JP2005347657A - Electronic device and electronic circuit arrangement using this electronic device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electronic device which reduces stress, caused by temperature change, to a terminal electrode, prevents a resonance, caused by external vibration, of a surface mounting device, and solves a problem such as a break of a relay substrate or the like, and also to provide an electronic circuit arrangement using this electronic device. <P>SOLUTION: A surface mounting device 1, in which a terminal electrode 4 is prepared in a bottom face, is mounted on a printed circuit board 20 having a mounting electrode 21 prepared at a location corresponding to the terminal electrode 4 via a relay substrate 10 enabling shear deformation in surface direction. A first relay electrode 11 connected in face to the terminal electrode 4 is formed on a front face of the relay substrate 10, and a second relay electrode 12 connected in face to a mounting electrode 21 is prepared at the same location with respect to the first relay electrode 11 on a rear face. When the printed circuit board is expanded in thermal expansion larger than the surface mounting device 1 by temperature rising, the relay substrate 10 is deformed in shear in the surface direction, and thereby, the stress applied to the terminal electrode 4 is reduced. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

The present invention relates to a structure of a surface mount type electronic device, particularly an electronic device used in an environment where thermal fluctuation and external vibration are large, such as an in-vehicle device.

Conventionally, surface mount electronic components have been widely used. In such an electronic component, a terminal electrode is provided on the bottom surface of a substrate constituting the electronic component, and the terminal electrode is connected to a mounting electrode of a printed circuit board by soldering or the like. When thermal fluctuation is applied in a state of being mounted on a printed circuit board, there is a problem that stress is applied to the terminal electrode if the difference between the linear expansion coefficient of the board on the electronic component side and the linear expansion coefficient of the printed circuit board is large.

As a countermeasure against this problem, Patent Document 1 proposes an electronic component having a structure in which a flexible substrate is disposed between a surface-mounted component and a printed board. The flexible substrate is larger than the electronic component, and the electrodes formed on the upper surface of the flexible substrate are soldered to the terminal electrodes of the surface mount component, and the end of the electrode extended to the side end of the flexible substrate is connected to the printed circuit board. Soldered to the mounting electrode.
In the electronic component having this structure, the portion directly under the terminal electrode of the surface mount component is not soldered to the printed circuit board, and the thin flexible substrate is bent to absorb the stress. In this case, since the surface-mounted component moves in the vertical direction due to the elasticity of the flexible substrate, it is likely to resonate with external vibration, and the flexible substrate may be broken. Further, since the flexible substrate is larger than the surface-mounted component, there is a drawback that the mounting area is increased.
An example in which an elastic sheet such as silicon rubber is laid on the bottom surface of the surface mount component in order to suppress the vertical vibration of the surface mount component is also disclosed, but this increases the number of components and increases the vertical dimension. There are drawbacks.
JP-A-7-201650

In Patent Documents 2 and 3, a flexible sheet is arranged between a semiconductor package having a terminal electrode on the bottom surface and a printed circuit board, and a relay electrode connected to the terminal electrode is provided on the upper surface of the flexible sheet. There is a disclosure in which a relay electrode connected to an electrode of a printed circuit board is provided on the lower surface of a flexible sheet. The relay electrode on the upper surface and the relay electrode on the lower surface of the flexible sheet are offset in the surface direction, and the stress applied to the terminal electrode is relieved by the bending of the flexible sheet.
In the case of the electronic circuit device having this structure, since the flexible sheet does not protrude from the semiconductor package, there is no disadvantage that the mounting area becomes large. However, since the relay electrode on the upper surface and the relay electrode on the lower surface are offset in the surface direction, the semiconductor package is likely to resonate when the vertical vibration is applied to the electronic circuit device, and the support stability of the semiconductor package is low. At the same time, bending stress concentrates in a region between the upper and lower relay electrodes in the flexible sheet, and problems such as breakage of the flexible sheet and breakage of the electrode are likely to occur.
JP-A-8-236898 JP 2002-237553 A

Therefore, an object of the present invention is to provide an electronic device that can reduce stress on the terminal electrode due to temperature change, prevent resonance of surface-mounted components due to external vibration, and solve problems such as breakage of a relay substrate, and the electronic device It is to provide an electronic circuit device using the above.

In order to achieve the above object, an invention according to claim 1 comprises a surface mount component having a terminal electrode provided on a bottom surface, and a relay substrate disposed on the bottom surface of the surface mount component and capable of shear displacement in a surface direction. A first relay electrode facing and electrically connected to the terminal electrode is provided on an upper surface of the relay substrate, and a second relay electrode is provided on a lower surface of the relay substrate and facing the first relay electrode. Provided that a connecting portion for connecting the first relay electrode and the second relay electrode to each other is provided at a position offset in the surface direction of the relay substrate with respect to the first relay electrode and the second relay electrode. An electronic device is provided.

