• 마이크로전자및패키징학회지
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• 제29권2호
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• pp.1-10
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• 2022

최근 반도체 소자는 모바일 전자제품과 wearable 및 flexible한 소자와 기판의 다양한 활용으로 많은 분야에서 폭넓게 사용되고 있다. 이들 반도체 칩 접합 공정 중 기판과 솔더의 열팽창 계수(CTE)의 차이와 기판 및 부품 전체에 인가되는 과도한 열 영향은 소자의 성능 및 신뢰성에 영향을 주며, 최종적으로 휨(warpage) 현상 및 장기 신뢰성 저하 등을 초래한다. 이러한 문제점을 개선하기 위해 저온에서 공정이 가능한 저융점 솔더에 대한 연구가 활발히 진행되고 있다. Sn-Bi, Sn-In 등 다양한 저융점 솔더 합금 중 Sn-Bi 솔더는 높은 항복 강도, 적절한 기계적 특성 및 저렴한 가격 등의 이점이 있어 유망한 저온 솔더로 각광받고 있다. 그러나 Bi의 높은 취성 특성 등 단점으로 인해 솔더 합금의 개선이 필요하다. 본 review 논문에서는 다양한 미량 원소와 입자를 첨가하여 Sn-Bi 소재의 기계적 특성 개선을 위한 연구 동향을 소개하며 이를 비교 분석하였다.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2009년도 추계학술대회 논문집
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• pp.699-700
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• 2009

• 마이크로전자및패키징학회지
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• 제19권1호
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• pp.17-24
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• 2012

Recently, flip chip interconnection has been increasingly used in microelectronic assemblies. The common Flip chip interconnection is formed by reflow of the solder bumps. Lead-Tin solders and Tin-based solders are most widely used for the solder bump materials. However, the flip chip interconnection using these solder materials cannot be applied to temperature-sensitive components since solder reflow is performed at relatively high temperature. Therefore the development of low temperature bonding technologies is required in these applications. A few bonding techniques at low temperature of $150^{\circ}C$ or below have been reported. They include the reflow soldering using low melting point solder bumps, the transient liquid phase bonding by inter-diffusion between two solders, and the bonding using low temperature curable adhesive. This paper reviews various low temperature bonding methods.

• 한국전기전자재료학회논문지
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• 제37권1호
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• pp.74-78
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• 2024

We have studied the effects of Ag on the characteristics of Sn₄₈In₅₂Ag_x (wt%) low-melting solders for photovoltaic ribbons. The Sn₄₈In₅₂ (wt%) solder coexisted in the InSn₄ and In₃Sn alloys. Ag atoms added in the solder formed an AgIn₂ alloy by reacting with some part of In atoms, while they did not react with Sn atoms. The addition of Ag atoms in the Sn₄₈In₅₂Ag_x (wt%) solders showed useful results; an increase in peel strength and a decrease in melting temperature. The peel strength of the ribbon plated with the Sn₄₈In₅₂ (wt%) solder was 53.6 N/mm², and that of the Sn₄₈In₅₂Ag₁ (wt%) solder largely increased to 125.1 N/mm². In the meanwhile, the melting temperature of the Sn₄₈In₅₂ (wt%) solder was 119.2℃, and that of the Sn₄₈In₅₂Ag₁ (wt%) solder decreased to 114.0℃.

• ETRI Journal
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• 제35권2호
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• pp.340-343
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• 2013

A novel bumping process using solder bump maker is developed for the maskless low-volume solder on pad (SoP) technology of fine-pitch flip chip bonding. The process includes two main steps: one is the aggregation of powdered solder on the metal pads on a substrate via an increase in temperature, and the other is the reflow of the deposited powder to form a low-volume SoP. Since the surface tension that exists when the solder is below its melting point is the major driving force of the solder deposit, only a small quantity of powdered solder adjacent to the pads can join the aggregation process to obtain a uniform, low-volume SoP array on the substrate, regardless of the pad configurations. Through this process, an SoP array on an organic substrate with a pitch of $130{\mu}m$ is successfully formed.

• ETRI Journal
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• 제41권6호
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• pp.820-828
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• 2019

A highly reliable conductive adhesive obtained by transient liquid-phase sintering (TLPS) technologies is studied for use in high-power device packaging. TLPS involves the low-temperature reaction of a low-melting metal or alloy with a high-melting metal or alloy to form a reacted metal matrix. For a TLPS material (consisting of Ag-coated Cu, a Sn96.5-Ag3.0-Cu0.5 solder, and a volatile fluxing resin) used herein, the melting temperature of the metal matrix exceeds the bonding temperature. After bonding of the TLPS material, a unique melting peak of TLPS is observed at 356 ℃, consistent with the transient behavior of Ag₃Sn + Cu₆Sn₅ → liquid + Cu₃Sn reported by the National Institute of Standards and Technology. The TLPS material shows superior thermal conductivity as compared with other commercially available Ag pastes under the same specimen preparation conditions. In conclusion, the TLPS material can be a promising candidate for a highly reliable conductive adhesive in power device packaging because remelting of the SAC305 solder, which is widely used in conventional power modules, is not observed.

