• Restorative Dentistry and Endodontics
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• 제20권1호
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• pp.152-163
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• 1995

This experiment was performed to observe the adhesion pattern and microleakage in the gingival margin according to variation in the resin cement thickness which results from thickness of Die spacer. which is considered to effect the adaptability of the composite resin inlays. Clearfil CR inlays were fabricated on stone models with CR Sep applicated once and Nice fit twice, 4 times, and 6 times each. After 2nd curing within the CRC-100 oven, CR inlays were cemented with CR inlay cement. Dye(2% methylene blue) penetration and adhesion pattern were evaluated after sectioning of gingival margin into :3 pieces. The results were as follows ; 1. The thickness of resin cement showed unevenchanging pattern with that of die spacer, namely, it was increased until 4 times' application of Nice-Fit but was decreased with 6 times' application of that. 2. The degree of dye penetration wasn't affected by cement thickness within a limited value. 3. Most of dye penetration was shown through the interface between cement and enamel rather than the interface between cement and CR inlay. This shows that the affinity of resin cement for CR inlay was superior to the adhesive strength with tooth structure. 4. No gap was found at the interface between enamel and cement but some showed separation between dentin and cement. It is concidered that the contraction force of cement was less than the bond strength with the enamel. 5. Lots of voids were found in the CR inlay and resin cement. There was a pooling tendency of bonding agent and cement in the axiogingival line angle portion. 6. In some specimens, cracks were shown in enamel margin. From this it could be considered that cavity preparation and surface treatment weakened the tooth structure.

• 한국생산제조학회지
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• 제23권4호
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• pp.355-360
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• 2014

Recently, the use of LED is increasing. This paper presents the new package process of thermal compression bonding using metal layered LED chip for the high power LED device. Effective thermal dissipation, which is required in the high power LED device, is achieved by eutectic/flip chip bonding method using metal bond layer on a LED chip. In this study, the process condition for the LED eutectic die bonder system is proposed by using the analysis program, and some experimental results are compared with those obtained using a DST (Die Shear Tester) to illustrate the reliability of the proposed process condition. The cause of bonding failures in the proposed process is also investigated experimentally.

• 마이크로전자및패키징학회지
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• 제19권2호
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• pp.29-33
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• 2012

The demand for 3D wafer level integration has been increasing significantly. Although many technical challenges of wafer stacking are still remaining, wafer stacking is a key technology for 3D integration due to a high volume manufacturing, smaller package size, low cost, and no need for known good die. Among several new process techniques Cu-to-Cu wafer bonding is the key process to be optimized for the high density and high performance IC manufacturing. In this study two main challenges for Cu-to-Cu wafer bonding were evaluated: misalignment and bond quality of bonded wafers. It is demonstrated that the misalignment in a bonded wafer was mainly due to a physical movement of spacer removal step and the bond quality was significantly dependent on Cu bump dishing and oxide erosion by Cu CMP.

• 한국마이크로전자및패키징학회:학술대회논문집
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• 한국마이크로전자및패키징학회 2002년도 International Symposium
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• pp.219-225
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• 2002

This paper presents a novel "bumpless flip chip package"for cost! performance driven devices. Using the conventional electroplating and etching processes, this package enables the production of fine pitch BGA up to 256 I/O with single layer routing. An array of circuitry down to $25-50{\mu}{\textrm}{m}$ line/space is fabricated to fan-in and fan-out of the bond pads without using bumps or substrate. Various types of joint methods can be applied to connect the fine trace and the bond pad directly. The resin-filled terminal provides excellent compliancy between package and the assembled board. More interestingly, the thin film routing is similar to wafer level packaging whereas the fan-out feature enables high lead count devices to be accommodated in the BGA format. Details of the design concepts and processing technology for this novel package are discussed. Trade offs to meet various cost or performance goals for selected applications are suggested. Finally, the importance of design integration early in the technology development cycle with die-level and system-level design teams is highlighted as critical to an optimal design for performance and cost.

• 제어로봇시스템학회논문지
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• 제21권12호
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• pp.1130-1135
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• 2015

The bond pull test is the most widely used technique for the evaluation and control of wire bond quality. The wire being tested is pulled upward until the wire or bond to the die or substrate breaks. The inspector test strength of wire by manually and it takes around 3 minutes to perform the test. In this paper, we develop a 3D vision system to measure 3D position of wire. It gives 3D position data of wire to move a hook into wires. The 3D measurement method to use here is a confocal imaging system. The conventional confocal imaging system is a spot scanning method which has a high resolution and good illumination efficiency. However, a conventional confocal systems has a disadvantage to perform XY axis scanning in order to achieve 3D data in given FOV (Field of View) through spot scanning. We propose a method to improve a parallel mode confocal system using a micro-lens and pin-hole array to remove XY scan. 2D imaging system can detect 2D location of wire and it can reduce time to measure 3D position of wire. In the experimental results, the proposed system can measure 3D position of wire with reasonable accuracy.

• Applied Microscopy
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• 제51권
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• pp.16.1-16.7
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• 2021

Electron microscopy (EM) is an essential imaging method in biological sciences. Since biological specimens are exposed to radiation and vacuum conditions during EM observations, they die due to chemical bond breakage and desiccation. However, some organisms belonging to the taxa of bacteria, fungi, plants, and animals (including beetles, ticks, and tardigrades) have been reported to survive hostile scanning EM (SEM) conditions since the onset of EM. The surviving organisms were observed (i) without chemical fixation, (ii) after mounting to a precooled cold stage, (iii) using cryo-SEM, or (iv) after coating with a thin polymer layer, respectively. Combined use of these techniques may provide a better condition for preservation and live imaging of multicellular organisms for a long time beyond live-cell EM.

