JPH07142645A - Semiconductor and manufacture thereof - Google Patents

Abstract

PURPOSE:To prevent generation of cracks on the main body of a resin-sealed package. CONSTITUTION:A semicylindrical recess 20a is formed on each main surface of a resin-sealed package main body 27 in a TQFP IC 29, each recess is formed by a bottom face 21a having a uniform circular-shaped recessed curve surface and a semicircular side face 22a which is positioned on both edges of the bottom face. Accordingly, even when stress is on the resin-sealed package main body 27 by the heating in a solder reflowing process and the like, the generation of cracks can be decreased because the main surface of the package main body 27 is formed in an arch shape.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor device, and more particularly to a technique for preventing the occurrence of cracks in a resin-sealed package body, for example, a semiconductor integrated circuit device (hereinafter referred to as IC That is) related to effective technology.

[0002]

2. Description of the Related Art An IC having a surface mount type resin-sealed package includes a semiconductor pellet (hereinafter referred to as a pellet), a tab to which the pellet is bonded, and a tab.
A plurality of leads electrically connected to each bonding pad of the pellet via a bonding wire, and a package body for resin-sealing the pellet, the tab, and a part of each lead are provided.

It should be noted that I provided with a resin-sealed package
Examples of C are disclosed in JP-A-59-16357, JP-A-62-115752, and JP-A-62-
There is a 12833 publication.

[0004]

SUMMARY OF THE INVENTION In the above IC,
Since the thermal expansion coefficient of silicon forming the pellets, 42 alloy or copper forming the lead frame, and resin forming the package body is very different, the IC can be used in temperature cycle tests and thermal shock tests. ,Also,
When heated in the solder dip or reflow soldering process during mounting, peeling occurs at the interface between the resin of the package body and the leads of the lead frame, and water enters the gap formed by the peeling and accumulates. However, there is a problem that cracks occur in the resin-sealed package body due to the so-called steam explosion of the moisture.

An object of the present invention is to provide a semiconductor device capable of reducing the occurrence of cracks in the resin-sealed package body.

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

[0007]

The typical ones of the inventions disclosed in the present application will be outlined below.

That is, the semiconductor pellet, the tab to which the semiconductor pellet is bonded, the plurality of leads electrically connected to each bonding pad of the semiconductor pellet, the semiconductor pellet, the tab, and part of each lead are In a semiconductor device having a package body to be resin-sealed, at least one main surface of the resin-sealed package body has a recess whose bottom surface is formed into a concave curved surface over substantially the entire main surface. Is characterized by.

[0009]

According to the above-mentioned means, since the main surface of the resin-sealed package main body is formed with an indentation having a concave curved surface to form an arch shape, the resin-sealed package body is sealed with resin during the reflow soldering process or the like. Even if stress is generated by heating the package, the effect of the arch shape can sufficiently support the stress, and as a result, the occurrence of cracks in the resin-sealed package body can be reduced.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a resin-sealed type T which is an embodiment of the present invention.
QFP / IC (Thin Quad Flat Pac)
FIG. 3 is a perspective view showing a mounted state of the IC card. Figure 2
8A to 8C are explanatory views showing each step in the manufacturing method.

In this embodiment, the semiconductor device according to the present invention is constructed as a TQFP IC. This TQ
The FP / IC 29 includes a pellet 24, a tab 18 to which the pellet 24 is bonded, a plurality of leads 19 electrically connected to each bonding pad 24 a of the pellet 24 via a bonding wire 25, and a pellet 24. , A tab 18 and a resin-sealed package body 27 for sealing a part of each lead 19 with a resin.

The two main surfaces of the resin-sealed package main body 27 are substantially square in plan view, and each of these main surfaces has a flat surface concentric with the outer shape of the main surface over substantially the entire main surface. Substantially square recesses 20a and 20b are formed when viewed from above. These recesses 20a and 20b are in the shape of a semi-cylindrical shape, and have bottom surfaces 21a and 21b, which are formed in a uniform arcuate concave curved surface in one direction, and bottom surfaces 21a and 2b.
A pair of vertical side surfaces 22 each having a truncated circular shape and located at both ends of 1b.
a and 22b.

The TQF which is an embodiment of the present invention will be described below.
A method for manufacturing the PIC will be described. By this explanation, TQ
Details of the above-described configuration of the FP IC will be clarified together.

