증류수 및 NaCl 용액내 SnPb 솔더 합금의 Electrochemical Migration 우세 확산원소 분석

정자영,이신복,유영란,김영식,주영창,박영배,Jung, Ja-Young,Lee, Shin-Bok,Yoo, Young-Ran,Kim, Young-Sik,Joo, Young-Chang,Park, Young-Bae 한국마이크로전자및패키징학회 2006 마이크로전자 및 패키징학회지 Vol.13 No.3

인쇄회로기판이나 플라스틱 패키지 등 다양한 전자소자 부품내 배선간 간격이 갈수록 좁아짐에 따라 최근 많이 발생하고 있는 electrochemical migration(ECM) 현상은 양극에서 이온화된 금속에 의한 conductive anodic filament(CAF) 및 덴드라이트와 같은 전도성 필라멘트의 성장으로 인해 전자부품의 절연파괴를 일으키고 있다. 본 연구에서는 공정조성 Sn-37Pb솔더 합금의 ECM 거동과 부식특성 사이의 연관성 평가를 통해 ECM 우세원소를 파악하기 위해 D.I Water 및 NaCl 용액에서 Water Drop Test(WDT)와 분극실험을 실시하여 서로 비교하였다. WDT 실시 결과 공정조성 Sn-37Pb 솔더 합금에서 Pb-rich 상이 Sn-rich 상보다 우선적으로 양극 패드에서 녹아나서 상대적으로 ECM 저항성이 낮았으며, 음극패드에서 자라난 덴드라이트에도 Pb가 훨씬 많이 존재하였다. NaCl에서의 분극실험 결과 전기화학적으로 부동태 피막을 형성하는 Sn에 비해 Pb의 부식속도가 크게 나타났으며, WDT의 결과와 같은 경향을 보였다. 따라서 공정조성 SnPb 솔더 합금의 부식저항성과 ECM 저항성 사이에는 좋은 상관관계가 존재한다. Higher density integration and adoption of new materials in advanced electronic package systems result in severe electrochemical reliability issues in microelectronic packaging due to higher electric field under high temperature and humidity conditions. Under these harsh conditions, metal interconnects respond to applied voltages by electrochemical ionization and conductive filament formation, which leads to short-circuit failure of the electronic package. In this work, in-situ water drop test and evaluation of corrosion characteristics for SnPb solder alloys in D.I. water and NaCl solutions were carried out to understand the fundamental electrochemical migration characteristics and to correlate each other. It was revealed that electrochemical migration behavior of SnPb solder alloys was closely related to the corrosion characteristics, and Pb was primarily ionized in both D.I. water and $Cl^{-}$ solutions. The quality of passive film formed at film surface seems to be critical not only for corrosion resistance but also for ECM resistance of solder alloys.

공정조성 SnPb Solder 합금의 부식 및 Electrochemical Migration 특성에 미치는 SO₄^2- 이온의 영향

정자영,유영란,이신복,김영식,주영창,박영배,Jung, Ja-Young,Yoo, Young-Ran,Lee, Shin-Bok,Kim, Young-Sik,Joo, Young-Chang,Park, Young-Bae 한국재료학회 2007 한국재료학회지 Vol.17 No.1

Electrochemical migration phenomenon is correlated with ionization of anode electrode, and ionization of anode metal has similar mechanism with corrosion phenomenon. In this work, in-situ water drop test and evaluation of corrosion characteristics for SnPb solder alloys in $Na_2SO_4$ solutions were carried out to understand the fundamental electrochemical migration characteristics and to correlate each other. It was revealed that electrochemical migration behavior of SnPb solder alloys was closely related to the corrosion characteristics, and Sn Ivas primarily ionized in ${SO_4}{^2-}$ solutions. The quality of passive film formed at film surface seems to be critical not only for corrosion resistance but also for electrochemical migration resistance of solder alloys.

