Thermal Conductive Composites Prepared by Addition of Several Ceramic Fillers to Thermally Cationic Curing Cycloaliphatic Epoxy Resins

Advances on Thermally Conductive Epoxy-Based Composites as Electronic Packaging Underfill Materials-A Review

The integrated circuits industry has been continuously producing microelectronic components with ever higher integration level, packaging density, and power density, which demand more stringent requirements for heat dissipation. Electronic packaging materials are used to pack these microelectronic components together, help to dissipate heat, redistribute stresses, and protect the whole system from the environment. They serve an important role in ensuring the performance and reliability of the electronic devices. Among various packaging materials, epoxy-based underfills are often employed in flip-chip packaging. However, widely used capillary underfill materials suffer from their low thermal conductivity, unable to meet the growing heat dissipation required of next-generation IC chips with much higher power density. Many strategies have been proposed to improve the thermal conductivity of epoxy, but its application as underfill materials with complex performance requirements is still difficult. In fact, optimizing the combined thermal-electrical-mechanical-processing properties of underfill materials for flip-chip packaging remains a great challenge. Herein, state-of-the-art advances that have been made to satisfy the key requirements of capillary underfill materials are reviewed. Based on these studies, the perspectives for designing high-performance underfill materials with novel microstructures in electronic packaging for high-power density electronic devices are provided.

Molecular-Level Investigation of Cycloaliphatic Epoxidised Ionic Liquids as a New Generation of Monomers for Versatile Poly(Ionic Liquids)

Recently, a new generation of polymerised ionic liquids with high thermal stability and good mechanical performances has been designed through novel and versatile cycloaliphatic epoxy-functionalised ionic liquids (CEILs). From these first promising results and unexplored chemical structures in terms of final properties of the PILs, a computational approach based on molecular dynamics simulations has been developed to generate polymer models and predict the thermo–mechanical properties (e.g., glass transition temperature and Young’s modulus) of experimentally investigated CEILs for producing multi-functional polymer materials. Here, a completely reproducible and reliable computational protocol is provided to design, test and tune poly(ionic liquids) based on epoxidised ionic liquid monomers for future multi-functional thermoset polymers.

Fabrication and Enhanced Thermal Conductivity of Boron Nitride and Polyarylene Ether Nitrile Hybrids

Excellent thermal resistance and thermal conductivity are preconditions of materials to be used at elevated temperatures. Herein, boron nitride and polyarylene ether nitrile hybrids (PEN-g-BN) with excellent thermal resistance and thermal conductivity are fabricated. Phthalonitrile-modified BN (BN-CN) is prepared by reacting hydroxylated BN with isophorone diisocyanate (IPDI) and 3-aminophxylphthalonitrile (3-APN), and then characterized by FT-IR, UV-Vis, and X-ray photoelectron spectroscopy (XPS). The obtained BN-CN is introduced to a phthalonitrile end-capped PEN (PEN-Ph) matrix to prepare BN-CN/PEN composites. After curing at 340 °C for 4 h, PEN-g-BN hybrids are fabricated by a self-crosslinking reaction of cyano groups (-CN) from BN-CN and PEN-Ph. The fabricated PEN-g-BN hybrids are confirmed through FT-IR, UV-Vis, SEM and gel content measurements. The PEN-g-BN hybrids demonstrate excellent thermal resistance with their glass transition temperature (T_g) and decomposition temperatures (T_d) being higher than 235 °C and 530 °C, respectively. Additionally, the thermal conductivity of the prepared PEN-g-BN hybrids is up to 0.74 W/(m·k), intensifying competitiveness of PEN-g-BN hybrids for applications at elevated temperatures.

Optimization of Boron Nitride Sphere Loading in Epoxy: Enhanced Thermal Conductivity and Excellent Electrical Insulation

Thermally conductive but electrically insulating materials are highly desirable for thermal management applications in electrical encapsulation and future energy fields, for instance, superconducting magnet insulation in nuclear fusion systems. However, the traditional approaches usually suffer from inefficient and anisotropic enhancement of thermal conductivity or deterioration of electrical insulating property. In this study, using boron nitride sphere (BNS) agglomerated by boron nitride (BN) sheets as fillers, we fabricate a series of epoxy/BNS composites by a new approach, namely gravity-mix, and realize the controllable BNS loading fractions in the wide range of 5-40 wt%. The composites exhibited thermal conductivity of about 765% and enhancement at BNS loading of 40 wt%. The thermal conductivity up to 0.84 W·m^-1·K^-1 at 77 K and 1.66 W·m^-1·K^-1 at 298 K was observed in preservation of a higher dielectric constant and a lower dielectric loss, as expected, because boron nitride is a naturally dielectric material. It is worth noting that the thermal property was almost isotropous on account of the spherical structure of BNS in epoxy. Meanwhile, the reduction of the coefficient of thermal expansion (CTE) was largely reduced, by up to 42.5% at a temperature range of 77-298 K.

The Impact of the Seasoning Conditions on Mechanical Properties of Modified and Unmodified Epoxy Adhesive Compounds

The aim of this study was to analyse the impact of the adhesive samples seasoning conditions (temperature and time) on selected mechanical properties of four epoxy adhesive compounds (two unmodified and two modified ones). The samples were made of Epidian 53 epoxy resin mixed with the two different amine curing agents in appropriate stoichiometric proportions. A filler in the form of calcium carbonate (CaCO₃) powder was used as a modifier. The adhesive compound samples were cured for seven days. Six seasoning variants were used. Four of them were related with the seasoning time at ambient temperature of 24 ± 2 °C for: one month, two months, five months and eight months, respectively. Two other variants were related with seasoning at negative temperature (−10 ± 2 °C) for one month. The last variant (F) also included seasoning at ambient temperature (24 ± 2 °C) for five months right after seasoning in negative temperature. Cured and cylinder-shaped adhesive compound samples were subjected to compressive strength tests (according to the ISO 604 standard). The strength tests were performed using a Zwick/Roell Z150 testing machine. Based on the tests, it was observed that both temperature and time of seasoning influenced the adhesive’s mechanical properties. In the perspective of eight months, these changes were relatively minor for the samples seasoned at ambient temperature. The adhesive samples prepared for the tests were especially sensitive to negative temperature.