Fine Circuit Manufacture And Defect Repair Of Laser Sintering Copper Nanoparticles

At present,electronic products are developing toward the trend of being lighter,thinner,shorter,and smaller.Integrated circuits are getting smaller and smaller in size,more powerful in functions,more and more pins,and faster and faster in signal transmission.The integration of chips continues to improve,and the matching chip packaging technology is also constantly evolving.Fan-out packaging technology has become a new direction of packaging technology by its outstanding advantages such as high density,low thickness,and high performance.The key to promoting the development of high-density packaging technology lies in the manufacturing level of interconnection circuits and the advancement of packaging technology.The interconnection circuit manufacturing technology has become a major technical point of current packaging technology.With the development trend of packaging and interconnection circuits in the direction of high density,high precision and fine pitch,the risk of circuit defects has increased exponentially.The yield and cost of circuit manufacturing and interconnection technologies are facing major challenges,which has become a bottleneck restricting the further development and application of new large-scale high-density interconnection technologies such as fan out package.In this paper,a new method of laser sintering copper nanoparticles for fine circuits repair at low temperature is innovatively proposed.Copper nanoparticles as prepared were used for fine circuit manufacture and open circuit defect repair through laser sintering copper nanoparticles,which provides a solution for defect repair of fine circuits and improves the yield rate of precision package interconnect manufacturing.In this paper,liquid phase reduction method was used to prepare copper nanoparticles,with copper acetate as the copper salt and ascorbic acid as the reducing agent.The effects of the concentration of copper salt and reducing agent,the addition of dispersant polyvinylpyrrolidone and different solvent systems,on the preparation of copper nanoparticles,were studied.Copper nanoparticles with different sizes and morphologies of about 50 nm,300 nm and 500 nm were prepared.Copper nanoparticles with flux were prepared into a copper paste containing 85 wt.% copper,and a structure of "upper copper plate-copper paste-lower copper plate" was made for interconnection by hot press sintering.By testing the shear strength of the sintered sample,comparing the sintering performance of different sizes of copper nanoparticles and copper paste with different fluxs,a copper paste was developed with good sintering performance and shear strength of 75 MPa at 300?+2 MPa sintering condition.The copper paste coated on the polyimide substrate was selectively sintered by a 355 nm ultraviolet nanosecond pulsed laser.The effect of laser scan rate,repeated scan,and laser power on the morphology and performance of the sintered circuit were studied,and the lowest line width of30 ?m was fabricated.The sintered circuit was cleaned by organic solvent,hydrogen peroxide and dilute sulfuric acid,and the effect of different cleaning methods on the sintered circuit was characterized by Energy Dispersive Spectrometry.On the basis of laser sintering copper nanoparticles circuit manufacture,taking the open circuit repair of polyimide organic substrate as an example.The copper paste was coated on the open circuit position and sintered with appropriate laser process parameters to complete the line width 0.1 mm metal copper fine circuit repair application,and the reliability of the repaired circuit was characterized and analyzed.