JPH0828449B2 - Lead frame manufacturing method - Google Patents

Description

TECHNICAL FIELD The present invention relates to a lead frame manufacturing method, and more particularly,
High-precision machining of inner leads.

[Conventional technology]

A lead frame used for mounting a semiconductor device such as an IC or LSI is formed by forming a plate-like body made of a metal material such as an iron-based material or a copper-based material into a desired pattern by pressing or etching.

In recent years, as semiconductor devices have become highly integrated and miniaturized, the width of the inner leads has become extremely narrow, and the spacing between them has become smaller, and even a slight deformation of the inner leads is not allowed. ing.

Therefore, in order to prevent the deformation of the leads, a method of attaching an insulating tape such as polyimide to the inner leads or fixing the inner leads to each other with an ultraviolet curable resin has been proposed.

However, the deformation of the inner leads due to the processing strain (residual stress) generated during the shape processing of the lead frame by the press processing cannot be corrected by these methods.

In order to solve such a problem, a method of stamping a shape in which a connecting piece for connecting the inner leads to each other is left on the end surface of the inner lead and performing a heat treatment for removing residual stress, and then removing the connecting piece Has been proposed (Japanese Patent Publication No. 62-44422).

However, even with this method, as shown in FIG. 3, the connecting piece for connecting the inner leads must be made thin in consideration of the subsequent cutting step, and the material is thin for forming a fine pattern. Since the mechanical strength is low, the connecting piece itself that should have fixed the inner leads is deformed by the tension to the lead frame during the heat treatment (annealing) in the reel state, and the inner leads are also deformed accordingly. It was

In order to solve this inconvenience, for example, heat treatment may be performed in a state where the inner lead and the pad are connected without forming a cavity region, but the inner lead tip is necessary for wire bonding. Since the coining is performed to secure the flat width and there is no portion to absorb the extension of the inner lead caused by this, there is a problem that the position of the pad is changed by the extended inner lead during the heat treatment process. It was

(Problems to be Solved by the Invention) As described above, in the conventional method, since there is no portion that absorbs the extension of the inner leads caused by coining, the position of the pad changes due to the extended inner leads. was there.

The present invention has been made in view of the above circumstances, and an object thereof is to provide a highly accurate and highly reliable lead frame.

[Structure of Invention]

(Means for Solving the Problem) Therefore, in the first aspect of the present invention, after the shape processing is performed in a state where the connecting portion is left at the tip portion of the inner lead, and after coining to make the tip portion of the inner lead thin, In order to absorb the excess part formed by the extension in the coining process,
After forming the concavities and convexities, heat treatment is performed, and thereafter, the connecting portions at the tips of the inner leads are removed to separate them individually.

Further, in the second aspect of the present invention, shape processing is performed in a state where the connecting portion is left at the tip portion of the inner lead, coining is performed to thin the tip portion of the inner lead, and then the extra portion formed by extension in the coining step is performed. In order to absorb the flesh, the inner lead tip surface is pressed down, and after heat treatment is performed to remove internal stress, the inner lead tip is pressed down to include the inner lead tip push-down part. Remove the connecting part of and separate it individually,
Finally, the die pad is pressed down to a predetermined depth.

(Operation) According to the above method, since the inner lead tip is not a thin connecting piece but is firmly connected in a state where the cavity region is unprocessed, the inner lead may be deformed by tension in the longitudinal direction during heat treatment. Moreover, since the extension due to coining is sufficiently absorbed by the formation of the unevenness, it is possible to obtain a lead frame with extremely high accuracy.

Further, according to the second aspect of the present invention, in addition to the above operation, the position of the die pad is further lowered, so that the bonding wire can be short and defects such as short circuit in the semiconductor device can be prevented.

(Example) Hereinafter, an example of the present invention will be described in detail with reference to the drawings.

Example 1 First, as shown in FIG. 1 (a), a strip-shaped material containing copper as a main component was formed from four corners of a lead frame unit, an inner lead 1 (excluding the tip surface) 1, a tie bar 2, of a desired shape. The outer lead 3 is mounted on a die equipped with a die such as a part of the outer lead 3 and is pressed to perform patterning while leaving the tip surface of the inner lead.

Next, a coining process is performed on the tip of the inner lead to form a thin portion.

After that, as shown in FIGS. 1B and 1C, the convex portion T is formed in a part of the region to be the cavity region in order to absorb the extra amount extended by the coining.

After that, heat treatment is performed at 700 to 800 ° C. for 80 minutes to remove the internal stress.

Further, as shown in FIG. 1 (d), the cavity region C is punched out so as to include this convex portion T, the die pad 11 and the inner lead tip are separated, and the die pad 11 and the inner lead tip end face are formed. Patterning is completed.

After that, a lead frame is completed through a plating process and a taping process as required.

