Laser-induced Transfer Of Cu-sn Single Imc Film And Interfacial Behavior Among IMC Copper And TIN Film

With the rapid development of Integrated Circuit(IC) technology, electronic products tend to become smaller, faster, and thinner. To fit the tendency, the solder joints are becoming smaller and the proportion of IMC(Intermetallic Compound) in solder joints is becoming higher. As a result, solder joints will be fully made up of IMC, even single IMC may appear. Single IMC solder joints have their own excellent properties as compared with traditional solder joints. It is important to study the rapid fabrication of single IMC solder joints with controllable microstructures.In this work, the parameters of tin electroplating on copper substrate were discussed and the research of Cu-Sn multilayer film fabrication by electroplating was also investigated. After that, single IMC film(Cu3Sn) was made on one surface of quartz substrates. Laser-induced forward transfer(LIFT) technology was used to transfer the IMC film from quartz substrates to receiver substrates. Then the factors which will influence the surface topography of transferred spots were studied, including single pulse power, location of focus plane, and so on. Simulation results of the film’s temperature field when the film was irradiated by a laser pulse were obtained. The IMC film was transferred to a Cu substrate or a Cu/Sn film to form a Cu/Cu3Sn/Sn structure or a Cu3Sn/Sn/Cu structure by LIFT. After that, the interface behavior of two structures was studied after annealing reaction, which can provide technical basis for using the LIFT to manufacture single IMC joints rapidly.The results indicated that a IMC film has been successfully made by annealing reaction at 300 ℃ for 0.25 h after preparation of Cu layer by magnetron sputtering and Sn layer by electroplating on quartz substrate. Appropriate increase of annealing time can reduce the cracking tendency of the film from quartz substrates because of the internal stress releasing. However, Using electroplating to manufacture Cu-Sn multilayer film will bring many defects to multilayer film as well as uncontrollable thickness of the Cu layer. Experiment results has shown that single pulse power, focal plane position, the space between two substrates and pulse width are important factors which will determine surface topographies of the transferred IMC spots. Due to the uneven distribution of Gaussian laser energy, it will be easy to get "crater" transferred spots. When laser power is increased, crater transferred spots will also be easily formed;When distance between laser focus plane and the Cu/quartz substrate interface is increased, energy distribution of the Gaussian laser will be more uniform, and the thickness of transferred spots will be more uniform; Uniform transferred spots can be obtained by controlling the laser power and distance between laser focus plane and theCu/quartz substrate interface; When laser power is increased, the sizes of transferred spots will increase; When distance between laser focus plane and the Cu/quartz substrate interface is increased, the sizes of transferred spots will increase at first and then decrease; The heat diffusion occurs in long-pulse LIFT and the IMC film is mainly transferred in the form of molten and solid state. XRD and EDS results indicated that phase composition of the film has not changed after LIFT treatment. ANSYS simulation results of film’s temperature field have indicated that increased the laser power and irradiation time will make temperature gradient rise, and increased distance between laser focus plane and the Cu/quartz substrate interface will make the temperature gradient decrease, which are in agreement with the experiment results. A Cu/Cu3Sn/Sn structure has been transformed into a single IMC layer without pressure after annealing reaction. Though there was an oxidation layer within the IMC layer after annealing reaction, the oxide layer bonded well with the IMC. A Cu3Sn/Sn/Cu structure has been transformed into a single IMC layer after annealing reaction. The transferred IMC film has combined well with the new generated Cu3 Sn layer in partial area without any pressure.