JPH0283961A - Manufacture of semiconductor device, semiconductor device obtained by the method and semiconductor wafer used in the method - Google Patents

Abstract

PURPOSE:To improve the reliability of an extra-thin LSI package by a method wherein a pellet is placed on the tab of a lead frame and the dimension of the thickness direction of the predetermined part of the package molded after the pellet is bonded to the lead frame is specified. CONSTITUTION:The tab 6 of a lead frame 9 is so formed as to have a thickness not larger than 150mum and divided into a plurality of parts with slits. A pellet 3 having a thickness of 200-350mum is jointed with the upper surface of the tab 6 and bonded to the lead frame 9 with wires 8. The height from the upper surface of the pellet 3 to the top part of the wire 8 is so selected as not to exceed 200mum. Then the frame 9 is placed in a molding die 15 and resin 17 is cast and cured to form a package. With this constitution, the flowability of the resin 17 in a cavity 16 is improved and the package can be manufactured with a high yield and, further, the reliability of the extra-thin package can be improved.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a technique that is effective when applied to a semiconductor device having an ultra-thin package structure.

[Conventional technology]

In recent years, with the spread of IC cards and ultra-thin electronic devices, development of ultra-thin LSI packages to be mounted on these devices is progressing.

Regarding the ultra-thin LSI package mentioned above, for example, Mitsubishi Electric Corporation, published in December 1987, Triple-x-
(TRIPLE! A)! &Ll 8 (7) rUltra-thin type 256 is described in Bit SRAMJ.

The ultra-thin LSI package described in the above document has V
S OP (Very Small 0utline
The package has a package structure of 1M, which is less than 1/2 the thickness of the conventional SOP.

Further, a semiconductor pellet (hereinafter referred to as pellet) having a thickness of 400 μm is sealed in the package, and the pellet and the inner lead are connected via a wire. In addition, to prevent the top end of this wire from being exposed from the top of the package, a tab (
The gui pad) is located below the lead.

[Problem to be solved by the invention]

According to the inventor's study, the above-mentioned conventional ultra-thin LSI
The package has the following problems.

In other words, when manufacturing an ultra-thin LSI package with a thickness of In or less using the transfer molding method, the mold cavity is extremely narrow, so the fluidity of the resin injected into the cavity decreases, causing the tab and resin to Voids are likely to occur at the interface with the

In order to prevent this, it is necessary to use a low-viscosity resin to improve its fluidity and to equalize the flow speed of the resin flowing inside the cavity above the pellet and below the tab.

However, in the ultra-thin LSI package described above, the tabs are placed below the lead surface to prevent the upper ends of the wires from being exposed from the package, so when the lead frame is inserted into the mold during molding, the tabs and The gap between the pellet and the lower mold becomes narrower than the gap between the pellet and the upper mold.

As a result, more resin injected into the cavity flows onto the pellet with a wide gap than under the tab with a narrow gap, pushing the tab downward, resulting in voids occurring at the interface between the tab and the resin, etc. Defects such as the tab being deformed and exposed from the bottom surface of the package occur, reducing the yield of package manufacturing.

The present invention has been made in view of the above-mentioned problems, and its purpose is to provide a technique that can improve the manufacturing yield of ultra-thin LSI packages.

Another object of the present invention is to provide a technique that can improve the reliability of ultra-thin LSI packages.

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

[Means to solve the problem]

A brief overview of typical inventions disclosed in this application is as follows.

That is, the invention according to claim 1 forms a slit in a tab of a lead frame having a thickness of 150 μm or less, and a pellet having a thickness of 200 μm to 350 μm is bonded onto the tab via an adhesive. and the pellet, the height of which is 200 μm.
This is a method of manufacturing a semiconductor device, in which bonding is performed to a thickness of m or less, and then molded with a resin having a thickness of l mts or more than F.

The invention according to claim 2 is provided with a package having a thickness of 1 ill or less, a slit being formed in a tab of 150 μm or less in thickness sealed in the package, and a pellet having a thickness of 208 μm to 350 μm. The height of the wire bonded onto the tab via adhesive and connecting the inner lead and the pellet is 200 μm or less, and the thickness of the package above the pellet and the thickness of the package below the tab are 200 μm or less. This is a semiconductor device in which the difference in thickness is 50 μm or less.

The invention according to claim 3 has a thickness of 200 μm to 350 μm.
It is a μm semiconductor wafer.

[Operation] According to the invention described in claim 1, since the distance from the tab to the upper end of the wire is reduced, when molding the pellet,
The gap between the tab and the lower die and the gap between the pellet and the upper die can be widened, and the widths of these gaps can be made almost equal.

