• Proceedings of the KWS Conference
• /
• 2007.11a
• /
• pp.245-247
• /
• 2007

Sn-base solder bump is mainly used in micro-joining for flip chip package. The quantity of intermetallic compounds that was formed between Cu pad and solder interface importantly affects reliability. In this research, micro-bump was fabricated by two binary electroplating and the intermetallic compounds(IMCs) was estimated quantitatively. When the micro Sn-Ag solder bump was made by electroplating, SiC powder was added in the plating solution for protecting of intermetallic growth. Then, the intermetallic compounds growth was decrease with increase of amount of SiC power. However, if the mount of SiC particle exceeds 4 g/L, the effect of the growth restraint decrease rapidly.

• Proceedings of the KWS Conference
• /
• 2005.06a
• /
• pp.367-369
• /
• 2005

For the purpose of the optimization or the break through of production processes, it is essential to understand or theoretically interpret dominant mechanisms of the processes, and further more, archive them. and utilize them combining some of them which are needed. Especially in the technology for micro- or nano-scaled objects, adhesion phenomenon is no more negligible, because the adhesion force is proportional to the size of objects meanwhile gravity force is proportional to the third power of it. Author has been working about the mechanisms for micro-assembly processes, which include joining processes and manipulation processes. In the present paper, the strategy and the progress to establish the micro-assembly technology archive are introduced. Some of the mechanisms are introduced with related basic approaches to the adhesion phenomena. Also it will be expressed that our data base project for the surface and interfacial energies is strongly related to these basic approaches.

• International Journal of Korean Welding Society
• /
• v.3 no.1
• /
• pp.29-33
• /
• 2003

The ferritic stainless steels are generally considered to have poor weldability compared with that of the austenitic stainless steels. However the primary advantages of ferritic stainless steels include lower material cost than the more commonly used austenitic stainless steels and a greater resistance to stress corrosion cracking. Thus, the weldability of ferritic stainless steels was investigated in this study. In concerning the weldability, Grain size measurement test, Erichsen test and Varestraint test were involved. full penetration welds were produced by autogeneous direct current straight polarity (DCSP) and pulsed currents gas tungsten arc welding (GIAW) and the effect of pulsed currents welding on the welds was compared to that of DCSP welding. The results showed that pulsed current was effective to refine grain size in the weld metal and the finest grain size was obtained at the frequency of 150Hz. In addition, the ductility of welds was lower than that of base metal. Finally, autogeneous type 444 welds were less susceptible to macro solidification cracks, but more sensitive to micro cracks; SEM/EDS analysis indicated that all the inclusions in the crack showed enrichment of Mn, Si, O and S.

• Journal of the Korean Society for Railway
• /
• v.12 no.4
• /
• pp.512-517
• /
• 2009

Extruded aluminium panels have been widely used for railway vehicle structures because -of their light specific weight and other merits. In the past, GMAW (Gas Metal Arc Welding) and GTAW (Gas Tungsten Arc Welding) were mainly used to join aluminium panels. But recently friction stir welding (FSW) is widely used due to its lots of advantage. In this study aluminium A6005 which is used for car body structures was chosen. The influences of main parameters on mechanical properties such as: pin (tool) rotating speed, pin transition speed, shoulder, diameter, pin length and tilting angle were examined. Optical microscope and scanning electron microscope (SEM) observation, micro hardness tests, and tensile tests were carried out.

• Journal of Welding and Joining
• /
• v.28 no.5
• /
• pp.51-57
• /
• 2010

Brittle microstructure created in a heat affected zone (HAZ) during the welding of low alloy steel can be eliminated by post-weld heat treatment (PWHT). If the PWHT is not possible during a repair welding, the controlled bead depositions of multi-pass welding should be applied to obtain tempering effect on the HAZ without PWHT. In order to anticipate and control the tempering effect during the temper bead welding, the definition of temperature curve obtained from the analytical solution was suggested in this research. Because the analytical solution for heat flow is expressed as a mathematical equation of weld parameters, it may be effective in anticipating the effect of each weld parameter on the tempering in HAZ during the successive bead depositions. The reheating effect by the successive bead layer on the brittle coarse grained HAZ formed by earlier bead deposition was estimated by comparing the overlapped distance between the temperature curves in the HAZ. Three layered weld specimens of SA508 base metal with A52 filler were prepared by controlling heat input ratio between layers. The tempering effect anticipated by using the overlapped distance between the temperature curves was verified by measuring the micro-hardness distribution in the HAZ of prepared specimens. The temperature curve obtained from analytical solution was expected as a good tool to find optimal temper bead welding conditions.