NaBr 및 NaF 용액에 대한 Sn-3.0Ag-0.5Cu 솔더 합금의 Electrochemical Migration 특성

정자영,장은정,유영란,이신복,김영식,주영창,정태주,이규환,박영배,Jung, Ja-Young,Jang, Eun-Jung,Yoo, Young-Ran,Lee, Shin-Bok,Kim, Young-Sik,Joo, Young-Chang,Chung, Tai-Joo,Lee, Kyu-Hwan,Park, Young-Bae 대한용접접합학회 2007 대한용접·접합학회지 Vol.25 No.3

Electrochemical migration characteristics of Pb-free solder alloys are quantitatively correlated with corrosion characteristics in harsh environment conditions. In-situ water drop test and corrosion resistance test for Sn-3.0Ag-0.5Cu solder alloys were carried out in NaBr and NaF solutions to obtain the electrochemical migration lifetime and pitting potential, respectively. Sn-3.0Ag-0.5Cu solder alloy shows similar ionization and electrochemical migration behavior with pure Sn because of Ag and Cu do not migrate due to the formation of resistant intermetallic compounds inside solder itself. Electrochemical migration lifetime in NaBr is longer than in NaF, which seems to be closely related to higher pitting potential in NaBr than NaF solution. Therefore, it was revealed that electrochemical migration lifetime of Sn-3.0Ag-0.5Cu solder alloys showed good correlation to the corrosion resistance, and also the initial ionization step at anode side is believed to be the rate-determining step during electrochemical migration of Pb-free solders in these environments.

잉크젯 프린팅된 은(Ag) 박막의 등온 열처리에 따른 미세조직과 전기 비저항 특성 평가

최수홍,정정규,김인영,정현철,정재우,주영창,Choi, Soo-Hong,Jung, Jung-Kyu,Kim, In-Young,Jung, Hyun-Chul,Joung, Jae-Woo,Joo, Young-Chang 한국재료학회 2007 한국재료학회지 Vol.17 No.9

Interest in use of ink-jet printing for pattern-on-demand fabrication of metal interconnects without complicated and wasteful etching process has been on rapid increase. However, ink-jet printing is a wet process and needs an additional thermal treatment such as an annealing process. Since a metal ink is a suspension containing metal nanoparticles and organic capping molecules to prevent aggregation of them, the microstructure of an ink-jet printed metal interconnect 'as dried' can be characterized as a stack of loosely packed nanoparticles. Therefore, during being treated thermally, an inkjet-printed interconnect is likely to evolve a characteristic microstructure, different from that of the conventionally vacuum-deposited metal films. Microstructure characteristics can significantly affect the corresponding electrical and mechanical properties. The characteristics of change in microstructure and electrical resistivity of inkjet-printed silver (Ag) films when annealed isothermally at a temperature between 170 and $240^{\circ}C$ were analyzed. The change in electrical resistivity was described using the first-order exponential decay kinetics. The corresponding activation energy of 0.44 eV was explained in terms of a thermally-activated mechanism, i.e., migration of point defects such as vacancy-oxygen pairs, rather than microstructure evolution such as grain growth or change in porosity.

솔더합금의 일렉트로케미컬 마이그레이션 특성분석

이신복(Shin-Bok Lee),유영란(Young-Ran Yoo),정자영(Ja-Young Jung),박영배(Young-Bae Park),김영식(Young-Sik Kim),주영창(Young-Chang Joo) 대한기계학회 2005 대한기계학회 춘추학술대회 Vol.2005 No.5

Smaller size and higher integration of electronic components make smaller gap between metal conducting layers in electronic package. Under harsh environmental conditions (high temperature/humidity), electronic component respond to applied voltages by electrochemically ionization of metal and metal filament formation, which lead to short failure and this phenomenon is termed electrochemical migration(ECM). In this work, printed circuit board(PCB) and model test system made on wafer were used for determination of ECM characteristics. Copper leads of PCB and under bump metallurgy on wafer were soldered by various solder alloys. Insulation breakdown time was measured at 85℃/85%RH or water drop test. Polarization tests in chloride or chloride-free solutions for pure metal and various solder alloys were performed to understand ECM characteristics. Details on migration mechanism and lifetime statistics will be presented and discussed.

