight, and heat transfer are of vital concern.
When there is a need for multi-layer boards, their high thermal conductivity property will be in significant play. The inner circuit layer/s and the surface will be spared from hot spots. This makes them ideal for use in applications where high temperatures are a concern, such as automotive or aerospace. Switching to ceramic PCBs may greatly improve machinery’s reliability, specifically those used in the military and heavy equipment industrial sectors.
In general, ceramic PCBs may be more expensive than traditional PCBs. Taking the cost into consideration, it offers several benefits that make them an excellent choice for selected applications.