• Proceedings of the International Microelectronics And Packaging Society Conference
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• 2002.05a
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• pp.117-120
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• 2002

In this paper, several methods to predict the solder joint shape are studied. Although there are various methods to predict the solder joint shape, such as truncated sphere method, force-bal tranced analytical solution, and energy-based methods like surface evolver developed by Ken Brakke, we calculate solder joint shape of $\mu$BGA by two solder joint shape prediction methods(truncated sphere method and surface evolver) and then compare results of each method. The results in dicate that two methods can accurately predict the solder joint shape in an accurate range. After that, we calculate reliability solder joint shape under thermal cycle test by FEA program ANSYS. As a result, it could be found that optimal solder joint shape calculated by solder joint prediction method has best reliability in thermal cycle test.

• Journal of the Microelectronics and Packaging Society
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• v.8 no.4
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• pp.35-41
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• 2001

In this paper, several methods to predict the solder joint shape are studied. Although there are various methods to predict the solder joint shape, such as truncated sphere method. force-balanced analytical solution, and energy-based methods like surface evolver developed by Ken Brakke, we calculate solder joint shape of $\mu$BGA by two solder joint shape prediction methods(truncated sphere method and surfaceevolver) and then compare results of each method. The results indicate that two methods can accurately predict the solder Joint shape in an accurate range. After that, we calculate reliability solder joint shape under thermal cycle test by FEA program ANSYS(version 5.62). As a result, it could be found that optimal solder joint shape calculated by solder joint prediction method has best reliability in thermal cycle test.

• 제어로봇시스템학회:학술대회논문집
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• 1996.10b
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• pp.117-120
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• 1996

In this paper, a new approach to acquire the cross-sentional image for automatic solder joint inspection of double-sided PCB using X-ray source is presented. We designed the apparatus with fixed X-ray source to realize the cross-sectional image by tunning object and detector synchronously. The cross-sectional images are captured at several view angle of X-ray source, the geometric image distortions caused by view angle and the shape of image intensifier are compensated. The precision variation of cross-sectional image by the change of view angle was investigated. Also we acquired the cross-sectional image to the solder joint of double-sided PCB and reconstructed the shape of solder joint.

• Proceedings of the KWS Conference
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• 1995.10a
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• pp.145-148
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• 1995

To provide better understanding of a solder joint design criteria, mathematical models have been developed to calculate the shape of the solder fillets formed between the pad and lead. The effects of parameters such as solder volume and pad dimensions are described with this model. In this study, a systematic way to determine the design criteria of the SMT from the predicted 3D solder joint profile is proposed. The solder joint profile is calculated using the available 3D FEM code which minimizes the system energy due to the surface tension and gravity. The solder joint profiles of gullwing-type lead such as QFP and SOP are calculated for design parameters, and acceptable ranges are obtained. The result shows that the pad length is the most significant factor compared with the pad width and pad area.

• Journal of Welding and Joining
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• v.17 no.6
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• pp.78-83
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• 1999

Solder joint is the weakest part which connects in mechanically and electronically between package body and PCB(Printed Circuit Board). Recently, the reliability of solder joint become the most critical issue in surface mounted technology. The solder joint interconnection between plastic package and PCB is susceptible to shear stress during thermal storage due to the mismatch in coefficient of thermal expansion between plastic package and PCB. A general computational approach to determine the effect of solder joint shape on the fatigue life presented. The thermal fatigue life was estimated from the engelmaier equation which was obtained from the temperature cycling loading($-65^{\circ}C$ to $150^{\circ}C$). As result of the simulation, TSOP structure has the shortest thermal fatigue life and the same structure Copper lead has 2.5 times as much fatigue life as Alloy 42 lead. In BGA structure, fatigue life time extended 80 times when underfill material exists.