In the present invention, a substrate capable of shear displacement in the plane direction is used as the relay substrate. Here, the shear displacement (shear strain) in the surface direction means that an upper surface and a lower surface parallel to each other cause relative displacement in the surface direction. The first relay electrode formed on the upper surface of the relay substrate and the second relay electrode formed on the lower surface are formed at positions vertically opposite to each other. The first relay electrode is face-to-face connected to the terminal electrode of the surface mount component, and the second relay electrode is face-to-face connected to an electrode such as a printed circuit board. When a vertical vibration is applied to the electronic device, the terminal electrode, the first and second relay electrodes, and the mounting electrode are in a position where they face each other, so the surface-mounted components do not resonate vertically and are held stably. it can. Also, if thermal fluctuations are applied to the electronic circuit device, there is a possibility that a large stress is applied to the terminal electrode due to the difference in coefficient of linear expansion between the substrate constituting the surface mount component and the mount substrate. This stress is relayed as in the past. It is not absorbed by the bending of the board, but is absorbed by the shear displacement in the surface direction of the relay board, that is, the sliding displacement in the surface direction. There is little risk to do.
In order to electrically connect the first relay electrode formed on the upper surface of the relay substrate and the second relay electrode formed on the lower surface, the first relay electrode and the second relay electrode are offset in the surface direction of the relay substrate. A connecting portion is provided at the position. In other words, since the connecting portion is formed at a portion away from the portion where the shear displacement in the surface direction of the relay substrate occurs, no shear displacement occurs at the connecting portion, and the connection between the first relay electrode and the second relay electrode is not caused. Without interfering with the shear displacement between them, the stress absorption effect is high.
As the relay substrate, a substrate capable of shear displacement in the plane direction is used, but any resin substrate having elasticity such as a flexible substrate can be used.

As in claim 2, the connecting portion is preferably a through hole provided in the relay substrate.
As a connection part for connecting the upper and lower relay electrodes to each other, it is possible to connect via the end of the relay board, but it is necessary to extend the electrode to the end, so the electrode length is unnecessary. There is a drawback of becoming longer. On the other hand, if the connection is made through the through hole, the upper and lower relay electrodes can be connected at an arbitrary position, which is desirable.

When the terminal electrode and the first relay electrode are electrically connected via solder as in the third aspect, the upper surface of the connecting portion is preferably covered with a solder resist.
Since the electrode thickness of the connection portion is reduced, if the solder adheres to the connection portion, the connection portion may be disconnected due to a solder erosion phenomenon. On the other hand, if the connection portion is covered with a solder resist, it is possible to prevent erosion of the solder due to the adhesion of solder and to solve the problem of disconnection.

As in claim 4, the relay board may have a size substantially equal to the bottom area of the surface mount component, and as in claim 5, the relay board is smaller than the bottom area of the surface mount component. The formed relay substrate may be individually provided for each of one or a plurality of terminal electrodes.
In the former case, since one relay board is sufficient for one surface mount component, connection is simple.
In the latter case, if there is a space between the terminal electrodes, there is an advantage that each relay board can be reduced in size.

As described above, according to the present invention, since the first and second relay electrodes are formed at the opposing positions of the upper and lower surfaces of the relay substrate, the first and second electrodes are directly below the terminal electrodes of the surface mount component. The relay electrode is fixed. Therefore, the relay board does not bend, the surface-mounted component is stably fixed, and the occurrence of resonance due to external vibration can be prevented.
In addition, when thermal fluctuations are applied to an electronic device, there is a possibility that a large stress is applied to the terminal electrode due to the difference in coefficient of linear expansion between the board constituting the surface mount component and the printed board. Since stress is reduced by shear deformation in the surface direction, stress on the terminal electrode can be reduced.
Furthermore, since the connecting portion for connecting the upper and lower relay electrodes to each other is provided at a position away from the relay electrode, the shear deformation of the relay substrate is not hindered, and the stress relaxation effect on the terminal electrode is high.

Embodiments of the present invention will be described below with reference to examples.

1 to 3 show an example of an electronic device A according to the present invention.
The electronic device A is composed of a surface mount component 1 and a relay substrate 10. The surface-mounted component 1 of this embodiment has a plurality of elements 3 mounted on a substrate 2 having an outer size of 5 × 3 mm, and four terminal electrodes 4 (see FIG. 2) at a corner portion of the bottom surface of the substrate 2. Reference) is formed. The substrate 2 is made of a material having a relatively small linear expansion coefficient, such as alumina. The terminal electrode 4 is formed of a thick film electrode, for example, and the size thereof is, for example, a quadrangle of 0.9 × 0.85 mm.

