Container for electronic devices having a plurality of circuit boards

We claim:

1. A container for containing an electric device comprising:

a frame having a first opening and a second opening at two end surfaces thereof and opposing each other;

a metal bottom plate for closing said first opening;

a metal closure lid for closing said second opening;

whereby a closed space is formed by said frame, said metal bottom plate, and said metal closure lid and provided inside said container;

a first circuit means which is brought into contact with a surface of said metal bottom plate so that said metal bottom plate serves as a heat sink for said first circuit means;

a first electrode means provided to enable establishment of an electrical connection between said first circuit means and external portions of said container, said electrical connection being inside said closed space; and

a metal reinforcing plate provided inside said closed space and between said metal bottom plate and said metal closure lid, and bridging between at least two mutually opposing inner surfaces of said frame at a position formed between said first circuit means and said metal closure lid.

2. A container for containing an electric device according to claim 1, wherein said container is further provided with a second circuit means in contact with a surface of said metal reinforcing plate so as to be supported by said metal reinforcing plate.

3. A container for containing an electric device according to claim 1, wherein a substrate of said first circuit means comprises said metal bottom plate.

4. A container for containing an electric device according to claim 1, wherein said metal bottom plate, said metal closure lid, and said metal reinforcing plate are made of an identical metallic material.

5. A container for containing an electric device according to claim 2, wherein an amount of heat generated by said second circuit means is less than an amount of heat generated by said first circuit means.

6. A container for containing an electric device according to claim 2, wherein said second circuit means is disposed on a surface of said metal reinforcing plate, which opposes said metal closure lid.

7. A container for containing an electric device according to claim 6, wherein said first and second circuit means are coated by a gel form coating agent.

8. A container for containing an electric device according to claim 6, wherein a plurality of stepwise portions for supporting said metal bottom plate, metal closure lid, and metal reinforcing plate, are disposed on an inside surface of said frame.

9. A container for containing an electric device according to claim 8, wherein each one of said stepwise portions includes:

a horizontal plane portion to which a peripheral portion of any one of said metal bottom plate, said metal closure lid, and said metal reinforcing plate is bonded with an adhesive; and

a vertical portion for determining mutual positions of said metal bottom plate, said metal closure lid, and said metal reinforcing plate in their arrangement.

10. A container for containing an electric device according to claim 9, wherein a groove is formed on said horizontal plane portion of said stepwise portion at a side adjoining said vertical portion of said stepwise portion.

11. A container for containing an electric device according to claim 9, wherein a cut-out portion is formed at an inner boundary of said bonded region formed on said horizontal plane portion to thereby store said adhesive in said cut-out portion.

12. A container for containing an electric device according to claim 9, wherein said frame has an inner wall formed in a stepwise configuration with a stepped portion having a horizontal plane portion supporting a peripheral portion of said metal bottom plate, said metal closure lid, and said metal reinforcing plate, and

wherein said horizontal plane portion is formed with a groove thereon at an inner boundary at a side of a closed space of said frame.

13. A container for containing an electric device according to claim 7, wherein a plurality of stepwise portions for supporting said metal bottom plate, said metal closure lid, and said metal reinforcing plate, are disposed on an interior surface of said frame.

14. A container for containing an electric device according to claim 13, wherein each of said stepwise portions includes:

a horizontal plane portion to which a peripheral portion of any one of said metal bottom plate, said metal closure lid, and said metal reinforcing plate is bonded with an adhesive; and

a vertical portion for determining mutual positions of said metal bottom plate, said metal closure lid, and said metal reinforcing plate, in their arrangement.

15. A container for containing an electric device according to claim 14, wherein a groove is formed on said horizontal plane portion of said stepwise portion at a side adjoining said vertical portion of said stepwise portion.

16. A container for containing an electric device according to claim 14, wherein a cut-out portion is formed at an inner boundary of said bonded region formed on said horizontal plane portion to thereby store said adhesive in said cut-out portion.

17. A container for containing an electric device according to claim 14, wherein said frame includes an inner wall formed in a stepwise configuration with a stepped portion having a horizontal plane portion supporting peripheral portion of said metal bottom plate, said metal closure lid, and said metal reinforcing plate; and

wherein said horizontal plane is formed with a groove thereon at an inner boundary at a side of a closed space of said frame.

18. A container for containing an electric device according to claim 9, wherein said frame includes an inner wall formed into a stepwise configuration having horizontal planes in contact with a peripheral portion of a wired side of said circuit board and bonded with said circuit board by an adhesive; and

a dummy wiring with a wiring pattern formed inside of said inner boundary while maintaining a small clearance therebetween.

