• 대한전기학회논문지:전기물성ㆍ응용부문C
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• 제48권8호
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• pp.598-604
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• 1999

This paper describes the research to minimize the film stress and maximize the aspect ratio of photoresist structure, especially about SU-8 for electroplating mold. UV LIGA process using SU-8 allows fabricating high aspect ratio polymer structures. However, it is hard to get fine patterns in the high aspect ratio structures because of high internal stress and difficulty of removing SU-8. The purpose of this paper is to setup the process condition for the obtainment of both low film stress and high aspect ratio and to find design rules that make the pattern be less dependent on stress problem. Firstly, the process of heat treatment and exposure of SU-8 are proposed. These two conditions control the amount of cross-linkage in polymer structure, which is the most important parameter of both pattern generation and remaining stress. Heat treatment is dealed with soft bake and post-exposure-bake. Temperature and time duration of each step are varied with heat treatment condition. Some test patterns are fabricated to evaluate the proposed process. Nickel electroplating is performed with the mold fabricated through the proposed process to confirm the SU-8 as a good electroplating mold.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2004년도 추계학술대회논문집
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• pp.276-279
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• 2004

The factors affecting Ni-Co alloy electroforming were investigated to determine the optimum bath composition and electroplating parameters, like pH, temperature, and current density, suitable for high speed fabrication of a micro mold with longer lifetime. To obtain alloy deposits having uniform thickness and composition, electroplating parameters were finely tuned with home-made electroforming apparatus. Ni-Co alloy deposits had linearly increased Co with $Co^{2+}$ ion concentration in electroplating bath, and showing $412H_v$ of Victors hardness at $23wt\%$ of Co content. For Ni-Co alloy, sulfonate and diol related organic additives were very effective to alleviate its residual stress and surface roughness. The maximum deposition rate was $106{\mu}m/hr$ at 10ASD and the tensile strength of alloy deposit was 2 times larger than that of Ni only case.

• 제어로봇시스템학회논문지
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• 제14권4호
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• pp.361-364
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• 2008

Tips of probe card were fabricated using MEMS technology. P-type silicon wafer with $SiO_2$ layer was used as a substrate for fabricating the probe card. Ni-Cr and Au used as seed layer for electroplating Ni were deposited on the silicon wafer. Line patterns for probing devices were formed on silicon wafer by electroplating Ni through mold which formed by MEMS technology. Bridge structure was formed by wet-etching the silicon substrate. AZ-1512 photoresist was used for protection layer of back side and DNB-H100PL-40 photoresist was used for patterning of the front side. The mold with the thickness of $60{\mu}m$ was also formed using THB-120N photoresist and probe tip with thickness of $50{\mu}m$ was fabricated by electroplating process.

• 한국정밀공학회지
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• 제23권2호
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• pp.138-145
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• 2006

An injection molding is necessary to mass-product for micro-nano system, so micro-nano mold must be developed for injection molding. The micro-nano mold has precision and strength to overcome a surround of injection. So in this paper, two methods were used. First, after etching the Al, Ni was electroplated in etched AI. The other, LIGA method was used. A temperature and thickness of Ni are important factors in these methods. So after fabrication, the simulation was processed to find optimal thickenss of Ni and temperature.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1998년도 하계학술대회 논문집 G
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• pp.2541-2543
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• 1998

This paper describes the fabrication process to fabricate metallic structure of high aspect ratio using LlGA-like process. SU-8 is used as an electroplating mold. SU-8 is an epoxy-based photoresist, designed for ultrathick PR structure with single layer coating [1,2]. We can get more than $100{\mu}m$ thick layer by single coating with conventional spin coater, and applying multiple coating can make thicker layers. In the experiments, we used different kinds of SU-8, having different viscosity. To optimize the conditions for mold fabrication process, experiments are performed varying spinning time and speed, soft-bake, develop and PEB (Post Expose Bake) condition. With the optimized condition, minimum line and space of $3{\mu}m$ pattern with a thickness of $40{\mu}m$ and $4{\mu}m$ pattern with a thickness of $130{\mu}m$ were obtained. Using the patterned PR as a plating mold, metallic structure was fabricated by electroplating. We have fabricated a electroplated nickel comb actuator using SU-8 as plating mold. The thickness of PR mold is $45{\mu}m$ and that of plated nickel is$40{\mu}m$. Minimum line of the mold is $5{\mu}m$. Patterned metallic layer or polymer layer, which has selectivity with the structural plated metallic layer, can be used as sacrificial layer for fabrication of free-standing structure.

