JPS61269338A - Resin-sealed semiconductor device and molding die used for manufacture thereof - Google Patents

Abstract

PURPOSE:To improve the mold release characteristics of a package to a molding die by forming a predetermined taper to the side surface of a projecting section in the surface of the package. CONSTITUTION:In a package 1 shaped through resin mold, a pellet 4 is fitted to a tab 3 by a bonding material such as a conductive resin. The pellet 4 is connected electrically to the inner end section of a lead 2 through a gold wire. The lead 2 is bent inward along a projecting section 6, which is bent downward near the side end of the package 1 and shaped around the back of the package 1, and a nose section thereof is inserted into a recessed section 7 formed to the back of the package 1. A groove 20 is shaped between the projecting sections 6. Tapered angle theta is formed to the side surfaces of each projecting section 6. The tapered angle theta is set in order to improve the mold release characteristics of the package 1 to a molding die. It is desirable that the tapered angle theta is large from the viewpoint of the mold release characteristics of the package 1 to the molding die.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to a resin-sealed semiconductor device and a manufacturing technique thereof.

[Background technology]

A package of a resin-sealed semiconductor device is usually formed by a resin molding method using a molding die.

That is, after the bellet mounting process and wire bonding process to the lead frame are completed, the lead frame is held between the upper and lower molds, both of which have recesses, and in this state, epoxy resin is injected from the resin injection gate. A resin such as the above is injected into a cavity formed by a mold, and after the injected resin is cured for a predetermined period of time, it is removed from the mold.

In order to remove the package formed by injecting and hardening the resin from the mold, a press pin, or so-called eject bin, is provided in the mold.By applying a pressing force to the package with the eject pin, the package is released from the mold. removed from That is, the pan cage is released from the mold.

Here, in a resin-sealed semiconductor device, the resin used therein is required to have a property that exhibits a large adhesive force to the lead frame in order to improve the reliability of the semiconductor device. Since the resin is required to have such properties, the releasability of the package formed by injection curing from the molding die is not necessarily good.

If the mold release properties are poor, an undesirable amount of external force will be applied to the package by the eject bin during demolding.

The problem of mold releasability becomes particularly large when the surface of the package to be obtained is not flat but has irregularities, such as in the case of so-called plastic leaded chip carrier type (hereinafter also referred to as PLCC) semiconductor devices. .

In some cases, the package surface of a resin-sealed semiconductor device has a rough surface such as a matte finish.

This can be manufactured by using a molding die in which the inner surface of the recess, that is, the surface that contacts the surface of the pan cage after molding, has a matte finish.

This matte finish on the surface of the package is mainly performed to improve so-called marking, which is printing of the type, loft number, etc. on the surface of the package to identify the product. Here, in marking, the printability becomes worse if the surface of the package has a fine satin finish. As a result, marking defects are likely to occur. On the other hand, if the roughness of the satin surface is made rougher, the releasability between the mold and the package becomes worse.

Regarding resin-sealed semiconductor devices, the 1980 January
Published by Kogyo Kenkyukai Co., Ltd., March 15th, Japan Microelectronics Association line RRC mounting technology JP149-P1
50.

[Purpose of the invention]

One object of the present invention is to provide a resin-sealed semiconductor device with excellent releasability from a mold.

Another object of the present invention is to provide a resin-sealed semiconductor device that has excellent marking printability and excellent mold releasability in a molding process.

Another object of the present invention is to provide a mold suitable for manufacturing the semiconductor device.

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.

[Summary of the invention]

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

That is, by providing a predetermined taper on the side surface of the protrusion on the package surface, the releasability of the package from the mold can be improved.

[Example 1] FIG. 1 (al is a cross-sectional view of a part of a so-called plastic leaded chip carrier (PLCC) type semiconductor device, which is an example of the present invention, and the first opening) shows the structure of the semiconductor device. FIG.

Moreover, FIG. 2 is a schematic perspective view of the semiconductor device of this example.

As shown in FIG. 2, in the semiconductor device of this embodiment, a number of lead portions 2 are embedded around the four sides of a package 1, and the tips of the leads are bent on the back surface of the package.

