JP3803650B2 - EMI gasket and EMI gasket manufacturing method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention belongs to the technical field of an EMI gasket formed by laminating a conductive elastomer on a conductive frame.
[0002]
[Prior art]
In an electronic device in which a device such as an IC or LSI is mounted on a printed circuit board or the like, means for shielding each device or shielding the electronic device and the outside is required.
[0003]
For example, Japanese Patent Laid-Open No. 2000-59065 discloses a technique using a sheet metal shield cover (paragraph 0002) and a shield cover (paragraphs 0015 to 0016) formed of a plastic material mixed with a conductive material. However, a shield cover such as a sheet metal has a structure in which a claw-like leg portion is fitted to a printed circuit board, and thus is difficult to manufacture and handle.
[0004]
On the other hand, a technique has been proposed in which holes are made in a conductive frame (metal frame or plated plastic sheet), and conductive elastomer is formed on the upper and lower surfaces to produce an EMI gasket with the conductive elastomer. (For example, Japanese Patent No. 30228804).
[0005]
[Patent Document 1]
JP 2000-59065 A (paragraph 0002, paragraphs 0015 to 0016)
[Patent Document 2]
Japanese Patent No. 30228804 (Claim 1)
[0006]
[Problems to be solved by the invention]
For example, miniaturization is progressing in small electronic devices such as mobile phones, POS terminals, and barcode readers (although miniaturization is not limited to small electronic devices), and the shielding means is small in response to miniaturization of printed circuit boards. Is required. Therefore, there is a limitation that even a gasket having a conductive elastomer formed on a conductive frame cannot be mounted on a small printed circuit board unless it is downsized, that is, the frame width of the conductive frame is narrower and the wall thickness is thinner. I came.
[0007]
However, if a hole is made in the frame in order to form a conductive elastomer on both sides of the conductive frame by injection molding or the like, there arises a problem that the strength of the frame becomes weak. Further, when the diameter of the hole is reduced in order to prevent a decrease in strength, there is a problem that it is difficult for the injected conductive elastomer to pass through the small hole and reach the opposite side well.
[0008]
[Means for Solving the Problems and Effects of the Invention]
According to a first aspect of the present invention, there is provided a method for manufacturing an EMI gasket, comprising: manufacturing a gasket comprising a conductive frame and a conductive elastomer laminated on both sides of the frame; Since the conductive elastomer is injected into the cavities on both sides of the frame from the gate arranged opposite to the outer peripheral surface of the frame, there is no need to make a hole in the frame. Therefore, the problem that the strength of the frame is weakened by the holes does not occur. In addition, since the conductive elastomer is injected from the gate into the cavities on both sides of the frame without passing through the holes in the frame, the conductive elastomer can be distributed well on both sides of the frame.
[0009]
The manufacturing method of the EMI gasket according to claim 2, in manufacturing a gasket composed of a conductive frame and a conductive elastomer laminated on both sides of the frame, a plate material which is a base material of the frame is used as a mold. Inserting conductive elastomer into the cavities on both sides of the plate material from the gate arranged opposite to the outer peripheral surface of the inserted plate material, laminating the conductive elastomer on both sides of the plate material, from the mold The plate material taken out is punched to form the frame.
[0010]
The method of claim 1 is different from the method of claim 1 in that the frame is inserted in claim 1 while the method of claim 2 inserts a plate material and laminates conductive elastomer on both sides and then punches the plate material ( For example, it is different in that it is made into a frame by punching with a press).
[0011]
Even with this method, since it is not necessary to make a hole in the frame (plate material), there is no problem that the strength of the frame is weakened by the hole. In addition, since the conductive elastomer is injected from the gate into the cavities on both sides of the plate material without passing through the holes of the plate material, the conductive elastomer can be spread well on both sides of the plate material, that is, the frame.
[0012]
Moreover, since the plate material laminated with the conductive elastomer is processed into a frame, there is an advantage that the frame width of the frame can be further narrowed.
In the manufacturing method of the EMI gasket according to claim 2, the conductive elastomer may be laminated on a wide range of the plate material as long as a portion where the die for punching and the plate material are in direct contact can be secured in the punching process. It is not efficient to laminate the conductive elastomer up to the part that will be pulled out.
