• Journal of the Microelectronics and Packaging Society
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• v.19 no.1
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• pp.67-73
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• 2012

After flash memory card(FMC) was manufactured by $B^2it$ process, interfacial reaction of silver bump with thermal stress was studied. To investigate bonding reliability of Ag bump, thermal shock and thermal stress tests were conducted and then examined on the crack between Cu land and Ag bump interface. Diffusion reaction of Ag bump/Cu land interface was analyzed using SEM, EDS and FIB. The Ag-Cu alloy layer due to the interfacial reaction was formed at the Ag/Cu interface. As the diffusivity of Ag ${\rightarrow}$ Cu is faster than Cu ${\rightarrow}$ Ag, a lot of (Cu, Ag) alloy layers were observed at the Cu layer than Ag. These alloy layers contributed to increase the Cu-Ag bonding strength and its reliability.

• Proceedings of the International Microelectronics And Packaging Society Conference
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• 2003.11a
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• pp.114-117
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• 2003

본 연구에서는 계산을 통해 나온 Sn-Ag-Cu 삼원계 공정점(Sn-3.7Ag-0.9Cu)을 바탕으로 그 근처의 응고경로가 다른 6가지 조성(Sn-4.6Ag-0.4Cu, Sn-4.9Ag-1.0Cu, Sn-3.9Ag-1.3Cu, Sn-2.2Ag-1.2Cu, Sn-2Ag-0.7Cu, Sn-2.7Ag-0.3Cu)에 대한 솔더합금의 미세조직을 관찰하였다. 응고경로는 $L\;\rightarrow\;L+Primary\;\rightarrow\;L+Primary+Secondary\;\rightarrow\;Ternary\;Eutectic+Primary+Secondary$로 되며 6가지 경우를 예상할 수 있다 솔더합금의 미세조직은 느린 냉각으로 인하여 빠른 냉각, 보통 냉각에 비해 상대적으로 커다란 $\beta-Sn$ dendrite를 보였고 $Ag_3Sn,\;Cu_6Sn_5$과는 다르게 $\beta-Sn$는 약 $30^{\circ}C$의 과냉(DSC분석)이 존재하게 되어 Sn-4.6Ag-0.4Cu의 경우에는 $Ag_3Sn$상이, Sn-2.2Ag-1.2Cu의 경우에는 $Cu_6Sn_5$가 과대성장을 하였다. 솔더의 기계적 특성을 살펴보고자 Cu 기판위에서 각 조성의 솔더볼을 솔더링한 후 다양한 냉각 속도를 적용하여 reflow 솔더링을 하고 솔더/기판 접합에 대한 전단 강도 시험을 실시했다. 냉각 속도가 빠를수록 $\beta-Sn$의 dendrite가 미세해져서 높은 전단 강도를 보였고 6가지 조성의 솔더볼중 공정조직 분율이 낮은 Sn-2Ag-0.7Cu 조성의 경우에서 낮은 전단 강도가 나타났다.

• Journal of the Microelectronics and Packaging Society
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• v.21 no.2
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• pp.91-97
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• 2014

With Pb-free solder joints containing Sn-Ag-Cu-based ternary alloys (Sn-1.0 wt.%Ag-0.5Cu and Sn-4.0Ag-0.5Cu) and Sn-Ag-Cu-In-based quaternary alloys (Sn-1.0Ag-0.5Cu-1.0In, Sn-1.2Ag-0.5Cu-0.4In, Sn-1.2Ag-0.5Cu-0.6In, and Sn-1.2Ag-0.7Cu-0.4In), fracture-mode change, shear strengths, and fracture energies were observed and measured under a high-speed shear test of 500 mm/s. The samples in each composition were prepared with as-reflowed ones or solid-aged ones at $125^{\circ}C$ to 500 h. As a result, it was observed that ductile or quasi-ductile fracture modes occurs in the most of Sn-Ag-Cu-In samples. The happening frequency of a quasi-ductile fracture mode showed that the Sn-Ag-Cu-In joints possessed ductile fracture properties more than that of Sn-3.0Ag-0.5Cu in the high-speed shear condition. Moreover, the Sn-Ag-Cu-In joints presented averagely fracture energies similar to those of Sn-Ag-Cu joints. While maximum values in the fracture energies were measured after the solid aging for 100 h, clear decreases in the fracture energies were observed after the solid aging for 500 h. This result indicated that reliability degradation of the Sn-Ag-Cu-In solder joints might accelerate from about that time.

