1. Overview of inkjet circuit technology
The original origin of PCB is to make the circuit diagram of the circuit board with the printed process, but later because of the improved resolution requirements for the line, and the printing process can not meet, it is replaced by a Huang Guang microshadow process with a higher line resolution. However, in recent years, Printing technology has continued to improve, and some advanced Printing techniques such as Ink Jet Printing, Screen Printing, Flexography Printing and Gravure Printing, The resolution of line printing can be raised from hundreds of um to tens of um, and the use of printing for line production has been discussed again. The increasing emphasis on green processes in recent years is also another reason why pull-up printing is widely discussed, because the use of printing can reduce the waste of materials in the circuit production process, and can reduce the steps of the process to achieve energy saving and waste reduction. The advantages of printing technology are as follows.
1.1. process steps reduction: the circuit board line production of light resistance, exposure, development, etching and light resistance stripping steps can be reduced to print light resistance, conductor lines and insulation materials on the substrate, eliminating the use of working negatives and light masks.
1.2. reduce the use of materials: it can reduce the use of chemical agents such as photoresistance, developer, etching solution and film stripping agent, and also eliminate the disposal of waste and waste liquid in the process.
1.3. the process conversion is easy: it can be directly by computer digital processing, directly printed on the substrate, no longer with the different products and prepare the light and mold and equipment
1.4. fine line line: the PCB process capacity of the yellow light process is L/S=3 mil/3mil, the research and development capacity is 2mil/2mil, and the printed line can reach a resolution of 1mil/1mil if the materials and equipment are well matched.
1.5. low-cost process: can reduce the use of chemical agents such as photoresistance, developer, etching fluid and film stripping agent, reduce material costs, in addition, because the process steps are reduced, it can also increase the flexibility of the use of plant space.
Examples of PCB production with inkjet technology When taking EPSON as an example, EPSON uses inkjet original technology to improve, At present, CBIT(Circuit Board Innovation by Ink Jet Technology) has made ten layers on PI through its mass-produced inkjet machine with metal conductors and insulating materials, and selected COF as the first target on this basis.
2. Market overview
2.1. Market size
Whether the inkjet technology production line can be successfully applied to the production of PCB lines, the impact factors are respectively the process, cost, and material to observe.
Process: inkjet technology is still in continuous development, PCB is an industry that requires a large number of rapid production, so whether the production speed and yield of inkjet technology can be the same as the existing yellow process, or better will affect whether it can replace the yellow process in the future to become the mainstream reason.
Cost: Because inkjet technology is still developing, the current cost of materials and equipment are quite high, so the cost of materials and equipment are high, how much can be reduced in the future, will affect its ability to enter the mainstream market one of the reasons.
Materials: Whether conductive inks can work well with the equipment, including viscosity/flow and molecular weight, will not block the inkjet head, conductive ink nanometal conductor formulation, currently commercialized materials to use silver Ag materials, because copper must also overcome the oxidation problem. However, silver is a precious metal and the price is high, and whether it can reduce the cost or develop conductive pastes of nano copper will be the focus.
Because the material is made of metal powder slurry, it still needs to be sintered after the inkjet line, but also because the mixing of other substances slurry makes the metal powder evenly distributed, so there is a problem of impedance of the sintered conductor line, so the electrical conduction of too fine line will cause problems. Therefore, because of this reason, the initial can only be used in the general household appliances with single/double panels that do not emphasize fine lines.
Because of the above limitations, PCB manufacturers hesitate to use inkjet technology, but also let inkjet technology development information in the market is highly opaque, blocking the investment of manufacturers interested in inkjet technology want to try, so IEK estimates that only a few manufacturers use inkjet technology before 2012. It is used in PCB photoresist and screen printing to mark the position of other components on PCB. The use of inkjet technology for line production is only limited to research and development and the production of prototype products, and there are very few manufacturers successfully developed. The products that really want to be able to use IJP for the production of conductive lines are also mainly single and double sided soft boards and hard boards with line width 70um~100um, and the cost of line products over 100um will be produced by screen printing technology. Therefore, the PCB market made by inkjet technology is growing very slowly. It is estimated that the global market size of inkjet technology used in circuit board conductive circuit production in 2012 can reach 0.09 million US dollars, and the market size can reach 0.5 million US dollars in 2013, as shown in Figure 1. Before 2012? Most manufacturers only test products, not mass production. By 2013, inkjet technology is still only a tentative new technology for the circuit board industry, and whether it can have the opportunity to be imported into the application of a wider circuit board after 2013 still needs to rely on material characteristics, material and equipment costs and the line width and narrowness of the nozzle can be made.
3. investment ink-jet line subgrade board elements
PCB manufacturers are willing to inkjet technology for PCB production, need to consider the manufacturer's business strategy, as well as the inkjet technology itself of the material, equipment development.
3.1. Business strategy
The type of product produced by PCB manufacturers themselves will affect whether it is suitable for the introduction of inkjet line production technology, the current inkjet line to make conductor lines, is not mature enough to be mass produced, if in the next five years can be mass produced, it will also be used in low layer number, wide line, conductor impedance requirements on the product. Therefore, in the early stage of commercialization, there is more opportunity to appear on single and dual panels and RFID substrates, because the lines of these products are wider, the impedance requirements of the lines are also looser and more opportunity to cut in.
Because the speed of line production is still much slower than that of the exposure, development, and etching processes, PCB manufacturers who focus on rapid production in large numbers have no incentive to use inkjet technology, but those who have diversified products and multi-batch production have a greater incentive to use inkjet technology. Long-term observation of inkjet line technology can indeed reduce the waste in the PCB process, in order to achieve the purpose of environmental protection and energy saving, if PCB manufacturers have urgent needs for the introduction of environmental protection process, you can consider the use of inkjet line technology on the line requirements of lower products, as for the fine line is still based on the existing process.
3.2. Material development
The most important thing for the commercialization of inkjet subgrade board is the matching development of materials and equipment. Including materials using nanoscale metal powder mixed slurry, metal powder particles can not be too large so as not to block the equipment nozzle, in addition, because the metal powder slurry as a line still need to be sintered at high temperature to achieve good conductive characteristics, so considering the characteristics of the substrate itself, the metal powder needs to reach 40nm to be sintered at a temperature below 200℃. This is the temperature that the substrate can withstand.
At present, the metal powder slurry used is mainly nano silver, but silver is a precious metal, so the cost is relatively high, as for the nano copper currently used in the production of the line, because the problem of easy oxidation of copper is difficult to overcome, so there is no metal powder slurry using copper as a material.
3.3. Equipment development and investment
At present, the equipment of the inkjet line is still under development, and many are still laboratory equipment, or must sign confidentiality contracts after sale. Japanese equipment manufacturers are quite early into the development, with Japan's materials and equipment advantages jointly developed, the current inkjet line equipment according to the size of the machine is about NT $600~10 million between. With the current maturity of the equipment, as well as its degree of close cooperation with the material supplier, the use of a manufacturer's equipment must use the matching material to avoid inkjet head damage, so the current acquisition cost or material specificity is very high, and the cost is difficult to reduce in the short term.
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