JP2014216480A - Wiring board and electronic equipment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a wiring board which enables a plurality of wiring conductors to be applied with varistor voltages different from each other, being effective for miniaturizing.SOLUTION: A wiring board includes an insulating substrate 1 equipped with a main surface containing a plurality of mounting parts 1a, input/output terminals 2, 3 provided on an outside surface of the insulating substrate 1, a plurality of input wiring conductors 4a provided from the input terminal 2 to the plurality of mounting parts 1a, a plurality of wiring conductors 4 containing a plurality of output wiring conductors 4b provided from the plurality of mounting parts 1a to the output terminal 3, a varistor circuit 5 in the insulating substrate 1, and a plurality of connection conductors 6 in which at least a part of the varistor circuit 5 is connected in series. The plurality of wiring conductors 4 are connected parallel to each other through the plurality of connection conductors 6. Lengths of the varistor circuits 5 connected respectively to the middle of the plurality of connection conductors 6 are different from each other for each of the plurality of connection conductors 6.

Description

  The present invention relates to a wiring board on which an electronic component such as a light emitting element is mounted, and an electronic device in which the electronic component is mounted on the wiring board.

  As a wiring board on which an electronic component including a light emitting element such as a light emitting diode element is mounted, a circuit board in which an electronic component mounting portion is provided on an upper surface of a flat plate or the like is often used.

  A wiring conductor is provided on the insulating substrate from the mounting portion to the input terminal and the output terminal provided on the outer surface such as the lower surface. An electronic component is mounted on the mounting portion, and the electronic component is electrically connected to the wiring conductor to form an electronic device.

  In addition, in order to reduce the possibility that an overvoltage such as a surge voltage is applied to an electronic component, a protective element such as a varistor element may be connected in parallel to the wiring conductor between the input terminal and the output terminal. is there.

  When a plurality of electronic components are mounted on a wiring board, a plurality of mounting portions and a plurality of wiring conductors corresponding to the mounting parts are provided on the insulating substrate.

JP 2012-227454 A JP 2008-270327 A

  When the withstand voltages such as breakdown voltages are different among a plurality of electronic components, for example, a plurality of protective elements corresponding to the respective breakdown voltages are mounted on the wiring board, so that a mounting space is required. Therefore, there is a problem that it is difficult to reduce the size of the wiring board and the electronic device.

  A wiring board according to one aspect of the present invention includes an insulating substrate having a main surface including a plurality of mounting portions on which electronic components are mounted, an input terminal and an output terminal provided on an outer surface of the insulating substrate, and the input A plurality of wiring conductors including a plurality of input wiring conductors provided from the terminals to the plurality of mounting portions; a plurality of output wiring conductors provided from the plurality of mounting portions to the output terminals; and the insulating substrate One varistor circuit provided in the inside, and a plurality of connection conductors in which at least a part of the varistor circuit is connected in series in the middle of the length direction, the plurality of wiring conductors and the plurality of wiring conductors Connection conductors are connected in parallel to each other, and the lengths of the varistor circuits connected respectively in the middle of the plurality of connection conductors are different from each other for each of the plurality of connection conductors.

According to the wiring board of one aspect of the present invention, the lengths of the varistor circuits connected in the middle of the length direction of the plurality of connecting conductors connecting the plurality of wiring conductors in parallel with each other are different from each other. Even if the breakdown voltages of the plurality of electronic components mounted on the plurality of mounting portions are different from each other, a breakdown voltage (varistor voltage) corresponding to the breakdown voltages can be applied. Further, since only one varistor circuit is required, it is possible to provide a wiring board effective for miniaturization.

(A) is a top view which shows the wiring board and electronic device of embodiment of this invention, (b) is sectional drawing in the AA of (a). It is sectional drawing which expands and shows typically the varistor circuit part in the wiring board shown in FIG. It is a schematic diagram for demonstrating the effect in the wiring board shown in FIG. (A) is a top view which shows the modification of the wiring board and electronic device which are shown in FIG. 1, (b) is sectional drawing in the AA of (a).

  A wiring board and an electronic device according to an embodiment of the present invention will be described with reference to the accompanying drawings. FIG. 1A is a plan view showing a wiring board and an electronic device according to an embodiment of the present invention, and FIG. 1B is a cross-sectional view taken along line AA of FIG. In the example shown in FIG. 1, the wiring board is used as an electronic component mounting board having an electronic component mounting portion.

