1. Introduction
In today's information age, as portable computers, mobile communications and the rapid development of military electronic technology, the demand for integrated circuit (IC) is soaring, which prompted microelectronic packaging technology ushered in the "explosive" development period. The global packaging market status and forecast shown in Table 1.
Someone called encapsulation techniques 1990s ten important one (1). Microelectronic packaging technology has undergone TO-shaped package, dual in-line package (DIP), the peripheral surface mount package and PATTERN package development stage leads. Table 2 shows the electronic packaging developments. In the new century, with the development of the IC industry, represented by the microelectronics industry for electronic packaging industry has created unlimited opportunities for development. Engaged in more than 400 packaged semiconductor plant in mainland China or in the package and there are more than 200 engaged. 2000 production situation of China's major circuit package as shown in Table 3. Expected in 2002, more than 10 foreign-owned companies, 15 joint ventures and more than 40 major domestic packaging companies in mainland China for packaging capabilities: IC for 16.124 billion, TR was 30.964 billion (2). According to expert estimates, in the next 10 years, domestic investment in the packaging industry will reach 60 billion yuan, foreign investment in China for electronic packaging industry will reach $ 7.5 billion.
An important support for electronic packaging technology is the electronic packaging materials. For IC package, the electronic packaging materials refer encapsulated integrated circuits (sealed) body. Not only for chips with mechanical support and environmental effects through the package to avoid the atmospheric water vapor, impurities and chemical pollution and erosion of the atmosphere, so that the IC chip can play a normal electrical function stably, and the package of the device and thermal performance of the circuit and the reliability plays an important role, a circuit packaging costs and the cost of the chip is almost equivalent. Electronic packaging materials are plastic materials, ceramics, packaging materials and metal packaging materials. Demand for plastic materials currently the largest, followed by ceramic packaging materials. Now, electronic packaging materials industry has become the semiconductor industry is an important branch, it relates to chemical, electrical, thermal, mechanical and process equipment, and other disciplines. China's electronic packaging materials after decades of unremitting efforts, has made considerable progress. In recent years, many overseas enterprises on the mainland in order to reduce the cost of packaging, packaging materials have to implement localization support strategy, especially as a higher stage of development of packaging technology multi-chip module (MCM) rapid development (3), for our electronic packaging development of materials provides a good opportunity.
2, plastic materials
The amount of plastic materials in electronic packaging materials in the largest, fastest growing, it is to achieve miniaturization of electronic products, light weight and low cost of an important class of packaging materials. At present, China's plastic ability to maintain an annual growth rate of over 30%. Materials used plastic material is a thermosetting plastics, including phenolic, polyester, epoxy and silicone (silicone plastic). As the epoxy molding compound epoxy molding compound (EMC) is a novolac epoxy resin, phenol resin and a filler (SiO2), release agents, curing agents, dyes and other components. Plastic material is a silicone resin, a silicone resin, an additional material (SiO2), release agents, curing agents, dyes and other components. This paper describes the epoxy molding compound.
2.1 electronic packaging technology for electronic plastic material performance requirements
As integrated circuit line width smaller, more integrated and surface mount technology (SMT), the ring-grid array (BGA), widely used MCM technology, the plastic material of increasingly high performance requirements. Requires plastic material having the following properties: ① high-purity materials, especially ionic impurities is minimal. ② the adhesion device and the lead frame is good. ③ water absorption, low moisture permeability. ④ molding shrinkage and internal stress is small. ⑤ coefficient of thermal expansion (CTE) is small, the thermal conductivity is high. ⑥ forming, hardening time is short, good mold release. ⑦ good flowability and filling, burrs and less. ⑧ has good flame resistance. Plastic materials for its low cost, simple and suitable for mass production technology in integrated circuit package has come out on top. Currently the reliability of the United States has enough plastic circuits and ceramic and metal packages circuit comparable, so you can predict the plastic material into the era of military field nor in the foreseeable future things.
