Hierarchical planning for a surface mounting machine placement

For a surface mounting machine (SMM) in printed circuit board (PCB) assembly line, there are four problems, e.g. CAD data conversion, nozzle selection, feeder assignment and placement sequence determination. A hierarchical planning for them to maximize the throughput rate of an SMM is presented here. To minimize set-up time, a CAD data conversion system was first applied that could automatically generate the data for machine placement from CAD design data files. Then an effective nozzle selection approach was implemented to minimize the time of nozzle changing. And then, to minimize picking time, an algorithm for feeder assignment was used to make picking multiple components simultaneously as much as possible. Finally, in order to shorten pick-and-place time, a heuristic algorithm was used to determine optimal component placement sequence according to the decided feeder positions. Experiments were conducted on a four head SMM. The experimental results were used to analyse the assembly line performance.

Analytical calculation of electromagnetic, torque for surface mounted permanent magnet brushless motors

With the air gap magnetic field distribution of surface mounted permanent magnet （PM） motors obtained using an analytical technique, the instantaneous electromagnetic torque and its corresponding components are investigated with the Maxwell stress tensor method. Accurate results can easily be achieved using the proposed method without using the tedious finite element analysis （FEA）. In this paper, the electromagnetic torque of a surface mounted PM motor with two phases energized is decomposed into four torque components. This technique is useful not only for the design and optimization of the permanent magnet motor, but also for the choice of control strategy.

Finite element simulation for mechanical response of surface mounted solder joints under different temperature cycling

Nonlinear finite element simulation for mechanical response of surface mounted solder joint under different temperature cycling was carried out. Seven sets of parameters were used in order to evaluate the influence of temperature cycling profile parameters. The results show that temperature cycling history has significant effect on the stress response of the solder joint. Based on the concept of relative damage stress proposed by the authors, it is found that enough high temperature holding time is necessary for designing the temperature cycling profile in accelerated thermal fatigue test.

CALCULATION OF THREE－DIMENSIONAL SOLDER JOINT FORMATION IN MICROELECTRONIC SURFACE MOUNT TECHNOLOGY

A finite element analysis for calculating three-dimensional(3-D) solder joint shape between chip component and substrate pad was carried out, and the effects of solder volume and pad extension beyond the edge of component on solder joint shapes were investigated. The resonable design ranges of solder volume and pad extension have been put forward.

High-Speed,High-Power Motor Design for a Four-Legged Robot Actuator Optimized using the Weighted Sum and Response Surface Methods

In this paper,a design is presented for a high-speed,high-power motor for a four-legged robot actuator that was optimized using the weighted sum method(WSM)based on the Taguchi method,and the response surface method(RSM).First,output torque,torque constant,torque ripple,and efficiency were selected as objective functions for the optimized design.The sampling method was implemented to use a mixed orthogonal array and the single response characteristics of each objective function were compared using the Taguchi method.Moreover,to consider the multi-response characteristic of the objective functions,WSM was applied.Second,the 2D finite element analysis result of the RSM was compared with that using the WSM.Finally,an experiment was carried out on the manufactured motor and the optimized model is presented here.

Study on surfce mount technology for fine pitch L type lead devices

Problems about surface mounting process for fine pitch devices and reasons on solder bridging of L type lead devices welded are depicted. Bridging mechanism and influence factors are analyzed with two-dimensional geometric model. Based on this, high-density surface mount technology ( SMT) for fine pitch L type lead devices heated by scanning laser is raised. Surface mount process for QFP208 on printed circuit board (PCB) is studied. The results of tests are that it is quite possible to solve the solder bridging of surface mounting for fine pitch devices with scanning laser-heating method.

Adaptive Lagrange finite element methods for high precision vibrations and piezoelectric acoustic wave computations in SMT structures and plates with nano interfaces

This paper discusses the validity of (adaptive) Lagrange generalized plain finite element method (FEM) and plate element method for accurate analysis of acoustic waves in multi-layered piezoelectric structures with tiny interfaces between metal electrodes and surface mounted piezoelectric substrates. We have come to conclusion that the quantitative relationships between the acoustic and electric fields in a piezoelectric structure can be accurately determined through the proposed finite element methods. The higher-order Lagrange FEM proposed for dynamic piezoelectric computation is proved to be very accurate (prescribed relative error 0.02% - 0.04% ) and a great improvement in convergence accuracy over the higher order Mindlin plate element method for piezoelectric structural analysis due to the assumptions and corrections in the plate theories.The converged lagrange finite element methods are compared with the plate element methods and the computedresults are in good agreement with available exact and experimental data. The adaptive Lagrange finite elementmethods and a new FEA computer program developed for macro- and micro-scale analyses are reviewed, and recently extended with great potential to high-precision nano-scale analysis in this paper and the similarities between piezoelectric and seismic wave propagations in layered structures and plates are stressed.

Test research and mechanism analysis of vacuum fluxless laser soldering for SMD

Fluxless soldering can solve a series of problems caused by side-effects afflux essentially. Feasibility research on vacuum fluxless laser soldering and mechanism analysis on fluxless action of vacuum were carried out. Fluxless soldering succeeded in spreading and wetting on Cu pad with laser heating source in vacuum surroundings. What' s more, this fluxless technology was applied in surface mounting of chip resistance successfully.

Load Optimization Scheduling of Chip Mounter Based on Hybrid Adaptive Optimization

A chip mounter is the core equipment in the production line of the surface-mount technology,which is responsible for finishing the mount operation.It is the most complex and time-consuming stage in the production process.Therefore,it is of great significance to optimize the load balance and mounting efficiency of the chip mounter and improve the mounting efficiency of the production line.In this study,according to the specific type of chip mounter in the actual production line of a company,a maximum and minimum model is established to minimize the maximum cycle time of the chip mounter in the production line.The production efficiency of the production line can be improved by optimizing the workload scheduling of each chip mounter.On this basis,a hybrid adaptive optimization algorithm is proposed to solve the load scheduling problem of the mounter.The hybrid algorithm is a hybrid of an adaptive genetic algorithm and the improved ant colony algorithm.It combines the advantages of the two algorithms and improves their global search ability and convergence speed.The experimental results show that the proposed hybrid optimization algorithm has a good optimization effect and convergence in the load scheduling problem of chip mounters.

Study on Strengthening of RC Slabs with Different Innovative Techniques

This paper presents a focused study on using different methods to enhance the ultimate capacity of flexural behavior in RC slabs. Four RC specimens were casted with common compressive strength and reinforced with steel mesh. Specimens were strengthened with different methods such as usage of GFRP sheets, carbon fibers laminate strips and near surface mounted steel rebars. All specimens were subjected to two-point loading setup. Load was increased from zero to failure load. First crack was recorded and crack pattern was observed. The behavior of strengthened specimens was compared to that of the control specimen to judge the efficiency of the used techniques. Test results showed that the used techniques were effective in enhancing the behavior of the strengthened slabs by noteworthy values.

A Microwave Ceramic Band-Pass Filter for Mobile Communications with New Coupling Structure

A surface mounted device （SMD） microwave ceramic band-pass filter for mobile communication with a new coupling structure is reported in this paper. In this filter, the external and internal coupling structures are fabricated on an alumina substrate and both resonators and coupling structures are placed into a metal house to cut off its radiation. The relationship between the coupling structures and the performance of the filter is analyzed by high frequency structure software （HFSS） and the filter with a center frequency of 836.5 MHz, bandwidth of 40.0 MHz, pass-band ripple of 0.1 dB and insertion loss of 1.5 dB has been successfully designed and fabricated. The measured results show a good agreement with the simulation results.