The lead frame formed in this manner is highly accurate and highly reliable, without deformation due to elongation of the material or variation in the length of the inner leads.

This lead frame is completed as a semiconductor device through steps such as chip mounting, wire bonding, and resin encapsulation, but because it is well formed with internal stress removed, it is extremely accurate. There is.

Embodiment 2 Next, a second embodiment of the present invention will be described.

In the first embodiment, the extension due to coining is absorbed by forming the convex portion, but in this example, the entire region to be the cavity region is pressed down to absorb the extension due to coining, and then heat treatment is performed. This is characterized in that, when the final die pad and inner lead are separated, this push-down portion is formed so as to be cut off at the inner lead portion, and the die pad portion can be pushed further deeper.

First, as shown in FIG. 2 (a), as in the first embodiment,
A strip-shaped material mainly composed of copper is
Inner lead of desired shape from the corner (excluding the tip surface)
1, the tie bar 2, a part of the outer lead 3 and the like are attached to a die equipped with a punching die, and press working is performed to perform patterning while leaving the leading end surface of the inner lead.

Next, a coining process is performed on the tip of the inner lead to form a thin portion.

After that, as shown in FIGS. 2 (b) and 2 (c), the entire cavity region is pushed down to absorb the extension due to coining in order to absorb the extra amount extended by coining.

After this, in order to remove the internal stress, 700 ~ 800 ℃, 80
Heat treatment for minutes.

Further, as shown in FIG. 2D, the cavity region C is punched out so as to include the depressed portion, and the depressed portion is cut off at the inner lead portion.
And the tip of the inner lead are separated to form the die pad 11 and the end surface of the tip of the inner lead.

Finally, as shown in FIG. 2 (e), the support bar is bent so that the die pad portion can be pushed deeper.

Thereafter, as in the first embodiment, a lead frame is completed by further performing a plating process and a taping process as needed.

The lead frame formed in this manner is highly accurate and highly reliable, without deformation due to elongation of the material or variation in the length of the inner leads.

This lead frame is completed as a semiconductor device through steps such as chip mounting, wire bonding, and resin encapsulation, but because it is well formed with internal stress removed, it is extremely accurate. There is.

Further, since the position of the die pad is lowered, the bonding wire can be short, and defects such as short circuit in the semiconductor device can be prevented.

The position and shape of the through hole are not limited to the embodiment and can be modified as appropriate.

Also, regarding the position and shape of the unevenness and the depressed portion,
The present invention is not limited to the embodiment and can be modified as appropriate.

〔The invention's effect〕

As described above, according to the lead frame manufacturing method of the present invention, shape processing is performed with the connecting portion left at the tip of the inner lead, and after coining, unevenness is formed in order to absorb the excess thickness portion. After forming, heat treatment is performed, and after that, the connecting parts at the tips of the inner leads are removed to separate them individually, so that the inner leads are not deformed by the tension in the longitudinal direction, and the extension due to coining does not occur. Since the irregularities are sufficiently absorbed, it is possible to obtain a lead frame with extremely high accuracy.

[Brief description of drawings]

1 (a) to 1 (d) are manufacturing process diagrams of the lead frame of the first embodiment of the present invention, and FIGS. 2 (a) to 2
FIG. 6E is a manufacturing process diagram of the lead frame of the second embodiment of the present invention, and FIG. 3 is a diagram showing a part of the manufacturing process of the conventional lead frame. 11 …… die pad, 12 …… inner lead, 13 …… tie bar, 14 …… outer lead, 15,16 …… sidebar, 1
7 ... Support bar, T ... Convex part.

Claims (2)

[Claims] 1. A plurality of inner leads radially formed so as to surround a semiconductor chip mounting portion and an outer lead connected to each inner lead, wherein a connecting portion is left at a tip portion of the inner lead. A first forming step of performing shape processing in a closed state, a coining step of thinning the tip portion of the inner lead, and a step of forming unevenness so as to absorb a surplus portion formed by the extension in the coining step. The method is characterized by including a second molding step, a heat treatment step of performing a heat treatment in order to remove internal stress, and a third molding step of removing the connecting portions at the tips of the inner leads and separating them individually. Method of manufacturing lead frame. 2. A plurality of inner leads radially formed so as to surround a semiconductor chip mounting portion, and outer leads connected to the inner leads, wherein a connecting portion is left at a tip portion of the inner lead. A first forming step of performing shape processing in a closed state; a coining step of thinning the tip portion of the inner lead; and an inner lead tip surface for absorbing a surplus portion formed by the extension in the coining step. The second forming step of pressing down the inner side of the inner portion, a heat treatment step of performing a heat treatment to remove internal stress, and a connecting portion of the inner lead tip so as to include the pressing portion of the inner lead tip. Third to remove and separate individually
The method for manufacturing a lead frame, comprising: