JPH0679750A - Method for transfer molding - Google Patents

Abstract

PURPOSE:To shorten a time for melting a tablet by a method wherein a hollow part is provided in the tablet to be charged in a pot, a projection provided on a plunger is put in the hollow part and the tablet is heated both from outside and the central part. CONSTITUTION:A tablet 1 to be charged in a pot 8 is formed of a cylindrical hollow main body part 2 and a through hole 3 provided coaxially with the main body part. A projection 16 of an outside diameter fit with the through hole 3 is provided on a plunger 13 so provided as to correspond to the tablet 1 and the length of the projection is equal substantially to the length in the axial direction of the through hole 3, while heaters 17 are provided inside the main body part 15 of the plunger and the projection 16. When the tablet 1 is pressed by the plunger 13, accordingly, the tablet 1 is heated preliminarily by heaters 12 provided inside a top force 4 and a bottom force 5 and also both of the inner and outer peripheral surfaces of the tablet 1 are heated by the heaters 12 and 17. Thereby the heated surface area of the tablet 1 is increased and a time required for molten resin to be filled up in a cavity 7 is shortened.

Description

Detailed Description of the Invention

 [Object of the Invention]

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a transfer molding method used in, for example, a semiconductor encapsulation process.

[0002]

2. Description of the Related Art In general, resin encapsulation of a semiconductor device is a material obtained by adding a filler such as silica to an epoxy resin, and is encapsulation-molded using a transfer molding machine. And
The molding shot is mainly made of a large number such as 12, 48, 64 and the like. This transfer molding machine is one in which an epoxy resin is injected and curing molding is performed in a state where a mold in which a lead frame to which a semiconductor chip to be sealed is fixed is arranged is closed. That is, a resin tablet made of epoxy resin preliminarily formed into a tablet shape is subjected to high-frequency preheater at 60 ° C to 100 °
Preheat to C and put in the pot. Then, the resin heated by the heater of the mold is pressed by the plunger to flow, fills the cavity through the runner and the gate, and is cured and molded in about 2 to 3 minutes.

By the way, as shown in FIG. 6, a conventional tablet A has a cylindrical shape.
It is loaded into a cylindrical pot B. Then, the tablet A in the pot B is pressed by the plunger C heated to about 180 ° C to 200 ° C. In this case, heat is transferred to the tablet A via both end surfaces and the outer peripheral surface of the tablet A, and the heated tablet A is melted in the pot B. The shorter the time from the loading of the tablet A into the pot B to the melting, the shorter the time is for the purpose of improving the molding efficiency (cycle time). However, the amount of heat transfer to the tablet A is limited because it depends on the surface area of the tablet A itself. Further, since heat transfer to the tablet A is from the outer surface thereof, the temperature distribution becomes uneven in the melted state of the tablet A.
As a result, it is also a cause of defective molding such as generation of voids, generation of cracks, and peeling. Further, even if the heating temperature is increased in order to shorten the melting time of the tablet A in the pot B, it is not a drastic solution due to molding defects such as generation of voids and generation of cracks.

[0004]

As described above, various attempts have been made to shorten the melting time of tablets in the pot for the purpose of improving the molding efficiency, but none of them have been successful.

The present invention has been made in view of the above circumstances, and an object of the present invention is to solve the technical problems of the above-mentioned conventional transfer molding method and to provide a transfer molding method capable of improving the molding efficiency. To do. [Constitution of Invention]

[0006]

According to the transfer molding method of the present invention, a hollow portion is provided in a tablet loaded in the pot, and a projection portion provided on a plunger is fitted into the hollow portion to form the inside of the pot. The tablet is heated from both the outside and the center.

[0007]

According to the transfer molding method having the above structure, the melting time of the tablet is shortened, the cycle time can be shortened, and the productivity can be improved. Since the temperature of the resulting molten resin becomes uniform, the unevenness of the viscosity is eliminated, and the effect of suppressing the occurrence of voids, cracks, etc. is achieved, and the density of the resin portion of the molding target becomes uniform, so that the molding quality is improved. It is also possible to improve the reliability of the object to be molded.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described in detail below with reference to the drawings.

FIG. 1 shows a tablet 1 used in the transfer molding method of this embodiment. The tablet 1 includes a main body 2 having a hollow cylindrical shape and a through hole 3 provided coaxially with the main body 2. The material of the main body 2 is, for example, a phenol novolac type epoxy resin, a curing agent such as amines, a curing accelerator such as nitrogen-containing compounds, a flexing agent such as silicone oil, for example fused silica. Etc., a coupling agent such as epoxysilane, a release agent such as wax, and the like.

On the other hand, FIG. 2 shows a transfer molding apparatus M used in the transfer molding method of this embodiment. This transfer molding apparatus M stores a mold part 6 composed of an upper mold 4 and a lower mold 5, a plurality of cavities 7 formed by the mold part 6, and the tablet 1 provided in the lower mold 5. Corresponding to the pot 8 that melts, the runner 10 that guides the molten resin 9 (see FIG. 3) generated by melting the tablet 1 in the pot 8 to the cavities 7, and the runners 10 to the respective cavities 7. Gate 11 for guiding the branched and melted molten resin 9 to the cavity 7 ...
A heater 12 provided in the upper mold 4 and the lower mold 5 for heating the tablet 1 in the pot 8, a plunger 13 slidably fitted in the pot 8 and a plunger for driving the plunger 13 in its axial direction. And a drive mechanism (not shown). Thus, the plunger 13 has a cylindrical body portion 15 slidably fitted in the inner diameter portion of the pot 8.
And a columnar protrusion 16 having a diameter such that the protrusion is provided at the lower end of the main body 15 and fits into the through hole 3, the main body 1.
5 and a heater 17 provided inside the protrusion 16. The axial length of the protrusion 16 is set to be substantially equal to the axial length of the through hole 3. That is, the tablet 1 loaded in the pot 8 has the inner peripheral surface 1a thereof.
The outer peripheral surface 1b is heated from both inside and outside (see the arrow in FIG. 2). Next, the transfer molding method of this embodiment will be described using the tablet 1 and the transfer molding apparatus M.