19. A container for containing an electric device according to claim 18, wherein a cut-out portion is formed at an inner boundary of said horizontal plane of said stepwise portion.

20. A container for containing an electric device according to claim 6, wherein a second electrode means is provided for said second circuit means and said first electrode means and said second electrode means are disposed on a first side surface of said frame.

21. A container for containing an electric device according to claim 20, wherein an electrical connection connecting said first and second circuit means is provided on a second side surface of said frame.

22. A container as according to claim 21, further comprising:

a first lead pin and a second lead pin, both supported by said frame and, respectively having a multi-pin structure, extending through one side of a side wall of said frame from the inside to the outside and in electrical contact with the contacting portions of said first circuit means and second circuit means at the interior of said frame; and

a connecting portion for integrally connecting said multi-lead structure connection leads and said first contacting portion and second contacting portion, and including intermediate connecting members held in stepwise bent fashion on the side wall of said frame at a side opposite to said side where said first and second lead pins are disposed, a first contacting portion disposed at a first stepped portion of said intermediate connecting member formed in a stepwise fashion and electrically connected to the contacting portion of said first circuit means and a second contacting portion disposed at a second stepped portion of said intermediate connecting member and electrically connected to the contacting portion of said circuit means.

23. A container as set forth in claim 21, further comprising:

an intermediate connecting member held inside the side wall of said frame in a stepwise bent fashion;

a first contacting portion exposed to a horizontal plane of the stepped portion of said side wall of said frame formed into a stepwise configuration and in contact with the contacting portion of the said first circuit board; and

a second contacting portion exposed to a horizontal plane portion of the stepped portion of the side wall of said frame formed into a stepwise configuration, other than that exposing said first contacting portion, and in contact with the contacting portion of said second circuit means.

24. A container according to claim 23, wherein said connection lead has a tip end extending from said second contacting portion toward an interior side of said side wall of said frame in parallel relationship with a connecting portion extending between said first contact portion and said second contact portion.

25. A container according to claim 21, wherein said container includes intermediate connecting lead members connecting said first circuit means and said second circuit means at one inner side wall of said frame, and having a stepwise configuration which comprises a first lead portion forming a first horizontal plate portion, a second lead portion forming a second horizontal plane portion, and a first vertical portion disposed between said first lead portion and said second lead portion and being perpendicular to both lead portions, wherein said first and second lead portions are disposed in opposite directions to each other with respect to said first vertical portion, and said first lead portion serves as a bonding region to which said first circuit means is bonded and said second lead portion serves as a bonding region to which said second circuit means is bonded.

26. A container according to claim 25, wherein said intermediate connecting lead member is further provided with a second vertical portion separate from said first vertical portion and extending downwardly from a free end portion of said second lead portion wherein said second vertical portion serves as an anchor portion to be inserted into and fixed to an inside portion of said frame.

Description Submit all comments and votes

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to an electronic device that can improve packaging density. More specifically, the invention relates to an electronic device that can improve the efficiency of an electrical connection between circuit boards and the effect of heat radiation, and prevent adverse effects from heat radiation, in a multi-board construction of the circuit boards. Furthermore, the invention relates to an electronic device and a lead and a terminal adapted to the electronic device for facilitating a connection of the boards and a lid member to a frame member.

2. Description of the Related Art

In the prior art, there are known electronic devices in which two or more circuit boards having installed semiconductor integrated circuits are packed in a single package. (For example, Japanese Unexamined Patent Publication (Kokai) No. 1-147850).

For such devices, various improvements have been made for facilitating the wiring between two or more circuit boards. Also, for external signalling, lead pins have been employed.

Conventionally, two or more circuit boards forming a multi-board structure have been bonded within the package.

In such a construction of the electronic device, the heat generated in the semiconductor circuits in the circuit board is transmitted to the package through the circuit board, or, as an alternative, is radiated within the internal space of the package. Accordingly, heat can be accumulated within the package that exhibits a low heat radiation effect.

On the other hand, since the conventional electronic device is designed to establish electrical connection between the circuit boards through the lead pins, which are used for externally feeding a signal, when signals are not commonly output externally, the lead pins have to be dummy pins, thereby resulting in a reduction in the number of active pins for externally outputting the signals.

Also, since the electrical wiring between a plurality of circuit boards is used in common to the lead pins, the number of connections to be established between the circuit boards is limited. In the case of the electronic device in which the packaging density of the elements is increased, the amount of wiring for connecting the circuit boards becomes large. Therefore, solving this problem is an important task.

