• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.22 no.3
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• pp.199-204
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• 2009

The effect of temperature on ACF thermocompression bonding for FPD assembly was investigated, It was found that Au bumps on driver IC's were not bonded to the glass substrate when the bonding temperature was below $140^{\circ}C$ so bonds were made at temperatures of $163^{\circ}C$, $178^{\circ}C$ and $199^{\circ}C$ for further testing. The bonding time and pressure were constant to 3 sec and 3.038 MPa. To test bond reliability, FPD assemblies were subjected to thermal shock storage tests ($-30^{\circ}C$, $1\;Hr\;{\leftrightarrow}80^{\circ}C$, 1 Hr, 10 Cycles) and func! tionality was verified by driver testing. It was found all of FPDs were functional after the thermal cycling. Additionally, Au bumps were bonded using ACF's with higher conductive particle densities at bonding temperatures above $163^{\circ}C$. From the experimental results, when the bonding temperature was increased from $163^{\circ}C$ to $199^{\circ}C$, the curing time could be reduced and more conductive particles were retained at the bonding interface between the Au bump and glass substrate.

• 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 the Microelectronics and Packaging Society
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• v.15 no.4
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• pp.1-7
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• 2008

We studied a growth behavior of Intermetallic compounds(IMCs) during solder bumping with two reflow methods. Ti(50 nm), Cu($1{\mu}m$), Au(50 nm) and Ti(50 nm) thin films were deposited on $SiO_2$/Si wafer using the DC magnetron sputtering system as the under bump metallization(UBM). And the $5{\mu}m$ thick Cu bumps and $20{\mu}m$ thick Sn bumps were fabricated on UBM by electroplating. Sn bumps were reflowed in RTA(Rapid Thermal Annealing) system and convection reflow oven. When RTA system was used, reflow was possible without using flux and IMC thickness formed in the solder interface was thinner than that of a convectional method.

• Korean Journal of Materials Research
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• v.10 no.12
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• pp.799-806
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• 2000

Cu$_{6}$Sn$_{5}$-dispersed 63Sn-37Pb solder bumps of 760$\mu\textrm{m}$ size were fabricated on Au(0.5$\mu\textrm{m}$)/Ni(5$\mu\textrm{m}$)/Cu(27$\pm$20$\mu\textrm{m}$) BGA substrates by screen printing process, and their shear strength were characterized with variations of dwell time at reflow peak temperature and aging time at 15$0^{\circ}C$ . With dwell time of 30 seconds at reflow peak temperature, the solder bumps with Cu$_{6}$Sn$_{5}$ dispersion exhibited higher shear strength than the value of the 63Sn-37Pb solder bump. With increasing the dwell time longer than 60 seconds, however the shear strength of the Cu$_{6}$Sn$_{5}$-dispersed solder bumps became lower than that the 63Sn-37Pb solder bumps. The failure surface of the solder bumps could be divided into two legions of slow crack propagation and critical crack propagation. The shear strength of the solder bumps was inversely proportional to the slow crack propagation length, regardless of the dwell time at peak temperature, aging time at 150 $^{\circ}C$ and the volume fraction of Cu$_{6}$Sn$_{5}$ dispersion.> 5/ dispersion.

• Journal of the Korean institute of surface engineering
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• v.36 no.5
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• pp.386-392
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• 2003

The electroplating process for a solder bump which can be applied for a flip chip was studied. Si-wafer was used for an experimental substrate, and the substrate were coated with UBM (Under Bump Metallization) of Al(400 nm)/Cu(300 nm)Ni(400 nm)/Au(20 nm) subsequently. The compositions of the bump were Sn-Cu and eutectic Sn-Pb, and characteristics of two bumps were compared. Experimental results showed that the electroplated thickness of the solders were increased with time, and the increasing rates were TEX>$0.45 <\mu\textrm{m}$/min for the Sn-Cu and $ 0.35\mu\textrm{m}$/min for the Sn-Pb. In the case of Sn-Cu, electroplating rate increased from 0.25 to $2.7\mu\textrm{m}$/min with increasing current density from 1 to 8.5 $A/dm^2$. In the case of Sn-Pb the rate increased until the current density became $4 A/dm^2$, and after that current density the rate maintains constant value of $0.62\mu\textrm{m}$/min. The electro plated bumps were air reflowed to form spherical bumps, and their bonded shear strengths were evaluated. The shear strength reached at the reflow time of 10 sec, and the strength was of 113 gf for Sn-Cu and 120 gf for Sn-Pb.

• Journal of the Microelectronics and Packaging Society
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• v.22 no.3
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• pp.39-44
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• 2015

We investigated the effect of CNT-Ag composite pad on the contact resistance of flip-chip joints, which were formed by flip-chip bonding of Cu/Au chip bumps to Cu substrate metallization using anisotropic conductive adhesive. Lower contact resistances were obtained for the flip-chip joints which contained the CNT-Ag composite pad than the joints without the CNT-Ag composite pad. While the flip-chip joints with the CNT-Ag composite pad exhibited average contact resistances of $164m{\Omega}$, $141m{\Omega}$, and $132m{\Omega}$ at bonding pressures of 25 MPa, 50 MPa, and 100 MPa, the flip-chip joints without the CNT-Ag composite pad had an average contact resistance of $200m{\Omega}$, $150m{\Omega}$, and $140m{\Omega}$ at each bonding pressure.

• 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.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.10 no.2
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• pp.61-67
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• 2003

The interfacial reaction between ultra-small 58Bi-42Sn solder and Au/Ni/Ti under bump metallurgy (UBM) for ultra-fine flip chip application was investigated. The ultra-small 58Bi-42Sn solder bump, about $46{\mu}m$ in diameter, was fabricated by using the lift-off method and reflowed using the rapid thermal annealing (RTA) system. The intermetallic compounds were characterized using a secondary electron microscopy (SEM), an energy dispersive spectroscopy (EDS), and an x-ray diffractometer (XRD). The faceted and polygonal intermetallic compounds were found in the Bi-Sn solder bumps on $Au(0.1{\mu}m)/Ni/Ti$ UBM and they were indentified as $(Au_xBi_yNi_{1-x-y})Sn_2$ Phase. The intermetallic compounds grown from the $Au(0.1{\mu}m)/Ni/Ti$ UBMinterface were dispersed in the solder bump.

• Korean Journal of Metals and Materials
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• v.49 no.5
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• pp.411-418
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• 2011

The current study investigates the electroplating characteristics of Sn-Cu eutectic micro-bumps electroplated on a Si chip for flip chip application. Under bump metallization (UBM) layers consisting of Cr, Cu, Ni and Au sequentially from bottom to top with the aim of achieving Sn-Cu bumps $10\times10\times6$ ${\mu}m$ in size, with 20${\mu}m$ pitch. In order to determine optimal plating parameters, the polarization curve, current density and plating time were analyzed. Experimental results showed the equilibrium potential from the Sn-Cu polarization curve is -0.465 V, which is attained when Sn-Cu electro-deposition occurred. The thickness of the electroplated bumps increased with rising current density and plating time up to 20 mA/$cm^2$ and 30 min respectively. The near eutectic composition of the Sn-0.72wt%Cu bump was obtained by plating at 10 mA/$cm^2$ for 20 min, and the bump size at these conditions was $10\times10\times6$ ${\mu}m$. The shear strength of the eutectic Sn-Cu bump was 9.0 gf when the shearing tip height was 50% of the bump height.