• Proceedings of the KWS Conference
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• 2002.05a
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• pp.276-277
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• 2002

• Proceedings of the International Microelectronics And Packaging Society Conference
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• 2002.05a
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• pp.98-103
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• 2002

BGA(Ball Grid Array) 패키지의 솔더볼 패드 중의 하나인 Au/Ni-Co/Cu 금속층 위에 Bi가 첨가된 Sn-3.5Ag-$\chi$Bi 솔더볼을 리플로우시켰다. 리플로우한 후 130 $^{\circ}C$에서 열처리함에 따른 계면상 및 솔더 내부의 상변화를 관찰하였다. 계면에는 (Ni,Co)$_3$Sn$_4$외에 (Au,Ni,Co,Bi)Sn$_4$가 생성되었음을 관찰할 수 있었고, 솔더 내부에는 (Au,Ni,Co,Bi)SH$_4$, Ag$_3$Sn, Bi 상이 혼재되어 있었다. Nano-indentation에 의한 경도 측정 결과, Bi 함량 증가에 따라 경도는 증가하였으나, 볼전단(Ball Shear) 테스트 결과는 Bi가 증가됨에 따라 오히려 볼전단 강도값이 감소하였다. 이는 파면 검사 결과, 파괴 경로가 주로 계면의 금속간 화합물과 솔더 사이에서 진행함에 기인한 것이다. 솔더 내부의 파괴 경로를 가진 2.5Bi가 가장 우수한 볼전단 강도값을 나타내었는데, 이는 솔더내의 Bi의 고용강화에 기인한 것으로 보인다.

• Journal of the Microelectronics and Packaging Society
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• v.12 no.2 s.35
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• pp.121-128
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• 2005

Solder joints in microelectronic devices are frequently operated at an elevated temperature in service. They also experience plastic deformation caused by temperature excursion and difference in thermal expansion coefficients. Deformed solders can go through a recovery and recrystallization process at an elevated temperature, which would alter their microstructure and mechanical properties. In this study, to predict the changes in mechanical properties of Pb-free solder joints at high temperatures, the high temperature microhardness of several Pb-free and composite solders was measured as a function of temperature, deformation, and annealing condition. Solder alleys investigated include pure Sn, Sn-0.7Cu, Sn-3.5Ag, Sn-3.8Ag-0.7Cu, Sn-2.8Ag-7.0Cu (composite), and Sn-2.7Ag-4.9Cu-2.9Ni (composite). Numbers are all in wt.$\%$ unless specified otherwise. Solder pellets were cast at two cooling rates (0.4 and $7^{\circ}C$/s). The pellets were compressively deformed by $30\%$ and $50\%$ and annealed at $150^{\circ}C$ for 2 days. The microhardness was measured as a function of indentation temperature from 25 to $130^{\circ}C$. Their microstructure was also evaluated to correlate with the changes in microhardness.

• Journal of the Microelectronics and Packaging Society
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• v.20 no.2
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• pp.59-64
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• 2013

In-situ annealing tests of Cu/Ni/Au/Sn-Ag/Cu micro-bump for 3D IC package were performed in an scanning electron microscope chamber at $135-170^{\circ}C$ in order to investigate the growth kinetics of intermetallic compound (IMC). The IMC growth behaviors of both $Cu_3Sn$ and $(Cu,Ni,Au)_6Sn_5$ follow linear relationship with the square root of the annealing time, which could be understood by the dominant diffusion mechanism. Two IMC phases with slightly different compositions, that is, $(Cu,Au^a)_6Sn_5$ and $(Cu,Au^b)_6Sn_5$ formed at Cu/solder interface after bonding and grew with increased annealing time. By the way, $Cu_3Sn$ and $(Cu,Au^b)_6Sn_5$ phases formed at the interfaces between $(Cu,Ni,Au)_6Sn_5$ and Ni/Sn, respectively, and both grew with increased annealing time. The activation energies for $Cu_3Sn$ and $(Cu,Ni,Au)_6Sn_5$ IMC growths during annealing were 0.69 and 0.84 eV, respectively, where Ni layer seems to serve as diffusion barrier for extensive Cu-Sn IMC formation which is expected to contribute to the improvement of electrical reliability of micro-bump.

• 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.

