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 put forward higher requirements on the performance of packaging substrates. Ceramic substrates have high thermal conductivity, good heat resistance, low coefficient of thermal expansion, high mechanical strength, good insulation, corrosion resistance, radiation resistance, etc., and are widely used in the packaging of electronic devices.
Among them, the co-fired multilayer ceramic substrates are gradually being used in high-power device packaging because they can be fired into electrode materials, substrates, and electronic devices at once to achieve a high degree of integration.
Co-firing multilayer ceramic substrates are made of many single ceramic substrates through the process of lamination, hot pressing, debinding, and sintering, etc. Since the number of layers can be made more, the wiring density is higher and the length of interconnection lines can be shortened as much as possible, and the assembly density and signal transmission speed can be improved, so it can adapt to the requirements of electronic machine for circuit miniaturization, high density, multifunction, high reliability, high speed, and high power.
According to the difference in temperature in the preparation process, the co-fired ceramic substrate can be divided into high-temperature co-fired ceramic (HTCC) multilayer substrate and low-temperature co-fired ceramic (LTCC) multilayer substrate.
What is the difference between these two technologies?
In fact, the production process of both is basically the same, both have to go through the preparation process of preparing slurry, flowing raw tape, drying raw material, drilling guide through holes, screen printing and filling holes, screen printing lines, laminated sintering, and finally post-treatment such as slicing. Only HTCC technology is a co-sintering technology with sintering temperature greater than 1000°C. Usually, the sintering process is first performed below 900°C, and then sintered and formed at a higher temperature environment of 1650-1850°C. LTCC, on the other hand, has a lower sintering temperature compared to HTCC, generally below 950°C. The development of the LTCC process has been prompted by the disadvantages of HTCC substrates such as high sintering temperature, huge energy consumption, and limited metal conductor materials.
The difference in sintering temperature first affects the choice of materials, which in turn affects the performance of the prepared product, resulting in two products suitable for different application directions.
HTCC substrates are not suitable for high-speed or high-frequency micro-assembly circuit substrates because of the high sintering temperature and cannot use low melting point metal materials such as gold, silver and copper, and must use refractory metal materials such as tungsten, molybdenum and manganese, which are more expensive to make, and the low electrical conductivity of these materials can cause defects such as signal delay. However, because the material is sintered at a higher temperature, and thus has higher mechanical strength, thermal conductivity, and chemical stability, as well as the advantages of a wide range of material sources and low cost, high wiring density, HTCC substrates are more advantageous in high-power packaging areas with high requirements for thermal stability, substrate mechanical strength, thermal conductivity, hermeticity, and reliability.
And LTCC substrate is by adding amorphous glass, crystallized glass, low melting point oxide and other materials in the ceramic paste to reduce the sintering temperature, you can use high conductivity and low melting point of gold, silver, copper and other metals as conductor materials, both to reduce the cost, but also to obtain good performance. And because of the low dielectric constant and high frequency low loss properties of glass-ceramics, making it ideal for applications in RF, microwave and millimeter wave devices. However, the addition of glass-like materials to the ceramic paste results in a low thermal conductivity of the substrate, and the lower sintering temperature also makes it less mechanically strong than HTCC substrates.
Therefore, the difference between HTCC and LTCC is also still a situation where the performance of each is different from the other, each has its own advantages and disadvantages, and the appropriate product needs to be selected according to the specific application conditions.
Differences between low temperature co-fired ceramics and high temperature co-fired ceramics
Aluminum oxide, mullite, aluminum nitride, etc
(1) Microcrystalline glass-based materials; (2) Glass + ceramic composite materials; (3) Amorphous glass-based materials
Conductive metal materials
Tungsten, molybdenum, manganese, molybdenum-manganese, etc.
Silver, gold, copper, palladium-silver, etc.
(1) Higher mechanical strength;
(2) Higher heat dissipation coefficient;
(3) Lower material cost;
(4) Stable chemical properties;
( 5) High density of wiring
(1) Higher conductivity;
(2) Lower production cost;
(3) Smaller thermal expansion coefficient and dielectric constant and easy to adjust the dielectric constant;
(4) excellent high frequency properties.
(5) Due to the low sintering temperature, some components can be sealed inside
( 1) lower conductivity; (2) higher production cost
(1) low mechanical strength; (2) low heat dissipation coefficient; (3) high material cost
Highly reliable microelectronic integrated circuits, high-power micro-assembly circuits, automotive high-power circuits, etc.
High-frequency wireless communication, aerospace, memory, driver, filter, sensor, automotive electronics, etc.
In short, HTCC substrate due to the mature process, dielectric materials, such as cheap advantages in electronic packaging, a long time will play a major role, but in the future, with the continuous improvement of materials, process control and technology is becoming more mature, LTCC’s natural advantages will be more prominent, more suitable for today’s high frequency, high speed, high power development trend. However, various substrate materials have their advantages and disadvantages, due to the specific application circuit requirements being different, the substrate material performance requirements are not the same. Therefore, a variety of substrate materials will co-exist and develop over a long period of time.