Material Applications and Machining Challenges
Cu/diamond composites combine the excellent thermal conductivity of copper with the extremely low coefficient of thermal expansion of diamond. This combination makes them highly suitable for high-performance electronic packaging, power module thermal management, and advanced heat-spreading substrates.
From a machining perspective, however, Cu/diamond is a typical multiphase material with a significant hardness mismatch. The copper matrix is relatively soft, while the diamond reinforcement particles are extremely hard and wear resistant. During plane grinding, these two phases respond differently to abrasive action, which can affect surface flatness, roughness, and material removal efficiency.
The high hardness of diamond particles may also lead to accelerated abrasive wear, surface scratches, particle protrusion, localized pullout, and non-uniform removal between the copper matrix and diamond particles. These factors make high-quality planarization particularly challenging.
Plane Grinding Process Approach
The study used a plane grinding method based on an cast-iron lapping plate and diamond micropowder abrasives.
A cast-iron plate provides good wear resistance, rigidity, and abrasive-retention capability, creating a stable working environment for diamond abrasives. Diamond micropowder, due to its high hardness, is capable of removing both the copper matrix and the diamond reinforcement particles.
The experimental work focused on three key process variables:
Lapping Plate Rotational Speed
The rotational speed of the lapping plate directly determines the relative velocity between the abrasives and the workpiece surface. Changes in speed influence the cutting and sliding behavior of abrasive particles, thereby affecting both material removal rate and surface morphology.
A proper increase in rotational speed can strengthen abrasive action per unit time and improve machining efficiency. However, excessive or unsuitable speed may increase frictional heat, destabilize abrasive motion, or raise the risk of surface damage. Therefore, plate speed must be optimized to balance removal efficiency and surface quality.
Grinding Pressure
Grinding pressure determines the extent to which abrasive particles penetrate the workpiece surface and is a major factor governing material removal behavior.
At low pressure, the abrasives may not interact effectively with the hard diamond particles, resulting in limited removal efficiency. As pressure increases, abrasive indentation and micro-cutting action become stronger, which can improve material removal rate. However, excessive pressure may intensify surface damage and cause uneven local removal between the copper matrix and diamond particles.
For this reason, pressure selection must account for the coordinated removal requirements of both the soft and hard phases within the composite.
Diamond Abrasive Grit Size
Diamond abrasive grit size has a significant effect on surface roughness, scratch characteristics, and material removal rate.
Coarser diamond abrasives provide stronger cutting capability and are generally more suitable for high-efficiency stock removal during the initial processing stage. However, they may leave deeper scratches and increase the risk of damage around particle boundaries. Finer diamond abrasives are more effective in improving surface finish and reducing roughness, making them better suited for fine grinding or surface preparation before polishing.In practical production, a staged grinding strategy from coarse to fine abrasives can be adopted. The initial stage focuses on removal efficiency, while the later stage focuses on reducing roughness and improving surface flatness.
Relationship Between Process Parameters, Surface Quality, and Removal Rate
The research established a process parameter–surface quality–material removal rate relationship for plane grinding of Cu/diamond composites.
This relationship demonstrates that successful grinding of Cu/diamond does not simply rely on increasing speed, pressure, or abrasive size. Instead, process conditions must be selected comprehensively according to the machining stage and quality requirements.
During rough processing, the primary objective is stable and efficient material removal. Appropriate combinations of plate speed, grinding pressure, and abrasive grit size are required to achieve this objective. During fine processing, greater attention should be given to surface roughness, flatness, and removal uniformity between diamond particles and the copper matrix. More controlled and refined grinding conditions are therefore required.This coordinated parameter optimization approach helps reduce the risk of surface damage, improve process consistency, and create a more reliable surface foundation for subsequent polishing, metallization, coating, or packaging interconnection processes.
Significance for Electronic Packaging Manufacturing
High-quality plane grinding is a critical step for the use of Cu/diamond composites in advanced electronic packaging and thermal management components. Surface defects such as deep scratches, particle protrusion, particle pullout, or localized unevenness may adversely affect the reliability of subsequent metallization, soldering, bonding, and interface joining processes.
By clarifying the effects of lapping plate speed, grinding pressure, and diamond abrasive grit size, manufacturers can define a more effective process window and achieve a balance between high material removal efficiency and high-quality surface planarization.The study provides both experimental and theoretical support for the development of plane grinding processes for Cu/diamond composites. It also offers valuable guidance for the broader application of high-thermal-conductivity composite materials in advanced electronic packaging.