The bonding characteristics and high-temperature reliability of gold bonding wires wereinvestigated with respect to the thickness of the aluminum pads and the addition of palladium. Samples ofhigh-purity gold (99.99%, 4N) and gold with 1% palladium added (99% purity, 2N) were processed into15.3 m diameter ultra-fine wires through wire drawing and bonded to aluminum pads with thicknesses of1 m and 5 m using ball bonding equipment. The reliability at elevated temperatures was evaluated byannealing at 175oC for up to 1,000 hours. Micro-structural and intermetallic compound (IMC) phase changesat the vertical cross-sections of bonded areas were characterized using SEM-EDS at specific time intervals. For 1 m aluminum pads, both 4N and 2N gold wires initially exhibited identical bonding ball morphologies. Voids began to form at the lateral sections after 250 hours, accompanied by the formation of Au8Al3 and Au4Alphases. Despite these observations, stable bonding was maintained up to 1,000 hours, with the palladiumaddition proving advantageous in terms of bonding strength. On the other hand, for 5 m aluminum pads,IMCs in the 4N wire were stabilized as Au8Al3, maintaining the bond interface for up to 1,000 hours. However,for the 2N wire, significant voids were observed beneath the bond interface as early as 250 hours. These voidswere attributed to the incorporation of palladium, which caused the growth of AuAl2 into Au2Al, leading torapid shrinkage due to phase transformation occurring at a very early stage. Therefore, the addition ofpalladium is less favorable when using 5 m thick aluminum pads, as it induces different inter-diffusionphenomena compared to 1 m pads, resulting in void formation.

This study investigated changes in electrical and mechanical properties, as well as the highhumidity reliability of 18 m-diameter silver alloy wires with palladium contents of 1.1, 2.5, 3.0, and 4.0 wt%,for semiconductor packaging. We also compared the formation of Free Air Ball (FAB) and the high humidityreliability of joints in a reducing atmosphere with 4N (99.99%) gold wire of the same diameter. The wireresistance and hardness values were measured using a 4-point probe and a micro-hardness tester. The FABformed in atmospheric and reducing atmospheres, as well as the high humidity reliability after bonding, wereanalyzed using field emission scanning electron microscopy, energy dispersive spectrometry, and a mechanicalstrength analyzer. As the palladium content increased in the silver alloy wire, the electrical resistanceincreased, showing a similar level to gold wire up to 2.5 wt%, after which it exhibited a further increase. Thehardness values also increased sharply, but the rate of increase slowed down after 2.5 wt%. FAB exhibitedexcellent sphericity across the entire range of palladium content. After bonding, a uniform distribution ofpalladium was observed at the joint interface. The high humidity reliability showed improvement withincreasing palladium content. Palladium 1.1 wt% exhibited differences compared to 2.5 and 3.0 wt%, andfurther improvement was observed with an increase to 4.0 wt%. This is attributed to the incorporation ofpalladium into the vulnerable Ag3Al intermetallic compound, resulting in the formation of a corrosionresistant (AgPd)3Al phase. As a result, micro-diameter silver alloy wires with a diameter of 18 m or lessdemonstrated stable FAB formation, bonding processes, and properties that make them candidates to replaceconventional gold wires, particularly under conditions with palladium content exceeding 2.5 wt%.

The bonding characteristics and high-temperature reliability of gold bonding wires wereinvestigated with respect to the thickness of the aluminum pads and the addition of palladium. Samples ofhigh-purity gold (99.99%, 4N) and gold with 1% palladium added (99% purity, 2N) were processed into15.3 m diameter ultra-fine wires through wire drawing and bonded to aluminum pads with thicknesses of1 m and 5 m using ball bonding equipment. The reliability at elevated temperatures was evaluated byannealing at 175oC for up to 1,000 hours. Micro-structural and intermetallic compound (IMC) phase changesat the vertical cross-sections of bonded areas were characterized using SEM-EDS at specific time intervals. For 1 m aluminum pads, both 4N and 2N gold wires initially exhibited identical bonding ball morphologies. Voids began to form at the lateral sections after 250 hours, accompanied by the formation of Au8Al3 and Au4Alphases. Despite these observations, stable bonding was maintained up to 1,000 hours, with the palladiumaddition proving advantageous in terms of bonding strength. On the other hand, for 5 m aluminum pads,IMCs in the 4N wire were stabilized as Au8Al3, maintaining the bond interface for up to 1,000 hours. However,for the 2N wire, significant voids were observed beneath the bond interface as early as 250 hours. These voidswere attributed to the incorporation of palladium, which caused the growth of AuAl2 into Au2Al, leading torapid shrinkage due to phase transformation occurring at a very early stage. Therefore, the addition ofpalladium is less favorable when using 5 m thick aluminum pads, as it induces different inter-diffusionphenomena compared to 1 m pads, resulting in void formation.

