What are electronic packaging materials?
As the basis of the entire electronic packaging technology, electronic packaging materials are mainly used for the electrical connection of the chip, moisture-proof heat dissipation, mechanical support, stress relief, etc. The purpose is to ensure that the chip and the entire system can work normally and stably in various complex and changeable environments.
Principles when selecting electronic packaging material
(1) High thermal conductivity;
(2) Match the thermal expansion coefficient of the chip material;
(3) Good heat resistance and good thermal stability;
(4)Good insulation, meeting the electrical interconnection and insulation requirements of devices;
(5) High mechanical strength, meeting the strength requirements of device processing, packaging and application;
(6) Reasonable price, suitable for large-scale production and application
In terms of packaging structure, electronic packaging materials mainly include substrates, wiring frames, interlayer dielectrics and sealing materials.
In terms of material composition, electronic packaging materials mainly include metals, ceramic plastics, etc.
Ceramic packaging material is a commonly used electronic packaging material. Compared with plastic and metal, its advantages are:
- Low dielectric constant, good high-frequency performance;
Good insulation and high reliability; - High strength, good thermal stability;
- Low thermal expansion coefficient and high thermal conductivity;
- Good air tightness and stable chemical properties;
- Good moisture resistance, not easy to produce microcracks
Types of electronic packaging ceramics
At present, the electronic packaging ceramic materials that have been put into use mainly include Al2O3,Si3N4, AIN, SiC, Be0, BN, etc.
Al2O3
At present, Al2O3 is the most widely used and most mature material in electronic packaging substrate ceramics.
But for Al2O3, the thermal conductivity is relatively low, the thermal expansion coefficient is relatively high, the adaptability to the silicon substrate is poor, and the internal stress of the electronic device is easy to accumulate during repeated cycles at a certain temperature. As a result, the failure probability of the chip is greatly increased. Therefore, it is difficult for Al2O3 to adapt to the development direction of high-power electronic devices, and it can only be used in low-frequency, low-power and other fields.
Si3N4
Among the existing ceramic materials that can be used as electronic packaging, Si3N4 ceramics have high bending strength (greater than 800MPa), good wear resistance, and are ceramic materials with the best comprehensive mechanical properties. At the same time, its thermal expansion coefficient is the smallest, so it is considered to be a potential substrate material for power device packaging.
However, its preparation process is complicated, its cost is high, and its thermal conductivity is relatively low. It is mainly suitable for applications in fields with high strength requirements but low heat dissipation requirements.
AIN
Compared with several other ceramic materials, AIN ceramics have greater comprehensive advantages. Mainly reflected in the following aspects:
(1) The thermal expansion coefficient matches the silicon material;
(2) High thermal conductivity, which is 6~8 times that of Al2O3 ceramics;
(3) Excellent electrical insulation, and low dielectric constant and loss;
(4) Excellent mechanical properties.
In addition to the high cost, the comprehensive performance of aluminum nitride ceramics is superior to several other ceramics. It is a very ideal electronic packaging material, especially suitable for fields with high thermal conductivity requirements.
SiC
Among the commonly used packaging ceramic materials, SiC has a thermal expansion coefficient that is quite close to that of silicon and has the advantages of high hardness, excellent chemical stability, high wear resistance and high thermal conductivity.
However, the thermal conductivity of polycrystalline SiC is only 60~70W/(m·K), which is caused by the anisotropy of polycrystalline. In addition, it also has significant disadvantages such as large dielectric loss, large dielectric constant, and low dielectric strength.
Be0
The production process of Be0 ceramics is relatively mature, the temperature of sintering into porcelain is low, it is easy to metalize, and the packaging strength is high. At present, the United States is the main producer and consumer of Be0 ceramic substrates in the world, and automobile companies such as Ford and General Motors use Be0 ceramics in large quantities in ignition devices.
However, the Be0 powder is toxic; the sintering temperature of Be0 is as high as 1900~C, and the production cost is high; in addition, its thermal conductivity decreases with the increase of temperature, which is not good for the high-temperature heat dissipation of the device. These reasons limit the popularization and application of Be0.