  The wiring board of the present embodiment includes an insulating substrate 1 having a main surface including a plurality of mounting portions 1a on which electronic components are mounted, and an input terminal 2 and an output terminal 3 provided on the outer surface of the insulating substrate 1. It is out. A plurality of wiring conductors 4 are provided between the input terminal 2 and the output terminal 3 and the mounting portion 1a. The plurality of wiring conductors 4 include a plurality of input wiring conductors 4a and a plurality of output wiring conductors 4b. That is, each of the plurality of wiring conductors 4 includes an input wiring conductor 4a provided from the input terminal 2 to each mounting portion 1a and an output wiring conductor 4b provided from each mounting portion 1a to the output terminal 3. Contains. Electronic components 7 (a plurality of electronic components) are respectively mounted on the plurality of mounting portions 1a of the wiring board to form the electronic device according to the embodiment of the present invention.

  A single varistor circuit 5 is provided in the insulating substrate 1. In addition, a plurality of connection conductors 6 are provided from the input terminal 2 to the output terminal 3 inside the insulating substrate 1. In the middle of the connecting conductor 6 in the length direction, at least a part of the varistor circuit 5 is connected in series.

  Further, the lengths of the varistor circuits 5 connected in the middle of the length direction of the plurality of connection conductors 6 that connect the plurality of wiring conductors 4 in parallel to each other are different from each other. Therefore, even if the withstand voltages such as breakdown voltages of the plurality of electronic components 7 mounted on the plurality of mounting portions 1a are different from each other, a breakdown voltage (varistor voltage) corresponding to the breakdown voltage can be given. Further, since only one varistor circuit 5 is required, a wiring board effective for miniaturization can be provided.

  In the example shown in FIG. 1, a plurality (three) of wiring conductors 4 are provided corresponding to a plurality (three) of mounting portions 1a. Each of the three wiring conductors 4 includes an input wiring conductor 4a and an output wiring conductor 4b. That is, three input wiring conductors 4a and output wiring conductors 4b are provided. Three input terminals 2 and three output terminals 3 are provided corresponding to the three wiring conductors 4. This wiring board is used as an electronic component mounting board on which a plurality of electronic components 7 are mounted on a plurality of mounting portions 1a, for example.

  As the electronic component 7, for example, a light emitting element such as a light emitting diode or a semiconductor laser, a sensor element such as a semiconductor integrated circuit element (IC) or an acceleration sensor element, and a minute electromechanical mechanism are formed on the surface of a semiconductor substrate. Various electronic components such as a micromachine (so-called MEMS element) are exemplified.

  Hereinafter, each part which forms the wiring board is demonstrated concretely.

  The insulating substrate 1 functions as a base for mounting a plurality of electronic components 7. The insulating substrate 1 is formed of a ceramic sintered body such as an aluminum oxide sintered body, an aluminum nitride sintered body, a mullite sintered body, or a glass ceramic sintered body.

  If the insulating substrate 1 is made of, for example, an aluminum oxide sintered body, a plurality of ceramic green sheets obtained by forming raw powders such as aluminum oxide and silicon oxide into a sheet shape together with an appropriate organic binder and an organic solvent are laminated. It is manufactured by firing later. Each ceramic green sheet becomes an insulating layer (no symbol) in the insulating substrate 1.

  A plurality of mounting portions 1a are provided on the main surface of the insulating substrate 1 (upper surface in the example shown in FIG. 1). The mounting portion 1a is a portion on the upper surface of the insulating substrate 1 on which the electronic component 7 such as a light emitting element is mounted. For example, as shown in FIG. is there.

  The input terminal 2 and the output terminal 3 are parts for electrically connecting the wiring board to an external electric circuit (not shown). The input terminal 2 and the output terminal 3 have, for example, a quadrangular shape, a circular shape, an elliptical shape, or a combination thereof in plan view. By connecting the input terminal 2 and the output terminal 3 to an external electric circuit via a conductive connecting material (not shown), the wiring board and the external electric circuit are electrically connected to each other. Examples of the conductive connecting material include solder such as tin-silver solder, or a conductive adhesive.

  The input terminal 2 and the output terminal 3 are made of a metal material such as tungsten, molybdenum, copper, silver, palladium, gold, platinum, nickel and cobalt, or a metal material appropriately selected from these alloys. If the input terminal 2 and the output terminal 3 are made of, for example, tungsten, they can be formed by applying a metal paste of tungsten to a ceramic green sheet to be the insulating substrate 1 in a predetermined pattern and simultaneously firing.

