JPH05225853A - Illuminated switch unit - Google Patents

Abstract

PURPOSE:To enable further thinning and prevent the pollution of a circuit pattern by the diffusion of the silicon from a silicon dam and improve the work efficiency of an LED bare chip element sealing process. CONSTITUTION:An LED bare chip element 7 is mounted on a one-sided printed wiring board where a metallic wiring layer is provided only on one side. A single-sided printed wiring board A, which is provided with an opening 31 conforming to an LED element mounting part, and a contact electrode circuit 5 for external connection, and others, is junctioned onto this printed wiring board B by an adhesive 19. And, the LED bare chip element 7 is sealed with light diffusing resin 9. Moreover, a dome-shaped click spring 6 is mounted on the printed wiring board A, with the top conforming to the center of the contact electrode circuit 5.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an illumination switch having a click spring for obtaining a click feeling when a key input section (switch) is pressed and an LED (light emitting diode) light source for illuminating a key operation section. The present invention relates to a unit, and particularly to an illumination switch unit suitable for thinning.

[0002]

2. Description of the Related Art Generally, in a thin illuminated switch unit, a chip LED is mounted in the vicinity of a key input portion of a base printed wiring board, and the key surface is diffused by guiding light from the LED to the key operation portion. To illuminate. In recent years, with the demand for further thinning of the switch unit, there has been proposed an illuminated switch unit in which an LED bare chip element is used instead of the chip LED and the LED bare chip element is directly mounted on a base printed wiring board.

FIG. 4 is a sectional view showing a conventional illumination switch unit of this type.

The printed wiring board 1 is a double-sided board having metal wiring layers provided on both sides thereof, and an insulating layer 2 made of an insulating material such as a polyimide film, and an upper surface (front surface) side metal wiring layer of the insulating layer 2. The conductive circuit 3a and the contact electrode circuit portion 5 provided on the insulating layer 2, the conductive circuit 3b provided on the lower surface (rear surface) side metal wiring layer of the insulating layer 2, and the LED bare chip element mounting portion (hereinafter, LED) on the insulating layer 2. The resist material 4a is selectively formed on a region other than the element mounting portion) and the electrode circuit portion 5 and the like, and the resist material 4b is formed on the lower surface side of the insulating layer 2. The specific conductive circuits 3a and 3b on the front surface and the back surface are electrically connected to each other by through holes 10 selectively provided in the insulating layer 2. Further, the electrode circuit portion 5 is composed of, for example, a pair of electrodes which are formed in a comb shape and whose comb tooth portions are alternately arranged.

The LED bare chip element 7 is directly mounted on the printed wiring board 1 and electrically connected to the conductive circuit 3a by a conductive wire 8. This LED
A dam 12 made of silicon is provided on the resist material 4a around the bare chip element 7. And LED
The bare chip element 7 and the wire 8 are sealed by the light diffusion resin 9 injected inside the dam 12.

On the other hand, on the contact electrode circuit portion 5, a click spring 6 made of a conductive metal formed in a dome shape has its top aligned with the center position of the electrode circuit portion 5 and its edge portion resist 4a. It is placed on top.

In this way, on the printed wiring board 1 on which the LED bare chip element 7 and the click spring 6 are mounted, the light guide diffusion resin plate 13 in which the LED element mounting portion and the click spring mounting portion are selectively opened, LED on the bottom side
A rubber foam 14 and a surface sheet 15 provided with unevenness corresponding to the bare chip element 7 and the click spring 6 are laminated.

The click spring 6 is formed by squeezing a metal plate having a strong spring property into a dome shape.
The click feeling when the switch is pressed is obtained by the deformation (click action) of the click spring 6. That is, when the click spring 6 is pressed through the surface sheet 15 and the rubber foam 14, the center of the click spring 6 is displaced and deformed, and the electrode spring 5 comes into contact with the electrode circuit portion 5 to turn on the electrode circuit portion 5. .. In this case, since the deformation of the click spring 6 is such that the center of the dome top is dented, a click feeling is obtained during this deformation.

[0009]

However, the conventional illumination switch unit has the following problems.
That is, in order to securely seal the LED bare chip element 7 and the bonding wire 8 with the light diffusing resin 9 in the LED element mounting portion, the height of the light diffusing resin 9 must be about 0.7 mm or more. For this reason, although the total thickness of the unit can be reduced to about half as compared with the case where the chip LED is used, it is difficult to reduce the thickness to about 1.2 mm or less, which hinders the further reduction of the illumination switch unit. ..

