Development of porous copper by powder compaction / Siti Athirah Rasid

The development of porous copper (Cu) as a heat sink has actively been researched in recent years due to some concern related to overheating of devices, particularly originated from alloys, towards lightweight, high surface area and a high performance (Hassani et al. 2012). One of the promising manufacturing techniques in producing porous structure is Powder Metallurgy (PM) incorporated with space holder material (SHM). In this study, to obtain porous Cu, three types of SHM which are potassium carbonate (K2CO3); 355-500 μm, natrium chloride (NaCl); 200-300 μm and polymethylmethacrylate (PMMA); 450 μm-1 mm were used together with Cu powder. The usage of SHM is to help in obtaining the required pore size and was used with the composition of 50:50%, 40:60% and 30:70% of volume fraction. The impact of volume fraction of SHM were investigated. The mixtures of Cu powder with different SHM were compacted into a green part with pressure of 2 tonne and 60 seconds holding time. The process continues with sintering in high vacuum tube with different temperature depending on the SHM that was used. After the sintering process, subsequent dissolution process is carried out to remove the SHM with distilled water in between 40 ⁰C- 60 ⁰C. Lastly, the samples were tested by using Heat Conduction Apparatus to obtain the result of thermal conductivity. The result shows that thermal conductivity of the sample is decreased as the volume fraction of SHM is increased. The microstructure of porous Cu was evaluated via SEM. It was observed that K2CO3 as a SHM worked successfully on porous Cu where pore structure developed exhibited open and highly inter-connected rather than NaCl and PMMA as a SHM. The results of the study show that porosity and pore size in the porous Cu give an effect on the performance of thermal conductivity results and successfully improve the problem of overheating at the junction of semiconductor. Other than that, for SHM of K2CO3, three different sizes of particles were used; 355 μm, 355-500 μm and 500 μm. From the study, the observations are the heat flow of the samples increases while the thermal conductivity of the samples decreases with increasing of porosity. In conclusion, it is possible to produce porous Cu through PM technique, with the recommendation of using 50% volume fraction of SHM with particle range size of 355 μm.