  A plurality of input wiring conductors 4a are provided from the input terminal 2 to the plurality of mounting portions 1a. A plurality of output wiring conductors 4 b are provided from the plurality of mounting portions 1 a to the output terminal 3. One input wiring conductor 4a among the plurality of input wiring conductors 4a and one output wiring conductor 4b among the plurality of output wiring conductors 4b are paired to constitute one wiring conductor 4. In this case, it can be considered that one wiring conductor 4 is divided into two in the mounting portion 1a. The input wiring conductor 4a and the output wiring conductor 4b are electrically connected to each other via the electronic component 7 when the electronic component 7 is mounted on the mounting portion 1a. In other words, one conductive path from the input terminal 2 through the electronic component 7 to the output terminal 3 is formed by the wiring conductor 4.

  In addition, the part located in the mounting part 1a among the input wiring conductor 4a and the output wiring conductor 4b becomes a pattern, such as a square shape, and is wider than the other parts. Thereby, connection of the bonding wire 8 etc. with respect to the wiring conductor 4 becomes easy. Such end portions of the input and output wiring conductors 4a and 4b function as pads 4c to which the electronic component 7 is electrically connected via a conductive connecting material such as a bonding wire 8.

  Further, the wiring conductor 4 includes, for example, a circuit pattern-like portion (no symbol) extending along a plurality of insulating layers, and a through conductor (via conductor) (no symbol) penetrating the insulating layer in the thickness direction. Yes.

The wiring conductor 4 and the connection conductor 6 can be formed by the same method using the same material as the input terminal 2 and the output terminal 3, for example. Further, a portion of the wiring conductor 4 and the connecting conductor 6 exposed on the outer surface of the insulating substrate 1 and the input / output terminals 2 and 3 may be coated with a plating layer such as nickel and gold. Oxidation of the wiring conductor 4 and the connection conductor 6 is more effectively suppressed by the plating layer. In addition, characteristics such as the wettability of solder with respect to the wiring conductor 4 (particularly the pad 4 c) and the input / output terminals 2 and 3 and the bonding property of the bonding wire 8 are improved.

  For example, as shown in FIG. 2, the varistor circuit 5 opposes one varistor layer 5a made of a material having nonlinear resistance such as zinc oxide and at least a part of the varistor layer 5a. A plurality of pairs of varistor electrodes 5b. The connection conductor 6 is connected to the pair of varistor electrodes 5b facing each other, and the connection conductor 6 and the varistor circuit 5 are connected in series with each other. FIG. 2 is a cross-sectional view schematically showing an enlarged portion of the varistor circuit 5 in the wiring board shown in FIG. In FIG. 2, the same reference numerals are given to the same parts as in FIG.

  The plurality of pairs of varistor electrodes 5b are configured such that a plurality of other electrodes (for example, the input side) face each other with respect to one electrode (for example, the output side). The distance between each of the other electrodes and the one electrode (that is, the thickness of the varistor layer 5a interposed between the electrodes) T1 to T3 is different from each other. Varistor circuits 5 having different varistor voltages are formed according to the thicknesses T1 to T3 of the varistor layer 5a, and these varistor circuits 5 are connected in series to a plurality of connecting conductors 6. The plurality of other electrodes are arranged so as not to overlap each other in plan perspective.

  Each of these connection conductors 6 is connected in parallel to each of the plurality of wiring conductors 4. One connection conductor 6 is connected to one wiring conductor 4 at one input wiring conductor 4a and one output wiring conductor 4b. In other words, one connection conductor 6 is connected in parallel to one wiring conductor 4 at a position including the mounting portion 1a. The connection conductor 6 is connected to the wiring conductor 4 at both ends thereof, and at least a part of the varistor circuit 5 is connected in series in the middle of the connection conductor 6 in the length direction. That is, when the plurality of electronic components 7 are mounted on the plurality of mounting portions 1a, the plurality of electronic components 7 and the varistor circuit 5 are connected in parallel to each other.

  In this case, since the lengths of the varistor circuits 5 respectively connected in the middle of the plurality of connection conductors 6 are different from each other for each of the plurality of connection conductors 6, the varistor voltage is different for each connection conductor 6. Therefore, the length of the varistor circuit 5 in the connection conductor 6 connected in parallel with the wiring conductor 4 extending from the mounting portion 1a can be adjusted according to the breakdown voltage of the electronic component 7 mounted on the mounting portion 1a. . Thereby, the connection conductor 6 in which the varistor voltage is set according to the breakdown voltage of the electronic component 7 is connected in parallel with the wiring conductor 4, and the overvoltage is effectively suppressed from acting on the electronic component.

