JPH07226460A - Resin sealed semiconductor device and its manufacturing method - Google Patents

Abstract

PURPOSE:To manufacture the resin sealed semiconductor device and its manufacturing method causing no cracking at all even if the thermal stress such as that in the reflow soldering step is imposed on the semiconductor device. CONSTITUTION:In the manufacturing method, an elastic resin after setting step is cast-set in planar shape using a frame mold to form a resin plate 6 on a main surface whereon a semiconductor element 4 on an island 2 is not mounted.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a resin-encapsulated semiconductor device and a method of manufacturing the same, and more particularly to a resin-encapsulated semiconductor device having improved resistance to cracking of an encapsulating resin and a method of manufacturing the same.

[0002]

2. Description of the Related Art In recent years, with the miniaturization and high performance of electronic equipment, the miniaturization and thinning of the entire mounting circuit has been advanced. Along with this, the surface mount type semiconductor package has been widely used instead of the conventional lead insertion type. Generally, the method of mounting the surface mount type component on the printed wiring board is to supply cream solder to the component mounting land of the printed wiring board by printing etc., align the lead of the component and mount it. So-called reflow soldering is employed in which solder is melted and attached by heating with far infrared rays or hot air from above and below the plate.

In reflow soldering, compared with flow soldering which has been conventionally used for soldering lead insertion type parts, the mounted parts are heated directly, so that the temperature of the parts themselves rises, and therefore various kinds of parts are used. There is a problem with. For example, in the case of a resin-encapsulated semiconductor device, if the encapsulating resin absorbs moisture, the absorbed moisture may vaporize, and cracks may occur in the encapsulating resin. The situation during this period is shown in FIGS.
This will be described with reference to FIG.

FIG. 9 is a partially cutaway perspective view schematically showing the structure of a general resin-encapsulated semiconductor device, and FIG. 10 is a sectional view taken along line AA of FIG. 21 is a lead,
A semiconductor element 24 is mounted on the island 22 via a conductive mount material 23. The lead 21 and an electrode portion (not shown) of the semiconductor element 24 are connected by a bonding wire 25, and the whole is molded (sealed) with a sealing resin 26.

FIG. 11 is a cross-sectional view explaining the mechanism of cracking in the sealing resin. The water vapor that has entered the sealing resin 26 from the outside air is condensed and liquefied in the minute gap existing at the interface between the sealing resin 26 and the island 22. The liquefied water expands rapidly under the high temperature during reflow. Therefore, a large water vapor pressure is applied to the interface between the sealing resin 26 and the island 22, and the interface is peeled off to form the gap 27.
If the amount of moisture absorption of the sealing resin 26 is large, the interface peeling leads to the crack 28 of the resin.

Therefore, as shown in FIG. 12, it has been proposed to form an opening in the lower portion of the island 22 of the sealing resin 26 to fill the rubber-like resin 29. The rubber-like resin 29 improves the adhesion to the island 22 and prevents the retention of water. For example, even if a gap is generated between the rubber-like resin 29 and the island 22 and moisture stays, and the moisture vaporizes and expands during heating such as solder reflow, the rubber-like resin has large flexibility and absorbs pressure. It means that cracks will not occur.

However, the rubber-like resin 29 and the sealing resin 2
6 does not necessarily have sufficient adhesiveness with 6, and when pressure is applied to the rubber-like resin 29 due to vaporization of water, the adhesive force between the rubber-like resin 29 and the sealing resin 26 is weakened to form a ventilation path. In the extreme case, the rubber-like resin 29 may drop off.

[0008]

As described above, the resin-encapsulated semiconductor device has a problem that cracks are generated in the encapsulating resin during reflow soldering. As a countermeasure against this, an idea was made to provide an opening below the island of the sealing resin and to fill it with a rubber-like resin, but the adhesiveness between the sealing resin and the rubber-like resin is not always sufficient, and the interface between the two does not flow. There was a possibility that channels would be formed and the rubber-like resin would fall off.

