• Journal of the Microelectronics and Packaging Society
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• v.17 no.1
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• pp.25-31
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• 2010

In this study, we investigated the morphology and thermal stability of interfacial phases in joint between lead free solder(Sn-3.0Ag-0.5Cu) and electroless Ni-W-P under bump metallizations(UBM) with different tungsten contents as a function of thermal aging. Content of phosphorus of each deposits was fixed at 8 wt.%, and content of tungsten was variated each 0, 3, 6 and 9 wt.%. Specimens were prepared by reflowing at $255^{\circ}C$, aging range was $200^{\circ}C$ and up to 2 weeks. After reflow process, in the electroless Ni(W)-P/solder joint, the interfacial intermetallic compound(IMC) was showed both $(Cu,Ni)_6Sn_5$ and $(Ni,Cu)_3Sn_4$. UBM and generated IMC at the interface of lead free solder was proportionally increased with aging time. The thickness of IMC was increased because the generation rate of $Ni(W)_3P$ decreased with increasing contents of W.

• Journal of Powder Materials
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• v.4 no.3
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• pp.196-204
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• 1997

Joining of AIN ceramics to W and Cu by active-metal brazing method was tried with use of (Ag-Cu)-Ti alloy as insert-metal. Joints were produced under various conditions of temperature, holding time and Ti-content in (Ag-Cu) alloy Reaction and microstructural development in bonded interface were investigated through observation and analysis by SEM/EDS, EPMA and XRD. Joint strengths were measured by shear test. Bonded interface consists of two layers: an insert-metal layer of eutectic Ag- and Cu-rich phases and a reaction layer of TiN. Thickness of reaction layer increases with bonding temperature, holding time and Ti-content of insert-metal. It was confirmed that the growth of reaction layer is a diffusion-controlled process. Activation energy for this process was 260 KJ/mol which is lower than that for N diffusion in TiN. Maximum shear strength of 108 MPa and 72 MPa were obtained for AIN/W and AIN/Cu joints, respectively. Relationship between processing variables, joint strength and thickness of reaction layer was also explained.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2013.05a
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• pp.841-842
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• 2013

• Journal of Welding and Joining
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• v.17 no.5
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• pp.69-76
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• 1999

A copper-tungsten sintered alloy(Cu-W) has been friction welded to a tough pitch copper in order to investigate the effect of upset pressure on friction weldability. Under the condition of friction time 0.8sec, upset pressure 150MPa, the tensile strength and Charpy impact value of the friction welded joint were 336MPa, $400KJ/m^2$ respectively. And highest temperature of the weld measured was below $800^{circ}K$ which is very lower than melting point of Cu($1356^{circ}K$). Under the same conditions, W grains picked up in Cu matrix from Cu-W profitably affected on these mechanical fracture, and were dispersed in Cu by plastic flow during brake time.

• Proceedings of the International Microelectronics And Packaging Society Conference
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• 2004.02a
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• pp.37-59
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• 2004

In the case of Ni/Au finished pad on the package side, the solder joint of SnAgCu system can bring brittle fracture under impact load such as drop test. Therefore, it's difficult to prevent the brittle fracture of lead-free solder, by controlling Cu content. The failure locus existing on the interface between $(Ni,Cu)_3Sn_4\;and\;(Cu,Ni)_6Sn_5$ IMC layers must be changed to other site in order to avoid brittle fracture due to impact load. It was not found any clear evidence that there were two IMC layers exist. But it was strongly assumed these were two layers which have different Cu-Ni composition. From the above analysis it was assumed that Cu atom in the solder alloy or substrate seemed to affect IMC composition and cause to IMC brittle fracture.

• Journal of Welding and Joining
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• v.15 no.4
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• pp.90-98
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• 1997

A copper-tungsten sintered alloy(Cu-W) has been friction welded to a tough pitch copper in order to investigate the effect of friction pressure on bonding strength and a charicteristic of fracture. The tensile strength of the friction welded joint was increased up to 90% of the Cu base metal under the condition of friction time 1.2 sec, friction pressure 4.5kgf/$\textrm{mm}^2$ and upset pressure 10kgf/$\textrm{mm}^2$. From the results of fracture surface analysis, the increase of friction pressure could remarkably decrease the force and the time to be normally acted on weld interface. The W particles which were included in the plastic zone of Cu side could induce fracture adjacent to the weld interface because their existance in Cu induces a decrease in available section area and an increase in notch effect. Therefore, the tensile strength was decreased at high friction pressure (6kgf/$\textrm{mm}^2$) because the destruction of W was increased by an increase in mechanical force and crack was formed at weld interface.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.17 no.3
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• pp.267-271
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• 2004