In such an electronic device, bonding of the circuit board onto the package has been performed without adequate care. Therefore, an excessive amount of adhesive on the bonding surface may bulge to the surface of the circuit board, or may drop on the lower circuit board.

Such an excess amount of adhesive can serve to increase the floating electrostatic capacity or cause a dielectric breakdown, or can be a cause of a failure of electric connection by adhering to the bonding portion on the circuit board. Also, when the adhesive adheres to the connection lead for an electrical connection between the circuit boards, an abnormal transmission of the boding power can occur in the connecting process of the substrate and the connection lead by way of wire bonding to result in a bonding failure. Furthermore, it is possible that the heat radiation effect is lowered because of the adhesive, causing distortion, cracking, degradation of the characteristics owing to a difference in thermal expansion coefficients between the adhesive, the substrate and the connection leads and so forth.

On the other hand, it is typical to coat the upper portion of the circuit board installing the electronic circuit with a gel form coating agent for moisture-proofing. In such a case, a coating agent that is in the liquidous state at the initial condition, can bulge up along the side wall inside of the frame because of surface tension thereof to adhere on the horizontal surface of the installation guide for the upper circuit board and thus cause a failure of connection between the upper circuit board and the frame. Also, the gel form coating agent can contain foam and therefore degrade the moisture-proofing effect.

Furthermore, when the coating agent adheres on the connection lead for an electrical connection between the circuit boards, it can create cause an electrical connection failure similar to the adhesive agent.

SUMMARY OF THE INVENTION

In view of the above-mentioned drawbacks in the prior art, it is a first object of the present invention to provide an electronic device that can improve the heat radiation effect of the electronic device packaging a plurality of circuit boards in a multi-board structure.

A second object of the present invention is to provide an electronic device that can facilitate electrical connection between the circuit board in the electronic device installing a plurality of circuit boards in a multi-board structure.

A third object of the invention is to provide the electronic device that facilitates connection of the circuit boards of the electronic device installing a plurality of circuit boards in the multi-board structure in the package and prevent harmful effects from the adhesive used in the electronic device and prevent the occurrence of connection failure.

On the other hand, in the above-mentioned construction of the electronic device, in addition to the foregoing drawbacks, there have been many problems in the structure of a lead and a terminal. Namely, when the lead and the terminal of the electronic device are connected by way of electric welding, the region of the terminal to be welded is formed into a projection, causing a concentration of the current in the welding region. Alternatively, the tip end of the welding electrodes are formed into an acute angle.

However, in the above-mentioned method, when the projecting portion is placed in contact with the lead wire, the lead wire slips easily, thereby making it difficult to accurately position the lead wire relative to the projection on the terminal.

Therefore, a fourth object of the present invention is to provide lead and terminal structures that facilitate positioning of the lead relative to the terminal and easily produce a concentration of the current.

In order to accomplish the above-mentioned object, an electronic device, according to the present invention, fundamentally comprises:

a frame having two openings through major planes mutually opposed;

a plurality of circuit boards disposed in the frame parallel to the major plane, and mounting selected electronic circuits thereon respectively; and

first and second closure lids for closing the openings in the major plane; the first closure lid contacting the surface of at least one of the circuit boards, on which no electronic circuit is mounted.

More practically, the electronic device comprises:

a resin frame having an opening at both end surfaces;

a first metal plate closing one of the openings of the frame;

a first circuit board formed on the surface of the first metal plate facing inside of the frame;

a first electronic circuit mounted on the first circuit board and handling a relatively large current for generating a relatively large amount of heat;

a second circuit board arranged at the intermediate position in the frame above the first electronic circuit in parallel relationship to the first metal plane;

a second electronic circuit arranged on the second circuit board and handling less power than the first electronic circuit for generating a smaller amount of heat; and

a closure lid for closing the opening at the opposite side of the opening closed by the first metal plate.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will be more fully understood from the following detailed description and from the accompanying drawings of the preferred embodiment of the invention, which, however, should not be taken to present to the invention, but are for explanation and understanding only.

