JP2785770B2 - Method and apparatus for manufacturing resin-encapsulated semiconductor device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to the manufacture of semiconductor devices .
More particularly, the present invention relates to a method for manufacturing a resin-sealed semiconductor device and an apparatus for manufacturing the same.

[0002]

2. Description of the Related Art In recent years, with the trend toward multifunctional, large-scale, and miniaturized semiconductor elements, the pitch of bonding pads has been reduced and the number of pins has been increased. In addition, packages are also becoming thinner, and accordingly, thinner lead frames and thinner sealing resins are being promoted. In the resin encapsulation process of such a thinned package, the pressure of the inflowing resin in the cavity increases, and the bonding wire and die pad move (so-called wire flow, die pad shift phenomenon). Occurs, which leads to a decrease in yield and reliability.

In order to cope with the narrowing of the bonding pad pitch and the wire flow in the resin encapsulation process, TAB is used instead of the bonding wire method.
(Tape Automated Bonding) TAB lead connection using a method has been adopted. Further, as a means for suppressing the die pad shift, a method of fixing a die pad by vacuum suction or the like during a resin sealing step (transfer molding step) has become common.

FIG. 5 is a cross-sectional view for explaining a conventional transfer molding method for fixing a die pad. A molding die for semiconductor encapsulation is composed of an upper die 2 and a lower die 1. A cavity 5 is provided between the upper mold 2 and the lower mold 1. Further, an exhaust hole 6 for fixing the semiconductor element is provided in the lower mold 1, and an exhaust pipe 7 that is in contact with a die pad of a lead frame is fixed to a tip of the exhaust hole 6 on the cavity side. While the upper mold 2 is retracted upward, a semiconductor device having the semiconductor element 3 mounted on the die pad of the lead frame 4 is transferred onto the lower mold 1. Although not shown, the pad on the semiconductor element and the inner lead of the lead frame 4 are connected by a conductor such as a TAB lead.

After the semiconductor device is mounted at a predetermined position on the lower mold 1, the upper mold 2 descends to hold the lead frame 4 between the upper and lower molds as shown in FIG. The die pad is fixed by vacuum suction through the tube 7. Thereafter, although not shown, a sealing resin is injected from a pot portion provided in the mold, and the sealing resin is filled into the cavity 5 through the runner gate.
At this time, in packages with thinner and higher density,
Although the resin flow path in the cavity is narrow, the semiconductor element and the die pad receive a strong resin pressure. However, since the die pad is fixed by vacuum suction, the semiconductor element 3 is sealed at a predetermined position in the cavity 5 without displacement. Is stopped.

After the cavity is completely filled with resin and a predetermined curing time of the sealing resin has passed, the space between the upper mold 2 and the lower mold is opened, and the semiconductor element 3 and the lead, which have been completely sealed with resin, are opened. When the semiconductor device including the frame 4 is taken out, a series of sealing steps is completed. In the semiconductor device formed in this manner, the portion of the rear surface of the die pad where the exhaust pipe 7 is in contact is exposed without being sealed.

Further, Japanese Utility Model Publication No. 2-7469 (Japanese Utility Model Application Laid-Open No. 61-39950) discloses that the back surface of a die pad is sealed with a rubber-like resin in order to prevent a gap between the die pad and the sealing resin. It has been proposed. That is, as shown in FIG. 6, the semiconductor element 12 is mounted on the die pad 11, and the bonding pad on the semiconductor element 12 and the inner lead portion of the external lead 14 are connected by the thin metal wire 13, and then the sealing resin is formed. 15 and rubbery resin 16
And sealing is performed. Here, the rubber-like resin 16 seals a region beyond the die pad 11 and including the inside of the external lead 14.

[0008]

In the conventional molding die shown in FIG. 5, after the cavity 5 excluding the contact portion of the exhaust pipe 7 is filled with the sealing resin, the exhaust pipe contacts the lower surface of the die pad. The portion cannot be filled with the resin, and the lower surface of the die pad remains exposed. Therefore, moisture easily penetrates into the package along the interface between the die pad and the sealing resin through the exposed portion, and the erosion of the semiconductor element 3 may cause electrical characteristic failure. This poor electrical characteristic is rarely generated in the initial stage after the completion of the manufacturing process, and occurs when the final product is used in an environment with high humidity after being incorporated into the final product. As a test item for evaluating the deterioration under high humidity, there is a PCT (Pressure Cooker Test; durability test under a high-temperature, high-humidity environment), but the pass rate in this test was low in conventional products.

On the other hand, in the semiconductor device shown in FIG. 6, a rubber-like resin having low moisture resistance is used as a sealing resin, and a wide area beyond a die pad portion is sealed with this resin. The moisture resistance was low and the PCT also produced many rejected products. The present invention has been made in view of such problems of the conventional example, and an object of the present invention is to ensure high moisture resistance in a high-density, thin semiconductor device. .

