Different types of ceramic pcb

Ceramic PCB is widely used in power electronics, electronic packaging, hybrid microelectronics and multi-chip modules due to its excellent thermal conductivity and air tightness. But not everyone is clear about the classification. Many manufacturers think ceramic PCBs are expensive and fragile as soon as they hear about ceramic PCBs. Yes, this is indeed a shortcoming of ceramic PCBs, but not all ceramic PCBs are like this. Today we will tell you about the different types of ceramic PCBs.

Al2O3 ceramic PCB

Al2O3 ceramic PCB ( alumina ceramic PCB) refers to various ceramic PCBs with Al2O3 as the main raw material and an Al2O3 content of more than 75%. It has a rich source of raw materials, with advantages of low price, high mechanical strength and hardness, good insulation performance, good heat shock resistance, good chemical resistance, high dimensional accuracy, and good adhesion to metals. It is a ceramic substrate material with good comprehensive performance. Currently used Al2O3 ceramic substrates, the content of Al2O3 accounts for 85% to 99.5%. Among them, 96% Al2O3 ceramic PCB is widely used in the production of thick film circuit substrates and chip devices. The thermal conductivity of Al2O3 at room temperature is 29W/(m·K), which is close to the thermal conductivity of steel; with the increase of Al2O3 content, the electrical insulation performance and thermal conductivity of Al2O3 ceramic PCB will increase, but At the same time, it will also lead to an increase in the firing temperature, an increase in energy consumption, a large loss of kiln furniture, and an increase in manufacturing costs.

SiC ceramic PCB

The thermal conductivity of SiC ceramic PCB is very high, 100～490W/(m·K) at room temperature, and it is related to the purity of SiC crystals. The higher the purity, the greater the thermal conductivity; the oxidation resistance is good, and the decomposition temperature is above 2500℃, it can still be used at 1600℃ in an oxidizing atmosphere; the coefficient of thermal expansion is also low, and it is close to Si, with good electrical insulation performance; SiC has a Mohs hardness of 9.75, second only to diamond and cubic BN, and has high mechanical strength. SiC ceramics have strong covalent bond characteristics and are difficult to sinter. Usually, a small amount of boron or aluminum oxide is added as a sintering aid to increase the density. Experiments show that beryllium, boron, aluminum and their compounds are the most effective additives, which can make SiC ceramics denser than 98%.

BeO ceramic PCB

BeO has a brazine structure, in which oxygen ions are arranged in a hexagonal close-packed manner to form a hexagonal lattice. The general oxide is usually an ionic compound, but BeO has a strong covalent bond and an average molecular weight of only 12. Because of its good electrical properties, luminescence and photochemical properties, high mechanical strength, low dielectric loss, etc, it become one of the materials that people pay attention to.

AlN ceramic PCB

AlN ceramic PCB (aluminum nitride ceramic) is a new type of high thermal conductivity ceramic packaging material. It has been extensively studied in the 1990s and gradually developed. It is currently generally considered to be a promising electronic ceramic packaging PCB. AlN material has high thermal conductivity, excellent dielectric properties, high electrical insulation strength, stable chemical properties, strong corrosion resistance, and good mechanical properties. In particular, its thermal expansion coefficient matches with silicon, which makes it an ideal semiconductor packaging substrate materials and have been widely used in integrated circuits, microwave power devices, millimeter-wave packaging, high-temperature electronic packaging and other fields.

Ceramic PCB for IGBT Module

IGBT stands for insulated-gate bipolar transistor. It is a bipolar transistor with an insulated gate terminal. The IGBT combines, in a single device, a control input with a MOS structure and a bipolar power transistor that acts as an output switch. IGBTs Ceramic PCB are suitable for high-voltage, high-current applications. They are designed to drive high-power applications with a low-power input.

IGBT, or Insulated Gate Bipolar Transistor, is a BJT transistor with a MOS Gate, or we can say an IGBT module is the combination of a BJT and a MOS Gate. An IGBT chip is small in size, but it can control electrical energy transmission and achieve 100,000 times of current switch at ultra-high voltages of 650 million V in only 1 second.

IGBT modules have been applied in automotive, industrial, aerospace, consumer electronics, and many other industries for many years. But how to optimize the thermal dissipation of an IGBT package so the module can work at a higher power? If thermal can dissipate more quickly, the IGBT module can have more advanced applications. For this purpose, engineers are using ceramic PCBs for IGBT packaging.

Ceramic PCBs dissipate thermal from IGBT chip to the outer packaging

You may ask, how much thermal does an IGBT module generate when it works? It is equal to the heat generated by 100 electric furnaces. So much thermal has to be dissipated immediately from the IGBT chip and leads to the application of ceramic PCBs.

How does a ceramic PCB protect the IGBT module from the heat? In an IGBT module, a ceramic PCB is placed under the IGBT chip, or we can say that the chip is assembled on the ceramic circuit board. The ceramic PCB connects and supports the chip and dissipates thermal quickly from it to the outer packaging. In this way, the chip is protected from the influence of thermal.

Why Ceramic PCBs can be used for IGBT thermal dissipation

There are alumina (Al₂O₃) PCBs, aluminum nitride (AlN) PCBs, and silicon nitride (Si₃N₄) PCBs used for thermal dissipation of IGBT modules.

Why ceramic PCBs can dissipate thermal effectively for the IGBT module? Because ceramic materials have good properties of thermal dissipation and electrical insulation. Unlike aluminum substrate PCBs, ceramic PCBs do not use an insulation layer that hinders thermal dissipation. During the ceramic PCB manufacturing process, the copper-clad is directly bonded onto the ceramic substrate at high temperatures under high pressures. Then the circuit layer is manufactured by the photoresist coating method. When the circuit board is manufactured, the IGBT and other components are mounted on the board. Ceramic materials have ultra-high insulation and can withstand breakdown voltage up to 20KV/mm. The thermal conductivity of alumina PCBs is 15-35W/mK, aluminum nitride PCB 170-230W/mK, and silicon nitride PCB 80+W/mK. On the contrary, an aluminum PCB has thermal dissipation of only 1-12W/mK.

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