Keywords: Ceramic substrate   

Alumina (Al2O3) or aluminum nitride (AlN) Ceramic substrate are unique process boards where the copper foil is directly bonded to the surface (single side or double side) at high temperature. The ultra-thin composite substrate offers superior electrical insulating performance, high thermal conductivity, outstanding soft solder ability, and high adhesion strength when compared to conventional FR-4 or aluminum substrate. It can also be etched with various graphics, such as PCBs, and has a high current carrying capacity. It is appropriate for items that generate a lot of heat (such as high-brightness LEDs and solar energy), and because of its exceptional weather resistance, it is more appropriate for tough outdoor conditions. 

What kinds of ceramic substrates are there?

As per Materials: 

Al2O3

Alumina is now the most widely used substrate material in the electronics industry due to its mechanical, thermal, and electrical qualities compared to the majority of other oxide ceramics, as well as its abundance of raw materials and high strength and chemical stability. It may be made in a variety of forms and technological configurations. 

BeO

It is utilized in applications that need high thermal conductivity since it has a greater thermal conductivity than metal aluminum, although the temperature quickly declines after 300 °C. The main factor limiting its development is that it is poisonous.

AlN

AlN has two extremely significant characteristics that are worth mentioning: first, it has a high thermal conductivity, and second, it has an expansion coefficient that is comparable to Si. The drawback is that the thermal conductivity will be impacted even if there is a very thin oxide coating on the surface. We can only create an AlN substrate with good consistency by carefully monitoring the components and procedures. AlN's pricing is now quite costly when compared to AI2O3, which is also a minor roadblock to its development. However, this barrier will gradually dissolve as the economy grows and technology advances.

Because of their exceptional all-around performance and widespread application, alumina ceramics continue to have a leading position in the disciplines of microelectronics, power electronics, hybrid microelectronics, and power modules. 

As per the manufacturing process

HTCC (High-Temperature Co-fired Ceramic)

High-temperature co-fired multilayer ceramic, or HTCC, is another name for it. The production procedure is pretty comparable to LTCC. The primary distinction is that glass materials do not include HTCC's ceramic powder. Therefore, a high temperature of 1300–1600 °C is required for the drying and hardening of HTCC. There are just a few options available for metal conductor materials because of the high co-firing temperature. There are just a few options available for metal conductor materials because of the high co-firing temperature. The primary components—which have high melting temperatures but weak conductivity—include tungsten, molybdenum, manganese, etc.—and are ultimately laminated and sintered to form. 

LTCC (Low-Temperature Co-fired Ceramic) 

Low-temperature co-fired multilayer ceramic substrate is another name for LTCC. To create a slurry that resembles mud, this method must first equally blend inorganic alumina powder with 30% to 50% glass material and an organic binder. Scrape the slurry into a sheet using a scraper, then dry the sheet to make a thin slice of the green embryo. Finally, drill holes in the sheet by the design of each layer's signal transmission. The internal circuit of the LTCC prints circuits and fills holes in the green embryo using screen-printing technology. Silver, copper, gold, and other metals can be used for the interior and exterior electrodes, respectively. It can be finished by sintering it at 850–900 °C in a sintering furnace.

LAM (Laser Activation Metallization)

Ionizing ceramic and metal with a high-powered laser beam, then allowing them to grow together to solidify their bond, LAM product characteristics include:

• An increase in thermal conductivity
• A thermal expansion coefficient that is more closely matched c. A metal sheet with less resistance
• The substrate can be soldered well and is suitable for high usage temperatures.
• Within 1 m 1 mm g, the conductive layer's thickness can be adjusted. Loss of low frequency
• Assembly at a high density is feasible.
• Absence of biological components
• There is no oxide layer present in the copper layer.
• Three-dimensional wiring and a substrate in three dimensions

Direct Plated Copper (DPC)

The innovation that significantly increased the viability of ceramics for designers was DPC, a recent advancement in the realm of ceramic substrate PCBs. Vacuum sputtering at high pressure and temperature is used in DPC to plate copper onto the substrate. Between the copper and ceramic layers, a small layer of titanium serves as a bonding contact. In this step of the process, a very thin layer of copper is applied to the ceramic substrate and is also applied to any holes that have already been drilled. Etching is then used to create the circuit. Very fine tracks and little undercutting are possible thanks to the thin copper. After that, panels are finished with copper plating that ranges from 10um (about 1/3 ounce) to 140um (4oz).DPC makes it possible for the circuit to use plated or filled vias. If a double-sided PTH board is needed, DPC must be utilized as standard PTH procedures do not yield accurate results on ceramics. Additionally, a circuit with various copper thicknesses in certain places can be created using DPC. As a result, a control part and a power section might be on the same layer.

Direct Bonded Copper (DBC)

With DBC, a high-temperature oxidation process is used to attach the copper to the ceramic substrate on either one or both sides. It provides hefty copper thickness choices between 140um (4 oz) and 350um (10oz). A copper-oxygen eutectic that effectively attaches to both copper and the substrate oxides occurs when the copper and substrate are heated in an environment of nitrogen with about 30 ppm of oxygen. Using conventional PCB technology and DBC, the copper layers may then be etched to create the necessary circuit. Because ceramics cannot be processed using conventional PTH methods, only DPC is employed for through-hole plating.

Active Metal Brazing (AMB)

The most recent advancement in Ceramic substrate is AMB. Active Metal Brazing, as opposed to DBC, creates the substrates without metallization. The copper is connected (brazed) directly to the ceramic foundation in a high-temperature vacuum. This provides a substrate with exceptional heat dissipation and excellent reliability. On thin ceramic substrates, the brazing method also permits copper weights of up to 800 m. AMB is perfect for power electronics because of these heavy copper materials.