JPH04180661A - Lead frame and manufacture thereof - Google Patents

Abstract

PURPOSE:To obtain a lead frame of small pitches by constituting inner leads in a two-layer structure of a surface and rear layers and positioning the inner leads of each layer between each inner lead of the other layer. CONSTITUTION:Resist films 2 are formed on the surface and rear of a blank metallic plate 1 so that each band of the banded pattern of each film 2 can be positioned between each band of the banded pattern of the other film 2. When the parts without the resist films 2 are etched, the etching progresses and inner leads 3 are separated from each other and, finally, upper inner leads 4 and lower inner leads 5 are formed at small pitches in a two-layer structure. Since outer leads 7 are formed at large pitches in a fan-like form and respectively connected to the inner leads 4 and 5, the leads 7 can be formed by ordinary etching.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a lead frame and a method for manufacturing the same, and more particularly to a lead frame for a semiconductor device by etching and a method for manufacturing the same.

[Conventional technology]

Conventionally, in a method for manufacturing a lead frame for a semiconductor device using this type of etching process, as shown in FIG. By applying the film 2 and etching it from both the front and back sides, the inner leads 6 were formed as shown in FIG. 2(b).

[Problem to be solved by the invention]

In the conventional lead frame manufacturing method described above, only the gaps in the inner leads 6 are etched in order to apply the resist film 2 to both the front and back surfaces of the metal plate 1 of the inner leads 6 to be formed. Therefore, since the adjacent inner leads 6 require a moderate gap between the inner leads 6, there is a drawback that the pitch of the inner leads 6 cannot be set smaller than a certain level.

SUMMARY OF THE INVENTION An object of the present invention is to provide a lead frame in which the pitch of inner leads can be set small, and a method for manufacturing the lead frame.

[Means to solve the problem]

In the present invention, the inner leads are formed in a two-layer structure on both the front and back surfaces, and the inner leads of each layer are located between the inner leads of the other layer.

The method for manufacturing a lead frame of the present invention includes forming a resist film in a striped pattern on both the front and back sides of a metal plate as a material, such that the striped pattern is located between the striped patterns on the other side. The method includes steps of forming inner leads having a two-layer structure by half-etching.

〔Example〕

Next, embodiments of the present invention will be described with reference to the drawings.

FIGS. 1(a) to 1(c) are perspective views showing the order of steps for explaining a manufacturing method according to an embodiment of the present invention.

First, as shown in FIG. 1(a), a resist film 2 is formed on each of the front and back surfaces of a raw metal plate 1 in a striped pattern such that the striped patterns are located in the middle of each other.

Next, as shown in FIG. 1(b), it is immersed in an etching solution to half-etch the portions where the resist film 2 is not present on both the front and back surfaces. At this time, the etched area is etched with a slightly bulging rectangular cross section.

As the etching progresses, each inner lead is separated, forming an upper inner lead 4 and a lower inner lead 5, each having a two-layer structure with a small pitch, as shown in FIG. 1(c). outer lead 7
are connected to the upper and lower inner leads 4 and 5, and are fan-shaped and formed at a wide pitch, so that the lead spacing, that is, the gap 8 is large, so that they can be formed by normal etching.

〔Effect of the invention〕

As explained above, the present invention has the effect of making it possible to set the pitch of the inner leads small and reducing the waste of the raw metal plate by forming the inner leads with a two-layer structure located in the middle of each lead.

[Brief explanation of drawings]

FIGS. 1(a) to (c) are perspective views showing the manufacturing method according to an embodiment of the present invention in the order of steps, and FIGS. 2(a) and (b)
1A and 1B are cross-sectional views showing the steps of a conventional lead frame manufacturing method. l...Material metal plate, 2...Resist film, 3...Inner lead, 4...Upper inner lead, 5...Lower inner lead, 6...Inner lead, 7... Outer lead, 8...Gap.

Claims (1)

[Claims] 1. The inner lead is formed in a two-layer structure on both the front and back surfaces,
A lead frame characterized in that the inner leads of each layer are located between inner leads of other layers. 2. By forming a resist film in a striped pattern on both the front and back sides of the raw metal plate so that the striped pattern is located between the striped patterns on the other side, and half-etching, 2. A method for manufacturing a lead frame, comprising the step of forming an inner lead having a layered structure.