We have constructed a neural network visual inspection system which classifies solder joints automatically using a neural network learning algorithm. The neural network is a repeat teaching algorithm without explicit quantitative criterion. In this system, the resolutions of the input images affect the quality of classification. More information can improve the quality of the inspection; however, the learning time and inspection time also increase. In this paper, we report on the effects of decreasing the input number by extracting the high contribution ratio components using the principle component analysis. The results show that the learning time did not proportionally decrease with the input number; however, the learning and inspection times are decreased and no deterioration in the classification quality was observed.

View full abstract

We have developed a center-frequency tunable band-pass filter with an in-out (I/O) matching compensation circuit. Additional electrical pads are placed at the open ends of the resonators in order to tune the center frequency. Pads are also placed around the I/O coupled-line elements to enable the external Q (Q_e) and the resonant frequency to be adjusted, thereby reducing the insertion loss caused by tuning. A prototype three-pole center-frequency tunable band-pass filter with I/O matching compensation circuit was fabricated and found to have a measured center frequency of 4.98 GHz. Use of the electrical pads to adjust the effective lengths of the resonators and the pads to adjust the Q_e and resonant frequency resulted in 1.2 GHz (4.98~3.78 GHz) center frequency tuning without increasing the insertion loss.

View full abstract

The residual warpage generated in two-layer-laminated structures consisting of epoxy resin and various substrates was examined by experiment and thermo-viscoelastic numerical analysis based on a linear viscoelastic theory from the view of cooling conditions. It was clarified that the residual warpage in any of laminated structure was influenced not only by the speed of cooling from a high holding temperature but also by the maximum high temperature. That is, first of all, the residual warpage increased as the maximum temperature became higher. Secondly, the residual warpage was larger with rapid cooling than with slow cooling in general. Finally, the residual warpage generated by rapid cooling of the steel and aluminum alloy substrates was larger than that generated with slow cooling.

View full abstract

We found that self-alignment accuracy was better than ±2 μm in the case with an initial offset of up to 1 mm. This method, driven by the surface tension force of the liquid, offers new technical solutions for both high accuracy chip bonding and low cost placement manner. Some important points, such as wetting behaviour, die release offset, and the influence of defects on a die, were studied in order to suggest approaches to robustness in this new technique.

View full abstract