JP3536999B2 - Resin molding equipment - Google Patents

Abstract

PURPOSE: To obtain a resin molding apparatus of the so-called multiplunger system pressing the resin tablets charged in pots by plungers to inject them into cavities by forming a large number of pots to one mold and directly connecting cavities to the respective pots. CONSTITUTION: In a resin mold apparatus wherein a large number of pots are bored in the mating surface of one of a pair of upper end lower molds 27, 38 on one straight line and the cavities 29 communicating with the respective pots are formed to at least one of the mating surfaces of the molds so as to approach each other and the resin tablets 42 supplied into the pots 28 are pressed by plungers 30 to be fluidized to be injected into the cavities, the pressing operation timings of the plungers 30 are shifted. Pressing operation is successively performed from the plunger 30 inserted in the pot 28 becoming a standard to the adjacent plungers.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method in which a plurality of pots are formed in one mold, cavities are directly connected to the pots, and a resin tablet put into the pots is pressed by a plunger and injected into the cavities. The present invention relates to a so-called multi-plunger type resin molding device.

[0002]

2. Description of the Related Art In general, a resin mold type electronic component mounts an electronic component main body on an island by using a lead frame in which an island and a large number of leads are integrated, and electrically connects an electrode and a lead of the electronic component main body. The main part on the lead frame including the electronic component body is sealed with resin, and unnecessary parts of the lead frame exposed from the exterior resin are cut and removed to be separated into individual electronic parts and manufactured. . FIG. 3 shows an example of a resin molding device for coating a main part on a lead frame with a resin. In the figure, reference numeral 1 denotes a lead frame in which a heat radiating plate (island) 2 and a large number of leads 3 are integrated, and an electronic component main body 4 is mounted on the heat radiating plate 2 in a previous process. Are connected to the leads 3 by thin metal wires 5. Reference numeral 6 denotes a lower die on which the lead frame 1 is placed. A lower part 7 is formed at the center of the upper surface, and a runner 8 is formed in communication with the lower part 7. A plurality of cavities 9 are formed along the runner 8. Are formed, and the runner 8 and the cavity 9 are communicated via the gate 10. Reference numeral 11 denotes an upper mold disposed above the lower mold, which penetrates the pot 12 and has its lower end opened at a position facing the cull portion 7. Reference numeral 13 denotes a resin tablet put into a space surrounded by the mold pot 12 and the cull portion 7 which are clamped, and 14 denotes a plunger for pressing the resin tablet 13.

The upper and lower dies 6 and 11 are supported by a fixed plate and a movable plate (not shown) and are heated by heating means.
The lead frame 1 is clamped in a state where the lead frame 1 is accommodated. In the illustrated example, the cross section along the runner 8 is shown on the left side from the AA plane,
On the right side of the plane, a cross section orthogonal to the runner 8 is shown, and a large number of runners 8, cavities 9, and gates 10 are formed in an actual device. In this apparatus, the lead frame 1 is clamped in the state shown in FIG. 3, the resin tablet 13 is fluidized by pressurizing and heating with a plunger 14, and the fluidized resin is sent into the cavity 9, and the lead frame 1 is pressed. Can be resin-coated. In this apparatus, the resin traveling in the runner 8 is sequentially injected into a number of cavities 9 arranged along the runner 8, but when the resin reaches the end of the runner 8, the resin is completely filled in all the cavities 9. The plunger 14 is not injected until the resin reaches the end of the runner 8.
Is transmitted to the resin to be injected into the cavity 9, and the injection of the resin into the cavity 9 is accelerated. by the way,
The thermosetting resin fluidizes due to a sharp decrease in the viscosity of the resin tablet when heated and pressurized, but the fluidized resin increases in viscosity over time and decreases in fluidity.