2.2, epoxy molding compound
Epoxy molding compound in the country in recent years, rapid growth, product demand. 2000 annual output of 5,500 tons to 6,000 tons, Warwick Electronics Group Co., Ltd. Lianyungang only one to achieve sales of 3,500 tons. The company's main products include six series, 89 varieties, most of which can meet 1μm ~ 3μm IC packaging needs, KL-4000-type plastic material can be used to 0.8μm ~ 1.0μm integrated circuit packages. Epoxy molding compound is currently the world's annual output has more than 100,000 tons. Domestic production of the material has seven major manufacturers, including two owned enterprises, state-owned enterprises 2, the other three. Domestic manufacturers EMC profile as shown in Table 4 (4). In EMC-based plastic packaging accounts for about 91% of the entire package, the widespread concern in the industry. 2001 accounted for 90% by plastic material of the entire package is calculated, and with each integrated circuit EMC3 grams, each discrete calculated using EMC0.35 grams, the IC with EMC to 6000 tons, discrete devices with EMC for 4200 t a total of 10,200 tons. Based on projections, EMC domestic demand in 2002 will reach 14,000 tons to 18,000 tons. The current production level of domestic EMC is able to meet the basic needs of 0.3μm technology development level is used to 0.35μm package, initially formed a local plastic materials industry, breaking the dominance of foreign companies.
Epoxy is an important raw material for the production of epoxy molding compound, with the development of electronic packaging industry, its rapid increase in demand, its performance has a significant impact on the quality of epoxy molding compound. Features abroad epoxy industry are: ① large capacity, highly concentrated production scale. ② supporting the work well done. ③ varieties grades serialization, fine, functional and high purification. Former world ranking manufacturer of epoxy resin 5 as shown in Table 5. Before 2000, domestic package with epoxy basically rely on imports, the price is very expensive, which hinders the development of China's packaging industry to some extent. With Tianjin Petrochemical (ethylene) joint venture production of epoxy resin and other enterprises, with an annual production capacity of domestic epoxy resin greatly improved. At present, China has more than 170 epoxy resin producers, with a total production capacity of 150,000 tons, of which the first five industries accounted for more than 50% of the productivity of production capacity, capacity utilization is about 50%. 2001 Chinese epoxy resin production pattern as shown in Table 6 (5).
Epoxy molding epoxy resin performance requirements are: ① has excellent chemical stability, corrosion resistance. ② good electrical insulation properties. ③ good adhesive properties, and high mechanical strength. ④ high purity, volatile matter, low impurity content. ⑤ hydrolysis rate, the content of Na and Cl ions should fall to around 1 × 10-6. There are four kinds of epoxy resin commonly used types, namely phenolic type (ECN), biphenyl, ferrocene type (DCPD) and naphthalene. ECN resins are amorphous at room temperature, in a temperature range above the softening point, high melt viscosity, and thus poor in fluidity during molding, is difficult to fill excess inorganic material. Biphenyl type resin in a crystalline state at ordinary temperature, the melting point of up to 105 ℃, has a very low melt viscosity. DCPD resin curing agent has a very low density of the bridge (for the ECN resin is 1/4), and therefore a low absorption rate (of 10% ECN resin), good heat resistance. Naphthalene-type resin having a high adhesive force "skeleton" type structure, low moisture absorption resin. In order to meet the future requirements of plastic materials for electronic packaging, the future should vigorously develop high-quality new resins, such as o-cresol novolac epoxy resin, biphenyl type epoxy resin, a bicyclic diene garrison low viscosity epoxy resin.
3, ceramic packaging materials
Ceramic package belongs hermetic package, the advantages of this package are: ① moisture is good, not easy to produce micro-cracking phenomenon. ② injury does not produce thermal shock test and temperature cycling test, high mechanical strength. ③ thermal expansion coefficient, high thermal conductivity. ④ air tightness, chips and circuits from the environment around it. So it is suitable for aerospace, military works with a highly reliable, high-frequency, high-temperature, gas-tight and strong product package. At present, although the proportion of small ceramic package encapsulates the entire industry, but it is fairly complete performance package. In demanding sealing of the occasion, the only only use a ceramic package. According to reports, within power 30W, ceramic package is the best choice. Therefore, ceramic packaging materials impressive.
3.1 Overview of the ceramic package
Japan ranks first in foreign ceramic package, Japan accounted for 90% to 95% of the US ceramic package of the market, accounting for 95% to 98% of the US defense market ceramic package. Japan NTK ceramic company, SMI companies and KyoceraInternational companies, three ceramic package company a virtual monopoly on the US electronic weaponry with ceramic package IC and discrete devices market. The mid-1990s, the US government ordered the defense electronic systems allow only purchased 25% of ceramic packages, the rest should be resolved by domestic companies. Abroad for high-density, highly integrated ceramic packaging materials typical of the products are produced by the Japanese company Kyocera black ceramic powder A440, white ceramic powder A473.