Further, the silicon dam 12 provided for defining the resin sealing shape is required to prevent the circuit surface from being contaminated by the diffusion of silicon when the silicon resin is cured, and therefore the LED bare chip element 7 and the conductive circuit 3a are required. Since it is necessary to form the transfer stamps one by one after the wire bonding and the wire bonding, the workability of the resin sealing step is hindered.

Further, in the conventional illumination switch unit, there is a drawback that a satisfactory click feeling cannot be obtained. The reason is shown below.

FIG. 5 is a schematic view showing the deformation behavior of the click spring, and FIG. 6 is a graph showing a load displacement curve of the click spring. In FIG. 5, reference numeral 26 shows the appearance of the click spring in the stationary state, and reference numeral 27 shows the bottom surface of the click spring 6 in the stationary state. Also, reference numeral 29a and reference numeral 3
Reference numeral 1 indicates the surface of the spring when the click spring is deformed.

When the click spring 6 is deformed from the stationary state, the deformed state of the spring after completion of the click action is, as indicated by reference numeral 31, the central portion thereof is below the bottom surface 27 of the spring in the stationary state. .. That is, the center of the spring 6 is located below the bottom surface 27 of the spring, and the deformation of the spring 6 reaches an equilibrium state. Therefore, what is indicated by reference numeral 31 in FIG. 5 is the original click action stroke of the click spring 6, the curve indicated by reference numeral 30 in FIG. 6 is the load displacement curve, and the one indicated by reference numeral E is the load at that time. It will change.

However, conventionally, when the click spring 6 is pressed, as shown by reference numeral 29a in FIG. 5, the spring 6 comes into contact with the electrode circuit portion 5 to prevent the spring from being deformed, and the spring is deformed. Stop at the bottom or the electrode circuit surface. Therefore, the displacement amount of the spring becomes C in FIG. 5, which is smaller than the original displacement amount by D. Therefore, the load displacement curve and the load change when the spring 6 is pressed are shown by reference numerals 29b and C in FIG. 6, respectively. in this way,
When the spring 6 is deformed by a key operation and the spring 6 and the electrode circuit portion 5 come into contact with each other to turn on, the downward displacement of the spring 6 ends at the position indicated by reference numeral 28 in FIG. Therefore, in the conventional switch unit, there is a drawback in that the click feeling at the time of designing the click spring as shown by reference numeral 30 in FIG. 6 cannot be obtained.

In order to improve the feeling of click, there is also a method of increasing the amount of displacement by strengthening the narrowed shape of the click spring. However, if this is done, the thickness of the click spring is increased, which hinders the switch unit from becoming thinner. The maximum load inherent to the click spring is significantly increased, and the durability is deteriorated, which greatly affects the entire unit. This is particularly remarkable in the case of a small switch unit using a click spring having a small diameter.

The present invention has been made in view of the above problems, and it is possible to further reduce the thickness as compared with the prior art, and to more reliably prevent the contamination of the circuit due to the diffusion of silicon from the dam. It is an object of the present invention to provide an illumination switch unit that can improve workability in a resin sealing process and can obtain a better click feeling.

[0017]

The illuminated switch unit according to the present invention includes a first printed wiring board having a circuit pattern formed only on one surface side thereof, and the one of the first printed wiring boards. LED mounted at a predetermined position on the surface
The bare chip element is provided with an opening in a region matching the bare chip element mounting portion of the LED and the first chip
Second printed wiring board having a circuit pattern formed only on the surface opposite to the one surface of the printed wiring board, and selectively arranged on the second printed wiring board. And a click spring provided.

[0018]

In the present invention, the LED bare chip element is mounted at a predetermined position on the first printed wiring board, and an area matching the LED bare chip element mounting portion is opened on the first printed wiring board. The formed second printed wiring board is joined. This second printed wiring board is a single-sided printed wiring board in which a circuit pattern is provided only on the surface opposite to the joining surface. That is, in the illumination switch unit according to the present invention, the LED bare chip element is mounted at a position lower than the surface of the second printed wiring board by an amount corresponding to the thickness thereof, so that the total thickness of the illumination switch unit is reduced. It can be reduced as compared with the conventional case. Further, since the distance between the silicon resin dam provided on the wiring board near the LED bare chip element and the circuit pattern is increased by the amount corresponding to the thickness of the second printed wiring board,
It is possible to prevent the contamination of the circuit due to the diffusion of silicon. Therefore, a plurality of silicon dams can be simultaneously formed by printing, for example, and workability in the resin sealing step can be improved.

By providing a connection hole in the second printed wiring board for electrically connecting the circuit pattern of the first printed wiring board and the circuit pattern of the second printed wiring board, for example, , Switch circuits and LEDs
The external connection terminals of the drive circuit can be provided on the same substrate, and the effect of facilitating connection with the outside can be obtained.

