JPS63264315A - Molding die - Google Patents

Abstract

PURPOSE:To reduce occurrence of voids in a finished item by a method wherein fins, which make the air contained in molten resin fine bubbles, are provided at a cull part. CONSTITUTION:A preheated resin tablet 5, which is charged in a pot 6, is placed on a cull 7. After that, by lowering a plunger 13, the tablet 5 is turned into molten resin 14. Fins 15 are provided on the central bottom and inner wall parts of the cull 7. Since the molten resin 14 is flowed by being directed by the guide 16 at the center of the bottom of the cull 7 into sub-runners 9 and, sent through gaps 18 part at the upper part of agitating fins 17, the molten resin 14 is agitated so as to produce intricate flow therein by fine bubble parts 19 consisting of the fins 15 of the guide 16, the agitating fins 17 and the like, resulting in turning the air in the molten resin 14 into fine bubbles. Since the fine bubbles in the molten resin 14 are 14 are crushed by the large final pouring pressure applied with the plunger, no bubble develops is a hardened molding.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a mold, and particularly to a mold for a transfer mold in which resin melted in a cull portion is transferred to each cavity via a resin flow path.

(Prior art) A transfer mold press is generally used for sealing (pancage) in the manufacture of resin molded semiconductor devices.In this equipment, a lead frame with chips mounted and wire tensioned is placed in a mold. After being sandwiched between the upper and lower molds (mold clamping), the resin tablet placed in the bot in the center of the upper mold and placed on the cull in the center of the lower mold is heated under pressure with a plunger. to melt it,
Melted resin is fed into the cavity through the resin flow path (main runner, sub-runner, gate) formed by the upper and lower molds, and the lead frame portion located inside the cavity is covered with resin. Further, since the resin in the cavity and the resin flow path is cured and hardened, the cured molded product is taken out after the upper mold and lower mold are separated (mold opening).

By the way, the transfer mold press is described, for example, in "Electronic Materials J, 1983 Special Issue," published by Kogyo Research Association.
Published November 15, 1980, described in P2S5-P2S5. This document describes voids that directly affect the molding yield and subsequent quality due to the shape of the runner and gate in the mold.

Since it is related to blisters, microcranks, etc., it is stated that its use must be carefully determined in consideration of the epoxy resin used, the shape of the lead frame, and molding conditions. In addition, in the same document, in order to improve moisture resistance,
It is also stated that it is essential to eliminate internal voids and microcracks.

[Problem that the invention seeks to solve]

In conventional transfer molds, when the air that exists in the gap between the pot and the tablet, or the air that originally exists inside the tablet, is compressed by the plunger, it gets caught up with the resin and creates large bubbles that reach the cavity. The inventors have clarified that the material is transported in a state in which it remains in the cavity without being crushed even when the final injection pressure is applied, and this causes voids. That is, the present inventor observed a state in which no final injection pressure was applied during transfer molding, in other words, a state in which the resin was injected into the cavity and before the resin had hardened. In the resin injection state before this final injection pressure is applied, although the inside of the cavity is filled with resin, it is porous and contains a large amount of fine air. Therefore, in order to reduce the voids inside the cavity, the inventor of the present invention decided to set the size of the air masses (bubbles) in the resin fed into the cavity to a size that can be crushed by the final injection pressure. The inventors realized that it was possible to reduce the incidence of voids in finished products and developed the present invention.

An object of the present invention is to provide a mold that can reduce the occurrence of voids.

The above and other objects and novel features of the present invention include:
It will become clear from the description of this specification and the accompanying drawings.

[Means for solving problems]

A brief overview of typical inventions disclosed in this application is as follows.

In other words, the mold of the present invention is a resin tablet! ! The cull part where the resin is placed is equipped with fins that work to make the air contained in the melted resin into fine bubbles.

[Effect]

According to the above means, in the mold of the present invention, the fins are provided in the cull portion.

