JP2019186389A - Circuit-board - Google Patents

Abstract

To reduce distortion of solder due to difference in the coefficient of linear thermal expansion of a semiconductor element and a wiring board.SOLUTION: A circuit board 100 includes a wiring board 110, a semiconductor element 150 to be mounted on the wiring board 110, multiple conductive relay terminals 130 placed between the electrodes of the semiconductor element 150 and the wiring member 112 of the wiring board 110, a holding member 140 for holding the multiple relay terminals 130 in insulation state, a first solder 121 for electrically connecting the wiring member 112 of the wiring board 110 and the relay terminals 130, and a second solder 122 for electrically connecting the relay terminals 130 and the electrodes of the semiconductor element 150.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a circuit board on which an electronic component such as a semiconductor element is mounted on a wiring board.

  A control device (ECU) that controls a motor for electric power steering is equipped with a circuit board on which electronic components such as semiconductor elements are mounted on a wiring board. In recent years, the electrodes have a small area due to the miniaturization of the semiconductor element, and the electrodes provided directly on the semiconductor element are connected to the wiring board by solder without using a lead frame due to space saving of the control device.

  A control device attached to a vehicle is often exposed to a large temperature change, and due to a difference in linear expansion coefficient between the semiconductor element and the wiring board, the wiring board deforms more greatly than the semiconductor element with respect to the temperature change. In the case of a control device on which a small semiconductor element is mounted, since the electrode area is small, the solder is also thin, and the influence of the strain received by the solder connecting the wiring board and the semiconductor element is large. Therefore, the difference in expansion coefficient between the semiconductor element and the wiring board may cause cracks in the solder and increase the resistance, or may be in an insulating state due to destruction of the solder.

  As a technique for protecting the solder from such a difference in linear expansion coefficient, Patent Document 1 proposes a technique for arranging a spherical core inside the solder.

JP 2010-177394 A

  However, as in the technique described in Patent Document 1, it is very difficult to dispose a spherical core between each electrode of a semiconductor element and a wiring board, and it is even more difficult when the electrode is downsized. Will increase.

  In addition, increasing the solder thickness is expected to reduce the effects of strain due to differences in the linear expansion coefficient. However, when the electrode area is small or the electrode arrangement density is high, the solder thickness If the thickness is increased, there is a concern that when the solder is melted, the solder of the adjacent electrode comes into contact and short-circuits.

  The present invention has been made in view of the above problems, and even when there is a large difference in coefficient of linear expansion between a wiring board and a semiconductor element, a circuit capable of suppressing distortion applied to the solder connecting them. The purpose is to provide a substrate.

  In order to achieve the above object, a circuit board according to one aspect of the present invention includes a wiring board, a semiconductor element mounted on the wiring board, an electrode of the semiconductor element, and a wiring member of the wiring board. A plurality of relay terminals provided with conductivity, a holding member that holds the plurality of relay terminals in an insulated state, and a first solder that electrically connects the wiring member of the wiring board and the relay terminals; And a second solder for electrically connecting the relay terminal and the electrode of the semiconductor element.

  According to the present invention, the thickness of the solder connecting the wiring board and the semiconductor element can be substantially increased, and the distortion of the solder caused by the difference in linear expansion coefficient between the wiring board and the semiconductor element can be reduced. It becomes possible.

It is a perspective view which shows a part of circuit board. It is a cross-sectional perspective view which shows the cross section of the semiconductor element part of a circuit board. It is a disassembled perspective view which decomposes | disassembles and shows the semiconductor element part vicinity of a circuit board. It is a top view which shows a semiconductor element from the surface by the side of an electrode. It is a side view which shows the state which attached the heat sink to the semiconductor element of a circuit board. It is sectional drawing which shows the state of the expansion | extension of the semiconductor element, holding member, and wiring board by heating.

  Next, an embodiment of a circuit board according to the present invention will be described with reference to the drawings. It should be noted that each of the embodiments described below shows a comprehensive or specific example. The numerical values, shapes, materials, constituent elements, arrangement positions and connecting forms of the constituent elements, steps, order of steps, and the like shown in the following embodiments are merely examples, and are not intended to limit the present invention. In addition, among the constituent elements in the following embodiments, constituent elements that are not described in the independent claims indicating the highest concept are described as optional constituent elements.

  In addition, the drawings are schematic diagrams in which emphasis, omission, and ratio adjustment are appropriately performed to show the present invention, and may differ from actual shapes, positional relationships, and ratios.

  FIG. 1 is a perspective view showing a part of a circuit board. FIG. 2 is a cross-sectional perspective view showing a cross section of the semiconductor element portion of the circuit board. FIG. 3 is an exploded perspective view showing the vicinity of the semiconductor element portion of the circuit board in an exploded manner. As shown in these drawings, the circuit board 100 is a component of a control device that controls a motor included in the electric power steering, for example, a wiring board 110, a first solder 121, a second solder 122, The relay terminal 130, the holding member 140, and the semiconductor element 150 are provided.

