Microstructure and Mechanical Properties of Copper Microtubes Fabricated via the Electroforming Process

In this study, a Cu microtube electroforming process on a plastic mandrel that enables rapid mandrel removal without damage to the tubing is proposed. A square tube with a minimum internal dimension of about 500 μm and a circular tube with a minimum inner diameter of approximately 60 μm were successfully fabricated. The effects of additive type and power source on the microstructure and mechanical properties of the electroformed tubes were also studied. The electroformed Cu microtubes that exhibit and textures had columnar and fibrous grains that aligned well along their growth directions. The -oriented columnar grains were divided by high-density twin boundaries when organic gelatin was added. The use of a commercial cupracid additive suppressed grain growth, which resulted in microtubes with relatively weak textures and equiaxed grains. The tensile test results showed that the addition of gelatin and cupracid and the use of pulsed power increased the strength of the electroformed Cu microtubes. This finding was attributed to small grain size, specific crystallographic textures, and high volume fraction of the twin boundaries. These results showed that the electroformed Cu microtubes can have geometries smaller than the tubes formed with existing metal tubing processes while retaining high strength.