• Journal of Welding and Joining
• /
• v.33 no.3
• /
• pp.19-24
• /
• 2015

Joint properties of electric control unit (ECU) module using Sn-Cu-(X)Al(Si) lead-free solder alloy were investigated for automotive electronics module. In this study, Sn-0.5Cu-0.01Al(Si) and Sn-0.5Cu-0.03Al(Si) (wt.%) lead-free alloys were fabricated as bar type by doped various weight percentages (0.01 and 0.03 wt.%) of Al(Si) alloy to Sn-0.5Cu. After fabrications of lead-free alloys, the ball-type solder alloys with a diameter of 450 um were made by rolling and punching. The melting temperatures of 0.01Al(Si) and 0.03Al(Si) were 230.2 and $230.8^{\circ}C$, respectively. To evaluation of properties of solder joint, test printed circuit board (PCB) finished with organic solderability perseveration (OSP) on Cu pad. The ball-type solders were attached to test PCB with flux and reflowed for formation of solder joint. The maximum temperature of reflow was $260^{\circ}C$ for 50s above melting temperature. And then, we measured spreadability and shear strength of two Al(Si) solder materials compared to Sn-0.7Cu solder material used in industry. And also, microstructures in solder and intermetallic compounds (IMCs) were observed. Moreover, thickness and grain size of $Cu_6Sn_5$ IMC were measured and then compared with Sn-0.7Cu. With increasing the amounts of Al(Si), the $Cu_6Sn_5$ thickness was decreased. These results show the addition of Al(Si) could suppress IMC growth and improve the reliability of solder joint.

• Journal of Welding and Joining
• /
• v.32 no.3
• /
• pp.68-73
• /
• 2014

Among through silicon via (TSV) technologies, for replacing Cu filling method, the method of molten solder filling has been proposed to reduce filling cost and filling time. However, because Sn alloy which has a high coefficient of thermal expansion (CTE) than Cu, CTE mismatch between Si and molten solder induced higher thermal stress than Cu filling method. This thermal stress can deteriorate reliability of TSV by forming defects like void, crack and so on. Therefore, we fabricated SiC composite filling material which had a low CTE for reducing thermal stress in TSV. To add SiC nano particles to molten solder, ball-typed SiC clusters, which were formed with Sn powders and SiC nano particles by ball mill process, put into molten Sn and then, nano particle-dispersed SiC composite filling material was produced. In the case of 1 wt.% of SiC particle, the CTE showed a lowest value which was a $14.8ppm/^{\circ}C$ and this value was lower than CTE of Cu. Up to 1 wt.% of SiC particle, Young's modulus increased as wt.% of SiC particle increased. And also, we observed cross-sectioned TSV which was filled with 1 wt.% of SiC particle and we confirmed a possibility of SiC composite material as a TSV filling material.

• Journal of the Korean Society for Precision Engineering
• /
• v.32 no.10
• /
• pp.891-896
• /
• 2015

In order to protect the environment, using light material is becoming more and more attractive within the automobile industry. Aluminum alloys are the best and lightest metallic materials used in the automotive, electron, and aerospace industries. Al alloy and SGARC were joined by cold metal transfer (CMT) welding, using AlSiMn4 as a filler. Results showed that dissimilar metals from the Al 6000 series/SGARC could be successfully joined by CMT under proper processing parameters. The micro-hardness value of 125Hv was obtained at an interface.

• Journal of the Korean Society of Manufacturing Technology Engineers
• /
• v.9 no.4
• /
• pp.131-136
• /
• 2000

This study deals with the mechanical properties of STS304-Al351 friction welding zone. Main results are as follows ; under the condition of upset pressure 75MPa, the tensile strength of STS304-al6351 friction weld interface was higher than that of Al6351 base metal, and the highest tensile strength(290MPa) was obtained at upset pressure 125MPa. The hardness profile across the weld interface shows that the hardness of both STS304 and Al6351 is higher around the weld interface, and sharply increased hardness on the STS304 side is related with the plastic deformation of micro volume. As the result of analyzing the tensile fracture, it showed perfect soft fracture.

• Journal of Welding and Joining
• /
• v.13 no.3
• /
• pp.96-105
• /
• 1995

An advantage offered by brazing over fusion welding is that strong joints may be produced at relatively low heat input. To minimize the thermal effects and maintain the desired dimension of assemblies. the CO$_{2}$ laser beam can be applied to the brazed joint of pin and plate as a micro heat source. This paper presents a analysis model of the laser brazing process considering the laser beam mode and heat flow in brazed parts by using the finite element method. The simulation results were compared with the experimental results obtained from the infrared temperature sensing system. Based on these results, the proper process parameters were investigated to get a good joining quality. The influence of the beam mode change was examined with respect to the temperature distribution and joint quality.