JP2708342B2 - Lead frame - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lead frame used for assembling a surface mount type semiconductor device.

[0002]

2. Description of the Related Art In a semiconductor manufacturing process, a semiconductor element incorporated in a lead frame is sealed with an epoxy resin or the like in a molding process. In this molding process, the lead frame may be warped or may be deformed due to the difference in thermal expansion coefficient between the sealing resin and the metal lead frame when the sealing resin cures and shrinks and returns to room temperature after molding. It is known that a residual stress is generated in the steel.

[0003] In order to prevent such warpage of the lead frame and residual stress in the molded portion, for example, a lead frame described in Japanese Patent Publication No. 62-17381 has been proposed. In this lead frame, as shown in FIG. 3, along the respective sides of the die pad 1 to which the semiconductor element is die-bonded, the intermediate portions of the lead terminals 2 arranged side by side are connected by tie bars 3, and each lead is connected. A gap 6 is provided between the connecting member 4 for connecting the leading ends of the terminals 2 and the outer frame 5, and the lead terminals 2 separated from the outer frame 5 are supported by the supporting pieces 7. Guide holes 8 serving as references for positioning the lead frame during the manufacturing process are provided at a constant pitch on the side in the longitudinal direction of the lead frame.

According to the above-described lead frame, when an external force is applied to the lead terminal 2 due to the curing shrinkage of the sealing resin or the stress caused by the difference in the thermal expansion coefficient between the sealing resin and the lead frame, the support pieces 7 and Since the lead terminals 2 are deformed following the deformation and the outer frame 5 is not deformed, the warpage of the lead frame and the residual stress of the molded portion can be reduced.

[0005]

A mold for molding the mold portion 9 indicated by a chain line in FIG. 3 is provided with a resin in a cavity (cavity) in the mold corresponding to the mold portion 9. A gate 10 for implantation is provided. Therefore, at the time of molding, the mold portion 9 is
It is thermoset in the form of being connected to the resin of the part. for that reason,
When the sealing resin cures and shrinks, the mold portion 9 is not uniformly shrunk and displaced toward its center, but is slightly displaced toward the gate 10. In other words, the mold 9 and the group of lead terminals 2 derived from the mold 9 are gate 1
Since they are displaced toward the zero side, the positional relationship between them and the guide holes 8 is slightly shifted. Such displacement of the mold portion 9 and the group of the lead terminals 2 is not always constant, but changes depending on the shape of the mold portion 9, molding conditions, the structure of the gate 10, and the like.

As a result, the following inconvenience is caused in the tie bar cutting step performed after the molding step. That is, in the tie bar cutting step, the dimensions of the molded lead frame are measured, and the dimensions of the cutting die are set based on the measured dimensions. Then, the lead frame is positioned with reference to the guide hole 8 provided on the side of the lead frame, and as shown in FIG. 4A, each cut punch 11 is positioned at the center between the adjacent lead terminals 2, After cutting the tie bar, tie bar residues 3a of the same length remain on both sides of the lead terminal 2. However, as described above, if the group of lead terminals 2 is displaced toward the gate 10 and the amount of displacement is not constant, the positional relationship between the guide holes 8 and the lead terminals 2 is shifted, and therefore, FIG. As shown in (1), the punching position by the cut punch 11 is shifted, a long tie bar residue 3a remains on one side of the lead terminal 2, and the other side is cut off. Although the positional deviation between the above-described lead terminals 2 and the guide hole 8 is slight, in a recent fine-pitch QFP (Quad Flat Package) or the like,
Since the pitch of the lead terminals 2 is extremely small, the above-mentioned positional deviation is a problem that cannot be ignored.

In order to solve the above-mentioned problem, Japanese Patent Application Laid-Open No. 63-217637 proposes a lead frame in which a reference portion having a positioning guide hole is connected to a tie bar and a die pad support. Have been. The lead frame attempts to maintain the positional relationship between the lead terminal portion and the guide hole by displacing the reference portion following the displacement of the lead terminal during molding.

However, since this reference frame has a structure in which the reference portion is cantilevered by a weak tie bar or the like, the reference portion itself is deformed at the time of handling the lead frame in each manufacturing process or at the time of molding. The positional relationship between the guide hole and the lead terminal may be shifted.

The present invention has been made in view of such circumstances, and a lead which can accurately maintain a positional relationship between a positioning guide hole and a lead terminal portion and can accurately position a lead frame. The purpose is to provide a frame.

[0010]

The present invention has the following configuration in order to achieve the above object. That is, the present invention is a lead frame used for assembling a surface mount type semiconductor device, a die pad to which a semiconductor element is fixed, and a lead terminal group arranged side by side along the side of the die pad, A tie bar connecting an intermediate portion of the lead terminal group, a lead terminal connecting portion connecting a base end of the lead terminal group, an outer frame provided around the lead terminal connecting portion with a gap therebetween, and the lead And a support piece for connecting and supporting the terminal connection portion to the outer frame, and
A guide hole for positioning is formed in an inner area of the lead terminal connecting portion.