PCB에서의 ECM 특성에 미치는 SnPb 솔더 합금의 분극거동의 영향

이신복,유영란,정자영,박영배,김영식,주영창,Lee Shin-Bok,Yoo Young-Ran,Jung Ja-Young,Park Young-Bae,Kim Young-Sik,Joo Young-Chang 한국마이크로전자및패키징학회 2005 마이크로전자 및 패키징학회지 Vol.12 No.2

전자 부품의 크기가 점점 줄어들고 고집적화됨에 따라 전자 패키지 내부에 사용되는 금속간 간격이 줄어들고 있다. 이에 더하여 고온 고습한 환경에서 금속간에 전압이 인가되면 금속의 이온화가 촉진, 금속으로 이루어진 필라멘트가 형성되어 결국 절연파괴에 이르게 된다. 이러한 현상이 electrochemical migration(ECM)이다. 이에 인쇄회로기판을 사용하여 ECM 특성 평가를 수행하였다. 항온/항습조건($85^{\circ}C,\;85{\%}RH$)에서 PCB의 $300 {\mu}m$의 단자간격을 가진 through-hole via 표면에서 발생하는 ECM 현상은 CAF가 절연파괴의 주된 메커니즘이었다. solder를 구성하는 Sn과 Pb 조성 분석을 통해 Pb 의 이온 이동도가 Sn의 이온 이동도보다 큰 것을 알 수 있었으며 이는 급격한 양극용해 거동을 보이는 pure Pb의 분극거동과 상관관계가 있는 것으로 사료된다. 또한 시간에 따른 절연파괴시간 시험을 통하여 ECM에 의한 절연파괴시간이 인가전압에 의존하며 인가전압 의존성 지수값(n)은 2로 나타났다. Smaller size and higher integration of electronic components make smaller gap between metal conducting layers in electronic package. Under harsh environmental conditions (high temperature/humidity), electronic component respond to applied voltages by electrochemically ionization of metal and metal filament formation, which lead to short failure and this phenomenon is termed electrochemical migration(ECM). In this work, printed circuit board(PCB) is used for determination of ECM characteristics. Copper leads of PCB are soldered by eutectic solder alloys. Insulation breakdown time is measured at $85^{\circ}C,\;85{\%}RH$. CAF is the main mechanism of ECM at PCB. Pb is more susceptible to CAF rather than Sn, which corresponds well to the corrosion resistance of solder materials in aqueous environment. Polarization tests in chloride or chloride-free solutions fur pure metal and eutectic solder alloys are performed to understand ECM characteristics. Lifetime results show well defined log-normal distribution which resulted in biased voltage factor(n=2) by voltage scaling. Details on migration mechanism and lifetime statistics will be presented and discussed.

반도체 배선용 저 유전 물질에서의 구리 확산에 대한 전기적 신뢰성 평가

이희찬,주영창,노현욱,윤도영,이진규,차국헌,Lee Hee-Chan,Joo Young-Chang,Ro Hyun-Wook,Yoon Do-Young,Lee Jin-kyu,Char Kook-Heon 한국마이크로전자및패키징학회 2004 마이크로전자 및 패키징학회지 Vol.11 No.3