In this embodiment, the manufacturing method of the TQFP / IC is based on the multiple lead frame 11 shown in FIG.
The multiple lead frame 11 is manufactured and prepared by a multiple lead frame molding process. The multiple lead frame 11 is made of a thin plate made of a spring material having a relatively large mechanical strength such as iron-nickel alloy or phosphor bronze, and is suitable for punching or etching. Are integrally molded by. A plating process using silver (Ag) or the like is partially or entirely applied to the surface of the multiple lead frame 11 so as to appropriately perform the wire bonding described later (not shown). This multiple lead frame 11 has a plurality of unit lead frames 12 in the horizontal direction.
They are lined up in rows. However, only one unit is shown.

The unit lead frame 12 has a positioning hole 13
There is provided a pair of outer frames 13 in which a is provided, and both outer frames 13 are arranged in parallel at a predetermined interval and extend in series. Adjacent unit lead frame 1
A pair of section frames 14 are provided between the outer frame 13 and the outer frame 13,
The unit lead frames 12 are arranged in parallel with each other between the 13 and are integrally installed. The unit lead frame 12 is formed in a substantially square frame body (frame) formed by the outer frame and the section frame.

In each unit lead frame 12, a dam suspension member 15 is provided at the connecting portion of the outer frame 13 and the section frame 14 so as to be disposed in a substantially right angle direction and integrally projected. The four dam members 16 are arranged so as to have a substantially square frame shape and are integrally suspended.

A tab suspension lead 17 is arranged at one end of each dam member 16 on the side of the section frame 14, and the tab suspension leads 17 are arranged at approximately 4
The tabs 18, which are integrally provided so as to face each other in the direction of 5 degrees and are formed in a substantially square flat plate shape at the tips of the tab suspension leads 17, are substantially concentric with the frame shape of the dam member 16 group. The tab suspension leads 17 are integrally arranged so as to be suspended by the tab suspension leads 17.

Each tab suspension lead 17 is bent near the tab 18, and the tab suspension lead 17 is bent.
Due to the bending, the tab 18 is lowered from the surface of the lead group described later by the thickness of the pellet described later (so-called tab lowering).

Further, a plurality of leads 19 as electric wiring are arranged on the dam member 16 at equal intervals in the longitudinal direction, and are integrally projected so as to be parallel to each other and orthogonal to the dam member 16. . The inner end of each lead 19 has a tab 1 at the tip.
The inner portion 19 is arranged by surrounding 8
a respectively. On the other hand, the outer extension of each lead 19 has its tip at the outer frame 13 and the section frame 1.
4 and each constitute an outer portion 19b. The portion of the dam member 16 between the adjacent leads 19 substantially constitutes a dam 16a that blocks the flow of the resin at the time of molding the package body, which will be described later.

The multiple lead frame 11 having the above-mentioned structure prepared in the multiple lead frame molding step is
In the pellet bonding process and the wire bonding process, the pellet bonding work and then the wire bonding work are performed. These bonding operations are sequentially performed for each unit lead frame by laterally pitching multiple lead frames.

First, as shown in FIGS. 3 and 4, a pellet 24 as a semiconductor integrated circuit structure in which an integrated circuit is formed in a so-called pre-process in the manufacturing process of a semiconductor device by a pellet bonding operation is shown. In addition, the unit lead frame 12 is disposed at a substantially central portion on the tab 18 and is mechanically fixed by a bonding layer 23 formed between the tab 18 and the pellet 24 for bonding. As a method for forming the pellet bonding layer 23, a bonding method using a gold-silicon eutectic layer, a soldering layer, a silver paste adhesive layer, etc. can be used. However, it is desirable to form the bonding layer 23 so that it does not become a barrier to heat transfer from the pellet to the tub, if necessary.

Then, by wire bonding work,
Bonding pad 2 of pellet 24 bonded onto tab 18 as shown in FIGS. 3 and 4.
4a and the leads 19 in each unit lead frame 12
The both ends of the bonding wire 25 are bonded to the inner part 19a of the same by using a suitable wire bonding device (not shown) such as an ultrasonic thermocompression bonding wire bonding device. Bridged. As a result, the integrated circuit built in the pellet 24 is electrically pulled out to the outside through the bonding pad 24a, the bonding wire 25, the inner portion 19a and the outer portion 19b of the lead 19.

In the assembly 26 thus pellet-bonded and wire-bonded, a group of package bodies 27 to be resin-sealed for each unit lead frame is formed by transfer molding as shown in FIGS. 5 and 6. Device 30
Are used for simultaneous molding of a unit lead frame group.

