JP2007273669A - Electronic component mounting circuit board - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent a variation in the shape and thickness of a resin sealing layer and improve the adhesive strength of a part chip to a wiring board and the protection of the part chip from undesired external action. <P>SOLUTION: The electronic component mounting circuit board is provided with a circuit wiring board 1 having a plurality of circuit wiring layers S1, L1 and L2 formed on an insulating board 2, a facing panel 3 which is provided facing and away from the circuit wiring board, a plurality of electronic components 20 which are connected to the circuit wiring layer by means of conductive adhesive layers 21 and 22 and mounted between the wiring board 1 and mounted between the wiring board 1 and the facing panel 3, and a resin sealing layer 23 which is formed by covering the surface of the electronic part 20 and the conductive adhesive layers 21 and 22 and molding them by injection. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an electronic component mounting circuit board, and more particularly to an improvement of an electronic component mounting circuit board suitable for a function operation board of various electronic devices.

  In recent years, in the field of various electronic devices and the like, miniaturization, thickness reduction, and weight reduction are required, and a thin type equipped with a switch operation unit such as a function operation button, a numeric keypad or a keyboard and a display panel unit incorporated in these electronic devices. An electronic component mounting circuit board constituting a function operation board is widely used.

  As an example of the prior art of an electronic component mounting circuit board suitable for this type of function operation board, a membrane switch structure as shown in FIG. 5 of Patent Document 1 is known. That is, in Patent Document 1, a flexible membrane sheet is arranged so as to face each other on the wiring layer side of a circuit board having a circuit wiring layer on an insulating substrate, and a plurality of through holes for accommodating components It is shown that a spacer having a gap is interposed between the circuit board and the membrane sheet, and these are integrated to form a flat component case.

  In one through hole of the spacer, a surface mounting chip LED as an electronic component is attached to a land which is a part of the wiring layer, and in the other through hole, the opposing surface of the insulating substrate and the membrane sheet A pair of switch contacts is provided on the electronic component mounting circuit board, and various switch contacts and electronic components are mounted on the electronic component mounting circuit board.

  Further, Patent Document 2 shows a membrane switch structure similar to that of Patent Document 1, in which a large number of switch contacts and LEDs and other electronic components are mounted, and a switch operation unit is mounted on a surface sheet corresponding to the membrane sheet. An electronic component mounting circuit board having a numeric keypad and a numeric segment display of a display window is shown.

  Next, an example of mounting the electronic component (eg, LED device) generally performed on the electronic component mounting circuit board that has been conventionally performed will be described with reference to FIG.

  The lower circuit wiring board 40 in the figure is formed by providing a wiring layer having a pair of land portions 42 and 43 on the surface of an insulating substrate 41. On the upper side of the wiring substrate 40, a flexible membrane sheet 44 that is supported by being separated by an insulating spacer (not shown) is provided. The LED device 45 as a mounting component chip includes an insulating chip 45a provided with a pair of lead terminals 45b and 45c, an LED element 45d mounted on one lead terminal 45b, and the upper end of the element as the other lead terminal 45c. And a translucent resin envelope 45f on the light path side of the LED element 45d.

  Therefore, conductive adhesive layers 46 and 47 are applied to the pair of land portions 42 and 43, respectively, and the pair of lead terminals 45b and 45c of the LED device 45 are aligned on the adhesive layers 46 and 47, respectively. The conductive adhesive layer is cured, and the LED device 45 is electrically connected to the land portions 42 and 43 for mounting. The cured adhesive layers 46 and 47 and the pair of lead terminals 45 b and 45 c of the LED device 45 are covered and protected by a resin sealing layer 48 application and curing process.

  The application process of the resin sealing layer 48 is generally performed by applying a dispensing method using an applicator called a dispenser having a syringe 49 filled with a sealing resin material. That is, the sealing resin material poured out from the tip of the needle 49a of the syringe 49 is coated portions such as the bases of the adhesive layers 46, 47, the lead terminals 45b, 45c, and the translucent resin envelope 45f. It is applied in a dip over the surface.

  However, the resin sealing layer 48 applied in such a state that the sealing resin material is dipped in the application portion in this way, the resin flows and diffuses at the application or curing stage of the sealing resin material, and the resin sagging 48a, 48b. It is easy to become the shape which has. Due to the resin sagging, the thickness of the resin sealing layer 48 is partially or locally thinned on the conductive adhesive layers 46 and 47 and the lead terminals 45b and 45c, to the wiring board of the component chip. There are problems such as an increase in adhesive strength and insufficient protection from undesired external effects on component chips. The protection from the external action means protection against external stress (impact, etc.) on the component chip and passivation that is protection against external air intrusion into each conductive adhesive layer and each lead terminal.

