Suspension board with circuit and producing method thereof

A method for producing a suspension board with circuit comprising the steps of:

• preparing a metal supporting board;
• forming a base insulating layer including a plurality of first portions disposed at spaced intervals to each other and having a thin thickness and a second portion disposed so as to surround the plurality of first portions and having a thicker thickness than the plurality of first portions at one side in a thickness direction of the metal supporting board;
• forming a conductive layer including a plurality of terminal portions, when projected in the thickness direction, overlapped with the second portion between the plurality of first portions in an arrangement direction of the plurality of first portions at one side in the thickness direction of the base insulating layer;
• by etching the metal supporting board, forming a plurality of first support opening portions passing through in the thickness direction and disposed when projected in the thickness direction, so as to include each of the plurality of first portions;
• by etching the base insulating layer via the plurality of first support opening portions, removing the plurality of first portions to form a plurality of base opening portions passing through in the thickness direction and as a plurality of thin portions, forming a second portion exposed from the plurality of first support opening portions and, when projected in the thickness direction, being continuous to circumferential edge portions of the plurality of base opening portions;
• and
• after forming the plurality of thin portions, by etching the metal supporting board, forming, in the metal supporting board, a plurality of second support opening portions passing through in the thickness direction and, when projected in the thickness direction, overlapped with each of end portions of the plurality of terminal portions in a direction, orthogonal to at least both directions of the thickness direction and the arrangement direction and as a plurality of thick portions, forming, in the base insulating layer, a second portion, when projected in the thickness direction, overlapped with the plurality of second support opening portions.