Ceramic PCB(s) are the printed circuit boards which are manufactured with ceramic (Al2O3, AlN, SiN) substrates by the means of Direct Plated Copper (DPC), Direct Bonded Copper (DBC) and Active Metal Brazing (AMB) technologies.
Ceramic PCB
With recent advances in the market, Ceramic PCBs have become a move viable option for PCB designer. With the continuing requirements for miniaturization, microelectronics and high-power packages, the need for substrates capable of withstanding high operating temperature, whilst offering outstanding thermal performance is a must. Semiconductors from materials such as Silicon Carbide (SiC) and Gallium Nitride (GaN) operate at high temperatures meaning associated circuits need to be ceramic. Ceramic interposers are also becoming popular for thermal management and when a hermetic package is required where no moisture can be tolerated and no outgassing materials can be used.
Ceramics are also used for high frequency applications due to low signal loss and as well as resisting UV they are chemical resistant, have no outgassing and are completely water resistant.
Ceramics have been widely used in electronics/electronic components for years due to their thermal, and mechanical advantages. With recent advances in technology and manufacturing capabilities, they are now replacing entire PCBs.
Since their introduction, Ceramic PCBs have received enormous attention from the industry as an effective solution to a range of electronic issues. The superior Thermal Conductivity of ceramics with low signal loss for high frequency being the leading reasons that more and more industries are turning to ceramics for their PCB design.
Heat dissipation is the key advantage that ceramics has over more conventional materials such as FR4 and metal core PCBs. With components being placed directly on the boards, and no isolation layer, the flow of heat through the boards is far more efficient. Depending on the material chosen, the Thermal Conductivity values range from 24-80W/m·K.
In addition to this, Ceramic material can withstand high operating temperatures (over 800°C) and has a very low CTE, allowing for additional compatibility options for PCB design.
DPC is recent development inn the field of Ceramic Substrate PCBs and was the breakthrough that made ceramics much more viable to designers. DPC involves vacuum sputtering under high temperature and pressure conditions to plate the copper to the substrate. The addition of a thin film titanium (Ti) layer acts as a bonding interface between the copper and ceramic layers. During this part of the process a very thin layer of copper is deposited coating the Ceramic substrate and it is also deposited in any pre-drilled holes. The circuit is then formed with etching. The thin copper allows very fine traces and reduced undercutting. Panels are then plated up to the required end copper thickness ranging from 10μm (≈1/3oz) to 140μm (4oz). DPC enables the circuit to incorporate plated or filled vias. Normal PTH methods do not produce reliable results on ceramics and therefore DPC must be used if a double-sided PTH ceramic board is required.
With DBC the copper is bonded to the Ceramic substrates on one or both sides using a high-temperature oxidation process. It offers options of heavy copper thickness -140μm (4oz)-350μm (10oz). The copper and substrate are heated in an atmosphere of nitrogen containing about 30ppm of oxygen; under these conditions, a copper-oxygen eutectic forms which bonds successfully both to copper and the oxides used as substrates. With DBC the copper layers can then be etched using standard PCB technology to form required circuit. Conventional PTH processing is not suitable for ceramics and therefore only DPC is used for through hole plating.
Reminder: MADPCB now not offers Direct Bond Copper (DBC) ceramic printed circuit boards (PCBs), but offers with DPC process.
Due to the Oxidization bonding process, there can be a slight reduction in Thermal Conductivity created by a void between the Copper and Ceramic layers.
Main applications are high power modules, like IGBT, CPV, or any other wide bandgap device modules.
AMB is the latest development in ceramic substrates. Unlike DBC Active Metal Brazing forms the substrates without metallization. Under a high temperature vacuum the copper is joined (brazed) direct to the ceramic base. This offers a high reliability substrate with unique heat dissipation. The brazing technology also enables copper weights of up to 800μm on thin ceramic substrates. These Heavy Coper materials make AMB ideal for Power Electronics.
Various copper weights are available to meet match substrate thicknesses detailed in the table below. It is recommended the copper thickness on any design is no more than half the ceramic thickness.
Double sided substrates offer greater mechanical strength and stability enabling Heavy Copper to be offered on thin ceramic substrates. The following is a guide on double sided material availability although during the etching process original copper weights can be reduced.
Note: Through hole plating is not possible with AMB or DBC substrates.
The most common material used for Ceramic PCBs is Al 2 O 3 Alumina PCB (96%). A naturally excellent electrical insulator with strong thermal properties. The thermal conductivity of Alumina is not as high as Aluminum Nitride (AlN), however, it is still noticeably higher than the best performing Metal Core PCB (MCPCB) materials with a Thermal Conductivity in the region of 24W/m·K. Another variant of this is Al 2 O 3 (99.6%) which has a higher Thermal Conductivity, in the region of 29W/m·K.
A high light reflectivity, along with good thermal properties makes Alumina Oxide well suited for LED applications.