Ceramic shell of IC production plant currently there are three: Yixing electronics plant, Fujian Nanping, Fujian flights electronics company and the China Electronics Technology Group Corporation No. 13 Research Institute, which has three production lines imported from abroad, using cast technology to produce ceramic quad flat package (CQFP), leadless ceramic chip packages (CLCC), pin array ceramic package (CPGA) and other products. CPGA can produce 44-pin to 257-pin series, CQFP lines to 160 lines can produce 44 series. Annual production capacity of the plant in Yixing plant and Nanping are 1.3 million sets.
3.2, ceramic packaging materials
High-density, gas-tight ceramic package of the main requirements of ceramic packaging materials are: thermal expansion coefficient, high thermal conductivity, moisture resistance. Ceramic package materials are Al2O3, BeO, SiC, Si3N4, etc., they are shaped, the assembly after the production of the sintered shell. Several characteristics of the ceramic package used as shown in Table 7.
(1) Al2O3 ceramic
Traditional ceramic packaging material is Al2O3 ceramic component from 85% to 99.9%. With increasing content of Al2O3, the thermal conductivity increases. Some materials can be doped to meet the specific needs of the package. Advantages Al2O3 ceramic is a good insulating properties, good chemical stability and mechanical properties, low price, and thus is the main ceramic packaging materials. The major domestic manufacturers of Al2O3 ceramic material Zhengzhou Aluminum Plant, 772 state-owned factory in Nanjing, Chengdu, 715 state-owned factory, Yixing Electronic Equipment Factory.
(2) SiC ceramics
Table 7 shows that the ceramic sealing material in several high thermal conductivity of SiC, Al2O3 is 13 times the thermal expansion coefficient is lower than Al2O3 and AlN. However, the high dielectric constant of SiC, AlN is 4 times, it is only suitable for low-density packaging and not suitable for high density packaging.
(3) AlN ceramics
AlN ceramics is the most promising international experts packaging materials. AlN is a Ⅲ-V compound having a wurtzite structure, which is close to the SiC has a high thermal conductivity, thermal expansion coefficient is lower than Al2O3, a breaking strength greater than Al2O3, which is half the Vickers hardness of Al2O3. Compared with the same Al2O3, AlN low density so that the weight is reduced by 20%. The method of manufacturing AlN package, there are two (6): ①Al2O3 carbon thermal reduction method, the reaction is: Al2O3 + 3C + N2 = 2AlN + 3CO② aluminum nitride directly. Compared to the thermal reaction of carbon with the direct nitridation reaction of AlN powder particle size distribution is wide, a larger average particle size. Usually at about 1800 ℃ AlN sintered in a nitrogen atmosphere. Y2O3 or CaO to obtain a sintering aid of oxygen from the surface of the AlN or lattice, is formed in the liquid at the grain boundary triple point grain boundary phase (Y-Al-O, or Ca-Al-O), or migrate to the surface of the AlN sintered body. This promotes grain growth of AlN and densification, and can prevent oxygen atoms from diffusing into the AlN crystal grains, so that an effective method of up 200W / m · K than the thermal conductivity can be achieved. In the case of added components and no added ingredients hot press sintering AlN, thermal conductivity rates with increasing oxygen content of the raw material powder is decreased (7), so that the oxygen content of the raw material powder is not more than 1%.
Because of AlN packaging material has many excellent properties, attention at home and abroad encapsulated community. The material was first developed in Japan that, the most mature technology, 1983, developed a thermal conductivity of 260W / m · K of the AlN package substrate material. The current production of AlN powder mainly Japanese companies have KYOCERA, NTK, Tokuyama Soda Co., Toyo Aluminium, Denki Kagaku Kogyo, Mitsui Toatsu Chemicals. Japan is developing AlN ceramic package companies Tao Jing, special pottery industry in Japan, Sumitomo Metal Industries, Fujitsu, Toshiba, NEC, etc. Domestic AlN ceramic packaging materials manufacturers are: 715 state-owned factory in Chengdu, China Electronics Technology Group Corporation No. 43 Research Institute, the Institute of Building Materials Academy special ceramics, electronic equipment plant in Yixing, Jiangsu, Nanjing Institute of Chemical Technology, Wuxi Microelectronics Research Center . 2001, domestic production of AlN, Al2O3 ceramic powder about 1200 tons, in short supply in the packaging market.