• Journal of the Korean Ceramic Society
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• v.35 no.1
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• pp.55-65
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• 1998

The oxidation behavior of Ag-36.8a%Cu-7.4at%Ti alloy brazed on Si3N4 substrate was investigated at 400, 500 and 600$^{\circ}C$ in air. Under this experimental condition Si3N4 and Ag were not oxidized whereas Cu and Ti among the brazing alloy components were oxidizied obeying the parabolic oxidation rate law. The activation energy of oxidation was found to be 80kj/ mol which was smaller than that of pure Cu owing to the presence of oxygen active element of Ti. The outer oxide scale formed from the initial oxidation state was always composed of Cu oxides which were known to be growing by the outward diffusion of Cu ions. As the oxidation progressed the concentration gradient occurred due to the continuous consumption of Cu as Cu oxides and consequently build-up of an Ag-enriched layer below the Cu oxides resulted in the formation of multiple oxide scales composed of Cu oxide (CuO) /Ag-enriched layer/Cu oxide (Cu2O) /Ag-enriched layer. Also the inward diffusing of oxygen through Cu oxide and Ag-enriched layers led to the formation of internal oxides of TiO2.

• Proceedings of the KWS Conference
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• 2006.10a
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• pp.169-171
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• 2006

Solderability and reaction properties were investigated for four Pb-free alloys as a function of Ag contents; Sn-4.0Ag-0.5Cu, Sn-3.0Ag-0.5Cu, Sn-2.5Ag-0.5Cu, and Sn-1.0Ag-0.5Cu. The alloy of the lowest Ag content, i.e., Sn-1.0Ag-0.5Cu, showed poor wetting properties as the reaction temperature decreased to 230oC. Variation of Ag concentration in the Sn-xAg-0.5Cu alloy shifted exothermic peaks indicating the undercooling temperature in DSC curve. For the aging process at 170oC, the thickness of IMCs at the board-side solder/Cu interface increased with the Ag concentration.

• Korean Journal of Environmental Biology
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• v.20 no.2
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• pp.136-145
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• 2002

A laboratory microcosm experiment was conducted to evaluate a major metal uptake route as well as chronic toxic effects of the clam, Macoma balthica exposed to Ag and Cu contaminated sediments. Twenty five clams were exposed to the sediments contaminated with four levels of Ag $Ag(0.01-0.87\mu{mol}\;g^{-1})$ and $Cu(0.75-5.55\mu{mol\;g^{-1})$ for 90 days. AVS (acid volatile sulfide) concentration in the sediments, considered as major factor controlling metal geochemistry and bioavailability, was manipulated to evaluate its effects on Ag and Cu bioaccumulation in M. balthica. Following 90-d exposure, the tissue Ag and Cu in M. balthica increased linearly with the Ag and Cu concentrations in sediments extracted with 1 N HCI (SEM, simultaneously extracted metals with AVS). The bioaccumulation of Ag and Cu in M. balthica was little influenced by difference in [SEM] - [AVS] values, suggesting a minor contribution of pore water metals to bioaccumulation. Tissue Ag and Cu concentrations directly influenced on the clearance rate and glycogen content of the clams. The clams with highest tissue Ag $(1.0\pm{0.2}\mu{mol}\;g^{-1})$ and Cu concentrations $(2.7\pm{0.3}\;\mu{mol}\;g^{-1})$ had only 18-43% of clearance of the clams exposed to uncontaminated sediments. Similarly, glycogen content of the exposed clams had a inverse relationship with tissue Ag and Cu concentrations. These results suggest that M. balthica exposed to Ag and Cu contaminated sediments accumulates metals largely by ingestion of contaminated sediments and can display chronic effects as reduced clearance rate and glycogen content.

