• Journal of Welding and Joining
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• v.20 no.6
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• pp.783-788
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• 2002

Sn-Ag-Cu solder is known as most competitive in many kinds of Pb-free solders. In this study, effects of solderability with plated layers such as Cu, Cu/Sn, Cu/Ni and Cu/Ni/Au were investigated. Sn-3.5Ag-0.7Cu solder balls were reflowed in commercial reflow machine (peak temp.:$250^{\circ}C$and conveyer speed:0.6m/min). In wetting test, immersion speed was 5mm/sec., immersion time 5sec., immersion depth 4mm and temperature of solder bath was $250^{\circ}C$. Wettability of Sn-3.5Ag-0.7Cu on Cu, Cu/Sn ($5\mu\textrm{m}$), Cu/Ni ($5\mu\textrm{m}$), and Cu/Ni/Au ($5\mu\textrm{m}/500{\AA}$) layers was investigated. Cu/Ni/Au layer had the best wettability as zero cross time and equilibrium force, and the measured values were 0.93 sec and 7mN, respectively. Surface tension of Sn-3.5Ag-0.7Cu solder turmed out to be 0.52N/m. The thickness of IMC is reduced in the order of Cu, Cu/Sn, Cu/Mi and Cu/Ni/Au coated layer. Shear strength of Cu/Ni, Cu/Sn and Cu was around 560gf but Cu/Ni/Au was 370gf.

• Proceedings of the KWS Conference
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• 2007.11a
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• pp.235-237
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• 2007

In this paper, fabrication of Sn-3.0Ag-0.5Cu solder bumping having accurate composition and behavior of intermetallic compounds(IMCs) growth at interface between Sn-Ag-Cu bumps and Cu substrate were studied. The ternary alloy of the Sn-3.0Ag-0.5Cu solder was made by two binary(Sn-Cu, Sn-Ag) electroplating on Cu pad. For the manufacturing of the micro-bumps, photo-lithography and reflow process were carried out. After reflow process, the micro-bumps were aged at $150^{\circ}C$ during 1 hr to 500 hrs to observe behavior of IMCs growth at interface. As a different of Cu contents(0.5 or 2wt%) at Sn-Cu layer, behavior of IMCs was estimated. The interface were observed by FE-SEM and TEM for estimating of their each IMCs volume ratio and crystallographic-structure, respectively. From the results, it was found that the thickness of $Cu_3Sn$ layer formed at Sn-2.0Cu was thinner than the thickness of that layer be formed Sn-0.5Cu. After aging treatment $Cu_3Sn$ was formed at Sn-0.5Cu layer far thinner.

• Journal of Welding and Joining
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• v.25 no.2
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• pp.82-88
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• 2007

Sn-3.0Ag-0.5Cu lead fee solder was generally utilized in electronics assemblies. But it is insufficient to research about activation energy(Q) that is applying to evaluate the solder joint reliability of environmental friendly electronics assemblies. Therefore this study investigated Q values which are needed to IMC formation and growth of Sn-3.0Ag-0.5Cu/Cu and Sn-40pb/Cu solder joints during aging treatment. We bonded Sn-3.0Ag-0.5Cu and Sn-40Pb solders on FR-4 PCB with Cu pad$(t=80{\mu}m)$. After reflow soldering, to observe the IMC formation and growth of the solder joints, test specimens were aged at 70, 150 and $170^{\circ}C$ for 1, 2, 5, 20, 60, 240, 960, 15840, 28800 and 43200 min, respectively. SEM and EDS were utilized to analysis the IMCS. From these results, we measured the total IMC$(Cu_6Sn_5+Cu_3Sn)$ thickness of Sn-3.0Ag-0.5Cu/Cu and Sn-40Pb/Cu interface, and then obtained Q values for the IMC$(Cu_6Sn_5,\;Cu_3Sn)$ growth of the solder joints.

• Korean Journal of Materials Research
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• v.15 no.9
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• pp.598-603
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• 2005

To develope new lead-free solders with the melting temperature close to that of Sn-37Pb$(183^{\circ}C)$, Sn-0.7Cu-5Pb-1Ga, Sn-0.7Cu-5Pb-1Ag, Sn-0.7Cu-5Pb-5Bi-1Ag, and Sn-0.7Cu-SBi-1Ag alloys were composed by adding low-netting elements such as Ga, Bi, Pb, and Ag to Sn-0.7Cu. Then the melting temperatures, microstructures, wettability, and adhesion properties of these alloys were evaluated. DSC analysis showed that the melting temperature of Sn-0.7Cu-SPb-1Ga was $211^{\circ}C$, and those of other alloys was in the range of $192\~200^{\circ}C$. Microstructures of these alloys after heat-treatment at $150^{\circ}C$ for 24 hrs were basically composed of coarsely- grown $\beta-Sn$ grains, and $Cu_6Sn_5$ and $Ag_3Sn$ intermetallic precipitates. Sn-0.7Cu-5Pb-1Ga and Sn-0.7Cu-5Pb-5Bi-1Ag showed excellent wettability, while Sn-0.7Cu-5Bi-1Ag and Sn-0.7Cu-5Pb-5Bi-1Ag revealed good adhesion strength with the Cu substrates. Among 4 alloys, Sn-0.7Cu-5Pb-5Bi-1Ag with the lowest melting temperature $(192^{\circ}C)$ and relatively excellent wettability and adhesion strength was suggested to be the best candidate solder to replace Sn-37Pb.

