JPH04179242A - Sealing method for semiconductor element - Google Patents

Abstract

PURPOSE:To prevent a resin for sealing from being hardened while it is flowing inside a cavity by a method wherein a semiconductor element is sealed with the resin for sealing on a lead frame arranged inside a metal mold. CONSTITUTION:A lead frame 20 is arranged between an upper metal mold and a lower metal mold 12, 11 at a metal mold 30, for sealing, which is provided with a heating means and which has been kept at a molding temperature; a resin 5A for sealing use on the upper side is arranged at its upper part and a resin 9A for sealing use on the lower side is arranged at its lower part. When the upper and lower metal molds 12, 11 are closed, the resins 5A, 9A for sealing use at the upper and lower parts are heated and molded preliminarily to a shape which follows the lead frame 20 on which a semiconductor element 17 and bonding wires 18 have been mounted; the resins are filled into a cavity 32 in proper quantities without having a bad influence such as a stress deformation on the semiconductor element 17 and the bonding wires 18 which have been mounted on the lead frame 20. When the metal mold 30 for sealing use is fastened in a heated state, the resins for sealing use are melted and softened, seal the semiconductor element 17 and the bonding wires 18 and are molded as shown by 5B, 9B.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a method for sealing semiconductor elements (transistors, IC1LSIs, etc.).

Conventional technology Conventionally, a lead frame with a semiconductor element mounted thereon is placed in a cavity of a mold for sealing, and a pot provided in the mold is preheated for sealing. After charging the resin, a plunger that is slidably fitted into the pot is pushed to inject the heated and melted resin into the cavity through a runner gate under pressure. Resin encapsulation molding is being carried out.

Problems to be Solved by the Invention However, the above method has the following problems.

The first problem is that a pot, runner, and gate are required to inject molten resin into the cavity of the sealing mold, and the resin tends to harden and remain in the pot, runner, and gate. Therefore, not only is the resin wasted, but the mold becomes unusable when the resin is hardened and adhered, leading to an increase in costs. Furthermore, if the lead frame is thin and has a large area, the resin may harden while flowing within the cavity.

The second problem is that when resin sealing is performed on a lead frame and a semiconductor element that are electrically connected by bonding wires, the resin melted in the pot flows into the cavity. In this case, if the resin comes into direct contact with the bonding wire, stress deformation such as wire collapse may occur, resulting in a decrease in quality, and there is also the problem that the wires may become connected to each other.

The third problem is that during preheating, the air and moisture contained in the resin are not completely removed and remain, and when the molten resin flows through the runner gate during the sealing process, air may be drawn in. This may cause voids to occur in the molded product.

Means for Solving the Problems The first invention of the present application solves the first problem described above.In order to solve the above first problem, the semiconductor element is surrounded by a sealing resin around the lead frame on which the semiconductor element is attached. In the soil mounting method for semiconductor devices, in which the encapsulating resin is formed into a predetermined shape and fixed on the lead frame, the shape of the encapsulating resin that is finally formed on the lead frame is imitated. Using a preheating mold having a shaped cavity, the sealing resin is preheated and molded into a shape that matches the shape of the cavity, and the sealing mold obtained in this preheating step is used as the final into a sealing mold equipped with a cavity that matches the outer shape of the sealing resin formed on the lead frame,
It is characterized in that a semiconductor element is sealed with the sealing resin on a lead frame arranged in a mold.

Further, in order to solve the first and second problems described above, the second invention of the present application, in addition to the structure of the first invention, provides a sealing resin molded in the preheating step whose outer shape is on the lead frame. It is characterized in that it has a shape that substantially matches the outer shape of the sealing resin formed in the mold, and has a recessed part whose inner shape does not interfere with the semiconductor element and the bonding wire.

Furthermore, in the third invention of the present application, in order to solve the above first and third problems or the first to third problems, in addition to the structure of the above □ first invention or second invention. , the preheating mold is equipped with a suction device that sucks the air in the cavity, the preheating process is performed under reduced pressure, and when the semiconductor element is sealed with the preheated sealing resin, the sealing mold The mold clamping process is performed under reduced pressure.