• Design & Manufacturing
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• 제6권1호
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• pp.95-100
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• 2012

In this study, a novel Cu composite sheet with embedded high electric conduction path was developed as another alternative for the interconnect materials possessing high electrical conductivity as well as high strength. The Cu composite sheet was fabricated by forming Ag conduction paths not within the interior but on the surface of a high strength Cu substrate by damascene electroplating process. As a result, the electrical conductivity increased by 40% thanks to mesh type Ag conduction paths, while the ultimate tensile strength decreased by 20%. The interfacial fracture resistance of Cu composite sheet prepared by damascene electroplating increased by above 50 times compared to Cu composite sheet by conventional electroplating. For feasibility test for practical application, a leadframe for LED module was manufactured by a progressive blanking and piercing processes, and the blanked surface profile was evaluated as a function of the volume fraction of Ag conduction paths. As Ag conduction path became finer, pressing formability improved.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2002년도 하계학술대회 논문집 C
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• pp.2008-2010
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• 2002

Process conditions of a novel negative thick photoresist, JSR THB-$430N^{(R)}$, are established in this paper. Although SU-8 obtains uniform and high-aspect-ratio structures, it is hard to remove the SU-8 mold after electroplating. The JSR THB-$430N^{(R)}$ can be more easily removed than the SU-8 and has a low internal stress. Introducing two step strip processes using acetone and the jSR THB-$S1^{(R)}$, the JSR THB-$430N^{(R)}$ electroplating mold was removed completely and a JSR THB-$430N^{(R)}$ film stress is compressive less than 2 MPa. In this paper, we obatined $200{\mu}m$ thick PR structure and $100{\mu}m$ thick electroplated nickel structure using the JSR THB-$430N^{(R)}$ photoresist.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2006년도 춘계학술대회 논문집
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• pp.143-144
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• 2006

In this paper, we proposed XP KMPR-1050 negative tone resist to replace SU-8 resist for multi-layer micro-structures and thick plating mold fabrication using UV-LIGA process. XP KMPR resist proposed in this paper can be easily striped using a common stripping solution such as NMP without damage of micro-structure. The conditions for the fabrication of XP KMPR micro-structure were optimized by adjustment of exposure and post-exposure bake(PEB). The $140{\mu}m$ -thick and an aspect ratio at least 10 micro-structure and multi-layer structures were successfully fabricated through the process conditions. Through-mold electroplating and PR striping of XP KMPR has been successfully demonstrated.

• 한국재료학회지
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• 제13권1호
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• pp.6-10
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• 2003

Electroplated Ni and Ni-W micro-molds using LIGA-like process for replication of micro-components such as microfluidic parts and micro optical parts have been investigated. In general, it is hard to produce micro-parts using conventional mechanical processes. Micro-mold formed by LIGA-like process could fabricate micro-parts with high aspect ratio. In this paper, fabrication and properties of electroplated Ni molds with varying applied current types as well as those of Ni-W molds were investigated. Ni molds fabricated under pulse-reverse current showed the highest hardness value of about 160 Hv. Ni-W molds showed the hardness of about 500 Hv which was much harder than that of Ni electroplated molds. The above results suggested that high quality micro-molds could be fabricated by using Ni electroplating of pulse-reverse type for core molds and sequential Ni-W alloys coating.

• 제어로봇시스템학회논문지
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• 제14권4호
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• pp.332-335
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• 2008

PMMA light guiding plate with nano pattern was fabricated by nano imprint lithography method. A silicon mold for electroplating of nickel was fabricated by conventional photolithography process. A nickel stamp for nano imprint lithography was fabricated by electroplating process using silicon mold. The nano imprint lithography was performed on PMMA plate at $140^{\circ}C$ under pressure of 20kN. The nano pattern on PMMA plate was investigated using FE-SEM. It is shown that the patterns were well transferred for several steps and the nano imprint lithography method could be applied for fabricating patterns of light guiding plate.