  The occurrence of the resin sag increases the sealing area, and becomes a factor that hinders downsizing and high-density mounting of the electronic component mounting circuit board. In addition, variations in the application amount and application shape of the sealing resin material are likely to occur, and variations in mounting performance such as the adhesive strength are likely to occur as individual differences among the mounted components.

When the electronic component to be mounted is the LED device 45, the thickness of the resin sealing layer 48 on the surface of the translucent resin envelope 45f is uneven due to the application variation, The sealing resin material may be partially applied to the upper surface of the envelope 45f by mistake in the application operation, and individual differences regarding non-uniform luminance distribution and undesired light scattering between LED devices may occur. May occur.
Utility Model Application Publication No. 6-38266 Utility Model Registration No. 3048872 Registration Utility Model Gazette

  The present invention has been made in order to solve the above-described problems of the prior art, and variation in the shape and thickness of the resin sealing layer can be suppressed, and the adhesion strength of the component chip to the wiring board can be increased. An object of the present invention is to provide an electronic component-mounted circuit board with improved protection from undesired external effects on the chip.

  An electronic component mounting circuit board according to a first aspect of the present invention includes a circuit wiring board having a plurality of circuit wiring layers formed on an insulating substrate, and a facing panel provided on the circuit wiring board so as to be spaced apart from each other. A plurality of electronic components connected to the circuit wiring layer by a conductive adhesive layer and mounted between the wiring board and the facing panel, and a resin injection-molded to cover the surfaces of the electronic component and the conductive adhesive layer And a sealing layer.

  According to a second aspect of the present invention, in the electronic component mounted circuit board according to the first aspect, at least one of the plurality of electronic components is an optical element device having an optical path on the facing panel side, and the resin seal The stop layer is formed by injection molding of a translucent resin that covers the optical path side of the optical element device.

  According to the electronic component mounting circuit board of the present invention, a plurality of electronic components connected and mounted on the circuit wiring layer by a conductive adhesive layer and the surface of the conductive adhesive layer are resin-molded in a predetermined amount. The shape and thickness of the resin sealing layer are covered with an injection molding die. Therefore, variations in the shape and thickness of the injection-molded resin sealing layer are suppressed, and the adhesion strength of the component chip to the wiring board is enhanced and the protection against undesired external action on the component chip is reliably improved. The effect of doing.

  Further, when the electronic component is an optical element device, the resin sealing layer covering the light path side is formed by injection molding of a translucent resin, so that the shape and thickness thereof are the same as the injection mold. It can function as a light guide arranged in a uniform manner, and can transmit light with a uniform light distribution such as light quantity and luminance. Further, there is an effect that there is no individual difference in light distribution characteristics between the optical element devices.

  An embodiment of an electronic component mounting circuit board according to the present invention will be described below with reference to FIGS. 1 is a cross-sectional view showing an electronic component mounting circuit board according to an embodiment of the present invention, FIG. 2 is an enlarged cross-sectional view showing an LED device mounted on the mounting circuit board, and FIG. 3 is a sealing method of the LED device. It is an expanded sectional view for demonstrating. Further, the same components are denoted by the same reference numerals throughout FIGS. 1 to 3.

  First, the circuit wiring board 1 on the lower side of the electronic component mounting circuit board shown in FIG. 1 is for forming a circuit pattern on the surface of a flat insulating board 2 made of, for example, PET (polyethylene terephthalate). In addition, for example, a circuit wiring layer is formed by screen printing a silver paste. In the figure, the first contact layer S1 for switch cells and the first and second land layers L1 and L2 for electronic parts (details of these layers will be described later) which are a part of the circuit wiring layer are shown.

  The flat facing panel 3 facing the upper side of the circuit wiring board 1 is made of, for example, a flexible film made of PET or PEN (polyethylene naphthalate), and is spaced apart from the upper surface of the wiring board 1. Yes.

  The flat insulating spacer 4 made of, for example, PET or PEN interposed between the wiring board 1 and the facing panel 3 has a plurality of through holes such as the first through hole 5 and the second through hole 6. is doing. The wiring substrate 1 and the facing panel 3 are bonded and fixed to both surfaces of the spacer 4 with an adhesive material (not shown).

  A switch cell S is provided at the position of the first through-hole 5 of the spacer 4, and the switch cell S is a pair of surfaces formed on the opposing surfaces of the circuit wiring board 1 and the facing panel 3, respectively. It has 1st and 2nd contact layer S1, S2. The first contact layer S1 is formed as a part of the circuit wiring layer of the wiring substrate 1 and formed on the upper surface of the insulating substrate 2, and the second contact layer S2 is also connected to the circuit wiring layer in the same manner as the facing panel 3. It is formed on the lower surface (inner surface). The switch cell S performs an on / off operation between the contact layers S1 and S2 by pressing and releasing the flexible facing panel 3 at the position of the switch cell S. Each surface of the first and second contact layers S1, S2 is provided with a conductive carbon coating (not shown).