  In this case, since only one varistor circuit (one varistor layer 5 and electrode) is required as described above, it is easy to reduce the size of the wiring board. The varistor layer 5 is made of zinc oxide as described above. For example, a paste of zinc oxide is filled in a through portion (not indicated) provided in advance in a ceramic green sheet to be the insulating substrate 1 and is fired simultaneously. Can be formed. Further, by making the connection positions of the plurality of connection conductors 6 different in the thickness direction of the varistor layer 5 extending in the thickness direction of the insulating substrate 1, the lengths of the varistor circuits 5 connected to the connection conductor 6 are different from each other. Therefore, it is effective for reducing the size of the insulating substrate 1 in plan view.

The varistor electrode 5b can be formed by the same method using the same material as the connection conductor 6, for example. The varistor electrode 5b may be integrated with the connection conductor 6 (the end of the connection conductor 6 enters the varistor layer to form a varistor electrode).

  Note that the varistor layer 5a included in one varistor circuit 5 may be formed by stacking a plurality of sublayers 5aa. In this case, each sublayer 5aa corresponds to one insulating layer. That is, a plurality of sublayers 5aa provided on a plurality of insulating layers (ceramic green sheets) are laminated to form one varistor layer 5a. In the example shown in FIG. 2, one varistor layer 5a is formed by stacking three sublayers. Each sublayer 5aa is provided in each insulating layer, for example, and has a thickness that is an integral multiple of the thickness of the insulating layer.

  The varistor circuit 5 is not limited to a person including the varistor layer 5a made of zinc oxide and the varistor electrode 5b, and may take other forms. For example, the circuit which consists of material which has nonlinear resistance, such as strontium titanate or silicon carbide, is mentioned.

  If the electronic component 7 is a light emitting element such as a light emitting diode (LED), for example, the breakdown voltage of the electronic component 7 is different for each color to emit light. If a wiring board is used for a so-called full-color LED display device, three light emitting elements (electronic components 7) corresponding to three colors of RGB (red, green, blue) are mounted. Therefore, varistor voltages corresponding to at least three different breakdown voltages are required. On the other hand, in the wiring board, by adjusting the length of the varistor circuit 5 connected in series with the connection circuit 6, for example, the thickness of the varistor layer 5a between the pair of varistor electrodes 5b facing each other, Different varistor voltages can be connected to the electronic component 7 of each mounting portion 1a. Therefore, for example, it is not necessary to mount three varistor elements (not shown) having different varistor voltages on the wiring board, and it is easy to miniaturize the wiring board.

In the example shown in FIG. 2, RGB three light emitting diodes (LEDs) are mounted on the wiring board as the electronic component 7. In order of increasing breakdown voltage, there are a blue LED (about 3.5 V), a green LED (about 2.1 V), and a red LED (about 1.4 V). In this order, the length of the varistor circuit 5, that is, the thickness of the varistor layer 5a. It is getting smaller.

  A plurality of electronic components 7 such as light emitting elements are mounted on the wiring board, and after each electronic component 7 is electrically connected to the wiring conductor 4, the electronic component 7 is sealed as necessary. Electronic devices such as light emitting devices are manufactured. As for the electronic device, a current is supplied from an external electric circuit to the electronic component 7 from the input terminal 2 through the input wiring conductor 4a. With this current, an operation such as light emission is performed in the electronic component 7. The current that has dropped due to the operation returns from the output terminal 3 to the external electric circuit via the output wiring conductor 4b.

  In this case, for example, when a large overvoltage is applied to the wiring conductor 4 (between the input wiring conductor 4a and the output wiring conductor 4b) due to on / off of the switch or discharge of static electricity, the electrical resistance in the varistor circuit 5 suddenly increases. The voltage is applied to the varistor circuit side and a current flows. Thereby, it is suppressed that an overvoltage acts on the electronic component 7 electrically connected to the wiring conductor 4, and an electrical breakdown of the electronic component due to the overvoltage is suppressed.

