The activation threshold evaluation of metallization for aluminum nitride ceramic under nanosecond laser pulses in air

Laser‐Tuned Surface Wettability Modification and Incorporation of Aluminum Nitride (AlN) Ceramics in Thermal Management Devices

“…Such laser-induced passivation of AlN resulted in the formation of a thin layer of Aluminum oxides (AlOx), which being stable, protected the water-exposed surface from hydrolysis as confirmed from experiments where dripping water droplets were released for long periods on modified substrates at elevated temperatures (Section S2, Supporting Information). [42,43,51] The oxide layer on top of the AlN substrate was O(≈1 μm), whereas the underlying bulk AlN substrate was O(≈1 mm) thick; consequently, the oxide layer was not thick enough to bring about significant changes to the bulk AlN properties. The CTE values become critical where different materials join, for example in direct chip cooling applications, wherein the CTE of the heat transfer device (herein made from AlN) should closely match the CTE of the heat source (generally made from Si).…”

“…[39] While other techniques often implement deposition of a thin film of another material, metallization (or surface passivation) of AlN via laser etching forms a film of aluminum or a rich mixture of oxides, which can inhibit hydrolysis and allow safer prolonged use of AlN. [42,43] Similar laser-based approaches have been recently used for combining Al-AlN powders in laser sintering for additive manufacturing [44] or in electroless plating. [45] Such ceramic surfaces are hard to machine and hence difficult to impart micro or nanoscale roughness, which is necessary to impart specific surface properties [26,27] that are critical for enhanced heat transfer.…”

Effect of laser parameters and atmosphere in the structuring of aluminum nitride

“…The reactions of laser‐activated AlN could be expressed as 10,15 : $$\begin{equation}{\rm{AlN(s)}} \to {\rm{Al(s)}} + 1/2 \, {{\rm{N}}_{\rm{2}}}{\rm{)(g)}}\end{equation}$$where (s), (l), and (g) denote the solid and gas phases, respectively. High thermal energy generates a precipitated aluminum layer on the AlN ceramic surface.…”

“…The directly formed conductive metal layer can be used as a seed layer to meet the requirements of ceramic substrate packaging by chemically plating copper, gold, nickel, and other metals 9 . However, the metallic aluminum layer precipitated in laser‐activated metallization is very sensitive to the laser parameters 10,11 . Kozioł et al.…”

“…9 However, the metallic aluminum layer precipitated in laser-activated metallization is very sensitive to the laser parameters. 10,11 Kozioł et al studied the laser-activated metallization of AlN ceramic and found that differences in the thickness and resistivity of the metallic aluminum layers were produced in different gas environments. 12 Gilbert et al used ultra-violet and near-infrared neodymium-doped yttrium aluminum garnet lasers to machine linear grooves on the surface of AlN ceramic and found that the laser pulse overlap ratio was the main factor influencing the surface roughness of the machined portion of the AlN ceramic as well as the angle of the groove walls.…”