• Journal of the Microelectronics and Packaging Society
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• v.22 no.3
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• pp.19-23
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• 2015

In this study, two types of Au/TiW bump samples were fabricated by the electroplating process onto Al/Si and SiN/Si wafers for the COG (Chip On Glass) packaging. TiW was used as the UBM (Under Bump Metallurgy) material of the Au bump and it was deposited by a sputtering method under the sputtering powers ranges from 500 to 5000 Watt. We investigated the delamination phenomenas for the prepared samples as a function of the input sputtering powers. The stable interfacial adhesion condition was found to be 1500 Watt in sputtering power. In addition, the SAICAS (Surface And Interfacial Cutting Analysis System) measurement was used to find the adhesion strength of Au bumps for the prepared samples. TiW UBM films were deposited at the 1500 Watt sputtering power. As a results, there was a similar adhesion strengths between TiW/Au interfacial films on Al/Si and SiN/Si wafers. However, the adhesion strength of TiW UBM sputtering films on Al and SiN under films were 2.2 times differences, indicating 0.475 kN/m for Al/Si wafer and 0.093 kN/m for SiN/Si wafer, respectively.

• Proceedings of the KWS Conference
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• 2002.10a
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• pp.469-474
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• 2002

Laser and hot air reflow soldering of PBGA solder ball was investigated. Experimental results showed that surface quality and shear strength of solder bumps reflowed by laser was superior than the solder bumps reflowed by hot air, and the microstructure inside the solder bumps reflowed by laser was much finer. Analysis on interfacial reaction showed that eutectic solder reacted with Au/Ni/Cu pad shortly after the solder was melted. Interface of solder bump reflowed by laser consists of a continuous AuSn$_4$ layer and remnant Au element. Needle-like AuSn$_4$ grew sidewise from interface, and then spread out to the entire interface region. A thin layer of Ni$_3$Sn$_4$ intermetallic compound was found at the interface of solder bump reflowed by hot air, AuSn$_4$ particles distributed inside the whole solder bump randomly. It is the combination effect of the continuous AuSn$_4$ layer and finer eutectic microstructure inside the solder bump reflowed by laser that resulted in higher shear strength.

• Proceedings of the International Microelectronics And Packaging Society Conference
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• 2003.11a
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• pp.68-71
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• 2003

The reaction of ultra-small eutectic 58Bl-42Sn solder bump with Au/Ni/Ti and Au/Cu/Ti UBMs during reflow was studied. The eutectic Bi-Sn solder bumps of $46{\mu}m$ diameter were fabricated by using the evaporation method and were reflowed using the rapid thermal annealing system. The intermetallic compound was characterized using a SEM, an EDS, and an XRD. The $(Cu_xAu_{1-x})_6Sn_5$ compounds formed at the interface between Bi-Sn solder and Au/Cu/Ti UBM. On the other hand, in the Bi-Sn solder bump on Au/Ni/Ti UBM, the faceted and rectangular intermetallic compounds were observed on the solder bump surface and inside the solder bump as well as at the UBM interface. These intermetallic compounds were Identified as $(Au_{l-x-y}Bi_xNi_y)Sn_2$ phase.

• Journal of Welding and Joining
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• v.22 no.1
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• pp.65-70
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• 2004

A soldering process with longitudinal ultrasonic is conducted in this work using the Au bump and substrate. Localized heating of the solder is achieved and the stirring action due to the ultrasonic is found to influence the bond strength and microstructure of the eutectic solder The acceptable bonding condition is determined from the tensile strength. Since the multiple bonds can be formed simultaneously with localized heating, the proposed ultrasonic soldering method appears to be applicable to the high-density electronic package.

• Proceedings of the KWS Conference
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• 2006.10a
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• pp.181-183
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• 2006

This paper studies the mechanical behaviors of Sn-3.5Ag solder joint against substrate(such as Au/Ni/Cu, Au/cu, Ni/Cu and Cu pad) after induction heating, a new soldering method. It was found that the solder bump formation depends on the time and current of the induction heating system. Also the heating value of the solder bump were found to vary with respect to the thermal conductivity of the pads on the substrate. In case of Au/Ni/Cu pad and Au/Cu pad, solder bump's shear strength were high for the heating time of $1.5{\sim}2sec$. For Ni/Cu pad, solder bump's shear strength were found to increase with time increment.

