JP2001196401A - Resin package forming method for semiconductor device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable a no-read type semiconductor device to be sealed up in a resin package taking advantage of an existing equipment without increase in the cost and producing burrs on the exposed surface of an electrode. SOLUTION: A die pad and an inner lead 67 which serves as an electrode are provided to a lead frame 6, a semiconductor chip is mounted on the die pad, the semiconductor chip is connected to the inner lead 67 with a conductor wire W, a region 68 of the lead frame 6 extending outward from the inner lead 67 is pinched between an upper and a lower dies, 7a and 7b, the semiconductor chip, the conductor wires W, and the inner leads 67 are housed in a cavity 70 formed by the dies 7a and 7b, and molding resin is poured into the cavity 70 for the formation of a resin-sealed package by making the under surfaces of the inner leads 67 exposed. The lower mold 7b is provided with a recess 70b whose depth is smaller than the thickness of the lead frame 6.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for forming a resin package in a resin package type semiconductor device. More specifically, for example, QFN (Q
In a non-read (a type in which electrodes do not extend in a lead shape from a resin package) semiconductor device, such as a uad Flat Non-read type semiconductor device,
The present invention relates to a method for forming the resin package.

[0002]

2. Description of the Related Art Conventionally, there is a QFN type semiconductor device as shown in FIG. This semiconductor device 8
Although not clearly shown in the drawing, a plurality of electrodes 82 are formed from the vicinity of four sides of a rectangular die pad 80 toward four directions. And die pad 8
Semiconductor chip 81 and upper surface 8 of electrode 82 mounted on
2a is connected by a conductor wire 83,
The semiconductor chip 81 and the conductor wires 83 are made of the resin package 8
4, and is sealed. In addition, each electrode 8
2, the lower surface 82b of the resin package 84 is exposed at the lower surface 84a, and the exposed lower surface 82b is used as a terminal for external connection.

The resin package 84 in the semiconductor device 8
Is formed by, for example, a transfer molding method. More specifically, as shown in FIG. 14, the components of the semiconductor device 8 are built in a lead frame 85, and the components are housed in a cavity 90 formed by upper and lower molds 9a and 9b. This is performed by injecting a molten resin into the cavity 90. Then, as in the semiconductor device 8 described above, the lower surface 82b of the electrode 82 is formed.
Is exposed from the resin package 84, an upper mold 9a having a recess 90a is used, and the lower mold 9b has a flat surface (cavity forming surface 90b) that defines the cavity 90. Is used. That is, the internal lead 82 ′ serving as the electrode 82
Is formed along the cavity forming surface 90b of the lower mold 9b, the lower surface 8 of the internal lead 82 'is formed.
2b ', and thus the lower surface 82b of the electrode 82 of the semiconductor device 1.
Are exposed on the lower surface 84a of the resin package 84.

[0004]

By the way, at the time of resin molding, the die pad 80 'and the internal lead 82' are not formed.
Is a lead frame 85 as shown in FIG.
And one end 82c 'of the internal lead 82' is a free end. Then, in the mold clamping state by the upper and lower molds 9a and 9b, a region (such as the external lead 86) extending from the internal lead 82 'in the lead frame 85 is sandwiched by the upper and lower molds 9a and 90b. At this time, in order to avoid resin leakage from the cavity 90, it is necessary to hold the lead frame 85 while the external leads 86 and the like are compressed to some extent.
The cavity forming surface 90b of the lower mold 9b is a flat surface. Therefore, only the upper surface 86a of the external lead 86 and the like is compressed by the mold clamping,
One end 82c 'of the free internal lead 82' may slightly float upward. In this case, if the resin is injected into the cavity 90, the resin flows around the rear surface 82b 'of the internal lead 82', and burrs are generated on the rear surface 82b 'of the internal lead 82'. The back surface 82b '(82b) of (82) cannot be exposed on the back surface 84a of the resin package 84. If such a problem occurs, burr processing must be performed by chemical treatment or blast processing, which is disadvantageous in work efficiency.

[0005] Because of such complicated burr processing, a method of suppressing burr generation on the back surface of the electrode has been proposed. As one of them, Japanese Patent Application Laid-Open No. H11-16930 discloses that a sealing sheet is interposed on a lower mold, and the sealing sheet is adhered to a lead frame so that a resin is applied to the back surface of the lead frame (electrode). An invention is disclosed which avoids wraparound and suppresses the generation of burrs. However, in the method described in the above-mentioned publication, not only must a sealing sheet be separately prepared and this sealing sheet be prepared on a lower mold, but also after the resin molding, the sealing sheet adhered to the lead frame. You also need to remove the seat. For this reason, in the method using a sealing sheet, the cost is increased by the amount of the sealing sheet, and the existing equipment alone cannot sufficiently cope with the problem, so that the sealing sheet is prepared on a lower mold and sealed from the lead frame. Since it is necessary to construct a new facility for removing the stop sheet, the cost is also high in this respect.