[0013]
Therefore, as described in claim 3, it is preferable that the conductive elastomer is laminated only on the portion of the plate that is to be the frame, that is, the conductive elastomer is not laminated on the portion that is punched out. In this case, it is sufficient that the conductive elastomer is laminated only on a portion of the EMI gasket that requires a conductive elastomer pattern.
[0014]
The conductive frame (or plate material) may be manufactured from a copper alloy such as copper, phosphor bronze or beryllium copper, iron, aluminum, stainless steel, magnesium alloy, titanium, a plated polyester sheet, or the like.
Examples of conductive elastomers include elastic rubbers such as silicone rubber and polymer foams such as chloroprene, neoprene, samptoprene and polyurethane mixed with fine particles and fillers such as silver, copper, aluminum, nickel, carbon and graphite. Is done. Such a conductive elastomer has conductivity, elasticity, and flexibility.
[0015]
As a molding method for injecting the conductive elastomer into the cavity, a known molding method such as transfer molding or injection molding can be employed.
The EMI gasket manufacturing method according to claim 4 is the EMI gasket manufacturing method according to claim 1, 2 or 3, wherein the mold has an outer edge holding portion for holding an outer edge portion of the inserted frame or plate material. The outer edge holding portion is provided with a recess serving as a passage for the conductive elastomer injected from the gate.
[0016]
Since the outer edge portion of the frame inserted by the outer edge holding portion is held, the relative position between the frame or the plate material and the mold, that is, the shape and position of the cavity can be accurately determined. Further, it is possible to prevent the frame or the plate material from being distorted by the pressure of the injected conductive elastomer. As a result, the dimensional accuracy of the manufactured EMI gasket is improved.
[0017]
In addition, since the outer edge holding portion is provided with a recess serving as a passage for the conductive elastomer injected from the gate, the injection of the conductive elastomer is not hindered.
An EMI gasket according to claim 5 is manufactured by the manufacturing method according to claim 1, 2, 3 or 4, and comprises a conductive frame and a conductive elastomer laminated on both sides of the frame, and the conductive The elastomer portion has an outer periphery reaching portion that extends in a branch shape and reaches the outer periphery of the frame.
[0018]
Since the EMI gasket is manufactured by the manufacturing method according to the first, second, third, or fourth aspect, the above-described effect is obtained.
The conductive elastomer exhibits a good shielding effect by being shaped along the frame. However, since the conductive elastomer is injected into the cavities on both sides of the frame or the plate from the gate arranged opposite to the outer peripheral surface, a portion where the conductive elastomer flowing out from the gate flows in the width direction of the frame is formed. This portion becomes the outer periphery reaching portion. In other words, if the EMI gasket has an outer periphery reaching portion, it is presumed that the EMI gasket was manufactured by the manufacturing method according to claim 1, 2, 3 or 4.
[0019]
The EMI gasket according to claim 6 is characterized in that, in the EMI gasket according to claim 5, the wall thickness of the outer periphery reaching portion is thinner than other portions.
Since the thickness of the outer periphery reaching portion has little relation to the shielding effect, if the thickness of the outer periphery reaching portion is made thinner than the thickness of other portions related to the shielding effect, the EMI gasket is attached to the electronic device. The adhesion of the part related to the shielding effect is improved, and the shielding effect is also improved.
[0020]
The EMI gasket according to claim 7 is the EMI gasket according to claim 5 or 6, characterized in that the outer peripheral reaching portions on both sides are arranged in series via a bridge portion attached to the outer peripheral surface of the frame. To do. That is, it is a structure in which the conductive elastomer exiting from the same gate is divided into both sides at the outer peripheral surface portion, and traces flowing into each cavity remain as bridge portions. The bridge portion can be used as an engaging portion when the EMI gasket is attached to the housing by engagement or the like. Further, when the bridge portion becomes unnecessary depending on the use of the EMI gasket or the mounting structure, it can be removed.
[0021]
DETAILED DESCRIPTION OF THE INVENTION
Next, embodiments of the present invention will be described with reference to some examples.