The joint strength and fracture surface of Sn-Pb solder bump in photo diode packages after isothermal aging testing were studied experimentally. Cu/Sn-Pb solders were adopted, and aged for up to 900 hours at 12$0^{\circ}C$ and 17$0^{\circ}C$ to analyze the effect of intermetallic compound(IMC). In 900-hour aging experiments, the maximum shea strength of Sn-Pb solder decreased by 20％ and 9％. The diffraction patterns of Cu$_{6}$Sn$_{5}$, scallop-shape IMC, and planar-shape Cu$_3$Sn were observed by Transmission Electron Microscopy (TEM).EM).

• Proceedings of the KWS Conference
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• 2002.10a
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• pp.620-625
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• 2002

Considering the fuel consumption of car, a light structure of aluminum alloys is desired for car body nowadays. However, fusion welding of aluminum alloys has some problems of reduction of joint efficiency, porosity formation and hot cracking. ill the present work, investigation to improve the joint performance of laser welded joint has been carried out by addition of Cu, Ni, and Zr to A6N01 alloy welds. Aluminum alloy plate of 2.0mm in thickness with filler metal bar was welded by twin beam Nd:YAG laser facility (total power:5kW). The filler metals were prepared by changing the chemical compositions for adding the elements into the weld metal. Thirteen filler metal bars were prepared and pre-placed into the base metal before welding. Ar gas shielding with a flow rate of 10 l/min was used. The defocusing distance is kept at 0 mm. At travel speeds of 3 to 9 m/min and at laser power of 5kW (front beam 2kW rear beam 3kW), full penetration welds were obtained, whereas at travel speeds of 12 to 18 m/min and same power, partial penetration was observed. The joint efficiency of laser-welded joint was improved by the addition of Cu, Ni, and Zr due to the solid solution hardening, grain refining and precipitation hardening. The type of hardening has been further considered by metallurgical examination.

• International Journal of Korean Welding Society
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• v.2 no.2
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• pp.26-31
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• 2002

Considering the fuel consumption of car, a light structure of aluminum alloys is desired fer car body nowadays. However, fusion welding of aluminum alloys has some problems of reduction of joint efficiency, porosity formation and hot cracking. In the present work, investigation to improve the joint performance of laser welded joint has been carried out by addition of Cu, Ni, and Zr to A6NO 1 alloy welds. Aluminum alloy plate of 2.Omm in thickness with filler metal bar was welded by twin beam Nd: YAG laser facility (total power: 5kW). The filler metals were prepared by changing the chemical compositions for adding the elements into the weld metal. Thirteen filler metal bars were prepared and pre-placed into the base metal before welding. Ar gas shielding with a flow rate of 10 1/min was used. The defocusing distance is kept at 0 mm. At travel speeds off 3 to 9 and at laser power of 5kW (front beam 2kW rear beam 3kW), full penetration welds were obtained, whereas at travel speeds of 12 to 18 m/min and same power, partial penetration was observed. The joint efficiency of laser-welded joint was improved by the addition of Cu, Ni, and Zr due to the solid solution hardening, grain refining and precipitation hardening. The type of hardening has been further considered by metallurgical examination.

• Journal of Welding and Joining
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• v.17 no.3
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• pp.79-89
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• 1999

The study was carried out to examine in more detail metallurgical and mechanical properties of brazed joints of diamond cutting wheel. In this work, shank(mild steel) and sintered bronze-base tips were brazed with three different filler materials(W-40, BAgl and BAg3S). The machine used in this work was a high frequency induction brazing equipment. The joint thickness, porosities and microstructure of brazed joints with brazing variables(brazing temperature, holding time) were evaluated with OLM, SEM, EDS and XRD. Bending(torque) test was also performed to evaluate strength of brazed joints. Further wetting test was performed in a vacuum furnace in order to evaluate the wettability of filler metals on base metals9shank and tips). The brazing temperature had a strong influence on the joint strength and the optimum brazing temperature range was about $700~850^{\circ}C$ for the bronze/steel combinations. The strength of the brazed joint was found to be influenced by the three factors : degree of reaction region, porosity content, joint thickness. The reaction region was formed in the bronze-base tip adjacent to the joint. The reaction region resulted in a bad influence on the strength due to the formation of Cu5.6Sn, CuZn4, $\beta(CuZn)$ and CdAg, etc. Porosities increased as brazing variables(brazing temperature, holding time) increased, and the brazed joints with porosities of less than about 3-5% had an optimum strength for the bronze-base tip.