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Types and Characteristics of Ceramic Substrates

by: Jun 02,2020 497 Views 0 Comments Posted in PCB Basic Information

LED,HTCC,LTCC,DBC Ceramic Substrates,PCB

Ceramic substrate refers to a special process board where copper foil is directly bonded to the surface (single side or double side) of alumina (Al2O3) or aluminum nitride (AlN) ceramic substrate at high temperature. Compared with traditional FR-4 or aluminum substrate, the ultra-thin composite substrate made has excellent electrical insulation performance, high thermal conductivity, excellent soft solderability and high adhesion strength, and can be etched various graphics like the PCB, with great current carrying capacity. It is suitable for products with high heat generation (high-brightness LED, solar energy), and its excellent weather resistance is more suitable for harsh outdoor environments.

What are the types of ceramic substrates?

1. According to the material

1). Al2O3

So far, the alumina substrate is the most commonly used substrate material in the electronics industry, because of its mechanical, thermal, and electrical properties compared to most other oxide ceramics, it has high strength and chemical stability, and is rich in raw materials. It is suitable for various technical manufacturing and different shapes. 

2). BeO

It has a higher thermal conductivity than metal aluminum and is used in applications requiring high thermal conductivity, but the temperature drops rapidly after 300 ℃. The most important thing is that its toxicity limits its development.

3). AlN

There are two very important properties of AlN worth noting: one is high thermal conductivity, and the other is the expansion coefficient matching Si. The disadvantage is that even if there is a very thin oxide layer on the surface, it will affect the thermal conductivity. Only by strictly controlling the materials and processes can we produce an AlN substrate with good consistency. At present, compared to the AI2O3, the price of AlN is relatively high, which is also a small bottleneck restricting its development. However, as the economy improves and technology upgrades, this bottleneck will eventually disappear.

Based on the above reasons, it can be known that alumina ceramics are still in a dominant position in the fields of microelectronics, power electronics, hybrid microelectronics, and power modules due to their superior comprehensive performance, and are widely used.

2. According to the manufacturing process

1).HTCC (High-Temperature Co-fired Ceramic)

HTCC is also called high temperature co-fired multilayer ceramic. The manufacturing process is very similar to LTCC. The main difference is that HTCC's ceramic powder is not added to glass materials. Therefore, HTCC must be dried and hardened at a high temperature of 1300 ~ 1600 ℃. Due to its high co-firing temperature, the choice of metal conductor materials is limited. Due to its high co-firing temperature, the choice of metal conductor materials is limited. The main materials are tungsten, molybdenum, manganese, etc., which have high melting points but poor conductivity, and are finally laminated and sintered to shape.

2).LTCC (Low-Temperature Co-fired Ceramic)

LTCC is also called low temperature co-fired multilayer ceramic substrate. This technology must first mix inorganic alumina powder with about 30% ~ 50% glass material with an organic binder to make it evenly mixed into a mud-like slurry. Use a scraper to scrape the slurry into a sheet, and then form a thin piece of the green embryo through a drying process, and then drill through holes according to the design of each layer as the signal transmission of each layer. The internal circuit of LTCC uses screen-printing technology to fill holes and print circuits on the green embryo respectively. The internal and external electrodes can use silver, copper, gold and other metals respectively. It can be completed by sintering it in a sintering furnace at 850 ~ 900 ℃.

3) DBC (Direct Bonded Copper)

Direct Bonded Copper technology uses copper's oxygen-containing eutectic solution to directly deposit copper on the ceramic. The basic principle is to introduce an appropriate amount of oxygen between copper and ceramic before or during the deposition process. In the range of 1065 ℃ ~ 1083℃, copper and oxygen form a Cu-O eutectic liquid. The DBC technology uses this eutectic liquid to chemically react with the ceramic substrate to generate CuAlO2 or CuAl2O4. Also, it infiltrates the copper foil to achieve the combination of the ceramic substrate and the copper plate.

4).DPC (Direct Plate Copper)

DPC is also known as direct copper-plated substrate. Take the DPC substrate technology as the example: First, the ceramic substrate is pre-processed and cleaned, and it is sputtered and bonded to the copper metal composite layer on the ceramic substrate using the professional film manufacturing technology-vacuum coating method, and then the photoresist with yellow light lithography is re-exposed, developed, etched, and the film removal process is completed Line making Finally, the thickness of the circuit is increased by electroplating / electroless plating deposition. After the photoresist is removed, the metallization circuit is completed.

5). LAM (Laser Activation Metallization)

Using a high-energy laser beam to ionize ceramic and metal, let them grow together to make them firmly together. 

Characteristics of LAM products:

a. Higher thermal conductivity

b. More matched thermal expansion coefficient

c. The metal film with lower resistance

d. The solderability of the substrate is good, and the use temperature is high

e. Good insulation

f. The thickness of the conductive layer can be customized within 1μm ~ 1mm

g. Low frequency loss

h. High-density assembly is possible

i. Free of organic ingredients

j. The copper layer does not contain an oxide layer

k. Three-dimensional substrate & Three-dimensional wiring

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