Molybdenum (Mo) feedthrough pins (with a diameter of smaller than half of a millimeter) are commonly used for
rechargeable batteries because of their inert nature and close CTE match with glass. Pure Mo has a very high melting
temperature, and is not conducive to soldering. Due to the small geometry, the attachment of electrical conducting
wire/ribbon to the pin is very challenging if conventional attachment methods were possible. Solid-state bonding by
resistance welding is marginally feasible, but often results in moderate bond strength. In this work, fine spot welding
using a pulsed Nd:YAG laser for the attachment of a conductive ribbon to a Mo pin is reported. The effect of the conductive ribbon materials was investigated. The weld condition was studied with the aim of determine the best set of laser processing parameters, including the angle of laser beam incidence, the laser power and the pulse duration. Weld strength testing on ribbon-pin weld structures was conducted. The laser fine spot welding resulted in a three times higher bond strength than resistance welding.
Laser micromachining is one of many laser material processing technologies employed in scientific research and engineering applications. It involves the deposition of photon energy and the material interaction. The intense photothermal energy is transported into the target material causing melting and evaporation. The material is removed layer by layer by melting and flowing away or by direct vaporization / ablation. It is due to the focused small spot size that the laser micromachining can remove material in small quantity at a time, thus precise control of geometrical dimension is possible. In this work, a nanosecond pulsed Nd:Yttrium-Aluminum-Garnet (Nd:YAG) laser was employed to generate relatively long notch of different dimensions (25.4 mm-length × 0.1 mm-width × 0.051/0.102/0.152 mmdepth) on Ti-3Al-2.5V seamless tubes for fatigue life study. Cyclic hydraulic impulse pressure test was conducted to find out the fatigue limits of the titanium tube containing the laser micromachined notch. The results of fatigue lives, crack profile and pattern of crack propagation are presented and discussed in this paper. Scanning electron microscopy was employed to characterize the fatigue crack profile and the laser micronotch. The capability of generating sharper notch root and consistent pre-crack on the surface of materials makes nanosecond pulsed Nd:YAG laser a great choice in preparing for fatigue test samples for crack growth life study.
In this work, a laser welding process for attaching conducting ribbons to a miniaturized feedthru is introduced. A pulsed
1064nm Nd:YAG laser was used as an example in this study. A numerical simulation by means of finite element method
(FEM) for the prediction of temperatures in the feedthru assembly is presented. The approach used was intended to solve
the energy balance equation with appropriate initial and boundary conditions. A laser weld joint strength test was
conducted using a Mechanical Strength Tester. The influence of processing parameters, such as laser power and pulse
duration, on the temperature distribution and the weld joint strength are investigated and discussed.
Laser welding is a commonly used process to assemble medical devices. The heat produced during the laser welding
process may have an adverse effect on the mechanical integrity of the case assembly and the functionality of heat
sensitive electronic components. In order to maintain the mechanical integrity of the case assembly and to protect the
subcomponents, it is important to control the temperature in the assembling process, the investigation of the temperature
distribution in the assembly during laser welding is thus necessary. In this paper, we report an experimental method and
a numerical simulation for the investigation of the temperature field in the process of laser welding the eyelet to the case
subassembly of the Functional Electrical Battery Powered Microstimulator (FEBPM). A pulsed 1064nm Nd:YAG laser
is used as an example in this paper.
Laser welding technology is widely used in fiber optic components assembling. A big issue in fiber optic packaging using laser welding is the welding-induced alignment distortion (WIAD), which significantly reduces the fiber optic coupling efficiency. Various studies have been conducted to investigate the factors affecting the WIAD in butterfly laser module packaging, but the influence of laser parameters on the WIAD remains unnoticed. We present a study in minimizing the WIAD by laser pulse shape. Finite element method is employed and a realistic laser-materials interaction model is developed and incorporated into the analysis to investigate the influence of six types of laser pulse shape on the WIAD in the butterfly packages. The results show that the pulse shape significantly affects WIAD. Ideally, a properly selected pulse shape can eliminate or minimize the WIAD in the butterfly laser module packages.
In fiber-optic component attachment using laser welding, the welding-induced-alignment-distortion (WIAD) is an issue significantly affecting the packaging yield. Our previous investigation has shown that an elimination or minimization of WIAD is possible if the relevant laser welding process parameters such as welding sequence can be optimized. In this work, a more realistic physics based laser welding model is introduced and incorporated into our finite element analysis model by a few user subroutines, the effect of welding sequence on WIAD in a butterfly laser diode module package is evaluated. The result verifies the conclusion that the effect of laser welding sequence on WIAD for butterfly laser diode packages is significant and WIAD control can be achieved as appropriate welding sequence is employed.
In pigtailing of a single mode fiber to a semiconductor laser for optical communication applications, the tolerance for displacement of the fiber relative to the laser is extremely tight, a submicron movement can often lead to a significant misalignment and thus the reduction in the power coupled into the fiber. Among various fiber pigtailing assembly technologies, pulsed laser welding is the method with submicron accuracy and is most conducive to automation. However, the melting-solidification process during laser welding can often distort the pre-achieved fiber-optic alignment. This Welding-Induced-Alignment-Distortion (WIAD) is a serious concern and significantly affects the yield for single mode fiber pigtailing to a semiconductor laser. This work presents a method for predicting WIAD as a function of various processing, laser, tooling and materials parameters. More specifically, the degree of WIAD produced by the laser welding in a dual-in-line laser diode package is predicted for the first time. An optimal welding sequence is obtained for minimizing WIAD.
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