What is HTCC and LTCC

With the rise and application of power devices, especially third-generation semiconductors, semiconductor devices are gradually developing in the direction of high power, miniaturization, integration, and multi-function, which also puts forward higher requirements for the performance of packaging substrates. Ceramic substrates have the characteristics of high thermal conductivity, good heat resistance, low thermal expansion coefficient, high mechanical strength, good insulation, corrosion resistance, radiation resistance, etc., and are widely used in electronic device packaging.

Among them, co-fired multi-layer ceramic substrates are gradually popularized and applied in high-power device packaging because they can be fired at one time for electrode materials, substrates, and electronic devices to achieve high integration.

Co-fired multi-layer ceramic substrates are made of many single-piece ceramic substrates through lamination, hot pressing, degumming, sintering and other processes. Since the number of layers can be made more, the wiring density is high, and the interconnect length can be as much as possible. Therefore, it can meet the requirements of the electronic whole machine for circuit miniaturization, high density, multi-function, high reliability, high speed and high power.

According to the temperature difference in the preparation process, co-fired ceramic substrates can be divided into high-temperature co-fired ceramic (HTCC) multilayer substrates and low-temperature co-fired ceramic (LTCC) Multilayer substrate.

(a)HTCC ceramic substrate products (b) LTCC ceramic substrate products

So what is the difference between these two technologies?

In fact, the production process of the two is basically the same. They all have to go through the preparation of slurry, casting green tape, drying green body, drilling via holes, screen printing and filling holes, screen printing circuits, lamination sintering, and finally slicing and other post-processing preparations. process. However, the HTCC technology is a co-firing technology with a sintering temperature greater than 1000 °C. Usually, the debinding treatment is performed at a temperature below 900 °C, and then sintered at a higher temperature environment of 1650 to 1850 °C. Compared with HTCC, LTCC has a lower sintering temperature, generally lower than 950 °C. Due to the disadvantages of high sintering temperature, huge energy consumption, and limited metal conductor materials on HTCC substrates, the development of LTCC technology has been promoted.

Typical Multilayer Ceramic Substrate Manufacturing Process

The difference in sintering temperature first affects the choice of materials, which in turn affects the properties of the prepared products, resulting in the two products being suitable for different application directions.

Due to the high firing temperature of HTCC substrates, low melting point metal materials such as gold, silver, and copper cannot be used. Refractory metal materials such as tungsten, molybdenum, and manganese must be used. The production cost is high, and the electrical conductivity of these materials is low, which will cause signal delay. and other defects, so it is not suitable for high-speed or high-frequency micro-assembled circuit substrates. However, due to the higher sintering temperature of the material, it has higher mechanical strength, thermal conductivity and chemical stability. At the same time, it has the advantages of wide material sources, low cost, and high wiring density. , The high-power packaging field with higher thermal conductivity, sealing and reliability requirements has more advantages.

The LTCC substrate is to reduce the sintering temperature by adding amorphous glass, crystallized glass, low melting point oxide and other materials to the ceramic slurry. Metals such as gold, silver and copper with high electrical conductivity and low melting point can be used as conductor materials. It not only reduces the cost, but also obtains good performance. And due to the low dielectric constant and high frequency and low loss performance of glass ceramics, it is very suitable for application in radio frequency, microwave and millimeter wave devices. However, due to the addition of glass materials to the ceramic slurry, the thermal conductivity of the substrate will be low, and the lower sintering temperature also makes its mechanical strength inferior to that of the HTCC substrate.

Therefore, the difference between HTCC and LTCC is still a situation of trade-offs in performance. Each has its own advantages and disadvantages, and it is necessary to select suitable products according to specific application conditions.

The difference HTCC and LTCC

In short, HTCC substrates will play a major role in electronic packaging for a long time due to the advantages of mature technology and cheap dielectric materials. Its natural advantages will be more prominent, and it is more suitable for the development trend of high frequency, high speed and high power. However, various substrate materials have their own advantages and disadvantages. Due to different application circuit requirements, the performance requirements of substrate materials are also different. Therefore, various substrate materials will coexist and develop together for a long time.