Metal foil for spring member, spring member for electronic device, production method for metal foil for spring member, and production method for spring member for electronic device

A method for manufacturing a metal foil for a spring member used to manufacture the spring member, the method comprising:

• rolling a base material;
• and
• preparing rolled materials obtained by rolling the base material and then selecting the metal foil for the spring member from the rolled materials, wherein
• each of the rolled materials include a first region on which the spring member is formed, the first region having a square shape with one side being 300 mm,
• a difference value between a maximum value and a minimum value of a first thickness at each of points on a straight line in a rolling direction in the first region is a first difference value,
• a difference value between a maximum value and a minimum value of a second thickness at each of points on a straight line in a width direction orthogonal to the rolling direction is a second difference value, and
• the selecting the metal foil for the spring member selects, from the rolled materials, as the metal foil for the spring member, the rolled material in which an absolute value of a difference value obtained by subtracting the second difference value from the first difference value is less than or equal to 0.8 μm.

A method for manufacturing a spring member for an electronic device formed from a metal foil for a spring member, the method comprising:

• forming a resist mask on a front surface and a back surface of the metal foil for the spring member;
• and
• wet-etching the metal foil for the spring member using the resist mask, wherein
• a difference value between a maximum value and a minimum value of a first thickness at each of points on a straight line in a rolling direction of the metal foil for the spring member is a first difference value,
• a difference value between a maximum value and a minimum value of a second thickness at each of points on a straight line in a width direction orthogonal to the rolling direction is a second difference value, and
• an absolute value of a difference value obtained by subtracting the second difference value from the first difference value is less than or equal to 0.8 μm.