• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2016.11a
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• pp.175-175
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• 2016

Sn도금액은 강산에서는 $Sn^{2+}$, 강알칼리에서는 $Sn^{4+}$석출이 안정하다. 중성영역은 도금액에 $Sn^{2+}$침전을 방지하기 위하여 착화제가 필요하다. 기록에 남아 있는 가장 오래된 Sn도금은 1856년 Gore가 4가의 주석산염을 사용한 알칼리성용액이다. 그 후 50~60년 사이에 2가의 염화주석($SnCl_2$)과 KOH에 Cyan 등의 착화제를 첨가한 도금액이 발표되었다. 최초의 실용적인 알칼리주석용액은 1931년 Oplinger의 4가 주석산 염으로서, $CH_3COONa$를 완충제로 사용하였고, $Sn^{2+}$을 산화시키기 위하여 과산화물이나 과 붕산염을 첨가하였다. 알칼리성 Sn용액은 Natrium용액과 Kalium용액이 있지만, Kalium염이 용해성이 좋고, Sn농도를 높여 전류밀도를 높일 수 있다. 알칼리성용액은 도금속도가 산성용액의 1/2로 되고, 음극효율도 80~90% 정도 낮아, 두꺼운 피막이나 생산성을 중시하는 부품에는 적합하지 않다. 초기의 산성용액은 Sn의 정련목적으로 사용되었고, Pb정련에 사용된 Fluor규산용액에 Gelatine을 첨가하였다. Mathers는 Cresol산을 첨가하여 미량의 Cresol포화용액을 사용하여 고속으로 두껍게 석출시킬 수 있었다. 독일의 Schloetter도 다양한 방향족 술폰산으로써 반 광택피막을 실현하였다. 산성Sn도금액은 첨가제에 어떠한 유기화합물을 사용하는가는 도금장치나 석출상태로써 결정할 수 있다. Hothersall과 Bradshaw는 Cresol술폰산을 첨가하여 도금액 안정성 향상을 발견했다. Cresol술폰산은 $Sn^{2+}$의 안정제이며, Gelatine은 분산제기능을 한다. 붕 불화용액은 Sn농도를 높일 수 있고, $2{\sim}12A/dm^2$의 고 전류밀도의 도금이 가능하다. 1937년 Schloetter가 개발하여 미국의 제철회사에서 사용되었다. Sn-Ni도금은 Ni도금보다도 뛰어난 내식성이 있기 때문에 자전거, 자동차부품에 사용되고 있다. 실용도금액은 1951년 Parkinson이 발표한 HBF/HCL용액이다. $SnCl_2$산성용액에서 표준전위는 -0.136V인데 비하여, Ni이온의 표준전위는 -0.25V이다. HF용액에서는 불화물이온이 $Sn^{2+}$의 석출전위를 (-)방향으로 이동시켜서 합금석출이 가능하다. Sn-Co도금은 Cr도금의 색조에 가깝고, 장식목적으로 사용된다. Cr도금 대체용으로 사용된다. 내마모성이나 내식성은 Cr도금보다도 떨어지기 때문에 장식목적에 한정된다. 1953년 Parkinson은 Sn-Ni도금연구에서 동일한 용액조성으로부터 Co 30%를 석출시켰다. Sn-Zn도금은 방식도금으로서 자동차부품에 많이 사용되고 있다. Sn과 Zn의 표준전위는 서로 멀리 떨어져 있기 때문에 산성용액에서는 공석될 수 없다. 1980년대에 들면서, 방식Cd(Cadmium)도금의 독성 때문에 Sn-Zn도금을 재인식 하게 되었다. 1957년 Vaid 등이 No Cyan도금액을 발표했다. 그 후 러시아의 연구자가 안정한 도금액을 연구하였고, Srivastava와 Muckergee가 1976년에 종합하였다.