For this reason, when the resin is put into the pot, which is the entrance of the resin transport path, and is cut onto the cull, when it is pushed out by the plunger, it is stirred by the fins of the cull, and as a result, the flow changes from laminar to turbulent. Due to this change, the air bubbles in the resin become finer and smaller. As a result, the minute air bubbles that have reached the inside of the cavity are crushed by the final injection pressure from the plunger, and the generation of air bubbles (voids) within the cured resin package is suppressed.

Therefore, a molded product with excellent moisture resistance can be manufactured.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a plan view showing a cull in a mold according to an embodiment of the present invention, FIG. 2 is a cross-sectional view taken along the line ■-■ in FIG. 1, and FIG. 3 is a plan view showing how resin flows in the cull. FIG. 4 is a schematic plan view showing the same, and FIG. 4 is a sectional view showing the main parts of the mold.

This embodiment is characterized by the cull portion of the lower die of the mold. Before explaining this cull portion, the entire mold will be briefly explained with reference to FIG.

As shown in FIG.
and an upper mold 3 (!:).The object to be molded, that is, the assembled lead frame 4, is held between the upper and lower molds 3.2.A resin tablet is placed in the center of the upper mold 3. A cylindrical bot 6 into which the bot 5 is introduced is provided.A cylindrical bot 6 is provided on which the bot 6 is placed.
There is a depression called. The preheated resin tablet 5 put into the Bontro is
be placed on top. Further, a resin flow path called a runner 8 extends from the cull 7 . This runner 8 is sub-runner 9. A resin flow path, referred to as a gate 10 , continues into each cavity 11 . The cavity 11 is also provided in the upper mold 3, and the cavities 11 in the upper and lower molds 3°2 form a mold space.

Moreover, at the end of the subrunner 9 and the cavity 11,
An air vent 12 consisting of an extremely narrow space is provided. These air vents 2 serve as passages through which air escapes during molding.

During molding, a lead frame 4 is placed between the upper and lower molds 3 and 2.
is sandwiched, and then preheated resin tablet 5
is put into pot 6. Then, as a result of the plunger 13 descending inside the bot 6, the resin tablet 5 that has started melting is combined with the compression by the plunger +13 to become a molten resin 4, which flows from the cull 7 into the runner 8, and then into the sub-runner 9. ．． Cavity 1 through gate 10
sent into 1. The molten resin 14 is cured and hardened after a certain period of time. Then, the lower mold 2 and the upper mold 3 are opened, the molded product is taken out, and the -th molding operation is completed.

By the way, the conventional Cal 7, as shown in Fig. 3,
Because it has a simple circular hollow structure, the plunger 13
The molten resin 14 that flows out under pressure flows out relatively smoothly as shown by the arrow and advances into the runner 8, so the air that existed between the resin tablet 5 and the bot 6 is removed from the cull 7 and the runner. There is a high probability that the air will flow along the inner wall surface of the tube 8, etc., and will proceed into the cavity 11 as a large air mass, which will cause voids to occur during molding.

Therefore, in the cull 7 of this embodiment, as shown in FIGS. 1 and 2, fins 15 are provided at the center bottom and inner wall portions of the cull 7, respectively. In these fins 15, the fin 15 provided at the center of the bottom of the cull 7 has a boat-shaped streamline structure, and the resin 14 is attached to the runner 8.
It is a guide lG that flows to the side. Further, the fins 15 provided on the inner periphery of the cull 7 are elongated protruding stirring fins I7, and the molten resin 14 flows toward the center of the cull 7. Moreover, the space between each cull 7 constitutes a semicircular curved surface. Therefore, as shown in Figure 3,
The flow of the molten resin 14 is blocked by each stirring fin 17,
Since the flow direction is regulated by the curved surface between the stirring fins 17, the molten resin 14 swirls as shown by the arrow, and as shown in FIG. Since it is formed to be lower than the parting surface by e, a gap 18 is generated between it and the bottom surface of the plunger 13.

