What is AMB Ceramic PCB?

What AMB Ceramic Substrate PCB is?

Active Metal Brazing (AMB) process is a further development of DBC technology. It uses a small amount of active elements such as Ti, Zr, Cr in the filler metal to react with the ceramic to form a reaction layer that can be wetted by the liquid filler metal, so as to bond the ceramic substrate with metal layer. AMB substrate is based on the chemical reaction of ceramic and active metal at high temperature to achieve the combination, so it has higher bonding strength and better reliability. The active metal layer also provides a metallization layer for the ceramic substrate, which can significantly reduce the processing time and cost of the PCB.

The structure of AMB ceramic PCB is showing as following:

Manufacturing Process of AMB Ceramic PCB

Different with other ceramic substrate manufacturing, the AMB has extra processes of printing active metal and brazing, so it is relative complex and need to use expensive manufacturing equipment to finish the whole process. In the PCB market, the silicone-nitride PCBs are usually to make by AMB technology, here we summarized general steps involved in the manufacturing process of AMB ceramic PCBs:

1. Active solder is silk screen printed on the ceramic substrate under the N₂ atmosphere at about 800℃. Generally, the metal of the active solder is Ag/Cu mixed with Ti and Zr. Ti, Zr and ceramic will form a reaction layer wettable by the solder.

2. Clamping ceramic substrate with oxygen-free copper clad and soldered in a vacuum brazing furnace. Please be make sure the ceramic and metal substrates are aligned proper in this step.

3. Etching circuit on the copper layer.

4. Electroless copper plating to conduct the circuit pattern.

5. If the PCB is multilayer, layers are laminated. (Alternative)

6. Finally, a solder mask is added to protect the circuit. (Alternative)

7. Perform E-test, visual test, dimension measurement to make sure the good quality of the ceramic substrate.

The AMB process allows for the creation of ceramic PCBs with high thermal conductivity, excellent electrical insulation, and strong bonding between the ceramic and metal substrates, making them ideal for use in high-power and electronic vehicles.

Features of Active Metal Braze Ceramic PCB

1. Higher thermal conductivity

The thermal conductivity of ceramic substrates is much higher than that of traditional organic substrates, which makes AMB ceramic PCBs suitable for high-power applications that require efficient heat dissipation.

2. Higher bonding strength

Due to the AMB ceramic PCB is based on the reaction of ceramic and active elements at high temperature, which makes it has higher bonding strength than other types of ceramics.

3. Higher reliability

The active metal brazing process forms a strong and stable bond between the ceramic substrate and the metal layers, which can significantly improve the reliability of the PCB.

4. Excellent electrical properties

Ceramic substrates have low dielectric constant and loss, which can minimize signal loss and interference in high-frequency applications.

5. Cost-effective

The active metal layer provides a metallization layer for the ceramic substrate, which can reduce the processing time and cost of the PCB. (But in anther way, the AMB manufacturing needs an expensive equipment.)

Not everything is perfect, AMB ceramic also has its drawbacks.

A: Brittle/fragile: Ceramic substrates are more brittle than traditional organic substrates, which may increase the risk of cracking or breaking during manufacturing or assembly, so be carefully when assemble or in transition.

B: Limited flexibility: Ceramic substrates have limited flexibility, which may limit the design options of the PCB.

Applications of Active Metal Braze Ceramic PCB

AMB ceramic PCBs are widely used in high-power and high-reliability applications, such as power electronics, aerospace, and military applications. In power electronics, AMB ceramic PCBs are generally used in high-power inverters, motor drives, and power supplies, where high thermal conductivity and reliability are essential. In aerospace and military applications, AMB ceramic PCBs are used in avionics, radars, and communication systems, where high reliability and harsh environment resistance are required. 

Comparison with Other Types of Ceramic PCBs

DBC ceramic PCBs use a direct bonding process to join the ceramic substrate and the copper layers. They have high thermal conductivity and good reliability, but they are expensive and have limited flexibility.

DPC ceramic circuit has a thinner copper layer than AMB PCB, so its bonding strength is not as good as AMB. (AMB has more than 18n/mm-21n/mm while DPC only has 8-15n/mm).

LTCC PCBs use a co-firing process to join the ceramic layers and the metal layers. LTCC PCBs have good electrical properties and flexibility, but their thermal conductivity is lower than that of DBC and AMB ceramic PCBs.

HTCC ceramics use a co-firing process at a high temperature to join the ceramic layers and the metal layers. HTCC PCBs have high thermal conductivity and reliability, but they are expensive and have limited flexibility.

Thick film ceramic PCBs use a screen-printing process to apply conductive and resistive pastes on the ceramic substrate. Thick film ceramic PCBs have low cost and high flexibility, but their electrical and thermal properties are lower than those of DBC, LTCC, HTCC, and AMB ceramic PCBs.

Capability of AMB Ceramic Substrate PCB

Compared to other types of ceramic PCBs, AMB ceramic PCBs have unique properties and advantages, but they also have some limitations, such as brittleness and limited flexibility. So choosing a right technology for your project also is important. If you don’t know which one is the best, welcome to contact us, BSTCeramicPCB provides free consulting and technical support for you.