• Proceedings of the KWS Conference
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• 2006.05a
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• pp.33-35
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• 2006

The interactions between Cu/Sn-Ag-(Cu) and Sn-Ag-(Cu)/Ni interfacial reactions were studied during isothermal aging at $150^{\circ}C$ for up to 1000h using Cu(ENIG)/Sn-3.5Ag-(0.7Cu)/Cu(ENIG) sandwich solder joints. A typical scallop-type Cu-Sn intermetallic compound (IMC) layer formed at the upper Sn-Ag/Cu interface after reflowing, whereas a $(Cu,Ni)_6Sn_5$ IMC layer was observed at the Sn-Ag/ENIG interface. The Cu in the $(Cu,Ni)_6Sn_5$ IMC layer formed on the Ni side was sourced from the dissolution of the opposite Cu metal pad or Cu-Sn IMC layer. When the dissolved Cu arrived at the interface of the Ni pad, the $(Cu,Ni)_6Sn_5$ IMC layer formed on the Ni interface, preventing the Ni pad from reacting with the solder. Although a long isothermal aging treatment was performed at $150^{\circ}C$, no Ni was detected in the Cu-Sn IMC layer formed on the Cu side. Compared to the single Sn-Ag/ENIG solder joint, the formation of the $(Cu,Ni)_6Sn_5$ IMC layer of the Cu/sn-Ag/ENIG sandwich joint effectively retarded the Ni consumption from the electroless Ni-P layer.

• Journal of Powder Materials
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• v.14 no.5
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• pp.320-326
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• 2007

Ag-Cu alloy nano powders were fabricated by the electrical explosion of Cu-plated Ag wires. Ag wires of 0.2mm diameter was electroplated to final diameter of 0.220 mm and 0.307 mm which correspond to Ag-27Cu and Ag-68Cu alloy. The explosion product consisted of equilibrium phases of ${\alpha}-Ag$ and ${\beta}$-Cu. The particle size of Ag-Cu nano powders were 44 nm and 70 nm for 0.220 mm and 0.307 mm wires, respectively. The Ag-Cu nano powders contained less Cu than average value due to higher sublimation energy compared to that of Ag. As a result, micron-sized spherical particles formed from liquid droplets contained higher Cu content.

• Journal of the Microelectronics and Packaging Society
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• v.28 no.2
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• pp.59-64
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• 2021

System-in-package (SIP) technology using heterogeneous integration is becoming the key of next-generation semiconductor packaging technology, and the development of low temperature Cu bonding is very important for high-performance and fine-pitch SIP interconnects. In this study the low temperature Cu bonding and the anti-oxidation effect of copper using porous Ag nanolayer were investigated. It has been found that Cu diffuses into Ag faster than Ag diffuses into Cu at the temperatures from 100℃ to 200℃, indicating that solid state diffusion bonding of copper is possible at low temperatures. Cu bonding using Ag nanolayer was carried out at 200℃, and the shear strength after bonding was measured to be 23.27 MPa.

• Proceedings of the International Microelectronics And Packaging Society Conference
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• 2003.11a
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• pp.110-113
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• 2003

여러가지 Sn-Ag-Cu 솔더조성과 솔더링 후의 냉각속도에 따라 솔더링 접합부에서의 계면 미세조직의 다양한 변화를 관찰해 보았다. 현재까지 Sn-Ag-Cu 3원계 공정점에 대한 정확한 연구가 미흡하고, 상용으로 제품화되고 있는 Sn-Ag-Cu 합금계는 3원계 공정조성에서 약간 벗어난 조성들을 선택하고 있다고 할 수 있다. 따라서, 본 연구에서 사용한 Sn-Ag-Cu 합금 조성은 Sn-3.5Ag, Sn-3Ag-0.7Cu, Sn-3Ag-1.5Cu, Sn-3.7Ag-0.9Cu, Sn-6Ag-0.5Cu로 선택하였으며, 각 조성에서 Lap Shear Joint를 제조하였다. 사용한 Solder pad는 Cu pad와 Cu pad 위에 Au/Ni를 plating한 것을 이용하였다. 리플로우 솔더링 조건은 $250^{\circ}C$ 이상의 온도에서 60초 실시하였으며, 리플로우 솔더링 후의 냉각속도를 달리하여 냉각시켰다. 솔더링 후의 냉각속도가 느려질수록 계면 금속간화합물(IMC)의 두께가 더욱 증가하며, 조대화되었다. 또한 솔더 조성의 영향에서 Cu와 Ag의 함량이 높을수록 계면 IMC의 두께가 증가되었으며, 이는 솔더내부에 형성된 IMC 입자들이 조대화되어 계면 IMC층에 결합되어 나타났기 때문이다.