According to the first invention of the present application, the sealing resin sealed in the preheating mold is preheated and softened, so that it conforms to the shape of the sealing resin that is finally formed on the lead frame. It is molded into a shape. The molded encapsulation resin is directly poured into the cavity of the encapsulation mold together with the lead frame on which the semiconductor element is mounted, and the semiconductor is molded with just the right amount of resin by clamping the encapsulation mold. It is possible to seal the element. This eliminates the need for pots, runners, and gates in the sealing mold, solving the problem of hardened resin remaining on the runners, gates, etc., and hardening the resin while it flows inside the cavity. It is also possible to solve the problem of

According to the second invention of the present application, the inner shape of the resin molded in the preheating step has a recess that does not interfere with the semiconductor element and the bonding wire.
When the resin is supplied into the mold for sealing, the resin does not exert any direct force on the semiconductor element and the bonding wire, and stress deformation such as wire collapse can be prevented.

According to the third invention of the present application, the preheating mold is provided with a suction device that sucks the air in the cavity, and since the preheating is performed under reduced pressure, there is no residual air present in the resin during the preheating. The air and moisture contained in the resin are suctioned and discharged from the resin, and the air and moisture in the resin after preheating and molding are reduced. After preheating, the resin put into the sealing mold is clamped under reduced pressure and heated to melt and harden, so that it is possible to prevent air from being drawn into the resin during clamping.

Embodiments Hereinafter, embodiments of the present invention will be described with reference to FIGS. 1 to 4. 1 and 2 show the preheating process, and FIGS. 3 and 4 show the sealing process.

FIG. 1 shows a first preheating mold 2a consisting of a pair of upper and lower molds 4a and 3a, and a molding cylinder 1 in which the upper mold 4a and the lower mold 3a are slidably fitted. has been done.

Heating means (not shown) are provided on both sides of the forming cylinder 1. The lower surface of the upper mold 4a has an upper cavity 14 of the upper mold 12 in the sealing mold 30 shown in FIG.
Four parts 22a corresponding to the four parts 22a are provided, and the four parts 22a
A fine communication hole 6a is provided for communicating with an external vacuum pump (not shown). On the other hand, a convex portion 23 shaped like the semiconductor element 17 and bonding wire 18 placed on the lead frame 20 is provided on the upper surface of the lower mold 3a. As shown in FIG. 1, the first preheating mold 2a follows the shape of the sealing resin 5B that will eventually be formed on the upper side of the lead frame 20 between the upper and lower molds 4a and 3a. The cavity 3] has a shape of a cavity 3], a.

FIG. 2 shows a pair of upper and lower molds 4b similar to those in FIG.
, 3b is shown. The lower surface of the upper mold 4b is provided with a sealing mold 3 as shown in FIG.
A recess 22b corresponding to the lower cavity 13 of the lower mold 11 in 0 is provided, and a fine communication hole 6b similar to the first preheating mold 2a is provided.
A convex portion 25 is provided on the upper surface. As shown in FIG. 2, the second preheating mold 2b has the shape of the sealing resin 9B that is finally formed on the lower side of the lead frame 20 between the upper and lower molds 41] and 31). It has a cavity 31b having a shape similar to the following.

Open the upper and lower molds 4a and 3a in FIG. 1, and put the sealing resin into the cavity 31a of the first preheating mold 2a.
The upper and lower molds 4a, 3a are closed, and then the resin is heated by a heating means to perform preliminary heating. During preheating, the vacuum pump is operated to cool the cavity 31a through the fine communication holes 6.
Suction the air inside to create a reduced pressure state. The resin gradually softens due to heating, and is pressure-molded by the upper and lower molds 4a and 3a, but the air that was generated in the resin is pushed out, and the water originally contained in the resin is is vaporized and suctioned and discharged from the communication hole 6a, so that the semiconductor element 7 and the upper sealing resin 5 having a recess shaped like the bonding wire 18 are removed from the air and moisture. ^ is formed.

A similar operation is performed using the second preheating mold 2b shown in FIG. 2 to mold the lower sealing resin 9^.