[0010]

According to the present invention, there is provided a method of manufacturing a resin-encapsulated semiconductor device, comprising the steps of: forming a lead frame having a semiconductor element mounted on a die pad;
Disposing the die pad in a cavity and supporting and fixing the die pad by a tubular suction means;
A first resin sealing step of resin-sealing the entire portion except for the portion occupied by the tubular suction means while maintaining the support of the die pad by the above-described method, and releasing the support of the die pad by the tubular suction means.
And a second resin sealing step of sealing the portion occupied by the tubular suction means using the same resin as the resin used in the first resin sealing step. It is characterized by:

According to another aspect of the present invention, there is provided an apparatus for manufacturing a semiconductor device, comprising: an exhaust hole which is opened on the back surface of a die pad of a lead frame; and a plunger shelter which communicates with the exhaust hole. A first mold provided with: a second mold capable of forming a cavity for accommodating a semiconductor device by combining the first mold with the first mold; Attached to the opening portion that is opened on the back surface of the die pad, during the main resin sealing step of filling most of the cavity, abuts against the back surface of the die pad of the lead frame, and the main resin sealing step An exhaust pipe that retreats into the first mold after completion, and is evacuated to the plunger shelter during the main resin sealing step, and after the main resin sealing step, the resin is sealed by the resin sealing. Formed die package A plunger that supplies a resin for filling the opening on the back surface of the plunger into the cavity, a resin supply unit that supplies a resin tablet onto the plunger evacuated to the plunger shelter,
It is characterized by having.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a sectional view for explaining an embodiment of the present invention. As shown in the figure, a semiconductor element 3 is mounted on a die pad of a lead frame 4. Although not shown, the pads on the semiconductor element 3 and the inner leads of the lead frame are connected by, for example, TAB leads. This semiconductor element is sealed in, for example, a QFP type package by a main sealing resin 10a made of an epoxy resin or the like. As described above, the sealing resin has an opening for exposing the back surface of the die pad. Have been. Therefore, in the present invention, this opening is filled with an embedding sealing resin 10b made of the same kind of resin as the main sealing resin 10a.

In the sealing step using the main sealing resin, for example, the embedded sealing resin 10b is mainly sealed by using a plunger that is waiting at a plunger shelter connected to an exhaust hole of a sealing mold. It is filled in the opening of the sealing resin 10a. At this time, since the inside of this opening is maintained in a reduced pressure state by performing vacuum suction, the inside of the opening can be satisfactorily embedded without generating voids.

In the package formed in this manner, since the opening formed in the main sealing resin 10a is filled with the same kind of resin, moisture does not enter the package through the opening, and moisture resistance is reduced. Shows characteristics equivalent to those of a resin package having no opening.

[0015]

Next, embodiments of the present invention will be described with reference to the drawings. [First Embodiment] FIG. 2 is a cross-sectional view of a molding die for explaining a first embodiment of the present invention, and FIG.
FIG. 2B shows a state before the resin sealing step, and FIG. 2B shows a state after the sealing step with the main sealing resin is completed. FIG.
As shown in FIG. 1A, an exhaust hole 6 is provided in the lower die 1, and a plunger 8 is accommodated in an opening portion connected to the exhaust hole. The exhaust hole 6 is opened below the semiconductor element 3, and an exhaust pipe 7 that can move up and down is mounted at the tip of the exhaust hole below the semiconductor element 3.

In the resin sealing step, the lead frame 4
A semiconductor device having a semiconductor element 3 mounted thereon is mounted on a lower mold 1.
After being mounted on the lead frame 4, the lead frame 4 is sandwiched between the upper mold 2 and the lower mold 1, and the semiconductor element is held at a predetermined position in the cavity 5. Then, air is exhausted from the exhaust hole 6 using a vacuum pump or the like, and the lower surface of the die pad is brought into close contact with the exhaust pipe 7. In this state, sealing is performed by injecting a molten resin into the cavity. Thereafter, a resin tablet 9 is supplied onto the plunger 8 by a resin supply means (not shown). After sealing with the main sealing resin 10a, the exhaust pipe 7 is housed in the lower mold 1 as shown in FIG. The resin is injected using the plunger 8 provided in the lower mold 1. At this time, since the opening is kept in a reduced pressure state,
Filling can be performed without generating voids (unfilling failure). Thereafter, the interior of the exhaust hole 6 is returned to normal pressure, the upper mold 2 and the lower mold 1 are opened, and the semiconductor device is taken out.

As for the resin tablet 9, one part of the lower mold 1 is insulated from the mold and stored in a room temperature, and after the sealing with the main sealing resin is completed, the stored tablet is planed. It can be supplied on a jar 8. By using the same resin as the main sealing resin 10a to fill the opening, it is possible to prevent the occurrence of cracks due to the difference in thermal expansion coefficient and to form a highly reliable package.