[0022]
[Example 1]
FIG. 1 is a plan view of the EMI gasket 10 and FIG. 2 is a cross-sectional view taken along the line AA. As shown in these drawings, the EMI gasket 10 is composed of a conductive frame 12 and a conductive elastomer 14 laminated on both sides of the frame 12 (in this embodiment, a material in which metal fine particles are mixed in silicone rubber is used). It is configured.
[0023]
The frame 12 of the present embodiment is made of a phosphor bronze sheet metal (the sheet pressure is about 0.1 to 1.0 mm, in many cases about 0.3 to 0.5 mm depending on the usage situation) by pressing. It is punched out into a grid. A window-like space formed by punching becomes a device accommodating portion 16 of a device such as an IC or LSI, and each of the annularly closed frame portions 18 functions as a shield. The size of the frame 12 and the shape of each housing portion 16 are determined according to the shape of a printed circuit board (not shown), the arrangement of devices on the printed circuit board, the shape of the device, etc., and are not uniform.
[0024]
The conductive elastomer 14 is laminated on both sides of the frame 12 as well shown in FIG. The planar projection shape follows the same shape of the frame 12.
The width of the conductive elastomer 14 on each frame portion 18 is smaller than the width of the frame portion 18 (the width of the frame portion 18 is 0.3 to 3.0 mm depending on the use scene or the like, and in many cases 0.4). The surface is exposed at the outer edge portion 20 and the inner edge portion 24 of the frame portion 18 (the frame 12) on both sides of the belt-shaped conductive elastomer 14.
[0025]
Of the exposed portion of the surface, the outer edge portion 20 along the outer periphery of the frame 12 has three portions each covered by the outer periphery reaching portion 22 of the conductive elastomer 14 on both long sides of the frame 12. is there. The outer periphery reaching portion 22 extends from the main body portion of the conductive elastomer 14 in a branch shape and reaches the outer periphery of the frame 12. Note that, as shown in FIG. 2, the thickness of the outer periphery reaching portion 22 is smaller than that of the main body portion.
[0026]
On the other hand, the inner edge portion 24 on the side of the accommodating portion 16 does not have a branch-like portion like the outer periphery reaching portion 22.
The exposure of the surface of the frame 12 at the outer edge portion 20 and the inner edge portion 24 originates from the molding operation for forming the conductive elastomer 14 on the frame 12.
[0027]
As shown in FIG. 3, the EMI gasket 10 of the present embodiment is formed by applying a pressed frame 12 to a mold 26 composed of an upper mold 26a and a lower mold 26b (one is a fixed mold and the other is a movable mold). It is manufactured by laminating the conductive elastomer 14 on the frame 12 by inserting and injecting the conductive elastomer 14.
[0028]
Cavities 28 for injecting the conductive elastomer 14 are formed above and below the frame 12 inserted into the mold 26.
Further, the upper mold 26 a and the lower mold 26 b are provided with a recess 30 corresponding to the outer periphery reaching portion 22, and the cavity 28 communicates with the gate 32 through the recess 30.
[0029]
Although illustration of details is omitted, the gate 32 is provided on the upper die 26a or the lower die 26b (which becomes a fixed die), and as shown in FIG. 3, at a position facing the outer peripheral surface 13 of the frame 12 when the die is closed. It is arranged.
On the other hand, the outer edge portion 20 and the inner edge portion 24 are tightly held between the upper mold 26a and the lower mold 26b (excluding the recess 30).
[0030]
With this configuration, when the conductive elastomer 14 is injected from the gate 32, the conductive elastomer 14 flows from the upper and lower recesses 30 into the upper and lower cavities 28. An appropriate amount of the conductive elastomer 14 is filled in the cavity 28 and gate-cut. After the conductive elastomer 14 is solidified, the mold is opened and the EMI gasket 10 is taken out.
[0031]
In this state, as shown in FIG. 3B, the bridge portion 34 between the gate 32 and the recess 30 is attached to the outer peripheral surface 13 of the frame 12 in a state where the upper and lower outer periphery reaching portions 22 are connected to each other. . The bridge portion 34 may be left as it is, but if this is deleted, the shape shown in FIGS. 1 and 2 is obtained.