  The wiring board 110 is a so-called printed board in which a pattern of a wiring member 112 made of a conductor is formed on the surface of an insulating board 111. The wiring member 112 is exposed at a portion of the wiring substrate 110 connected to an electronic component such as the semiconductor element 150, and the other portions are covered with a resist. Although the material of the board | substrate 111 will not be specifically limited if it has insulation, The thing etc. which impregnated the epoxy resin to the glass cloth etc. can be illustrated. The material of the wiring member 112 is not particularly limited as long as it has conductivity, and examples thereof include copper.

  The semiconductor element 150 is one of electronic components mounted on the wiring board 110. The type of the semiconductor element 150 is not particularly limited, but in the case of the present embodiment, the semiconductor element 150 is a MOSFET (metal-oxide-field field-effect transistor), and particularly performs switching of a large current. This is a so-called power MOSFET. As shown in FIG. 4, the semiconductor element 150 is a horizontal semiconductor element in which a gate electrode 151, a drain electrode 152, and a source electrode 153 are arranged in an array on one side. The semiconductor element 150 is a chip component that does not include a resin casing (package) or lead frame. By adopting a chip component as the semiconductor element 150, as shown in FIG. 5, a heat sink 159 is attached to the surface opposite to the surface on which the electrodes of the semiconductor element 150 are disposed via a heat dissipation sheet or the like. The heat of the element 150 itself can be efficiently radiated.

  The relay terminal 130 is a member that is disposed between an electrode such as the gate electrode 151, the drain electrode 152, and the source electrode 153 included in the semiconductor element 150 and the wiring member 112 of the wiring substrate 110. The material of the relay terminal 130 is not particularly limited as long as it has conductivity. For example, copper can be exemplified like the wiring member 112 of the wiring board 110. The shape of the relay terminal 130 is not particularly limited, but in the case of the present embodiment, the shape of the surface of the relay terminal 130 facing the electrode provided in the semiconductor element 150 is the same as the shape of the electrode provided in the semiconductor element 150. They have almost the same shape and the same size.

  The holding member 140 is a member that holds the plurality of relay terminals 130 in a predetermined arrangement state. The material of the holding member 140 is not particularly limited as long as it has an insulating property, but the linear expansion coefficient is between the linear expansion coefficient of the semiconductor element 150 and the linear expansion coefficient of the entire wiring board 110, particularly at the center. A value of about is preferred. Specifically, for example, the material of the holding member 140 can be exemplified by a resin adjusted using the epoxy resin as a matrix and the linear expansion coefficient.

  The shape of the holding member 140 is not particularly limited. In the case of the present embodiment, the holding member 140 corresponds to the shape of the disk-shaped semiconductor element 150 and has a disk-shaped holding portion 141 that holds the relay terminal 130. The leg portion 142, the support portion 143, and the positioning portion 144 are integrally provided.

  The method for holding the relay terminal 130 on the holding portion 141 is not particularly limited. For example, insert molding for arranging the relay terminal 130 at a predetermined position when the holding member 140 is formed, or on the holding portion 141 of the holding member 140. A method of press-fitting the relay terminal 130 into the provided through hole can be exemplified.

  The holding portion 141 is a portion that holds the plurality of relay terminals 130 at a predetermined interval, and holds the surface of the relay terminals 130 facing the wiring substrate 110 and the surface facing the semiconductor element 150 so as to be exposed. . The overall shape of the holding portion 141 is a disc shape corresponding to the shape of the semiconductor element 150.

  The leg portion 142 is a portion that maintains the relay terminal 130 at a predetermined interval with respect to the wiring board 110. In the case of the present embodiment, the leg portion 142 is disposed so as to protrude from the peripheral edge of the holding portion 141 toward the wiring board 110. Since the leg 142 determines the distance between the wiring substrate 110 and the relay terminal 130, the pressing load on the first solder 121 can be reduced or eliminated when the first solder 121 is melted. Therefore, the thickness of the first solder 121 after cooling can be made thicker than the case where there is no leg portion 142, and the first solder 121 has a size that can resist the distortion due to the difference in linear expansion coefficient. be able to.

  The support portion 143 is a portion that maintains the semiconductor element 150 at a predetermined interval with respect to the relay terminal 130. In the case of the present embodiment, the support portion 143 is disposed so as to protrude from the peripheral edge of the holding portion 141 toward the semiconductor element 150 and abuts on a portion where the electrode of the semiconductor element 150 is provided. Since the support portion 143 can maintain the distance between the relay terminal 130 and the semiconductor element 150 in the same manner as the leg portion 142, when the second solder 122 is melted, the pressing load applied to the second solder 122 is reduced. Can be reduced or eliminated. Therefore, it becomes possible to make the thickness of the second solder 122 after cooling thicker than the case where the support portion 143 is not provided, and to make the second solder 122 large enough to resist distortion due to the difference in linear expansion coefficient. be able to.