[Second Embodiment] FIG. 3 is a sectional view of a molding die for explaining a second embodiment of the present invention, and FIG. FIG. 3B shows the state at the stage when the sealing step with the main sealing resin is completed. This embodiment differs from the first embodiment in that the exhaust hole 6 is branched into a plurality of parts below the die pad, and the exhaust pipes 7 that can move up and down are attached to the branched exhaust holes. The other points and the sealing method are the same as those in the previous embodiment. In this embodiment, a plurality of (for example, four) exhaust pipes 7 are arranged in a portion in contact with the lower surface of the die pad of the lead frame, so that a large semiconductor element can be stably fixed by suction and sealed. it can.

[Third Embodiment] FIG. 4 is a sectional view of a molding die for explaining a third embodiment of the present invention, and shows a state before a resin sealing step. In this example,
A plurality of vertically movable exhaust pipes 7 are provided below the die pad of the lead frame 4, an exhaust hole 6 is provided for each exhaust pipe, and a plunger 8 is also provided for each exhaust pipe. The difference is that the other points are the same as those of the other embodiments. In the second embodiment shown in FIG. 3, it is possible that the resin is not evenly supplied to the plurality of exhaust pipes. However, by providing a plunger for each exhaust pipe as in the present embodiment, each of the openings is formed. And the resin can be stably injected.

In the resin-encapsulated semiconductor device formed in this manner, moisture can be prevented from entering through the opening formed in the main encapsulation resin, so that it can be used for a long time in a high-temperature and high-humidity environment. No deterioration in the use of
High reliability can be ensured. Table 1 shows the results of 500 hours of PCT performed on the semiconductor device formed in this manner and the semiconductor device formed by the conventional mold shown in FIG. 5 using 20 samples each.

[0021]

[Table 1]

[0022]

As described above, the method of manufacturing a resin-encapsulated semiconductor device according to the present invention provides a method of manufacturing a resin-encapsulated semiconductor device , which is performed by a vacuum suction exhaust pipe for preventing a die pad shift occurring during a resin encapsulation process. since part is its embedding free ones by the material of the sealing resin and the same kind, and it is possible to prevent moisture from entering through the opening of the sealing resin, the electrical characteristics degradation due to erosion of the semiconductor element Can be suppressed.

Further, according to the manufacturing apparatus of the present invention, a plunger for injecting a resin into an opening formed in the main sealing resin is provided in a mold, and the plunger is used to evacuate the die pad for evacuation. In this state, the resin can be injected, so that the resin can be embedded without voids.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a semiconductor device illustrating an embodiment of the present invention.

FIG. 2 is a sectional view of a molding die for explaining the first embodiment of the present invention.

FIG. 3 is a cross-sectional view of a molding die for explaining a second embodiment of the present invention.

FIG. 4 is a cross-sectional view of a molding die for explaining a third embodiment of the present invention.

FIG. 5 is a cross-sectional view of a conventional molding die.

FIG. 6 is a cross-sectional view for explaining another conventional example.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 lower mold 2 upper mold 3 semiconductor element 4 lead frame 5 cavity 6 exhaust hole 7 exhaust pipe 8 plunger 9 resin tablet 10a main sealing resin 10b embedded sealing resin 11 die pad 12 semiconductor element 13 metal wire 14 Lead 15 Sealing resin 16 Rubbery resin

Claims (2)

(57) [Claims] 1. A semiconductor device is mounted on a die pad.
Disposing a lead frame in the cavity, supporting and fixing the die pad by a tubular suction means ,
A <br/> first resin sealing step of the entire resin-sealing except for the portion occupied by the tubular suction means while maintaining the support of the die pad by suction means tubular die according to the adsorption unit of said tubular
A step of releasing the support of the pad, and a second resin sealing step of sealing the portion occupied by the tubular suction means using the same resin as the resin used in the first resin sealing step. And a method of manufacturing a resin-encapsulated semiconductor device. 2. A first mold having therein an exhaust hole opened on the back surface of a die pad of a lead frame, a plunger shelter communicating with the exhaust hole, and the first mold. A second mold capable of forming a cavity for accommodating a semiconductor device in combination with the second mold, wherein the second mold is mounted on an opening formed on the back surface of a die pad of the exhaust hole of the first mold. An exhaust pipe that abuts on the back surface of the die pad of the lead frame during the main resin sealing step of filling most of the cavity and retreats into the first mold after the main resin sealing step is completed; During the main resin sealing step, the plunger is evacuated to the shelter, and after completion of the main resin sealing step, a resin for filling the opening on the back surface of the die pad formed by the resin sealing is placed in the cavity. Plunge to supply And a resin supply means for supplying a resin tablet onto the plunger evacuated to the plunger shelter.