4, metal packaging materials
Metal packaging features are: encapsulation shell can and certain components (such as hybrid integration of A / D or D / A converter) for the integrated, diverse shapes can package, fast heat dissipation, small size and low cost. When metal package, the package would be according circuits or devices such as transmission delay, crosstalk, thermal requirements of the rational design package structure, size and reasonable choice of packaging materials. Most used metal in the package material is copper, aluminum, Kovar and copper tungsten, copper and molybdenum alloys. The main characteristics of metal packaging material such as shown in Table 8. As can be seen from Table 8, a high thermal conductivity Cu, Al being the lowest CTE of Kovar, which are matched in terms of thermal and dominant; CuMo alloy and a CuW alloy has a high thermal conductivity and to match the CTE However, their high density, it is not suitable for the weight of the required applications, especially portable electronic packages today's popular products. Metal packaging shapes are round, diamond-shaped, flat plate-shaped, shallow cavity and deep cavity and so on. The main step is to design metal packaging, machining, testing, pre-processing, shipping, melt sealing, testing, post-processing.
Engaged in domestic metal packaging material manufacturers have radio equipment factory in Wuhan, China Electronics Technology Group Corporation No. 24 Research Institute, China Electronics Technology Group Corporation No. 43 Research Institute, China Electronics Technology Group Corporation No. 44 Research Institute. Among them, the radio equipment factory in Wuhan is the largest hybrid circuit with a metal shell packaging factory, China Electronics Technology Group Corporation No. 24 Research Institute launched a package with aluminum hybrid high-resolution high-speed A / D converter development work.
5, AlSiC metal matrix composite packaging materials
The rapid development of hybrid integrated circuit technology, packaging material made of newer and higher requirements, the traditional packaging materials challenges. In fact, there is no single material can also have a low CTE, high thermal conductivity, low price, simple processing advantages, it is difficult to meet today's aerospace, ships and radar power, small size, light weight, portable requirements of the electronic module. Therefore, in order to keep pace with the development of advanced hybrid circuits, we must vigorously develop metal matrix composites. Currently, the US company has developed a new type of AlSiC CPS metal matrix composite (MMC) packaging material (8), which has a high thermal conductivity, low CTE, low density, low cost, etc., but also in the process of the AlSiC, such as insulators, sealing ring and the base can be hermetically packaged together with high reliability, thus making it an ideal packaging material sheet having a Si or GaAs power chips advanced hybrid microcircuit. Common packaging materials and AlSiC properties of the metal matrix composite material as shown in Table 9. Comparative. Table 9 can be seen from AlSiCMMC thermal conductivity higher than that of Al2O3, and AlN fairly; CTE lower than Cu, Al; flexural strength ranking first in several packaging materials.
AlSiCMMC osmotic pressure by the molten aluminum metal into the preform to the special production of SiC, which is composed of a continuous and a discontinuous aluminum SiC particles. This composite material is very dense, void-free, is an excellent hermetic packaging material (9). This material combines the advantages of each of Al and SiC, SiC whose characteristics depend on the nature of the content, particle size distribution and the Al metal. General SiC content in packaging applications accounted for 50% to 68%. In this range of performance and price than the best.
6. Prospects
Into the 21st century, the microelectronics packaging industry will be more rapid development of network applications will become the new driver chip packaging technology, array technology will gradually replace the perimeter wire technology, MCM will develop in the direction towards a more intensive, MEMS packaging technology will become new highlights. With the development of microelectronics packaging industry, electronic packaging materials will become a high technological content, good economic returns, has an important position in the industrial sector, there are broad prospects for development.
(1) for a long period of time, electronic packaging materials will continue to plastic materials for the mainstream, it will be to the series, fine, matching direction. Low stress, low α-rays, low viscosity, high adhesion, environmentally friendly epoxy molding compound will be the best-selling product on the market. Dedicated polyimide resin as the main component of plastic material is a promising electronic packaging materials.
(2) In the field of military integrated circuits and surface acoustic wave devices, crystal oscillator components, optoelectronic devices, ceramic packaging materials has great room for development, it will develop in the direction of multi-layered. Reliability, flexibility, low development costs of multilayer ceramic package housing is the focus of development. AlN as a high thermal conductivity, high sealing material has great potential for development, can replace SiC, even partially replace Al2O3, in order to further broaden the scope of its application, should strive to break through the selection and amount of additives, the sintering temperature, powder particle size, oxygen content control and other key technologies.
(3) With the microelectronic packaging technology significantly towards the development of SMT and MCM, many single packaging materials currently in use has been difficult to meet the requirements of high-density packaging must be another way priority to the development of new composite materials. Electronic packaging materials will be composite development.