The transfer molding apparatus 30 shown in FIGS. 5 and 6 is provided with a pair of an upper mold 31 and a lower mold 32 which are clamped to each other by a cylinder device or the like (not shown). A plurality of upper mold cavity concave portions 33a and a plurality of lower mold cavity concave portions 33b are respectively formed on the mating surface of the lower mold 32 and the lower mold 32 so as to cooperate with each other to form the cavity 33. In this embodiment, the total height of the cavity 33 is set to 1 mm or less in order to correspond to the TQFP / IC.

The upper mold cavity concave portion 33a and the lower mold cavity concave portion 33b are substantially square in plan view, and the bottom surfaces of the respective concave portions 33a and 33b are concentric with the shape of the bottom surface over substantially the entire bottom surface. The convex portions 43a and 43b having a substantially square shape are formed so as to project from the top. Each of the convex portions 43a and 43b has a semi-cylindrical shape, and has a bottom surface 44 formed in a convex curved surface having a uniform arc shape in one direction.
a, 44b and a pair of vertical side surfaces (lower mold cavity concave portion 33b) in the shape of a truncated circle located at both ends of the bottom surfaces 44a, 44b.
6C, the side surface in the upper mold cavity recess 33a is also formed in the same manner. )
It is formed by.

A pot 34 is opened on the mating surface of the upper die 31, and a cylinder device (not shown) is provided in the pot 34.
A plunger 35 that is advanced and retracted by is inserted so that a resin (hereinafter, referred to as a resin) as a molding material can be fed.

On the mating surface of the lower mold 32, a cull 36 is disposed so as to face the pot 34 and is recessed.
A plurality of runners 37 are radially arranged and connected so as to be connected to the culls 36, respectively. The other end of each runner 37 is connected to the lower cavity recess 33b, and a gate 38 is formed at that connection so that the resin can be injected into the cavity 33. Also,
On the mating surface of the lower die 32, a relief recess 39 is formed in a rectangular shape slightly larger than the outer shape of the multiple lead frame 11 so that the relief recess 39 can escape the thickness of the lead frame. It is set up.

When the resin-sealed package body is transfer-molded by using the assembly 26 having the above-mentioned structure, each cavity 3 in the upper mold 31 and the lower mold 32.
3 is a pair of dams 16 in each unit lead frame 12.
It corresponds to the space between a and 16a, respectively.

At the time of transfer molding, in the assembly 26 according to the above-mentioned structure, the multiple lead frame 11 has the lower die 3
It is housed in the escape recess 39 that is buried in the unit 2, and the pellets 24 of each unit lead frame 12 are arranged and set so as to be housed in each cavity 33.

Subsequently, the upper die 31 and the lower die 32 are clamped, and the resin 40 is moved from the pot 34 by the plunger 35 through the runner 37 and the gate 38 to each cavity 3.
It is sent to 3 and press-fitted.

After the injection, when the resin is thermoset and the resin-sealed package body 27 is molded, the upper mold 31 and the lower mold 32 are opened, and the resin is sealed by an ejector pin (not shown). The stationary package body 27 group is released. In this way, as shown in FIGS. 7 and 8, the assembly 28 in which the group of resin-sealed package bodies 27 is molded is removed from the transfer molding device 30.
The tab 18, the pellet 24, the inner portion 19a of the lead 19 and the wire 25 are resin-sealed inside the resin-sealed package body 27 resin-molded as described above.

In the present embodiment, the upper mold cavity concave portion 33a and the lower mold cavity concave portion 33b respectively have a semi-cylindrical convex portion 43a on the bottom surfaces thereof over substantially the entire bottom surface thereof.
Since 43b is formed so as to project, a semi-cylindrical recess 2 is formed on each of the two main surfaces of the resin-sealed package body 27.
0a, 20b are formed.

Although not shown, the assembly 28 as a semi-finished product in which the resin-sealed package body is molded has the outer frame 13 and the dam 16a sequentially cut off for each unit lead frame in the lead cutting molding process. The outer portion 19b of each lead 19 is bent and formed in a gull wing shape.

Resin-sealed type T manufactured as described above
The QFP / IC 29 is mounted on the printed wiring board as shown in FIG.