The relay substrate 10 of this embodiment is formed of a substrate that is the same size as the substrate 2 of the surface mount component 1 and that can be shear-strained in the surface direction with a thickness of 75 μm. Here, an aramid substrate flexible substrate is used. As shown in FIG. 3, four first relay electrodes 11 are formed on the upper surface of the relay substrate 10 at positions corresponding to the terminal electrodes 4 of the surface mount component 1, and the first relay is formed on the lower surface of the relay substrate 10. A second relay electrode 12 having the same shape as the electrode 11 is formed at a position vertically opposite to the first relay electrode 11. 3 shows only the upper surface of the relay substrate 10, the lower surface has the same shape. The relay electrodes 11 and 12 are made of Cu electrodes, for example, and are formed by a known printed wiring technique. As shown in FIGS. 4 and 5, the first relay electrode 11 is connected to the terminal electrode 4 of the surface mount component 1 by solder 30. A part of the first relay electrode 11 and the second relay electrode 12 is extended to a position offset in the surface direction of the relay substrate 10, and a connecting portion 13 made of a through hole is provided in the extended portion. The upper and lower relay electrodes 11 and 12 are electrically connected to each other by the connecting portion 13. The upper and lower surfaces of the connecting portion 13 are covered with a solder resist 14 so that solder does not adhere. Here, the two adjacent connecting portions 13 are covered with one solder resist 14, but each connecting portion 13 may be individually covered, and when the connecting portions 13 are close to each other, one connecting portion 13 is covered. All the connecting portions 13 may be covered with the solder resist 14.

On the printed circuit board 20 on which the electronic device A is mounted, mounting electrodes 21 are formed at positions corresponding to the terminal electrodes 4 of the surface mount component 1 as shown in FIGS. As is well known, the printed circuit board 20 is obtained by wiring a mounting electrode 21 on the surface of a resin substrate such as an epoxy resin or a phenol resin. Here, the mounting electrode 21 is composed of a Cu electrode. The second relay electrode 12 is connected to the mounting electrode 21 by the solder 31, and the electronic device A is mounted on the printed board 20. As described above, the first relay electrode 11 on the upper surface of the relay substrate 10 and the second relay electrode 12 on the lower surface are formed at positions vertically opposite to each other, and the first relay electrode 11 and the terminal electrode 4 of the surface mount component 1 are connected to each other. Since the second relay electrode 12 and the mounting electrode 21 of the printed circuit board 20 are face-to-face connected, the first and second relay electrodes 11 and 12 and the mounting are directly under the terminal electrode 4 of the surface-mounted component 1. Electrodes 21 are arranged and these are joined by solders 30 and 31, respectively.

Here, an electronic circuit device in which the electronic device A is mounted on the printed circuit board 20 will be described.
When this electronic circuit device is applied to a vehicle-mounted device, thermal fluctuation and vibration are applied. In general, the linear expansion coefficient of the printed circuit board 20 is larger than the linear expansion coefficient of the substrate 2 of the surface-mounted component 1, and the printed circuit board 20 expands more greatly due to the temperature rise, and stress is applied to the terminal electrodes 4 of the surface-mounted component 1.
This is shown in FIG. FIG. 6 shows the displacement of the relay board 10 in an enlarged manner for easy understanding of the principle.
When the printed circuit board 20 expands in the surface direction as indicated by an arrow, the mounting electrode 21 tends to spread outward with respect to the terminal electrode 4 of the surface mounting component 1, and a relative shift occurs between the electrodes 21 and 4. However, since this deviation is absorbed by the shear strain in the surface direction of the relay substrate 10, the stress applied to the terminal electrode 4 is relieved, and problems such as peeling of the terminal electrode 4 and peeling of the solder are solved.
Further, when external vibration is applied to the printed circuit board 20, the electronic device A mounted on the printed circuit board 20 may resonate and damage the surface mounted component 1. However, in the present invention, the first and second relay electrodes 11 and 12 and the mounting electrode 21 of the printed circuit board 20 are arranged immediately below the terminal electrode 4 of the surface mounting component 1, and these are fixed to each other by the solders 30 and 31. Therefore, the relay substrate 10 does not bend and deform, and the surface mount component 1 is stably fixed. Therefore, the phenomenon that the surface-mounted component 1 resonates due to external vibration can be prevented.
Furthermore, the solder 30 that connects the terminal electrode 4 and the first relay electrode 11 and the solder 31 that connects the second relay electrode 12 and the mounting electrode 21 do not adhere to the connection portion 13 due to the solder resist 14. The disconnection of the connecting portion 13 due to the solder erosion phenomenon can be reliably prevented.