Further, an opening (second opening) is formed in the area of the first printed wiring board which is aligned with the click spring mounting portion.
Is preferably provided. As a result, when the click spring is pressed, the second printed wiring board of the contact electrode circuit section is elastically deformed, and the action action originally intended for the click spring can be completed, resulting in a good click feeling. You will be able to get it.

[0021]

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

FIG. 1 is a sectional view showing an illumination switch unit according to the first embodiment of the present invention. In FIG. 1, the light guide diffusion resin plate, the silicone rubber foam, and the surface sheet laminated on the printed wiring board are the same as those in the related art, and therefore their illustration is omitted.

The printed wiring boards A and B each have an insulating layer 16a made of a polyimide film having a thickness of 25 μm.
16b is a single-sided plate having a predetermined pattern formed by depositing a rolled copper foil having a thickness of 18 μm as a metal wiring layer on one surface of 16b, which are bonded to each other with a laminating adhesive 19 interposed therebetween.

That is, on the metal wiring layer of the printed wiring board A, a contact electrode circuit 5 having a pair of contact electrodes, a signal circuit 17a for propagating an input signal, a connecting terminal 20a, etc. are selectively formed. .. A surface resist material 18a is selectively formed on the surface of the printed wiring board A except for the contact electrode circuit 5 and the connection terminals 20a. The contact electrode circuit 5 is plated with gold for contacts. Further, the printed wiring board A is provided with an opening 21 aligned with the LED element mounting portion.

The metal wiring layer of the printed wiring board B is LE
Power supply circuit 17b for supplying power to the D element, LED
The element mounting circuit 22, the connection terminal 20b, and the like are selectively formed. The LED bare chip element 7 is mounted on the LED element mounting circuit 22 of the printed wiring board B. A surface resist material 18b is selectively formed on the surface of the printed wiring board B except for the LED element mounting portion and the connection terminals 20b. The LED element mounting circuit 22 is plated with high-purity gold for wire bonding.

In both of these printed wiring boards A and B, the circuit forming surface is on the upper side, that is, the surface on the insulating layer side of the printed wiring board A and the circuit forming surface of the printed wiring board B are opposed to each other. They are joined by the laminating adhesive 19.
The laminated adhesive 19 is, for example, a sheet-shaped adhesive made of an epoxy resin having a thickness of 50 μm in which a region matching the LED element mounting portion is previously opened. The LED bare chip element 7 is, for example, a visible light element containing gallium / phosphorus as a main component, and its shape is a square having a side of 250 μm and a height of about 300 μm.

Resist material 18a near the LED element mounting portion
A silicon dam 12 is provided on the top. Inside the dam 12 (that is, inside the opening 21), a diffusing sealing resin such as transparent or milky white is injected to seal the LED bare chip element 7 and the bonding wire 8. Further, at a position on the printed wiring board A aligned with the contact electrode circuit 5, a dome-shaped click spring 6 made of metal is mounted with its edge placed on the surface resist material 18a.

In the illumination switch unit of this embodiment having the above-mentioned structure, the mounting surface (bottom surface) of the LED bare chip element 7 from the surface of the printed wiring board A to the printed wiring board A (thickness 43 μm) and the laminating adhesive agent. 19 (thickness 50μ
m) equivalent to the sum of the thicknesses (that is, about 100 μm)
Just below. Therefore, the resin sealing height can be reduced,
The total thickness of the switch unit equipped with upper laminated parts such as silicon rubber is about 10 compared to the conventional switch unit.
The thickness can be reduced to 0 μm.

Further, in this embodiment, since the contact area of the light diffusion resin 9 for sealing the LED bare chip element 7 and the like with the printed wiring board is enlarged, a strong adhesive strength can be realized and stress due to substrate deformation and the like can be realized. Resistance to.

Further, since the distance between the stamp position of the silicon dam and the electrode circuit for wire bonding becomes large, it is possible to prevent the circuit from being contaminated due to the diffusion of silicon. Therefore, a plurality of silicon dams can be simultaneously formed by printing before mounting the LED bare chip element, and the workability of the resin sealing step is improved. Furthermore, in contrast to the conventional use of a double-sided board as a printed wiring board, in the present embodiment, two single-sided boards are used in a laminated manner, so that costs such as raw material costs and board making process costs can be reduced. Since the gold plating specifications can be set individually for each layer, the plating cost can be reduced, and the manufacturing cost of the illuminated switch printed wiring board can be reduced.

FIG. 2 is a sectional view showing an illumination switch unit according to the second embodiment of the present invention.

