Ceramic PCB - LTCC (Low Temperature Co-fired Ceramic)

LTCC (Low Temperature Co fired Ceramic) is a remarkable integrated component technology that began to develop in 1982. It has become the mainstream technology of passive integration and the development direction of the passive component field, as well as a new economic growth point for the component industry.

LTCC products have a wide range of applications, such as mobile phones of various standards, Bluetooth modules, GPS, PDA, digital cameras, WLAN, automotive electronics, optical disc players, etc. Among them, mobile phone usage accounts for the main part, accounting for more than 80%; followed by Bluetooth modules and WLAN. Due to the high reliability of LTCC products, their applications in automotive electronics are also increasing. LTCC products used in mobile phones include LC filters, duplexers, functional modules, transceiver switch functional modules, balanced-unbalanced converters, couplers, power dividers, common mode chokes, etc.

The purpose of using LTCC technology in SMD is to increase assembly density, reduce volume, reduce weight, add new functions, improve reliability and efficiency, and shorten the assembly cycle. Voltage controlled oscillator (VCO) is a key component of mobile communication equipment. VCO can be produced through LTCC technology to meet the requirements of mobile communication for small size, lightweight, low power consumption, and low phase noise (high C/N ratio) . Internationally, LTCC technology has been applied to make high-performance surface-mounted VCOs, and a series of products has been formed. The volume of VCOs has been greatly reduced by using LTCC technology. From 1996 to 2000, the volume of VCO decreased by more than 90%. The volume of this surface-mounted VCO is only 1/5-1/20 of the volume of the original VCO with leads. The new VCO produced using LTCC technology has the advantages of small size, low power consumption, good high-frequency characteristics, small phase noise, and suitable for surface mounting, and has been widely used in the field of mobile communications. This kind of miniaturized VCO is widely used in digital communication system terminals such as GSM, DCS, CDMA, and PDC, as well as satellite communication-related terminals such as the Global Positioning System (GPS).

The rapid development of mobile communications has further promoted the miniaturization of DC/DC converters, providing a broad application market for SMD DC/DC converters. Many foreign power supply manufacturers are using LTCC technology to actively develop standard SMD DC/DC converters with rated power of 5-30W and various universal input and output voltages. Some new DC/DC converter designs also offer shorter start-up times. In addition, LTCC technology has also been used to produce chip multi-layer antennas, Bluetooth components, radio frequency amplification voltage-controlled attenuators, power amplifiers, phase shifters and other surface-mounted devices for mobile communications.

LTCC modules have received great attention and are widely used in military and aerospace equipment due to their compact structure and strong resistance to mechanical shock and thermal shock. Its application in automotive electronics will be very extensive in the future.

LTCC devices can be roughly divided into LTCC components, LTCC functional devices, LTCC packaging substrates, and LTCC module substrates based on the number of components they contain and their role in the circuit.

LTCC functional devices: In early communication products, filters and duplexers were mostly bulky dielectric filters and duplexers. The filters on GSM and CDMA mobile phones have been replaced by surface acoustic filters or embedded in module substrates, while the filters on PHS and cordless phones are mostly LC filters made of LTCC with small size and low price. Bluetooth and wireless network cards have been using LC filters from the beginning.

The filters made of LTCC include bandpass, high pass, and low-pass filters, with frequencies ranging from tens of MHz to 5.8 GHz. LC filters have unparalleled advantages in terms of volume, price, and temperature stability, and it is not difficult to understand why they continue to receive widespread attention.

The above-mentioned RF devices made by LTCC have a history of several years. Japan's Murata, Dongguang, TDK, Shuangxin Electric, Taiwan's Huaxin Technology, ACX, South Korea's Samsung, etc. are all mass-produced and sold. China only started developing similar products in 2003.

LTCC chip antenna: WLAN and Bluetooth devices have short communication distances, low transmission and reception power, and low requirements for antenna power and transmission and reception characteristics. However, strict requirements are placed on the PCB area and cost of the antenna. The chip antenna prepared by LTCC has significant advantages such as small size, easy surface mounting, high reliability, and low cost, and has been widely used in WLAN and Bluetooth.

LTCC module substrate: The modularization of electronic components has become an undeniable fact in the industry, with LTCC being the preferred method. The available module substrates include LTCC, HTCC (high-temperature co fired ceramics), traditional PCBs such as FR4, and PTFE (high-performance polytetrafluoroethylene). The sintering temperature of HTCC is above 1500 ℃, and the matching refractory metals such as tungsten, molybdenum/manganese have poor conductivity, and the sintering shrinkage is not as easy to control as LTCC. The dielectric loss of LTCC is one order of magnitude lower than that of RF4. PTFE has lower losses but poorer insulation properties. LTCC can better control accuracy than most organic substrate materials. There is no organic material that can be comprehensively compared with the high-frequency performance, size, and cost of LTCC substrates.

The research on LTCC module substrates is booming, and there are already various commercial productions and applications of LTCC modules. More than ten companies, including Murata, Mitsubishi Electric, Kyocera, TDK, Epcos, Hitachi, Avx, produce only mobile phone antenna switch modules (ASM). In addition, Bluetooth modules from companies such as NEC, Murata, and Ericsson, as well as amplifier modules from companies such as Hitachi, are all made using LTCC technology.

LTCC modules have received great attention and wide application in military and aerospace equipment due to their compact structure, strong resistance to mechanical and thermal impacts. In the future, its application in automotive electronics will be very extensive

LTCC functional devices and modules are mainly used in communication products such as GSM, CDMA, PHS mobile phones, cordless phones, WLAN, and Bluetooth. Except for cordless phones with a capacity of over 40 Mbps, these types of products have only developed in the past 5 years. In order to seize the market as soon as possible, most of the initial design schemes for terminal products are purchased, and even the schemes are packaged with components for procurement. The purchased schemes all use mature components. In the past few years, the main goal of terminal product manufacturers was to expand market share, but the cost pressure was not high and they could not take into account the localization of components in China. With the overcapacity of terminal products, price and cost competition will become increasingly fierce, providing a good market opportunity for the development of TCC devices.

LTCC is a trend in future component manufacturing processes, and the trend towards integration is very evident. Compared with other integrated technologies, LTCC has these characteristics: the dielectric constant of LTCC material can vary widely according to the different ingredients, which increases the flexibility of circuit design; Ceramic materials have excellent high-frequency, high-Q characteristics, and high-speed transmission properties; Using high conductivity metal materials as conductor materials is beneficial for improving the quality factor of circuit systems; Produce circuit board with high layers, reduce the length and number of connecting chip conductors, and enable the production of thin line structured circuits with a line width less than 50 μ m, achieving more wiring layers, integrating a variety of components with a wide range of parameters, making it easy to achieve multifunctionality and improve assembly density; Can adapt to high current and high temperature resistance requirements, with good temperature characteristics; It has good compatibility with thin film multi-layer wiring technology, and the combination of the two can achieve higher assembly density and better performance of hybrid multilayer LTCC and hybrid multi chip components; Easy to implement a multi-layer wiring and packaging integrated structure, further reducing volume and weight, improving reliability, high temperature resistance, and high humidity, and can be applied in harsh environments; Adopting a non continuous production process facilitates quality inspection of each layer of wiring and interconnect holes before substrate firing, which is beneficial for improving the yield and quality of multilayer LTCC, shortening the production cycle, and reducing costs.