JPS58161330A - Die structure for resin mold - Google Patents

Abstract

PURPOSE:To obtain the die structure for resin mold preventing defective external appearance and the generation of an internal void by forming the area of the opening of a main runner formed into a center block so that an area on the upstream side is made larger than that on the downstream side. CONSTITUTION:In a die 10, a center block 11 is arranged at the center, and vacity blocks 12 are disposed on both sides and brought mutually to a closely contacted state. A pot 14 is formed at an approximately center of the block 11, and tablets 18 manufactured by molding resin powder can be changed into the pot, and can be pressed by a plunger 13. A main runner 16 is extended toward the periphery of the block 11 from the pot 14. A formula Sa>Sb>Sc is set in the sectional areas Sa, Sb, Sc of the opening at points (a), (b), (c) of the runner 16. A plurality of cavities 15 are each formed into the cavity blocks 12, and communicated and connected with the main runner 16 through subrunners 17 formed.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a mold structure that is effective when resin molding a semiconductor device.

It is known that a semiconductor structure, in which a semiconductor element pellet is fixed on a base member such as a lead frame and the pellet and leads are connected, is molded with resin in order to protect it from external forces and air. Generally, the transformer 7-mold method is used. That is, the first
As shown in the figure, the molding die is composed of a center block 1 and cavity blocks 2 placed on both sides of the center block 1. A bot 4 having a plunger 3 is formed in the center block 1, and a bot 4 having a plunger 3 is formed in the center block 1. A cavity 5 shaped to be molded is formed in. A main runner 6 and a sub-runner 7 are extended between the bot 4 and the cavity 5 (they are communicated with each other), and a heated tablet 8 inserted into the bot 4 is pressed with a plunger to release the resin. is fed under pressure to the cavity 5 through the main runner 6 and sub-runner 7, and is molded into the same shape as the cavity.

By the way, the main runner 6 described above is conventionally formed to have the same inner diameter over the entire length from the pot 4 to the cavity block boundary. Therefore, when molding is performed with the tablet 8 at a low preheating temperature (high hardness or high viscosity after preheating), the initial flow resistance, especially when the resin flows from the bot 4 to the main runner 6, is increased. As a result, pressure loss increases, and the mold is not completed within a predetermined time, resulting in poor appearance and internal voids.

As a countermeasure against such accidents, it has been considered to increase the opening area of the main runner 6, but this reduces the heat transfer performance from the mold in the main runner section, making it difficult to reduce the viscosity of the resin. Pressure loss increases at the sub-runner 7 of the cavity block 2 and the gate portion of the cavity 5, resulting in poor appearance and internal voids as described above. In addition, there is also the problem that the opening area of the main runner 6 is increased (this increases the usage magnification of the resin and increases the waste of material).

Therefore, an object of the present invention is to prevent the viscosity of the tablet from decreasing by configuring the opening area of the main runner formed in the center block so that the area on the upstream side is larger than the area on the downstream side. An object of the present invention is to provide a mold structure for a resin mold that can prevent the pressure loss of the resin at the initial stage of inflow, thereby preventing appearance defects and internal voids, and at the same time achieving an improvement in the usage ratio of the resin. .

Hereinafter, the present invention will be explained with reference to illustrated embodiments.

FIG. 2 is an overall sectional view of the mold structure for a resin mold according to the present invention, and FIG. 3 is a schematic plan view of the main parts thereof. In the figure, a mold 10 has a center block 11 disposed in the center, and cavity blocks 12 and 12 disposed on both sides of the center block 11 so as to be in close contact with each other. A bot 14 is provided approximately at the center of the center block 11, into which a tufflet 18 made of molded resin powder can be inserted and pressed by a plunger 13. Further, a main runner 16 extends from the bot 14 toward the periphery of the center block 11, and in this embodiment, the bot 1
Extend two main runners from 4 and branch them into four main runners at the intersection P to form a cavity block 12.12
towards.

Here, in this example, the opening areas Sa, Sb, and Sc of the main runner 16 at point tbtC are 5a) Sb:
>SC. In other words, the opening area on the upstream side is set to be larger than the opening area on the downstream side. In this case, the cross-sectional shape of the main launch is not particularly limited, but generally has a substantially inverted trapezoidal shape as shown in FIG. Furthermore, the opening area of the main runner 16 may be reduced continuously from the upstream side to the downstream side, or may be reduced in stages.

On the other hand, a plurality of cavities (one in the figure) 15° 15 are formed in each of the cavity blocks 12 and 12,
It is communicatively connected to the main runner 16 via the established sub-runner 17.17.

In this case, subrunner 17. By making the opening area of L7 smaller on the downstream side than on the upstream side, it is possible to reduce the resin filling time difference during resin filling, which will be described later.

According to the above configuration, after heating the center block 11 and the cavity blocks 12 and 12 to a predetermined temperature, the tablet 18 is placed in the bot 14 and the tablet 18 is inserted into the plunger 13.
Press with. As a result, the resin flows from the main runner 16 to the sub runners 17 and 17 (each tablet) 18.
18 is filled. At this time, since the main launch 16 has a large opening area on the upstream side as described above, the pressure loss of the resin is reduced and the transfer delay is improved as shown in FIG. 5. In the figure, the horizontal axis is the preheating temperature, and the vertical axis is the transfer delay amount. Overall, as the preheating temperature decreases, the transfer delay amount also increases, but the main runner characteristic A of this example is still more transferable than the conventional characteristic B. It can be seen that the amount of delay is much smaller.

Therefore, as can be seen from the characteristics shown in Fig. 6, the smaller the transfer delay amount, the smaller the rate of void occurrence (degree). can be effectively suppressed.

On the other hand, since the opening area of the main runner 16 as a whole has not increased so much, the main block 11
It is possible to increase the efficiency of heat transfer from the resin to the resin, promote a decrease in resin viscosity, and increase the resin usage ratio.

As described above, according to the cash register/mold structure of the present invention, the opening area of the main runner formed in the center block is configured to be larger on the upstream side than on the downstream side. It is possible to prevent the generation of voids by reducing the accompanying pressure loss, and it is possible to reduce the viscosity of the resin, further increasing the prevention of void generation, and on the other hand, achieving an increase in the usage ratio of the resin. It has the effect of being able to

[Brief explanation of the drawing]

Fig. 1 is a schematic sectional view of a conventional general mold, Fig. 2 is a sectional view of the mold of the present invention, Fig. 3 is a partially cutaway plan view of the main part, and Fig. 4 is a main runner. 5 and 6 are graphs showing the characteristics. 10... gold m, it... center block, 12...
・Cavity block, 14...Pot, 15...
Cavity, 16, 16A... Main runner, 17.
...Sabranna, 18...Tablet. Figure 1 Figure 2 Figure 3 Figure 5 Figure 6 Figure/2.1'a 5 Continued from page 1 ■ Applicant Hitachi Microcomputer Engineering Co., Ltd. 1479-162, Josui Honmachi, Kodaira City

Claims (1)

[Claims] 1. A gold-plated structure in which a bot formed in a center block and a cavity formed in a cavity block are communicated through at least a main runner formed in the center block, and resin in the bot is transferred to the cavity, A mold structure for a resin mold, characterized in that the opening area of the main runner is larger on an upstream side than on a downstream side.