[0011]

The operation of the present invention is as follows. In the molding process, when stress acts on the lead terminal group due to the curing shrinkage of the mold part or the difference in the thermal expansion coefficient between the sealing resin and the lead frame, the support piece is deformed and follows the displacement of the mold part. And lead terminal group, tie bar,
And the lead terminal connecting portion is displaced. Accordingly, the positioning guide holes formed in the inner region of the lead terminal connecting portion are similarly displaced, so that the positional relationship between the lead terminal group and the tie bar with respect to the guide holes is accurately maintained.

[0012]

An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a partially enlarged plan view of a QFP lead frame according to an embodiment. This lead frame 20
It is formed by punching or etching a metal thin plate having a thickness of 0.1 to 0.15 mm made of an iron-nickel alloy, a Kovar alloy, a copper alloy, or the like. The lead frame 20 is provided with a die pad 21 to which a semiconductor element is die-bonded at the center.
The die pad 21 is supported by support leads 22. Around the die pad 21, a lead terminal 23
Groups are juxtaposed along each side. Each lead terminal 23 group is connected by a tie bar 24 at an intermediate portion thereof, and a base end thereof is connected by a lead terminal connecting portion 25.

Each lead terminal connecting portion 25 is connected to and supported by the outer frame 20a via four support pieces 26 formed in a zigzag shape. The outer frame 20a has a lead frame 2
A guide hole 27 used for positioning the lead frame 20 or the like at the time of plating process 0, die bonding or wire bonding of a semiconductor element. Further, the lead frame 2 is formed in the inner area of each lead terminal connecting portion 25 by a tie bar cutting process after molding.
Other guide holes 28 used for positioning the 0 are respectively formed.

A semiconductor element is die-bonded to the lead frame 20 shown in FIG. 1, a wire bonding is performed between the semiconductor element and the tip of each lead terminal 23, and the semiconductor element is sealed with an epoxy resin or the like. A mold part 30 is formed. In FIG. 1, reference numeral 31 denotes a gate of a molding die for forming the mold portion 31.

When forming the mold portion 30 as described above, an external force is applied to the lead terminals 23 by stress caused by the curing shrinkage of the sealing resin and the difference in thermal expansion coefficient between the sealing resin and the lead frame 20. 2, the supporting piece 26 interposed between the lead terminal connecting portion 25 and the outer frame 20a is deformed, as shown by a chain line in FIG.
The group is displaced. At this time, the group of lead terminals 23 is displaced integrally with the tie bar 24 and the lead terminal connecting portion 25. Therefore, even if the group of lead terminals 23 is displaced, the guide holes 28 formed in the area inside the lead terminal connecting portion 25 are formed.
And the positional relationship with the group of lead terminals 23 is unchanged. In the tie bar cutting step performed after the molding step, the positioning of the lead frame 20 is performed by inserting a positioning pin of a cutting die (not shown) into the guide hole 28 of the lead terminal connecting portion 25, and the tie bar 24 is cut and removed. . Since the positional relationship between the guide hole 28 and the lead terminal group 23 remains unchanged regardless of the displacement of the lead terminal group 23 during molding, the tie bar 24 can be cut and removed with high precision.

In the above-described embodiment, a lead frame for a QFP has been described as an example. However, the present invention is also applicable to a lead frame for a flat package in which lead terminals are led out from two opposing side surfaces of a molded part. Can be applied.

The guide hole 28 in which the lead terminal connecting portion 25 is formed is not limited to a round hole as in the embodiment, but may be, for example, a long hole or a rectangular hole. Further, a supporting piece 26 for connecting the lead terminal connecting portion 25 and the outer frame 20a is provided.
Any shape may be used as long as it can be deformed by the stress applied during molding, and its shape can be variously changed.

[0018]

As is apparent from the above description, according to the present invention, since the positioning guide holes are formed in the inner region of the lead terminal connecting portion for connecting the base end portions of the lead terminal group, the guide holes are formed during molding. When the lead terminal group is displaced, the guide hole is also displaced accordingly. Therefore, the positional relationship between the lead terminal group and the tie bar with respect to the guide hole is accurately maintained. By positioning the lead frame with reference to the guide hole, it is possible to perform lead frame processing such as tie bar cutting with extremely high precision. .

Further, since the lead terminal connecting portion in which the guide hole is formed is connected and supported by the lead terminal group and the support pieces, it is less likely to be deformed during the handling of the lead frame, and the handling of the lead frame is facilitated. .

[Brief description of the drawings]

FIG. 1 is a partially enlarged plan view of a QFP lead frame according to an embodiment.

FIG. 2 is an enlarged view of a main part of the lead frame according to the embodiment.

FIG. 3 is a partially enlarged plan view of a lead frame according to a conventional example.

FIG. 4 is a diagram provided to explain a problem of a conventional example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 20 ... Lead frame 20a ... Outer frame 21 ... Die pad 23 ... Lead terminal 24 ... Tie bar 25 ... Lead terminal connection part 26 ... Support piece 28 ... Guide hole

Claims (1)

(57) [Claims] 1. A lead frame used for assembling a surface mount type semiconductor device, comprising: a die pad to which a semiconductor element is fixed; a lead terminal group arranged side by side along the side of the die pad; A tie bar connecting an intermediate portion of the lead terminal group; a lead terminal connecting portion connecting a base end of the lead terminal group; an outer frame provided around the lead terminal connecting portion with a gap therebetween; And a support piece for connecting and supporting a connecting portion to the outer frame, and a guide hole for positioning is formed in a region inside the lead terminal connecting portion.