The wear resistance of high-value copper components used in the metal casting, automotive, aerospace and electrical equipment industries can be improved by applying nickel (Ni)-based coatings through laser cladding. A high-power diode laser array providing continuous power levels up to 10 kilowatts with beam-shaping optics providing a rectangular focal region of various dimensions was used to deposit Ni-based alloy coatings with controlled thickness ranging from 0.3 mm to 1.6 mm in a single pass on copper (Cu) substrates. Slotted powder feeding plates with various discrete widths delivered uniform streams of powdered metal particles entrained in a carrier gas, matching the selected focal spot dimensions. To enhance laser beam coupling with the substrate and to avoid defects such as cracks, delamination and porosity, Cu substrates were preheated to a temperature of 300°C. The effect of heat input on microstructure of the cladding and extent of the heat-affected zone (HAZ) was evaluated using optical microscopy and scanning electron microscopy. Excessive heat input with longer interaction time increased dilution, porosity and expanded HAZ that significantly reduced the hardness of both the clad and the Cu substrates. Average microhardness of the Ni-C-B-Si-W alloy coating was 572 HV, which was almost 7 times greater than the hardness of the Cu substrate (84 HV).
A significant enhancement in the rate of material removal is demonstrated using a nanosecond-pulsed UV fiber laser in multi-pulsing burst mode, as compared to the case without bursting. Percussion drilling and scribing of thin-film and bulk material tests show that, in general, laser bursts with increased pulse count and reduced pulse spacing show higher rates of material removal. A considerable improvement in removal rate is demonstrated, when bursting is applied to scribing of mono-crystalline silicon (m-Si) and up to 30% in percussion drilling speed. Likewise, improved material removal is demonstrated for scribing of thin film of indium tin oxide (ITO) on glass or metal film on sapphire. Examples of material processing are given with and without bursting at similar experimental conditions of average power, scan speed, and burst/pulse energies. Experimental results included are for m-Si, ITO thin films on glass, and metal films on sapphire.
Thin sections of single-crystal sapphire are favored as substrates for the epitaxial deposition of gallium nitride and other III-V and II-VI thin films used in the fabrication of electro-optic devices such as blue-green LEDs and laser diodes. Due to difficulties commonly encountered in cutting this hard material, alternatives to traditional mechanical processing techniques are of particular interest. This paper reviews a recent study characterizing the scribing of sapphire using the tightly focused output of an ultraviolet wavelength pulsed solid-state laser.
We report on the development and testing of a laser system that delivers up to 200 mW of continuous-wave radiation at 198.54 nm in a near diffraction-limited beam, to be used as a source for photolithography mask writing and mask inspection. The source has been developed with the support of International SEMATECH. The laser output is obtained by intra-cavity sum frequency generation in a CLBO (Cesium Lithium Borate) non-linear crystal
As the demand for semiconductor devices based upon ever-thinner silicon substrates continues to increase, mechanical techniques suitable for dicing wafers appear to be approaching their practical limits. Recent advances in power scaling have now enabled reliable ultraviolet-wavelength lasers to be considered to offer a flexible solution to this dilemma. This paper presents new data on the machining of thin silicon wavers using a high average power 355-nm wavelength pulsed laser. In particular, the concept of pulse repetition-rate scaling of the effective cutting speeds was investigated to determine the preferred direction for further laser development efforts.
Diffusion bonding of single crystal Nd:YAG with another Nd:YAG or undoped YAG involves precision polishing, assembly by optical contacting and heat treatment. Preliminary data on bonding kinetics indicate an approximate (time)1/5 dependence which describes bulk sintering. Optical homogeneity across the interface did not exhibit a discontinuity for composites of Nd:YAG/Nd:YAG while a step at the Nd:YAG/undoped YAG interface is assumed to be due to a difference in refractive index. Parallel to the interface, stress birefringence values of up to about 5 nm/cm have been observed for Nd:YAG/Nd:YAG and about 20 nm/cm for Nd:YAG/undoped YAG. Corresponding values perpendicular to the interface are about 2 to 3 nm/cm for both types of composites. Reflectivity of about 3% and scattering of about 5% has been measured at 89 degrees incident angle while values below 0.03 and 0.05% respectively have been estimated for normal incidence.