Table 1 shows the thermal shock of −40 ° C. to 85 ° C. by soldering the electronic device A of the above example and the electronic device having no relay substrate to a printed board (material is glass epoxy) having a thickness of 1.6 mm. It is the result of having implemented the test and measuring the number of thermal cycles until the electronic device peels from the printed circuit board.
As is clear from Table 1, it can be seen that the electronic device A according to the present invention has twice the lifetime due to the relay substrate 10.

7 and 8 show a second embodiment of the electronic device according to the present invention.
In this embodiment, the relay substrate 10 is provided for each terminal electrode 4 individually. 7 and 8, the same parts as those of the first embodiment are denoted by the same reference numerals, and the duplicate description is omitted.
In this embodiment, the relay substrate 10 is divided into a plurality of pieces, and one first relay electrode 11 and one second relay electrode 12 are provided on the upper and lower surfaces of each relay substrate 10. Since the relay board 10 is divided into a plurality of parts, when thermal fluctuations are applied while mounted on the printed circuit board 20, no tension is generated between the relay boards 10, and the load on the relay board 10 is reduced. Tesumu. Further, since the relay substrate 10 is divided for each terminal, the relay substrate 10 can be mounted on the bottom surface of the surface-mounted component in the same manner as the component with a normal chip placer (component mounting device).

The present invention is not limited to the above embodiments, and can be modified without departing from the spirit of the present invention.
In the above-described embodiment, an example in which the relay substrate 10 is approximately the same size as the surface-mounted component 1 and an example in which each relay electrode 10 is divided for each terminal electrode are shown. For example, it may be formed every two terminal electrodes).
Further, as a method of manufacturing the electronic device according to the present invention, in addition to a method of individually connecting the relay substrate 10 to the surface mount component 1, the relay substrate 10 is manufactured in a mother substrate state, and a pattern is formed on the upper surface thereof. In addition, after mounting a plurality of surface mount components 1 on the first relay electrode, the relay substrate 10 can be divided and cut. In this case, the size of the relay substrate 10 may be slightly larger than the surface-mounted component 1 so that the cutting blade does not interfere with the surface-mounted component 1.
In the above embodiment, the terminal electrode and the first relay electrode, and the second relay electrode and the mounting electrode are connected by soldering, but another bonding material such as a conductive adhesive can be used. It is also possible to connect using bumps.

1 is a schematic perspective view of a first embodiment of an electronic device according to the present invention. It is the perspective view seen from the bottom face of the surface mounting components used with the electronic device shown in FIG. It is a perspective view of the relay board | substrate used with the electronic device shown in FIG. FIG. 2 is a front view and a partially enlarged cross-sectional view of a state where the electronic device shown in FIG. 1 is mounted on a printed board. FIG. 2 is a side view and a partially enlarged sectional view of the electronic device shown in FIG. 1 mounted on a printed board. It is a front view of the electronic circuit device at the time of temperature rise. It is a bottom view of 2nd Example of the electronic device concerning this invention. FIG. 8 is a front view and a partially enlarged sectional view of the electronic device shown in FIG. 7 mounted on a printed board.

Explanation of symbols

A Electronic device 1 Surface mount component 2 Substrate 3 Element 4 Terminal electrode 10 Relay substrate 11 First relay electrode 12 Second relay electrode 13 Connection part (through hole)
14 Solder resist 20 Mounting board (printed board)
21 Mounting electrodes

Claims (7)

Surface-mounted components with terminal electrodes on the bottom;
It is arranged on the bottom surface of the surface mount component and consists of a relay board capable of shear displacement in the surface direction,
A first relay electrode facing and electrically connected to the terminal electrode is provided on the upper surface of the relay substrate, and a second relay electrode is provided on the lower surface of the relay substrate and facing the first relay electrode. And a connecting portion for connecting the first relay electrode and the second relay electrode to each other at a position offset in the surface direction of the relay substrate with respect to the first relay electrode and the second relay electrode. And electronic devices. The electronic device according to claim 1, wherein the connection portion is a through hole provided in the relay substrate. The terminal electrode and the first relay electrode are electrically connected via solder,
The electronic device according to claim 1, wherein an upper surface of the connection portion is covered with a solder resist. 4. The electronic device according to claim 1, wherein the relay substrate has a size substantially equal to a bottom area of the surface mount component. The terminal electrodes are provided at a plurality of locations on the bottom surface of the surface mount component,
The relay board is formed smaller than the bottom area of the surface mount component,
4. The electronic device according to claim 1, wherein the relay substrate is individually provided for each of one or a plurality of terminal electrodes. The electronic device according to any one of claims 1 to 5, and a mounting substrate provided with a mounting electrode facing the second relay electrode on an upper surface,
An electronic circuit device, wherein the second relay electrode of the relay board and the mounting electrode of the mounting board are electrically connected. The mounting electrode and the second relay electrode are electrically connected via solder,
The electronic circuit device according to claim 6, wherein a lower surface of the connection portion is covered with a solder resist.

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