In the cull 7 having such a structure, the molten resin 14 crushed and pressurized by the plunger 13 is directed to the guide 16 at the center of the bottom of the cull 7, and is directed to the sub-runner 9.
In addition to flowing into the launcher 8 , the molten resin 14 also passes through the gap 18 at the top of the stirring fin 17 and is fed into the launch 8 .
The air in the molten resin 14 is stirred to form a complicated flow in the air bubble section 19 formed by the fins 15, and the air existing in the molten resin 14 becomes minute bubbles.

As a result, the cavity 11 is filled with the molten resin 14 containing only minute bubbles. Also, the plunger 13 causes the molten resin 14 inside the cavity 11 to be removed.
Inside, a large final injection pressure (typically 70 kg/cm
"~80kHz/cm") is added. For this reason,
The minute air bubbles in the cavity 11 and the like are crushed by the pressure, and their volume becomes several tenths of that, disappearing macroscopically, and no air bubbles (voids) are generated in the hardened mold.

Note that after the molten resin 14 has hardened within the mold 1,
The mold 1 is opened and the molded product is taken out.

According to such an embodiment, the following effects can be obtained.

(1) When the mold of the present invention injects molten resin into the cavity, the air in the molten resin is reduced to bubbles with a size smaller than the size that disappears at the final injection pressure, so that voids are eliminated. The effect is that the occurrence can be suppressed.

(2) According to the above (1), the mold of the present invention has the effect that the mold yield can be improved by reducing the generation of voids.

(3) The above (1) and (2) provide a synergistic effect in that a molded product with excellent moisture resistance can be provided at a low cost.

Although the invention made by the present inventor has been specifically explained above based on Examples, it goes without saying that the present invention is not limited to the above Examples and can be modified in various ways without departing from the gist thereof. For example, the structure of the air bubble portion may be a structure other than a fin. Further, even if the air bubble portion is provided in a resin flow path other than the cull, the same effect as in the above embodiment can be obtained.

In the above description, the invention made by the present inventor was mainly applied to the resin molding technology in semiconductor device manufacturing, which is the background field of the invention, but the invention is not limited thereto.

The present invention can be applied to a technique in which at least part or all of an article is molded with resin.

〔Effect of the invention〕

A simple explanation of the effects obtained by typical inventions disclosed in this application is as follows.

Since the mold of the present invention aims to make the air contained in the resin into fine bubbles in the air bubble portion, it is possible to reduce the size of the air bubbles in the resin filled in the pan cage. Also, this bubble disappears due to the final injection pressure. Therefore, according to the present invention, the generation of voids in a molded product can be suppressed, and a mold with excellent moisture resistance can be achieved, so that a molded product with excellent quality can be provided at a low cost.

[Brief explanation of the drawing]

FIG. 1 is a plan view showing a cull in a mold according to an embodiment of the present invention, FIG. 2 is a sectional view taken along line nn in FIG. 1, and FIG. FIG. 4 is a sectional view showing the main parts of the mold, and FIG. 5 is a schematic plan view showing how resin flows in a conventional cull. l...mold mold, 2...lower mold, 3...upper mold, 4
...Lead frame, 5...Resin tablet, 6
...bot, 7...cal, 8...runner, 9...
・Subrunner, IO...gate, 11...cavity, 12...air vent, 13...plunger,
14... Molten resin, 15... Fin, 16...
Guide, 17... Stirring fin, 18... Gap, 19
・Figure 3 Figure 4 Figure 5

Claims (1)

[Scope of Claims] 1. A mold having a resin flow path for guiding melted resin and a cavity communicating with the resin flow path, wherein the resin flow is stirred in a part of the resin flow path. A mold type characterized by being provided with air cells that turn the air contained in the resin into fine bubbles. 2. The mold according to claim 1, wherein the air cell portion is provided in a cull portion into which a resin tablet is placed.