JPH1012647A - Manufacture of semiconductor device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for fabricating a semiconductor device which can avoid gate clogging and void generation. SOLUTION: The method for fabricating a semiconductor device includes steps of disposing an assembled lead frame 5 in between lower and upper mold parts 20 and 21 of a metallic mold 22, forcingly introducing molten resin 26 into a cavity 24 from a gate 23 through a sprue 25 defined by the metallic mold, opening the metallic mold parts and removing the lead frame therefrom, and cutting and removing unnecessary portions from the lead frame. In this method, a sheet of tape 15 is applied onto at least a plurality of leads of the lead frame 5. Within the metallic mold parts, the taped leads form one face of the gate 23. After the resin is forcingly introduced in the cavity, the tape is removed so that the tape portion is bent between the leads and a recess resulting from the bent portion also forms part of the gate.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a semiconductor device, and more particularly to a technique effective when applied to a technique for forming a sealing body (package) by transfer molding.

[0002]

2. Description of the Related Art A resin-sealed semiconductor device is known as one of semiconductor devices. In a resin-encapsulated semiconductor device, after preparing a metal lead frame, a semiconductor chip is fixed to a predetermined portion (support plate) of the lead frame, and then the electrodes of the semiconductor chip and the leads of the lead frame are electrically conductive. It is manufactured by connecting with a wire, covering the semiconductor chip, the wire, the inner end portion of the lead, and the like with a sealing body formed by transfer molding, and cutting and removing unnecessary lead frame portions and forming leads. .

[0003] In transfer molding, an assembled lead frame is sandwiched between a lower mold and an upper mold of a mold, and a resin melted from a gate is press-fitted into a cavity formed by the upper and lower molds. Form a stop. Regarding the transfer mold, see, for example, “VLSI Packaging Technology (Lower)” 19 issued by Nikkei BP.
It is described on pages 31 to 40, issued May 15, 1993. This document describes a mechanism in which unfilling occurs in the case of a lower gate.

[0004]

A QFP in which leads protrude from four sides of a quadrangular sealed body (package), respectively.
In the case of (Quad Flat Package), the gate at the time of forming the sealing body is provided at one corner of the quadrangular sealing body formation region. As a result, the size of the gate width (frontage) is limited,
Inflow of the resin into the cavity is hindered, so-called gate clogging may occur, and mold failure (unfill failure) may occur. In other words, the resin to be filled becomes partially semi-cured in a molten state, and is so-called "gelled", so that the narrow and shallow gate portion is clogged with the gel, thereby suppressing the resin from flowing into the cavity. There is.

In addition, since the gate width is small and shallow, the flow rate of the resin flowing into the cavity is high, and the flow rate tends to be different between the lower side and the upper side of the lead frame. Therefore, when the flow of one of the resins is fast, a phenomenon of wrapping around the surface on the opposite side of the lead frame occurs, and voids (bubbles) are generated on the collision surface between the wrapped tip and the tip that has flowed late. The void is relatively large, and in some cases, a defect in which a part of the semiconductor chip or the wire can be visually observed may occur, resulting in poor appearance.

An object of the present invention is to provide a method for manufacturing a semiconductor device in which gate clogging does not occur.

Another object of the present invention is to provide a method of manufacturing a semiconductor device in which voids are less likely to occur.

The above and other objects and novel features of the present invention will become apparent from the description of the present specification and the accompanying drawings.

[0009]

The following is a brief description of an outline of typical inventions disclosed in the present application.

(1) A step of sandwiching the assembled lead frame between the lower mold and the upper mold of the mold, and the step of passing the resin melted from the gate into the cavity through the resin flow path formed by the mold. A method of manufacturing a semiconductor device, comprising: a step of press-fitting, a step of opening the mold and taking out the lead frame, and a step of cutting and removing an unnecessary portion of the lead frame. Along with attaching one tape to the leads so as to cover at least one surface side of the plurality of leads, in the molding die, the tape portion constitutes one surface of a gate extending over the plurality of leads, After press-fitting the resin, the tape is peeled off. The tape portion bends and wraps between the leads, and the recessed portion formed by the wrapping also forms a gate. The width of the gate extends nearly the full width of the cavity. The tape portion extends to the edge of the lead frame and is folded back at the edge to the opposite side of the lead frame.