A plurality of lands 42 are provided on the printed wiring board 41, and a resin-sealed TQFP / IC 29 to be mounted is to be mounted.
Are arranged so as to correspond to the respective leads 19 in the above, and are formed in a substantially rectangular thin plate shape by using a solder material. The leads 19 groups of the IC 29 are aligned and abutted against the land 42 groups. In addition, the leads 19 and the lands 42 are electrically and mechanically connected to each other by a solder layer (not shown) formed by the reflow soldering process.

Next, the operation will be described. T related to the above configuration
The QFP / IC is inspected before shipment. Environmental tests including temperature cycle tests and thermal shock tests are carried out as sampling inspections. Further, when the TQFP / IC is mounted on a printed wiring board or the like, the TQFP / IC is heated by the solder dipping process or the reflow soldering process.

When a thermal stress is applied to the TQFP / IC 29 having the above-described structure during such an environmental test or mounting, a stress is generated inside the resin-sealed package body 27 due to the difference in the thermal expansion coefficient of the constituent materials.

When the outer peripheral edge of the tab is formed in a sharp right angle, the internal stress of the resin-sealed package body is concentrated near the outer edge on the back surface of the tab. However, cracks in the resin-sealed package body do not occur with such stress concentration. However, if peeling occurs at the interface between the bottom surface of the tab and the resin of the package or the interface between the tab and the pellet due to repeated stress due to repeated thermal stress, excessive stress acts on the stress concentration point, and so there is a starting point there. Then cracks occur.

Further, the moisture absorbed inside the resin-sealed package body in the storage process after the completion of the resin-sealed package should be generated in a gap generated by peeling between the lower surface of the tab and the sealing of the package body. When invading, TQFP
When the IC is heated, the moisture expands due to the heating, so-called steam explosion occurs, so that even more stress is generated. For this reason, it has been clarified that there is a problem that cracks originating from the stress concentration points are more likely to be generated.

However, in the present embodiment, for example, as shown in FIG.
Moisture absorbed by the resin is accumulated in the gap formed at the interface between the lower surface of the tab 18 and the resin of the resin-sealed package body 27, and the resin-sealed package body 2 at the time of heating described above.
Even if a so-called steam explosion caused by the temperature rise of 7 occurs, the bottom surfaces 21a of the recesses 20a, 20b formed on the main surfaces of the resin-sealed package body 27,
Since 21b is formed in a uniform arcuate concave curved surface and is formed in an arch shape, stress can be sufficiently supported by the effect of the arch shape, and the resin-sealed package main body 27
It is possible to reduce the occurrence of cracks in the.

According to the embodiment described above, the following effects can be obtained. A temperature rise of the resin-sealed package body is achieved by forming a recess on the main surface of the resin-sealed package body over almost the entire main surface, and the bottom surface of this recess is formed into a uniform arc-shaped concave curved surface. Even if stress is generated due to the above, the stress can be sufficiently supported by the concave curved surface, and thus cracks in the resin-sealed package body can be reduced.

As described above, since it is possible to prevent the occurrence of cracks in the resin-sealed package body, it is possible to further reduce the thickness of the surface mount type package and reduce the size thereof, and an IC including the surface mount type package. It is possible to further increase the integration density and packaging density.

By forming a recess on the main surface of the resin-sealed package main body over substantially the entire main surface and forming the bottom surface of the recess into a uniform arcuate concave curved surface, the resin-sealed package main body is formed. The amount of resin used to form the resin can be reduced, and the cost can be reduced.

10 to 12 show a TQFP IC which is another embodiment 2 of the present invention. Example 2 and Example 1 above
Is different only in the shape of the recess formed in the main surface of the resin-sealed package body, and the other configurations are the same.

The recesses 20a, 20b formed over substantially the entire main surfaces of the resin-sealed package body 27 in the second embodiment are formed in a spherical shape that is arcuate in all directions. . Therefore, in the molding device for the resin-sealed package body, spherical convex portions are formed on the bottom surfaces of the upper mold cavity concave portion and the lower mold cavity concave portion that form the cavity, and these convex portions form the package. Spherical recesses 20a, 20b are formed on each main surface of the resin-sealed package body 27 during molding of the body.
Is formed.

Although the invention made by the present inventor has been specifically described based on the embodiments, the present invention is not limited to the above embodiments, and various modifications can be made without departing from the scope of the invention. Needless to say.

In the above description, the invention made by the present inventor is the field of application which is the background of the invention.
Although the case where the invention is applied to the P.IC has been mainly described, the invention is not limited thereto and the invention can be applied to all semiconductor devices including a resin-sealed package.