The present invention has been made in view of the above circumstances, and is a resin-sealed mold having good moisture resistance so that cracks do not occur in the sealing resin even when thermal stress is applied during reflow soldering. It is intended to provide a semiconductor device.

[0010]

In order to achieve the above object, according to the present invention, a semiconductor element, an island on which the semiconductor element is mounted, and a plurality of leads electrically connected to an electrode portion of the semiconductor element are provided. , An elastic resin plate adhered and formed below the main surface of the island on which the semiconductor element is not mounted, and the semiconductor element, the island, and the lead are sealed, and a side surface and a peripheral edge portion of the resin plate are formed. It is characterized by comprising a sealing resin for adhesive coating.

In addition, as a second invention, a semiconductor element,
The island on which the semiconductor element is mounted, a plurality of leads electrically connected to the electrode portion of the semiconductor element, and the island that is formed below the main surface of the island on which the semiconductor element is not mounted and has unevenness on its side surface It is characterized by comprising a resin plate, a sealing resin that seals the semiconductor element, the island, and the lead, and that adheres a side surface of the resin plate. Furthermore, the manufacturing method of the present invention,
Mounting the semiconductor element on the island of the lead frame, electrically connecting the electrodes of the semiconductor element and the leads of the lead frame, and applying elastic after curing to the main surface of the island on which the semiconductor element is not mounted. A step of casting a resin having a plate shape using a frame mold and curing the resin to form a resin plate, a semiconductor resin, the island, the lead, and a sealing resin except at least a central portion of the resin plate. And a step of sealing.

[0012]

As described above, in the first aspect of the invention, the elastic resin plate is previously provided under the back surface of the island, and the side surface and the peripheral portion of the resin plate are adhesively covered when the resin is sealed. The adhesion distance between the resin plate and the sealing resin is increased to prevent the generation of air passages, and the peripheral edge portion of the resin plate is covered with the sealing resin to prevent the resin plate from falling off.

In the second aspect of the present invention, since the side surface of the elastic resin plate provided under the back surface of the island is provided with the unevenness, the adhesion distance between the resin plate and the sealing resin becomes long and the generation of the air passage is prevented. At the same time, the unevenness of the resin plate prevents the resin plate from falling off.

Further, in the manufacturing method of the present invention, a frame mold is provided on the back surface of the island, and after curing, a resin having elasticity is cast and cured to form a resin plate. Therefore, the island and the resin plate are directly bonded and bonded. You can get enough power.

[0015]

Embodiments of the present invention will now be described with reference to the drawings. FIG. 1 is a sectional view schematically showing a resin-sealed semiconductor device according to the first embodiment of the present invention. In FIG. 1, 1 is a lead and 2 is an island, which are integrally formed in a lead frame made of Fe-Ni alloy or Cu. A semiconductor element 4 is mounted on the island 2 via a mount material 3 such as Ag paste or solder.
The semiconductor chip 4 and the lead 1 are electrically connected by a bonding wire 5. On the lower surface of the island 2, a resin plate 6 made of a rubber-like resin (for example, silicone rubber, urethane resin, polyimide resin, or the like) having good adhesiveness and elasticity is formed. Further, these components are sealed with a sealing resin 7 such as an epoxy resin. At this time, the sealing resin 7 is molded so as to have an opening without covering the central portion of the resin plate 6. Therefore, the resin plate 6
Is bonded to the sealing resin on its side surface and peripheral portion, and slipping or falling off is prevented. Since the surface of the resin plate 6 is one step lower than the surface of the sealing resin 7, even if the central portion of the resin plate 6 expands due to vaporization of water, it protrudes from the surface of the sealing resin 7. It also has a unique structure. When mounted on a printed wiring board or the like, it is effective in applications where securing a gap with the printed wiring board poses a problem.
When silicone rubber is used, it has a high water vapor permeability, and therefore has the effect of preventing swelling itself.

