The rapid development of electronic information industry makes electronic products develop in the direction of miniaturization, functionalization, high performance and high reliability. From the general surface mount technology (SMT) in the mid-1970s to the high-density interconnect surface mount technology (HDI) in the 1990s, and the application of various new packaging technologies such as semiconductor packaging and IC packaging technology in recent years, electronic installation technology continues to develop in the direction of high density. At the same time, the development of high-density interconnection technology promotes the development of PCB to high-density. With the development of mounting technology and PCB technology, the technology of copper clad laminate as PCB substrate material is also improving.
Experts predict that the world electronic information industry will grow at an average annual rate of 7.4% in the next 10 years. By 2020, the market scale of the world electronic information industry will reach US $6.4 trillion, including US $3.2 trillion for complete electronic machines, of which communication equipment and computers will account for more than 70%, reaching US $0.96 trillion. It can be seen that the huge market of copper clad laminates as electronic basic materials will not only continue to exist, but also continue to develop at a growth rate of 15%. Relevant information released by the copper clad laminate industry association shows that in the next five years, in order to adapt to the development trend of high-density BGA technology and semiconductor packaging technology, high-performance thin FR-4 and high-performance resin substrates will increase.
Copper clad laminate (CCL), as the substrate material in PCB manufacturing, mainly plays the role of interconnection, insulation and support for PCB, and has a great impact on the signal transmission speed, energy loss and characteristic impedance in PCB. Circuit. Therefore, the performance, quality, manufacturing technology, manufacturing level, manufacturing cost, long-term reliability and stability of PCB copper clad laminate largely depend on the material of copper clad laminate.
Copper clad plate production technology has experienced more than half a century. At present, the global annual output of copper clad laminate has exceeded 300 million square meters, and copper clad laminate has become an important part of the basic materials of electronic information products. Copper clad laminate manufacturing industry is a sunrise industry. With the development of electronic information and communication industry, it has broad prospects. Its manufacturing technology is a high-tech with multi-disciplinary intersection, penetration and promotion. The development of electronic information technology shows that copper clad laminate technology is one of the key technologies to promote the rapid development of electronic industry.
China’s copper clad laminate (CCL) industry is the key task of the future development strategy. In terms of products, efforts should be made on five types of new PCB substrate materials, that is, through the development and technological breakthrough of five types of new substrate materials, The cutting-edge technology of copper clad laminate in China has been improved. The development of five types of new high-performance copper clad laminate products listed below is a subject that engineers and technicians in China’s copper clad laminate industry should focus on in the future research and development.
1. PCB substrate material lead-free compatible copper clad laminate
At the EU conference on October 11, 2002, two “European directives” with environmental protection content were adopted. They will formally implement the resolution on July 1, 2006. The two “European directives” refer to the “waste of electronic and electrical products directive” (WEEE) and the “restrictions on the use of specific hazardous substances” (RoHS). In these two statutory directives, requirements are explicitly mentioned. Lead containing materials are prohibited. Therefore, the best way to deal with these two directives is to develop lead-free copper clad laminates as soon as possible.
2. PCB substrate material – high performance copper clad laminate
The high-performance copper clad laminate mentioned here includes low dielectric constant (DK) copper clad laminate, high-frequency and high-speed PCB copper clad laminate, high heat-resistant copper clad laminate, and various substrates for multilayer boards (resin copper clad foil, organic resin film forming the multilayer board insulation layer, glass fiber reinforced or other organic fiber reinforced prepreg, etc.). In the next few years (to 2010), when developing this type of high-performance copper clad laminate, it is predicted that the development of electronic installation technology in the future should reach the corresponding performance index value.
3. PCB substrate material – substrate material of IC packaging carrier
The development of substrate materials for IC packaging substrate (also known as IC packaging substrate) is a very important topic at present. It is also urgent to develop IC packaging and microelectronic technology in China. With the development of IC packaging towards high frequency and low power consumption, IC packaging substrate will be improved in important properties such as low dielectric constant, low dielectric loss factor and high thermal conductivity. An important research topic in the future is the substrate thermal connection technology – effective thermal coordination and integration of heat dissipation.
