Multilayer ceramic pcb substrate manufacturing process: HTCC and LTCC technology

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Multilayer ceramic substrate is also known as ceramic shell, ceramic tube shell. At present, most of the multilayer ceramic substrates are manufactured using co-fired ceramic technology – high-temperature co-fired ceramic technology (HTCC), low-temperature co-fired ceramic technology (LTCC) to achieve the mainstream of large-scale manufacturing of multilayer ceramic substrates.

In this article, we will focus on analyzing the advantages and applications of HTCC and LTCC two processes, to facilitate the selection of manufacturing processes that have a clearer direction. Details are as follows:

What is HTCC?

HTCC (High Temperature co-fired Ceramic), using materials such as tungsten, molybdenum, molybdenum, manganese and other high melting point metal heating resistor paste in accordance with the requirements of the heating circuit design printed on 92 ~ 96% of the alumina cast ceramic billet, 4 ~ 8% sintering additives, and then multi-layer stacked, at a high temperature of 1,500 ~ 1,600 ℃ co-fired into one. The product is co-fired under 1500～1600℃.

Therefore, it has the advantages of corrosion resistance, high temperature resistance, long service life, high efficiency and energy saving, uniform temperature, good thermal conductivity, fast thermal compensation, etc. Moreover, it does not contain lead, cadmium, mercury, hexavalent chromium, polybrominated biphenyls (PBBs), polybrominated diphenyl ethers (PBDEs), and other hazardous substances, and it complies with the environmental protection requirements of the European Union, such as RoHS.

Due to the high firing temperature, HTCC cannot use low melting point metal materials such as gold, silver, copper, etc. Refractory metal materials such as tungsten, molybdenum, manganese, etc. must be used, and the low electrical conductivity of these materials will cause defects such as delayed signals, and therefore they are not suitable for making the substrate of high-speed or high-frequency microassembly circuits. However, HTCC substrates have a wide range of applications in high-power microassembly circuits due to their advantages of high structural strength, high thermal conductivity, good chemical stability and high wiring density.

What is LTCC?

Low Temperature Co-fired Ceramic technology LTCC (Low Temperature Co-fired Ceramic) is a low-temperature sintered ceramic powder made of raw ceramic tape with precise thickness and density, in the raw ceramic tape using laser perforation, microvia slurry injection, precision conductor paste printing and other processes to make the required circuit graphics, and a number of passive components (e.g., low-tolerance capacitors, resistors, filters.), impedance converters, couplers, etc. buried in a multilayer ceramic substrate, and then stacked together, Impedance converter, coupler, etc.) buried in a multilayer ceramic substrate, and then stacked together, the inner and outer electrodes can be used respectively silver, copper, gold and other metals, sintered at 900 ℃, made of three-dimensional space does not interfere with each other’s high-density circuits, but also made of built-in passive components of the three-dimensional circuit substrate, the surface of which can be mounted on the IC and active devices, made of passive/active integrated functional modules, can be further circuit This makes it possible to further miniaturize circuits and increase density, and is particularly suitable for high-frequency communication components.

LTCC integrated components include a variety of substrates carrying or embedded in a variety of active or passive components of the product, integrated components product program includes components, substrates and modules.

HTCC technology vs LTCC technology

 

High temperature co-fired ceramic technology

▶Insulating materials: alumina, aluminum nitride, oxide plating, etc.
▶Conductor material: tungsten, platinum, platinum-manganese, etc.
▶Co-firing temperature: higher than 1400℃
▶Advantages: high mechanical strength, high thermal conductivity, low material cost, chemically stable.
▶Disadvantages: high on-resistance, high manufacturing cost


Low temperature co-fired ceramic technology

▶Insulating materials: microcrystalline glass, ceramic + glass composite system, amorphous glass, etc.
▶Conductor materials: gold, silver, copper, vantage – silver, etc.
▶Co-firing temperature: below 900°C
▶Advantages: low on-resistance, low manufacturing cost, low coefficient of thermal expansion, low dielectric constant and easy to adjust, can be buried passive devices, high-frequency characteristics are excellent, and can be produced with a line width of as low as 50 um of fine circuits.
▶Disadvantages: low mechanical strength, low thermal conductivity, high material cost.

Technology Benefits


Advantages of HTCC technology

HTCC because of the use of tungsten, platinum, and other high melting point metals, these metals greatly increase the RF loss of the component. The advantages are high structural strength, good chemical stability and high wiring density, and its thermal conductivity is as high as 20W/mK, which is far greater than the thermal efficiency of LTCC substrate. In contrast, the thermal conductivity of LTCC substrate is only 3W/mK, which makes it difficult to dissipate heat in the structure of high-density boards and easily makes the chip damaged.


Advantages of LTCC technology

(1) has good electrical and mechanical properties, such as high frequency characteristics, good temperature stability of the resonant frequency, the dielectric constant covers a wide range, the coefficient of thermal expansion is close to silicon.

(2) Has high system stability and reliability.

(3)Can produce 3D microstructures including cavities and channels.

(4)Possesses high level of integration characteristics (sensors, drivers, microfluidic control, electronic and optoelectronic systems for LTCC, etc.) ;and

(5) Very good characteristics at high voltage.

(6) High voltage characteristics and high vacuum. In addition, LTCC manufacturing industry is simple, fast and inexpensive, with low capital investment, short cycle time and high profitability.

Application of HTCC technology

High-temperature co-fired ceramic products mainly include ceramic multilayer substrates, ceramic packaging shells, UVLED brackets, VCSEL brackets, various types of heating pads, thermal bridges, etc., which are mainly used in microwave device packaging, large-scale integrated circuit packaging, hybrid integrated circuit packaging, optoelectronic device packaging, SMD packaging, LED chip packaging, semiconductor packaging and other packaging fields. HTCC ceramic substrate can be sintered with metal materials such as deforestation alloy to make HTCC package shell, which greatly saves the wiring space.

Application of LTCC technology

LTCC products have a wide range of applications, such as various types of cell phones, Bluetooth modules, GPS, PDA, digital cameras, WLAN, automotive electronics, optical drives and so on. Among them, the use of cell phones occupies the main part, about 80% above; followed by Bluetooth module and WLAN. due to the high reliability of LTCC products, the application in automotive electronics is also rising. LTCC products used in cell phones include LC filters, duplexers, function modules, transceiver switching function modules, balanced-unbalanced converters, couplers, power dividers, common mode chokes and so on.