JPH05138691A - Mold for injection molding of liquid resin - Google Patents

Abstract

PURPOSE:To produce a mold for injection molding of a liquid resin in a large scale inexpensively without damage of lead wires and leakage of a resin by covering the contact face, which supports the lead wires or lead frames, of at least one part of a mold with heat resistant high-elasticity rubber. CONSTITUTION:A mold is opened by lowering a lower mold 6, and an electronic part 21 having many lead wires 20 such as a transformer and an inductor is inserted into the cavity 16 of the mold. The lead wires 20 are mounted on a fluorine-contained rubber plate 18 of a lower side mold plate 8 arranging the wires not to overlap each other. The whole lower mold 6 is then lifted to close the mold. A liquid thermosetting resin 22 like epoxy resin is injected under relatively low pressures. The injected liquid thermosetting resin 22, through sprue, runner and gate of an upper mold 7, is charged into the cavity 16 of the mold, the temperature of which is kept about 50-150 deg.C, and then cured to form a thermosetting resin coat of an insulating seal part outside the electronic part 21. Thus, the molding process is simplified to improve the productivity.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid resin injection molding die, and more particularly to an injection molding die for injection molding a liquid thermosetting insulating resin on the outside of an electronic component.

[0002]

2. Description of the Related Art In recent years, miniaturization of electronic parts used in electronic devices has been further accelerated with the progress of miniaturization of electronic devices. Surface mounting is the main method of mounting electronic components. Therefore, in order to improve resistance to reflow soldering, the outside of electronic components may be encapsulated with an insulating resin. It is being actively conducted.

In such encapsulation of electronic parts, thermosetting resin materials conventionally used for semiconductor encapsulation and the like are naturally used for reasons of reliability and the like.
When such a resin material is injection molded on the outside of the electronic component, the function of the electronic component may be impaired by the high pressure (50 to 300 Kg / cm ² ) at the time of injection.

On the other hand, a so-called liquid resin sealing method in which a liquid thermosetting insulating resin such as an epoxy resin or a silicone resin is dropped (potted) on an electronic component and cured at a relatively low temperature is used. Although it is recently being used more often because it is less likely to be damaged, there is a drawback in that the shape of the sealing portion cannot be determined because a mold is not used.

Therefore, a liquid thermosetting resin is injected and filled at a relatively low pressure (0.1 to 10 kg / cm ² ) into a cavity of a mold heated and held at a relatively low temperature (50 to 150 ° C.). A so-called liquid injection molding method has been developed, and is expected to supplement the drawbacks of various conventional methods. When actually encapsulating an electronic component by such liquid injection molding, the electronic component is attached to each contact surface of the lower mold 1 and the upper mold 2 as shown in a sectional view in FIG. The injection-molding die in which the escape groove 4 for inserting the lead wire 3 and the protrusion 5 to be fitted into the escape groove 4 is formed is used, and the lead wire 3 is clamped as follows. .. That is,
After inserting the lead wires 3 one by one into the clearance groove 4 of the lower mold 1,
The projection 5 was fitted into the escape groove 4 from above the lead wire 3 to close the mold.

[0006]

However, the electronic component generally has a large number of lead wires 3 and the lead wires 3 are
Since most of them have low positional accuracy and dimensional accuracy, some lead wires 3 are dislocated from the escape groove 4 of the lower mold 1 when the injection molding die described above is used. Therefore, there is a problem that the lead wire 3 is crushed when the mold is closed, or a liquid resin having a large fluidity leaks out from a gap between the molds formed by sandwiching the lead wire 3. Further, since the work of accurately fitting the lead wires 3 one by one into the escape groove 4 is difficult to automate, there is a problem that mass productivity is poor and the cost is increased. In addition, for electronic components of the type using a lead frame, it is necessary to form a highly accurate mold in accordance with the highly accurate lead frame, which also increases the cost.

