Session: 04-09-01: Design of Engineering Materials

Paper Number: 165365

Composition and Rheological Property of Copper-Based Feedstocks for Metal Injection Molding Targeting Thermal Management Applications 

Metal injection molding (MIM), a transformative manufacturing technique combining plastic injection molding and powder metallurgy, enables high-volume production of intricate metal components with near-net-shape accuracy. While widely applied to ferrous alloys, its adaptation to copper (a critical material for thermal management systems) faces persistent challenges, particularly in the binder system design. The binder must simultaneously ensure moldability during injection, structural stability during debinding, and minimal contamination during sintering, with which the conventional wax-based binder systems struggle to fulfill due to incompatible thermal and rheological properties. Therefore, the design of binder systems for copper-based MIM feedstocks significantly impacts debinding efficiency and sintering performance. Compared to conventional wax-based binders suffering from high residual carbon, insufficient rheological stability, high-temperature liquid phase formation, and inadequate green strength, polyoxymethylene (POM)-based binder systems demonstrate superior advantages in MIM processes as they enable efficient removal via oxalic acid-catalyzed debinding, provide enhanced green strength to maintain structural integrity, reduce defects, and exhibit improved rheological properties. However, research work on POM-based binders for copper MIM remains limited, necessitating further exploration to optimize rheological behaviors and debinding characteristics. In the context, the present study developed a novel POM-based binder system to balance feedstock flowability, debinding efficiency, and sintering quality. Specifically, a multi-phase binder system was designed, comprising POM as the primary binder, polypropylene (PP) as the secondary binder, and additives including PP-MAH-g compatibilizer, paraffin wax (PW) plasticizer, and stearic acid (SA) lubricant. The PP-MAH-g compatibilizer was incorporated to enhance interfacial adhesion between POM and PP phases, while PW and SA for synergistically improving feedstock plasticity and mold release properties. MIM feedstocks with 57 vol.% Cu powder (D₅₀=27μm) were prepared by adjusting POM/PP ratios to investigate compositional effects on processability. Feedstocks were homogenized via twin-screw extruder at 160°C under a shear rate of 20 s⁻¹, followed by granulation to ensure uniform particle size distribution. To quantify debinding kinetics, thermogravimetric analysis (TGA) was performed under nitrogen atmosphere with a heating rate of 10°C/min. Afterwards, rheological properties were systematically evaluated through viscosity-shear rate curves, thermal analysis (TG/DSC), non-Newtonian index (n), and viscous flow activation energy (Eη). The preliminary experimental results indicate that optimized POM-based feedstocks exhibited viscosity <1000 Pa·s at 200°C under shear rates of 10⁻¹ to 10³ s⁻¹, significant shear-thinning behavior (n<0.5), and excellent pseudoplasticity. Moreover, the sintered MIM parts achieved a density of 8.5 g/cm³ (95% relative density) with low carbon residue, demonstrating structural integrity and suitability for high thermal conductivity. In addition, post-sintering microstructure analysis revealed homogeneous grain distribution and minimal porosity, aligning with the density measurements. This work provides a reliable feedstock solution for copper-based MIM products targeting thermal management applications such as electronic devices.

Presenting Author: Can Yang Shenzhen Technology University

Presenting Author Biography: Dr. Can Yang
He received his B.S. and Ph.D in Mechanical Design and Theory from South China University of Technology in 2006 and 2011, respectively. From October 2008 to September 2010, he was working at The Ohio State University, USA as a visiting scholar with Professors Jose M. Castro and Allen Y. Yi. He is currently working at Shenzhen Technology University, with research interests covering advanced manufacturing, intelligent/high-performance material forming process and equipment.

Authors:

Can Yang Shenzhen Technology University
Zhuo Tang Shenzhen Technology University
Yang Shu Shenzhen Technology University
Xiao-Hong Yin Shenzhen Technology University