BN
BN has the characteristics of high thermal conductivity, thermal conductivity that hardly changes with temperature, a small dielectric constant, and good insulation performance. It is often used in tube sockets, tube shells, heat sinks, and microwave output windows of high-power transistors in radar windows.
However, cubic boron nitride is expensive and not suitable for the production of commonly used high thermal conductivity ceramics; the mismatch between the thermal expansion coefficient and silicon also limits its application.
Electronic Packaging Technology
Planar Package Ceramics:
Thin Film Ceramics (TFC)
Thick Film Printed Ceramics (TPC)
Direct Bonded Copper Ceramics (DBC)
Active Metal Brazed Ceramics (AMB)
Direct Plating Copper Ceramics (DPC)
Laser Activated Metal Ceramics (LAM)
Three-dimensional Packaging Ceramics:
High-Temperature Co-fired Ceramics (HTCC)
Low-Temperature Co-fired Ceramics (LTCC)
MultilayerSintering Ceramic Substrate (MSC)
Direct Adhere Ceramic Substrate (DAC)
Multilayer Plated Ceramic Substrate (MPC)
Direct Molding Ceramic Substrate (DMC)
Applications of electronic packaging ceramic
With the rapid development of electronic power devices, electronic packaging ceramic materials are in increasing demand due to their excellent thermal conductivity, dielectric, corrosion resistance, high strength and high reliability, and their application fields are also expanding.
Electronic packaging ceramics are widely used in electronic communications, medical machinery, lighting machinery, automotive electronics and other fields that are closely related to people’s lives. In addition, with the continuous development of the microelectronic packaging industry, electronic packaging materials also have broad application prospects in important fields such as the aerospace and military industries.
Electronic communication field
The field of electronic communication is closely connected with people’s life. Such as mobile communication equipment mobile phones, Bluetooth and other products.
Compared with traditional communication technologies, when the currently popular 5G communication technology is connected to working devices, it must first meet the three basic requirements of full-spectrum access, high-frequency band and even millimeter wave transmission, and ultra-high broadband transmission. Therefore, in the packaging process, it is necessary to further develop electronic ceramic packaging materials with low dielectric constant, high thermal conductivity, high insulation, large-scale integration, high frequency and high spectral efficiency to meet the development needs of the current information technology field.
Aerospace electronics field
Today, in the rapidly developing aerospace field, the performance requirements for electronic equipment on spacecraft are getting higher and higher. Therefore, research on new materials and new processes is becoming more and more urgent.
Ceramic materials have become the material of choice for MCM multi-chip micro-assembly processes due to their excellent dielectric, thermal, and mechanical properties, high reliability, easy integration, and diverse designs.
Medical machinery field
In medical machinery that is closely related to people’s health, because electronic ceramic packaging materials have the characteristics of small size, high reliability, and no side effects on the human body, they can fully meet the performance requirements of medical devices that need to be implanted into the human body, such as cardiac pacemakers and hearing aids. Therefore, it is widely used in medical testing and monitoring equipment and other devices and has great advantages in terms of performance and cost.
Automotive electronics field
With the continuous improvement of people’s performance requirements for the reliability and safety of daily travel tools such as cars, car control is developing rapidly in the direction of intelligence and electronics. Ceramic materials play an important role in the field of automotive electronic circuits due to their advantages of high-temperature resistance, vibration resistance and excellent sealing performance.
In addition, in the fields of military integrated circuits and surface acoustic wave devices, crystal oscillator devices, optoelectronic devices and other fields, electronic ceramic packaging materials also have a large room for development and are developing in the direction of multi-layering. The multi-layer ceramic packaging shell with good reliability, high flexibility and low development cost is also the focus of researchers.
As the basis of the entire electronic packaging technology, electronic packaging materials are mainly used for the electrical connection of the chip, moisture-proof heat dissipation, mechanical support, stress relief, etc. The purpose is to ensure that the chip and the entire system can work normally and stably in various complex and changeable environments.
At present, the electronic packaging ceramic materials that have been put into use mainly include Al2O3,Si3N4, AIN, SiC, Be0, BN, etc.
- Electronic communication field
- Aerospace electronics field
- Medical machinery field
- Automotive electronics field