Therefore, the cavity 9 for the runner 8 is
The viscosity of the resin injected differs depending on the position of the resin, and the resin injected into the cavity 9 after a lapse of time has poor fluidity.
There is a problem that an air vent (not shown) for letting out the air trapped inside closes first, causing voids in the resin. On the other hand, in order to collectively cover many lead frames 1 with resin, it is necessary to lengthen the length of the runner 8, and the cull portion 7 is required to efficiently transmit the pressing force from the plunger 14 to the runner 8. It is formed in a concave curve.
Since the runner 8 and the cull portion 7 do not contribute to the molding, there is a problem that the use rate of the resin is reduced when a large number of lead frames are to be collectively processed. In order to solve such a problem, a so-called multi-plunger type resin molding apparatus in which cavities are directly connected to a large number of pots and plungers are inserted into the pots has been used.

An example of this device will be described with reference to FIG. In the figure, reference numeral 15 denotes a lower mold, which has a large number of pots 16, 16,... Numerals 17 are cavities formed in the vicinity of each of the pots 16, and are arranged on one side of each of the pots 16 in the illustrated example. Reference numeral 18 denotes a runner that communicates the pot 16 with the cavity 17, and 19 denotes a plunger inserted into each pot 16 from below. Each plunger 19 is connected to a cylinder 21 for driving the plunger via a rod 20. 22
Is an upper mold disposed above the lower mold 15. Although not shown, a cull portion is formed at a position facing the pot 16, and an upper cavity is formed at a position facing the lower cavity 17. The upper and lower dies 15 and 22 are fixed to a fixed platen and a movable platen (not shown), respectively, and heated by the heating means so that the abutment surfaces are relatively close to and separated from each other.

In this apparatus, a lead frame (not shown) is placed on a cavity 17 of a lower mold 15 and a plunger 1 is mounted.
9 is lowered and the resin tablet 23 is put into the space formed between the pot 16 and the upper and lower dies 15 and 22 to clamp the lead frame and clamp the mold to operate the cylinder 21 to raise the plunger 19. Then, the resin tablet 23 is pressurized, heated and fluidized. The fluidized resin is runner 1
Air is injected into each cavity 17 via 8, and the air compressed by the resin confined in the cavity 17 and injected is expelled from an air vent (not shown) to cover the main part of the lead frame. This device has one pot 1
Since the distance between the cavity 6 and the cavity 17 connected thereto is short, the injection pressure of the resin can be small, and the cull portion and the runner 18 can be made sufficiently smaller than the total capacity of the cavity 17.
The utilization rate of the resin can be improved as compared with a resin molding device having a large number of cavities formed along the runner. An apparatus related to the apparatus shown in FIG. 4 is disclosed in, for example, Japanese Patent Application Laid-Open No. 1-103417.

[0007]

By the way, in the apparatus shown in FIG. 4, resin injection into the cavity proceeds in accordance with the operation of the plunger, but if the operating speed of the plunger is increased in order to shorten the resin molding time. In some cases, defects such as void defects involving air in the molding resin and unfilling in which the resin is not completely injected into the cavity may occur. The inventor has found that void defects and unfilled portions are concentrated in the cavities connected to the middle pot among a large number of pots arranged in a straight line. Was confirmed to be remarkable. Such a phenomenon is caused by the resin mold device disclosed in the above-mentioned publication, that is, connecting one cavity to one pot and driving each plunger inserted in each pot by an independent cylinder to control the pressure of each plunger. It is thought that this does not occur in a device that detects the speed and controls each cylinder optimally.However, such a device requires a large number of cylinders, requires detection devices and control devices, and complicates the device. The technology could not be applied immediately.

[0008]

SUMMARY OF THE INVENTION The present invention has been proposed for the purpose of solving the above-mentioned problems, and a plurality of pots are opened along one straight line on one of the upper and lower molds at the abutment surface of the mold. In a resin molding apparatus, a cavity communicating with each pot is formed close to each other on at least one of the mold abutting surfaces, and the resin tablet supplied to the pot is pressurized with a plunger, fluidized, and injected into the cavity. There is provided a resin molding apparatus characterized in that the timing of the pressing operation of each plunger is shifted. The timing may be set such that the plunger inserted into the pot serving as a reference is successively pressed to an adjacent plunger.