• Journal of the Microelectronics and Packaging Society
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• v.9 no.2
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• pp.1-9
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• 2002

The intermetallic formation between Sn-Ag-(Cu) solders and metal pads in a real BGA package was characterized using SEM, EDS, and XRD. The intermetallic phase formed in the interface between Sn-Ag-Cu and Au/Ni/Cu pad is likely to be ternary compound of $(Cu,Ni)_6Sn_5$ from EDS analysis High concentration of Cu was observed in the solder/Ni interface. XRD analysis confirmed that $\eta -Cu_6 Sn_5$ type was intermetallic phase formed in the interface between Cu containing solders and Ni substrates and $Ni_3$Sn_4$ intermetallic was formed in the Sn-Ag solder/Ni interface. The thickness of intermetallic phase increased with the reflow times and Cu concentration in solder.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.18 no.1
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• pp.33-37
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• 2008

The effects of Cu and Sb on the microstructure and mechanical properties of Sn-Sb-Cu-Ni-Cd whitemetal were investigated. Any compound phase was not observed in the whitemetal with 0.05 wt% Cu, while as the Cu content was increased, star- or needle-like $Cu_6Sn_5$ phases were found. The tensile strength gradually increased with Cu up to 5 % and then remained almost constant with Cu content above 5 %, while the hardness continuously increased with Cu content because of the increased hard $Cu_6Sn_5$ phases. As the Sb content increased, SbSn cuboids were present as well as $Cu_6Sn_5$. The tensile steength and hardness continuously increased and the elongation decreased with Sb content.

• Journal of Welding and Joining
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• v.20 no.1
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• pp.97-102
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• 2002

The growth kinetics of intermetallic compound layers formed between the eutectic Sn-3.5Ag solder and the Cu and Ni/Cu pad by solid stateisothermal aging were examined. The interfacial reaction between the eutectic Sn-3.5Ag solder and the Cu and Ni/Cu pad was investigated at 70, 120, 150, $170^{\circ}C$ for various times. The intermetallic compound layer was composed of two phase: $Cu_6Sn_5$(${\varepsilon}-phase$) adjacent to the solder and $Cu_6Sn_5$(${\varepsilon}-phase$) adjacent to the copper and on solder/Ni pad the intermetallic compound layer was $Ni_3Sn_4$. Because the values of time exponent(n) have approximately 0.5, the layer growth of the intermetallic compound was mainly controlled by volume diffusion over the temperature range studied. The apparent activation energy for layer growth of total Cu-Sn($Cu_6Sn_5 + Cu_6Sn$), $Cu_6Sn_5$, $Cu_3Sn$ and $Ni_3Sn_4$ intermetallic compound were 64.82kJ/mol, 48.53kJ/mol, 89.06kJ/mol and 71.08kJ/mol, respectively.

• Proceedings of the International Microelectronics And Packaging Society Conference
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• 2003.11a
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• pp.133-137
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• 2003

The effect of Bi additions to the eutectic Sn-3.5Ag solder alloy on the growth kinetics of the intermetallic compound (IMC) layers during solid-state aging of Sn-Ag-Bi/Cu solder joints has been Investigated. The Bi additions enhanced the growth rate of the total IMC layer comprising of $Cu_6Sn_5$ and $Cu_3Sn$ sublayers. This enhanced IMC growth rate was primarily due to the rapid increase In the growth rate of $Cu_6Sn_5$ sublayer. The growth rate of $Cu_3Sn$ sublayers was little influenced and appeared to be retarded by the Bi additions. The observed growth behavior of $Cu_6Sn_5$ and $Cu_3Sn$ sublayers could be understood if the interfacial reaction barrier at the $Cu_6Sn_5/solder$ interface were reduced by the segregation of Bi at the interface.

• Proceedings of the Korean Vacuum Society Conference
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• 2016.02a
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• pp.272.2-272.2
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• 2016

Copper-Tin (CuSn) thin films were synthsized by rf magnetron co-sputtering method with pure Cu and Sn metal targets with various rf powers and sputtering times. The obtained CuSn thin films were characterized by a surface profiler (alpha step), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), X-ray induced Auger electron spectroscopy (XAES), and contact angle measurement. The deposition rates were calculated by the thickness of CuSn thin films and sputtering times. We observed hexagonal Cu20Sn6 and cubic Cu39Sn11 phases from the films by XRD measurement. From the survey XPS spectra, the Cu and Sn main peaks were observed. Therefore, we could conclude CuSn thin films were successfully fabricated on the substrate in this study. The changes of oxidation states and chemical environment of the films were investigated with high resolution XPS spectra in the regions of Cu 2p, Cu LMM, and Sn 3d. Surface free energy (SFE) and wettability of the CuSn thin films were studied with distilled water (DW) and ethylene glycol (EG) using the contact angle measurement. The total SFE of CuSn thin films decreased as rf power on Cu target increased. The contribution to the total SFE of dispersive SFE was relatively superior to polar SFE.

• Journal of the Microelectronics and Packaging Society
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• v.9 no.2
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• pp.39-43
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• 2002

The eutectic solder Sn-37Pb and the lead free solder alloys with the compositions of Sn-0.7Cu, Sn-3.5Ag, Sn-3.5Ag-0.75Cu, Sn-2.0Ag-0.7Cu-3.0Bi were applied to the 48 BGA packages, and then it was discussed for the shear strength at the solder joints as the hardness and the composition of the small solder ball. As a result of experiments, the high degree of hardness with the displacement of 0.043 mm was obtained in Sn-2.0Ag-0.7Cu-3.0Bi. The shear strength of the lead free solder was higher than that of Sn-37Pb solder, and it can be obtained the maximum value of about 52% in Sn-2.0Ag-0.7Cu-3.0Bi.