• Journal of Institute of Control, Robotics and Systems
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• v.6 no.8
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• pp.710-718
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• 2000

In this paper we described an approach to automation of visual inspection of solder joint defects of SMC(Surface Mounted Components) on PCBs(Printed Circuit Board) by using neural network and fuzzy rule-based classification method. Inherently the surface of the solder joints is curved tiny and specular reflective it induces difficulty of taking good image of the solder joints. And the shape of the solder joints tends to greatly vary with the soldering condition and the shapes are not identical to each other even though the solder joints belong to a set of the same soldering quality. This problem makes it difficult to classify the solder joints according to their qualities. Neural network and fuzzy rule-based classification method is proposed to effi-ciently make human-like classification criteria of the solder joint shapes. The performance of the proposed approach is tested on numerous samples of commercial computer PCB boards and compared with the results of the human inspector performance and the conventional Kohonen network.

• Proceedings of the KWS Conference
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• 2002.10a
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• pp.439-449
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• 2002

This paper reviews our recent research works on the interconnection technologies in electronic packaging and assembly. At the aspect of advanced joining methods, laser-ultrasonic fluxless soldering technology was proposed. The characteristic of this technology is that the oxide film was removed through the vibration excitated by high frequency laser change in the molten solder droplet. Application researches of laser soldering technology on solder bumping of BGA packages were carried out. Furthermore, interfacial reaction between SnPb eutectic solder and Au/Ni/Cu pad during laser reflow was analyzed. At the aspect of soldered joints' reliability, the system for predicting and analyzing SMT solder joint shape and reliability(PSAR) has been designed. Optimization design method of soldered joints' structure was brought forward after the investigation of fatigue failure of RC chip devices and BGA packages under temperature cyclic conditions with FEM analysis and experimental study. At the aspect of solder alloy design, alloy design method based on quantum was proposed. The macroproperties such as melting point, wettability and strength were described by the electron parameters. In this way, a great deal of the experimental investigations was replaced, so as to realize the design and research of any kinds of solder alloys with low cost and high efficiency.

• 제어로봇시스템학회:학술대회논문집
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• 1996.10b
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• pp.264-267
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• 1996

This paper is aimed to develop a very reliable method for automatic inspection of the solder joints on PCBS. There have been lots of previous works using vision technologies, but they can not be used for inspecting BGA, FCA or other newly used devices. Thus we adopt X-ray technologies for solder joint inspection. We put our attention on reconstructing the 3D shapes of solder joints since it gives us the most detailed information on quality of solder joints. Laminography principle is used to reject the interferences from neighboring parts or leads. To verify the effectiveness of laminography, a simulation study is performed in the case of a solder joints on double sided PCB using.

• Journal of the Microelectronics and Packaging Society
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• v.22 no.1
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• pp.69-74
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• 2015

With difficulties during the cleaning of reflow flux residues due to the decrease of the part size and interconnection pitch in the advanced electronic devices, the need for the no-clean solder paste is increasing. In this study, an epoxy curable solder paste was made with SAC305 solder powder and the curable flux of which the main ingredient is epoxy resin and its reflow solderability, flux residue corrosivity and solder joint mechanical properties was investigated with comparison to the commercial rosin type solder paste. The fillet shape of the cured product around the reflowed solder joint revealed that the curing reaction occurred following the fluxing reaction and solder joint formation. The copper plate solderability test result also revealed that the wettability of the epoxy curable solder paste was comparable to those of the commercial rosin type solder pastes. In the highly accelerated temperature and humidity test, the cured product residue of the curable solder paste showed no corrosion of copper plate. From FT-IR analysis, it was considered to be resulted from the formation of tight bond through epoxy curing reaction. Ball shear, ball pull and die shear tests revealed that the adhesive bonding was formed with the solder surface and the increase of die shear strength of about 15~40% was achieved. It was considered that the epoxy curable solder paste could contribute to the improvement of the package reliability as well as the removal of the flux residue cleaning process.

• Proceedings of the International Microelectronics And Packaging Society Conference
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• 1999.12a
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• pp.63-85
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• 1999

$\cdot$New CSP using Lead Frame and solder ball techniques. $\cdot$EMC needs high filler content, low CTE and high flexural modulus. $\cdot$Solder Joint Reliability improved by anchor leads. .Uniform inner lead shape would be better at capacitance values. $\cdot$Low Assembly cost CSP.