| The developments of integrated circuit(IC) of high integration and high density, and digital signal transmission of high frequency and high speed require PCB along the development direction of smaller and lighter. Embedded resistors technology can save a lot of packaging surface of PCB, thereby increasing PCB routing flexibility and integration density. Therefore, embedded resistor technology will become the mainstream packaging technology in the future.The paper mainly introduces technology of manufacturing embedded resistor by carbon paste screen printing method.Focuses on how to optimize the process parameters, thus can control the stability of resistance of embedded resistors. The paper also introduces preliminary study on electroless Ni-P, and obtained some basic rules and initial process methods. While producing embedded resistors by this method, prone to problems and put forward possible solutions.The study on fabrication of embedded resisitors by carbon paste screen printing is major factors that affect ink volume of carbon paste screen printing. The process parameters of embedding resistors by carbon paste screen printing method are optimized by using orthogonal optimized design method. Compare to the advantages and disadvantages of carbon paste sreen printing resistors when using 61T and 120T sreen, discussing the impact of pickling and lamination to the resistance. Experimental results show that carbon paste ink must be tested before manufacturing embedded resistors, in order to determine the actual sheet resistance of carbon paste ink and the impact of actual operating conditions to resistance; the scrape printing pressure and scrape printing speed of the scraper are the main factors which influence carbon paste resistors, but curing temperature and time are the secondary factors; when using 120T screen, the surface and edge of the resistors are better than using 61T screen. Pickling makes resistor change smaller, but lamination makes resistor change greatly. Finally in the paper embedded resistors are carried out constant temperature and humidity reliability test.Electroless Ni-P method is mainly studied on the following some aspects. We study the eletroless Ni-P reaction rate on the different substrate, and analyze the reasons that affect reaction rate. We compare with the coating bond strength of three different roughing methods of plasma etching, alkaline potassium permanganate etching and PI adjustment agent micro erosion, and discuss when pH is different, electroless Ni-P reaction rate and sheet resistance of the Ni-P plating. Experimental results show that plasma etching roughing method not only meets reqiriement of coating adhesion, but also operation is simple and does not pollute the environment; With the decrease of pH, the reaction rate slows, but coating sheet resistance increase gradually. When pH are 3.7 and 3.4, electroless plating time is 3min~10min, the thickness of the coating can be controlled between 0.100μm~0.400μm, and coating sheet resistance can be controlled between 15~200Ω/□. Finally, preliminary attempt of embedding resistors are studied in the paper, the experimental study shows that when manufacturing embedding resistors, due to different electroless Ni-P reaction rate on the copper layer and substrate surface, which causes poor contact between copper wire and coating.In the paper, the two manufacturing methods of embedded resistors are compared. The resistors which are produced by two different methods are uses in the different occasions and fields, there are own advantage and disadvantage. However, no matter what the embedded embedded technology, with the highlight of the limitation of the SMT packaging technology, and PCB along the development direction of "light, thin, short and small" and multifunction, embedded resistor packaging technology will welcome to flourishing development opportunity. |
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