This improves the fluidity of the resin flowing inside the cavity during molding, and the amount of resin flowing under the tab equals the effort of the resin flowing over the pellet, effectively preventing the generation of voids and deformation of the tab. This makes it possible to manufacture ultra-thin LSI packages with a thickness of one thickness or less with good yield.

Note that if the thickness of the pellet is 350 μm or more, the distance from the bottom of the tab to the top of the wire can only be slightly reduced.
It is not possible to prevent the occurrence of voids and deformation of the tab.

On the other hand, if the thickness of the pellet is less than 200 μm, the mechanical strength decreases, chipping occurs during the manufacturing process, and handling becomes difficult, making it impossible to improve the yield.

According to the second aspect of the invention, the thickness of the package above the pellet and the thickness of the package below the tab are increased, so that the moisture resistance of the package is improved. Further, since the tab is divided into a plurality of parts via the slit, stress applied to the tab is dispersed, and cracks in the package due to this stress can be effectively prevented.

As a result, an ultra-thin LS with a thickness of l mm or less
The reliability of the I package can be improved.

According to the third aspect of the invention, by mounting this pellet on the tab of the lead frame and sealing it in a package, the distance from the tab to the upper end of the wire can be reduced. Therefore, when molding pellets, the gap between the tab and the lower mold and the gap between the pellet and the upper mold can be widened, and the widths of these gaps can be made almost equal, so that the thickness can be increased. It is possible to manufacture ultra-thin LSI packages with lw or less with a high yield. Also, the thickness of the package above beret 1),
and the increased thickness of the package below the tab, which improves the moisture resistance of the package.

〔Example〕

FIG. 1 is a sectional view of a main part of a semiconductor device that is an embodiment of the present invention, FIG. 2 is a plan view of a main part of a lead frame used in this semiconductor device, and FIGS. FIG. 4 (a
) to (C) are sectional views of essential parts of a mold, also showing the method of manufacturing this semiconductor device.

The semiconductor device of this embodiment is, for example, Q F P (Qua
dFlat Package) and package l
For example, the silicone modified epoxy resin is filled with a filler such as silica to make the thermal expansion coefficient close to that of silicone, and the resin is transfer molded. In addition, the above-mentioned resin constituting this package l is
It is a low viscosity resin that has a viscosity of, for example, about 1x10'P (poise) when cold.

The dimensions of the package 1 are, for example, 14+am in length and width on each side, and 1m+a in thickness, for example. On the side surface of this package 1, for example, 44 13-cords 2 constituting human output pins and power supply pins extend outward and are bent into a gull-wing shape.

A semiconductor pellet 3 made of silicon single crystal is sealed inside the package 1 . The thickness of this pellet 3 is, for example, 300 μm, and its upper surface serves as an integrated circuit forming surface. This pellet 3 is obtained by slicing a silicon single crystal ingot to create, for example, a 300 μm thick semiconductor wafer (not shown), forming an integrated circuit on this semiconductor wafer by a predetermined process, and then guising this. It is something.

A memory LSI (not shown) such as a 4 megabit mask ROM, for example, is formed on the integrated circuit forming surface of the pellet 3, and the surface of this Memo'JLSI is coated with an extremely thin polyimide resin 4. This polyimide resin 4 has moisture in the resin that makes up the package 1.
This is to prevent the resin from entering the SI and also to prevent the surface of the Memo' JLSI from being damaged by the filler in the resin.

The pellet 3 is bonded to a tab 6 via a thin adhesive 5 made of, for example, silver paste.

A slit 7, which will be described later, is formed in this tab 6. Further, the thickness of the tab 6 is, for example, 150 μm. On the other hand, for the adhesive 5, a material with low foamability is selected because it is necessary to reduce the film thickness. Note that if the solvent rapidly expands when baking the adhesive 5, air bubbles will be generated in the adhesive 5, resulting in an increase in the film thickness. To prevent this, for example, a curing method may be used in which heating is performed gradually in an open furnace installed in a clean room.

For example, when the adhesive 5 made of silver paste is baked using this curing method, the film thickness can be reduced to about 0 to 30 μm.

The pellet 3 and the glue 2 in the package 1 are electrically connected via a wire 8 made of, for example, a gold wire with a diameter of 25 μm.

In this example, in order to prevent the upper end of the wire 8 from being exposed from the upper surface of the package 1 when molding the package 1, the height (h) from the upper surface of the pellet 3 to the upper end of the wire 8 is set to 200 μm or It is smaller than that, and the tab 6 is arranged below the lead 2.

