Rapid micro hole laser drilling in ceramic substrates using single mode fiber laser

Drilling of micron-scale high aspect ratio holes with ultra-short pulsed lasers: Critical effects of focusing lenses and fluence on the resulting holes’ morphology

“…Another important and growing application area for high aspect ratio micro holes is in electronic industry, i.e. interconnecting vias of printed circuit boards and guide blocks of interface probe cards for testing 3D integrated circuits and electronic devices [8][9][10][11]. In particular, it is necessary in such applications to produce arrays of holes usually in ceramic substrates with aspect ratios more than 5 while their diameters and pitches are less than 60µm and taper angle does not exceed 10°.…”

“…They are more pronounced in stationary beam drilling methods such as percussion drilling, compared with lower throughput, moving beam methods like trepanning and helical drilling [12]. To address these issues, for both drilling categories, new methods and tools have been developed, in particular changing the focusing position [8,13], the use of assisted gases [14][15][16][17], beam rotation [18,19], drilling under water [20], two-side drilling [21,22], new drilling cycles [12] and also different modelling and optimizing approaches to identify the optimum processing window [23][24][25][26][27]. Furthermore, the effects of process settings were investigated, too, especially peak power and pulse width effects on holes' repeatability in regards to the entry diameters [28] the evolution of shallow craters' diameter and depth in regards to number of pulses (NoP) and fluence [29] and the effect of different laser parameters such as average power on circularity, HAZ and taper angle [30] Other parameters that affect the laser drilling process, especially pulse energy, fluence and intensity, have been investigated, too.…”

Two-Side Laser Processing Method for Producing High Aspect Ratio Microholes

“…arrays of micro holes with high aspect ratio (depth to diameter ratio), that are required for a range of applications in the electronics industry, i.e. interconnecting vias and printed circuit boards, and also for producing interface probe cards for 3D wafer bumps [7][8][9][10]. The target holes' diameters and pitches in such applications are less than 60 µm, whereas the holes' aspect ratios are higher than 5 with taper angle less than 10°.…”

“…Different research groups have investigated laser parameter domains, different process setups and drilling strategies to reduce and even eliminate these shortcomings. In particular, Adelmann and Hellmann [7] investigated the effects of different factors affecting the process and found that the accurate setting-up of the focal plane on the workpiece was the most influential one in producing holes with a very low taper and higher circularity in ceramic plates. Wang et al [13] tried to identify the best focus plane positioning to minimize the taper and HAZ.…”

A theoretical analysis and experimental verification of a laser drilling process for a ceramic substrate

“…After laser surface treatment of the cylindrical-shaped alumina ceramic, surface roughness decreased with an increasing number of laser scan passes for all defocusing positions; however, depth deviation increased with an increasing number of passes. Adelmann and Hellmann [12] used a single-mode fiber laser for drilling alumina and aluminum nitride with thicknesses ranging from 0.25 to 1.5 mm; focus positions were controlled to obtain drill holes with small taper diameters. The drilling times for both materials and all thicknesses were <1 ms, with 0.1 ms for 0.25 mm alumina being the shortest.…”