Quality inspection of deposited solder pastes is critical in surface mounting processes. As SMT component pitches decrease, 3D measurement of solder pastes has become more and more important in ensuring solder joint reliability. Currently, the 3D measurements for solder pastes are mainly performed by laser-based systems. However, they suffer from low inspection speed due to the physical line-scanning process. In this paper, a fast and cost-effective 3D measurement system for deposited solder pastes is proposed. The proposed system uses an LCD-based phase shifting technique to perform full-field 3D measurement of solder pastes with high accuracy. Experiments have shown that the 3D profiling and volume measurement of solder pastes are very efficient and effective with the proposed system. The volume measurement repeatability is in the micrometer range. The processing time of the proposed 3D measurement system for an image of 640×480 pixels is less than 1 second on a typical personal computer.
Ball-Grid-Array (BGA) has become one of the most popular packaging techniques in the electronic industry. Coplanarity inspection of BGA solder balls is critical in BGA manufacturing for process and quality control. Currently, the 3D measurement systems for BGA coplanarity inspection are mainly based on laser scanning techniques. However, they suffer from low inspection speed due to the physical line-scanning process. In this paper, a fast and cost-effective 3D measurement system for coplanarity inspection of BGA solder balls is proposed. The proposed system uses an LCD-based phase measuring technique to perform full-field 3D measurement of BGA solder balls with high accuracy. Experiments have shown that the coplanarity measurement of BGA solder balls is very efficient and effective with the proposed system. The measurement repeatability is in the micrometer range.The processing time of the proposed 3D measurement system for an image of 640×480 pixels is less than 2 seconds on a typical personal computer.
In recent years, the demand of polarizer films has increased since that liquid crystal displays are widely used in consumer electronics products such as smart phones, tablet computers and large-size TVs. For improving production yields, manufacturers actively adopt automated inspection equipment to detect in-line polarizer film defects. This study uses computer vision techniques to develop a cost-effective optical detection system for the tiny bump defects of polarizer films. The proposed system applies digital fringes and image processing techniques to detect the tiny bump defects. Experiments show that the proposed system can effectively detect the tiny bump defects, and complete the defect inspection of a sample polarizer film with an area of 1600 × 1200 pixels (36mm × 27mm) within 0.3 seconds.
The flip chip, a type of chip mounting used in semiconductor devices, has become one of the most popular innovations in the semiconductor packaging industry. The height of flip-chip solder bumps ranges from 20 to 140 m with a required measurement accuracy of 2 m. Three-dimensional (3-D) measurement of flip-chip solder bumps is crucial to flip-chip manufacturing quality and process control. Currently, 3-D measurement systems for flip-chip solder bumps are mainly based on laser scanning techniques. However, they require a high implementation cost, and suffer from low inspection speed due to the physical line-scanning process. In this paper, a fast and cost-effective 3-D measurement system for flip-chip solder bumps is proposed. The proposed system is based on a phase shift technique, in which the phase is accurately shifted by a software-controlled grating using a digital light processing (DLP) unit that allows full-field measurement of a projected flip chip. The DLP unit can provide a higher fringe-contrast pattern at a faster changing time than a liquid crystal display (LCD) panel. Phase shift-based measurement systems require a calibrated system parameter, which is generally considered a fixed value in currently available methods. In this paper, adaptive parameter values, instead of a fixed value, are used to improve measurement accuracy. The proposed system also adopts a fringe-contrast thresholding to solve the pseudo-surface height problem for high reflective solder bumps and low reflective substrate in a flip chip. Experiments have shown that the 3-D measurement of flip-chip solder bumps is very efficient and effective with the proposed system. Computation time of the proposed 3-D measurement system for a 640 480 image that contains almost 500 solder bumps is less than 1 s, and measurement accuracy meets the required specification of 2 m.Index Terms-Flip chip, phase shifting technique, solder bump, three-dimensional measurement.
Solar power has become more and more important due to the decrease of the energy sources. The solar cell is the main device to transform solar power to electric power. Since the power efficiency of solar cell is decreased with defects generated in manufacturing process, defect inspection is crucial to ensure the reliability of solar cells. This paper presents a cost-effective machine vision system for surface defect inspection of printed polycrystalline silicon solar cells. The defects of printed busbars and fingers are effectively inspected by using auto-thresholding and projection techniques sequentially in the inspection process. Experimental results have demonstrated that the defect inspection of printed polycrystalline silicon solar cells is very effective with the proposed system.
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