Flexible Hdi Boards Key Technologies

With the rapid development of IT industry, the miniaturization trend is unavoidable for electronic products, the printed circuit board is facing the challenge of higher accuracy and density requirement. HDI(High Density Interconnect)technology appeared. Rigid HDI board technology has been mature, but the flexible HDI board is still at the start stage, excepting America, Japan and Korea,flexible HDI is still a mythology to most countries. Nowadays, we are in the learning stage, research and development ability falls behind others, there is no flexible HDI manufacturing. Flexible HDI is widely used in IC packaging, computers, consumer electronics, aviation, space flight, military. Its strong points and vast market requirement will give an impetus to the development of flexible HDI technology. In the paper, technology of the key processes of the flexible HDI board manufacturing was studied, the achievements are followed:Control the distortion of PCB. In the process of measuring the distortion, different size vias bring different error, the iva introduced the smallest error is found to measure the distortion coefficient. Baking the boards reduces the distortion. These optimizations enhanced the control of distortion.Drilling by only one pulse under certain pulse width, find the appropriate pulse width one by one. The new way improved the study efficiency. The experiments showed that high efficiency, low cost, high dependability of CO2 laser can't be ignored, there is no better choice to manufacture the blind hole that larger than 75μm, UV laser drilling process is suitable for through micro via of multi-layer board that less than 50μm. 50μm~75μm is the transition region of the two methods, it depends on the actual needs.New desmearing method for bland via was found. Design optimization experiments and suitable parameter of plasma was proved. Based on the study of ultrasonic cleaning, PI adjustment method, a new desmearing technique was brought forward. Ultrasonic cleaning takes effects by physical way and PI adjustment method works by chemical reaction, the two methods were comminuted and play their roles together. The experiments showed an excellent effect, the vias were cleaner and the shape was ideal, all these are propitious to micro via metallization.Optimizing the process of micro vias metallization. Micro vias are so small that the plating solution refresh slowly, skip plating may happen, extending the time of key processes solved the problem and ensured the quality of the metallization.Make fine lines successfully. Subtractive Process was used to get thinner copper foil , meanwhile guarantee the environment of the exposal room, lower the power of exposure, 0.1mm pitch fine line is produced successfully,and these improvements increase the yield of the products, reduce the cost.In the paper, key technology of HDI board was studied, six layers flexible HDI was trial produced, and the experiment proved that these new technology methods and optimized parameter are feasible, it is ready for the production of HDI board in advance, and flexible HDI board manufacture has a bright future.