  The positioning unit 144 is a part that determines the positional relationship between the semiconductor element 150 and the relay terminal 130. In the case of the present embodiment, the positioning portion 144 is disposed so as to protrude from the peripheral edge of the holding portion 141 toward the semiconductor element 150 and contacts the side surface of the semiconductor element 150. The positioning unit 144 is a cylinder having a through hole in which the semiconductor element 150 matches the shape in plan view. By fitting the semiconductor element 150 into the through hole of the positioning unit 144, the rotation direction of the semiconductor element 150 is changed. The location to include can be determined.

  The first solder 121 is a member that electrically connects the wiring member 112 of the wiring substrate 110 and the relay terminal 130. The type of the first solder 121 is not particularly limited, but in the case of the present embodiment, since the semiconductor element 150 is surface-mounted on the wiring substrate 110, the first solder 121 is fluxed to the solder powder. A so-called cream solder made into a paste by adding is heated and melted in a reflow oven or the like, and cooled and solidified after melting.

  The second solder 122 is a member that electrically connects the relay terminal 130 and electrodes such as the gate electrode 151, the drain electrode 152, and the source electrode 153 of the semiconductor element 150. The type of the second solder 122 is not particularly limited and may not be the same as the first solder 121, but in the present embodiment, the same type as the first solder 121 is used.

  According to the circuit board 100 described in the above embodiment, the wiring board 110 and the semiconductor element 150 are electrically connected using the first solder 121 and the second solder 122. That is, through the relay terminal 130 held by the holding member 140, the wiring board 110 and the semiconductor element 150 are connected with a solder thickness approximately twice that of the case where the relay terminal 130 is not used. Therefore, from the state of the circuit board 100 shown in the part of FIG. 6A, as shown in the part of FIG. Even when the interval between the wiring members 112 is increased, the stress applied to the first solder 121 and the second solder 122 is suppressed, and the generation of strain is suppressed, so that an increase in resistance due to cracks, insulation due to breakage, etc. Can be suppressed.

  Furthermore, by adjusting the linear expansion coefficient of the holding member 140 so as to be closer to the semiconductor element 150 than the wiring substrate 110, the burden on the electrode of the semiconductor element 150 can be reduced, and peeling of the electrode can be reduced.

  The present invention is not limited to the above embodiment. For example, another embodiment realized by arbitrarily combining the components described in this specification and excluding some of the components may be used as an embodiment of the present invention. In addition, the present invention includes modifications obtained by making various modifications conceivable by those skilled in the art without departing from the gist of the present invention, that is, the meaning of the words described in the claims. It is.

  For example, the semiconductor element 150 has been described as having a disk shape in plan view, but the semiconductor element 150 may adopt any shape such as a rectangle. In addition, although the case where three electrodes of the gate electrode 151, the drain electrode 152, and the source electrode 153 exist in one semiconductor element 150, one semiconductor element 150 includes a functional unit such as a plurality of MOSFETs, Four or more electrodes may be provided on one surface. In this case, the same number of relay terminals 130 as the semiconductor elements 150 may be arranged at positions corresponding to the electrodes of the semiconductor elements 150 by the holding members 140.

  Further, the case where the holding member 140 supports one semiconductor element 150 has been described, but one holding member 140 may support a plurality of semiconductor elements 150. In this case, the holding member 140 holds the relay terminal 130 corresponding to the electrode provided in each of the plurality of semiconductor elements 150 to be supported.

  INDUSTRIAL APPLICABILITY The present invention can be applied to a circuit board used for control of a motor like an electric power steering, control of a motor for driving a vehicle, control of a motor for steering a vehicle, and the like. Further, the present invention is not limited to the motor control, and can be used for the circuit board 100 used in an environment where the temperature changes rapidly.

  100: circuit board, 110: wiring board, 111: board, 112: wiring member, 130: relay terminal, 140: holding member, 141: holding part, 142: leg part, 143: support part, 144: positioning part, 150: Semiconductor element, 151: Gate electrode, 152: Drain electrode, 153: Source electrode, 159: Heat sink

Claims (3)

A wiring board;
A semiconductor element mounted on the wiring board;
A plurality of relay terminals having conductivity disposed between the electrode of the semiconductor element and the wiring member of the wiring board;
A holding member that holds the plurality of relay terminals in an insulated state;
A first solder that electrically connects the wiring member of the wiring board and the relay terminal;
A circuit board provided with the 2nd solder which electrically connects the relay terminal and the electrode of the semiconductor element. The circuit board according to claim 1, wherein the holding member includes legs that maintain the relay terminals at a predetermined interval with respect to the wiring board. The circuit board according to claim 1, wherein the holding member includes a support portion that maintains the semiconductor element at a predetermined interval with respect to the relay terminal.

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