Beryllium Oxide (BeO) Ceramic PCB

Beryllium oxide (BeO) ceramics, commonly known as beryllia ceramics, are a type of ceramic composed predominantly of exceptionally pure beryllium oxide, constituting up to 99% of its composition. Notably, beryllium oxide stands out as a premier ceramic thermal conductor, rivaling the conductivity of top-tier metallic materials. Its exceptional electrical isolation capabilities are on par with alumina, a renowned insulator. BeO ceramic PCB are particularly favored in cutting-edge high-power LED applications, thanks to their remarkable thermal conductivity exceeding 230W/Mk.

BeO ceramic PCB

When to Use BeO Ceramic PCB

BeO ceramics serve as a unique substrate and are generally considered excessive for typical applications. Consequently, it is not cost-effective to employ them in every PCB. It’s crucial to bear in mind that BeO ceramic PCB come at a higher cost compared to standard PCB, necessitating careful consideration to maintain reasonable production costs.

BeO Ceramic PCB becomes a preferred choice when electronic equipment is anticipated to operate in challenging environments prone to oxidation-induced corrosion. Being inert, BeO ceramics don’t react with air, ensuring prolonged durability in oxidizing conditions.

Here are key characteristics of BeO substrate:

  • Melting Point: 2530 to 2570°C
  • Density: 3.02g/cm3
  • Thermal Conductivity: 250 to 300 watts per meter-kelvin (W/mK)

Noteworthy hardness, rigidity, and resistance to mechanical stress, maintaining dimensional stability and reliability in the PCB structure.

For high-frequency electronics with ultra-fast signals, often in the hundreds of megahertz to gigahertz range, specialized substrates like Beryllium oxide are crucial to maintaining signal integrity and minimizing propagation losses.

As modern electronics trend towards miniaturization, there is a challenge for PCB designers. The common FR-4 PCB struggles with thermal management beyond certain dimensions, leading to the use of special substrates like BeO in smaller, high-density designs to uphold intended performance and efficient heat dissipation.

Beyond BeO, alternative ceramic substrates include:

  • Al2O3: Known as alumina, it is a robust material with exceptional electrical insulation characteristics. Common 96% alumina has a thermal conductivity of 25.0W/mK and CTE of 4.5 to 10.9/K.
  • AlN: A non-oxide semiconductor ceramic with excellent electrical resistivity and thermal conductivity (about 80 to 200W/mK). It is more expensive and is often used in high-current-carrying PCBs.
  • SiC: An advanced material with impressive strength and electrical insulation properties, both naturally occurring and synthetically produced.

BeO Ceramic PCB Manufacturing Process

In reality, regardless of the substrate material, several inherent PCB manufacturing processes play a crucial role, including circuit design, substrate cleaning, and layer stacking. When it comes to manufacturing BeO ceramic PCB, there are some distinctive aspects:

Firstly, BeO is a pure ceramic material, making it challenging to construct multilayers, similar to Al2O3 and AlN.

Secondly, for building the conductive layer, it’s recommended to utilize advanced techniques like screen printing or inkjet printing to evenly apply pastes containing metals such as silver, copper, or gold on the substrate’s surface.

Additionally, a key step in the process involves placing the substrate with the applied conductive material into a high-temperature furnace for heat treatment. This process, known as sintering, helps firmly fuse the conductive material onto the PCB, forming a robust structure.

Of course, BeO ceramics can also adhere to other ceramic PCB manufacturing technologies, which we’ll delve into next!

Other Manufacturing Technologies

LAM (Laser Activation Metallization)

LAM are produced using a high-energy laser to ionize both metal and ceramic materials. The process results in the growth of metal and BeO together, creating a robust bond with a smooth surface texture.

DPC (Direct Plate Copper)

DPC is an advanced coating technique involving trace printing and etching using a thin copper layer plated onto the BeO substrate. The bonding of copper to the substrate utilizes physical vapor deposition, vacuum, and sputtering techniques. The resulting copper thickness ranges from approximately 10um to 140um, providing a thin yet effective layer.

DBC (Direct Bonded Copper)

The direct copper bonding method introduces controlled amounts of oxygen between the copper and BeO before or during deposition. This technique yields thin copper coatings, ranging from 140um (4oz) to 350um (10oz). It is important to note that DBC may not be suitable for high current-carrying PCB.

LTCC (Low-Temperature Co-Fired Ceramics)

LTCC PCBs are created by combining ceramic substances, such as Beryllium oxide, with glass materials in ratios ranging from 30% to 50%. Organic binders are added for proper bonding. After spreading, flattening, and drying the mixture, through-holes and vias are drilled based on designer specifications. The screen printing method, using gold as the preferred conductor, is employed to create the circuit. The final step involves placing the circuit in an oven at temperatures between 850°C and 900°C.

HTCC (High-Temperature Co-Fired Ceramic)

HTCC differs from LTCC in baking temperature, as HTCC undergoes baking at a temperature between 1600°C and 1700°C in a gaseous atmosphere. Due to the high temperature involved, metals with high melting points, such as tungsten and molybdenum, are utilized to create the traces.

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