Guide

Ceramic PCBs: Materials, Advantages, Applications and Design Considerations

PCBs are at the heart of our everyday electronics, but not all PCBS have excellent heat dissipation capabilities. LED PCBs, high-voltage PCBs, and some high-power PCBs all need to use PCBs with strong heat dissipation capacity. Ceramic PCBs are widely used because of their excellent heat dissipation ability.

What Are Ceramic PCBs?

Ceramic PCBs are printed circuit boards produced from materials with ceramic in them. Ceramic PCBs are used in applications that require Low CTE (Coefficient of Thermal Expansion) and circuits that require high thermal conductivity. In Ceramic Printed Circuit Boards, the ceramic substrate PCB material is not made up of FR-4 standard PCB material but various types of ceramic substrates. The widely used ceramic substrate PCB materials which are oriented to application-specific are Alumina (Al2O3), Aluminium Nitride (AlN), Beryllium Oxide (BeO), Boron Nitride (BN), and Silicon Carbide (SiC). The Ceramic PCB boards are used as the insulators for IC substrates.

Ceramic Material Types and Their Properties

Ceramic Printed Circuit Board

Ceramic PCBs can be classified into various types based on the substrate, stack up, and thickness. Ceramic PCB board materials can be of single layer or multi-layer based on the number of layers; Thick film, thin film, or hybrid ceramic type based on the stack up and thickness. The broader classification of ceramic PCB board is based on the ceramic substrate material types which are layer and stack-up dependent as mentioned above.

Alumina / Aluminium Oxide (Al2O3): The most commonly used ceramic type of material is Aluminium Oxide as it is thermally stable and meets industrial-grade stability. These substrate materials are also used for LED lighting techniques and in automotive environments. The coefficient of thermal expansion (CTE) of the material is lower yet it is a little fragile, so environments do not prefer Alumina substrate PCBs. The cost of the ceramic substrate PCB material is cheaper as the materials are available and easy to fabricate.

Aluminium Nitride (AlN): Aluminium Nitride PCBs offer higher thermal dissipation than Aluminium oxide PCBs. This is used where thermal dissipation is more than mechanical stability. Industrial applications that use inverters or other switch mode power supply circuits use Aluminium Nitride PCBs.

Beryllium Oxide (BeO): Beryllium oxide possesses better thermal conductivity than aluminium nitride and better electrical isolation than other ceramic substrate PCB materials. Applications that use high-current devices and microwave products use Beryllium oxide as PCB substrate material. The manufacturing process of Beryllium oxide is high as the material is toxic and difficult to process the material.

Silicon Carbide (SiC): High-frequency applications and high thermal dissipation products use SiC as the substrate material for the PCBs. Silicon carbide plays a major role in extreme conditions like aerospace, automotive, and medical applications. Silicon carbide PCBs can handle more mechanical stress than other ceramic PCB board materials. Power electronics applications use SiC’s for stabilized high voltage and isolation circuits in drive trains, and industrial and renewable energy.

Hybrid Ceramic: Substrates consisting of metal cores along with ceramic PCB board materials to achieve the performance for specific applications.

The construction of the Ceramic PCB stack-up is shown in the below image.

Construction of the Ceramic PCB Stack-up

Properties of Ceramic PCBs

  • Thermal Conductivity: FR4 PCBs cannot handle more thermal conductivity and dissipate heat. Dissipating thermals will increase the efficiency of the circuit enhancing the performance and reliability. If the thermal conductivity of a ceramic substrate PCB material is good then the electrical property of the ceramic substrate PCB material is also good and this concludes that Ceramic circuit board materials can be used for PCB substrates as ceramics are bad conductors of electricity.
  • Dielectric Constant Dk: The dielectric cost of ceramic circuit boards varies a lot concerning materials. Higher dielectric constant values assist in designing high-frequency circuits. The resonant noise is reduced by reducing the internal signal reflections. The mechanical dimensions of these circuits can be smaller as the signal wavelengths are shorter and Dk is larger.
  • Coefficient of Thermal Expansion & Temperature Resistance: The CTE of the ceramic circuit boards is lower than standard FR4 substrates which are usually made up of reinforced laminates. Higher thermal resistance provides higher performance of the circuit as ceramic circuit boards can withstand up to 350 degrees Celsius or more, whereas FR4 can handle only up to 170 degrees Celcius.
  • Durability & Reliability: The durability of Ceramic-type substrate PCBs is higher than standard FR4 and the material rigidness is greater. Ceramic circuit boards are designed to withstand rigorous environments for automotive and aviation applications. These properties ensure the performance of the PCBs is reliable and the life cycle of the ceramic printed circuit board is longer.

