Abstract: This paper presents an experimental investigation of the influence of scuffing conditions on two-roller test rig. The prediction of Scuffing load capability model for the gear oils containing molybdenum dithiocarbomate (MoDTC) was developed based on the response surface methodology. A good agreement between the predicted and actual scuffing resistance was observed
within ±5% significance level.
Abstract: Conventional levels can be employed to measure just one dimensional inclinations each time, and are frequently used to measure inclination, straightness and flatness. There are two disadvantages when such levels are used to measure two dimensional inclinations (such as flatness): (1) two measurement steps are needed to measure two orthogonal directions in flatness; and (2) the
two directions cannot be perfectly perpendicular to each other because of setting errors. This paper describes the development of a novel optoelectronic level which employs a simple pendulum, reflection mirror, 2D PSD and laser diode. In this system, a laser light is projected onto reflection mirror 1 which is fixed on a simple pendulum, and mirror 1 reflects the light to mirror 2 which is fixed on a fixture, and mirror 2 reflects the light to the 2D PSD. Thus, the inclination measurement
result can be obtained from the output of the PSD. This paper establishes a novel system and describes the complete experiment. The A-axis rotation angle from approximately -1.3 to 1.3 degrees can be measured with an accuracy of 2 arc sec, and the B-axis rotation angle from approximately -1.7 to 1.7 degrees can be measured with an accuracy of 3 arc sec.
Abstract: The advantages of ductile regime grinding of silicon wafer such as smooth surface
roughness (Ra < 10 nm) and minimum subsurface damage layer (< 10μm) have great impact on the production process of wafer. With ductile regime grinding, the subsequent processes such as etching and rough polishing processes can be minimized. To achieve ductile regime grinding, a fundamental concept is the application of grain depth of cut being less than the critical cut depth, dc, of the silicon wafer. However, dc is dependent on material properties, cutting conditions, and crystallographic orientation .The objective of this paper is to derive, and to investigate by experiment, the dc value for silicon wafer grinding. Following these key steps, the effects of dc on various major grinding parameters are studied.
Abstract: This paper proposes a fast imaging auto-focus method to adjust the focus of laser diode products. The image of laser diode spot is processed to be a three-value image which is distinguished to be the background, blurred region and bright region. The ratio of areas between blurred and bright regions is used to judge whether the focusing is well-done. A four-point method is modified for this three-value image to get the areas of the blurred and bright regions. Thus, we can get the criterion for
auto-focus. In the meantime, we can also get the offset of the laser diode from the center of laser diode spot. The four-point method is faster and more accurate than the area, three-point, contour-tracking and least-squares error methods of center-positioning. This auto-focus method of spatial domain is also faster than other methods of the energy strength in the frequency domain. Finally, we adjust the
focus length of laser light by the servo control card and the AC servo motor, and then we can get the optimal focus length from the former image processing.
Abstract: This paper presents a series of three dimensional (3D) LIGA-like processes to fabricate microlens arrays on a cylindrical substrate. The processes consist of design of mask and rotating mechanism, coating of photoresist, 3D UV lithography, development and hardening, and electroforming. It transfers microlens array pattern to a φ76mm cylindrical stainless steel substrate intended for use as a rolling mold via electroforming. Process technologies are investigated and experiments are design and conducted as a proof of concept. Experimental results showed that
φ200μm microlens arrays can be fabricated on the substrate with good repeatability. The microlens pattern transferred to the 100μm-thick film showed the feasibility and stability of the 3D lithography process.
Abstract: This paper is to investigate the effects on grain size of different working conditions for making poly Si films by using the excimer laser annealing method. In this research, a KrF excimer laser of 248 nm in wavelength is used to irradiate a-Si films of 0.1 μm in thickness on glass substrate to produce poly-Si ones. The control parameters are laser intensity (200~500 mJ/cm2), pulse number
(1~10 shots) and coverage fraction (0~100%). Besides, the effect of a SiO2 layer is also studied, which is utilized as a heat-isolated zone located between the Si film and glass substrate. Average grain sizes from SEM photos are used to analyze the effects of these parameters. Purely from the heat transfer view, the Si film obtains more energy would have the slower cooling or solidification rate,
which results in the larger grain. From the experimental results, if the melt pool is within the range of Si film or does not contact its neighboring layer (SiO2 layer or glass substrate), the more absorbed energy from the higher energy intensity, the larger pulse number or the bigger coverage fraction can have the larger average grain size. However, with large enough energy, the melt pool could go through
the Si film and touch the lower layer. This would induce much more nuclei due to the homogeneous nucleation in the pool and the heterogeneous nucleation near the interface between the film and the neighboring layer. The resulting grain size is much smaller than that of the former one. The transition points of these two cases for different control parameters can be obtained from the experimental
results in this study. When the energy from the laser is small, the SiO2 layer acts like a heat absorber and makes the grain size smaller than that of not having the SiO2 layer. On the other hand, when the energy is large, the SiO2 layer becomes a heat insulator and makes the grain size larger.
Abstract: In the fabrication of a poly-Si film, an a-Si thin layer on glass substrate is melted by the irradiation of an excimer laser with the duration of nanosecond scale, and then is cooled down to form the poly-Si one. For analyzing the fabricating process, an efficient two-dimensional numerical model has been developed in this work, based on the finite difference method and the specific heat/enthalpy method used to handle the release of latent heat. The model can simulate the heat transfer, melt and
solidification behavors of a-Si films subjected to the laser irradiation. Numerical analysis was performed by solving the heat flow equation which incorporates the material properties of temperature dependence, the surface reflectivity of silicon film, the variation of the incident power density with time and heat lose by the radiation and convection from the film surfaces into the surroundings. From the analysis of temperature responses for different laser intensities, the thresholds corresponding to the surface and full melting of the Si film can be found. The temperature
responses are essentially different in the partial-melting and the complete-melting regimes. The Ft (surface melting threshold) and Fc (full-melt threshold) obtained from the simulation results of the proposed model in this study agree fairly well with those from the experimental data reported in the literature. In the partial-melting regime, the maximum temperature is close to the melting point of
amorphous Si, since it is the point where solid a-Si is transformed into liquid state and the high latent heat can absorb extra energy to keep the temperature at the melting point. The fluence larger than Fc is the complete-melting regime, the maximum temperature increases with fluence. It is also found that the variation of the surface reflectivity gives a good way to observe the phase change and the
melting duration. When the a-Si melts, the reflectivity rapidly goes up to a steady value which is consistent with the reflectivity of liquid silicon, and stays there until the melt silicon begins to solidify. As the irradiation energy of laser increases, the melting duration in the silicon layer is prolonged.
Abstract: This paper demonstrates the thermal-induced mechanical problems resulted from various temperature profiles of reliability test for a system-in-package (SIP) assembly process. The package includes two flip chip mounted chips (underfilled), two memory CSPs, some passive SMDs and 4-layer BT substrate. The flip-chip specimen was taken and the Moiré Interferometry was used as
methodology to verify the developed Finite Element Model and material property. It also shows that the developed finite element model is capable to simulate the JEDEC standard JESD22-A104 reliability thermal cycle test and then to predict solder fatigue life and to summarize design rules for thermal optimization of package based on the creep model and viscoplastic model of solder while the
SIP package design is proceeded. Thermal design for SIP depends on the placement of FC chip (high power) and memory CSP components. Passive SMDs are also included to study the effect of thermal-induced stress. A series of comprehensive parametric studies were conducted in this paper.