Abstract
The objective of this work is the enhancement of metal-to-metal bonding to provide high thermal conductivity together with electrical insulation, to be used as heat sinks at room and cryogenic temperatures. High thermal conductive metal (copper) and epoxy resin (Stycast 2850FT) were used in this study, with the latter also providing the required electrical insulation. The copper surface was irradiated with laser to induce micro- and nano-patterned structures that result in an improvement of the adhesion between the epoxy and the copper. Thus, copper-to-copper bonding strength was characterized by means of mechanical tensile shear tests. The effect of the laser processing on the thermal conductivity properties of the Cu/epoxy/Cu joint at different temperatures, from 10 to 300 K, is also reported. Using adequate laser parameters, it is possible to obtain high bonding strength values limited by cohesive epoxy fracture, together with good thermal conductivity at ambient and cryogenic temperatures.
Highlights
The adhesion between epoxy resin and metals is of great relevance in diverse industry sectors, such as automotive, aerospace, energy, and electronics [1,2,3]
The effect of laser irradiation on copper surfaces on the mechanical and thermal resistance of Cu/epoxy/Cu has been analyzed in this work
No significant time evolution has been found in the epoxy wettability nor in the mechanical properties of the Cu/epoxy/Cu joints prepared with laser-irradiated copper, in the time interval from a few minutes to about 22 days of this study
Summary
The adhesion between epoxy resin and metals is of great relevance in diverse industry sectors, such as automotive, aerospace, energy, and electronics [1,2,3]. In the case of copper, these consist of removing first the native oxides and organic contaminants (by immersion in concentrated hydrochloric acid solution, for example) and exposing the surface to some oxidation agents (for example alkaline solutions, such as sodium chlorite and sodium hydroxide solution) at temperatures of 70–95 ◦C during a few minutes [4,5]. This method, widely used in electronics, results in the formation of the so-called black and red oxides on the metal surface. The use of aggressive agents in chemical treatments may create a large volume of hazardous and contaminant wastes that can negatively affect natural environment and human health
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