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Deng F.,University of Hong Kong | Deng F.,ASM Assembly Automation Ltd. | Sze W.F.,ASM Assembly Automation Ltd. | Deng J.,ASM Assembly Automation Ltd. | And 3 more authors.
Applied Optics | Year: 2012

In many industrial inspection systems, it is required to have a high-precision three-dimensional measurement of an object under test. A popular technique is phase-measuring profilometry. In this paper, we develop some phase-shifting algorithms (PSAs). We propose a novel smoothness constraint in a regularization framework; we call this the R-PSA method and show how to obtain the desired phase measure with an iterative procedure. Both the simulation and experimental results verify the efficacy of our algorithm compared with current multiframe PSAs for interferometric measurements. © 2011 Optical Society of America.

Dong M.,Chinese University of Hong Kong | Chung R.,Chinese University of Hong Kong | Lam E.Y.,University of Hong Kong | Fung K.S.M.,ASM Assembly Automation Ltd.
IEEE Transactions on Electronics Packaging Manufacturing | Year: 2010

Die bonding in the semiconductor industry requires placement of solder bumps not on PCBs but on wafers. Such wafer bumps, which are much miniaturized from their counterparts on printed circuit boards (PCBs), require their heights meet rigid specifications. Yet the small size, the lack of texture, and the mirror-like nature of the bump surface make the inspection task a challenge. Existing inspection schemes generally reconstruct every bump surface. This work addresses by how much can the task be simplified if merely the bump heights are inspected against the specification. It is assumed that ball bumps are used as the wafer bumps. An imaging setup is described that lets the peaks of the ball bumps be distinguishable in the image data. A measure is also described that reveals how well the ball bumps meet the height specification without going through explicit 3-D reconstruction. The measurement, in the form of a 3 × 3 matrix extractable from the image data, is sensitive to variations in the bump heights, but not to 2-D uncertainties in soldering the bumps onto the wafer substrate, or small variations in the placement of the wafer in 3-D. Experimental results are shown to illustrate the effectiveness of the proposed system. © 2010 IEEE.

Ngai D.C.K.,ASM Assembly Automation Ltd. | Yung N.H.C.,University of Hong Kong
IEEE Transactions on Intelligent Transportation Systems | Year: 2011

In this paper, we present a learning method to solve the vehicle overtaking problem, which demands a multitude of abilities from the agent to tackle multiple criteria. To handle this problem, we propose to adopt a multiple-goal reinforcement learning (MGRL) framework as the basis of our solution. By considering seven different goals, either Q-learning (QL) or double-action QL is employed to determine action decisions based on whether the other vehicles interact with the agent for that particular goal. Furthermore, a fusion function is proposed according to the importance of each goal before arriving to an overall but consistent action decision. This offers a powerful approach for dealing with demanding situations such as overtaking, particularly when a number of other vehicles are within the proximity of the agent and are traveling at different and varying speeds. A large number of overtaking cases have been simulated to demonstrate its effectiveness. From the results, it can be concluded that the proposed method is capable of the following: 1) making correct action decisions for overtaking; 2) avoiding collisions with other vehicles; 3) reaching the target at reasonable time; 4) keeping almost steady speed; and 5) maintaining almost steady heading angle. In addition, it should also be noted that the proposed method performs lane keeping well when not overtaking and lane changing effectively when overtaking is in progress. © 2006 IEEE.

Hu Z.,Chinese University of Hong Kong | Chung R.,Chinese University of Hong Kong | Fung K.S.M.,ASM Assembly Automation Ltd.
Machine Vision and Applications | Year: 2010

Extended Gaussian image (EGI) and complex EGI (CEGI) have been widely used as the representation of 3D shapes for shape recognition and pose estimation. In this work, we extend the representations and present a new representation named enriched complex extended Gaussian image (EC-EGI). The representation follows the same framework of EGI and CEGI, which is to represent each surface patch of the target 3D shape as a weight at the associated spot on the surface of the Gaussian sphere. However, while the original CEGI uses a single complex number as the weight, the new representation uses three complex numbers, which are related to the centroid position of the surface patch in 3D. With the inclusion of more information in the new representation, not only could object pose be determined more accurately, but also some key ambiguities of shape representation that CEGI and EGI have also removed. The translation parameters in the pose estimation application could also be determined in a simpler and more accurate way. In addition, the Gaussian sphere partition problem of CEGI is no longer present. Experimental results on synthetic and real image data are shown to illustrate the performance of the proposed representation in pose estimation. © 2009 Springer-Verlag.