PMSSQ (Poly Methyl Silsesquioxane)-based matrix에 BTMSE (Bis Tri Methoxy Silyl Ethane) 를 첨가한 low-k물질의 전기적 특성을 조사하였다. 우리는 절연체로 copolymer를 사용하여 금속-절연체 -실리콘 구조를 만들고 BTS 실험을 통하여 누설 전류와 파괴 시간을 측정하였다. 코 폴리머의 기공이 $30\%$ 이상이 되었을 때, 파괴 시간이 급속하게 감소되어 진다. 온도에 관하여 파괴 시간으로부터 코 폴리머를 통한 구리 확산의 활성화 에너지는 1.51eV가 측정되었다. We investigated the electrical properties of copolymer low-k materials that are compromised of the PMSSQ(Poly Methyl Silsesquioxane)-based matrix with the BTMSE (Bis Tri Methoxy Silyl Ethane) additives. We manufactured MIS-type test samples using the copolymer as the insulator and measured their leakage current and failure time by means of the BTS (bias-temperature-stress) test. The failure time was observed to decrease drastically when the porosity of the copolymer was increased over $30\%$. From the measurement of failure time with respect to temperature. the activation energy of Cu drift through the copolymer was calculated to be 1.51 eV.

3차원 적층 패키지를 위한 Cu/thin Sn/Cu 범프구조의 금속간화합물 성장거동분석

박영배 ( Young Bae Park ),김재원 ( Jae Won Kim ),김병준 ( Byoung Joon Kim ),김재동 ( Jae Dong Kim ),주영창 ( Young Chang Joo ),이기욱 ( Ki Wook Lee ),정명혁 ( Myeong Hyeok Jeong ),곽병현 ( Byung Hyun Kwak ) 대한금속재료학회(구 대한금속학회) 2011 대한금속·재료학회지 Vol.49 No.2

Isothermal annealing and electromigration tests were performed at 125℃ and 125℃, 3.6×104 A/cm2 conditions, respectively, in order to compare the growth kinetics of the intermetallic compound (IMC) in the Cu/thin Sn/Cu bump. Cu6Sn5 and Cu3Sn formed at the Cu/thin Sn/Cu interfaces where most of the Sn phase transformed into the Cu6Sn5 phase. Only a few regions of Sn were not consumed and trapped between the transformed regions. The limited supply of Sn atoms and the continued proliferation of Cu atoms enhanced the formation of the Cu3Sn phase at the Cu pillar/Cu6Sn5 interface. The IMC thickness increased linearly with the square root of annealing time, and increased linearly with the current stressing time, which means that the current stressing accelerated the interfacial reaction. Abrupt changes in the IMC growth velocities at a specific testing time were closely related to the phase transition from Cu6Sn5 to Cu3Sn phases after complete consumption of the remaining Sn phase due to the limited amount of the Sn phase in the Cu/thin Sn/Cu bump, which implies that the relative thickness ratios of Cu and Sn significantly affect Cu-Sn IMC growth kinetics.

잉크젯 프린팅된 Cu 박막의 응력해소를 통한 전기적 특성 개선

이설민,주영창,Yi, Seol-Min,Joo, Young-Chang 한국마이크로전자및패키징학회 2014 마이크로전자 및 패키징학회지 Vol.21 No.4