More specifically, as shown enlarged in FIG.
The bead 4 is attached by a bonding material (not shown), such as silicon eutectic, and the bonding pad electrode (not shown) thereon is attached to the lead 2.
The gold wire 5 is electrically connected to the inner end of the gold wire 5. Then, the portion of the lead 2 outside the package (hereinafter referred to as
Also called external lead. ) is bent downward near the side edge of the package 1, and further bent inward along the protrusion 6 formed around the back surface of the pan cage 1,
The tip end thereof is inserted into a recess 7 formed on the back surface of the pan cage 1.

The protrusion 6 has a function of preventing deformation of the lead 2 during mounting on a printed circuit board.

The protrusions 6 do not consist of one continuous piece, but correspond to each lead on a one-to-one basis, as is clear from the first opening. Therefore, there are grooves 20 between the protrusions 6.

The groove 20 is provided for the following reasons, for example.

That is, the lower ends 2a of the leads of the PLCC are electrically and mechanically coupled to the wiring of a wiring board (not shown) such as a printed circuit board using a brazing material such as solder. During the PLCC mounting process, undesirable reactants that may attack leads and wiring, such as flux used for soldering, must be cleaned if necessary to sufficiently improve the reliability of the electronic device. and removed. If the groove 20 is not formed, that is, if a continuous protrusion is provided for a plurality of leads, the cleaning liquid will not be trapped in the bottom part of the package surrounded by the protrusion. limited.

Accordingly, undesirable reactants cannot be sufficiently removed from the surfaces of the leads 2, the brazing material layer, the wiring layer of the wiring board, and the like. When the groove 2o is provided as described above, exchange of the cleaning liquid in the space between the bottom surface of the package l and the wiring board becomes sufficiently efficient. As a result, undesirable reactants in such spaces can also be sufficiently removed.

According to this example, as is clear from the first opening),
A taper angle θ is attached to the side surface of each protrusion 6. This taper angle θ is determined by the mold type 8a, which will be explained later with reference to FIG.
It is set in order to improve the releasability of the package 1 against the mold. The width of the portion of the protrusion 6 that directly corresponds to the lead 2 is set such that it provides a good guide for the lead 2.
substantially equal to the width of lead 2 or the first opening)
As shown in Figure 2, it is made slightly larger than that of lead 2.

The taper angle θ is desirably large from the viewpoint of releasability of the package 1 from the mold.
is desirably small in order to prevent the cross-sectional area of the groove 20 from decreasing. From these points of view, it is desirable that the taper angle θ is between 3 degrees and 20 degrees, particularly preferably 15 degrees.

FIG. 4 is a sectional view showing a mold according to another embodiment of the present invention applied to manufacturing the semiconductor device of this embodiment, including aspects of the molding process.

The mold 8 is composed of an upper mold 8a and a lower mold 8b, and a recess, that is, a cavity, is formed at a location exactly corresponding to each mold, and a semiconductor device is formed around the bottom of the recess of the lower mold. A recess 9 corresponding to the protrusion 7 is formed. As shown in the figure, the lead frame with the pellet attached and the wire bonding completed is held between the upper mold 8a and the lower mold 8b, and the epoxy resin is flowed into the recess of the upper mold 8a through the gate IO. A package is formed by filling the resin into the cavity 11 formed by the recess of the lower mold 8b.

The cavity 11 is filled with resin, and after a predetermined period of time has elapsed, that is, after the resin has hardened, the package is removed from the mold 8 using an eject pin (not shown), and then the leads are cut from the frame and the external leads are removed. By performing bending, the semiconductor device of this example is completed.

The resin is slightly reduced in volume when it is cured. As shown in FIG. 2, when a plurality of protrusions are formed for a plurality of leads, overall shrinkage of the resin constituting the package 1 causes side surfaces 6a or 6b of the protrusion 6 (the first The stress caused by the curing shrinkage, which results in a relatively large stress being applied between the opening (1)) and the mold 8b (FIG. 4), increases accordingly as the distance from the center of the package 1 increases. The stress applied to the side surface 6a or 6b is considered to be a shear stress on the protrusion 6. This stress also occurs when the package 1 is released from the mold.
The mutual frictional force between the protrusion 6 and the mold 8b is increased. Side surface 6a of protrusion 6.