In the drawings:

FIG. 1 is a section of a practical embodiment of an electronic device according to the present invention;

FIG. 2 is a perspective view of a frame of the electronic device;

FIG. 3 is a perspective view of the frame, in which a first circuit board is mounted;

FIG. 4 is a perspective view of the frame, in which a second circuit board is mounted;

FIG. 5 is a section showing the construction of the frame;

FIG. 6 is a plan view showing the first circuit board;

FIG. 7 is a plan view showing a flat configuration before bending of lead pins;

FIG. 8 is a perspective view showing a three dimensional configuration after a bending process of the lead pins of FIG. 7;

FIG. 9 is a plan view showing another flat configuration before bending of the lead pin;

FIG. 10 is a perspective view showing a three dimensional configuration after being the lead pins of

FIG. 11 is a plan view showing a flat configuration before-bending the connection leads;

FIG. 12 is a perspective view showing a three dimensional configuration after bending the connection leads of FIG. 11;

FIG. 13 is a plan view showing another flat configuration before bending the connection leads;

FIG. 14 is a perspective view showing a three dimensional configuration after bending the connection leads of FIG. 13;

FIG. 15 is a plan view showing a further flat configuration before bending the connection lead;

FIG. 16 is a perspective view showing a three dimensional configuration after bending the connection leads FIG. 15;

FIG. 17 is a section showing a detailed construction of a first step portion;

FIGS. 18a and 18b are sections showing the another detailed contraction of the first step portion;

FIG. 19 is a section showing a detailed construction of a third step portion;

FIG. 20 is a plan view showing a construction of the third step portion mounting the second metal board;

FIG. 21 is a section showing a detailed construction of a fifth step portion;

FIG. 22 is a section showing a sectional structure of the lead;

FIG. 23 is a back elevation showing the basic side construction of the frame;

FIG. 22 is a section showing the relationship between a die associated with a production process of the frame and the connection lead;

FIG. 25 is a perspective view showing a manner for supporting the connection lead during fabrication of the frame;

FIG. 26 is a perspective exemplary illustration showing inappropriate support by an inappropriate configuration of a connection lead during fabrication of the frame;

FIG. 27 is a perspective view showing the relationship between another configuration of the connection leads and a manner of supporting therefor during fabrication of the frame;

FIG. 28 is a perspective view showing a connection between a terminal portion of the connection lead and a lead; and

FIG. 29a-29e are plan views showing another construction of the terminal portion of the connection lead.

DESCRIPTION OF THE PREFERRED EMBODIMENT

The preferred embodiment of an electronic device according to the present invention will be discussed herebelow in detail with reference to the accompanying drawings.

In FIG. 1, there is illustrated one example of the basic construction of the electronic device according to the present invention. FIG. 2 is a perspective view of a frame 10. FIG. 3 is a perspective view of the device, in which a lower first circuit board 50 is mounted on the frame 10. FIG. 4 is a perspective view of the device, in which an intermediate second circuit board 52 is mounted on the frame 10. FIG. 5 is a section of the frame 10.

As shown in FIG. 1, the preferred embodiment of the electronic device includes a frame assembly 1 that defines openings 11 and 12 on major surfaces 100 and 200, and a plurality of circuit boards 50 and 52. On the circuit boards 50 and 52, any appropriate electronic circuits, such as a semiconductor integrated circuit or so forth, are mounted. The circuit boards 50 and 52 are disposed in the frame in a piling fashion orienting their board surface parallel to the major surfaces 100 and 200 of the frame assembly 1. First and second closure lids 40 and 46 are provided for closing the openings 11 and 12 defined in respective major surfaces 100 and 200. At least one of the circuit boards 50 and 52 have a surface on which no electronic circuit is formed; the surface which is placed in contact with the first closure lid 40. In the shown embodiment, the circuit board 50 is provided with such a surface in contact with the first closure lid 40.

Preferably, the first closure lid, to which the circuit board 50 is connected by contacting the surface having no electronic circuit thereto, is formed from a metal plate. Another circuit board 52, which is placed away from the first closure lid 40, also has a surface on which no electronic circuit is formed. Such a circuit board surface 52 is preferably connected to an appropriate support plate 43. The support plate 43 is preferably formed from a metal plate.

In the preferred construction, the second closure lid 46 is formed of the same metallic material as that of the first closure lid 40.

In the shown construction, the first closure lid 40 serves to radiate heat generated in the electronic circuits on the circuit board 50.

The first aspect of the electronic device according to the present invention for achieving the first object of the invention will be discussed in detail with reference to FIG. 5.

