• Journal of Welding and Joining
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• v.30 no.2
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• pp.65-69
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• 2012

Environmental and health concerns over the lead have led to investigation of the alternative Pb-free solders to replace commonly used Pb-Sn solders in microelectronic packaging application. The leading candidates for lead-free solder alloys are presently the near eutectic Sn-Ag-Cu alloys. Therefore, extensive studies on reliability related with the composition have been reported. However, the insufficient drop property of the near eutectic Sn-Ag-Cu alloys has demanded solder compositions of low Ag content. In addition, the solder interconnections in automobile applications like a smart box require significantly improved vibration resistance. Therefore, this study investigated the effect of alloying elements (Ag, Bi, In) on the vibration fatigue strength. The vibration fatigue was conducted in 10~1000Hz frequency and 20Grms. The interface of the as-soldered cross section close to the Cu pad indicated the intermetallic compound ($Cu_6Sn_5$) regardless of solder composition. The type and thickness of IMC was not significantly changed after the vibration test. It indicates that no thermal activities occurred significantly during vibration. Furthermore, as a function of alloying composition, the vibration crack path was investigated with a focus on the IMCs. Vibration crack was initiated from the fillet surface of the heel for QFP parts and from the plating layer of chip parts. Regardless of the solder composition, the crack during a vibration test was propagated as same as that during a thermal fatigue test.

• Journal of the Microelectronics and Packaging Society
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• v.7 no.2
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• pp.47-53
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• 2000

The fluxless wetting properties of TSM-coated glass substrate were evaluated by the wetting balance method. We could estimate the wettability of the TSM with new parameters obtained from the wetting balance test for one side-coated specimen. It was more effective in wetting to use Cu as a wetting layer and Au as a protection layer than to use Au itself as a wetting layer. The SnSb solder showed better wettability than SnAg, SnBi, and SnIn solders. The contact angle of the one side-coated glass substrate to the Pb-free solders could be calculated from the farce balance equation by measuring the static force and the tilt angle.

• Journal of the Microelectronics and Packaging Society
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• v.16 no.4
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• pp.23-28
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• 2009

We investigated the wafer-level MEMS capping process for which cavity formation in Si wafer was not required. Ni caps were formed by electrodeposition on 4" Si wafer and Ni rims of the Ni caps were bonded to the Cu rims of bottom Si wafer by using epoxy. Then, top Si wafer was debonded from the Ni cap structures by using SnBi layer of low melting temperature. As-evaporated SnBi layer was composed of double layers of Bi and Sn due to the large difference in vapor pressures of Bi and Sn. With keeping the as-evaporated SnBi layer at $150^{\circ}C$ for more than 15 sec, SnBi alloy composed of eutectic phase and Bi-rich $\beta$ phase was formed by interdiffusion of Sn and Bi. Debonding between top Si wafer and Ni cap structures was accomplished by melting of the SnBi layer at $150^{\circ}C$.

• Proceedings of the International Microelectronics And Packaging Society Conference
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• 2001.11a
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• pp.75-87
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• 2001

Three different kinds of substrate used in this study : bare Cu substrate, Ni-P/Cu substrate with a Ni-P layer thickness of $5\mu\textrm{m},$ and Au/Ni-P/Cu substrate with the Ni-P and Au layers of $0.15\mu\textrm{m}$ and $5\mu\textrm{m}$ thickness respectively. The wettability of various Sn-base solders was affected by the substrate metal finish used, i.e., nickel, gold and copper. On the Au/Ni-F/Cu substrate, Sn-base solders wet better than any of the other substrate metal finishes tested. The interfacial reaction between various substrate and Sn-base solder was investigated at $70^{\circ}C,$ $100^{\circ}C,$ $120^{\circ}C,$ $150^{\circ}C,$ $170^{\circ}C$ and $200^{\circ}C$ for reaction times ranging from 0 day to 60 day. Intermetallic phases was formed along a Sn-base solder/ various substrate interface during solid-state aging. The apparent activation energy for growth of Sn-Ag/Cu, Sn-Ag-Bi/Cu, and Sn-Bi/Cu couples were 65.4, 88.6, and 127.9 Kj/mol, respectively. After isothermal aging, the fracture surface shoved various characteristics depending on aging temperature and time, and the types of BGA pad.

• Korean Journal of Materials Research
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• v.7 no.4
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• pp.303-309
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• 1997

기존의 전자 기판에서 땜납으로 사용되고 있는 Sn-Pb계 합금을 대체하기 위한 새로운 합금을 개발하기 위하여 열역학을 이용한 상평형계산을 통해 얻은 다원계 상태도를 바탕으로 적정한 녹는점과 용융구간을 가지는 Sn-Bi-In-Zn계 솔더합금을 설계하였다. 설계된 합금을 제작하여 XRD, DSC및 EDX로 분석하여 상의 확인,조성분석 및 고상점과 액상점 등의 녹음 거동을 확인하였다. 또한 열처리에 따른 미세구조의 변화를 관찰하였고, 이러한 조직변화가 기계적 성질에 미치는 영향을 경도실험과 인장실험을 통해 연구하였다.

