Fabrication Processes Of DCB Ceramic Substrate PCB

DBC (Direct Bonded Copper) ceramic PCBs (Printed Circuit Boards) are a type of circuit board that uses a ceramic substrate and copper foil to create a high-performance electronic component. The important difference between DBC and DPC ceramic PCBs is the thickness of the copper layer. In DBC PCBs, the copper layer is typically thicker, ranging from 35 to 200 microns or more. This thicker layer provides better conductivity and improved mechanical strength, making DBC PCBs more suitable for high-power applications. In contrast, the copper layer in DPC PCBs is typically thinner, ranging from 10 to 35 microns or less. This thinner layer reduces the overall cost of the PCB, making it a better choice for low-power applications.

The manufacturing process of DBC ceramic PCBs involves several steps, which are outlined below:

1. Ceramic substrate preparation:

The first step in the process is the preparation of the ceramic substrate. The substrate is typically made from aluminum oxide (Al2O3) or aluminum nitride (ALN), which are materials with high thermal conductivity and excellent electrical insulation properties. In general, the substrate is a big sheet, so we need to cut it to the desired size and shape using a laser cutting machine. Due to the ceramic substrate being fragile and easy to be broken, a laser cutting machine is the ideal way to cut.

2. Copper foil preparation:

This step is also known as deposition of copper foil. which involves the preparation of the copper foil. The copper foil is typically a thin layer of copper (usually less than 10um) that is laminated onto the ceramic substrate by various techniques such as electroless plating, sputtering, or evaporation. The thin layer of copper serves as a bonding layer for the thick copper layer that will be applied in the next step.

3. Bonding:

In this step, the copper foil is bonded to the ceramic substrate using a high-temperature bonding process. The bonding process involves placing the copper-polyimide composite on top of the ceramic substrate and then heating them together in a furnace at a high temperature, typically around 1000-1100°C. The high temperature causes the polyimide film to decompose and evaporate, leaving only the copper layer in direct contact with the ceramic substrate. The high temperature also causes the copper and ceramic to form a strong bond through a diffusion process, where atoms from each material intermix at the interface. The copper thickness after bonding can be 100-200um, 300um also is available. So if your ceramic project needs copper thickness over 200um, the DBC technology is the best choice for your choosing.

4. Etching:

After the bonding process, the excess copper will be etched away from the foil using a chemical etching process. This process involves applying a layer of photoresist material on top of the copper layer, exposing it to UV light through a photomask to create a pattern, and then immersing the PCB in an etchant solution that dissolves the exposed copper, the same as DES process of normal FR4 PCB. The photoresist material acts as a barrier, protecting the unexposed copper from the etchant solution. This leaves only the desired copper traces and pads on the ceramic substrate.

5. Drilling:

Then holes are drilled in the substrate according to the requirements to create the necessary vias and through-holes for top and bottom side connecting or component mounting. The holes are drilled using a laser drilling machine, which uses a high-speed rotating drill bit to remove material from the substrate and can ensure the holes quality as well.

6. Solder mask and Surface finishing:

Similar to FR4 PCB or metal core PCB, surface treatment is the necessary step to protect the surface. The process is to clean the ceramic circuit board carefully and then coat it with a layer of solder mask to protect the copper traces and pads. The solder mask layer is typically made from a heat-curable polymer material and is applied using a screen-printing process (usually, the solder mask for ceramic PCB is a greenish glass glaze. Once the solder mask is applied, it is cured using a UV light, which hardens the polymer and makes it resistant to damage. Finally, coating with a layer of gold or silver provides a protective layer and improves electrical conductivity of the ceramic PCB. The surface finishings for ceramic PCB are generally ENIG, ENEPIG (best for wire/alumina bonding), Nickel plating and OSP.

7. De-panel / Separate:

Once the QC inspection the quality of the product, we can proceed with the last process - depanelization. In order to improve production efficiency and maximization of material utilization, manufacturers prefer to fabricate ceramic PCB in panels. Due to the fragility of the ceramic PCB, BSTCeramicPCB always help to separate the panels into single piece before package and shipment.

Overall, the manufacturing process for DBC ceramic PCBs is complex and requires specialized equipment and expertise. The resulting PCBs offer excellent thermal conductivity and can be used in high-power applications that require efficient heat dissipation.

Properties of DBC ceramic PCB:

At our facility, we use state-of-the-art equipment and processes to ensure that our DBC ceramic PCBs are of the highest quality and reliability. We also offer customization options to meet the unique needs of each customer. Contact us today to learn more about our DBC ceramic PCB manufacturing process and how we can help you with your next project.