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RISS 인기검색어
- 검색키워드
- 저자 : Jwad, Tahseen (검색결과 1 건)
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Nasrollahi, Vahid,Penchev, Pavel,Jwad, Tahseen,Dimov, Stefan,Kim, Kyunghan,Im, Changmin Elsevier 2018 Optics and lasers in engineering Vol.110 No.-
<P><B>Abstract</B></P> <P>Micro drilling employing ultra-short pulsed lasers is a promising manufacturing technology for producing high aspect ratio holes, particularly on ceramic substrates due to the growing range of application in electronic industry. Controlling the morphology and quality of the holes is an important factor in fulfilling the requirements of such applications. In this research, the effects of a wide fluence spectrum associated with the use of femto-second lasers on achievable aspect ratios were investigated by employing lenses with different focal distances. The holes’ morphology and quality were analysed utilising a high resolution X-ray tomography (XCT). It was demonstrated that the achievable aspect ratio can be increased from 3 to 25 just by varying the lenses focal distances. In addition, the quality of produced holes in terms of taper angle and cylindricity was investigated and the results showed that the quality would be improved by increasing the fluence and/or decreasing the focal distance. At the same time, the limitations of drilling holes with low focal distance lenses were discussed, i.e. sensitivity to defocusing and increased risks of recast formations inside the holes and bending effects, that should be considered in designing processes for high aspect ratio percussion drilling.</P> <P><B>Highlights</B></P> <P> <UL> <LI> The effects of different focal distance lenses and fluence on achievable holes’ aspect ratio in percussion drilling with femto-second lasers are investigated. </LI> <LI> The achievable holes’ aspect ratio can be increased significantly by employing lower focal distance lenses. </LI> <LI> Holes’ morphologies, cylindricity and taper angle improve by employing smaller focal distance lenses. </LI> <LI> The use of high fluence and high pulse energy in percussion drilling leads to a high penetration depth. </LI> <LI> Key limitations in using lenses with smaller focal distances are a higher sensitivity to defocusing, risks of recast formations and bending effects. </LI> </UL> </P>
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