This study investigated changes in electrical and mechanical properties, as well as the highhumidity reliability of 18 m-diameter silver alloy wires with palladium contents of 1.1, 2.5, 3.0, and 4.0 wt%,for semiconductor packaging. We also compared the formation of Free Air Ball (FAB) and the high humidityreliability of joints in a reducing atmosphere with 4N (99.99%) gold wire of the same diameter. The wireresistance and hardness values were measured using a 4-point probe and a micro-hardness tester. The FABformed in atmospheric and reducing atmospheres, as well as the high humidity reliability after bonding, wereanalyzed using field emission scanning electron microscopy, energy dispersive spectrometry, and a mechanicalstrength analyzer. As the palladium content increased in the silver alloy wire, the electrical resistanceincreased, showing a similar level to gold wire up to 2.5 wt%, after which it exhibited a further increase. Thehardness values also increased sharply, but the rate of increase slowed down after 2.5 wt%. FAB exhibitedexcellent sphericity across the entire range of palladium content. After bonding, a uniform distribution ofpalladium was observed at the joint interface. The high humidity reliability showed improvement withincreasing palladium content. Palladium 1.1 wt% exhibited differences compared to 2.5 and 3.0 wt%, andfurther improvement was observed with an increase to 4.0 wt%. This is attributed to the incorporation ofpalladium into the vulnerable Ag3Al intermetallic compound, resulting in the formation of a corrosionresistant (AgPd)3Al phase. As a result, micro-diameter silver alloy wires with a diameter of 18 m or lessdemonstrated stable FAB formation, bonding processes, and properties that make them candidates to replaceconventional gold wires, particularly under conditions with palladium content exceeding 2.5 wt%.

This study investigated the photovoltaic properties and microstructure of perovskite solar cells (PSCs) with an ITO/SnO2/perovskite/HTL/Au electrode configuration, developed with varying sintering temperatures (100~200°C). The goal was to use SnO2 ink as the electron transport layer (ETL) by lowtemperature sintering. TGA-DTA analysis was conducted to determine the optimum sintering temperature of the SnO2 ink and the photovoltaic properties were examined by solar simulator analysis. To analyze the microstructure, a 3D profiler, optical microscope, and scanning electron microscopy (SEM) were used. The TGA-DTA analysis results show that SnO2 ink was effectively sintered at the low temperature of 80°C and above. As for the photovoltaic(PV) properties, the PV efficiency was approximately 15% at 120~150°C, and increased to a maximum of 17.16% at 180°C, and then fell to 12% at 200°C. The RMS value, a representation of surface roughness, of the SnO2 layer according to sintering temperature incrementally decreased, reached its lowest at 180°C, before finally increasing. The microstructure analysis showed that the perovskite layer formed on the SnO2 at a sintering temperature of 180°C had a relatively greater grain size of 402 nm and a thickness of 432 nm, thereby improving the PSC’s PV properties. These results suggest it is possible to implement a PCS with SnO2 ETL by low temperature sintering process.