According to the means (1), since the gate is wide near the width of the cavity, it is possible to prevent the resin from being filled into the cavity.

Also, since the gate is wide near the width of the cavity, the resin is uniformly pressed into the entire width of the cavity, so that it is difficult to make a difference in flow velocity between the top and bottom of the lead frame in the cavity. The generation of large voids due to the collision of the resin on the upper and lower surfaces of the stationary body is eliminated. Therefore, a sealed body having high moisture resistance can be formed.

[0013]

Embodiments of the present invention will be described below in detail with reference to the drawings. In all the drawings for describing the embodiments of the present invention, components having the same functions are denoted by the same reference numerals, and their repeated description will be omitted.

As shown in FIG. 6, a semiconductor device 1 according to the present embodiment has a sealing body (package) 2 having a substantially rectangular parallelepiped appearance and a plurality of leads projecting from four sides around the package 2. It consists of three. The lead 3
Has a so-called gull wing type that bends one step in the middle.

In the method of manufacturing a semiconductor device according to the present embodiment, a lead frame 5 as shown in FIG. 2 is used. The lead frame 5 is made of iron having a thickness of about 0.15 mm.
It has a shape obtained by punching a nickel alloy plate or a copper alloy plate into a desired pattern by pressing. The lead frame 5 has a frame structure formed by a pair of parallel outer frames 6 and a pair of inner frames 7 connecting the pair of outer frames 6 and extending in a direction orthogonal to the outer frames 6. Has become.

A rectangular support plate (tab) 8 is disposed at the center of the frame, and the support plate 8 is supported by a tab suspension lead 9 extending from the center of the inner frame 7. ing. The outer frame 6 and the inner frame 7
The plurality of leads 3 extend from the support plate 8 toward the support plate 8. The lead 3 has a width of, for example, 0.35 mm and a lead pitch of 1.0 mm.

A tie bar 10 is provided substantially in the middle of the frame in parallel with the outer frame 6 and the inner frame 7. The tie bar 10 serves as a reinforcing member for reinforcing each lead 3 and also serves as a dam for preventing resin melted out during transfer molding from flowing out.

The tie bar 10 is not provided on one side of a rectangular lead frame. As will be described later, this is a portion that becomes a gate,
This is because we don't want to have even a few protrusions that could obstruct the flow.

In the manufacture of the semiconductor device, as shown in FIG. 3, a tape 15 is partially adhered to the back side of the lead frame 5. The back surface of the lead frame 5 is shown in FIG.
As shown in FIG. 2, in a mold 22 composed of a lower mold 20 and an upper mold 21, the tape 15 is superimposed on the lower mold 20.
The portion overlaps the gate 23 provided on the lower mold 20. The gate 23 has a wide width approximating the full width of the cavity 24.

On the other hand, by clamping the lower mold 20 and the upper mold 21, a cavity 24 for forming a sealing body, a resin flow path (runner) 25 for guiding the resin melted in the cavity 24, and the like are formed. . The gate 23 is formed at a connection portion between the cavity 24 and the resin channel 25, and serves as a portion for determining the direction of the melted resin 26 or adjusting the flow velocity.

As shown in FIGS. 3 and 4, the tape 15 has a group of leads 3 where no tie bar 10 is provided.
It is pasted all over. This tape 15 is attached over the outer lead 6 and the portion of the outer lead 16 where the package 2 is not formed. The entire portion slightly inside the width portion to which the tape 15 is attached is the gate 23 region. As a result, the gate 23 approximates the full width of the cavity 24.

Further, the tape portion protruding from the outer frame 6 is folded and attached over an intermediate portion of the main surface (upper surface) of the outer frame 6 (a folded attaching portion 17). Folding part 1
7 is compressed when the lead frame 5 is sandwiched between the lower mold 20 and the upper mold 21, and one surface of the lead frame 5 is
It acts to adhere to the parting surface. The end of the folded attachment portion 17 is a peeling end when the tape 15 is peeled off.

As shown in FIG. 5, the tape 15
Between the lead 3 and the lead 3, and is attached to the side surface of each lead 3. As a result, a groove 18 is formed along the lead 3 by the tape 15 between the adjacent leads. This groove 18 forms a part of the gate 23. Therefore, not providing the tie bar 10 between the leads 3 to which the tape 15 is attached does not cause any protruding portion in the gate 23 to be any obstacle. The minimum distance between the tape 15 attached to the lead 3 and the gate portion of the lower mold 20 is, for example, about 0.1 mm.

The tape 15 is made of a heat-resistant resin tape, such as a polyimide resin tape, which can sufficiently withstand the temperature during transfer molding, and is lead-through an adhesive applied to the tape surface in advance so that it can be easily peeled off later. Affixed to frame 5. The thickness of the tape 15 is about 0.1 mm or less.

Next, after preparing the lead frame 5 to which the tape 15 as described above is attached, as shown in FIG. 3, the semiconductor chip 30 is fixed to the main surface of the support plate 8 and the semiconductor chip 30 is fixed. (Not shown) and the tip of the lead 3 are connected by a conductive wire 31.

Next, the assembled lead frame 5
As shown in FIGS. 4 and 5, the resin 26 is clamped to the mold 22, and the melted resin 26 is pressed into the cavity 24 from the gate 23. The gate 23 is provided widely on one side of the cavity 24 having a substantially rectangular parallelepiped shape so as to straddle the plurality of leads 3 and has a width similar to the width of the package 2 to be formed. Since the press-fitting is performed uniformly over the entire width of the cavity 24, even if the melted resin 26 gels, the conventional gate clogging does not occur, and a molding defect (unfilling defect) does not occur.

Further, since the gate width is wide near the width of the cavity 24, the resin 26, which is uniformly melted, flows into the entire width of the cavity 24, so that the flow velocity of the resin is different between the lower side and the upper side of the lead frame 5. Since the vertical flow merges gently at the cavity 24 opposite to the gate 23, unlike the conventional case, the generation of voids due to the collision and merge of the resin on the front and back surfaces of the package 2 does not occur, and the moisture resistance does not occur. The package 2 having high performance can be formed.

FIG. 1 shows the lead frame 5 on the lower mold 20 after molding. Inside the tie bar 10, the package 2 formed of a rectangular parallelepiped is formed, and outside the tape 15,
The cured runner portion resin 35 extends in the resin flow path 25.

Next, the lead frame 5 is taken out from the mold 22 and the tape 1
Peel 5 off. By this peeling, the runner portion cured resin 35 is easily separated from the lead frame 5 and comes off.

Thereafter, although not shown, the tie bar 10 is cut and removed, the leads 3 are cut at the roots of the outer frame 6 and the inner frame 7, and the leads 3 projecting from four sides of the package 2 are formed. Thus, a gull-wing type semiconductor device 1 as shown in FIG. 6 is manufactured.

According to the method of manufacturing a semiconductor device of the present embodiment, the following effects can be obtained.

(1) Since the gate 23 has a width approximating the width of the cavity 24, the melted resin 26 is press-fitted uniformly over the entire width of the cavity 24, so that the melted resin 26 gels. In this case as well, clogging of the gate as in the prior art does not occur, and mold failure (unfilling failure) does not occur. Therefore, the package 2 can be manufactured with a high yield.

(2) Since the gate width is large near the width of the cavity 24, the resin 26, which is uniformly melted, flows into the entire width of the cavity 24, so that there is a difference in the resin flow rate between the lower side and the upper side of the lead frame 5. Since it becomes difficult to achieve this, the vertical flow merges gently at the portion of the cavity 24 opposite to the gate 23. Therefore, unlike the conventional case, the generation of voids caused by the collision of resin on the front and back surfaces of the package 2 does not occur. As a result, the package 2 having high moisture resistance can be manufactured with a high yield.

(3) The tape 15 to be stuck on one surface of the lead frame 5 is folded outside the outer frame 6 and
Is attached over an intermediate portion of the main surface of the main body. As a result, the folded attachment portion 17 is compressed during transfer molding and acts so that one surface of the lead frame 5 is in close contact with the parting surface of the upper die 21, and when the tape 15 is peeled, the peeling when peeling is performed. It is convenient at the end.