  The position corresponding to the second through-hole 6 of the spacer 4 is an electronic component chip mounting region M, and the first and second connected to the surface of the insulating substrate 2 of the circuit wiring board 1 as a part of the circuit wiring layer. Two land layers L1 and L2 are formed. An electronic component 20 such as an LED (light emitting diode) device is electrically connected to the first and second land layers L1 and L2, and is mounted on the circuit wiring board 1 in the second through hole 6. Has been.

  Practically, the electronic component mounting circuit board is provided with a number of land layers and mounting spaces such as the through holes in the circuit wiring board 1 so as to be a function operation board corresponding to the number of functions of the applied electronic device. Many switches and electronic components are mounted. As electronic components, device component chips such as passive elements (resistors, inductors, capacitors, etc.) and active elements (transistors, ICs, LEDs, etc.) are selectively combined as appropriate.

  The facing panel 3 is shown as having an embossed shape that protrudes outward (upward) in accordance with the outer height of the electronic component 20 in the mounting region M. When the distance between the contact layers of S can be increased, or when the height of the electronic component or its mounting height is low, it may be flat without providing embossing.

  The integrated structure of the circuit wiring board 1, the facing panel 3 and the spacer 4 has a so-called membrane configuration, and functions as a housing case for a large number of mounted switch contacts and LEDs and other electronic components. 3 can be provided with a function as a display panel capable of displaying numeric segments on the numeric keypad of the switch operation unit and the display window unit. The second through hole 6 may have a small diameter formed corresponding to each electronic component, or may have a large diameter that can accommodate a plurality of electronic components as one unit.

  Next, the electronic component 20 and its mounting structure will be described in detail with reference to FIG. Here, the electronic component 20 is an LED device as a mounted component chip. For example, an insulating chip 20a made of a ceramic plate, a metallized layer formed on both sides of the insulating chip (for example, after silver metallizing, gold plating is performed) A pair of lead terminals 20b and 20c, an LED element 20d mounted on a portion of one lead terminal 20b extending on the upper surface of the insulating chip 20a, and bonding for connecting the upper end of the element to the other lead terminal 20c. It has a translucent resin envelope 20f formed by applying a transparent epoxy resin mold to the light path side of the wire 20e and the LED element 20d.

  The pair of lead terminals 20b and 20c of the LED device 20 are disposed opposite to the first and second land layers L1 and L2 of the circuit wiring layer on the lower surface side of the insulating chip 20a. Are electrically connected and fixed by conductive adhesive layers 21 and 22 made of a conductive adhesive mixed with silver particles.

  The resin sealing layer 23 formed on the side of the translucent resin envelope 20f of the LED device 20 includes the LED device 20, the conductive adhesive layers 21 and 22, and the first and second land layers L1 and L2. For example, a light-transmitting sealing resin material made of, for example, an epoxy resin or a silicon resin is formed by injection molding so as to entirely wrap these components and each layer over the respective end portions.

  The resin sealing layer 23 enhances the adhesive strength of the lead terminal and the land layer by the conductive adhesive layer, and protects the mounting structure including the component chip from an unwanted external action, that is, the component chip. Protects against external stress on the surface, and protects each conductive adhesive layer and each lead terminal against passivation and the like against intrusion of outside air (such as moisture and contaminating components).

  In addition, the resin sealing layer 23 can function as an envelope that protects components such as the LED element 20d from external stress (pressing force or impact such as keystroke), so By making the envelope 20f thinner than before, it is possible to suppress an increase in the component mounting height due to the resin sealing layer 23 to a low level.

  In order to use the facing panel 3 as a display panel, a character display surface is formed on the embossed portion of the mounting region M, and the character display can be visually recognized by the irradiation light from the LED device 20. The resin sealing layer 23 can function as a light guide (or a light guide tube) that effectively guides light from the LED element 20d to the character display portion. Therefore, it is not necessary to prepare a light guide (or light guide tube) as an individual component other than the electronic component in the mounting process.

  Accordingly, the resin sealing layer 23 has a cross-section that is equivalent to the shape and area of the character display portion, and has a height such that the tip is close to or in contact with the inner surface of the display portion. It may be formed into a simple shape. In that case, the uniform distribution light of the brightness | luminance and light quantity corresponding to the optical characteristic of LED element 20d is irradiated to a display part, and a character can be displayed clearly.

  Furthermore, the resin sealing layer 23 can also have a function as an envelope for protecting components such as the LED element 20d from external stress (pressing force such as keystroke and impact). Accordingly, since the translucent resin envelope 20f can be made thinner than a conventional general thickness, an increase in the component mounting height due to the resin sealing layer 23 can be suppressed to a low level.