When the taper angle θ is not substantially given to 6b, the above-mentioned frictional force becomes sufficiently large, making release from the mold difficult.

According to this embodiment, since the taper angle θ is given to the side surfaces 6a and 6b of the protrusion 6, the stress applied to the protrusion 6 when the resin is cured and shrunk can be applied in two directions, that is, on the plane of the package 1. and a direction substantially perpendicular to the plane of the package 1. As a result, as the resin hardens and shrinks, stress is generated to release the package 1 from the mold 8b.

In the semiconductor device of this embodiment, the surface of the upper package portion 1a above the buried surface of the leads 2 in FIG. Figure 3 fa) and (b)
1 shows the state in an enlarged manner, and fa) in the same figure shows part A in FIG. 1a), and part B in the same figure shows part B.

In the mold 8 of FIG. 4, the concave surface of the upper mold 8a is formed to have a rough surface, and that of the lower mold 8b is finer than that of the upper mold 8a, corresponding to the surface of the package of the semiconductor device to be manufactured. It is formed with a rough surface. For example, the surfaces of these recesses are made to have a surface roughness of about 13 μm in the upper mold 8a and 6 to 8 μm in the lower mold 8b.

FIG. 5 shows an enlarged view of the surface condition.
"at" indicates section A in FIG. 4, and "at" indicates section B in the same figure.

The main parts of the molds 3a and 3b are made of a material such as cemented carbide, and are formed by a machining technique such as electrical discharge machining.

The concave surface of each mold becomes rough during electrical discharge machining. The degree of roughness, that is, the roughness, is determined by the machining conditions during electrical discharge machining. Each mold is worn out as it is repeatedly used due to mutual friction between it and a filler having a relatively high hardness, such as a filler mainly composed of silicon oxide powder, which is mixed into the injected resin. Although not shown, a relatively thin coating layer such as a hard chrome plating layer is formed on the surface of the recessed portion of the mold. The surface of the covering layer has substantially the same roughness as the underlying material. If the wear progresses, for example, the old coating layer is removed and a new coating layer is formed again. Therefore, the covering layer constitutes a kind of reproduction layer in the mold.

Generally, if the surface of the mold is formed with a rough surface, the releasability in the step of removing the package from the mold will be poor, and therefore there is a problem in that external defects such as package chipping are likely to occur. In particular, a semiconductor device having a protrusion 7 on the back surface of a pan cage, such as the semiconductor device of Example 2, has a particularly serious problem.

On the other hand, if the surface of the mold is formed with a finely rough surface, the mold releasability will be improved, but the printability of the marking applied to the package surface of the manufactured semiconductor device will be lowered, resulting in marking defects.

By using the mold 8 as shown in FIG. 5, the surface of the upper package part 1a can be formed to be rough, so that marking with high printability can be achieved on the surface of the upper package part, and furthermore, Since the releasability between the lower mold and the package can be improved, workability can be improved and defects can be prevented. Particularly, this embodiment is extremely effective for a semiconductor device including a lower package portion 1b having a complicated structure as in this embodiment.

〔effect〕

(1) Since the side surface of the part where a step occurs, such as a protrusion, is tapered, it is possible to obtain a resin-sealed semiconductor device in which no excessive stress is applied to the step, and as a result, package chipping is reduced. A semiconductor device without appearance defects can be obtained.

(2) Manufacturing a resin-sealed semiconductor device using a mold in which at least a part of the inner surface of the recess of the upper mold is finished with a rough surface, and the inner surface of the recess of the lower mold is finished with a fine rough surface. As a result, it is possible to improve the mold releasability of at least the lower mold in the molding process, thereby preventing appearance defects such as package chipping.

(3) According to (2) above, it is possible to improve the yield of semiconductor devices.

(4) By using the mold described in (2) above, it is possible to manufacture a semiconductor device in which at least a part of the surface of the upper package portion has a rough surface, so that it is possible to mark the rough surface with good printability. be.

(5) According to (3) and (4) above, a semiconductor device with highly reliable markings can be provided at low cost.