• Proceedings of the International Microelectronics And Packaging Society Conference
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• 2002.05a
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• pp.85-91
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• 2002

Even though electroless Hi and Sn-Ag-Cu solder are widely used materials in electronic packaging applications, interfacial reactions of the ternary Ni-Cu~Sn system have not been known well because of their complexity. Because the growth of intermetallics at the interface affects reliability of solder joint, the intermetallics in Ni-Cu-Sn system should be identified, and their growth should be investigated. Therefore, in present study, interfacial reactions between electroless Ni UB7f and 95.5Sn-4.0Ag-0.5Cu alloy were investigated focusing on morphology of the IMCs, thermodynamics, and growth kinetics. The IMCs that appear during a reflow and an aging are different each other. In early stage of a reflow, ternary IMC whose composition is Ni$_{22}$Cu$_{29}$Sn$_{49}$ forms firstly. Due to the lack of Cu diffusion, Ni$_{34}$Cu$_{6}$Sn$_{60}$ phase begins growing in a further reflow. Finally, the Ni$_{22}$Cu$_{29}$Sn$_{49}$ IMC grows abnormally and spalls into the molten solder. The transition of the IMCs from Ni$_{22}$Cu$_{29}$Sn$_{49}$ to Ni$_{34}$Cu$_{6}$Sn$_{60}$ was observed at a specific temperature. From the measurement of activation energy of each IMC, growth kinetics was discussed. In contrast to the reflow, three kinds of IMCs (Ni$_{22}$Cu$_{29}$Sn$_{49}$, Ni$_{20}$Cu$_{28}$Au$_{5}$, and Ni$_{34}$Cu$_{6}$Sn$_{60}$) were observed in order during an aging. All of the IMCs were well attached on UBM. Au in the quaternary IMC, which originates from immersion Au plating, prevents abnormal growth and separation of the IMC. Growth of each IMC is very dependent to the aging temperature because of its high activation energy. Besides the IMCs at the interface, plate-like Ag3Sn IMC grows as solder bump size inside solder bump. The abnormally grown Ni$_{22}$Cu$_{29}$Sn$_{49}$ and Ag$_3$Sn IMCs can be origins of brittle failure.failure.

• Korean Journal of Heritage: History & Science
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• v.52 no.1
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• pp.4-21
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• 2019

In this paper, 23 Silla gold earrings from the sixth and seventhand centuries, excavated from the Yeongnam region, were analyzed. Based on the silver content of the gold plate, they were classified into three types. The classifications included type I(20-50wt%), type II(10-20wt%) and type III (less than 10wt%). In the analysis process, the composition and morphological differences were identified on the surface of the gold plate. In the case of type I and II earrings, it was observed that the fine holes were concentrated in a relatively higher part of the gold content. The causes of the difference in the surface composition of the gold plate were divided into four categories: 1) surface treatment, 2) thermal diffusivity in the manufacturing process, 3) differences in composition of alluvial gold, and 4) the refining method of gold. It is possible that depletion gilding was attempted to increase the gold content while intentionally removing the other metals from the surface of the gold alloy in the portion where the gold deposit is relatively concentrated on the surface of the gold plating. The highest copper content was detected in the earring with the highest gold content of the analyzed earrings, and it was assumed that thermal diffusion had occurred between the gold plate and the metal rod during the manufacturing process rather than intentional addition. Copper was detected only in the thin ring earring type, and copper was not detected in the thick ring earring type or pendant type. It also proves that this earring has a high degree of tightness at higher temperatures, as there was an invisible edge finish on other earrings and horizontal wrinkles on the gold plate surface. In terms of the material of the gold plate, we examined whether the silver content of the gold plate was natural gold or added by alloy through analyzing the alluvial gold collected in the region. As a result of the analysis, it was found that on average about 13wt% of silver is included. This suggests that type II is natural gold, type III is refined gold, and type I seems to have been alloyed with natural gold. Here, we investigated the refining method introduced in the ancient literature, both at home and abroad, about the possibility of alloying silver after the refining process of type III earrings and then making pure gold. It was found that from ancient refining methods, silver which had been present in the natural gold was removed by reacting and combining with silver chloride or silver sulfide, and long-term efforts and techniques were required to obtain pure gold through this method. Therefore, it was concluded that the possibility of adding a small amount of silver in order to increase strength after making pure gold through a refining process is low.