As described above, in this embodiment, for example, the pellet 3 with a thickness of 300 μm is mounted on the tab 6 with a thickness of 150 μm via the adhesive 5 with a thickness of 10 to 30 μm, so that the wire 7 can be connected from the tab 6. The distance to the top edge is smaller than before.

As a result, the thickness of the package l above the pellet 3 (A) and the thickness of the package 1 below the tab 6 (B) are both larger than those of the conventional ultra-thin LSI package. ). Further, the difference (AB) between the thickness (A> and the thickness (B)) is 50 μm or less, which is approximately the same thickness.

FIG. 2 shows a lead frame 9 used in manufacturing the semiconductor device of this embodiment. This lead frame 9 includes a tab 6 on which the pellet 3 is mounted, a dam 10 surrounding the tab 6,
A rectangular shape consisting of tab suspension leads 11 formed at the four corners of the tab 6, for example 44 leads 2 arranged radially around the tab 6, and an outer frame part 12 and an inner frame part 13 surrounding these. It is composed of a frame.

As for the lead 2, the outside of the dam IO is called the external lead, and the inside is called the internal lead.When the product is manufactured, the internal lead is sealed in the package l, and the outside lead is called the internal lead. The ffl U-do projects outward from the side surface of the package l and constitutes an external terminal.

Outer frame 11'l! A guide hole 14, which serves as a guide during transportation and positioning of the lead frame 9, is punched out in the lead frame 12 using a press or the like.

The lead frame 9 is formed by pressing a plurality of unit frames constituted by the above-mentioned parts arranged in the direction in which the outer frame part 12 extends, for example seven series, and is made of the following materials: For example, it is made of 42 alloy, and its thickness is, for example, 150 μm.

A cross-shaped slit 7 is formed in the tab 6 of the lead frame 9. That is, the tab 6 is divided into four parts via the slit 7.

This is a configuration for dispersing the stress applied to the tab 6 when, for example, water in the resin constituting the package l evaporates and expands during solder reflow.

Next, the molding process of the package l using the lead frame 9 is shown in FIGS. 3(a) to rb) and FIGS. 4(a) to (
This will be explained using C1.

First, the pellet 3 is bonded onto the tab 6 using an adhesive 5 made of, for example, silver paste, and the adhesive 5 is heated at 180°C, for example.
(Fig. 3(a)). At that time, for example, if the above-mentioned curing method is used, the film thickness of the adhesive 5 can be reduced to 10 to 30 μm.
It can be made as thin as about m.

Next, a wire 8 made of a gold wire having a diameter of 25 μm, for example, is bonded between the tab 6 and the lead 2 using a wire bonding device (not shown) (FIG. 3(b)).

At that time, in order to prevent the upper end of the wire 8 from being exposed from the package 1 in the molding process described later, the height (h) from the upper surface of the pellet 3 to the upper end of the wire 8 is set at 20 m.
Bonding is performed so that the thickness is 0 μm or less.

Next, as shown in FIG. 4(a), the lead frame 9 is installed at a predetermined position in a mold 15 for transfer molding. The upper mold 15 inside the cavity 16 of this mold 15
The gap between a and the lower die 15b is, for example, 1 mm. In addition, at this time, the gap between the pellet 3 and the upper die t5a (, A
) and the gap (B) between the tab 6 and the lower mold 15b (A
The tab 6 is placed below the lead 2 by bending the tab suspension lead 11 in advance so that -B) is 50 μm or less.

Next, the preheated pellet-shaped resin 17 is poured into the shell 18.
put it into. Subsequently, the plunger 19 is lowered and the molten resin 17 is injected into the cavity 16 via the runner 20 and the gate 21 (FIG. 4(b)).

Finally, after the resin 16 injected into the cavity 16 has hardened, the mold 15 is opened, the lead frame 9 is taken out and cut at a predetermined portion, thereby completing a package l having a thickness of, for example, 1 m (the first Figure 4 (C)).

As described above, according to this embodiment, the following effects can be obtained.

(1) 1 For example, on the tab 6 with a thickness of 150 μm,
By joining the pellets with a thickness of 300 μm through the thin adhesive 5 of ~30 μm, the distance from the tab 6 to the upper end of the wire 8 is reduced, so when molding the pellet 3, the tab 6 and the lower mold 15b and the gap (A) between the pellet 3 and the upper mold 15a can be widened, and the widths of these gaps can be made almost equal.

(2), Due to (1) above, cavity 1 is
The fluidity of the resin 17 flowing inside the tab 6 is improved, and the amount of the resin 17 flowing under the tab 6 becomes equal to the amount of the resin 17 flowing over the pellet 3, which effectively prevents the generation of voids and deformation of the tab 6. The thickness can be, for example, 1 m.
+e package l can be manufactured with high yield.

