• 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.20 no.3
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• pp.45-51
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• 2013

Thermal annealing tests were performed in an in-situ scanning electron microscope chamber at $130^{\circ}C$, $150^{\circ}C$, and $170^{\circ}C$ in order to investigate the effects of solder structure on the growth kinetics of intermetallic compound (IMC) in Cu/Sn-3.5Ag microbump. Cu/Sn-3.5Ag($6{\mu}m$) microbump with spreading solder structure showed $Cu_6Sn_5$ and $Cu_3Sn$ phase growths and then IMC phase transition stages with increasing annealing time. By the way, Cu/Sn-3.5Ag($4{\mu}m$) microbump without solder spreading, remaining solder was transformed to $Cu_6Sn_5$ right after bonding and had only a phase transition of $Cu_6Sn_5$ to $Cu_3Sn$ during annealing. Measured activation energies for the growth of the $Cu_3Sn$ phase during the annealing were 0.80 and 0.71eV for Cu/Sn-3.5Ag($6{\mu}m$) and Cu/Sn-3.5Ag($4{\mu}m$), respectively.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2000.07a
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• pp.658-662
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• 2000

The microstructure, adhesion strength and conductivity of electroplated Sn-Cu Films on Alloy42 lead Frame were measured for comparison. In the case of electroplated 90Sn10Cu, 99Sn1Cu, Cu$\sub$10/Sn$_3$Phase was formed and Ni$_3$Sn$_2$Phase was formed after 200$^{\circ}C$, 30min annealing. In the case of electroplated 99Sn1Cu, Cu$\sub$10/Sn, Ni$_3$Sn phases were formed and Ni$_3$Sn$_4$, Ni$_3$Sn$_4$phases were formed after 200$^{\circ}C$, 30min annealing. 90Sn10Cu film was measured better uniformity, adhesion strength and conductivity than 99Sn1Cu.

• Journal of the Microelectronics and Packaging Society
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• v.15 no.1
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• pp.33-37
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• 2008

A noticeable amount of Kirkendall voids formed at the Sn-3.5Ag solder joint with electroplated Cu, and that became even more significant when an additive was added to Cu electroplating bath. With SPS, a large amount of voids formed at the $Cu/Cu_3Sn$ interface of the solder joint during thermal aging at $150^{\circ}C$. The in-situ AES analysis of fractured joints revealed S segregation on the void surface. Only Cu, Sn, and S peaks were detected at the fractured $Cu/Cu_3Sn$ interfaces, and the S peak decreased rapidly with AES depth profiling. The segregation of S at the $Cu/Cu_3Sn$ interface lowered interface energy and thereby reduced the free energy barrier for the Kirkendall void nucleation. The drop impact test revealed that the electrodeposited Cu film with SPS degraded drastically with aging time. Fracture occurred at the $Cu/Cu_3Sn$ interface where a lot of voids existed. Therefore, voids occupied at the $Cu/Cu_3Sn$ interface are shown to seriously degrade drop reliability of solder joints.

• Journal of the Microelectronics and Packaging Society
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• v.14 no.4
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• pp.15-20
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• 2007

Growth kinetics of intermetallic compound (IMC) at various interface in Cu pillar bump during aging have been studied by thermal aging at 120, 150 and $165^{\circ}C$ for 300h. In result, $Cu_6Sn_5\;and\;Cu_3Sn$ were observed in the Cu pillar/SnPb interface and IMC growth followed parabolic law with increasing aging temperatures and time. Also, growth kinetics of IMC layer was faster for higher aging temperature with time. Kirkendall void formed at interface between Cu pillar and $Cu_3Sn$ as well as within the $Cu_3Sn$ layer and propagated with increasing time. $(Cu,Ni)_6Sn_5$ formed at interface between SnPb and Ni(P) after reflow and thickness change of $(Cu,Ni)_6Sn_5$ didn't observe with aging time. The apparent activation energies for growth of total $(Cu_6Sn_5+Cu_3Sn),\;Cu_6Sn_5\;and\;Cu_3Sn$ intermetallics from measurement of the IMC thickness with thermal aging temperature and time were 1.53, 1.84 and 0.81 eV, respectively.

• Journal of the Microelectronics and Packaging Society
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• v.19 no.2
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• pp.35-39
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• 2012

We studied interfacial reaction and bonding characteristics of a flip chip bonding with the viewpoint of formation behavior of intermetallic compounds. For this purpose, Sn-0.7Cu and Sn-3Cu solders were reflowed on the Al/Cu and Al/Ni UBMs. When Sn-0.7Cu was reflowed on the Al/Cu UBM, no intermetallic compounds were formed at the solder/UBM interface. The $Cu_6Sn_5$ intermetallic compounds formed by reflowing Sn-3Cu solder on the Al/Cu UBM were spalled from the interface, resulting in delamination of the solder/UBM interface. On the other hand, the $(Cu,Ni)_6Sn_5$ intermetallic compounds were formed by reflowing of Sn-0.7Cu and Sn-3Cu on the Al/Ni UBM and the interfacial bonding between the Sn-Cu solders and the Al/Ni UBM was kept stable.

• 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.

• 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.

• 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.

• Journal of Welding and Joining
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• v.20 no.6
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• pp.59-59
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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℃ 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℃. Wettability of Sn-3.5Ag-0.7Cu on Cu, Cu/Sn (5㎛), Cu/Ni (5㎛), and Cu/Ni/Au (5㎛/500Å) 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.