• Journal of the Microelectronics and Packaging Society
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• v.14 no.3
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• pp.43-49
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• 2007

Thickness of intermetallic compounds and consumption rates of under bump metallurgies (UBMs) were investigated in wafer-level solder bumping with variations of UBM materials and reflow times. In the case of Cu UBM, $0.6\;{\mu}m-thick$ intermetallic compound layer was formed before reflow of Sn solder, and the average thickness of the intermetallic compound layer increased to $4\;{\mu}m$ by reflowing at $250^{\circ}C$ for 450 sec. On the contrary, the intermetallic layer had a thickness of $0.2\;{\mu}m$ on Ni UBM before reflow and it grew to $1.7\;{\mu}m$ thickness with reflowing for 450 sec. While the consumption rates of Cu UBM were 100nm/sec fur 15-sec reflow and 4.50-sec for 450-sec reflow, those of Ni UBM decreased to 28.7 nm/sec for 15-sec reflow and 1.82 nm/sec for 450-sec reflow.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.20 no.2
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• pp.187-192
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• 2011

UBM(Under Bump Metallurgy) is very important for successful realization of Flip-Chip technology. In this study, it is investigated the interfacial reactions between various Sn-Ag solder alloys and Ni-P/Au UBM and Cu plate finish. It is also evaluated the shear strength by using the micro shear-punch test method for Sn-37Pb alloy, binary and ternary alloys of environment-friendly Pb-free solder alloys which are applied in the electronic packages. In terms of interfacial microstructure, the Pb-free solder joints have thicker IMCs than the Sn-Pb solder joints. The thickness of IMC is related to Reflow time. The IMC has been observed to grow with the increase in Reflow time. As a result of the shear test, in case of Max. shear strength, Pb-free solder showed the highest strength value and Sn-37Pb showed the lowest strength value 10 be generally condition of Reflow time.

• Proceedings of the International Microelectronics And Packaging Society Conference
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• 2003.11a
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• pp.94-98
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• 2003

The microstructure of Sn1.8Bi0.8Cu0.6In alloys was evaluated at various aging time. The bumps of Sn1.8Bi0.8Cu0.6In alloys after reflowed at $250^{\circ}C$ were well-formed and had 260um height. The craters on the bumps, however, were observed. Intermetallic compounds formed on the interface between so]der and Cu/Ni UBM were consist of $(Cu,Ni)_6Sn_5$. As aging goes on up to 1000hours, the composition of Ni changed from $6.63\%$ at initial stage(as-reflowed) to $13.47\%$ at final stage(1000hours aging ). In addition, after 500hours aging, the floating of IMC to the solder was observed.

• Journal of the Microelectronics and Packaging Society
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• v.22 no.3
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• pp.51-56
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• 2015

It has been used various pad finish materials to enhance the reliability of solder joint and recently Electroless Ni Electroless Pd Immersion Gold (the following : ENEPIG) pad has been used more than others. This study is about reliability according to being used in commercial Electrolytic Ni pad and ENEPIG pad, and was observed behavior of various Cu contents. After reflow, the inter-metallic compound (IMC) between solder and pad is composed of $Cu_6Sn_5$ (Ni substituted) by using EDS, and in case of ENEPIG, between IMC and Ni layer was observed the dark layer ($Ni_3P$ layer). Additional, it could be controlled the thickness of dark layer according to Cu contents. Investigated the different fracture mode between electrolytic Ni and ENEPIG pad after drop shock test, in case of soft Ni, accelerated stress propagated along the interface between $1^{st}$ IMC and $2^{nd}$ IMC, and in case of ENEPIG pad, accelerated stress propagated along the weaken surface such as dark layer. The unstable interface exists through IMC, pad material and solder bulk by the lattice mismatch, so that the thermal and physical stress due to the continuous exterior impact is transferred to the IMC interface. Therefore, it is strongly requested to control solder morphology, IMC shape and thickness to improve the solder reliability.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.39 no.5
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• pp.467-471
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• 2015

Thus far, solders used in electronics remain lead-based. Pb-free solutions in electronic components and systems are receiving increased attention in the semiconductor and electronics industries. Pb-free materials currently in used are Sn-37Pb, Sn-4Ag and Sn-4Ag-0.5Cu/Ni plate joints. In this study, solder alloys were used at high temperatures for artificial aging processing that was performed at $150^{\circ}C$ for 0hr, 100hr, 200hr, 400hr, 600hr and 1000hr. The SP test was conducted at $30^{\circ}C$ and $50^{\circ}C$. As a result, the maximum shear strength of all the specimens decreased with the increase in artificial aging time and temperature of the SP test. In addition, Pb-free solders showed higher total fracture energy compared with Sn-37Pb at high temperatures. The mechanical properties of Sn-4Ag-0.5Cu solder/Ni plate joints remained in excellent conditions in electronic parking systems at high temperatures.