As best shown in FIG. 5, a frame 10 is formed of a synthetic resin into a parallelepiped configuration. In the shown condition, the frame 10 defines an upper opening 12 opening to the external space at the upper side and a lower opening 11 opening to the external space at the lower side. On the inside surface of the frame 10, a first stepped portion 21, a second stepped portion 22, a third stepped portion 23, a fourth stepped portion 24 and a fifth stepped portion 25 are formed in order from the lower side. Respective stepped portions 21, 22, 23, 24 and 25 are defined by horizontal planes 21h, 22h, 23h, 24h and 25h having normals oriented in a Y axis direction (vertical axis direction) and vertical planes 21v, 22v, 23v, 24v and 25v having normals oriented in a X axis direction (horizontal axis direction). It should be noted that the vertical plane as used in the disclosure is not necessarily limited to the exactly vertical plane but can include a plane oblique to the vertical or horizontal plane.

As shown in FIG. 6, the first circuit board 50 is fabricated by forming an insulation layer on an aluminum plate 40 and forming a circuit pattern on the surface of the insulation layer. The circuit board integrally formed on the metal plate 40 is generally called a metal substrate. By bonding the peripheral portion 50a (FIG. 6) of the first circuit board 50 onto the horizontal plane 21h of the first stepped portion 21, the lower opening 11 is closed by the metal plate 40.

It should be noted that the height of the vertical plane 21v of the first stepped portion 21 is substantially equal to the thickness of the metal substrate on which the first circuit board 50 is integrally formed so that the bottom of the frame 10 and the back surface 41 of the metal plate 40 lie flush on a common plane.

On the first circuit board 50, a power supply circuit 51 (first electronic circuit) composed of power elements, such as power MOS transistor, power transistor and so forth, handling a large current and thus having a large amount heat generation is mounted, as shown in FIGS. 1 and 3.

As shown in FIG. 1 and 19, the metal plate 43 is arranged on the third stepped portion 23. Namely, on the horizontal plane 23h of the third stepped portion 23, the peripheral portion of the back side 44 of the metal plate 43 is bonded by an adhesive. The second circuit board 52 is bonded on the surface 45 of the metal plate 43 by the adhesive. On the second circuit board 52, a control circuit (second electronic circuit) handling a relatively small current and thus having a relatively small amount of heat generation is mounted. The power supply circuit 51 and control circuit 53 are coated by silicon gel 16, as shown in FIG. 1. The coating gel material to be employed for coating the circuits is not limited to silicon but can be any appropriate resin.

Since such a gel has an adiabatic effect, if the element handling a large current is mounted on the second circuit board in the foregoing construction, the heat generated by such an element may accumulate in a space defined between the first and second circuit boards 50 and 52 and cannot escape externally. In contrast to this, according to the shown construction of the present invention, the heat generated by the elements formed on the first circuit board 50 can be externally radiated through the metal plate 40 having a high heat radiation effect. In the shown construction, since the elements arranged on the second circuit board 52 will not generate a large amount of heat, no substantial heat will accumulate within the device.

On the fifth stepped portion 25 of the frame 10, a metal plate (closure lid member) 46 is provided for closing the upper opening 12. Namely, on the horizontal plane 25h of the fifth stepped portion 25, the peripheral portion of the back side 47 of the metal plate 46 is bonded by the adhesive. The surface of the metal plate 46 is exposed to the atmosphere. As set forth above, a casing of the electronic device 1 is formed by the frame 10 and the metal plates 40 and 46.

Since the shown embodiment of the electronic device is provided with the metal plate 40 made of aluminum for closing the lower opening 11 of the resin frame 10, the intermediate metal plate 43 formed of aluminum in the frame 10, on which the second circuit board 52 made of a ceramics is provided, deflection owing to difference of the thermal expansion coefficients between the resin frame 10 and the metal plate can be successfully prevented even at substantially high temperatures such as in the engine compartment of an automotive vehicle. Therefore, degradation of reliability because of cracking of the ceramic second circuit board 52 or a connection failure at a connecting portion on the second circuit board 52 can be successfully avoided. Also, since the metal plate 46 formed of aluminum is provided for the upper ending 12 of the frame 10, deflection of the frame and a connection failure of the circuit board associated with the deflection of the frame can be prevented with greater certainty.

It should be noted that the electronic device illustrated in FIG. 1 of Japanese Unexamined Patent Publication No. 1-147850 has a resin frame and a metallic closure lid member. The shown construction may cause deflection of the frame owing to a difference in the thermal expansion coefficient between the resin and the metal thereby causing cracking of the ceramic substrate disposed within the frame or degradation of reliability owing to a failure at the connecting portion.

In contrast to this, according to the shown embodiment, the first electronic circuit handling a relatively large current to generate a relatively large amount of heat is mounted on the lower metal plate board, and the second electronic circuit handling a relatively smaller current to generate a small amount of heat is mounted at the intermediate position. Also, the first