Abstract
High density and high quality interconnects are necessary for the preparation of miniaturized and lightweight electronic products. Therefore, small-diameter and high-density through-holes in FPCs (Flexible Printed Circuits) are required. However, the current processing methods cannot further decrease the diameters and improve the quality of through-holes. Comparatively, ultrashort pulse laser is a good choice. In this paper, the processing technology for the microdrilling of through-holes in FPCs using a 10 ps pulse laser was systematically studied. The effects of laser parameters, including the wavelength, energy, pulses and polarization, on the drilling of through-holes were investigated. The various processing parameters were optimized and the plausible reasons were discussed. Finally, the desired small-diameter and high-density through-holes in FPCs were obtained. The experimental results showed that, through-holes with diameters of less than 10 µm and inlet interconnection pitches of 0~2 µm could be successfully drilled in FPCs using ultrashort pulse laser.
Highlights
Flexible printed circuits (FPCs) are composite laminated materials that are mainly composed of copper (Cu) and polyimide (PI)
It is necessary to process the FPCs with high density and quality interconnects
Microhole drilling is the main processing technology to obtain the interconnects in FPCs
Summary
Flexible printed circuits (FPCs) are composite laminated materials that are mainly composed of copper (Cu) and polyimide (PI). Cu foil is used as the conductive metal material, while the typical organic polymer PI serves as the dielectric or insulating layer due to its advantages of good dielectric property, thermal stability, excellent mechanical properties, plasticity and less fragility [1]. Based on their structural and material characteristics, FPCs display many desirable properties, such as high reliability, flexibility, light weight and thinness. It is necessary to process the FPCs with high density and quality interconnects. There are strict requirements for the size and quality of the microholes drilled in FPCs, which directly determine the density and performance of interconnects
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