Interaction Between Polymer And Laser (Ⅲ) Manufacture Of Fine Circuit On Polyimide Film By Selective Electroless Plating Using Silver As Seeding

With the development of microelectronic industry, new techniques are urgently required to lower the pollution, simplify and the producing process of electronic circuit, and miniaturize the products. Electroless plating is widely used because it is a relatively low-cost technique, can be applied on non-metal substrates, and can be operated at room temperature with relative simple equipment, and can also obtain the uniform and thick deposited metal. If laser technique was introduced to electroless plating process, the procedure would be simplified, and the deposited metal patterns, which can be designed and controlled by computer, would be produced without mask.Polyimide is a low dielectric constant (low-k) material with high electric insulation, good tightness, high thermal stability, and high mechanical property, and Cu-based metallization on polyimide can reduce the RC delay time, so polyimide has been widely used in microelectronic industry. The key step in electroless deposition process is the activation or seeding on the dielectric substrate prior to metal plating. The conventional activation solutions such as Pd colloid are expensive and pollutional, so it is necessary to find the substitutes for them. Compared with aurum, palladium and platinum as seeds, Silver is much cheaper and lower pollutional and can also activate electroless plating, although it is still rarely investigated. We used Ag to seed polyimide and developed four different techniques of laser-induced electroless plating to selective metallization on polyimide surface. These techniques provided new approaches on fabrication of micro-scale metal circuit on flexible film, and have potential applications in microelectronic industry. The content of this dissertation could be summarized as follows:1. Polyimide was patterned by direct laser writing, then the patterned polyimide was immersed in silver diammine solution for seeding. The silver particles were deposited in-situ at the irradiated areas on polyimide films, whose particle size was 150-300nm. Finally patterned copper was electrolessly deposited on polyimide using the Ag particles as seeds. The mechanism of the deposition of Ag particles was proposed. We deduced that Ag(NH₃)₂⁺ reacted with the dangling bonds, such as free radicals, or reducing functional groups produced by laser ablation, so Ag particles were generated and deposited in situ. More Ag particles were deposited on the edges of the tracks than those at the center of the tracks. Laser fluence and rinsing process had influence on the morphology and selectivity of the deposited copper respectively.2. Ag particles were generated on Ag+ doped polyimide film by laser direct writing, followed by selective copper deposition using the metallic silver particles as seeds. The process was characterized by ATR-FTIR, EDS, AFM, XPS, and Contact Angle meter. Laser irradiation caused in-situ reduction and agglomeration of silver on the polyimide film. The particle size of Ag particles ranged from 120 nm to 200 nm. Meanwhile, the Ag particles arranged parallel to the laser writing direction. Laser fluence and scanning velocity had influence on the morphology and connectivity of the deposited copper line respectively. Equations of the relationship between scanning velocity and connectivity of the deposited copper patterns have been proposed.3. The self-assembly monolayer of dodecanethiol was formed on Ag nanoparticles/PI film which was produced by anneal treatment on Ag+ doped polyimide, The desired micro-scale patterns was generated on the film by laser direct writing and copper was then selectively deposited on the pattern areas by electroless plating. Chemical and physical properties of the Ag nanoparticles were characterized by XPS and AFM, and the result showed that the particle size of the metallic Ag nanoparticles was about 35nm. Formation of the self-assembly monolayer was confirmed by contact angle meter and ATR-FTIR, and it showed that the equilibrium contact angle on the PI surface was increased to 128.0±1.9°after the self-assembly monolayer was successfully formed. The electrolessly deposited copper was uniform and compact.4. Laser printer was used to mask polyimide for patterned electroless copper deposition. Polyimide film was printed with picture drawn by software, and then the film was chemically treated and selectively activated to bond with patterned Ag+ ions. Finally copper was selectively deposited on polyimide film through electroless plating.5. Ag nanoparticles were generated from PVP/AgNO₃ colloid coated on polyimide by laser irradiation, and the Ag nanoparticles was used as seeds to induce selective electroless plating on polyimide and form patterned copper deposition. Laser fluence and the mass ratio between PVP to AgNO₃ had influence on the morphology of the Ag nanoparticles, respectively. The influence of scanning velocity on the morphology and connectivity of the deposited copper line was also analyzed by the equations we proposed.