| 摘要 |
PURPOSE:To increase inner leads without enlarging a lead frame, by forming inner lead intervals in patterns to be transcribed on both resist layers put on the front and back surfaces of a conductive plate so that they become larger on the side of the back surface to form narrow leads there. CONSTITUTION:Negative-type photo resists 42 are formed in their similar thickness on the front and back surfaces of a 42-alloy plate 40. A front plate 44 having windows 45, and a back plate 48 having windows 49 are closely attached to the resists 42, to form masks by exposure developing. When both surfaces are etched by using FeCl3 solution, inner leads 60 are formed so as to be inserted between resists 52 and 54. Then, undercuts 56 and 58 are generated on the width-directional end parts of respective upper and lower ends in the inner leads. Width between the front surface 62 and the back surface 64 in the inner lead 60 is smaller than that between the resists 52 and 54. With the resists being dissolved and removed, rinsing and drying processes are performed for completion. Because intervals between leads become large, the lead terminals can be increased without enlarging the lead frame. |