  Next, a method for manufacturing the electronic component mounted circuit board will be described with reference to FIGS. First, a circuit wiring board 1 is prepared in which a silver paste is screen-printed on the surface of the insulating substrate 2 to form a circuit wiring layer including the first contact layer S1, the first and second land layers L1, L2. Conductive adhesive layers 21 and 22 are formed by applying the conductive adhesive to the surfaces of the first and second land layers L1 and L2 by screen printing or dispensing. The lower surfaces of the lead terminals 20b and 20c of the LED device 20 are aligned and overlapped on the conductive adhesive layers 21 and 22, and the conductive adhesive layers 21 and 22 are thermally cured so that the lead terminals 20b, 20c is fixedly connected to each land layer L1, L2.

  Then, an injection mold 30 is prepared. The injection mold 30 has a cross-sectional shape, area, and height necessary for the resin sealing layer 23 to function as a light guide that effectively leads to the character display portion of the facing panel 3 as described above. The hollow wall surface 31 is designed in the shape of a column, and the insulating resin material introduction path 32 communicates from the hollow wall surface 31 into the cavity.

  Therefore, the injection mold 30 is placed on the circuit wiring board 1 so as to cover the conductive adhesive layers 21 and 22 on the first and second land layers L1 and L2 and the LED device 20 as a whole. The resin encapsulating layer 23 is formed by injecting and filling the pressure energized encapsulating resin material into the entire cavity through the introduction path 32 and thermally curing the resin. Therefore, the resin sealing layer 23 is made of a certain amount of sealing resin material corresponding to the cavity volume. In addition, although the front-end | tip injection port of the said introduction path 32 is distribute | arranged to the side position of the insulation chip | tip 20a of the said LED apparatus 20, the position may be selected suitably and formed.

  Thereafter, the spacer 3 and the facing panel 3 are overlapped on the circuit wiring board 1 and bonded together with an adhesive material to produce an electronic component mounting circuit board.

  According to the electronic component mounting circuit board according to the embodiment of the present invention, the resin sealing layer 23 has a structure according to the design size and shape of the injection mold, and the resin sagging as in the related art is prevented. Without being adjusted, it is adjusted to a predetermined shape and thickness. Therefore, there is no variation in the application amount and shape of the sealing resin material as in the prior art, and the above-described disadvantages for the mounting structure including the electronic component and the strengthening of the adhesive strength by the conductive adhesive layer between the lead terminal and the land layer are eliminated. There is an effect that the protection from a desired external action is surely improved. Such an effect can be obtained with almost no individual difference in the mounting of a large number of electronic components, and a product with even higher quality can be provided.

  Further, since the sealing area does not increase due to the resin sag as described above, the electronic component mounting circuit board can be miniaturized and high-density mounting can be improved. Furthermore, by changing the shape and cavity volume of the cavity wall surface 31 of the injection mold according to the outer shape and dimensions of the electronic component, the shape and dimension of the resin sealing layer for the mounted electronic component can be freely controlled or set. be able to.

  The circuit wiring board 1 may be formed using a so-called FPC (flexible wiring board) or RPC (rigid wiring board) in which a copper foil is laminated on an insulating substrate. As the optically mountable electronic components, a light emitting or receiving device including an organic EL as a light emitting element or a photodiode as a light receiving element can be used. Therefore, these optical devices are collectively referred to as an optical element device. To handle.

It is sectional drawing which shows the electronic component mounting circuit board which is one Embodiment of this invention. It is an expanded sectional view which shows the LED device mounted in the electronic component mounting circuit board which is one Embodiment of this invention. It is an expanded sectional view for demonstrating the sealing method of the LED apparatus mounted in the electronic component mounting circuit board which is one Embodiment of this invention. It is sectional drawing which shows the Example of the electronic component to the conventional electronic component mounting circuit board.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Circuit wiring board 2 Insulating board 3 Face-to-face panel 4 Insulating spacer 5, 6 Through-hole 20 Electronic component (LED device)
21, 22 Conductive adhesive layer 23 Resin sealing layer 30 Injection mold 31 Hollow wall surface L1, L2 Land layer of circuit wiring layer M Mounting area S Switch cell S1, S2 Contact layer

Claims (2)

  A circuit wiring board having a plurality of circuit wiring layers formed on an insulating substrate, a facing panel spaced apart from the circuit wiring board, and the wiring connected to the circuit wiring layer by a conductive adhesive layer Electronic component mounting comprising: a plurality of electronic components mounted between a substrate and a facing panel; and a resin sealing layer that is injection-molded to cover the surfaces of the electronic components and the conductive adhesive layer Circuit board. 2. The electronic component mounting circuit board according to claim 1, wherein at least one of the plurality of electronic components is an optical element device having an optical path on the facing panel side, and the resin sealing layer is a light of the optical element device. An electronic component mounting circuit board formed by injection molding of a translucent resin covering the passage side.

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