With reference to the example shown in FIG. 3, one electronic component 7 and the wiring conductor 4 connected thereto will be described specifically. As shown in FIG. 3A, when an overvoltage is not acting between the input terminal 2 and the output terminal 3, the current flows from the input wiring conductor 4a to the electronic component 7 according to the wiring conductor 4, as shown by a solid line. And flows to the output terminal 3 through the output wiring conductor 4b. In this case, no current flows through the connection conductor 6 indicated by a broken line. On the other hand, as shown in FIG. 3B, when an overvoltage is applied between the input terminal 2 and the output terminal 3, the current flows from the input wiring conductor 4a to the connection conductor 6, as shown by the solid line. It flows to the output terminal 3 through the varistor circuit 5 and the output wiring conductor 4b. In this case, no current flows through part of the wiring conductor 4 (broken line portion) indicated by the broken line and the bonding wire 8, and no current flows through the electronic component 7. FIG. 3 is a schematic diagram (main part cross-sectional view) for explaining the effect of the wiring board shown in FIG. In FIG. 3, the same parts as those in FIG.

  If the electronic component 7 is a light emitting element, a plurality of electronic components mounted on the plurality of mounting portions 1a by a sealing material (not shown) such as a translucent resin material containing a fluorescent material, for example. 7 is sealed. Thereby, the electronic component is protected from the outside air, and light is emitted to the outside through the fluorescent material.

  FIG. 3 is a cross-sectional view showing a modification of the wiring board shown in FIG. In FIG. 3, the same parts as those in FIG. In the example shown in FIG. 3, a plurality of wiring conductors 4 (output wiring conductors 4 b) are collectively connected to one output terminal 3. Further, a part of the output wiring conductor 4b and a part of the connection conductor 6 are also used. This is effective for reducing the size of the wiring board. Moreover, it is easier to secure a space for routing the wiring conductor 4 in the insulating substrate 1.

  In addition, the some wiring conductor 4 (input connection conductor 4a) may be collectively connected to one input terminal (not shown). When a plurality of wiring conductors 4 are connected to one input / output terminal 2 or 3, the number of through conductors (via conductors) connected to the input / output terminals is increased in consideration of conduction resistance or the like, The sectional area in plan view is increased, or the size of the input / output terminal (3) itself in plan view is larger than the size in plan view of the input / output terminals 2 and 3 to which one wiring conductor 4 is connected. It is preferable to keep it large.

  The wiring conductor 4 may include other wiring conductors (not shown) in addition to the input wiring conductor 4 a and the output wiring conductor 5. Other wiring conductors include, for example, an internal conductor that electrically connects the plurality of mounting portions 2 to each other.

  The wiring board of the present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the gist of the present invention.

  For example, the varistor layer 5 a of the varistor circuit 5 does not have to be entirely located inside the insulating substrate 1, and at least one of the upper end portion and the lower end portion is exposed on the upper surface or the lower surface of the insulating substrate 1. I do not care. A part of the varistor electrode 5 b may be exposed on the main surface of the insulating substrate 1. When the varistor electrode 5b is exposed on the main surface of the insulating substrate 1, it is preferable that a plating layer such as nickel and gold is deposited on the exposed surface.

DESCRIPTION OF SYMBOLS 1 ... Insulation board | substrate 1a .... Mounting part 2 ... Input terminal 3 ... Output terminal 4 ... Wiring conductor 4a ... Input wiring conductor 4b ... Output wiring conductor 5 ... Varistor circuit 5a ... Varistor layer 5aa ... Sublayer 5b ... Varistor electrode 6 ... Connection conductor 7 ... Electronic component 8 ... Bonding wire

Claims (4)

An insulating substrate having a main surface including a plurality of mounting portions on which electronic components are mounted;
An input terminal and an output terminal provided on the outer surface of the insulating substrate;
A plurality of wiring conductors including a plurality of input wiring conductors provided from the input terminal to the plurality of mounting portions; and a plurality of output wiring conductors provided from the plurality of mounting portions to the output terminal;
One varistor circuit provided in the insulating substrate;
A plurality of connection conductors, wherein at least a part of the varistor circuit is connected in series in the middle of the length direction,
The plurality of connection conductors are connected in parallel to the plurality of wiring conductors,
A length of the varistor circuit connected in the middle of the plurality of connection conductors is different for each of the plurality of connection conductors. The varistor circuit includes one varistor layer made of a material having nonlinear resistance provided inside the insulating substrate, and a plurality of pairs of varistor electrodes facing each other with at least a part of the varistor layer interposed therebetween. And
2. The wiring board according to claim 1, wherein the varistor electrode and the connection conductor are directly connected. The electronic component is a light emitting element;
The wiring board according to claim 1, wherein the varistor circuit included in the middle of the connection conductor is longer as the breakdown voltage of the light emitting element is higher. The wiring board according to claim 1;
An electronic apparatus comprising: a plurality of electronic components mounted on the plurality of mounting portions.

Images