JP2003051575A - Method for forming half etched surface - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a novel method for inexpensively manufacturing a lead frame having no roundness in a sectional shape of half etched surface with high productivity. SOLUTION: The method for forming a half etched surface comprises the steps of press forming a half etched lead distal end by pressing to flatten the surface of the lead distal end, providing two or more holes having a relation of a high positional accuracy to a half etched part in the lead frame before pressing, positioning the lead by using the holes, and flattening the object half etched part with a punch to flatten the half etched part. In this case, the metal die has at least two or more pins for positioning a metal plate in the mold, and the punch assembled to match the pattern shape of the half etched part.

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a surface treatment of a lead frame having a half-etch structure or a metal material subjected to a half-etching process used as a member in a CSP manufacturing process. About the method. [0002] FIG. As shown in FIG. 1, there is a lead frame which has been half-etched at the tip of the inner lead. Such a lead frame is the result of the miniaturization of the semiconductor device, and reduces the thickness of the semiconductor device itself obtained by wire-bonding the tip of the half-etched inner lead to the semiconductor element and sealing it with resin. The purpose is to increase the etching characteristics by reducing the thickness of the sheet, and to process a fine-pitch product. When manufacturing such a lead frame, if the tip of the inner lead is half-etched after the inner lead is formed, the half-etched surface of the tip of the inner lead must be rounded. Even if the inner lead portion is formed and half-etched at the same time, the inner lead portion is rounded. If the roundness is excessive, the bonding strength between the bonded wire and the inner lead becomes low, and there is a problem that only a semiconductor device with low reliability can be obtained. As means for solving such a problem, it has been studied to first form a half-etched portion, provide a resist layer on a half-etched surface, and form a lead portion by etching from a surface opposite to the half-etched surface. .
However, in this method, the number of steps of covering the first half-etched portion with the resist again and etching from the opposite surface is increased, so that the productivity is poor, and a major problem remains in economic efficiency. SUMMARY OF THE INVENTION An object of the present invention is to provide a novel method capable of manufacturing a lead frame having a rounded half-etched surface with no roundness with good productivity and at low cost. In order to solve the above-mentioned problems, the present invention is to press-mold a half-etched lead tip using a press die to flatten the surface of the lead tip. Before press forming, two or more holes that have a high positional accuracy relationship with the half-etched part are provided in the lead frame, positioning is performed using these holes, and the target half-etched part is punched. A press die to be crushed and flattened, the press die to be used is provided with at least two or more pins for positioning a metal plate in the die, and a punch incorporated according to a pattern shape of a half-etched portion. A method for forming a half-etched surface. In the present invention, two or more holes having a high positional accuracy with respect to a half-etched portion are formed in advance by etching or press working, and a die is formed in the hole. Then, the desired half-etched portion is crushed with a punch, and a flat portion is created at the desired location. Here, the positional relationship between the hole of the metal plate and the half-etched portion is designed to be the same as the positional relationship between the pin in the mold and the punch, so that only the target portion can be crushed by the punch. Hereinafter, description will be made with reference to FIG. A lead frame 1 processed into a reel or a sheet having a half-etch structure is conveyed into a mold 3 and the lead frame 1
The positioning is performed by inserting the pilot pin 5 in the mold 3 into two or more holes 4 having a high positional accuracy relationship with the half-etched portion 2 of FIG. The die 3 includes a pilot pin 5 and a punch 6 having the same relationship as the positions of the hole 4 of the lead frame 1 and the half-etched portion 2, and the lead frame 1 positioned and fixed by the pilot pin 5 has a punch 6 Thus, only the target half-etched portion 2 is crushed. The punch 6 can be adjusted in its crushing strength by a spring 7 or a bottom dead center adjusting jig (not shown), and the required flatness is determined in consideration of the material and thickness of the lead frame. Can be secured. The present invention is also effective for flattening a half-etched portion used for electroforming as shown in FIG. 3, and the half-etched portion can be easily flattened by adjusting the punch shape. . Next, the present invention will be further described with reference to examples. (Embodiment 1) FIG. 1 shows that a copper alloy is used as a material metal, and a lead end portion to be wire-bonded at the time of assembling an IC is half-etched in half of the plate thickness and a half-etched surface is rounded. The test was performed using such a lead frame. The lead frame was placed in a press having a mold as shown in FIG. 2, and only the half-etched surface was crushed. The cross-sections of the front and rear ends of the lead were measured by a high-precision length measuring machine. The result is shown in FIG. As can be seen from FIG. 4, a flat surface that can ensure bonding reliability is obtained. According to the present invention, as described above, a half-etched and rounded lead tip is provided with a positioning pin and a punch having the same relation as the positions of the positioning hole of the lead frame and the half-etched portion. The flatness of the tip of the inner lead can be easily and inexpensively improved without performing complicated processing such as etching twice by crushing using a mold having the above. The present invention is also applicable to flattening a half-etched portion used for electroforming.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a view showing a lead frame in which a half-etch is applied only to a portion to be wire-bonded and a cross-sectional shape thereof. FIG. 2 is a view showing a mold used in the present invention and an operation state thereof. FIG. 3 is a diagram showing a metal plate serving as a half-etched mold used for electroforming. FIG. 4 is a diagram showing profile measurement results before and after punching of a half-etched surface. [Description of Signs] 1—Lead frame 2—Lead tip half-etched part 3—Mold 4—Hole 5—Pilot pin 6—Punch 7—Spring

Claims (1)

Claims: 1. A half-etched lead tip is press-formed by a press die to flatten the surface of the lead tip, and the half-etched part is formed before the press-forming. In the lead frame, two or more holes having a high positional accuracy relationship are provided in the lead frame, positioning is performed using these holes, and the target half-etched portion is flattened by crushing with a punch. The press die to be used is provided with at least two or more pins for positioning the metal plate in the die, and a punch incorporated according to the pattern shape of the half-etched portion. Molding method for half-etched surface.