• Journal of the Microelectronics and Packaging Society
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• v.15 no.4
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• pp.9-15
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• 2008

Microstructure and contact resistance of the Au-Sn solder joints were characterized after flip-chip bonding of the Au/Sn bumps processed by successive electrodeposition of Au and Sn. Microstructure of the Au-Sn solder joints, formed by flip-chip bonding at $285^{\circ}C$ for 30 sec, was composed of the $Au_5Sn$+AuSn lamellar structure. The interlamellar spacing of the $Au_5Sn$+AuSn structure increased by reflowing at $310^{\circ}C$ for 3 min after flip-chip bonding. While the Au-Sn solder joints formed by flip-chip bonding at $285^{\circ}C$ for 30 sec exhibited an average contact resistance of 15.6 $m{\Omega}$/bump, the Au-Sn solder joints reflowed at $310^{\circ}C$ for 3 min after flip-chip bonding possessed an average contact resistance of 15.0 $m{\Omega}$/bump.

• Journal of Welding and Joining
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• v.22 no.3
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• pp.62-68
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• 2004

The strip Au bumps are bonded using longitudinal ultrasonic far the electronic package. Au bumps on the chip and substrate are aligned in a crossed shape, and the ultrasonic is imposed on the chip to form the solid-state bond between the Au bumps. Deformed bump shapes are calculated using the finite element method, and the bond strength is measured experimentally. The crossed strip Au bumps are deformed similar to the saddle, which provides larger contact surface area and higher friction force. Compared with the previous bonding method between the Au bump and planar pad, higher bond strength is obtained using the crossed strip bumps.

• Journal of Welding and Joining
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• v.29 no.6
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• pp.65-70
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• 2011

The effect of flip chip bonding parameters on formation of intermetallic compounds (IMCs) between Au stud bumps and Sn-3.5Ag solder was investigated. In this study, flip chip bonding temperature was performed at $260^{\circ}C$ and $300^{\circ}C$ with various bonding times of 5, 10, and 20 sec. AuSn, $AuSn_2$ and $AuSn_4$ IMCs were formed at the interface of joints and (Au, Cu)$_6Sn_5$ IMC was observed near Cu pad side in the joint. At bonding temperature of $260^{\circ}C$, $AuSn_4$ IMC was dominant in the joint compared to other Au-Sn IMCs as bonding time increased. At bonding temperature of $300^{\circ}C$, $AuSn_2$ IMC clusters, which were surrounded by $AuSn_4$ IMC, were observed in the solder joint due to fast diffusivity of Au to molten solder with increased bonding temperature. Bond strength of Au stud bump joined with Sn-3.5Ag solder was about 23 gf/bump and fracture mode of the joint was intergranular fracture between $AuSn_2$ and $AuSn_4$ IMCs regardless bonding conditions.

• Journal of the Microelectronics and Packaging Society
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• v.17 no.2
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• pp.55-61
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• 2010

The device with tantalum silicide heater were bonded by Ag paste and Au SBB(Stud Bump Bonding) onto the Au coated substrate. The shear test after Au ABB and the thermal performance under current stressing were measured. The optimum condition of Au SBB was determined by fractured surface after die shear test and $350^{\circ}C$ for substrate, $250^{\circ}C$ for die during flip chip bonding with bonding load of about 300 g/bump. With applying 5W through heater on the device, the maximum temperature with Ag paste bonding was about $50^{\circ}C$. That with Au SBB on Au coated Si substrate showed $64^{\circ}C$. The difference of maximum temperatures is only $14^{\circ}C$, even though the difference of contact area between Ag paste bonding and Au SBB is by about 300 times and the simulation showed that the contact resistance might be one of the reasons.

• Proceedings of the Materials Research Society of Korea Conference
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• 1995.11a
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• pp.82-82
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• 1995