The present invention has been conceived in view of the above-mentioned circumstances. In forming a resin package on a non-read type semiconductor device, the existing equipment is used to significantly increase the cost. It is an object of the present invention to avoid the generation of burrs on the electrode exposed surface without accompanying.

[0007]

DISCLOSURE OF THE INVENTION In order to solve the above problems, the present invention employs the following technical means. That is, according to the present invention, a semiconductor chip is mounted on the die pad with respect to the lead frame on which the internal lead serving as the die pad and the electrode is formed, and the semiconductor chip and the internal lead are connected via a conductor wire. In an electrically connected state, an upper mold and a lower mold are formed by the upper mold and the lower mold by compressing and sandwiching a region extending further outward from the internal lead in the lead frame. The die pad, the semiconductor chip,
A method for housing the conductor wire and the internal lead, forming a resin package such that a resin is injected into the cavity and a lower surface of the internal lead is exposed,
A method of forming a resin package for a semiconductor device is provided, wherein the lower mold has a concave portion whose depth is smaller than the thickness of the lead frame.

In the above method, when the lead frame is sandwiched between the upper and lower dies, a region extending further outward from the electrode (for example, an external lead, hereinafter simply referred to as a “clamping region”) is compressed. . And in the above method,
A lower mold having a concave portion is used.
For this reason, in a state where the holding region is compressed by the upper and lower molds, not only the upper surface side of the holding region is compressed, but also the lower surface of the internal lead follows the concave portion of the lower mold, and the upper surface of the holding region is compressed. And the underside are both compressed. Therefore, in the above method, since the lower surface of the internal lead extends along the concave portion of the lower mold, even if the resin is injected into the cavity in this state, the resin hardly wraps around the lower surface of the internal lead. . As a result, generation of burrs on the lower surface of the internal lead and, consequently, the lower surface of the electrode of the semiconductor device is avoided.

In addition, the above method only uses a lower mold having a concave portion having a depth smaller than the thickness of the lead frame. Therefore, only by changing the mold, the internal leads (electrodes) can be formed. The formation of burrs on the lower surface of (1) can be avoided. For this reason, it is possible not only to avoid an increase in cost due to the use of the sealing sheet, but also to use the existing resin molding equipment without having to construct a new equipment in carrying out the above method, and in this respect, it is also cost effective. Is advantageous.

In a preferred embodiment, the cavity is formed by a concave portion of the upper mold and a concave portion of the lower mold, and an opening area of the concave portion of the upper mold is equal to that of the lower mold. It is larger than the opening area of the recess.

By the way, if the lead frame is sandwiched between the upper mold and the lower mold having different opening areas, the top of the lead frame (clamping region) and the upper mold are attached to the tip of the internal lead whose free end is on the die pad side. There is a tendency that a force acts on the side of the mold having the end by making a bend on the side closer to the die pad among the contact end of the lower mold and the contact end of the lower mold. Therefore, as in the above method, if the opening area of the upper mold is larger than that of the lower mold,
Since the lower mold side comes into contact with the pinching portion up to a portion closer to the die pad, a force toward the lower mold side acts on the tip of the internal lead. For this reason, since the lower surface of the internal lead is brought into a state of being in close contact with the lower mold,
It is possible to more reliably avoid the resin from reaching the lower surface of the internal lead.

[0012] Other features and advantages of the present invention will become more apparent from the detailed description given below with reference to the accompanying drawings.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be specifically described below with reference to the drawings.

FIG. 1 is an overall perspective view showing an example of a semiconductor device to which a resin package forming method according to the present invention is applied, and FIG. 2 is a cross-sectional view taken along line II-II of FIG.

The semiconductor device 1 shown in FIG. 1 and FIG.
So-called QFN (Quad Flat Non-rea)
d) belongs to the type. That is, the plurality of electrodes 2
Are formed so as to extend between each side of the rectangular die pad 4 and each side of the resin package 3, and each electrode 2 does not extend from the resin package 3 to the outside in a lead shape. The device 1. The semiconductor chip 5 is mounted on the die pad 4, and the electrode pad (not shown) of the semiconductor chip 5 and the upper surface 20 of the electrode 2 are electrically connected via the wire W. I have. The resin package 3 is formed such that the lower surface 21 of the electrode 2 is exposed from the lower surface 30 thereof.
The semiconductor device 1 is mounted on a predetermined target such as a circuit board with the lower surface 21 of the electrode 2 as a connection portion.