This resin-sealed semiconductor device can be manufactured as follows. That is, after mounting the semiconductor element 4 on the island 2 of the lead frame with the mount agent 3 such as Ag paste, the bonding wire 5 is provided between the electrode portion (not shown) of the semiconductor element 4 and the lead 1 by means such as ultrasonic bonding. Connecting.

Next, the lead frame after this bonding is set in a jig as shown in FIG. 2, and a silicone rubber (for example, TSE325 and TS manufactured by Toshiba Silicone Co., Ltd.) is set.
E3250) is cast to mold the resin plate 6. In FIG. 2, reference numeral 8 denotes a lead frame support, which has a U-shaped cross section in order to avoid contact between the semiconductor element 4 and the bonding wire 5. Reference numeral 9 is a frame for casting having an opening in contact with the island 3. FIG. 3 is a perspective view showing the support base 8, the lead frame 10, and the frame die 9 separately.
(A) is a frame mold 9, (b) is a lead frame 10, (c)
Indicate the supports 8, respectively, and they are stacked in this order. The lead frame 10 schematically shows four lead frames in which four semiconductor elements can be mounted.

In FIG. 3 (c), the projection 11 is used for fixing or positioning the lead frame 10 and the casting frame 9. Further, as shown in FIG. 3A, the casting frame 9 is provided with an opening 12 corresponding to the island 2. The receiving hole 13 corresponds to the protrusion 11 of the support base 8 and fixes or positions the casting frame 9.

The lead frame 10 is set on such a support 8 with the semiconductor element side facing down. At this time, the feed hole 14 of the lead frame 10 can be aligned with the protrusion 11 of the support base 8. Subsequently, the casting frame 9 is set in the opening 12 so as to fit the island 2. At this time, the protrusion 11 can be inserted into the receiving hole 13 to serve as a guide. Subsequently, silicone rubber is injected into the opening 12 up to the surface of the casting frame 9 and cured. Then, the casting frame 9 is removed to form the resin plate 6 under the island 2.

Next, the lead frame 10 removed from the support base 8 is set in a transfer mold, and epoxy resin transfer molding is performed to perform resin sealing. At this time, if a part of the lower die 15 of the molding die is in contact with the resin plate 6 as shown in FIG. 5, a resin-sealed semiconductor device as shown in FIG. 1 is obtained. Note that FIG.
16 is an upper mold.

Next, a second embodiment of the present invention will be described with reference to the sectional view of FIG. Since the basic structure of FIG. 6 is almost the same as that of FIG. 1, the same parts are designated by the same reference numerals and the description of the structure is partially omitted. The resin plate 6'of this embodiment is provided with unevenness on its side surface, which increases the contact area with the sealing resin 7 and strengthens the locking force of the resin plate 6 '. Therefore, it is not necessary to cover the peripheral edge of the resin plate 6'with the sealing resin 7, which is an effective configuration when thinness is required. Although a plurality of irregularities is provided in FIG. 6, it may be one.

This resin type semiconductor device can be manufactured as follows. The procedure is the same as that of the first embodiment up to the point where the mounted and bonded lead frame is set on the support base 8 as shown in FIG. The casting frame 9'is divided into two frames 9'a and 9'b as shown in the perspective view of FIG. 8, which are set together on the lead frame. The island 2 is surrounded by the half openings 12'a and 12'b to form openings. A groove 17 is dug in the wall surface of this opening,
The injected silicone rubber fills the groove 17 and hardens.
After the silicone rubber has hardened, the casting frames 9'a and 9'b are opened to the left and right, and a resin plate 6'having a groove on the side surface is formed on the island 2.

In the next transfer molding step, the resin-sealed semiconductor device shown in FIG. 6 is obtained by molding so that the resin plate 6'contacts the lower mold of the molding die. The thus-fabricated semiconductor devices of the two examples were subjected to infrared reflow (maximum temperature 240 ° C.) known as the most severe reflow method, but no resin cracks, resin plate slips, or falling off occurred.

