| With the extensive applications of 4G communication and putting forward of 5G communication,mobile communication technology and mobile communication equipment have undergone enormous changes.The frequency and rate of transmission signal have been improved constantly,that requires the fine line in printed circuit board of mobile communication facility with regular shape and smooth surface.Meanwhile the density of fine line in printed circuit board has to increase as the volume of mobile communication equipment continues to decrease and number of I/O interface in semiconductor device continues to rise.In order to adapt to the demand of printed circuit boards caused by the development of the mobile communication,manufacturers of printed circuit board must continuously improve the production technology of fine lines fabrication.In this paper,parameters of etching process are optimized by orthogonal experiment.Etching factor and the lateral etching amount are used to be experimental index of orthogonal experiment,while thickness of resist,the thickness of the copper and spraying pressure etching liquid are taken to be experimental factors.The best parameters of etching process in subtractive are obtained by orthogonal experiment.Fabricated under the optimum parameters,the maximum etching factor of fine line is 4.90,and the minimum lateral etching amount is 1.98?m.It is shown that the fine line fabricated with subtractive can satisfy the requirement of 4G communication.But with the advent of 5G communication,the width of fine line in printed circuit board is below 35 microns which make it necessary to put forward a new fabricating method for printed circuit board industry.Among the three fabricating methods of fine line,semi-additive is the most appropriate way for the production of mobile communication printed circuit board with high density fine line.However there are still some disadvantages about semi-additive.Such as the binding force between the seeder layer deposited by electroless copper and the insulating base produced with epoxy resin is very poor.To a certain extent,it can be improved by depositing the seeder layer with magnetron sputtering.But it cannot be applied widely as the high cost and low efficiency.To solve the problem,a new semi-additive is put forward by depositing seeder layer with electroless nickel.The deposition rate of electroless nickel plating has a significant impact on production efficiency,so the single factor experiment is used to optimize the parameters affecting the rate of deposition in electroless nickel plating.According to the experiment,the best concentration of nickel sulfate is 25g/L,the best concentration of reducing agent is 35g/L,the p H of plating solution is 8.5 and the best temperature is 85?.Among two types of dry film,SZ-1235 dry film produced by DuPont is selected as the plating resist dry film.According to experiment,the suitable current density is 0.8A/dm2 and the suitable electroplating time is 120 min.The thickness of seeder nickel layer is 2?m and etching time of nickel layer is 2min.After the correct parameters are determined,the fine line is fabricated by new semi-additive.Then the metallographic microscope,scanning electron microscope and peel strength test are used to test the quality of fine line.It is found that the surface of fine line is smooth,the shape of the cross section of fine line is very neat and the etching factor which can reach more than 8 of line is very high.Through peel strength test it is found that the binding force between line and the substrate is strong and the results of peel strength test of fine lines meet the quality requirements of IPC(Institute of Printed Circuits).The fine line fabricated in this experiment has a high etching factor and high peel strength.Compared with ordinary semi-additive and subtractive,the new semi-additive put forward in this article is obviously more suitable for mobile communication and printed circuit board production. |
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