[0032]
As described above, the EMI gasket 10 inserts the conductive frame 12 into the mold 26 and conducts from the gate 32 disposed opposite to the outer peripheral surface 13 of the inserted frame 12 to the cavities 28 on both sides of the frame 12. Since the conductive elastomer 14 is manufactured by injection and injection, a hole, a notch or the like for guiding the conductive elastomer 14 to the other surface is provided as in the case of injection with a gate arranged on one side of the frame 12. There is no need to provide the frame 12.
[0033]
Therefore, the problem that the strength of the frame 12 becomes weak due to holes or the like does not occur. Further, since the conductive elastomer 14 is injected from the gate 32 into the cavities 28 on both sides of the frame 12 without passing through the holes or the like of the frame 12, the conductive elastomer 14 can be spread well on both sides of the frame 12.
[0034]
Since the mold 26 is provided with a recess 30 that serves as a passage for the conductive elastomer 14 injected from the gate 32, injection of the conductive elastomer 14 is not hindered by clamping.
When injecting the conductive elastomer 14, the outer edge 20 and the inner edge 24 of the frame 12 inserted into the mold 26 are held by the mold 26, so that the relative position between the frame 12 and the mold 26, that is, the cavity 28. Accurate shape and position. Further, the frame 12 can be prevented from being distorted by the pressure of the injected conductive elastomer 14 or the like. As a result, the dimensional accuracy of the EMI gasket 10 is improved.
[0035]
The same effect can be obtained by a configuration in which only the outer edge portion 20 of the frame 12 is held by the mold 26, that is, a configuration in which the exposed portion of the frame 12 corresponding to the inner edge portion 24 is not provided.
The EMI gasket 10 is disposed on a printed circuit board so that a device such as an IC or LSI is accommodated in the accommodating portion 16, and a conductive casing or the like is in pressure contact with the upper surface side. That is, since the accommodating portion 16 is sandwiched between the printed circuit board and a conductor such as a housing and the housing portion 16 is closed, the devices are shielded from each other, and the electronic device and the outside are shielded. At this time, since the conductive elastomer 14 is in intimate contact with the lower printed circuit board and the upper conductor, the shielding effect is ensured.
[0036]
By the way, a branch-like outer periphery reaching portion 22 is formed in the EMI gasket 10 corresponding to the recess 30 that becomes a passage of the conductive elastomer 14 at the time of molding. The thickness of the outer periphery reaching portion 22 is larger than that of other portions. Therefore, when the EMI gasket 10 is mounted on an electronic device, the adhesion of the main body of the conductive elastomer 14 related to the shielding effect is not hindered. Therefore, the adhesiveness of the conductive elastomer 14 is good and the shielding effect is also good.
[0037]
On the outer peripheral surface 13 of the EMI gasket 10 taken out from the mold 26, traces of the conductive elastomer 14 coming out of the gate 32 being divided into upper and lower portions at the outer peripheral surface 13 portion and flowing into the cavities 28 become bridge portions 34. Remaining. The bridge portion 34 can be used as an engaging portion when the EMI gasket 10 is attached to a housing or the like, but may be removed when the bridge portion 34 is unnecessary depending on the use or mounting structure of the EMI gasket 10.
[0038]
[Modification]
The bridge portion 34 can be modified as shown in FIGS.
That is, the notch 35 is provided in the portion of the frame 12 that faces the gate 32. Then, the conductive elastomer 14 injected from the gate 32 is diverted from the notch 35 and flows into the cavity 28 through the recess 30. Therefore, the bridge portion 34 is not protruded from the outer peripheral surface 13, or at least the protrusion amount can be made extremely small.
[0039]
[Example 2]
The EMI gasket 11 shown in FIGS. 6 and 7 is obtained by injection-molding the conductive elastomer 14 by holding the inserted frame 12 by holding pins (not shown) provided in a mold. The structure of the mold (except for the part related to the holding pins) and the injection molding procedure are the same as in the first embodiment, and therefore illustration and description thereof are omitted.
[0040]
For this reason, the trace of the restraining pin is left as the pin trace 37 on the conductive elastomer 14 of the EMI gasket 11.
