JPS6315892B2 - - Google Patents

Description

BACKGROUND OF THE INVENTION The present invention relates generally to transfer molding of multi-plastic molded articles, and more particularly to transfer molding of multi-plastic encapsulated semiconductor devices.

Description of the Prior Art In the transfer molding of multi-plastic articles with multi-cavity metal molds, embodiments of the prior art provide multi-cavity metal molds comprising separable upper and lower mold sections; The upper and lower mold sections had a plurality of cavities for the molded parts and a plurality of runners with a distribution device for supplying molding material to each individual cavity. The runners typically terminate in a common cull or gate area that is used to supply plastic molding material to multiple cavities. The upper and lower mold halves are held together in a press and the assembly is heated to cure the molding material. Since the plastic molding compound, which is usually a powder, has been pressed or pelletized, the molding compound is pretreated in part of the mold assembly to bring it into liquid or semi-liquid form. A plunger is used to force the heated molding material under very little pressure into a runner system of the mold for distribution into each of the plurality of part cavities of the multi-cavity mold.

Some of the disadvantages of transfer molding equipment of the type described above include that the molding material must be pelletized to a size commensurate with the volume of the mold cavity and runners to be used. As a result, rather large plugs of plastic molding compounds often require considerable preheating time. Since the runner is in the mold half along with the part cavity, the heated mold half also causes the plastic molding material to harden in the runner and part cavity. This can result in considerable plastic waste, depending on the relative volumes of the runner and molding cavity. Also, since this equipment cannot provide a continuous supply of molding material, output is limited by the batch nature of the operation. Therefore, regarding transfer molding of small multi-molded products using heated multi-cavity molds,
There was a need to provide a method and mold part that allows continuous supply of molding material, preferably in powder form.

According to one embodiment of the invention, it is an object of the invention to provide an apparatus for transfer molding of small moldings.

Another object of the present invention is to provide an improved mold apparatus for insert molding of semiconductor electronic devices and integrated circuits.

Yet another object of the present invention is to provide a mold apparatus that is capable of substantially continuously feeding plastic molding material into a multi-cavity mold.

Yet another object of the present invention is to provide a mold apparatus that avoids the need to pelletize plastic molding materials.

According to a preferred embodiment of the invention, the runner section of the multi-cavity mold is configured to provide a flow of molding material directly to the gate section of the mold without curing the plastic within the runner section of the mold. , is insulated from the metal mold cavity.

According to another embodiment of the invention, the runner section of the molding device is cooled to prevent the plastic molding compound from hardening within the runner device.

According to yet another embodiment of the invention, the plastic molding material is distributed through a runner that is sufficiently cool to prevent the molding material from curing until it reaches the cull or gate portion of the molding apparatus, where the pressure A plunger and local heating device are provided below to supply liquid molding material to the mold cavity.

These and other objects, features and advantages of the invention will become apparent from the following detailed description of preferred embodiments of the invention, as particularly illustrated in the accompanying drawings.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring now to FIG. 2) is illustrated. The mold is separated along the parting line between the upper mold part 4 and the lower mold part 2 to enable extraction of the finished molded plastic article. Both mold halves are made of a thermally conductive metallic material, for example stainless steel. Above the upper mold part 4 are additional metal members or blocks 10, 12 forming part of a runner 20 for feeding plastic molding material into the lead frame cavity of the mold. The vertical portion of runner 20 is formed by a block 15 with a tapered orifice.
The runner blocks 10, 12 have a number of runners 20 feeding the cavities of the cavity block. Each of the plurality of runners 20 is supplied from a central reservoir of plastic molding compound.

Each runner 20 is insulated from the upper mold part 4 and the lower mold part 2 by a heat insulating member 14, which keeps the temperature of the runner at most about 80°C while the upper and lower mold parts are heated to about 170°C. Maintain at °C. insert heating element 18 provides a high temperature tip to maintain the temperature of the cull or gate area at approximately 185°C;
Facilitates heating of the plastic molding compound in the flow section just before the entrance to the part cavity supporting the insert lead frame. Coolant is passed through the passage 16 and the orifice block 15 is connected to the runner 2.
The temperature is maintained low enough to prevent liquefaction and/or hardening of the molding material within 0.00 mL. A parting line between the block portions 10, 12 of the runner allows the blocks to be separated in order to wipe clean the runner if necessary. Runner or passageway 2
Applying pressure or vacuum to the ends of the horizontal sections (not shown) of the plastic molding material can be applied to the cavity of the mold at the beginning of the molding cycle, or after the cavity has been filled with liquefied material. It is better to collect the amount.