The semiconductor device 1 configured as described above
Is manufactured through the steps shown in FIGS. FIG. 3 is a partial perspective view of a lead frame used for manufacturing a semiconductor device, FIG. 4 is a partial perspective view showing a state in which a semiconductor chip is mounted on a die pad in the lead frame of FIG. 3, and FIG. FIG. 6 is a partial perspective view showing a state in which electrode pads of a semiconductor chip are connected to internal leads of a lead frame via wires. FIG. 6 shows components of the semiconductor device in FIG. 5 in a cavity formed by upper and lower dies. 7 is an enlarged sectional view of a main part of FIG. 6, FIG. 8 is a sectional view showing a state in which resin is injected into the cavity shown in FIG. 6, FIG. 9 and FIG.
0 is a sectional view and a partial perspective view showing a state in which upper and lower dies are removed from the state of FIG.

First, as shown in FIG. 3, a lead frame in which necessary components are built is formed. The lead frame 6 includes a pair of side members 6 extending in the longitudinal direction.
0, the space between these side members 60 is connected to the cross member 61, and the formation region 62 of each semiconductor device 1 is defined. Such a semiconductor formation region 6
2 is not clearly shown in the drawing, but the side member 6
A plurality is provided so as to be arranged in the direction in which 0 extends.
In each semiconductor formation region 62, 4 is connected between the side members 60 or between the cross members 61.
Two dam bars 63a and 63b are provided, and a rectangular area 64 is formed by these dam bars 63a and 63b. In the rectangular area 64, a rectangular die pad 66 is supported at four corners via suspension leads 65. Although not clearly shown in FIG. 3, the die pad 66 is offset upward with respect to the dam bars 63a and 63b (see FIG. 6). And each dam bar 63a,
From 63b, the tip 67
A plurality of internal leads 67 extending a are formed side by side in the width direction. These internal leads 67 are parts to be electrodes 2 of the semiconductor device 1 later (see FIGS. 1 and 2). From each dam bar 63a extending in the same direction as the cross member 61, an external lead 68 is formed so as to extend in a direction opposite to the internal lead 76. It should be noted that the side members 60
A positioning hole 60a is provided.

In manufacturing the semiconductor device 1 shown in FIGS. 1 and 2, the die pad 6 is formed as shown in FIG.
The semiconductor chip 5 is mounted on the semiconductor chip 6 in a face-up manner. This operation is achieved by curing the adhesive while an adhesive such as an epoxy resin is interposed between the lower surface of the semiconductor chip 5 and the die pad 66. The semiconductor chip 5 is a bare chip, and a plurality of electrode pads 50 are formed on the upper surface thereof, for example, so as to be arranged along the periphery.

Next, as shown in FIG. 5, the electrode pads 50 of the semiconductor chip 5 and the internal leads 67 are electrically connected via wires W. The conductive connection by the wire W
The first bonding is performed on the electrode pads 50 and the second bonding is performed on the internal leads 67.

The first bonding is a so-called ball bonding, in which a wire protruding from a capillary (not shown) is melted by a hydrogen flame or arc discharge into a ball shape, and the ball is formed into an electrode pad 50. This is done by pressing against

The second bonding is so-called stitch bonding, and the internal leads 67 are used.
Is performed by pressing the capillary downward, moving the capillary toward the base end (outer lead 68) of the inner lead 67, and cutting the wire.

At the time of bonding, ultrasonic waves may be applied to secure the connection between the electrode pad 50 or the internal lead 67 and the wire W, or the lead frame may be heated. Is also good.

Subsequently, as shown in FIGS. 6 to 10, the elements 5, 66, 6 to be constituents of the semiconductor device 1 are formed.
7. A resin package 3 is formed to seal W. The formation of the resin package is a part according to the present invention.

To form the resin package 3, first, as shown in FIGS. 6 and 7, each element 5, 66, 70 is formed in a cavity 70 formed by upper and lower molds 7 a, 7 b.
67, W. The cavity 70 is formed by a recess 70a of the upper mold 7a and a recess 70b of the lower mold 7b. The depth of the recess 70b of the lower mold 7b is smaller than the thickness of the lead frame 6 (the internal lead 67), and is, for example, about 1/20 to 1/5 of the thickness of the internal lead 67. In this embodiment, as expected from FIGS. 7 and 8, the opening areas of the recesses 70a and 70b are substantially the same, and the dam bars 63a and 63b of the lead frame 6 are formed by the molds 7a and 7b. External lead 68
Etc. are pinched. At this time, the dam bars 63a, 63b
The outer lead 67 and the like are compressed in the thickness direction, but the lower mold 7b has a concave portion 7 smaller than the thickness of the lead frame 6.
0b is formed, each part 63a, 63
The compression of b and 67 is performed not only on the upper surface side but also on the lower surface side. Therefore, as in the prior art, each part 63
The lifting of the tip 67a of the internal lead 67 caused by the compression of only the upper surfaces of the internal leads 67 is avoided, and the internal lead 67 is brought into close contact with the bottom surface of the recess 70b of the lower mold 7b. .

