JPS5947097A - Forming of powder resin tablet - Google Patents

Abstract

PURPOSE:To enable preform at a uniform density in forming a circular cylindrical tablet of a powder resin, by exerting pressure on the side face of the circular cylinder. CONSTITUTION:A hole having a rectangular section is opened in a die 2, and a powder resin 3 is put there and is compressed in a vertical direction (arrows B, B') by means of a pair of punches 1a, 1b of which the half of the side faces of the circular cylinder is sunk. Then the tablet of a large weight can be removed as far as the dies have the stroke equal to the diameter of the circular cylinder and therefore one-piece molding is made possible and the density distribution in the axial direction is made uniform. If resin molding is accomplished with this tablet, the generation of the voids in the resin molding occurring in the air existing in the part where the density is nonuniform and small is reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a powder resin tablet molding method for resin molds (
Regarding preforms, the main target is powder resin for resin mold sealing of semiconductor devices.

Semiconductor devices such as transistors and ICs are made by connecting the semiconductor element (pellet) that forms the main body to leads, and then molding a resin (transfer mold) to partially surround the element and leads. However, cylindrical powder resin cubes 7) are usually used as the resin raw material for this resin mold. When making this powder resin tapelet into a cylindrical shape, the powder resin is put into the die of the preform mold, and conventionally it is compressed in the axial direction from both end faces of the cylinder using a punch. By doing so, it was molded.

The reason why a preform is necessary is to mold with as much pressure as possible to increase density in order to prevent air intervening between particles of powdered resin during resin molding from causing voids in the product. be. However, as the weight of the powdered resin increases and the length of the cylinder becomes the same, the density at the center decreases compared to both ends, making it impossible to obtain a uniform density and requiring a longer stroke to remove the tablet from the die.
The resin molded product collapsed during removal.

The object of the present invention is to improve the brifmeme method, which overcomes the above-mentioned drawbacks, and to make it possible to perform brifmeme with uniform density.

The powder resin tablet molding method according to the present invention is similar to the conventional method.
) is not compressed from the end face of the cylinder, but pressure is applied from a direction perpendicular to the side wall of the cylinder. That is, conventionally, as shown in Fig. 1, the die 2 has a round hole, the powdered resin 3 is put into the hole, and a cylinder having the same diameter as the hole is formed from both ends of the hole along the directions of arrows A and A'. In contrast, in the present invention, as shown in FIGS. 2 and 3, a hole with a rectangular cross section is made in the die 2, and the powder resin 3 is compressed by pushing the punch 1 into the hole.
and two punches I that drilled half of the sides of the cylinder.
The configuration is such that compression is performed in the vertical direction (arrows B and B') by a and Ib.

According to the present invention described in the embodiments above, the following effects can be obtained.

(1) In a powder resin preform, even a heavy tablet can be removed from the die if the stroke is the diameter of the cylinder, so single-piece molding is possible and the density distribution in the axial direction is uniform.

(21 Since the stroke is short, there is less wear on punches and dies, extending their life.

(By carrying out resin molding using a powdered resin tablet that has been sealed by the 31J double preform method, the occurrence of voids in the resin molded product due to uniform density of 3T in any part of the tablet can be reduced.

(4) The reliability of semiconductor products sealed with resin molded products with less void generation can be improved.

This cicada; Akira is mJ tl by transfer molding method.
Applicable to resin side stops for all semiconductor products.

[Brief explanation of the drawing]

FIG. 1 is a vertical sectional view of a main part of a molding apparatus showing one form of the conventional Kubresoto molding method. FIG. 2 is a cross-sectional view of a main part of a molding apparatus showing an embodiment of the tablet molding method according to the present invention. FIG. 3 is also a longitudinal sectional view. 1...Punch, 2...Die, 3...Powder resin, arrow A. A', 13. I'...Pressure direction. 1st 2nd Figure 3

Claims (1)

[Scope of Claims] 1. A powder resin tablet molding method characterized by applying pressure to the side surface of the cylinder in molding a cylindrical powder resin tablet for a resin mold. 2. The powder resin tablet molding method according to claim 1, wherein the resin mold is a resin mold for stabbing a semiconductor element.