미래형 유연소자 개발 시 비용감소 및 공정적합성 개선을 위해 동박을 잉크젯 프린팅법을 이용해 공중합체 유연기판 상 형성하고, 전기적 특성에 열처리 분위기가 미치는 영향을 확인하기 위해 3 종류의 환원분위기에서 열처리를 진행하여 보았다. 그 결과 200도의 낮은 온도에서 환원 특성이 뛰어난 포름산 분위기에서 전도체 수준의 비저항은 얻을 수 있었으나, 열처리 시 발생하는 응력으로 인해 발생된 표면균열에 기인해 그 값이 기존 동박에 비해 매우 높았다. 이에 비정질재료에서 응용되는 응력해소법을 응용하여 표면균열을 억제한 결과 230도 열처리 시 기존 열처리 방법에서는 $7.4{\mu}{\Omega}cm$의 비저항을 보이나, 응력해소를 통한 표면 균열이 억제된 시편에서는 $3.4{\mu}{\Omega}cm$의 비저항 값을 얻을 수 있었다. 특히 등온열처리에 의한 응력해소 효과를 확인하기 위해 동일 온도에서 등온시간 없이 열처리를 진행한 결과, 표면균열이 억제되지 못함을 확인할 수 있었다. Using flexible bismaleimide-triazine co-polymer as a substrate, inkjet-printed Cu films were also investigated for low-cost and process feasibility of flexible electronics. After annealing at $200^{\circ}C$ for 1 h under various reducing ambient, surface color was changed to red and electrical resistivity was decreased to the level of conductor under formic acid ambient. However, its resistivity was much higher than conventional copper films due to surface crack. In order to reduce the residual film stress after annealing, additional isothermal treatment was inserted before anneal hiring the stress relaxation applied in processes of amorphous materials. As a result, no surface crack was observed and electrical resistivity of $3.4{\mu}{\Omega}cm$ was measured after annealing at $230^{\circ}C$ with stress relaxation while electrical resistivity of $7.4{\mu}{\Omega}cm$ was observed after normal annealing without relaxation. The effect of stress relaxation was also confirmed by observing surface crack after decreasing the relaxation time to 0 min.

공정조성 SnPb 솔더 라인의 온도에 따른 Electromigration 확산원소의 In-situ 분석

김오한,윤민승,주영창,박영배,Kim Oh-Han,Yoon Min-Seung,Joo Young-Chang,Park Young-Bae 한국마이크로전자및패키징학회 2006 마이크로전자 및 패키징학회지 Vol.13 No.1

63Sn-37Pb 솔더의 실시간 electromigration 거동 관찰을 박막형 edge 이동 선형시편과 주사전자현미경을 이용하여 실시하였다. 공정조성 63Sn-37Pb 솔더의 electromigration에 의한 edge 이동 잠복기는 $90{\sim}110^{\circ}C$에서 뚜렷하게 존재하였다. 온도에 따른 electromigration 우선확산원소는 실험온도 $90{\sim}110^{\circ}C$에서 Pb, $25{\sim}50^{\circ}C$에서는 Sn으로 나타났고, $70^{\circ]C$에서는 Sn과 Pb가 거의 동시에 이동하여 우선확산 원소가 관찰되지 않았다. $90{\sim}110^{\circ}C$에서 관찰된 SnPb의 electromigration에 의한 edge 이동 잠복기는 Pb 우선이동에 의해 발생되었다. 이러한 edge 이동 잠복기의 존재는 플립칩 (flip chip) 솔더범프의 수명과 밀접한 관계를 가지는 것으로 보인다. Electromigration에 의해 발생되는 SnPb 솔더의 우선확산원소의 온도 의존성은 Pb와 Sn의 확산계수와 함께 $Z^*$ (전기장내의 유효전하 수)도 크게 영향을 미치는 것으로 생각된다. In-situ observation of electromigration in thin film pattern of 63Sn-37Pb solder was performed using a scanning electron microscope system. The 63Sn-37Pb solder had the incubation stage of electromigration for edge movement when the current density of $6.0{\times}10^{4}A/cm^2$ was applied the temperature between $90^{\circ}C\;and\;110^{\circ}C$. The major diffusion elements due to electromigration were Pb and Sn at temperatures of $90-110^{\circ}C\;and\;25-50^{\circ}C$, respectively, while no major diffusion of any element due to electromigration was detected when the test temperature was $70^{\circ}C$. The reason was that both the elements of Sn and Pb were migrated simultaneously under such a stress condition. The existence of the incubation stage was observed due to Pb migration before Sn migration at $90-110^{\circ}C$. Electromigration behavior of 63Sn-37Pb solder had an incubation time in common for edge drift and void nucleation, which seemed to be related the lifetime of flip chip solder bump. Diffusivity with $Z^*$(effective charges number) of Pb and Sn were strongly affect the electromigration-induced major diffusion element in SnPb solder by temperature, respectively.