Next, as shown in FIG.
The molten resin is injected into the inside of the tube and solidified. The resin injected into the cavity 70 is, for example, an uncured epoxy resin, and the epoxy resin is thermally cured by heating the molds 7a and 7b in the state where the epoxy resin is injected into the cavity 70. At this time, since the inner leads 67 are in close contact with the bottom surface of the concave portion 70b of the lower mold 7b, the resin is prevented from flowing under the inner leads 67, and the lower surface of the inner leads 67 is prevented. The generation of burrs on the screen is avoided.

When the injection and solidification of the resin is completed in this way, as shown in FIG. 9, the upper and lower dies 7a, 7b
Is removed, the resin package 3 is formed above the rectangular area 64 as shown in FIG. Finally, the marking on the resin package 3, the internal leads 67 and the suspension leads 6
The semiconductor device 1 shown in FIG. 1 and FIG. 2 is obtained by cutting the space between 5 and the dam bar 63a.

In this embodiment, the opening areas of the concave portions of the upper and lower molds are the same, but the opening areas of these concave portions may be different. That is, as shown in FIG. 11, the opening area of the recess 70a 'of the upper mold 7a' may be made larger than that of the recess 70b 'of the lower mold 7b, or as shown in FIG. The opening area of the recess 70a "of the upper mold 7a" may be smaller than that of the recess 70b "of the lower mold 7b".

However, in order to improve the adhesiveness of the internal lead to the bottom surface of the concave portion of the lower mold (avoid lifting of the tip), the opening area of the concave portion of the upper mold must be equal to that of the concave portion of the lower mold. More preferably, it is larger.

[Brief description of the drawings]

FIG. 1 is an overall perspective view showing an example of a semiconductor device to which a resin package forming method for a semiconductor device according to the present invention is applied.

FIG. 2 is a sectional view taken along the line II-II in FIG.

FIG. 3 is a partial perspective view of a lead frame used for manufacturing the semiconductor device of FIGS. 1 and 2;

FIG. 4 is a partial perspective view showing a state where a semiconductor chip is mounted on a die pad in the lead frame of FIG. 3;

5 is a partial perspective view showing a state in which the electrode pads of the semiconductor chip are further connected to the internal leads of the lead frame via wires from the state shown in FIG. 4;

6 is a cross-sectional view illustrating a state where components of the semiconductor device in FIG. 5 are accommodated in cavities formed by upper and lower dies.

FIG. 7 is an enlarged sectional view of a main part of FIG. 6;

FIG. 8 is a cross-sectional view showing a state in which a resin is injected into the cavity shown in FIG.

FIG. 9 is a cross-sectional view showing a state in which upper and lower molds are removed from the state of FIG.

FIG. 10 is a partial perspective view showing a state where upper and lower dies are removed from the state of FIG. 8;

11 is an enlarged sectional view of a main part corresponding to FIG. 7, showing a modified example of a mold for realizing the resin package forming method of the present invention.

FIG. 12 is an enlarged sectional view of a main part corresponding to FIG. 7, showing a modified example of a mold for realizing the resin package forming method of the present invention.

FIG. 13 is a cross-sectional view illustrating an example of a semiconductor device obtained by a conventional resin package forming method.

14 is a cross-sectional view for describing a method of forming a resin package of the semiconductor device of FIG.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 semiconductor device 2 electrode (of semiconductor device) 21 lower surface (of electrode) 3 resin package (of semiconductor device) 30 lower surface (of resin device) 4 die pad (of semiconductor device) 5 semiconductor chip (of semiconductor device) W wire 6 lead Frame 66 Die pad (of lead frame) 67 Internal lead (to be an electrode of semiconductor device) 68 External lead 7a Upper die 7b Lower die 70 Cavity 70a Depression (of upper die) 70b Depression (of lower die)

Claims (2)

[Claims] 1. A semiconductor chip is mounted on a die frame on which a die pad and an internal lead serving as an electrode are formed, and the semiconductor chip and the internal lead are electrically connected via a conductor wire. In the connected state, the region extending further outward from the internal lead in the lead frame by the upper mold and the lower mold is compressed and sandwiched, and is placed in the cavity formed by the upper mold and the lower mold. A method of accommodating the die pad, the semiconductor chip, the conductor wire, and the internal lead, and injecting a resin into the cavity to form a resin package so that a lower surface of the internal lead is exposed. The mold has a concave portion whose depth is smaller than the thickness of the lead frame. Method. 2. The cavity is formed by a concave portion of the upper mold and a concave portion of the lower mold, and an opening area of the concave portion of the upper mold is equal to or larger than an opening area of the concave portion of the lower mold. The resin package forming method for a semiconductor device according to claim 1, wherein: