JP4107930B2 - Press-fit bonded wiring board and electronic equipment - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
  The present invention relates to a press-fit bonded wiring board to be incorporated in an electronic device, and more particularly to a press-fit terminal in a through-hole provided in a wiring board in an electronic control device mounted on a vehicle such as an automobile and used in a high temperature environment. This is a press-fit bonded wiring board that suppresses the influence of terminal press-fitting on the wiring board when it is press-fitted for electrical bonding.Furthermore, the present invention relates to an electronic device provided with the press-fit bonded wiring board.To do.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, in a vehicle such as an automobile, a plurality of electronic control devices called ECUs that control installed devices such as an engine are mounted as a unit for each function to be controlled. Each ECU includes a microcomputer that operates based on electronic information detected by each sensor, and includes a control circuit portion that performs logical control calculations, and external power such as an actuator that drives a control target according to the calculation results. A power circuit portion for performing control (see, for example, Patent Document 1).
[0003]
Therefore, FIG. 3 shows a schematic assembly configuration of an electronic control device conventionally used disclosed in Patent Document 1. The main part of the electronic control device 1 is housed in a connector-integrated resin case 2 in which a connector case is integrally formed. The control connector 3 and the power connectors 4 and 5 are gathered and provided on one of the side surfaces of the connector-integrated resin case 2. As a result, the electronic control device 1 can be electrically connected to the outside only from one direction.
[0004]
A control circuit portion and a power circuit portion are accommodated in the connector-integrated resin case 2. The power circuit portion includes a plurality of power electronic components 6 and 7 and the like, and connection terminals 8 and 9 are mounted on a module portion on which these power electronic components are mounted. The connection terminals 8 and 9 are used for electrical connection with the control board 10 included in the control circuit portion. Here, the control board 10 is mounted on the upper surface side of the connector-integrated resin case 2. A plurality of through-holes 11 and 12 are provided at the end of the substrate 10. The control circuit and the power circuit are connected by solder or the like so that the connection terminals 8 and 9 are inserted into the through-holes 11 and 12. Are electrically connected. A plurality of control electronic components 13, 14, 15 are mounted on the control board 10. Then, after mounting the control board 10 on the upper side of the connector-integrated resin case 2, the lid 16 is placed over the control board 10. On the other hand, on the bottom surface side of the connector-integrated resin case 2, a heat sink 17 is mounted for cooling the heat generated by the power electronic components 6 and 7 of the power circuit. Waterproof gaskets 18 and 19 are interposed at the joints between the lid 16 and the heat sink 17 and the connector-integrated resin case 2.
[0005]
As described above, in the on-vehicle electronic control device according to the related art, in the middle of the assembly of the electronic control device, the through-holes 11 and 12 provided in the control board 10 are erected on the module incorporating the power circuit. After the connection terminals 8 and 9 are inserted, the connection terminals 8 and 9 are soldered to conductive members formed in the through holes 11 and 12 by plating or the like. As a result, the connection terminals 8 and 9 are electrically connected to the wiring pattern formed on the control board 10 and the control board 10 is fixed in the connector-integrated resin case 2.
[0006]
In addition, in order to perform connection by soldering, it is necessary to perform not only soldering work but also cleaning work and the like, which not only increases the number of work steps but also deteriorates the work environment. Furthermore, there are many technical problems in soldering lead parts by lead-free soldering, and the number of man-hours for management increases.
[0007]
Here, in order to ensure the connection between the connection terminal and the control board, in the above-described conventional electronic control device, soldering is performed after the connection terminal is inserted into the through hole formed in the control board. However, when soldering to the through hole, the hole on the side opposite to the side where the connection terminal is inserted is blocked by solder, so check whether the through hole is in contact with the connection terminal. It is difficult to detect poor connections. Further, since the connection terminal and the control board are fixed, for example, the vibration of the housing to which the actuator is attached is directly transmitted to the control board, and the electronic components mounted on the control board are adversely affected.
[0008]
Therefore, it is necessary to connect the control board and the connection terminal securely, reduce the work man-hours, and realize the board connection that does not cause deterioration of the work environment. For example, a device that is applied to an electronic control device has been developed (see, for example, Patent Document 2). FIG. 4 shows how the control board and terminals are connected in this electronic control unit.
[0009]
FIG. 4A shows a longitudinal section in the through hole of the control board. This control board is the same as that used in the electronic control apparatus 1 shown in FIG. 3 and is the through holes 11 and 12 of the control board 10. In FIG. 4A, these through holes are represented by H.₁, H₂This is indicated by the symbol. Actually, more through holes are provided, but two are shown here representatively. Each through-hole is arranged at intervals p. And through hole H₁, H₂A conductive member 18 made of copper plating or the like is provided from the wall of the inner peripheral surface to the vicinity of the hole opening on the surface of the control board 10. The through-hole diameter was represented by w.
[0010]
  Meanwhile, figure4(B) shows a press-fit terminal P embedded and standing in a connection terminal housing.₁, P₂It is shown. These press-fit terminals are erected as many as the number of through holes provided in the control board 10.4(B)4Through hole H shown in (a)₁, H₂Corresponding to two press-fit terminals P₁, P₂Is shown and is erected at a position corresponding to the interval p of the through holes. Press-fit terminal P₁, P₂Is adjusted so that the control board 10 is fixed at a predetermined position in the case. The maximum width of the press-fit terminal before press-fitting is represented by W.
[0011]
The press-fit terminal is formed by punching a metal plate made of a conductive material such as a copper alloy to form one terminal. In the press-fit terminal, a main body portion, a pressure holding portion, an introduction portion, and a tip portion are integrally formed in the axial direction. The pressure holding portion and the introduction portion form a spring portion at the time of press-fitting. In the example of FIG. 4B, the main body portion is a base end portion that is embedded in the connection terminal housing and is erected. The introduction part is formed to be thin so that the tip end can be easily inserted when the press-fit terminal is press-fitted into the through hole.
[0012]
In the longitudinal direction of the axial center of the press-fit terminal, there is provided an opening that is formed simultaneously with the punching of the metal plate. By this opening, a pressure holding portion and an introduction portion are formed, and the width W of the position indicated by the AA line of the pressure holding portion is the widest among the terminals. The width of the introduction part gradually decreases toward the tip part.
[0013]
The cross-sectional areas of the pressure holding portion and the introduction portion in the press-fit terminal are the same size. When the press-fit terminal is press-fitted into the through hole, the press-fit terminal comes down from the top or the control board rises, so that a part of the introduction part first contacts the periphery of the through-hole opening. Thus, a load is applied and the introduction portion is elastically deformed. Further, when the load is continuously applied, the pressure holding portion is elastically deformed and press-fitted into the through hole. Here, the press-fit size for the through hole of the press-fit terminal is (W−w).
[0014]
Here, the through hole H of the control board 10 shown in FIG.₁, H₂The press-fit terminal P shown in FIG.₁, P₂FIG. 5 shows a state where the pressure is pressed. As shown in FIG. 5, the pressure holding part of the press-fit terminal is all press-fitted into the through hole, the control board 10 is held at a position close to the connection terminal module, and the control board 10 is fixed, Moreover, the pressure holding part is a through hole H₁, H₂The inner conductive material 18 is in close contact with and electrically connected.
[0015]
On the other hand, a control board mounted on the above-described electronic control device is required to have a low thermal expansion coefficient from the viewpoint of connection reliability. Conventionally, ceramic substrates, ceramic-resin composite substrates, fiber composite resin substrates, etc. have been developed to meet these requirements, but there are substrates that satisfy both a low coefficient of thermal expansion and good workability. Because there was not, using a metal foil-clad laminate integrated by heat-pressure molding of a prepreg layer obtained by impregnating and drying an epoxy resin on a sheet-like base material and a metal foil placed on the surface, as a substrate Yes.
[0016]
Then, the laminated substrate which reduced the elasticity modulus of resin and suppressed the thermal expansion of the surface direction of a laminated board by adding a flexible material to an epoxy resin is proposed (for example, refer patent document 3). . In the multilayer substrate proposed in Patent Document 3, fine particles having rubber elasticity are contained in the resin so that the metal foil is not peeled off due to the thermal expansion of the substrate even in an environment where the temperature fluctuates at a high temperature. It absorbs and relaxes the stress generated in the resin due to thermal expansion. Thereby, the thermal expansion in the planar direction of the multilayer substrate is suppressed to a small level.
[0017]
[Patent Document 1]
Japanese Patent Laid-Open No. 2000-323848 (FIG. 10)
[Patent Document 2]
Japanese Patent Laid-Open No. 10-208798
[Patent Document 3]
JP-A-8-309920
[0018]
[Problems to be solved by the invention]
By the way, when a press-fit terminal is press-fitted into a through-hole provided in the control board, fine damage due to stress concentration at the press-fit terminal press-fitting occurs in the through-hole entrance portion of the control board indicated by a circle in FIG. There is a case. Even in general electronic equipment, a press-fit terminal joining method is often used. In this case, the terminal tolerance is controlled by emphasizing the diameter tolerance of the through hole of the board. However, even in this case, since the terminal is press-fitted to obtain a holding force with the substrate, an unnecessary load is applied to the substrate.
[0019]
Usually, a substrate having a laminated structure in which a large number of sheets in which glass fibers are vertically and horizontally combined and impregnated with an epoxy resin is superposed and pressed and solidified is used as a control substrate. Therefore, it has a laminated structure in the periphery of the opening of the through hole provided on the board, and when press-fit terminals are press-fitted, a large force acts on the periphery of the opening in the direction of the board surface. Thus, damage due to substrate destruction such as peeling of the laminated sheets may occur. In order to firmly fix and hold the press-fit terminal, it is necessary to increase the elasticity of the press-fit terminal, for example, by using a large press-fit terminal. In this case, particularly, the occurrence of damage during press-fitting becomes significant.
[0020]
However, regarding the operating environment of the control board, for example, if the ambient temperature is not so high, or if temperature control is performed such as air-conditioning, it is assumed that damage during press fitting existed in the control board Is not a problem. On the other hand, particularly in the case of an electronic control device installed in an engine room such as an automobile, in a severe operating environment, for example, when the ambient temperature is high, the humidity is high, and the vibration is intense, Minor damage during press fitting may affect the substrate characteristics.
[0021]
The fact that the control board is damaged during press-fitting means that the insulation distance is shortened according to the length of peeling between the sheet layers. That is, when the control substrate is in a high temperature and high humidity environment, it becomes easy to absorb moisture at the damaged portion, and as a result, there is a problem that copper ions of the conductive material are melted and the insulation deterioration of the substrate is promoted. In particular, recently, electronic control devices are required to have a wide variety of control functions, so that the density of control boards has been increased and the size has been reduced, the number of electrical connections on the control boards has increased, and the distance between through holes has increased. Since it becomes small, there exists a big problem of promoting the insulation deterioration of a board | substrate.
[0022]
Further, it is necessary to further strengthen the holding force by the press-fit terminal for the control board of the electronic control device installed in the engine room where vibration is intense. Therefore, if the press-in force is increased in order to increase the holding force of the press-fit terminal, the result is an increase in the load during press-fitting. In order to reduce the load at the time of press-fitting, there is a problem that even if the generation of a load (load) can be suppressed by reducing the press-fitting silo, the holding force of the press-fit terminal is lowered.
[0023]
  Therefore, an object of the present invention is, for example, when a press-fit terminal is press-fitted into a through-hole provided in a wiring board in an electronic control device used in a high-temperature environment, and when the terminal is press-fitted. An object of the present invention is to provide a press-fit bonded wiring board that absorbs external stress and suppresses a burden generated in the board. Another object of the present invention is to provide a substrate structure in which a conventional press-fit terminal can be used as it is, and the substrate can absorb the stress applied to the substrate received from the terminal.Furthermore, another object of the present invention is to provide an electronic apparatus provided with the press-fit bonded wiring board.
[0024]
[Means for Solving the Problems]
  In order to solve the above problems, in the present invention, as a press-fit bonded wiring board,Using a substrate in which a plurality of fiber sheet base materials are bonded and laminated with a resin,Press-fit terminalsIn the thickness direction of the substrateIt has a through-hole that is press-fitted and holds an elastic material.In the surface layer portion of the substrateFilled in resinDecided.
[0025]
The elastic material is flexible particles, is dispersed in the resin of the substrate, and is selected from acrylic rubber, silicon rubber, nitrile butadiene rubber, or a combination thereof.