The present invention has been made in order to solve these problems, and the encapsulation of an electronic component having a large number of lead wires with a resin is performed by using an excellent technique of so-called liquid injection molding, and quality is improved. It is an object of the present invention to provide a liquid resin injection molding die for mass-producing a good product of (1) at low cost without causing crushing of a lead wire or resin leakage.

[0008]

A liquid resin injection molding die according to the present invention holds an electronic component having a lead wire or a lead frame in a cavity and injects a liquid thermosetting resin around the cavity at a low pressure. In an injection-molding die for filling and heating and curing at low temperature, at least one of the dies has a contact surface for sandwiching the lead wire or the lead frame covered with a heat-resistant and highly elastic rubber. To do.

[0009]

In the liquid resin injection molding die described above, the contact surface of at least one die on which the lead wire or the lead frame of the electronic component is sandwiched, that is, the contact between at least one die of the upper die and the lower die. Since the contact surface is covered with a rubber material with excellent heat resistance and elasticity such as silicone rubber or fluororubber, keep this mold at a relatively low temperature of 50 to 150 ° C and keep it in its cavity. When inserting and holding an electronic component having a large number of lead wires or lead frames such as transformers and inductors, the lead wires or lead frames can be freely arranged on such a rubber coating layer. Then, when the mold is closed with the lead wire or the lead frame placed on the rubber coating layer in this way, the lead wire or the lead frame is pressed against the contact surface of the other mold and the inside of the rubber coating layer is pressed. It is pushed into and completely embedded. Therefore, the lead wire and the lead frame are not crushed, and a gap is hardly formed around the lead wire and the lead frame, so that the liquid resin injected and filled into the cavity is unlikely to leak.

[0010]

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

FIG. 1 is a front sectional view schematically showing an embodiment of a liquid resin injection molding die according to the present invention, and FIG. 2 is an enlarged view of a main part thereof. Further, FIG. 3 is a side sectional view for explaining a state in which the lead wire is clamped and fixed by the injection molding die of the embodiment.

As shown in FIG. 1, the injection mold of the embodiment comprises a lower mold 6 on the movable side and an upper mold 7 on the fixed side. The lower die 6 is composed of a lower (movable side) die plate 8 having a female die recessed on the main surface, a spacer block 9, a stripper plate 10, and a lower mounting plate 11, and the upper die 7 is a main die. Upper (fixed side) mold plate 12 in which a female mold part is provided in a position corresponding to the female mold part of the surface and stripper plate 1 for runner
3 and the sprue bush 14 and the upper mounting plate 15. The female mold part of the lower mold plate 8 and the female mold part of the upper mold plate 12 form a cavity 16 having a predetermined shape. Further, as shown in an enlarged manner in FIG. 2, a recess is formed on the surface of the lower mold plate 8 that contacts the upper mold plate 12, and a support plate 17 made of aluminum is attached to the recess by screws. .. Furthermore, this aluminum support plate 17
The height of the surface is approximately above the surface of the lower template 8 around.
A plate 18 made of fluororubber is adhered with an adhesive so that the protrusion height is 0.3 mm and the compression margin is 0.3 mm. Reference numeral 19 in the drawing denotes a knockout pin for ejecting the molded product and taking it out of the mold.

In order to perform liquid injection molding with the injection molding die thus constructed, first, the lower mold 6 is lowered to open the mold and a large number of lead wires 20 such as transformers and inductors are provided in the cavity 16. The electronic component 21 having the above is inserted, and the lead wire 20 is appropriately placed on the fluororubber plate 18 of the lower mold plate 8 so as not to overlap each other. Next, lower mold 6
Raise the whole and close the mold. At this time, as shown in cross-section in FIGS. 3 (a) and 3 (b), respectively, the lower template 8
The lead wire 20 placed on the fluororubber plate 18 is pressed by the contact surface of the upper mold plate 12 and pushed into the fluororubber plate 18 in a state where the mold is closed, and is completely embedded. Becomes Next, a liquid thermosetting resin 22 such as an epoxy resin is injected from the injection molding machine at a relatively low pressure of 0.1 to 10 kg / cm ² . The injected liquid thermosetting resin 22 is passed through the sprue, runner and gate of the upper mold 7 and then the mold cavity 16 kept at a temperature of 50 to 150 ° C.
It is injected and filled into the inside and cured, and an insulating sealing portion made of a thermosetting resin is coated and formed on the outside of the electronic component 21.