[0009]

According to the present invention, air can be satisfactorily exhausted from the cavity when the resin is injected into the adjacent cavity by the above-mentioned means for solving the problem. Can be molded.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. In the drawing, reference numeral 27 denotes a lower mold, which has a large number of pots 28, 28,... Numerals 29 are cavities formed in the vicinity of each pot 28, and two cavities are arranged on one side of each pot 28 in the illustrated example. 30 is a plunger inserted into each pot 28 from below, and each plunger 30 is a rod 31
Are connected. A flange 32 serving as a stopper is formed at an axially intermediate portion of the rod 31, and a piston 33 is formed at a lower end. Reference numeral 34 denotes an engagement plate provided with an insertion hole 35 into which the piston 33 of the rod 31 is inserted, and a coil spring 36 is inserted into the insertion hole 35 so as to elastically push the rod 31 upward. 37
Denotes a plunger driving cylinder that drives the engagement plate 34 to move the plungers 30 up and down in a lump. Numeral 38 denotes an upper die, which is shown upside down for illustrative purposes to show an abutting surface, but is arranged above the lower die 27 and forms a cull portion 39 at a position facing the pot 28. The upper cavity 4 is located at a position facing the lower cavity 29.
0 is formed, and the cull portion 39 and the cavity 40 are connected by the runner 41, respectively.

The upper and lower dies 27 and 38 are fixed to a fixed plate and a movable plate (not shown), respectively, and heated by heating means so that the abutment surfaces are relatively close to and separated from each other. Upper and lower molds 27, 38
The air in the cavity compressed by resin injection is exhausted from an air vent (not shown) while the mold is clamped by holding the lead frame. It is difficult to make an abutment, and a narrow gap is also formed in the abutment surface between the substantially adjacent cavities, and the air compressed in the cavities is also discharged from this gap. The present invention has been made to find that the minute gaps between the cavities cause molding problems such as voids and unfilling. The feature of the present invention resides in the drive mechanism of each plunger 30, and more specifically, among the plungers 30 inserted into a large number of pots 28 arranged in a straight line, That is, the timing is shifted so as to drive the plunger 30 inserted into the plunger 28.

That is, as shown in FIG. 2, among the pots 28, 28,.
The plungers 30a inserted into the central pot 28a and the plungers 30b inserted into the pots 28b at both ends in the arrangement direction (only one end is shown in the illustrated example) will be described. Each plunger 30a, 30b and each flange 32a, 32b will be described.
Are set to the same length, but each flange 30
The length from a, 30b to each of the pistons 33a, 33b is set longer in the center plunger 30a. The coil springs 35 have the same length and the same spring constant. The insertion holes 35 of the engagement plate 34 are set to the same depth, and the drive cylinder 3
7 is in the lowermost position where it is not operated, the height of the plunger 30 in the pot 28 is gradually reduced from the center pot 28 toward both sides, that is, the height of the pot 28 to which the resin tablet 42 is supplied. The depth is set so as to increase gradually. The operation of this device will be described below. First, as shown in FIG. 2, the upper and lower molds 27 and 38 are opened, and a lead frame (not shown) is placed at a predetermined position on the lower mold 27 with the plunger 30 lowered to the lowermost position. The resin tablet 42 is supplied to each pot 28, the upper and lower molds 27 and 38 are brought close to each other, and the lead frame is clamped and clamped.

