TWI803486B

These copper particles each comprise: a core part containing copper; and a copper oxide layer formed on the surface of the core part and containing CuO and Cu2O. The condition of Y ≥ 36X - 18 is satisfied where X is the content ratio (mass %) of oxygen contained in a copper particle and Y is the crystallite size (nm) of Cu2O contained in the copper oxide layer. It is also preferable that the value of DC/D50, that is, the ratio of the crystallite size DC (µm) of metallic copper contained in the core part to a volume cumulative particle size D50 (µm) at a cumulative volume of 50 volume % as measured using a laser diffraction/scattering particle size distribution measurement method, is between 0.10 and 0.40 inclusive. In addition, it is also preferable that the oxygen content ratio is between 0.80 mass % and 1.80 mass % inclusive.