As a concrete example, a fluororubber plate 18 having a thickness of 1.5 mm is attached to the abutting surface of the lower mold plate 8 with a support plate 17 interposed between the fluororubber plate 18 and the upper mold plate 12. With a diameter of 0.
When 5 mm of lead wire 20 was sandwiched and liquid injection molding was performed in such a state, the lead wire 20 was not crushed, and almost no resin leakage occurred around the lead wire 20. Then, when molding was carried out for 1000 shots as it was, a product of good quality was practically mass-produced without damage to the fluororubber plate 18 or change in the situation.

In the above embodiment, the fluororubber plate 18 is used.
Was attached only to the lower mold plate 8 so that its surface was raised by 0.3 mm from the contact surface of the lower mold plate 8 around it, but the leakage of liquid resin was further reduced and it was even better. When high durability is required, it is desirable to attach such a fluororubber plate 18 also to the corresponding position of the upper mold plate 12. Furthermore, the compression allowance can be adjusted.

Although a plate made of fluororubber was used in the examples, since fluororubber is expensive, it can be used at a lower temperature (100
In the case of injection molding at (° C. or lower), a cheaper plate made of silicone rubber can be used in the same manner.

[0017]

As described above, in the liquid resin injection molding die of the present invention, the contact surface of at least one of the upper die and the lower die is made of a heat-resistant material such as silicone rubber or fluororubber. Since it is coated with a rubber material with excellent elasticity and elasticity, this mold is kept at a relatively low temperature of 50 to 150 ° C, and 0.1 to 0 ° C outside the electronic parts held in the cavity.
Injection of liquid thermosetting resin at a low pressure of 10 kg / cm ² ,
When so-called liquid injection molding is performed, crushing of lead wires and lead frames and leakage of liquid resin from the die contact surface are small, and a high-quality insulation-sealed product can be obtained.

Further, it is not necessary to carry out the work of fitting each lead wire of the electronic component into the escape groove,
Easy molding and high mass productivity.

[Brief description of drawings]

FIG. 1 is a front sectional view schematically showing an embodiment of a liquid resin injection molding die according to the present invention.

FIG. 2 is an enlarged sectional view of a main part of an injection molding die according to an embodiment.

FIG. 3 is a side sectional view showing a state in which a lead wire is sandwiched in an injection molding die of an embodiment, (a) is a side sectional view showing a state in which the die is opened, and (b) is a side sectional view showing a state in which the die is closed. Fig.

FIG. 4 is a side sectional view showing a state in which a lead wire is sandwiched in a conventional injection molding die, (a) is a side sectional view showing a state in which the die is opened, and (b) is a side sectional view showing a state in which the die is closed. ..

[Explanation of symbols]

 1, 6 ... Lower mold 2, 7 ... Upper mold 3, 20 ... Lead wire 4 ... Relief groove 5 ......... Projection part 8 ... Lower mold plate 11 ... Lower mounting plate 12 ... Upper template 14 ……… Sprue bush 15 ……… Upper mounting plate 16 ……… Cavity 17 ……… Aluminum support plate 18 ……… Fluorine rubber plate 19 ……… Knockout pin 21 ……… Electronic parts 22 …… ... Liquid thermosetting resin

Continuation of front page (51) Int.Cl. ⁵ Identification code Office reference number FI technical display area B29L 31:34 4F

Claims (1)

[Claims] 1. An injection molding die for holding an electronic component having a lead wire or a lead frame in a cavity, injection-filling a liquid thermosetting resin around the cavity at a low pressure, and heating and hardening at a low temperature, A liquid resin injection molding die, characterized in that a contact surface of at least one of the dies holding the lead wire or the lead frame is covered with a heat-resistant and highly elastic rubber.