Byung-Seung Yim

Dispersion, hybrid interconnection and heat dissipation properties of functionalized carbon nanotubes in epoxy composites for electrically conductive adhesives (ECAs)

Different types of MWNTs/epoxy composites were prepared with diglycidyl ether of bisphenol F (DGEBF) and bisphenol A (DGEBA) used as epoxy resins. MWNTs were functionalized to enhance the properties of epoxy composites by treatment with strong acids (acid-treated MWNTs, a-MWNTs) followed by m-phenylenediamine grafting (amine grafted MWNTs, m-MWNTs). Raw, a-, and m-MWNTs were dispersed in DGEBF or DGEBA to a concentration of 1 wt.%. X-ray photoelectron spectroscopy and thermogravimetric analysis verified the effectiveness of acid treatment and confirmed the amine-functionalization of the MWNTs. Scanning electron microscopy of the fracture surface of the epoxy matrix showed that chemical functionalization improves compatibility between the epoxy and MWNTs. Good dispersion of MWNTs leads to the improvement in coalescence and pull strength in the quad flat package (QFP) test. Further, the thermal conductivity of MWNTs/epoxy composites was higher than that of pure epoxy resins. In particular, the m-MWNT/epoxy composite has the best heat dissipation properties, due to the formation of an effective network for heat flow.

Characteristics of solderable electrically conductive adhesives (ECAs) for electronic packaging

Abstract This study investigated the effect of the viscosity of the ECAs using a low-melting-point alloy (LMPA) filler on its bonding characteristics. The curing behaviors of the ECAs were determined using Differential Scanning Calorimetry (DSC), and ECA temperature-dependant viscosity characteristics were observed using a torsional parallel rheometer. The wetting test was conducted to investigate the reduction capability of ECAs and the flow-coalescence-wetting behavior of the LMPAs in ECAs. Electrical and mechanical properties were determined and compared to those with commercial ECAs and eutectic tin/lead (Sn/Pb) solder. In the metallurgically interconnected Quad Flat Package (QFP) joint, a typical scallop-type Cu–Sn intermetallic compound (IMC) layer formed at the upper SnBi/Cu interface after curing process. On the other hand, a (Cu, Ni)6Sn5 IMC layer formed on the SnBi/ENIG interface. In addition, the fracture surface exhibited by cleavage fracture mode and the fracture was propagated along the Cu–Sn IMC/SnBi interface. The extremely low-level viscosity of ECAs had a significant influence on the flow-coalescence-wetting behavior of the LMPAs in ECAs and also on the interconnection properties. Stable interconnected assemblies showed good electrical and mechanical properties.

Mechanical and wetting properties of epoxy resins: Amine-containing epoxy-terminated siloxane oligomer with or without reductant

Abstract The mechanical and wetting properties of the diglycidyl ethers of bisphenol A (DGEBA) and bisphenol F (DGEBF) with epoxy-terminated siloxane oligomers (ETSO) were investigated to examine their durabilities as anisotropic conductive adhesive (ACA) resins. The mechanical properties were improved by decreasing the ETSO content due to the high cross-linking density resulting from the short-chain length of ETSO–diaminodiphenylmethane (DDM). To obtain good wettability in both systems, a short-chain reductant (butanoic acid, BA) was added. DGEBF produced enhancement in the wetting angle compared to that of DGEBA due to its low viscosity. DGEBF can be considered an eco-friendly material in this process since it does not require the use of other chemicals, such as a diluent. Therefore, DGEBF/ETSO–DDM with reductant constitutes a suitable system for favorable environmental processing.

Influence of functionalized graphene on the electrical, mechanical, and thermal properties of solderable isotropic conductive adhesives

Graphene nanosheets have attracted considerable attention as ideal reinforcing filler materials for polymer composites due to their superior physical properties. In this paper, to investigate the influence of functionalized graphene on the electrical, mechanical, and thermal properties of solderable isotropic conductive adhesives (SICAs) with low-melting-point alloy, three types of SICAs [without and with graphene oxide (GO) and amine-modified GO (GO-NH2)] were prepared. All SICA assemblies without and with different functionalized graphene sheets showed excellent electrical and mechanical properties due to the formation of uniform and stable metallurgical conduction paths. The epoxy composite with GO sheets showed superior thermal conductivity to the epoxy composite with GO-NH2 sheets. Our results demonstrated that graphene sheets within SICAs do not affect the electrical and mechanical properties of SICA joints, and that GO sheets are more suitable for enhancing the thermal conductivities of polymer composites than GO-NH2 sheets.