Advantages of Ceramic PCBs

Ceramic PCB Board

Ceramic printed circuit boards have many advantages to adapt to high-speed signal and high-power applications to meet the required performance without compromising on efficiency.

  • Ceramic Printed circuit boards have better thermal conductivity and also retain the same performance at higher temperature
  • The coefficient of thermal expansion (CTE) is much less when compared to other substrate materials.
  • Electrical isolations are better in ceramic than other PCBs as the dielectric constant (Dk) is greater and has a wide range.
  • It’s easy to handle and the production cost of the entire product is lower when compared to other systems with heatsinks and special components on the Printed circuit board.
  • The mechanical rigidity of the PCB is greater as it can operate in high-vibration environments like the automotive and aviation industries.
  • Ceramic substrate types are more resistant to corrosion to chemical compounds which makes them adaptable for industrial, medical, automotive, and aerospace applications.
  • The size of the Ceramic PCBs can be reduced and made in compact form factor as the PCB also can aid in thermal dissipation.
  • Low tangent is the major advantage in Ceramic Printed circuit boards because of its high dielectric constant leading to better signal integrity at high frequencies. This will be adaptable for high-speed signal designs in telecommunication and Wireless sensor networks.
  • The electrical properties of ceramic PCBs make them better in Electromagnetic interference and compatibility areas as the PCB can act as a shield by isolating the layers.
  • Ceramic circuit boards can be customised to make complex designs in mechanical and electrical aspects because of their flexibility and robustness. So multilayer ceramic PCBs are widely used.
  • The cost of ceramic PCB materials, manufacturing, and assembly is higher yet the life cycle and longevity are longer. The risk of failure is lower and the life span factor is more reliable.

Applications of Ceramic PCBs

Ceramic Circuit Board

  • Telecommunication: Ceramic PCBs are best suited for telecommunication purposes like antennae, and filters as the losses on the PCB are low when operating at high frequency.
  • Automotive: High current and high voltage applications can be designed easily with the Ceramic PCBs which provide more electrical isolation and high current carrying capability is also achieved.
  • Lighting Solutions: High-power LED lighting for high-brightness applications dissipates more heat, ceramic circuit boards are designed to dissipate high heat and are thermally stable. This increases the life span of these PCBs.
  • Medical Equipment: Medical applications use high-level standards for high frequency and high-performance applications like MRI scanners, X-ray machines, Ophthalmic lens makes, and surgical arms.
  • Aerospace: Avionics and aerospace industries require PCBs that can perform at high efficiency, at higher temperatures and vibrations for which ceramic circuit boards are used due to their robust and reliable properties. Because this kind of PCB circuit is complicated,  multilayer ceramic PCBs are needed in this situation.
  • Industrial: Industrial machinery that operates furnaces for heaters, high-power machines operating at higher temperatures, the performance of these machines is met using ceramic PCBs.
  • Renewable Energy: Renewable energy sources use inverters to convert and store energy. These machines work in harsh environments and the lifecycle of these machines has to be kept more than other commercial equipment’s.

Design Considerations for Ceramic PCBs

Ceramic PCBs require certain attention while designing for various material properties and design considerations are set as follows:

  • Material properties play a vital role; therefore, the materials are carefully chosen based on the application demands.
  • Thermal dissipation is the second factor that has to be considered as ceramic PCB design is opted for meeting higher thermal management. Various mechanical and electrical properties of the heatsink, vias, plane, and component footprint are considered before design.
  • Layer stacking is important as the signal integrity and performance of the PCB are dependent, on the thickness of the PCB, and the layer’s thickness impacts the inductance across the layer.
  • Copper is the standard conductor material used but in specific applications conducting layers are designed using gold, silver, or copper based on the current carrying requirements.
  • Most of the PCBs work through holes via plated or plugged-in technology, in certain conditions buried, blind, or micro vias are used.
  • Surface finishes like ENIG, Immersion silver, Tin, and OSP of the Ceramic printed circuit board depend on the solderability, thermal management, and mechanical resistance to the environment.
  • The design of ceramic PCBs also depends on the manufacturing capability of a particular vendor, hence the DFM (Design for Manufacturing) rules are set according to these parameters.
  • Ceramic printed circuit boards are designed for High-frequency and high-power PCBs which need to follow the guidelines to avoid cross-talk, impedance mismatch, and signal integrity issues.

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