Flux-coated ball and method for manufacturing same

A flux-coated ball comprising:

• a core part;
• and
• a shell part with which the core part is coated,
• wherein the core part is made of a solder ball or a copper core ball,
• the shell part is made of a flux layer containing at least one selected from the group consisting of an activator and a resin component,
• wherein a thickness of the flux layer is 0.10 μm or more and 2.0 μm or less,
• wherein the thickness of the flux layer is determined by subtracting the diameter of the core part from the diameter of the flux-coated ball and thereafter dividing the result by 2,
• wherein a ball diameter of the solder ball or the copper core ball used in the core part is 30 μm or more and 295 μm or less, and
• wherein the flux-coated ball has an oxide film on surface of the core part, and a thickness of the oxide film measured by the following measurement method is 3 nm or less;
• measurement method of oxide film thickness:
• the flux-coated ball, which is a measurement sample, is ultrasonically cleaned in acetone, and then an Auger electron spectrometer is used to measure the surface of the measurement sample after ultrasonic cleaning under the following analytical conditions, and the oxide film thickness is calculated as a SiO2 equivalent value;
• an acceleration voltage of 10 kV,
• a current value of 10 nA, and
• an analysis diameter of 20 μm.