First, the tablet 1 is preheated to 60 ° C. to 100 ° C. by a high-frequency preheater (not shown) and loaded in the pot 8. At this time, the upper mold 4, the lower mold 5 and the pot 8
In addition, the plunger 13 has heaters 12 and 17 beforehand.
By heating to about 180 ° C to 200 ° C. Then, as shown in FIG. 2, the tablet 1 in the pot 8 is
The outer peripheral surface 1b and the lower end surface 1c are heated from the pot 8 side, and the inner peripheral surface 1a and the upper end surface 1d are heated from the plunger 13 side. That is, the tablet 1 in the pot 8 is heated from both the outside and the inside. Therefore, in combination with the fact that the heating surface area of the tablet 1 is increased by the amount of the inner peripheral surface 1a and that the tablet 1 is also heated in the radial direction from the central portion, the time until the molten resin 9 is completely formed. And the temperature of the obtained molten resin 9 becomes uniform (see FIG. 3). Then, the molten resin 9 is extruded by the runner 10 as the plunger 13 descends, and then is filled into the cavities 7 via the gates 11. At this time, the semiconductor chip 2 is placed in the cavity 7.
0 is mounted in advance, the molten resin 9 filled in the cavities 7 is solidified, the semiconductor chip 20 is sealed, and the molding target 2 is molded.
Get one.

The molded body 21 molded in this way
Is molded by the molten resin 9 having a uniform temperature, the viscosity becomes uniform, and the molten resin 9 smoothly flows through the runner 10, the gates 11 ... And the cavities 7. Further, the density of the resin portion 22 of the molded body 21 after solidification becomes uniform, and the occurrence of voids and cracks is reduced,
The molding quality is improved. Further, since the melting time of the tablet 1 in the pot 8 is shortened, the cycle time can be greatly shortened from the conventional 60 seconds to 50 seconds.

In the above embodiment, the shape of the tablet 1 is a through cylinder, but the shape is not limited to this. For example, as shown in FIG. 4, a tablet 50 having a bottomed cylinder may be used. Correspondingly, as shown in FIG. 4, in the plunger 51, with the main body portion 52 thereof in contact with the tablet 50, the projection portion 52 has the tablet 50.
The shape and dimensions are such that they fit perfectly into the bottomed circular hole 53 without any gap. Further, as shown in FIG. 5, a tablet 61 having a tapered hole 60 having a draft may be used in order to improve releasability. As shown in FIG. 5, the projection 63 of the plunger 62 corresponding to the tablet 61 is formed such that the tip side is tapered with the smaller diameter side. Further, the shape of the hollow hole of the tablet is not limited to a circle, and may be a polygon such as a hexagon.

【The invention's effect】

In the transfer molding method of the present invention, a hollow portion is provided in the tablet loaded in the pot, and the projection portion provided on the plunger is fitted into the hollow portion.
The tablet in the pot is heated from both the outside and the center. By shortening the melting time of the tablet, it is possible to shorten the cycle time and help improve productivity. . Also, since the temperature of the molten resin made by melting the tablet becomes uniform,
The effect of suppressing the occurrence of voids, cracks, etc. is eliminated, and the density of the resin part of the molding target is uniform, which improves the molding quality and improves the reliability of the molding target. Can contribute.

[Brief description of drawings]

FIG. 1 is a perspective view showing a tablet used in a transfer molding method according to an embodiment of the present invention.

FIG. 2 is a configuration diagram of a transfer molding apparatus used in a transfer molding method according to an embodiment of the present invention.

FIG. 3 is an explanatory diagram of a transfer molding method according to an embodiment of the present invention.

FIG. 4 is a perspective view showing a tablet and a plunger used in a transfer molding method according to another embodiment of the present invention.

FIG. 5 is a perspective view showing a tablet and a plunger used in a transfer molding method according to another embodiment of the present invention.

FIG. 6 is an explanatory diagram of a conventional technique.

[Explanation of symbols]

1: Tablet, 3: Through hole (fitting hole), 6: Mold part,
7: cavity, 8: pot.

Claims (3)

[Claims] 1. A mold for forming a molten resin by heating a tablet loaded in a pot into a molten resin, and pressing the molten resin obtained in this molten resin forming step with a plunger fitted in the pot. In the molten resin forming step, the protrusion provided at the tip of the plunger is fitted into the fitting hole provided in the tablet in the molten resin forming step, A transfer molding method, wherein the tablet is heated from both the center side and the outside of the tablet via the plunger and the pot. 2. The transfer molding method according to claim 1, wherein the pot has a cylindrical shape, and a projecting portion is coaxially projected at a tip of a cylindrical plunger fitted into the pot. . 3. The transfer molding method according to claim 1, wherein the tablet has a cylindrical shape, and a fitting hole is formed so as to be coaxial with the protrusion of the plunger.