By using the holding pins, the exposed portions of the frame 12 such as the outer edge portion 20 and the inner edge portion 24 can be formed only by the pin marks 37, and the width of the conductive elastomer 14 can be matched with the width of the frame portion 18. That is, since the wall thickness (width) of the conductive elastomer 14 can be maximized, the shielding effect becomes better. It goes without saying that the same effects as those of the first embodiment are obtained.
[0041]
As mentioned above, although embodiment of this invention was described according to the Example etc., it cannot be overemphasized that this invention is not limited to these examples, and can be implemented variously in the range which does not deviate from the summary of this invention.
For example, in the embodiment, the configuration is such that the conductive elastomer 14 is injected from six gates 32 to one frame 12 (the outer periphery reaching portion 22 can be provided at six locations on one side). What is necessary is just to set suitably according to a shape, the quantity of the conductive elastomer 14 to inject, etc., and it is not necessarily restricted to six places.
[0042]
In the embodiment, the method of manufacturing the EMI gasket by inserting the frame and injection molding was described. However, the plate material as the base material of the frame was inserted and injection molded, and the conductive elastomer was laminated on both sides of the plate material. Later, it is possible to adopt a method of punching a plate material with a press, for example, into a frame. Even in this method, the same effect as the embodiment can be obtained. Further, since the frame is processed after the injection molding, the frame width (the width of the frame portion 18 in the embodiment) can be further reduced.
[Brief description of the drawings]
FIG. 1 is a plan view of an EMI gasket of Example 1. FIG.
FIG. 2 is a cross-sectional view taken along line AA in FIG.
3 is an explanatory view of injection molding of an EMI gasket of Example 1. FIG.
FIG. 4 is a partial plan view of a modified EMI gasket.
FIG. 5 is a partial cross-sectional view of a modified EMI gasket.
6 is a plan view of an EMI gasket of Example 2. FIG.
7 is a cross-sectional view taken along line BB in FIG.
[Explanation of symbols]
10, 11 EMI gasket 12 Frame 13 Outer peripheral surface 14 Conductive elastomer 16 Housing part 18 Frame part 20 Outer edge part 22 Outer peripheral part 24 Inner edge part 26 Mold 28 Cavity 30 Recess 32 Gate 34 Bridge part 35 Notch

Claims (7)

In manufacturing a gasket comprising a conductive frame and a conductive elastomer laminated on both sides of the frame,
Insert the frame into the mold,
A method for producing an EMI gasket, characterized in that a conductive elastomer is injected into cavities on both sides of the frame from gates arranged to face the outer peripheral surface of the inserted frame. In manufacturing a gasket comprising a conductive frame and a conductive elastomer laminated on both sides of the frame,
Insert the plate that is the base material of the frame into the mold,
Injecting a conductive elastomer into the cavities on both sides of the plate material from the gate arranged facing the outer peripheral surface of the inserted plate material, laminating the conductive elastomer on both sides of the plate material,
A method of manufacturing an EMI gasket, wherein the frame is formed by punching the plate material taken out from the mold. In the manufacturing method of the EMI gasket of Claim 2,
A method of manufacturing an EMI gasket, wherein the conductive elastomer is laminated only on a portion of the plate material that is to be the frame. In the manufacturing method of EMI gasket of Claim 1, 2, or 3,
The mold is provided with an outer edge holding portion for holding an outer edge portion of the inserted frame or plate material, and the outer edge holding portion is provided with a recess serving as a passage for the conductive elastomer injected from the gate. A method for producing an EMI gasket. It is manufactured by the manufacturing method according to claim 1, 2, 3, or 4.
A conductive frame;
It consists of a conductive elastomer laminated on both sides of the frame,
The EMI gasket according to claim 1, wherein the conductive elastomer portion includes an outer periphery reaching portion that extends in a branch shape and reaches the outer periphery of the frame. The EMI gasket of claim 5,
An EMI gasket characterized in that a thickness of the outer periphery reaching portion is thinner than other portions. The EMI gasket according to claim 5 or 6,
The EMI gasket, wherein the outer peripheral reaching parts on both sides are arranged in series via a bridge part attached to the outer peripheral surface of the frame.

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