The conductive fine particles according to the present invention each have: a core particle containing an acrylic resin; and a silver layer provided directly on the surface of the core particle directly or provided on the surface of the core particle via a nickel layer, wherein the surface coverage rate of the silver layer is 70% or higher.

Particles that can suppress the occurrence of cracking or peeling during a thermal cycle in a connection part that connects two members to be connected, further can suppress the variation in thickness in the connection part, and can increase the connection strength are provided. The particles according to the present invention are particles used to obtain a connecting material for forming a connection part that connects two members to be connected, and the particles are used for forming the connection part such that thickness of the connection part after connection is twice or less the average particle diameter of the particles before connection, or the particles have an average particle diameter of 1 µm or more and 300 µm or less, the particles have a 10% K value of 30 N/mm² or more and 3000 N/mm² or less, and the particles have a particle diameter CV value of 10% or less.

Provided is a copper powder which can be suitably utilized in applications such as an electrically conductive paste and an electromagnetic wave shield while securing excellent electrical conductivity by increasing the number of contact points between the copper powders. A copper powder 1 according to the present invention has a dendritic shape having a linearly grown main stem 2 and a plurality of branches 3 separated from the main stem 2, the main stem 2 and the branches 3 are constituted as flat plate-shaped copper particles having a cross-sectional average thickness of from 0.02 µm to 5.0 µm to be determined by scanning electron microscopic SEM observation gather, the average particle diameter D50 of the copper powder 1 is from 1.0 µm to 100 µm, and the maximum height in the vertical direction with respect to the flat plate-shaped surface of the copper particles is 1/10 or less with respect to the maximum length in the horizontal direction of the flat plate-shaped surface of the copper particles.

Provided is a silver-coated copper powder that has a dendritic shape, that ensures excellent conductivity as a result of having an increased number of points of contact when silver-coated dendritic copper particles are in contact, that prevents aggregation, and that can be suitably used in a conductive paste, an electromagnetic wave shield, or the like. The silver-coated copper powder comprises amassed dendritic copper particles 1 having a linearly grown main trunk 2 and a plurality of branches 3 branching from the main trunk 2. The surface of the copper particles 1 is coated with silver. The main trunk 2 and the branches 3 of the copper particles 1 have a flat plate shape in which the average cross-sectional thickness is more than 1.0 µm but no more than 5.0 µm. The silver-coated copper powder has a flat plate shape configured from a layered structure of one layer or a plurality of stacked layers. The average particle size (D50) is 1.0-100 µm.

[Problem] To provide a copper electroconductive film formed on a paper substrate, the copper electroconductive film being considerably improved in weather resistance and electroconductivity.

[Solution] The problem can be achieved by an electroconductive film formed by pressing a sintered electroconductive film formed by sintering copper particles in a coating film containing copper powder on a paper substrate along with the substrate, the electroconductive film having an area ratio of copper occupying on a cross section of the electroconductive film in parallel to a thickness direction thereof of 82.0% or more. The electroconductive film can be produced by pressing, for example, by roll press to from 90 to 190°C, after light sintering.

In the drill, each of the thinning edges (6B) extends beyond an intersection point with the chisel (9); an axial rake angle of each of the thinning edges is in a range of +5° to +15°; and a ratio of a length of each of the thinning edges (6B) to a length of each of the cutting edges (6) in a direction, in which the main cutting edge (6A) extends as viewed from the front side of the axial direction (O), is in a range of 20% to 50%. Intersecting ridges (L) between: second thinning wall surfaces (7B) facing an opposite side of the drill rotation direction (T); and the tip flank faces (4), are disposed in such a way that: they are spaced apart in a direction orthogonal to the intersecting ridges (L) as viewed from the front side of the axis (O) direction; they are positioned on one diameter line passing the axis (O); or they mutually pass over in a passing over amount of 0.03×D or less with respect to a diameter (D) of the cutting edges (6) in the direction orthogonal the intersecting ridges (L) beyond the one diameter line.