[0026]
  Also,SaidThrough hole inner surfaceIn, Metal harder than copperConductive member is formed byFor example, nickel, palladium and the like are included.
  Furthermore, in the electronic device of the present invention,A substrate in which a plurality of fiber sheet-like base materials are bonded and laminated with a resin, and a through hole provided in the thickness direction of the substrate, and an elastic material is filled in the resin in a surface layer portion of the substrate WasPress-fit bonded wiring boardPreparation, The press-fit terminal of the press-fit bonded wiring boardSaidThe press-fit bonded wiring board is fixed while being press-fitted and held in the through hole.
[0027]
DETAILED DESCRIPTION OF THE INVENTION
Next, an embodiment according to the press-fit bonded wiring board of the present invention will be described with reference to the drawings.
[0028]
Therefore, first, before explaining the press-fit bonded wiring board of the present embodiment, the concept that led to the improvement of this press-fit bonded wiring board is shown in FIG. FIG. 1A shows a conventional press-fit terminal P connected to a through hole H of the control board 10 shown in FIG.₁Or H₂It shows a state of being press-fitted into. In FIG. 1A, in order to simplify the drawing, the press-fit terminal P has a schematic shape, and the through hole H₁Or H₂The display of the conductive member 18 inside was omitted.
[0029]
FIG. 1A shows a state in which the press-fit terminal P is press-fitted into the through hole H. When the press-fit terminal P is inserted into the through hole H and the introduction portion contacts the opening peripheral edge of the through hole H, the insertion stroke is set to 0 mm. When a force is applied to the press-fit terminal P and the pressure holding portion starts to be press-fitted into the through hole H through the introduction portion, the insertion stroke is set to 0.6 mm. Although not shown in the figure, the press-fitting operation continues thereafter, and the insertion stroke becomes longer. A constant pressing force is applied to the terminal during the press-fitting operation.
[0030]
FIG. 1B shows a change in the load applied to the control board 10 when the press-fit terminal P is press-fitted into the through hole H as shown in FIG. The horizontal axis indicates the insertion stroke, and the vertical axis indicates the load (N). A load curve indicated by a solid line represents a change in load in the press-fitting operation of the press-fit terminal P shown in FIG. The load peaks when the insertion stroke is around 0.6 mm.
[0031]
In FIG. 1C, the stress curve shows the change in the stress generated at the peripheral edge of the opening of the through hole H of the substrate corresponding to this load curve. The horizontal axis is the insertion stroke, while the vertical axis is the generated stress (N / mm²). As can be seen from this stress curve, the magnitude of the generated stress becomes maximum when the insertion stroke is around 0.6 mm, and decreases as the press-fitting operation proceeds. Here, when compared with the design standard value of the conventional board, as shown in FIG. 1C, the maximum value when the insertion stroke is around 0.6 mm exceeds the board design standard value. For this reason, it is considered that excessive stress is generated in the opening peripheral portion of the through hole provided in the substrate, and the laminated structure of the peripheral portion is destroyed.
[0032]
Therefore, when the press-fit terminal P is press-fitted into the through hole H, the maximum value of the stress curve does not exceed the board design reference value in order to prevent damage to the peripheral edge of the through hole H. You can do it.
[0033]
Based on the above knowledge, in the press-fit connection wiring board of the present embodiment, when press-fit terminals are press-fitted into each of a plurality of through holes provided in the wiring board, external stress applied to the board can be reduced. In order to reduce this stress, the substrate itself of the laminated structure is given elasticity, and as a specific means, an elastic material is filled in the resin that binds the sheet-like substrate of the substrate. I did it.
[0034]
The press-fit connection wiring board according to the present embodiment will be described below. There are various methods for filling an elastic material into a resin, for example, an epoxy resin, that binds the sheet-like base material of the substrate.
[0035]
For example, when a prepreg layer obtained by impregnating and drying an epoxy resin varnish containing a curing agent on a sheet-like substrate and a metal foil placed on the surface of the prepreg are heat-pressed and integrated, Part or all of the layer is made to disperse fine particles having rubber elasticity that is incompatible with the epoxy resin, and an epoxy resin varnish is impregnated and dried on a sheet-like substrate to form a prepreg layer.