(6) Applying the mold described in +11 above to a PLCC type semiconductor device is particularly effective since the semiconductor device has a complicated back surface of the package.

(7) Since the friction between the mold having a finely roughened surface and the filler mixed in the injected resin is reduced by the finely roughened surface, a mold with a long life can be obtained.

(8) A mold that is made to have a complicated shape and is therefore expensive due to the presence of multiple step portions can be made to have a long life due to the above (η), so it is possible to obtain a mold that is substantially cheaper. can.

Although the invention made by the present inventor has been specifically explained above based on Examples, it goes without saying that the present invention is not limited to the Examples and can be modified in various ways without departing from the gist thereof. Nor.

For example, although a semiconductor device has been described in which the entire surface of the upper package portion is formed of a rough matte surface, the present invention is not limited to this; a portion of the surface of the upper package portion,
In other words, only the marking portion may be made rough.

Similarly, the mold used for manufacturing the semiconductor device is not limited to one in which the entire inner surface of the upper mold is formed of a rough satin finish (although only a part of the inner surface may be rough). Needless to say.

The upper mold and the lower mold merely correspond to the upper surface and lower surface (or back surface) of the package to be obtained, and the molds may be located either above or below in the sealing device. It can be made of materials other than metal.

[Application field]

The above explanation will mainly focus on the field of application made by the present inventor, which is the so-called PLCC.
Although the description has been made regarding the case where the application is applied to a semiconductor device of the type semiconductor device, the present invention is not limited thereto. It is.

[Brief explanation of the drawing]

FIG. 1 is a partial sectional view showing a semiconductor device according to an embodiment of the present invention, FIG. 1B is a partial side view of the semiconductor device, and FIG. 2 is a schematic diagram of the semiconductor device. Perspective view, Figure 3 ia+
3 is an enlarged sectional view showing the surface part of the upper pancage part, FIG. 4 is an enlarged sectional view showing the surface part of the lower package part, and FIG. A partial sectional view showing the mold, Figure 5 (al is an enlarged sectional view showing the surface of the recess of the upper mold, and Figure 5 (bl is an enlarged sectional view showing the surface of the recess of the lower mold). ...Package, 1a...Upper package part,
1b...lower package part, 2...lead, 3.
...Tab, 4...Pellet, 5...Wire, 6...
・Protrusion, 7... Recess, 8... Mold, 8a... Upper mold, 8b... Lower mold, 9... Recess, 10... Gate, 11... Cavity . Figure 1 (b) Figure 3

Claims (1)

[Claims] 1. On the surface of the package located on one side of a plane formed by a plurality of lead wires, a stepped portion is formed with a side surface facing in a different direction with respect to the direction of extension of the plane. 1. A resin-sealed semiconductor device characterized in that the side surface is tapered. 2. The resin-sealed semiconductor device according to claim 1, wherein the stepped portion is comprised of a convex portion corresponding to each lead wire in a plastic leaded chip carrier type package. 3. The resin-sealed semiconductor device according to claim 2, wherein a marking portion is formed on the surface of the package located on the other side with respect to the plane, and at least the marking portion has a roughened surface. . 4. Claim 3, characterized in that the package surface located on the other side with respect to the plane is made into a rough surface, and the package surface located on the one side is made into a finely roughened surface. The resin-sealed semiconductor device described above. 5. Claim 3, wherein the package is formed by a resin molding method, and the rough surface of the package is determined by the mold type.
The resin-sealed semiconductor device according to item 1 or 4. 6. A resin-sealed semiconductor device with a roughened package surface, wherein at least a marking portion of the package surface on one side of the plane formed by the lead wire is formed with a rough surface, and the flat surface A resin semiconductor device in which a package surface on the other side is formed with a finely roughened surface. 7. The semiconductor device according to claim 6, which is comprised of a plastic leaded chip carrier type package in which a convex portion for preventing lead deformation is formed on the back surface of the package. 8. A mold for manufacturing resin-sealed semiconductor devices, in which at least a part of the inner surface of the recess of the upper mold is formed with a rough satin finish, and the inner surface of the lower mold is formed with a fine satin finish. Type. 9. The mold according to claim 7, wherein a recess is formed around the bottom surface of the recess of the lower mold.