[0048]

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

Since at least one main surface of the resin-sealed package body has a recess whose bottom surface is formed into a concave curved surface over substantially the entire main surface, cracks occur in the resin-sealed package body. It is possible to reduce the amount of resin used for forming the resin-sealed package body, and it is possible to reduce the cost.

[Brief description of drawings]

FIG. 1 is a resin-encapsulated TQFP, which is an embodiment of the present invention.
It is a perspective view which shows the mounted state of IC.

FIG. 2 is a partially omitted plan view showing a multiple lead frame used in the method for manufacturing the TQFP / IC.

FIG. 3 is a partially omitted plan view showing a state after a pellet and wire bonding step.

FIG. 4 is a front sectional view taken along line IV-IV in FIG.

FIG. 5 is a partially omitted vertical sectional view showing a molding step of a resin-sealed package body.

FIG. 6 shows a lower mold cavity recess of the molding apparatus,
(A) is a plan view, (b) is a bb line sectional view in (a), (c) is a cc line sectional view in (a).

FIG. 7 is a plan view showing the assembly after molding the resin-sealed package body.

8A is a sectional view taken along line aa in FIG. 7, and FIG.
FIG. 8 is a sectional view taken along line bb in FIG. 7.

FIG. 9 is an enlarged front sectional view for explaining the function of preventing crack generation.

FIG. 10 is a resin-sealed TQ that is another embodiment 2 of the present invention.
It is a perspective view which shows the mounting state of FP * IC.

FIG. 11 is a plan view showing the assembly after molding the resin-sealed package body.

12 (a) is a sectional view taken along line aa in FIG.
11B is a sectional view taken along line bb in FIG. 11.

[Explanation of Codes] 11 ... Multiple lead frame, 12 ... Unit lead frame, 13 ... Outer frame, 14 ... Section frame, 15 ... Dam suspension member, 16 ... Dam member, 16a ... Dam, 17 ... Tab suspension lead, 18 ... tab, 19 ... lead, 19a ... inner part, 19b ... outer part, 20a, 20b ... dent, 21
a, 21b ... Bottom surface, 22a, 22b ... Side surface, 23 ... Bonding layer, 24 ... Pellet, 24a ... Bonding pad, 25 ... Wire, 26 ... Assembly, 27 ... Resin-sealed package body, 28 ... Resin-sealed package body Assembly after molding, 29 ... TQFP / IC (semiconductor device), 30 ...
Transfer molding device, 31 ... upper mold, 32 ... lower mold, 33
... Cavity, 33a ... Upper mold cavity recess, 33
b ... Lower mold cavity recess, 34 ... Pot, 35 ... Plunger, 36 ... Cull, 37 ... Runner, 38 ... Gate, 3
9 ... Escape recess, 40 ... Resin, 41 ... Printed wiring board, 42 ... Land, 43a, 43b ... Convex part, 44a, 4
4b ... bottom surface, 45b ... side surface.

Claims (4)

[Claims] 1. A semiconductor pellet, a tab to which the semiconductor pellet is bonded, a plurality of leads electrically connected to each bonding pad of the semiconductor pellet, a semiconductor pellet, a tab, and a part of each lead. In a semiconductor device including a package body to be resin-sealed, at least one main surface of the resin-sealed package body is formed with a recess whose bottom surface is formed into a concave curved surface over substantially the entire main surface. A semiconductor device characterized by: 2. The semiconductor device according to claim 1, wherein the recess is formed in a circular arc shape or a semi-cylindrical shape that is uniform in one direction. 3. The semiconductor device according to claim 1, wherein the recess is formed in a spherical shape that forms an arc shape in all directions. 4. A semiconductor pellet, a tab to which the semiconductor pellet is bonded, a plurality of leads electrically connected to each bonding pad of the semiconductor pellet, a part of each of the semiconductor pellet, the tab and each lead. In a method of manufacturing a semiconductor device having a package body to be resin-sealed, an inner surface of a cavity of a molding die is provided with a convex portion, and a resin is placed in the cavity of the molding die. A package main body that is injected to mold the semiconductor pellet, the tab, and a part of each lead with resin is molded, and the molded package main body has at least one main surface and a bottom surface formed into a concave curved surface. A method of manufacturing a semiconductor device, comprising: a package body molding step in which a recess is formed over substantially the entire main surface.