[0036]
Here, the dispersed fine particles have rubber elasticity that is incompatible with the epoxy resin in the varnish, and the particle material is one of acrylic rubber, silicon rubber, nitrile butadiene rubber, or these It is selected from those blended in combination.
[0037]
Next, when such fine particles are dispersed in the resin and applied to the press-fit bonding in the through hole for the wiring substrate in which the resin constituting the substrate is given elasticity, damage in the substrate during press-fit terminal press-fitting The occurrence situation is shown in FIG. In the graph of FIG. 2, the case of the press-fit connection wiring board in which elasticity is imparted to the resin according to the present embodiment is shown as an example. For comparison, a composite board (FR-4) using an epoxy resin conventionally used is shown. For example, the case of a glass woven resin substrate is shown as a conventional example.
[0038]
FIG. 2 shows the result of measuring the length of breakage such as peeling of the sheet-like base material as damage that occurs in the substrate when a press-fit terminal is press-fitted into the through-hole provided in the substrate. The fracture length was measured by applying a load in a direction parallel to the laminated surface of the sheet-like base material of the substrate to the substrate test piece on which stress was assumed to be applied. In the graph of FIG. 2, black circles indicate the measurement results in the conventional example, and black squares indicate the measurement results in the example. A thick solid line corresponds to the embodiment, and a thin solid line corresponds to the conventional example. These lines represent the tendency by plotting each measurement result.
[0039]
Therefore, when looking at the development trend of the fracture length for the conventional example, the fracture length increases as the stress applied to the substrate increases. On the other hand, in the case of the embodiment, it is added. It is shown that even if the stress increases, the degree of progress of the fracture length is suppressed. It is considered that the difference in the fracture occurrence results is due to the fact that the resin is filled with an elastic material. The result of the fracture length was the kind of fine particles to be filled, and was not so different from the example of FIG.
[0040]
In the substrate used in the conventional example, when performing press-fit bonding, only attention is given to the holding force with the substrate, and damage to the substrate when press-fitting the press-fit terminal into the through hole is not considered. . Therefore, when the terminal density is increased, the interval between the through holes is shortened, and the above-described progress of the breakdown length has been a great obstacle to improving the insulation reliability of the substrate. As a result, in order to use it in a high temperature environment, the through-hole interval must be designed wide in consideration of the fracture length, or the holding force of the press-fit terminal must be designed small.
[0041]
In contrast to this conventional example, in the case of a substrate in which an elastic material is filled in a resin, when a press-fit terminal is press-fitted into a through hole, as shown in FIG. 2, the stress generated on the substrate increases. However, since the progress of the fracture length can be kept low, a substrate that is resistant to the stress during press-fitting can be obtained. Therefore, even if the through-hole interval is shortened, the insulation reliability of the substrate can be guaranteed.
[0042]
For example, when the through-hole interval (inter-edge interval) is 300 μm, the fracture length limit is 150 μm. In FIG. 2, this range is shown as an allowable fracture length region that is shaded. In the substrate of the conventional example, for example, when the through hole interval is designed to be 300 μm and the required insulation reliability is to be obtained, the holding force of the press-fit terminal must be weakened to reduce the stress at the time of terminal press-fitting. . Usually, the stress generated when a terminal is press-fitted into a through hole is 400 to 500 N / mm.²Therefore, the substrate according to the conventional example cannot satisfy the requirement. In FIG. 2, the generated stress is f.₁As shown.
[0043]
On the other hand, in the case of the substrate according to the embodiment, since the substrate is filled with an elastic material in the resin, the external stress applied to the substrate is absorbed and relaxed, thereby increasing the strength of the substrate. The indicated stress f₂As described above, for example, even when a stress of 600 μm is applied, the fracture length can be suppressed to 150 μm or less, and the above-described requirements are sufficiently satisfied.
[0044]
In the description so far, the case where the elastic material is filled into the wiring board is exemplified as the case where the entire board is filled. However, the portion where the external stress applied to the board needs to be absorbed and relaxed is shown in FIG. As described above, in the press-fit terminal, paying attention to the vicinity of the press-fit entrance of the through hole formed in the substrate, the elastic material may be filled in the resin on the surface portion of the substrate.
