Method of transfer molding and a transfer molding machine

Details Method of transfer molding and a transfer molding machine Method of transfer molding and a transfer molding machine

1993-12-08

1998-06-23

Ortiz, Angela Y.

Plastic and nonmetallic article shaping or treating: processes

With step of cleaning, polishing, or preconditioning...

26427217, 425210, 425229, 425544, B29C 4502, B29C 4514

Patent

active

057701288

DESCRIPTION:

BRIEF SUMMARY
BACKGROUND OF THE INVENTION

The present invention relates to a method of transfer molding and a transfer molding machine for molding insert-parts, e.g., lead frames of semiconductor devices, with resin.
In case of molding lead frames by a transfer molding machine, the steps are: setting lead frames in a lower die; clamping the lead frames by the lower die and an upper die; filling cavities with resin; opening the lower die and the upper die; and taking out molded products. A press unit is provided for opening and closing a mold, which consists of the lower die and the upper die arranged in the vertical direction, and presses are provided to move the mold for each molding work.
Therefore, setting lead frames in the lower die and taking out molded products are executed by a loader or loaders, which are capable of going into the press unit from the side thereof so as to transfer lead frames.
Operating efficiency of the transfer molding machine is basically defined as molding cycle time, so it is quite important for increasing the efficiency to shorten the molding cycle time. Thus, a transfer molding machine with high speed operation has been required.
Actions of a conventional transfer molding machine, which has two loaders: an unloader and a parts-loader, with respect to time is shown in FIG. 19. The horizontal axis stands for time; the vertical axis stands for actions. Graph a stands for opening and closing the mold (the lower die and the upper die): the mold is opened after molding, and the mold is closed again after predetermined time passes. Graph b stands for taking out molded product from the mold. Graph c stands for the movement of the unloader: after the mold is opened, the unloader goes into the press unit, chucks molded products and comes out therefrom. Graph d stands for the movement of the parts-loader: the parts-loader sets next lead frames into the lower die after the unloader took out the molded products. After the parts-loader sets the lead frames, the mold is closed. In the conventional high speed type transfer molding machine, the cycle time will be 15 seconds.
To shorten the cycle time of the transfer molding machine, accelerating speed of opening and closing the mold and travelling the unloader and the parts-loader has been proposed, but the speed of opening and closing the mold is limited, in other words, shortening the cycle time of the conventional transfer molding machine is limited.
As shown in FIG. 19, in the actions of the conventional transfer molding machine, for example, the unloader starts to move after the lower die and the upper die completely opened, the parts-loader moves after the movement of the unloader, namely the actions are sequentially executed. The reason why the actions must be sequentially executed is that the unloader and the parts-loader must be operated while the mold is opened, so that the cycle time of the conventional transfer molding machine cannot be efficiently shortened.
Furthermore, in the conventional transfer molding machine, parting faces of the lower die and the upper die are cleaned by the unloader, so the cleaning must be executed after the lower die are and the upper die completely opened, if the positions of the parting faces are not fixed when they are cleaned, effective cleaning cannot be executed.


SUMMARY OF THE INVENTION

An object of the present invention is to provide a method of transfer molding and a transfer molding machine, which are capable of shortening the cycle time and increasing production efficiency by effective operation of opening and closing the mold, movement of the loaders without accelerating the speed thereof.
To achieve the object, the present invention has following constitutions.
Firstly, a method for transfer molding, being capable of moving in said pots,
said method comprising the steps of:
setting insert-parts into said mold;
supplying resin tablets into said pots;
clamping said insert-parts by said upper die and said lower die; and
exerting pressure on resin melt by said plungers, so as to fill cavities in said

REFERENCES:
patent: 4347211 (1982-08-01), Bandoh
patent: 4372740 (1983-02-01), Kuramochi et al.
patent: 4388265 (1983-06-01), Bandoh
patent: 5302101 (1994-04-01), Nishimura

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