We investigated interfacial reactions and structural changes occurring in 15 um -diameter goldbonding wires with varying palladium contents (0, 0.05, 0.1, 0.3, and 1.0%) bonded to 5 um-thick aluminumpads and subjected to accelerated high-temperature testing at 175°C for up to 1,000 h. Compared withconventional 1um aluminum pads, the increased aluminum thickness in 5 um pads caused most of the firstball bond area to transform into intermetallic compounds overtime. For gold bonding wires without palladiumaddition, rapid gold diffusion resulted in deformation of the first ball bond after 250 h at 175°C . After 1,000 h,all gold at the top of the first ball bond was consumed, forming a thin neck and leading to crack formation. As the palladium content increased, a Pd-rich barrier formed between the first ball bond region and the IMClayer, slowing the diffusion of gold into the aluminum pad. This helped preserve the gold at the top of thefirst ball bond and maintained a stable bonding interface even after 1,000 h. However, in the case of goldbonding wires containing 1.0% palladium, after 250 h, the Pd-rich barrier further slowed gold diffusion whileaccelerating aluminum diffusion, resulting in the formation of large voids in the aluminum pad area. Therefore, when applying 15 um fine gold bonding wires to relatively thick 5 um aluminum pads, the additionof an appropriate palladium content (approximately 0.05–0.3%) was found to be advantageous for ensuringhigh-temperature reliability.

이 연구의 목적은 금속 3D프린터가 금속공예나 주얼리 분야에서 활용되기 위해 각 용도에 맞는 공정조건을 도출하는 것이다. 분말적층용융(PBF) 방식의 금속 3D 프린팅 방법 중 하나인 선택적 레이저용융(SLM) 공정은 금속분말을 레이저로 용융시킨 후 다시 굳히는 과정을 반복하며 적층 시키는 제조방식으로서 정교하고 복잡한 형상을 가진 제품을 만들 수 있는 장점을 지닌다. 그러나 적층 과정 내발생하는 급격한 가열 및 냉각은 공극 형성 및 미세구조 변화를 야기하는데, 이는 난발과 같은 부분의강도 및 내구성을 저하시키는 주요한 원인이 될 수 있다. 연구방법은 스테인리스강 SUS316L 분말을이용하여 다양한 레이저 출력과 주사 속도를 조절해 에너지밀도를 변화시켜 바뀐 값에 따른 상대밀도값을 도출하는 방식으로 진행되었다. 이후 경도 및 인장시험을 통해 강도와 연성을 확인하였으며, 이를 통해 주얼리 작업에 최적화된 강도와 연성을 갖는 공정조건을 수립하였다. 연구결과 주조의 어려움으로 그동안 스테인리스를 사용한 주얼리는 디자인에 제한이 많았으나 PBF방식의 장점을 활용하여서포트 없이 트러스들이 중공 구조를 이루어 기존의 정밀주조로는 제작이 어려운 주얼리 형상을 SLM 공정으로 출력할 수 있었다. 파우더기반인 SLM출력방식의 특성상 광택이 없는 출력물의 표면은 스레인리스 합금으로 경도가 높았으나 주얼리의 폴리싱도구를 통해 표면처리가 가능하였고 도출된 공정조건을 통해 제작된 난발로 큐빅 지르코니아와 같이 경도가 높지 않은 스톤도 기존의 세공 도구를 사용하여 세팅할 수 있음을 확인하였다.

고순도 H2 정제용 ZrVFe 합금을 대기 중에 상온으로 보관시 발생하는 표면부의 오염을 제거하기 위한 전처리 공정으로, UVO3 크리닝 공정을 제안하였다. 보관 60일까지 시간에 따른 표면부 오염에 의한 물성 변화를 optical microscopy, micro-Raman, XRD 방법으로 확인하고, UVO3 크리닝 공정 전후 물성을 비교하였다. 상온 보관 시간에 따라 준비된 시료와 이들을 UVO3 공정으로 처리한 뒤 표면부에 VOx, FeVOx와 같은 Oxide계 오염물의 형성과 카본계 물질의 흡착 오염 정도에 따른 물성 변화는 광학현미경 이미지와 XRD로 확인할 수는 없었지만, micro-Raman 분석으로 오염물의 존재와 제거 여부에 대해 명확히 확인할 수 있었다. 이는 ZrVFe 합금 게터가 상온 대기 중에서 보관시간에 따라 나노급 두께의 VOx, FeVOx와 같은 금속 산화물을 형성하며, 이렇게 생성된 Oxide계 오염물은 UVO3를 통해 비교적 간단히 제거할 수 있음을 의미하였다. 따라서 UVO3 크리닝 공정으로 ZrVFe 합금의 표면부 오염층을 효과적으로 제거할 수 있으며, 오염물이 제거된 ZrVFe 합금은 향상된 고순도 H2 가스 정제 기능을 가질 수 있었다.