• Journal of Welding and Joining
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• 제16권3호
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• pp.157-166
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• 1998

Recently as environmental pollution caused by Pb has posed a serious threat to the global environment, the trend to regulate the usage of Pb in electronic industry is one the rise. Currently, the solder alloy with high Pb content, Sn-37%Pb, is utilized in the electronic assembly therefore, the objective of this study is to develop an alternative solder alloy for the existing Sn-37%Pb solder alloy. First thing, this work choosed Sn-5%Pb-1.5%Ag, Sn-5%Pb-1.5%Ag-x%Bi(x=1~5%) for candidate solder alloys, and examined their properties such as melting range, wettability, microhardness, tensile property, oxidation behavior and microstructure. Wettability was on the same level of Sn-37%Pb. Dissolution of Pb ion in Sn-5%Pb solder was 0.46ppm. This solder alloy revealed cellular dendrite microstructure $\beta$-Sn matrix, Pb-rich phase, Ag/Sn, and Cu/Sn Intermetallic compounds. The range of solidification temperature was within 3$0^{\circ}C$. Also these alloy displayed higher tensile strength and lower elongation than Sn-37%Pb. The resistance of oxidation in Sn-5%Pb-1.5%Ag solder alloy was superior to that of Sn-37%Pb solder alloy. But that of Sn-5%Pb-1.5%Ag-5%Bi solder alloy was equal to that of Sn-37%Pb solder alloy.

• 한국재료학회지
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• 제21권12호
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• pp.673-678
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• 2011

With an increased production of Printed Circuit Boards (PCBs) in electronic equipment, the consumption of solder alloys is growing globally. Recently, increasing importance of recycling solder scrap has been recognized. Generally, solder scrap contains many impurities such as plastics and other metals. Hazardous components must be eliminated for recycling solder scrap. The present work studied pretreatment for reuse of solder scrap alloys. An experiment was conducted to enhance the cleanliness of solder scrap melt and eliminate impurities, especially lead. Physical separation with sieving and magnetic force was made along with pyrometallurgical methods. A small decrease in lead concentration was found by high temperature treatment of solder scrap melt. The impurities were removed by filtration of the solder scrap melt, which resulted in improvement of the melt cleanliness. A very low concentration of lead was achieved by a zone melting treatment with repeated passage. This study reports on a pretreatment process for the reuse of solder scrap that is lead free.

• 한국전기전자재료학회논문지
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• 제36권2호
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• pp.186-190
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• 2023

We studied the various characteristics of Sn-In (wt%) Pb-free solders for photovoltaic ribbon application. The solders near the eutectic composition of Sn₄₈In₅₂ (wt%) existed in InSn₄ and In₃Sn alloy phases, and in In crystal phase, but not in Sn crystal phase. In addition, the InSn₄ phase (γ-alloy) existed separately from the In₃Sn (β-alloy) and the In phase confirmed by an SEM-EDS-mapping. The melting temperature of the eutectic solder of Sn₄₈In₅₂ (wt%) was 119.2℃, and when the Sn content decreased in reference to the eutectic composition, it slightly increased to 121.4℃, but when the Sn content increased, it remained almost constant at 119.1℃. The peel strength of the ribbon plated with the Sn₄₂In₅₈ (wt%) solder was 38.7 N/mm², and it tended to increase when the Sn content increased. The peel strength of the eutectic Sn₄₈In₅₂ (wt%) solder was 53.6 N/mm², and that of the Sn₅₁In₄₉ (wt%) solder was 61.6 N/mm² that was the highest.

• 대한용접접합학회:학술대회논문집
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• 대한용접접합학회 2002년도 Proceedings of the International Welding/Joining Conference-Korea
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• pp.450-455
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• 2002

Cu-cored Sn-Ag solder balls were fabricated by coating pure Sn and Ag on Cu balls. The melting behavior and the solderability of the BGA joint with the Ni/Au coated Cu pad were investigated and were compared with those of the commercial Sn-Ag and Sn-Ag-Cu balls. DSC analyses clarified the melting of Cu-cored solders to start at a rather low temperature, the eutectic temperature of Sn-Ag-Cu. It was ascribed to the diffusion of Cu and Ag into Sn plating during the heating process. After reflow soldering the microstructures of the solder and of the interfacial layer between the solder and the Cu pad were analyzed with SEM and EPMA. By EDX analysis, formation of a eutectic microstructure composing of $\beta$-Sn, Ag$_3$Sn, ad Cu$_{6}$Sn$_{5}$ phases was confirmed in the solder, and the η'-(Au, Co, Cu, Ni)$_{6}$Sn$_{5}$ reaction layer was found to form at the interface between the solder and the Cu pad. By conducting shear tests, it was found that the BGA joint using Cu-cored solder ball could prevent the degradation of joint strength during aging at 423K because of the slower growth me of η'-(Au, Co, Cu, Ni)$_{6}$Sn$_{5}$ reaction layer formed at the solder, pad interface. Furthermore, Cu-cored multi-component Sn-Ag-Bi balls were fabricated by sequentially coating the binary Sn-Ag and Sn-Bi solders on Cu balls. The reflow property of these solder balls was investigated. Melting of these solder balls was clarified to start at the almost same temperature as that of Sn-2Ag-0.75Cu-3Bi solder. A microstructure composing of (Sn), Ag$_3$Sn, Bi and Cu$_{6}$Sn$_{5}$ phases was found to form in the solder ball, and a reaction layer containing primarily η'-(Au, Co, Cu, Ni)$_{6}$Sn$_{5}$ was found at the interface with Ni/Au coated Cu pad after reflow soldering. By conducting shear test, it was found that the BGA joints using this Cu-core solder balls hardly degraded their joint shear strength during aging at 423K due to the slower growth rate of the η'-(Au, Cu, Ni)$_{6}$Sn$_{5}$ reaction layer at the solder/pad interface.he solder/pad interface.