Referring now to FIG. 2, a section of a mold apparatus similar to that shown by FIG. 1 is shown in cross-section. The upper mold half 4 and the lower mold half 2 have metal inserts 8
It has a number of cavities for forming the main body 6 around the periphery of the main body 6. The block portions 10, 12 of the runners of the mold apparatus are the runners 2 for supplying a flow of plastic molding material to the cavity of the mold.
It has 0. The mold apparatus of FIG. 2 differs from the mold apparatus of FIG. Different from type equipment. In this way, the runner block can be maintained at about 80 DEG C. while the cavity block is maintained at about 170 DEG C. for a considerably longer period of time than the apparatus of FIG. Thus, by removing only the lower part 2 of the cavity block with the molded article after the completion of each transfer molding cycle, an almost automatic or continuous molding process can be carried out. The runner block remains cold,
In its lower position, plunger 16A blocks the flow of plastic material through the orifice. After replacing the lower part 2 of the cavity block, the plunger 16A is raised and then lowered again to force a predetermined amount of plastic material into the cavity block, where it is heated to a high temperature maintained at approximately 185°C. The plastic material is heated and liquefied by the chip element 18. A plunger 16A with a plastic ring/tip portion 17 seats in the orifice to maintain high pressure during the curing portion of the cycle.

In the apparatus shown in either FIG. 1 or FIG. 2, the insulation and/or cooling means keep the temperature of the runner block sufficiently low that no hardening occurs within the runner block. Also, the temperature of the runner block can be kept low enough so that the plastic material is not substantially melted, and in this case the feedstock is preferably a non-pelletized plastic molding material.

While the invention has been particularly shown and described with respect to preferred embodiments thereof, it will be apparent to those skilled in the art that other changes may be made in form and detail without departing from the scope and spirit of the invention as claimed. You will understand what you can do.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a cavity for molded parts and a cold runner device of a fixed mold device according to the invention, and FIG. 2 is a sectional view of a molded part cavity and a cold runner device for use in a device in which mold parts are moved in and out of a mold station in a semi-continuous manner. FIG. 2 is a cross-sectional view of a cold runner mold apparatus having a plunger for use in the cold runner mold apparatus. 2... lower half of the mold, 4... upper half of the mold, 10,
12, 15...Block, 14...Insulating member, 2
0...Runner.

Claims (1)

[Scope of Claims] 1. A mold apparatus for transfer molding of a plurality of small molded products, comprising a cavity block having a plurality of molded product cavities in which the small molded products are cured, and a runner means. , a runner block for supplying a plastic molding material to the cavity, and a runner block between the runner block and the cavity block, the runner block being configured such that the plastic molding material does not harden in the runner block. and cooling means proximate said runner block for preventing hardening of said plastic material in said runner block, said cooling means means and a plurality of passages for passing a coolant, each in contact with a portion of the runner block, and within the cavity block for heating the plastic molding material prior to entering the cavity. further comprising localized heating means, said heating means comprising a solid plug member positioned adjacent to a common passageway in said gate means abutting said cavity, said cavity block being connected to said upper portion; a lower portion, the runner block further having an inclined inner bore, and the cooling means is located in the upper portion of the cavity block and adjacent the inclined bore of the runner block. A mold apparatus surrounding the block, wherein the heating means is located directly below the inclined bore of the runner block. 2. A mold apparatus for transfer molding of a plurality of small molded products, comprising a cavity block, a plurality of cavities of the cavity block, a gate means for introducing plastic molding material into each of the cavities, and a runner. a block, runner means of said runner block for flowing plastic molding material, and a plunger tip for forcing said plastic molding material into said plurality of cavities and maintaining said plastic material under high pressure within said cavities. plunger means for contacting said runner block;
cooling means for preventing hardening of the plastic molding compound in the runner block, the cooling means including a plurality of coolant passages in the surface of the runner block, the passages being cooled by the insulation means. and further comprising localized heating means within said cavity block for heating said plastic molding material before said plastic molding material enters said plurality of cavities. said heating means is located adjacent to a common passageway in said gate means abutting a molded article cavity, said small molded article being cured within said molded article cavity and said heating means The cavity block further has an upper portion and a lower portion, and the runner block further has an inclined inner bore, and the cooling means is located in the upper portion of the cavity block and connected to the inclined inner bore of the runner block. surrounding said runner block adjacent to said heating means, said heating means being a solid plug means located in said lower portion of said runner block, directly below said inclined bore; .