A 1.8 μm thick polycrystalline diamond (PCD) thin film layer is prepared on a Si(100) substrate using hot-filament chemical vapor deposition. Thereafter, its thermal conductivity is measured using the conventional laser flash analysis (LFA) method, a LaserPIT-M2 instrument, and the newly proposed light source thermal analysis (LSTA) method. The LSTA method measures the thermal conductivity of the prepared PCD thin film layer using an ultraviolet (UV) lamp with a wavelength of 395 nm as the heat source and a thermocouple installed at a specific distance. In addition, the microstructure and quality of the prepared PCD thin films are evaluated using an optical microscope, a field emission scanning electron microscope, and a micro-Raman spectroscope. The LFA, LaserPIT-M2, and LSTA determine the thermal conductivities of the PCD thin films, which are 1.7, 1430, and 213.43 W/(m·K), respectively, indicating that the LFA method and LaserPIT-M2 are prone to errors. Considering the grain size of PCD, we conclude that the LSTA method is the most reliable one for determining the thermal conductivity of the fabricated PCD thin film layers. Therefore, the proposed LSTA method presents significant potential for the accurate and reliable measurement of the thermal conductivity of PCD thin films.

A porous ZrFe alloy specimen was prepared as a 6 × 3 mm (diameter × thickness) disk. The reaction of the ZrFe alloy was confirmed while the whole system was maintained at a target temperature, which was increased from 150 oC to 950 oC in a 99.999% low purity nitrogen atmosphere, consisting of 10 ppm of impurity gas. Surface color, pore size, stabilized layer, and phase change were confirmed with optical microscopy, scanning electron microscopy-energy dispersive X-ray spectroscopy, X-ray diffraction, X-ray photoelectron spectroscopy, and Micro-Raman, according to temperature. The surface color of the ZrFe alloy changed from metallic silver to dark gray as the temperature increased. In the EDS and XPS results, nitrogen component was not observed, and oxygen content increased on each surface at the elevated temperatures. In this way, the ZrFe alloy was stabilized in a low purity nitrogen atmosphere, preventing rapid nitride reactions.

금속 공예가들은 금속의 색상표현을 위해 다양한 착색기법을 연구해 왔다. 많은 착색 방법들 가운데애노다이징 기법을 이용한 알루미늄 착색은 간섭색을 이용한 착색이나 넓은 판재의 애노다이징에는고가의 장비와 다공성 표면에 유해한 염료 투입후 봉공처리가 필요한 공정상의 제한이 있었다. 이에연구자는 내마모성이 뛰어나고 두께에 따라 다양한 간섭색을 나타내는 diamond-like carbon(DLC) 박막에 주목하였다. 이 연구의 목적은 두께에 따라 비철금속인 백동과 적동 기판에 충분한 접합성과간섭색이 나는지 확인하기 위함이다. 연구 방법은 백동과 적동 판재를 이용하여 네 가지의 도형을 조합한 패턴을 부식시켜 준비하고 공정시간을 달리하여 네 가지의 두께로 DLC 박막을 코팅하였다. 각조건에서의 두께와 색상을 주사전자현미경, 색 분석기를 이용하여 확인하고. DLC 박막의 반사모드만을 고려한 모델로 간섭색을 예측해보았다. DLC 코팅 후 코팅된 금속 시편을 10개의 색상 팔레트로 사용해 색을 조합하여 두 개의 브로치를 제작하였고 직경 25cm로 성형된 기물에 보라색 DLC 코팅을적용해 제작 가능성을 확인 하였다. 브로치의 제안에서는 코팅한 표면 위를 일부 연마해 본래의 금속색과 코팅된 색의 차이를 대비시켜 연출하여 생동감 있는 표현과 DLC 코팅을 연마용 버로 일부 제거하고 바탕 금속이 부분 노출되게 하여 입사법과 비슷한 색상의 대비효과를 얻을 수 있었다. 또한 이연구를 통해 큰 직경의 기물에서는 그동안 표현되기 어려웠던 남보라 계열의 색상 표현과 반복된 마스킹 작업 없이 높이에 따른 간섭색의 그라데이션을 통해 풍부한 색상 표현이 가능하였다.