Since the 1980s, electronics have moved through a sustained wave of miniaturization. As circuit integration increased, current density and thermal-flux density rose with it, pushing conventional cooling strategies closer to their limits. Once heat accumulation passes a critical threshold, both performance and reliability begin to decline.
That is why packaging materials with both high thermal conductivity and suitable thermal expansion have become so important. The broader industry trend now points toward directional heat flow, multi-material composite structures, and better balance between thermal performance, CTE matching, and mechanical strength.
These changes are not only solving current cooling bottlenecks; they are also enabling more reliable thermal solutions for three-dimensional integrated chips, power modules, and other advanced electronic systems.
Traditional packaging materials include ceramics, plastics, metals, and their alloys. Ceramics such as BeO and AlN offer low thermal expansion and good stability, but processing is difficult and some systems are costly or hazardous. Plastics are light and inexpensive, but their thermal conductivity is poor. Pure metals such as Cu, Ag, and Al conduct heat well, but thermal expansion is often too high. This is why new packaging materials are needed that combine strong heat dissipation with appropriate dimensional stability.
Diamond is one of the hardest natural materials known and also one of the best heat conductors in nature, with thermal conductivity ranging from roughly 200 to 2200 W/(mK). Copper adds high thermal conductivity, strong electrical conductivity, good ductility, and relatively mature manufacturing routes. Together, they form a highly promising composite system for advanced electronic packaging.
Common preparation routes for diamond/copper include powder metallurgy, high-temperature high-pressure processing, melt infiltration, spark plasma sintering, and cold spraying.
This article focuses on Spark Plasma Sintering (SPS).
SPS is an advanced powder-metallurgy process driven by pulsed current. Diamond particles and copper powder are mixed, loaded into a graphite die, rapidly heated, and densified under axial pressure. The process offers very high heating rates, short sintering cycles, and limited grain growth.
At the same time, SPS is highly sensitive to composition. When diamond content rises above roughly 65 vol.%, mass transport becomes more restricted, interfacial thermal stress increases because of the large CTE mismatch, and current distribution becomes less uniform because diamond is electrically insulating. Together, these effects narrow the practical processing window.
The intrinsic non-wetting behavior between diamond and copper creates another key challenge. Weak interfacial bonding raises thermal resistance and limits the final performance of the composite. Current research therefore focuses on two major routes.
Diamond surface functionalization
Coatings and chemical treatments create a transition layer on the diamond surface and improve compatibility with the copper matrix.
Copper matrix alloying
Introducing active elements into the copper matrix can reduce interface energy or form useful interfacial compounds, strengthening bonding and improving heat transport.
Together, these interface-engineering strategies reduce thermal resistance and help balance thermal conductivity with mechanical reliability.
