Heat Dissipation in Epoxy/Amine-Based Gradient Composites with Alumina Particles: A Critical Evaluation of Thermal Conductivity Measurements

Abstract

For the design of the next generation of microelectronic packages, thermal management is one of the key aspects and must be met by the development of polymers with enhanced thermal conductivity. While all polymer classes show a very low thermal conductivity, this shortcoming can be compensated for by the addition of fillers, yielding polymer-based composite materials with high thermal conductivity. The inorganic fillers, however, are often available only in submicron- and micron-scaled dimensions and, consequently, can sediment during the curing reaction of the polymer matrix. In this study, an epoxy/amine resin was filled with nano- and submicron-scaled alumina particles, yielding a gradient composite. It was found that the thermal conductivity according to laser flash analysis of a sliced specimen ranged from 0.25 to 0.45 W·m−1·K−1 at room temperature. If the thermal conductivity of an uncut specimen was measured with a guarded heat flow meter, the ‘averaged’ thermal conductivity was measured to be only 0.25 W·m−1·K−1. Finite element analysis revealed that the heat dissipation through a gradient composite was of intermediate speed in comparison with homogeneous composites exhibiting a non-gradient thermal conductivity of 0.25 and 0.45 W·m−1·K−1.

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

“…Calcium carbonate (structural formula: CaCO 3 ) in a form of white fine-crystalline powder was used as the epoxy adhesive compounds’ modifier [73]. The amount of modifier in the adhesive compound (two weight molecules) was selected based on the literature data [66,67,68,69,70,71] and own tests.…”

“…It is important to mix the additive with the adhesive compound evenly so that it all shows exactly the same properties. The additives that are most often used with adhesive compounds are: fillers, plasticisers, surfactants, and compounds that stabilize the polymers [42,44,50,57,61,62,63,64,65,66]. Moreover, different kinds of fillers have different chemical, mechanical and structural properties.…”

Temperature-Triggered/Switchable Thermal Conductivity of Epoxy Resins

“…This measurement technique reveals the lowest thermal conductivity of the specimens during measurements. Preceded by studies of the thermal conductivity of composites with larger-scaled inorganic fillers, the formation of gradient composites is unlikely to occur in this study because of the exclusive involvement of nanofillers and fast curing times [ 18 ]. While π-π stacking is expected to occur exclusively at temperatures above the glass-transition temperature, the thermal conductivity was measured in a range of temperatures from 30 to 180 °C (in steps of 30 K).…”

“…Two main strategies have been reported for the enhancement of the thermal conductivity of polymers and polymer-based composites; that is, compounding with inorganic particles that exhibit high thermal conductivity (e.g., λ (BN) = 600 W·m −1 ·K −1 [ 17 ] λ (SiO 2 ) = 0.7 W·m −1 ·K −1 [ 18 ]) on the one hand, and blending with organic moieties with a high content of aromatic units capable of forming (crystalline) regions by π-π-stacking on the other [ 19 , 20 , 21 ]. The so-called percolation threshold [ 22 ] has to be considered within both strategies, which commonly results in high degrees of compounding/blending and influences various other macroscopic properties such as the mechanical properties.…”

Thermally enhanced polyolefin composites: fundamentals, progress, challenges, and prospects

“…Moreover, the progress in predicting the thermal conductivity of polymer composites using modeling and simulation is discussed. Furthermore, polyolefin composites and nanocomposites (Figure 1) such as heat exchangers, waste energy recovery, heat dissipation applications, electronic packaging, solar, satellite devices, aerospace applications, renewable energy system, electronics, and Li-ion batteries [1][2][3][4][5][6][7][8][9]. However, the relatively low thermal conductivity of polymers (κ p ) poses a challenge and constitutes a bottleneck towards commercial implementation.…”