Abstract
The high-quality, high-efficiency micro-hole drilling of structural ceramics to improve the thermal conductivity of hot-end parts or achieve high-density electronic packaging is still a technical challenge for conventional processing techniques. Recently, the laser drilling method (LDM) has become the preferred processing tool for structural ceramics, and it plays an irreplaceable role in the industrialized processing of group holes on structural ceramic surfaces. A variety of LDMs such as long pulsed laser drilling, short pulsed laser drilling, ultrafast pulsed laser drilling, liquid-assisted laser drilling, combined pulse laser drilling have been developed to achieved high-quality and high-efficiency micro-hole drilling through controlling the laser–matter interaction. This article reviews the characteristics of different LDMs and systematically compares the morphology, diameter, circularity, taper angle, cross-section, heat affect zone, recast layer, cracks, roughness, micro–nano structure, photothermal effect and photochemical reaction of the drilling. Additionally, exactly what processing parameters and ambient environments are optimal for precise and efficient laser drilling and their recent advancements were analyzed. Finally, a summary and outlook of the LDM technology are also highlighted.
Highlights
The trend of product miniaturization, as well as the trend of manufacturing miniature functional parts and components, require new tools and manufacturing methods [1].Among these, high-aspect-ratio (>5:1) micro-holes have become one of the typical features of products, such as the lab-on-a-chip which uses micro-channel networks to transport, mix, separate, and detect samples; the important guiding structure for the gas/medium that is used in the ignition target ball and micro-heat exchanger; the cooling holes in the aeroengine turbines blades [2,3,4]
Since laser processing in water is enhanced by the better laser–matter interaction, which limits heat accumulation, and removes debris to avoid re-deposition, it has been proven that it the mechanical impact related to the formation and the collapse of bubbles of evaporated material [77,78,79,80] can be widely used in the laser drilling of ceramic materials, including long and femtosecond pulsed laser
An interesting experiment was reported by Wang et al in 2019 which we found worked extremely well when used in the high-efficiency and high-quality drilling of structural ceramics: a two-step combined pulse laser (CPL) approach to drill the thermal barrier coated nickel base alloys
Summary
The trend of product miniaturization, as well as the trend of manufacturing miniature functional parts and components, require new tools and manufacturing methods [1]. Multi-size, multi-pitch, and high-density micro-holes processing is used to provide internal circuit interconnection, and the processing quality needs to meet the packaging requirements of chip conduction and pin fixation [5,6,7]. Such arrays of holes as the core structure of many micro-devices and systems, the processing quality, accuracy, and repeatability directly determine the performance (such as the detection sensitivity and heat dissipation performance) and integration level of the entire device/system, which introduces further constraints and limit the available options for their cost-effective manufacture. The opportunities and challenges of the laser drilling of structural ceramics are discussed
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