Research About Laser Technology In Applications Of Windows And Fine Lines Of Rigid-flex PCB

The development direction of electronic products is miniaturization, which put forward higher request to the size of components electronic system and connection method. Rigid-flex Printed Circuit Board(Rigid-flex PCB) is a hybrid construction containing the elements of both rigid and flexible circuit technologies, can offer supportive function and achieve local bending, and greatly reduce the weight and volume of electronic products, not only provides for the electronic system excellent stable interconnection, and more versatility and reliability than other methods, so it is widely used in encapsulation field of electronic products.During the Coverlay lamination process of FPC, the binding force of the Coverlay of FPC were evaluated, the Uniform design method was applied to data processing, and the quadratic polynomial model between four factors and the binding force of the Coverlay were formed. The results showed that the optimized parameters were preloading time of 5s,lamination temperature of 194℃,forming time of 104 s, pressure of fast-laminating of 60 Kg/cm2, under the circumstances, the result of binding force of Coverlay is 5.31N/cm.FR-4 glass-epoxy material without cladding copper foil was cut to form the rigid-flex PCB opening-area by 355 nm UV laser. Cut width and cut depth of glass-epoxy material were observed by metallographic microscope. The results showed that the cut width and cut depth of the glass-epoxy material was gradually increased with the increase of the laser power, but the cut width and cut depth was gradually reduced with the increase of the cutting speed, while cutting speed had little effect on the cut width, there was an approximate inverse relationship between cutting depth and Z-axis height and repetition frequency, and repetition frequency had little effect on the cut width, controlling the Z-axis height appropriately helped reduce cutting width. The optimal parameters of UV laser process for cutting glass-epoxy material were laser power of 6w, cutting speed of 170 mm/s, laser frequency of 50 kHz and Z-axis height of 0.6mm, resulting in average cut width of 25μm and small HAZ.A method to blind via and fine lines with CO2 laser ablation has been put forward, The main process includes:1).Fine lines and blind via was ablated by CO2 laser;2). Plasma desmear process;3).seed layer by Electroless process;4).Dry Film Lamination;5).Blind via and fine lines filling plating;6) Remove the seed layer. This method not only greatly reduce the production process of blind via and fine lines, but improve the fineness of the line. And the method is optimized and achieved by experimental analysis, including the optimization of the laser parameters on blind via and fine lines, as well as plating parameters of filling plating of blind via and fine lines.Base on above researches cutting experimental analysis by UV laser, four layer Rigid-flex PCB with pads and finger were successfully achieved by reserved Kerf, reserved Kerf were formed by UV lase along windows area of rigid board outer contour, and laminated with a protective layer of rigid plates, and phenomenon of copper break off of pads and the finger of the window area were not appeared. Experiment showed that this method improved the product yield rate.