[0045]
In addition, when the generated stress at the time of press-fitting the terminal into the through hole is large, in addition to filling the resin with an elastic material, the conductive material formed on the inner surface of the through hole is made of a metal harder than copper (for example, , Nickel, palladium, rhodium, etc.), and by partially bearing the stress when the terminals are press-fitted, the stress concentration can be dispersed and the stress resistance performance can be improved, improving the reliability of the board Can be made.
[0046]
In the above-described embodiment, the present invention is applied to a control circuit device such as an electronic control device mounted on an automobile or the like. However, the present invention is not limited to such use, and other circuit boards, for example, The same can be applied to the control circuit board of the labor-saving device, the control circuit board of the communication device, and the like, and the same effect can be obtained.
[0047]
【The invention's effect】
As described above, in the press-fit bonded wiring board of the present invention, since the elastic material is filled in the resin for bonding the sheet-like base material of the board, the shape of the press-fit terminal that is press-fitted into the through hole provided in the board Without changing the above, it is possible to secure the holding force in conventional press-fit bonding and improve the insulation reliability between through holes. For this reason, the press-fit bonded wiring board can be used particularly for a control board of an electronic control device in an environment of high temperature, high humidity, and severe vibration.
[0048]
Further, by filling the resin with an elastic material, it is possible to absorb and relax external stress applied to the substrate. Therefore, while using the conventional terminal, that is, without improving the conventional terminal, an effect can be obtained, and in order to manage the press-fitting white of the conventional board, the hole diameter tolerance of the printed wiring board is, for example, What is required in the range of 50 μm can be managed in the range of 150 μm to 200 μm, and the degree of freedom in designing the printed wiring board can be increased. In addition, the interval between the through holes can be shortened, and a high-density design of the control board is made possible.
[Brief description of the drawings]
FIG. 1 is a diagram illustrating a state of stress generated in a substrate when a press-fit terminal is press-fitted into a through hole.
FIG. 2 is a graph showing a comparison between an example and a conventional example regarding the relationship of the fracture length to the compressive stress.
FIG. 3 is an exploded perspective view for explaining a mounting state of electronic components in a conventional in-vehicle electronic control device.
FIG. 4 is a diagram illustrating a configuration in which a press-fit terminal is press-fitted into a through hole of a wiring board on which an electronic component is mounted.
FIG. 5 is a diagram illustrating a state in which a press-fit terminal is press-fitted into a through hole of a wiring board.
[Explanation of symbols]
1 ... Electronic control unit
2. Connector integrated resin case
3. Control connector
4, 5 ... Power connector
6, 7 ... Power electronic components
8, 9 ... Terminal for connection
10 ... Control board
11, 12 ... Through hole
13, 14, 15 ... control electronic components
16 ... Lid
17 ... Heatsink
18 ... Conductive member
H, H₁, H₂... through hole
P, P₁, P₂... Press-fit terminals

Claims (6)

A substrate in which a plurality of fiber sheet base materials are bonded and laminated with a resin;
Has a through-hole press-fit terminal is press-fitted held in the thickness direction of the substrate, and
An elastic material is filled in the resin in the surface layer portion of the substrate. Said elastic member is a flexible particles, the press-fit junction wiring board according to claim 1, characterized in that it is dispersed in the resin.   The press-fit bonded wiring board according to claim 2, wherein the flexible particles are acrylic rubber, silicon rubber, nitrile butadiene rubber, or a combination thereof. Inner to the peripheral surface, the press-fit junction wiring board according to any one of claims 1 to 3, characterized in that the conductive member according harder than copper metal is formed of the through hole. The press-fit bonding wiring according to any one of claims 1 to 4, wherein the substrate is a substrate on which glass fiber sheets impregnated with an epoxy resin are laminated, and printed wiring is provided on a surface of the substrate. substrate. A substrate in which a plurality of fiber sheet-like base materials are bonded and laminated with a resin, and a through hole provided in the thickness direction of the substrate, and an elastic material is filled in the resin in a surface layer portion of the substrate comprising a press-fit junction wiring board that is,
In a state where the press-fit terminal is press-fitted held in the through hole of the press-fit junction wiring board, electronic apparatus, characterized in that it is fixed to the press-fit junction wiring board.

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