학술논문
Solution-processable thermally conductive composite adhesives with modified boron nitrides / Boron nitride 표면 개질 및 열전도성 고분자 합성
Document Type
Dissertation/ Thesis
Author
Source
Subject
Language
English
Abstract
최근 기술의 발달로 전자 기기는 점점 더 경량화, 소형화, 집적화가 진행되고있다. 전자 기기는 더 얇고 작아지는데, 집적화가 되면서 더 많은 열이 발생하게된다. 이러한 열은 소자의 기능을 저하시킬 뿐만 아니라, 수명을 단축시킨다. 실제로 기기의 성능 저하 또는 고장의 원인은 55 %가 열로 발생한다. 장치 내부에서 발생한 열을 외부로 열을 방출하는 것은 오작동이나 고장을 방지하는 중요한 기술이다. 따라서, 방출 되는 열을 제어하는 기술에 대해 많은 관심과 연구가 이루어지고 있다. 전자 기기는 수천에서 수만개의 부품으로 조립된다. 이러한 부품들을 접합하기 위해서는 접착제가 필요하다. 접착제의 경우 열전도율이 매우 낮은 고분자 수지이다. 따라서, 이러한 접착제에 의해 열의 전달에 어려움을 겪는다. 최근에는 이러한 문제를 해결하기 위해 고분자에 금속, 탄소재, 세라믹 등 열전도율이 높은 충전제를 첨가한 복합재료가 일반적으로 사용되고 있다. 이를 열전도성 고분자 복합재료라고 한다. 많은 고분자 중에서 에폭시 수지의 기계적, 화학적, 열적 특성이 우수하다. 일반적으로 금속, 탄소재, 세라믹 등의 충전제로 사용된다. 금속의 경우 매우 높은 열전도율을 가지고 있어 매우 좋은 후보이지만, 전기 절연을 필요로 하는 경우 사용이 불가하다. 따라서, 열전도율도 높으며 전기 절연성을 지닌 세라믹 물질을 많이 사용한다. 400 W/m ∙ K 의 고유 열전도도를 가지고 있는 질화 붕소물(BN)이 주목받고 있다. 최근에는 구형보다 방향성을 가지는 판상형 BN 합성되고 있다. 본 연구에서는 에폭시 수지에 열전도율이 높은 BN을 함침시키는 방법을 제시하였다. 열전도성 고분자 복합체의 열의 대부분은 충전제에 의해 전달된다. 에폭시 수지 내에서 충전재의 연결성이 매우 중요하다. BN의 표면개질을 통해 에폭시 내의 함량을 증가시켜 필러의 연결성을 이루어 열경로를 형성시켰다. 또한, 표면개질을 통해 에폭시와 충전재의 계면 저항을 줄여주어 열 손실을 방지하였다. 개질된 BN을 상용화된 접착제에 적용하여 성능시험을 진행 및 개선하였다. 이처럼, 표면 개질 된 BN은 열전도성 고분자 복합재료제조에 도움이 될 것이며 방열 산업에 필요한 충전제 역할을 할 것이다.
Recently, electronic devices such as smartphone, tablet PC and portable device are becoming lighter, smaller and more integrated. As a result, the thermal density rapidly increases, which causes deterioration or failure of electronic devices. It has been reported that heat generation of electronic products causes degradation of product performance, and 55 % of failures are caused by heat generation. Accordingly, the demand for high heat dissipation materials is rapidly increasing. A heat dissipation from the inside of the device to the outside is an important technique for preventing malfunction or failure. An electronic device is a finished product heat is assembled from many parts. Adhesives are often used to assemble them, and these adhesives are polymeric resins with very low thermal conductivity. Recently, in order to solve this problem, a composite material made by adding a high thermal conductivity filling material such as a metal, carbon material and ceramic material to a polymer is generally used. It is called thermally conductive polymer composite. Among many polymer, epoxy resins have excellent mechanical, chemical, and thermal properties. In particular, since bisphenol-type epoxy has a flexible chemical structure, it has the advantage of being able to impregnate fillers in general. When a metal with high thermal conductivity is used as a filler, it is impossible to apply it to electronic devices requiring insulation due to high electrical conductivity. Therefore, a lot of research has been done on boron nitride (BN) among ceramic materials that have thermal conductivity as high as metal and have insulating properties. In this study, a method for impregnating BN with high thermal conductivity on a polymer was presented. Boron nitride used as a filler. Most of the heat of the thermally conductive polymer composite is transferred by filler. That is, the filler forms a thermal conduction pathway. Simply synthesizing a polymer and a filler can’t improve heat conduction. This is because there are two types of thermal resistance. The resistance between the interface filler and the polymer, and the thermal resistance of the contact filler. The weak interfacial adhesion between the filler and the polymer results in a large interfacial thermal resistance due to the additional scattering of phonons. Therefore, the surface of the filler material was modified to improve the dispersion of the filler material in the polymer and to strengthen the interfacial interaction. In addition, a method was presented to form a thermal conduction pathway of the filler in the epoxy. The thermal conductivity of the polymer composite was measured using the laser flash apparatus (LFA) method. The surface modified BN will be helpful in the manufacture of thermally conductive polymer composites, and will serve as a necessary filler in the heat dissipation industry.
Recently, electronic devices such as smartphone, tablet PC and portable device are becoming lighter, smaller and more integrated. As a result, the thermal density rapidly increases, which causes deterioration or failure of electronic devices. It has been reported that heat generation of electronic products causes degradation of product performance, and 55 % of failures are caused by heat generation. Accordingly, the demand for high heat dissipation materials is rapidly increasing. A heat dissipation from the inside of the device to the outside is an important technique for preventing malfunction or failure. An electronic device is a finished product heat is assembled from many parts. Adhesives are often used to assemble them, and these adhesives are polymeric resins with very low thermal conductivity. Recently, in order to solve this problem, a composite material made by adding a high thermal conductivity filling material such as a metal, carbon material and ceramic material to a polymer is generally used. It is called thermally conductive polymer composite. Among many polymer, epoxy resins have excellent mechanical, chemical, and thermal properties. In particular, since bisphenol-type epoxy has a flexible chemical structure, it has the advantage of being able to impregnate fillers in general. When a metal with high thermal conductivity is used as a filler, it is impossible to apply it to electronic devices requiring insulation due to high electrical conductivity. Therefore, a lot of research has been done on boron nitride (BN) among ceramic materials that have thermal conductivity as high as metal and have insulating properties. In this study, a method for impregnating BN with high thermal conductivity on a polymer was presented. Boron nitride used as a filler. Most of the heat of the thermally conductive polymer composite is transferred by filler. That is, the filler forms a thermal conduction pathway. Simply synthesizing a polymer and a filler can’t improve heat conduction. This is because there are two types of thermal resistance. The resistance between the interface filler and the polymer, and the thermal resistance of the contact filler. The weak interfacial adhesion between the filler and the polymer results in a large interfacial thermal resistance due to the additional scattering of phonons. Therefore, the surface of the filler material was modified to improve the dispersion of the filler material in the polymer and to strengthen the interfacial interaction. In addition, a method was presented to form a thermal conduction pathway of the filler in the epoxy. The thermal conductivity of the polymer composite was measured using the laser flash apparatus (LFA) method. The surface modified BN will be helpful in the manufacture of thermally conductive polymer composites, and will serve as a necessary filler in the heat dissipation industry.