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Synthesis and Properties of UV Laser Debondable Temporary Bonding and Debonding Adhesives for 3D Multi-chip Packaging Process

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Authors
이승우
Advisor
김현중
Major
농업생명과학대학 산림과학부
Issue Date
2015-02
Publisher
서울대학교 대학원
Keywords
Adhesivesdual-curing3D multi-chip packagingtemporary bonding and debondingUV laser debondingfluorinated urethane adhesive
Description
학위논문 (박사)-- 서울대학교 대학원 : 산림과학부, 2015. 2. 김현중.
Abstract
Recently, mobile devices with a focus on smartphone require both high performance and lightness at the same time, so TSV (Through Silicon Via) 3D multi-chip package technology was emerging. In order to realize this technique, temporary bonding and debonding adhesive is required to process silicon wafer and handling. However, using the existing adhesive handling a thin silicon wafer having a thickness of less than 50 μm is not easy. There are two main reasons for this. First, to maintain the high purity, it is required to have over 200 oC processing temperature during the process of bonding and debonding. Due to this thermal degradation, it generates low molecular weight substances and cause contamination to the thin silicon wafer. Second, while debonding, strong adhesive force can crack or cracking the thin silicon wafer and generate defects.
In this study, the perspective on temporary bonding for TSV (Through Silicon Via) 3D multichip packaging and the perspective on debonding afterwards are divided into each technique elements, and these elements are to be used to newly synthesize the adhesive. Plus, the mechanisms of curing and debonding are to be analyzed through these property evaluations.
In this study, the non-solvent type urethane acrylic adhesive was designed and manufactured to improve the disadvantages such as the phenomenon on flowing adhesive out from the silicon wafer after the spinning coating which the conventional solvent-based adhesive have during temporary bonding, the phenomenon of uneven coating thickness by contaminated wafer surface from the solvent evaporation and the phenomenon on the contamination of the work area. During the urethane synthesis, isophorone diisocyante was used as a hard segment and silicone-based diols (not conventional hydrocarbon-based diols) was used as a soft segment to improve the heat resistance of the polymer structure. Also, designing for dual curing adhesive that further introduce a photo-curing after thermal curing was made (rather than a single curable adhesive, such as the conventional light curing or thermal curing) to improve the heat resistance. A multi-functional acrylic monomer was end-capped to one end of the synthesized urethane oligomer and a monomer containing a fluorine was end-capped to the other end for to analyze the measurement of the number of functional groups of the multifunctional acrylic monomer, the density of the UV irradiation energy, hardening behavior, thermal stability and the peel strength depending on the amount of photoinitiator used. As a result, the number of functional acrylic monomer was in mono On the other hand, this study used the method of edge zone debonding, using the UV laser, to consider both temporary bonding and debonding. While the conventional method requiring a bonding temperature of 200 ~ 220 oC, this study was able to proceed the bonding at a low temperature of 80 ~ 150 oC. Furthermore, this study has done debonding within two minutes using a UV laser, rather than the conventional way in which this process takes time over 6 hours by a penetration of the solvent. For this purpose, BTHPEMA (2- [3- (2-Benzotriazol-2-yl) -4-hydroxyphenyl] ethyl methacrylate) was introduced when preparing the adhesive. When debonding, identification (BTHPEMA playing a role of being the LTHC (light to heat conversion)) for debonding progression of the polymer film formation by the heat cure adhesive was made through thermal curing mechanism of epoxy functionality by the FTIR-ATR analysis and the gel fraction measurement. Absorbency, for a UV laser of a synthesis adhesive, was determined according to wavelength using a UV-visible spectroscopy. As a result, 355 nm in wavelength bands indicate the absorption of up to 60% of the binder prepared in accordance with the increase amount of BTHPEMA comparison 0.4 phr input, and the UV laser absorbency of the adhesive synthesized was adjustable by varying the blending ratio. Moreover, it was confirmed that the joined debonding was composed in the effective energy density conditions of the UV laser irradiation with 5.65 to 6.72 J/cm2.
Language
English
URI
https://hdl.handle.net/10371/121074
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College of Agriculture and Life Sciences (농업생명과학대학)Dept. of Forest Sciences (산림과학부)Theses (Ph.D. / Sc.D._산림과학부)
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