(3) As a result of the reduction in the distance from the tab 6 to the upper end of the wire 8, the thickness of the package 1 above the pellet 3 and the thickness of the package below the tab become larger than before. Improves moisture resistance. Moreover, since the tab 6 is divided into a plurality of parts via the slit 7, the stress applied to the tab 6 is dispersed, and cracks in the pub cage 1 caused by this stress can be effectively prevented.

(4) According to (3) above, the reliability of a semiconductor device including a package 1 having a thickness of, for example, one thickness is improved.

As above, the invention made by the present inventor has been specifically explained based on Examples, but it should be noted that the present invention is not limited to the Examples and can be modified in various ways without departing from the gist thereof. Not even.

That is, the thickness of the pellet 3 is not limited to 300 μm, but may be within the range of 200 to 350 μm.

The pellet 3 used in the above example has a thickness of 300μ, for example.
After forming an integrated circuit on a 400 μm thick semiconductor wafer, this is not limited to this. For example, after forming an integrated circuit on a 400 μm thick wafer, which is the same as conventional products, A material that has been polished to a thickness of 300 μm may also be used.

Although the package in the above embodiment was a QFP, it is not limited to this, and for example, a 5OP (Sfflal
l 0utline Package) and S OJ (
Small 0utlineJ-1ead Packa
ge).

〔Effect of the invention〕

Among the inventions disclosed in this application, the effects obtained by typical inventions are briefly described below.

That is, a slit is formed in a tab of a lead frame with a thickness of 150 μm or less, a pellet with a thickness of 200 μm to 350 μm is bonded to the tab via an adhesive, and a wire is used to connect the lead frame and the pellet. % of semiconductor devices that are bonded to a height of 200 μm or less and then molded with resin to a thickness of 1 m or less! According to the manufacturing method, an ultra-thin LSI with a thickness of I m+a or less
Packages can be manufactured with high yield.

Alternatively, a slit is formed in a tab with a thickness of 150 μm or less sealed in a package with a thickness of I mm or less, and a pellet with a thickness of 200 μm to 350 μm is bonded onto the tab via an adhesive. , the height of the wire connecting the inner lead and the pellet is 200 μm.
According to a semiconductor device in which the difference between the thickness of the package above the pellet and the thickness of the package below the tab is 50 μm or less,
The reliability of an ultra-thin LSI package with a thickness of lu or less can be improved.

Furthermore, the above effects can be obtained by using a semiconductor wafer with a thickness of 200 μm to 350 μm.

[Brief explanation of drawings]

FIG. 1 is a sectional view of a main part of a semiconductor device that is an embodiment of the present invention, FIG. 2 is a plan view of a main part of a lead frame used in this semiconductor device, and FIGS. FIGS. 4(a) to 4(C) are sectional views of main parts of a lead frame showing a method of manufacturing this semiconductor device, and FIGS. 4A to 4C are sectional views of main parts of a mold also showing a method of manufacturing this semiconductor device. 1. .Package, 2. .Lead, 3.
... Semiconductor pellet, 4... Polyimide resin, 5 Adhesive, 6... Tab, 7... Slit, 8... Wire, 9... Lead frame, IO... Dam, 11...
...Tab hanging lead, 12...Outer frame part, 13...Inner frame part, 14...Guide hole, 15...Mold, 15a...
... Upper mold, 15b... Lower mold, 16... Cavity,
17...Resin, 18...Pot, 19...Plunger 20...Runner 21...Kate. Agent Patent Attorney Daiwa Tsutsui

Claims (1)

[Claims] 1. A slit is formed in the tab of a lead frame having a thickness of 150 μm or less, and the thickness is 200 μm to 350 μm.
A μm semiconductor pellet is bonded onto the tab via an adhesive, and a wire connecting the lead frame and the semiconductor pellet is bonded to a height of 200 μm or less. 1mm
Or a method of producing a semiconductor device that is characterized by molding with a resin below. 2. A package with a thickness of 1 mm or less is provided, a slit is formed in a tab with a thickness of 150 μm or less sealed in the package, and a semiconductor pellet with a thickness of 200 μm to 350 μm is inserted into the package through an adhesive. The height of the wire bonded on the tab and connecting the lead and the semiconductor pellet is 200 μm or less,
The difference between the thickness of the package above the semiconductor pellet and the thickness of the package below the tab is 5.
2. A semiconductor device obtained by the method for manufacturing a semiconductor device according to claim 1, wherein the thickness is 0 μ or less. 3. A semiconductor wafer used in the method for manufacturing a semiconductor device according to claim 1, wherein the semiconductor wafer has a thickness of 200 μm to 350 μm.