Research On Inner Short Problem And Its Control Strategy In The PCB Technology

Printed Circuit Board (PCB) is one of the main parts of the electronic products and isthe carrier of the electronic components. During producing, the inner layer short is themain reason which causes the reject. With the development of the electronicmanufacturing technology, the average layer of PCB products is increasing rapidly and thestructure becomes complicated, which make the inner layer short much more serious. Thisis the major block restricting the development of the high-tech PCB. For this reason, it ismeaningful to study the causing mechanization of the inner layer short and offer thesolutions to solve this problem.This paper studies the main reasons that cause the inner layer short and proposessolving methods, which can optimize processes and save the costs.The deformation of film can be affected by precondition duration, storageenvironment and exposure time. After the study, we find that the dimension deformationof black film accesses to a standard value when lay up more than24hr before plotting.After plotting, the size of black film in9hr turns to be lengthening. The size of film can beaffected by the temperature and humidity and the appropriate storage environment isdefined in this paper. We also find that100mm Kodak black film contracts0.00724μmafter exposure once on fully-automatic exposure machine, which can help us monitoringthe deformation of the film.The deformation of inner core is measured and analyzed by2D measurementinstrument and X-Ray target-shooting machine in the paper. The investigation of factorsinclude the baking sheet time, the residual copper rate and the structure, which provide thereference for the engineer to obtain more accurate film compensating factor in theengineering practice of multilayer board. It is observed that for ordinary symmetrystructure board, baking after board cutting shows little impact on deformation. It alsofound linear relationship between residual copper rate and shrinkage, the lower theresidual copper ratio, the greater the shrinkage. And the sizing rule of several speciallaminated structures is summarized. What’s more, a calculation model for shrinkage is proposed, and the result is consistent with the actual value when use it to calculate theinner sizing of a six-layer board.The impact of drilling parameters and materials on wicking is discussed usingexperimental design optimization. The optimum drilling parameters of two kinds ofmaterials with different aperture are given respectively. It is found that we can increasemanufacturing efficiency with cost neutrality by promoting the feeding speed and theretracting speed of the0.25mm and0.3mm drills ten percent. We also find that the lengthof wicking can be reduced twenty percent by increasing the rotating speed of the0.3mmdrill from115kr/min to135kr/min.