This embodiment is different from the first embodiment in that a connection hole for electrically connecting the wiring circuit of the printed wiring board A and the wiring circuit of the printed wiring board B is provided. 2 is basically the same as that of the first embodiment, the same components as those in FIG. 1 are designated by the same reference numerals in FIG. 2 and their detailed description is omitted.

In this embodiment, the connection land pattern 32a is selectively formed on the wiring layer of the printed wiring board A, and the surface resist 18a is not formed on the land pattern 32a. At the center of the land pattern 32a, an opening 23 is formed at the same time when the opening 21 of the LED element mounting portion is formed.

On the other hand, on the wiring layer of the printed wiring board B, a land pattern 32b for connection is formed in alignment with the opening 23. Further, the surface resist material 18b and the laminating adhesive 19 are also provided with openings in alignment with the openings 23. The opening 23 is filled with, for example, a silver paste or a solder paste 24, and the land pattern 32a and the land pattern 32b are electrically connected.

In this embodiment, the same effect as that of the first embodiment can be obtained, and in addition, since the connecting terminals are collectively arranged on the printed wiring board B, the connection with the outside can be achieved. The effect of being easy can be obtained.

FIG. 3 is a sectional view showing an illumination switch unit according to the third embodiment of the present invention.

The present embodiment is different from the second embodiment in that the opening 25 is provided in the area of the laminated adhesive 19 and the printed wiring board B which are aligned with the arrangement position of the click spring 6, and the others. Since the construction of is basically the same as that of the second embodiment, in FIG. 3, the same parts as those in FIG. 2 are designated by the same reference numerals and the detailed description thereof will be omitted.

In this embodiment, the laminated adhesive 19 and the printed wiring board B, which are the back surface of the click spring arrangement portion of the printed wiring board A, are provided with the opening 25 having a diameter smaller than that of the click spring 6. For this reason, when the click spring 6 is pressed, the click spring 6 is deformed, the top portion thereof contacts the electrode circuit portion 5, and the insulating layer 16a of the printed wiring board A is deformed. Therefore, in this embodiment, in addition to obtaining the same effect as in the second embodiment, the original click action of the click spring 6 is possible, and a good click feeling can be obtained.

[0039]

As described above, the illumination switch unit according to the present invention is provided with the first printed wiring board on which the LED bare chip element is mounted and the opening provided in alignment with the LED element mounting portion. Since it is composed of the second printed wiring board joined to the printed wiring board, the total thickness of the unit can be reduced as compared with the conventional case. Also, since the distance from the silicon dam to the circuit pattern is large, it is possible to prevent circuit contamination due to silicon diffusion.
The workability of the process of sealing the ED bare chip element is improved. Furthermore, since the contact area between the sealing resin for sealing the LED bare chip element and the printed wiring board becomes large, the effect of preventing peeling of the sealing resin due to external stress is also obtained.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing an illumination switch unit according to a first embodiment of the present invention.

FIG. 2 is a sectional view showing an illumination switch unit according to a second embodiment of the present invention.

FIG. 3 is a sectional view showing an illumination switch unit according to a third embodiment of the present invention.

FIG. 4 is a sectional view showing a conventional illumination switch unit.

FIG. 5 is a schematic diagram showing a deformation behavior of a click spring.

FIG. 6 is a graph showing a load displacement curve of a click spring.

[Explanation of symbols]

 1; Printed wiring board 2, 16a, 16b; Insulating layer 3a, 3b; Conductive circuit 4a, 4b; Resist material 5; Electrode circuit part 6; Click spring 7; LED bare chip element 8; Wire 9; Light diffusion resin 10; Through Hole 12; Dam 13; Light guide diffusion resin plate 14; Rubber foam 15; Topsheet 20a, 20b; Connection terminals 21, 23, 25; Opening 22; Mounting circuit 24; Conductive paste 32a, 32b; Land pattern

Claims (3)

[Claims] 1. A first printed wiring board having a circuit pattern formed only on one surface side thereof, and an LED mounted at a predetermined position on the one surface of the first printed wiring board.
The bare chip element is provided with an opening in a region matching the bare chip element mounting portion of the LED and the first chip
A second printed wiring board having a circuit pattern formed only on the surface opposite to the one surface of the printed wiring board, and selectively arranged on the second printed wiring board. An illumination switch unit comprising a click spring provided. 2. A connection hole for electrically connecting a circuit pattern of the first printed wiring board and a circuit pattern of the second printed wiring board is selectively provided in the second printed wiring board. The illumination switch unit according to claim 1, wherein the illumination switch unit is provided. 3. The illumination switch unit according to claim 1, wherein a second opening is provided in a region of the first printed wiring board that is aligned with the click spring mounting portion. ..