• Clean Technology
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• v.11 no.3
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• pp.153-164
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• 2005

This study found a reliable evaluation for four kinds of pb-Free plating solutions and it's layers, through pure Sn, SnAg, SnBi and SnCu. These four kind of solutions are widely used to pb-Free plating. Hull-cell, Harring-blum, coverage, throwing power, current efficiency, stability, life-time, composition, hardness, roughness, abrasion, scratch, solderability, corrosion, contact angle, morphology, SIR(Surface insulation resistance) and Whisker test were experimented. Also, Using ICP, XRF, FE-SEM, EDS, temperature/humidity chamber, solderability tester, hardness tester, roughness tester, abrasion tester, salt spray tester, contact angle tester, SIR tester, and microscope. In this paper could be shown the systematic and various analysis for reliability about four kinds of pb-Free plating solutions, processes and it's deposit surface.

• Journal of the Korean Solar Energy Society
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• v.38 no.1
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• pp.45-55
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• 2018

Environmentally benign lead-free solder coated ribbon (e. g. SnCu, SnZn, SnBi${\cdots}$) has been intensively studied to interconnect cells without lead mixed ribbon (e. g. SnPb) in the crystalline silicon(c-Si) photovoltaic modules. However, high melting point (> $200^{\circ}C$) of non-lead based solder provokes increased thermo-mechanical stress during its soldering process, which causes early degradation of PV module with it. Hence, we proposed low-temperature conductive paste (CP) based tabbing method for lead-free ribbon. Modules, interconnected by the lead-free solder (SnCu) employing CP approach, exhibits similar output without increased resistivity losses at initial condition, in comparison with traditional high temperature soldering method. Moreover, 400 cycles (2,000 hour) of thermal cycle test reveals that the module integrated by CP approach withstands thermo-mechanical stress. Furthermore, this approach guarantees strong mechanical adhesion (peel strength of ~ 2 N) between cell and lead-free ribbons. Therefore, the CP based tabbing process for lead free ribbons enables to interconnect cells in c-Si PV module, without deteriorating its performance.

• Proceedings of the International Microelectronics And Packaging Society Conference
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• 2000.04a
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• pp.81-86
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• 2000

To evaluate the possibility of the partial melting soldering. wettability of partial melted solders was measured using wetting balance. Off eutectic Sn-Pb allows are wettable in their partial melting zone. Especially, Pb rich alloys showed excellent wettability while wettability of Sn rich alloys were adequate or poor. It is found that wettability increases over $200^{\circ}C$ regardless of composition liquid fraction and phases of the original alloy Sn-7Ag alloy showed good wettability in their partial melting zone, while Sn-65Bi alloy was non-wettable under their melting points.

• Journal of the Microelectronics and Packaging Society
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• v.28 no.2
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• pp.65-70
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• 2021

In this study, interfacial properties and mechanical properties of joints were reported after Cu pads finished with organic solderability preservative (OSP) on flame retardant-4 (FR-4) printed circuit board (PCB) and electronic components were joined with a Sn-57Bi-1Ag solder paste by using a laser bonding process. The laser bonding process was performed under various bonding conditions with changing a laser power and a bonding time and effects of bonding conditions on interfacial and mechanical properties of joints were analyzed. In order to apply for industry, properties of bonding joints using a reflow bonding process which are widely used were compared. When the laser bonding process were performed, we observed that Cu₆Sn₅ intermetallic compounds (IMCs) were fully formed at the interface although the bonding times were very short about 2 and 3 s. Furthermore, void formations of the joints by using the laser bonding process were suppressed at the joints with comparing to the reflow bonding process and shear strengths of bonding joints were higher than that by using the reflow bonding process. Therefore, in spite of a very short bonding time, it is expected that joints will be stably formed and have a high mechanical strength by using the laser bonding process.

• Proceedings of the International Microelectronics And Packaging Society Conference
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• 2004.09a
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• pp.79-92
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• 2004

RoHS compliant products are now being mass-produced. Eco-product(Pb-free+RoHS compliant+Halogen-free) will be possible from 2005. Pb-free flip chip will be qualified by 2004. 4Q. Lead Finish: SnBi-Under mass production Pd PPF-Under small production Matte Sn-will be internally qualified by 2004. 4Q Development of Pb-free Solder Ball: Stable Supply, Cost Down.