## 1 Introduction  
Additive manufacturing (AM) has the potential to be a flexible production method that can be used for the fabrication of personalized products with low weight, tailored mechanical, electrical, thermal, and medicinal properties for numerous applications [1]. For these reasons, AM has gained importance in academic and industrial research in the last 20 years. Among the materials used in AM, metals are still the most important ones [2]. One metal that could benefit from being processed by AM is pure copper. Copper and its alloys have a very high thermal and electrical conductivity, making them good candidates for thermal and electrical management systems [3]. Additionally, copper and its alloys have antibacterial and antiviral properties [4, 5]. Combining these properties with the design freedom that AM brings can result in the possibility of manufacturing efficient heat exchanger devices and complex electrically conductive paths in electronics [3] and fixtures that can prevent the spread of diseases [5]. The most common techniques used for the additive manufacturing of metals are powder bed fusion (PBF) techniques. It has been observed that using PBF with copper is challenging due to its high thermal conductivity, leading to a very high thermal dissipation during processing, which causes residual stresses [6; 7]. Copper also has a high reflectivity to laser light, making selective laser melting (SLM) of pure copper problematic, and is mainly used in copper alloys with lower thermal conductivity and lower reflectivity [3; 7; 8; 9]. This limitation is sometimes overcome by using laser beams with greater power (1000 W). By doing so, densities up to 99.9% from the theoretical can be obtained with SLM [10]. Another possibility is to coat the powder with polymers followed by a debinding and sintering step [11], but the density and purity of the final part can be lower than expected [12]. The fabrication of copper parts by electron beam melting (EBM) works quite well since the absorption and reflection of electrons are different from those of photons [3; 13]. Thus, most of the energy transferred by the electrons is absorbed within the copper particles. The energy deposited is sufficient to consolidate pure copper with very high thermal conductivity (400 W m/K) [3; 14]. The high thermal conductivity of copper requires heating the powder bed to minimize defects caused by the severe thermal energy dissipation during the melting process. However, due to the high sintering activity of copper powder, there is a danger that the loose powder cannot be removed if the pre-heating is conducted at a high temperature or for a very long time [3]. In addition, there is a high capital cost of beam-based AM equipment and the infrastructure needed to handle explosive powders safely. These complexities have led to the development of other binder-based AM processing routes for copper specimen fabrication [7; 11]. Copper parts can be indirectly, additively manufactured by other non-beam methods, such as material jetting (MJT), vat photopolymerization (VPP), binder jetting (BJT) and material extrusion (MEX) [11; 15], followed by the removal of the organic binder and the sintering of the rebound parts. The most common ones are BJT and MEX. Binder Jetting is an AM method where a liquid binding agent is selectively deposited to join particles temporarily. The non-bound powder acts as a support material for overhangs, and it is removed by compressed air. The shaped part is cured for better handling and taken to a sintering furnace where the binder is pyrolyzed and the particles sintered through atomic diffusion [16]. Binder jetting is a scalable process very well suited for lots with numerous small parts with complex geometry. However, as with other powder bed technologies, the flowability of the powder is crucial to achieving geometrical accuracy and low porosity. A good flowability is generally achieved by using larger particles, but smaller particles sinter more easily.