At this point, each flange 32a, 32b
Are separated from the engagement plate 34 and each plunger 30
The displacement applied to the a and 30b from the engagement plate 34 via the coil spring 36a is the same. When the engagement plate 34 is raised from this state, each plunger 3
0a and 30b rise and the resin 4 in the central pot 30a
2a is sandwiched between the plunger 30a and the cull portion 39a, the coil spring 36a is compressed, and the resin tablet 42 is compressed.
A pressure is applied to a. On the other hand, the other plunger 30b raises the resin tablet 42b as it is. Therefore, the resin tablet 42a of the central pot 28a is fluidized and injected into the cavity. Further engaging plate 3
When 4 rises, the central plunger 30a has an increased elastic force, the pressing force increases, and the fluidized resin flows into the cavities 29, 40. When the resin tablet 42b of the pot 28a at the center and the pot 28b adjacent to the pot 28b are clamped by the plunger 30b and the cull portion 39b due to the rise of the engagement plate 34, the elastic force due to the compression of the coil spring 36b acts to press the resin tablet 42b. Fluidize.
The fluidization of the resin is transmitted to the adjacent pot by raising the engagement plate 34, and the resin is sequentially injected into the cavities 29 and 40 where the resin injection is started first and the adjacent cavities.

At this time, the flange 32a of the rod 31a connected to the central plunger 30a is directly engaged with the surface of the engagement plate 34, the pushing force is directly transmitted to the plunger 30a, and the adjacent flange is also engaged. The push-up force from the engagement plate 34 is transmitted to all the plungers at the final stage of the resin injection by engaging with the mating plate 34. The resin injected into the cavity is suppressed from the air compressed by the resin which is confined in the cavity and injected. At this time, the compressed air is discharged from an air vent (not shown) having a small cross-sectional area communicating the cavity with the outside of the mold. On the other hand, the air compressed in the cavity is also discharged from a narrow gap formed substantially at the abutment surface between the adjacent cavities. And resin injection is performed smoothly. This gap is
Because of the small size, the resin injected into the cavity gradually closes the gap, but the resin in the gap is immediately cured by directly receiving the heat from the mold, and there is no risk of resin leakage.

In the resin molding apparatus according to the present invention, since the resin is injected sequentially from the center cavity to the cavities on both sides, the gap between the adjacent cavities is also sequentially closed from the center side. Is sufficiently secured in response to the resin injection, so that the compressed air in the cavity can be efficiently expelled, and the resin injection can be performed smoothly even when the operating speed of the plunger is increased. Note that the present invention is not limited to the above-described embodiment. For example, the operation order of the plungers is such that not only the plungers in the center of the array are sequentially operated from both sides, but also the plungers inserted into the reference pot. It is only necessary to sequentially press the plungers adjacent to each other, and it is also possible to operate from one end of the arrangement to the other end,
A plurality of reference pots can be set instead of one. The driving mechanism of the plunger is not limited to the embodiment as long as the operation timing of the plunger can be shifted. For example, each plunger or a set of several plungers is driven by an independent cylinder. Deformation such as doing is also possible.

[0016]

As described above, according to the present invention, even if the operating speed of the plunger is increased, defects such as void defects and unfilling do not occur, and the resin molding time can be reduced.

[Brief description of the drawings]

FIG. 1 is a sectional perspective view of a main part showing an embodiment of a resin molding apparatus according to the present invention.

FIG. 2 is a sectional side view of an essential part for explaining the operation of the apparatus in FIG. 1;

FIG. 3 is a side sectional view showing an example of a conventional resin molding apparatus.

FIG. 4 is a partially sectional perspective view showing another example of a conventional resin molding apparatus.

[Explanation of symbols]

27 Lower mold 28 pots 29 cavities 30 plunger 38 Upper mold 42 resin tablet

Claims (1)

(57) [Claims] (1) One of a pair of upper and lower molds has one
Open multiple pots along the straight line, and
A cavity communicating with at least one of the pots
Formed close to each other and supplied to each of the above pots
Press the resin tablet with a plunger to fluidize it,
In the resin molding apparatus for injecting into the cavity, the plunger inserted into the reference pot located substantially at the center of the straight line is first started to perform a pressurizing operation, and then from there to the adjacent plunger, Delay the timing
A resin press apparatus for starting a pressurizing operation by pressing.