In order to ensure the freedom of IC packaging design and the development of new IC packaging technology, model test and simulation test are essential. These two tasks are of great significance for mastering the characteristic requirements of IC packaging substrate materials, that is, understanding and mastering their electrical performance, heat dissipation performance, reliability and other requirements. In addition, we should further communicate with the IC packaging design industry to reach a consensus. The properties of the developed substrate materials will be provided to the designers of complete electronic products in time, so that the designers can establish an accurate and advanced data base.
IC packaging carrier also needs to solve the problem of inconsistency with the thermal expansion coefficient of semiconductor chip. The thermal expansion coefficient of the insulating substrate is generally too large (the general thermal expansion coefficient is 60ppm / ℃). The thermal expansion coefficient of the substrate reaches about 6ppm, which is close to that of the semiconductor chip, which is really a “difficult challenge” for the manufacturing technology of the substrate.
In order to adapt to the rapid development, the dielectric constant of the substrate should reach 2.0 and the dielectric loss factor can be close to 0.001. Therefore, it is expected that a new generation of printed circuit boards beyond the boundaries of traditional substrate materials and traditional manufacturing processes will appear in the world around 2005. Base material.
In order to predict the future development of IC packaging design and manufacturing technology, there are more strict requirements for the substrate materials used. This is mainly reflected in the following aspects:
1. High Tg corresponding to lead-free flux.
2. Achieve low dielectric loss factor matching with characteristic impedance.
3. Dielectric constant corresponding to high speed（ ε It should be close to 2).
4. Low warpage (improve the flatness of the substrate surface).
5. Low moisture absorption.
6. The coefficient of thermal expansion is low, making the coefficient of thermal expansion close to 6ppm.
7. The cost of IC packaging carrier is low.
8. Low cost substrate material for embedded components.
9. In order to improve the heat shock resistance, the basic mechanical strength is improved. It is suitable for substrate materials that do not reduce performance under the temperature change cycle from high to low.
10. Green substrate material with low cost and suitable for high reflow soldering temperature.
4、 PCB substrate material copper clad laminate with special functions
The copper clad laminates with special functions mentioned here mainly refer to metal based (core) copper clad laminates, ceramic based copper clad laminates, high dielectric constant laminates, copper clad laminates (or substrate materials) – type multilayer boards for embedded passive components, copper clad laminates for optoelectronic circuit substrates, etc. The development and production of this kind of CCL is not only the need of the development of new technology of electronic information products, but also the aerospace and military industry of our country.
5、 PCB substrate material high performance flexible copper clad laminate
Since the large-scale industrial production of flexible printed circuit board (FPC), it has experienced more than 30 years of development. In the 1970s, FPC began to enter the truly industrialized mass production. In the late 1980s, due to the emergence and application of a new kind of polyimide film materials, FPC is an adhesive free FPC (generally referred to as “two-layer FPC”). In the 1990s, the world developed a photosensitive covering film corresponding to high-density circuits, which led to significant changes in FPC design. Due to the development of new application fields, the concept of product form has changed a lot and has been extended to include a wider range of tab and cob substrates. The high-density FPC appeared in the second half of the 1990s and began to enter large-scale industrial production. Its circuit pattern has rapidly developed to a more subtle level. The market demand for high-density FPC is also growing rapidly.
At present, the annual output value of FPC produced worldwide has reached about US $3 billion to US $3.5 billion. In recent years, the global output of FPC has been increasing. Its proportion in PCB is also increasing year by year. In the United States and other countries, FPC accounts for 13% – 16% of the output value of the whole printed circuit board. FPC is increasingly becoming a very important and indispensable variety in PCB.
In terms of flexible copper clad laminate, there is a large gap between China and advanced countries and regions in terms of production scale, manufacturing technology level and raw material manufacturing technology, which is even greater than that of rigid copper clad laminate.