Next, the upper and lower sealing resins 5A and 9A are preheated and molded.
is supplied into the cavity 32 of the sealing mold 30 for the sealing process shown in FIG. 3 together with the semiconductor element 17 and the lead frame 20 to which the bonding wires 18 are attached while maintaining the preheating temperature. That is, the lead frame 20 is arranged between the upper and lower molds 12 and 11 of the sealing mold 30, which is equipped with a heating means (not shown) and maintained at a molding temperature (for example, 180° C.), and the lead frame 20 is placed above it. The upper sealing resin 5^ and the lower sealing resin 9A are placed below it.
10- will be done. When the upper and lower molds 12.11 are closed, the upper and lower sealing resins 5A and 9A are preheated and molded into a shape that follows the lead frame 2o on which the semiconductor element 17 and the bonding wire 18 are mounted, so that the lead frame Semiconductor element 17 and bonding wire 18 attached to 20
The cavity 32 is filled in just the right amount without causing any adverse effects such as stress deformation or the like. Then, as shown in FIG. 4, when the sealing mold 30 is clamped in a heated state, the sealing resin melts and softens and seals the semiconductor element 17 and bonding wire 18, as shown in FIG. 5B,
It is molded as shown in 9B. This sealing process is performed under reduced pressure by sealing the surrounding area and using an external vacuum pump (not shown), and when the mold is clamped, air is drawn into the resin, causing air to enter the molded product. Prevent from remaining.

Effects of the Invention According to the first invention of the present application, there is no need for a pot, runner, or gate in the mold for sealing molding, and the problem of hardened resin remaining on the pot, runner, or gate can be solved, and resin is not wasted. Since the use of the mold is omitted and maintenance of the mold becomes easy, costs can be reduced, and the problem of the conventional example in which the resin hardens while flowing within the cavity can be solved.

According to the second invention of the present application, in addition to the effects of the first invention, there is an effect that wire collapse of the bonding wire and contact between wires can be prevented.

According to the third invention of the present application, in addition to the effects of the first invention or the effects of the first and second inventions, it is possible to provide a high-quality product without the risk of void generation. .

[Brief explanation of drawings]

Figures 1 and 2 are sectional views of essential parts of a preheating device used in an embodiment of the present invention, Figure 3 is a sectional view showing the sealing molding process during resin injection, and Figure 4 is a mold clamping process. It is a sectional view showing the soil forming process at the time. 2a, 2b-----11 heating mold-11 = 5A, 9A, 5B, 9B... Sealing resin 6a, 6b.
・・・−・−・・・−−−1−～Minute communication hole 17・−−
1------・--------Semiconductor element 18-
・−・−−−−−−−−−−−−−−Bonding wire 20− ・−・−−−−−1−−−・Lead frame 30・−−−−−−・−−−− −−・・・・・・・・・
Sealing molds 31a, 31b--11-cavity 3
2−・−−−〜−−−−−−−−−−−−−−−− Cavity agent Patent attorney Masaru Ishihara

Claims (3)

[Claims] (1) For a lead frame on which a semiconductor element is attached, the periphery of the semiconductor element is covered with a sealing resin, and the sealing resin is formed into a predetermined shape and fixed onto the lead frame. In the sealing method, a preheating mold having a cavity shaped to follow the shape of the sealing resin that will eventually be formed on the lead frame is used to preheat the sealing resin and mold the mold to match the shape of the cavity. The sealing resin obtained in this preheating process is molded into a matching shape and is then molded into a sealing mold with a cavity that matches the outer shape of the sealing resin that will be finally formed on the lead frame. 1. A method for encapsulating a semiconductor element, comprising: supplying the resin into a mold, clamping the mold, and sealing the semiconductor element with the encapsulating resin on a lead frame arranged within the mold. (2) The sealing resin molded in the preheating process has an outer shape that approximately matches the outer shape of the sealing resin formed on the lead frame, and an inner shape that matches the semiconductor element and bonding wire. 2. The method for sealing a semiconductor element according to claim 1, wherein the semiconductor element has a shape having a concave portion that does not interfere with each other. (3) The preheating mold is equipped with a suction device that sucks the air inside the cavity, and when the preheating process is performed under reduced pressure and the semiconductor element is sealed with the preheated sealing resin, the 3. The method for sealing a semiconductor device according to claim 1, wherein the mold is clamped under reduced pressure.