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Ceramic Multilayer PCBs Printed Circuit Board

Many users of printed circuit boards have found ceramic plates to be superior to conventional boards made from other materials. This is because they provide a suitable substrate for electronic circuits having high thermal conductivity and low coefficient of expansion (CTE). Multi-layer ceramic PCBs are extremely versatile and can replace complete traditional printed circuit boards with simple design and higher performance. Ceramic materials play a key role in electronic components.

Ceramic substrates such as aluminum oxide, aluminum nitride, and tantalum oxide are highly thermally conductive materials that rapidly and efficiently transfer heat away from hot spots to dissipate heat throughout the surface. PCB material (FR-4) is epoxy based and has poor thermal conductivity leading to hot spots, which reduces the lifetime of most semiconductor junctions.

In addition to the enviable thermal properties and coefficient of expansion, ceramic circuit board can operate at operating temperatures up to 350 degrees Celsius, resulting in smaller package sizes, better high frequency performance, and a sealed package that does not absorb water.

According to different manufacturing methods, there are currently three basic types of ceramic PCB plates:

A) Thick film ceramic PCB Board
Thick film ceramic PCB: With this technology, the thickness of the conductor layer exceeds 10 microns, which is thicker than the spray technology. The conductor is silver or gold palladium and is printed on a ceramic substrate. More thick film ceramic PCB.

B) Thin film ceramic PCB
Thin film technology ceramic PCB: Since the thickness of the resistor and the conductor film is less than 10 μm and the film is sprayed on the ceramic substrate, it is named as a thin film ceramic plate. More suitable for thin film ceramic PCB.

C) DCB ceramic PCB
The DCB (Direct Copper Bonding) technique represents a special process in which a copper foil and a core (Al2O3 or AlN) are bonded directly on one or both sides at a suitable elevated temperature and pressure. More DCB ceramic PCB.

Materials - Aluminum Nitride and Alumina
ceramic PCB boardCeramic PCBs are usually made of metal cores. For high thermal conductivity, aluminum nitride sheets are ideal for providing over 150 w / mK. However, due to the high price of aluminum nitride sheets, those who choose cheaper ceramic PCBs may find themselves using alumina sheets, which provide about 18-36w / mK. Both types will provide better thermal performance than metal core printed circuit boards because no electrical layer is required between the core and the circuit.

The use of silver as a print mark - covered with glass for protection - will further increase the thermal conductivity (406 W / mK). Other ceramic material options include boron nitride, tantalum oxide and silicon carbide. Due to the high operating temperature, the ceramic plates are not finished with OSP, HASL or other conventional surface treatments. However, if silver corrosion can be a problem, such as in a high sulfur environment, you can use a gold-plated ceramic printed circuit board to protect the exposed pad.

Ceramic PCB thermal conductivity

High ceramic PCB thermal conductivity may be the main reason why more industries turn to ceramics in their printed circuit boards and packages because this material has significant advantages over plastics in this respect. Better CTE matching and hermetic sealing will only increase the attractiveness of these materials. The challenge is that these materials, as well as the boards produced by ceramic PCB manufacturers, are much more expensive than traditional printed circuit board materials, and the materials of traditional printed circuit boards can be greatly increased in high-volume work. However, the benefits of ceramic plates and the need to improve thermal conductivity are so great that companies in any relevant industry that can afford to use ceramic plates may do so as necessary.

While we can estimate the level of thermal conductivity that each ceramic plate can provide, the final value will vary depending on the manufacturing process and the grain size and composition.

The most popular, despite the expensive ceramic - aluminum nitride - has a thermal conductivity that many people think is more than 150 W / mK, usually about 180 W / mK. However, studies have found values ​​ranging from 80 W / mK to 200 W / mK at room temperature, and when approaching 100 degrees Celsius, the value drops by more than a third. Other thermal ranges that we can identify at room temperature include alumina of 18-36 W / mK, yttrium oxide of 184-300, boron nitride of 15-600, and silicon carbide of 70-210.

Ceramic PCB application

Industries that require higher frequency connections and good heat resistance can benefit from ceramic PCBs. The main industries that ceramic PCBs can serve include: high-power circuits, chip-on-board modules, aerospace and heavy-duty equipment, automotive, medical equipment, heavy machinery, high-power transistors and transistor arrays, solar cell substrates, and other power applications such as DC conversion. And voltage regulator

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