Although the embodiments of the present invention have been described above, the present invention is not limited to the above embodiments, and various modifications can be made without departing from the spirit of the invention. For example, in the above embodiment, an example of wire bonding was explained, but TAB (Tape
The Automated Bonding method can also be used.

The resin plate 6 or 6'may be separately prepared in advance and bonded to the back surface of the island 2 with an adhesive or the like. However, if the resin plate is directly formed on the island 2, the two are directly bonded. However, the above-mentioned manufacturing method is preferable because a stronger adhesive force can be obtained.

[0026]

As described above, according to the present invention, since the resin plate having a strong adhesive force and elasticity is provided under the island, moisture does not accumulate under the island and the vaporization thereof prevents the sealing resin from cracking. Even if water is collected, the resin plate has elasticity so that it can absorb stress due to vaporization.
Further, since the resin plate is covered with a sealing resin at the periphery thereof or the side surface of the resin plate is provided with irregularities to enhance the locking force of the sealing resin, the resin plate will not fall off due to the pressure due to vaporization.
In addition, since the adhesive path between the resin plate and the sealing resin becomes long due to the coating or the unevenness, a ventilation path is not formed between the both and the humidity resistance is not deteriorated, and the reliability is greatly improved.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of essential parts of a resin-sealed semiconductor device according to a first embodiment of the present invention.

FIG. 2 is a sectional view illustrating a method for manufacturing a resin plate according to the first embodiment of the present invention.

3 is an exploded perspective view showing the manufacturing method of FIG.
(A) shows a frame type, (b) shows a lead frame, (c) shows a support stand.

FIG. 4 is a sectional view illustrating a transfer mold according to the first embodiment of the present invention.

FIG. 5 is a cross-sectional view of essential parts of a resin-sealed semiconductor device according to a second embodiment of the present invention.

FIG. 6 is a sectional view illustrating a method of manufacturing a resin plate according to a second embodiment of the present invention.

FIG. 7 is a perspective view of a frame mold used in the manufacturing method according to the second embodiment of the present invention.

FIG. 8 is a partially cutaway perspective view showing a typical example of a resin-encapsulated semiconductor device.

FIG. 9 is a cross-sectional view of essential parts of a resin-sealed semiconductor device according to a conventional technique.

FIG. 10 is a cross-sectional view illustrating a resin crack generation mechanism in a conventional resin-sealed semiconductor device.

FIG. 11 is a cross-sectional view of essential parts of another resin-encapsulated semiconductor device according to the related art.

[Explanation of symbols]

 1 ... Lead 2 ... Island 3 ... Mounting agent 4 ... Semiconductor element 5 ... Bonding wire 6 ... Resin plate 7 ... Sealing resin

Claims (3)

[Claims] 1. A semiconductor element, an island on which the semiconductor element is mounted, a plurality of leads electrically connected to an electrode portion of the semiconductor element, and an island below the main surface of the island on which the semiconductor element is not mounted. It is characterized by comprising a formed elastic resin plate, and a sealing resin that seals the semiconductor element, the island, and the lead, and that adhesively coats the side surface and the peripheral portion of the resin plate. Resin-sealed semiconductor device. 2. A semiconductor element, an island on which the semiconductor element is mounted, a plurality of leads electrically connected to an electrode portion of the semiconductor element, and an island below the main surface of the island on which the semiconductor element is not mounted. A resin characterized by comprising a resin plate which is formed and has irregularities on its side surface, and a sealing resin which seals the semiconductor element, the island and the lead, and adheres the side surface of the resin plate. Sealed semiconductor device. 3. A step of mounting a semiconductor element on an island of a lead frame, and a step of electrically connecting an electrode of the semiconductor element and a lead of the lead frame,
A step of casting a resin having elasticity after curing into a plate shape using a frame mold and curing the resin on the main surface of the island on which the semiconductor element is not mounted; and forming the resin plate, the semiconductor element, the island, and the leads. And a step of sealing with a sealing resin except at least the central portion of the resin plate, the method for manufacturing a resin-sealed semiconductor device.