Realization of sub-4 µm Laser Microvia on ABF

In recent years, high-density I/O has been implemented in IC packages. As a result, the density of wiring and drilling on build-up boards has significantly increased. A major bottleneck in achieving even higher density pattern on build-up boards is micro-vias formation. Thus, further miniaturization of microvias is one of the most important issues in packaging. We are developing a deep ultraviolet (DUV) laser processing machine that delivers intense laser pulses with a wavelength more than 30 times shorter than that of the CO2 lasers currently used for microvias processing. In this article, we demonstrate the drilling of sub-4 µm microvias on the Ajinomoto Build-up Film® (ABF) using direct DUV-laser processing. The sub 4-µm holes allow for a hole density that is twice as high as that of the 6-µm holes we reported previously.