Hon S.F.,Hong Kong Polytechnic University | Kwok K.W.,Hong Kong Polytechnic University | Li H.L.,ASM Assembly Automation Ltd. | Ng H.Y.,ASM Assembly Automation Ltd.
Review of Scientific Instruments | Year: 2010

Self-focused acoustic ejectors using the Fresnel zone plate (FZP) have been developed for ejecting viscous liquids, without nozzle, in the drop-on-demand mode. The FZP is composed of a lead zirconate titanate piezoelectric plate patterned with a series of annular electrodes, with the unelectroded region of the plate removed. Our results show that the acoustic waves are effectively self-focused by constructive interference in glycerin (with a viscosity of 1400 mPa s), giving small focal points with a high pressure. Due to the high attenuation, the wave pressure decreases significantly with the distance from the FZP. Nevertheless, the pressure at the focal points 2.5 and 6.5 mm from the FZP is high enough to eject glycerin droplets in the drop-on-demand mode. Driven by a simple wave train comprising a series of sinusoidal voltages with an amplitude of 35 V, a frequency of 4.28 MHz, and a duration of 2 ms, the ejector can eject fine glycerin droplets with a diameter of 0.4 mm at a repetition frequency of 120 Hz in a downward direction. Droplets of other viscous liquids, such as the prepolymer of an epoxy with a viscosity of 2000 mPa s, can also be ejected in the drop-on-demand mode under similar conditions. © 2010 American Institute of Physics.

Sun Z.G.,Hong Kong Polytechnic University | Cheung N.C.,Hong Kong Polytechnic University | Zhao S.W.,Hong Kong Polytechnic University | Gan W.-C.,ASM Assembly Automation Ltd
IEEE Transactions on Vehicular Technology | Year: 2010

A novel linear magnetic levitated actuator using the switched reluctance principle is addressed in this paper. This actuator can be applied to precise motion control of automation machines. The proposed system has the advantages of a simple and robust structure, and direct drive capability. The contactless structure eliminates mechanical wear, friction, noise, and heat generation. To verify the feasibility of the proposed system, the magnetic levitated force is analyzed by magnetic circuit analysis (MCA) and by finite-element analysis (FEA). A prototype structure is fabricated, and experiments are performed with the actual hardware. Results of the MCA and the FEA are both compared with the results obtained from the hardware experiments. They all agree with the proposed design methodology. This paper can form a useful reference in the design of a mechanical structure for magnetic levitated switched reluctance actuators. © 2006 IEEE.

Sun Z.G.,Hong Kong Polytechnic University | Cheung N.C.,Hong Kong Polytechnic University | Zhao S.W.,Hong Kong Polytechnic University | Gan W.C.,ASM Assembly Automation Ltd.
Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science | Year: 2010

A control algorithm for the position tracking of a magnetic levitation system is presented in this article. The magnetic levitation system is well known for its non-linear dynamic characteristics and open-loop instability. The external disturbances will deteriorate the dynamic performance of the magnetic levitation system, and may give rise to system instability. This problem triggers enormous interests in designing various controllers for the non-linear dynamic system. In this article, a magnetic levitation system is first modelled. Then, a sliding mode controller is proposed, with a simple yet effective disturbance observer to perform disturbance rejection. Both the simulation results and the experimental results verify the validity of the robust controller.

An apparatus (10) for dispensing solder onto a substrate (12) for mounting a semiconductor chip on the substrate comprises a dispensing body (18) and first and second dispensing channels extending through the dispensing body. Each dispensing channel is operative to receive a separate solder wire to feed the solder wire (24) to an end of the dispensing body facing the substrate. The dispensing channels are further operative to introduce the solder wires in a solid state simultaneously from the end of the dispensing body to be melted upon contact with the substrate which is heated.

A bonding apparatus (10) for bonding a length of wire comprises a first module (14) which is drivable along a linear axis towards and away from a bonding point and a second module (16) slidably mounted to the first module (14). A wire cutter (36) is mounted to the first module (14) and a bonding tool (32) is mounted to the second module (16). A coupling mechanism is operative to lock the second module (16) in fixed relative position to the first module (14), and to unlock the second module (16) from its fixed relative position to the first module (14) so that the second module (16) is slidable relative to the first module (14) in directions parallel to the linear axis.

ASM Assembly Automation Ltd. | Date: 2012-05-09

Adhesive is dispensed for conducting die bonding onto a substrate including rows of bond pads aligned along a first axis and columns of bond pads aligned along a second axis transverse to the first axis where target dispensing positions are located. A first dispensing head incorporating a first nozzle and a second dispensing head incorporating a second nozzle are provided and the substrate is fed along the first axis to a position where the first and second dispensing heads are located. Pattern recognition of a columnar section of the substrate comprising one or more consecutive columns of bond pads with an optical system may be conducted by moving the optical system along the second axis relative to the substrate. Thereafter, the first nozzle and the second nozzle are driven concurrently to dispense adhesive from the first and second nozzles onto the target dispensing positions in the same columnar section of the substrate.

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