JPS62135330A - Transfer molding method - Google Patents

Abstract

PURPOSE:To enable molding such that no recess is generated on the surface of a molded product, by a method wherein a hole is provided to a mold so as to be continued to the cavity part thereof and a porous metal body is inserted in a said hole to supply gas to the cavity part from the outside through the metal body at the time of demolding and the molded product is allowed to be spaced apart from the mold by the pressure of the gas. CONSTITUTION:A product 7 is preset in a cavity part 3 and a preheated tablet 9 is thrown in a pot 10 and a plunger 11 is subsequently fallen. Whereupon, a heated molten resin is injected in the cavity part 3 through a runner 12 and a gate 13. After the resin was cured under heating, an upper mold 1 and a lower mold 2 are opened to take out a molded product. Holes 14 continued to the cavity part 3 are provided to the molds 1, 2 and porous metal bodies 15 are inserted in said holes 14 and constituted of a sintered metal comprising bronze or stainless steel. After the injected resin is cured, gas is supplied into the holes 14 along the directions shown by arrows. The pressure of the gas at this time acts so s to allow the molded product to be spaced apart from the molds 1, 2.

Description

[Detailed description of the invention] (Industrial application field) The present invention relates to a transfer molding method.

(Prior Art) As is well known, this type of molding method is widely used when semiconductor elements are encapsulated with resin, and usually involves heating a product in which a semiconductor element is assembled on a lead frame and molding it into a mold. It is set in a cavity, heated and molten resin is injected into it, the resin is cured, and then the upper and lower molds are opened to take out the molded product.

By the way, in conventional molding methods that use molds, when the upper and lower molds are opened to take out the molded product, ejector pins are used to improve the mold release properties of the molded product from each mold. is considered normal.

4 and 5 show a conventional molding method, in which 1 is an upper mold, 2 is a lower mold, 3 is a cavity formed by both molds 1 and 2, and 4 is an ejector pin.

A product 7 in which a semiconductor element 6 is assembled on a lead frame 5 is set in the cavity 3, heated and melted resin is injected into it, and then the upper mold 1 and the lower mold 2 are opened (Fig. 5). ) Remove the molded product 8. At this time, the molded product 8 is ejected by the ejector pin 4 and separated from the molds 1 and 2.

By the way, according to such a forming method, the ejector pin 4
is in contact with the surface of the molded product 8 only in a point-like manner,
The force for releasing the mold is not very large, and in addition, dents are formed on the surface that comes in contact with the ejector pins 4, which impairs the appearance of the molded product and may limit markings, etc. .

Not only that, but the ejector pin 4 may be □ due to the resin pad etc.
It may become stuck to the mold and cannot slide, and as a result, it may not be able to perform its mold release action.

(Problems to be Solved by the Invention) An object of the present invention is to ensure the mold release of a molded product and also to enable molding without causing any dents on the surface of the molded product.

(Means for Solving the Problems) This invention provides each mold with a continuous hole in its cavity, inserts a porous metal body into the hole, and uses this metal body as a part of the mold. In addition, when the molded product is released from the mold, gas is supplied from the outside through this metal body, and the molded product is separated from the cavity portion by the gas pressure.

(Example) An embodiment of the invention will be explained with reference to FIG.

Note that parts given the same reference numerals as in FIGS. 4 and 5 indicate the same or corresponding parts. The product 7 described above is set in the cavity 3, and when the preheated tablet 9 is put into the pot 10 and the plunger 11 is lowered, the resin heated and melted in the pot 10 flows into the runner 12,
It is injected into the cavity 3 through the gate 13. After the injected resin is heated and hardened, the upper mold 1. Open the lower mold 2 and take out the molded product 8.

These molding methods are not particularly different from conventional methods, but according to the present invention, each mold 1, 2 is provided with a hole 14 that is continuous with the cavity 3, and a porous metal body 15 is inserted into this hole 14. , which forms a part of the cavity 3 of the mold. In the figure, this metal body 15 is used as the earthen wall and lower wall of the cavity portion 3.

The metal body 15 is made of sintered metal such as freon, stainless steel, or the like. Further, the porosity should be smaller than the resin component used, and should be of a size that allows gas flow.

In the above configuration, when the upper mold 1 and the lower mold 2 are opened to take out the molded product 8 after the resin injected into the cavity 3 has hardened, a gas such as nitrogen gas is injected into the hole 14 along the direction of the arrow. supply The gas pressure at this time passes through the inside of the metal body 15 and pressurizes the surface of the molded product 8. This pressing force acts to separate the molded product 8 from each mold 1, 2.

During separation at this time, the metal body 15 is in planar contact with the surface of the molded product 8, so the separation force due to gas pressure acts as a surface, and therefore the mold release performance is lower than that of the conventional ejector pin. The mold release is much improved compared to the point-based mold release method. Furthermore, since no ejector pins are used, no protruding parts are created on the surface of the molded product. Moreover, there is no difficulty in releasing from the mold due to the inability of the ejector pin to slide due to Paris or the like.

(Effects of the Invention) As detailed above, according to the present invention, molded products can be released more easily and reliably than conventional methods, and markings can be restricted due to the presence of recesses on the surface of molded products. It has the effect of not being there.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view for explaining the method of the embodiment of the present invention, FIGS. 2 and 3 are cross-sectional views for explaining each step of the method of the embodiment, and FIGS. 4 and 5 are conventional FIG. 3 is a cross-sectional view for explaining each step of the method. 1... Upper mold, 2... Lower mold, 3... Cavity part,
8... Molded product, 14... Hole, 15... Metal body.

Claims (1)

[Claims] A continuous hole is provided in the cavity of the mold, a porous metal body is inserted into this hole, and this metal body is used as a part of the mold, and the resin injected into the cavity is A transfer molding method, characterized in that when releasing the molded product, gas is supplied from the outside through the metal body, and the gas pressure causes the molded product to be separated from the cavity portion.