JPS63193814A - Mold for transfer molding - Google Patents

Abstract

PURPOSE:To obtain molded resin having neither an inner void nor a blister by making uniform a state of pressed resin in each of cavities, by providing a valve on an air vent of the cavity. CONSTITUTION:Resin is pressed into cavities from the cavity 10a close to the pressing-in section in order to the terminal cavity 10b passing through a runner 6a from a cull 12 of a resin reservoir However, as an air vent 3a is closed by a valve 1 up to three sets from the runner 6b of the pressing-in suction, the casting resistance is increased, a pressed-in quantity of the resin is controlled and the resin is pressed into the cavities 10b of terminal two sets at high pressure. Therefore, the state of pressing the resin 11a in the cavity 10a and the resin 11b in the cavity 10b become close to about uniformity to each other. Then when air of the cavity 10a is released outside through the air vent 3a by opening the valve 1, every cavity in also filled with the resin, and generation of an inner void or a blister is eliminated.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a transfer mold die.

[Conventional technology]

With the recent mass production of resin molds, the number of cavities in transfer molds has increased in order to perform multi-cavity molding.

FIG. 3 is a longitudinal sectional view of an example of a conventional transfer mold die.

A semiconductor chip 7 mounted on one of the lead frames 8 is inserted into a cavity 10 formed by combining the upper mold 4 and the lower mold 5.

A runner 6 and a gate 9 for injecting press-fit resin into the cavity 10, and an air vent 3 as an escape route for air from the cavity 10.
b is also formed at the same time.

[Problem that the invention seeks to solve]

In the conventional transfer mold mold described above, the air vents 3b of each cavity 10 have the same dimensions and are open to the outside, and the cavities closer to the resin compression source have a higher initial pressure than the cavities at the end. Since a significantly large amount of resin is injected into the cavity, there is a problem in that resin engineering conditions become non-uniform depending on the position of the cavity.

In particular, cavities close to the resin compression source are in a state where no holding pressure is applied even after the resin is filled until the end cavity is filled with resin, resulting in voids and blisters inside the molded resin. There was a problem.

An object of the present invention is to provide a transfer molding die that can uniformly adjust the initial injection amount of press-fitting resin and that can produce molded resin of good quality.

[Means for solving problems]

The transfer mold mold of the present invention includes (A) a pair of upper and lower molds in which a plurality of resin passages are formed for receiving injected resin in a runner and passing through a cavity and exiting to an air vent; (B) a mold provided in at least two of the air vents; and a valve that adjusts the flow rate of air passing through the air vent.

〔Example〕

Next, the present invention will be explained with reference to the drawings.

FIG. 1 is a longitudinal sectional view of one embodiment of the present invention.

The mold is the same as the mold shown in FIG. 3 except that the valve 1 and its valve driving device 2 are provided in the upper mold 4 and the lower mold 5 so as to be perpendicular to the air vent 3a.

Next, the operation of this embodiment will be explained.

As shown in FIG. 1, when the pair of upper and lower valves 1 are closed with the lead frame 8 in between, even if the resin is press-fitted from the runner 6a, the air in the cavity 10a will flow to the air vent 3.
Since the resin cannot escape to the outside through the air vent 3a, the amount of resin press-fitted from the runner 6a into the cavity 10a can be controlled by moving the valve 1 up and down using the valve drive device 2 to adjust the amount of air passing through the air vent 3a.

FIGS. 2(a) to 2(b) are cross sections of a mold shown in order of resin press-fitting steps to explain this embodiment.

As shown in FIG. 2(a), the valve 1 closes the air vent 3a during the initial step of resin press-fitting.

The press-fit resin passes from the cull 12 of the resin reservoir through the runner 6a,
Resin is press-fitted into the cavities 10b at the end in order from the cavity 10a closest to the resin press-in area, but since the air vents 3a are closed by the valve 1 from the runners 6a to 3, the injection resistance increases. The amount of resin press-in is limited to 1/2 to 115 compared to the conventional one, but since the two sets at the end are the same mold as in Figure 3, the cavity 10 is injected with a higher pressure than the conventional one.
Resin is press-fitted into b.

Therefore, the press-fit cores of the resin 11a in the cavity 10a and the resin 11b in the end cavity 10b become almost uniform.9 Next, as shown in FIG.
Approximately 10 seconds after the resin is press-fitted into Oa, valve 1 is opened to release the air in the press-in cavity 10a to the outside through the air vent 3a, lowering the injection resistance in cavity 1'Oa, and rapidly press-fitting the resin. Since the cavity is also filled with resin and a holding pressure of about 10 seconds is applied, internal voids and bulges in the molded resin are eliminated.

Although a plurality of valves 1 in this embodiment were operated to open and close at the same time, the flow rate of air was precisely adjusted by operating the valve drive device 2 for each cavity to individually set the opening/closing degree and time of the valve 1. You can also.

〔Effect of the invention〕

As explained above, the present invention has the effect that by providing a valve in the air vent of each cavity, the condition of the press-fitted resin in each cavity can be made uniform, and molded resin without internal voids or blisters can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal sectional view of an embodiment of the present invention, and FIG. 2(a)-
(b) is a cross-sectional view of a mold shown in the order of resin press-fitting steps for explaining this embodiment, and FIG. 3 is a vertical cross-sectional view of an example of a conventional transfer mold mold. DESCRIPTION OF SYMBOLS 1... Valve, 2... Valve drive device, 3a, 3b... Air vent, 4... Upper mold, 5... Lower mold, 6a, 6
b...Runner, 7...Semiconductor chip, 8...Lead frame, 9...Gate, 10a, 10b...Cavity, 11a, llb...Resin, 12...Cal.

Claims (1)

[Scope of Claims] (A) A pair of upper and lower molds in which a plurality of resin passages are formed for receiving injected resin in a runner and passing through a cavity and exiting to an air vent; (B) a mold provided in at least two of the air vents, A transfer mold mold comprising: a valve that adjusts the flow rate of air passing through an air vent.