(4) The tape 15 bends between the leads 3 and wraps around, and is also attached to the side surface of each lead 3. As a result, a groove 18 along the lead 3 is formed between the adjacent leads by the tape 15. This groove 18 forms a part of the gate 23. Therefore, the gate 23 provided in the lower mold 20 can be made shallower, and the resin cured in the gate 23 and the resin flow path 25 can be separated from the gate 2.
It can be made easier with three parts.

(5) As described above, since the occurrence of poor moisture resistance and poor appearance can be prevented, and the sealing can be performed at a high yield, the manufacturing cost can be reduced.

The invention made by the inventor has been specifically described based on the embodiment. However, the invention is not limited to the above embodiment, and various modifications can be made without departing from the gist of the invention. Needless to say, for example, a tape may be attached to both sides of the lead frame. In this case, the tape portion between the leads may be recessed to form a groove that forms a part of the gate.

[0038]

The effects obtained by the representative ones of the inventions disclosed in the present application will be briefly described as follows.

(1) In transfer molding in the manufacture of a semiconductor device, since the gate is formed so as to have an opening extending over a plurality of leads, unfilled resin can be prevented, and the yield can be improved.

(2) In the transfer molding in the manufacture of a semiconductor device, since the gate is formed so as to have an opening approximating the width of the cavity, the resin can be press-fitted over the entire width of the cavity. It becomes difficult to make a difference between the upper and lower resin flow velocities, so that large voids due to the collision of the resin on the upper and lower surfaces of the sealing body are eliminated, and sealing with high moisture resistance can be achieved. As a result, appearance defects can be prevented, and the yield can be improved.

[Brief description of the drawings]

FIG. 1 is a plan view of a method for manufacturing a semiconductor device according to an embodiment of the present invention in a state where an upper mold after transfer molding is removed.

FIG. 2 is a plan view showing a lead frame used in the method for manufacturing a semiconductor device according to the embodiment.

FIG. 3 is a plan view showing a lead frame to which a tape used in the method of manufacturing a semiconductor device according to the embodiment is attached.

FIG. 4 is a schematic cross-sectional view showing a transfer mold state in the method for manufacturing a semiconductor device of the present embodiment.

FIG. 5 is a schematic enlarged cross-sectional view showing a gate portion in a transfer mold state in the method for manufacturing a semiconductor device of the present embodiment.

FIG. 6 is a front view showing a semiconductor device manufactured by the method for manufacturing a semiconductor device according to the embodiment;

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Semiconductor device, 2 ... Sealed body (package), 3 ... Lead, 5 ... Lead frame, 6 ... Outer frame, 7 ... Inner frame, 8 ... Support plate, 9 ... Tab suspension lead, 10 ... Tie bar, 15 ... Tape, 16: Outer lead, 20: Lower mold, 21: Upper mold, 22: Mold, 23: Gate, 24: Cavity, 25: Resin channel, 26: Melted resin, 30: Semiconductor chip, 31 ... Wire, 35: Runner cured resin.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code Agency reference number FI Technical display location H01L 23/50 H01L 23/50 G Y // B29L 31:34

Claims (4)

[Claims] 1. A step of sandwiching a lead frame after assembly between a lower mold and an upper mold of a mold, and press-fitting a resin melted into a cavity from a gate through a resin flow path formed by the mold. A step of opening the mold and taking out the lead frame; and a step of cutting and removing an unnecessary portion of the lead frame. Attach one tape to the lead so as to cover at least one surface side of the book lead,
A method of manufacturing a semiconductor device, comprising: forming one surface of a gate extending over a plurality of leads at the tape portion in the mold; and peeling the tape after press-fitting a resin. 2. The method of manufacturing a semiconductor device according to claim 1, wherein the tape portion bends and wraps between the leads, and a recess formed by the wrapping also forms a gate. 3. The method of manufacturing a semiconductor device according to claim 1, wherein the width of the gate is almost as large as the width of the cavity. 4. The tape device according to claim 1, wherein the tape portion extends to an edge of the lead frame, and the tape portion is folded back to the opposite side of the lead frame at the edge portion. 13. The method for manufacturing a semiconductor device according to the above item.