• 마이크로전자및패키징학회지
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• 제13권4호
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• pp.1-7
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• 2006

WLCSP(wafer level chip size package)는 웨이퍼 레벨에서 패키지 공정이 이루어지는 차세대 패키지 중 하나이다. WLCSP는 웨이퍼 레벨에서 패키지 공정이 이루어진다는 특징으로 인하여 웨이퍼당 생산되는 반도체 칩의 수에 따라 그 패키징 비용을 크게 줄일 수 있다는 장점이 있다. 그러나 응력 버퍼 역할을 하는 기판을 없애는 혁신적인 구조로 인하여 솔더 조인트의 신뢰성이 기존의 BGA 패키지에 비하여 취약하게 되는데, 이러한 솔더 조인트 신뢰성에 대하여 반도체 칩과 솔더볼을 연결하는 폴리머 절연층은 열팽창계수 차이에 의해 발생하는 응력을 흡수하는 중요한 역할을 하게 된다. 본 연구에서는 하이닉스에서 개발한 Omega-CSP를 사용하여 솔더볼 배열 변화와 제 1 절연층의 특성에 따른 솔더 조인트의 열피로 특성을 평가하였다. 그 결과 절연층의 특성 변화가 솔더 조인트의 열피로 특성에 주는 영향은 솔더볼 배열 구조에 따라 변화되는 것을 확인하였다.

• 대한용접접합학회:학술대회논문집
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• 대한용접접합학회 2005년도 춘계학술발표대회 개요집
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• pp.54-56
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• 2005

Ultrasonic soldering using of Si-wafer to FR-4 PCB atroom temperature was investigated. Sn3.5Ag foil rolled $100{\mu}m$ was used for solder. The UBM of Si-die was Cu/ Ni/ Al from top to bottom and its thickness was $0.4{\mu}m$, $0.4{\mu}m$, $0.3{\mu}m$ respectively. Pad on FR-4 PCB comprised of Au/ Ni/ Cu from top to bottom and its thickness was $0.05{\mu}m$, $5{\mu}m$, $18{\mu}m$ respectively. The ultrasonic soldering time was changed from 0.5sec to 3.0sec and its power 1400W. As experimental result, reliable bond joint by ultrasonic at room temperature was obtained. The shear strength increased with soldering time up to 2.5 sec. That means at 2.5sec, the shear strength showed maximum rate of 65.23N. The strength decreased to 33.90N at 3.0 sec because the cracks generated along the intermetallic compound between Si-wafer and Sn-3.5mass%Ag solder. intermetallic compound produced by ultrasonic between the solder and the Si-die was $(Cu, Ni)_{6}Sn_{5}$ and the intermetallic compound between solder and pad on FR-4 was $(Ni, Cu)_{3}Sn_{4}$.

• ETRI Journal
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• 제39권6호
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• pp.866-873
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• 2017

We propose a multilayered-substrate-based power semiconductor discrete device package for a low switching loss and high heat dissipation. To verify the proposed package, cost-effective, low-temperature co-fired ceramic, multilayered substrates are used. A bare die is attached to an embedded cavity of the multilayered substrate. Because the height of the pad on the top plane of the die and the signal line on the substrate are the same, the length of the bond wires can be shortened. A large number of thermal vias with a high thermal conductivity are embedded in the multilayered substrate to increase the heat dissipation rate of the package. The packaged silicon carbide Schottky barrier diode satisfies the reliability testing of a high-temperature storage life and temperature humidity bias. At $175^{\circ}C$, the forward current is 7 A at a forward voltage of 1.13 V, and the reverse leakage current is below 100 lA up to a reverse voltage of 980 V. The measured maximum reverse current ($I_{RM}$), reverse recovery time ($T_{rr}$), and reverse recovery charge ($Q_{rr}$) are 2.4 A, 16.6 ns, and 19.92 nC, respectively, at a reverse voltage of 300 V and di/dt equal to $300A/{\mu}s$.

• 한국재료학회지
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• 제22권9호
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• pp.454-458
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• 2012

Various adhesive materials are used in flip chip packaging for electrical interconnection and structural reinforcement. In cases of COF(chip on film) packages, low temperature bonding adhesive is currently needed for the utilization of low thermal resistance substrate films, such as PEN(polyethylene naphthalate) and PET(polyethylene terephthalate). In this study, the effects of anhydride and dihydrazide hardeners on the low-temperature snap cure behavior of epoxy based non-conductive pastes(NCPs) were investigated to reduce flip chip bonding temperature. Dynamic DSC(differential scanning calorimetry) and isothermal DEA(dielectric analysis) results showed that the curing rate of MHHPA(hexahydro-4-methylphthalic anhydride) at $160^{\circ}C$ was faster than that of ADH(adipic dihydrazide) when considering the onset and peak curing temperatures. In a die shear test performed after flip chip bonding, however, ADH-containing formulations indicated faster trends in reaching saturated bond strength values due to the post curing effect. More enhanced HAST(highly accelerated stress test) reliability could be achieved in an assembly having a higher initial bond strength and, thus, MHHPA is considered to be a more effective hardener than ADH for low temperature snap cure NCPs.