When designing heat sinks (especially the copper-based ones), researchers strive for improving the adhesion of binder to diamond because even small imperfections and cavities at the interface, which are inevitable because copper does not wet diamond, may dramatically reduce thermal conductivity.
While mechanical strength of adhesion of binder to diamond can be estimated by measuring the mechanical properties of the binder alone, assessment of adhesion ensured by chemical bonding is a rather challenging task.Īdhesion of diamond to the metal matrix is an important parameter affecting diamond retention capacity in the working layer of the tool, as well as its general performance. When diamond retention capacity is ensured exclusively by mechanical interlocking, the percentage of prematurely lost diamond grains is as high as 80% 16, resulting in significant economic losses. Mechanical interlocking depends on mechanical properties of the material's matrix, and especially on its flexural and compressive strengths. The van der Waals forces are negligibly small. As demonstrated by numerous publications focusing on methods to improve adhesion and searching for efficient ways to produce diamond-based metal matrix composites, adhesion of binder to diamond has always been a pressing problem 10, 11, 12, 13, 14, 15.ĭiamond retention capacity depends on three forces: the van der Waals forces, mechanical interlocking, and chemical bonding. Diamond is applied as a component of a composite material with a metallic, ceramic, or organic matrix (binder) or as layer in coatings deposited on different substrates. Due to its high hardness, thermal conductivity, and low coefficient of thermal expansion, diamond is used as the key component of cutting, drilling, and grinding tools 7 and heat sinks 8, 9. The key advantages of diamond involve such properties as extremely high hardness (ranging from 70 to 200 GPa according to different sources) 1, 2, 3 and thermal conductivity (2200–2600 W/(m K)) 4, 5, 6, which is only inferior to graphene. Diamond is a unique material that exhibits a combination of superior physical, chemical, and mechanical characteristics.