Self-interconnection characteristics of hybrid composite with low-melting-point alloy fillers

A novel hybrid composite with low-melting-point alloy fillers was fabricated and characterized through differential scanning calorimeter analysis and viscosity test. Based on the chemo-rheological properties of the hybrid composite, the hybrid interconnection process was determined. The effect of the reduction capability of hybrid composite on the rheology-coalescence-wetting phenomenon of low-melting-point alloy fillers into the hybrid composite was investigated. The hybrid composite has a low viscosity and did not show excessive curing around the melting point of the used low-melting-point alloy material. The low-viscosity characteristic of hybrid composite and the loading of reductant accelerated rheology-coalescence-wetting phenomenon of low-melting-point alloy fillers in hybrid composite significantly. X-ray image and cross-section view revealed a stable metallurgical interconnection between upper and corresponding lower electrode in hybrid composite with reduction capability. This stable metallurgical interconnection was reflected in much improved mechanical and electrical properties of the hybrid interconnection.

Three-dimensional multi-layer through-hole filling properties of solderable polymer composites with low-melting-point alloy fillers

A novel three-dimensional (3D) multi-layer through-hole filling process using solderable polymer composites (SPCs) was developed to overcome several limitations of the conventional 3D package technique. To investigate the multi-layer through-hole filling properties of SPCs, SPCs with functionalized polymer composite and low-melting-point-alloy (LMPA) fillers were formulated, and a multi-layer through-hole filling test was conducted under atmospheric pressure and decompression reflow conditions. The results indicated that the multi-layer through-hole filling assemblies under the atmospheric pressure reflow condition have weak through-hole filling and interlayer interconnection properties because of the weak elimination of residual polymer composite and voids within the through-hole. Meanwhile, the multi-layer through-hole filling assemblies reflowed under the decompression condition showed improved through-hole filling properties because of the favorable elimination of polymer composite and voids within the through-hole and the excellent wetting behavior of molten fillers. The corresponding electrodes between the stacked boards were electrically interconnected by the proper selective wetting behavior of molten LMPA, and the spaces between stacked boards were underfilled by the cured polymer composite.

ACF COB Bonding Process using Thermosonic

. ACF에 의한 도전은 구동소자와 패널의 전극 사이에 공급된 ACF에 열과 압력을 가함으로써 바인더 내부의 도전 입자들이 물리적 접촉에 의해 도전 경로를 형성하는 방식으로 이루어진다. 현재 ACF의 접합은 압력과 온도를 주요 접합 인자로 하는 열 압착 방식(Thermo-compression bonding: TCB)이 적용되고 있으며 칩과 기판 간의 강한 접합을 얻기 위하여 높은 하중 및 온도, 그리고 긴 공정시간을 필요로 한다. 이와 같이 TCB방식에 의해 전자디바이스에 가해지는 과도한 열 및 압력은 접합계면에 대한 열응력을 발생시켜 접합 신뢰성에 악영향을 일으키며 전자 디바이스에 대한 손상을 발생시킬 수 있다

Electrically Conductive Adhesive using Low-melting-point Alloy and Bonding Process using Them

LMPA를 포함하는 ECA는 기판과 칩 사이에 도포되고, 기판과 칩은 대향하는 전극에 대하여 정렬된다. 정렬이 완료된 ECA에 대하여 열을 가하게 되면 폴리머 매트릭스의 화학적 반응으로 인하여 점성이 천천히 낮아지게 되고 온도가 LMPA의 녹는점에 이르게 되면 LMPA는 용융된다. 상하부 단자간의 높이 변화에 의해 폴리머 매트릭스 내부에서 유동이 발생되고 이 유동은 용융된 LMPA의 유동에 대한 추진력으로 작용하게 된다. 유동중의 접촉에 의하여 주변의 용융된 LMPA와 결합하며 액상수지에 의한 외압과 용융 합금고유의 표면장력에 의해 거대한 구상필러로 성장한 LMPA는 상하부 기판에 형성된 전극(Electrode)에 대한 뛰어난 젖음거동을 일으켜 전도 패스를 형성하게 된다. 가열온도가 폴리머 매트릭스의 경화온도에 이르게 되면 수지성분의 경화에 의하여 대향하는 단자를 고착시키며, 인접 전도 패스 간의 절연성도 확보하게 된다. 접합 공정 동안에 요구되는 사항은 용융필러가 젖음(Wetting)과 융합(Coalescence)을 하는 동안 폴리머 매트릭스가 낮은 점성을 가져야 한다는 점과 폴리머의 환원특성에 의하여 필러 표면의 산화막이 제거 되어야 한다는 점이다. 폴리머가 높은 점성을 갖게 되면 용융필러의 유동을 방해하게 되고, 필러입자의 표면에 산화막이 남아있게 되면 융합과 젖음을 방해하는 요인으로 작용하게 된다