JP2023008681A - bonded substrate - Google Patents

Abstract

To obtain a bonded substrate capable of suppressing manufacturing cost and improving heat transfer performance.SOLUTION: A bonded substrate 10 includes a wiring board 20 having a through hole 21, and a metal plate 40 bonded to one surface of the wiring board 20 via an adhesive layer 30. The metal plate 40 has a concave portion 42 formed in a surface facing the through hole 21 of the wiring board 20, and when the metal plate 40 is bonded to one side surface of the wiring board 20, a part of the material of the adhesive layer 30 enters a recess 42 of the metal plate 40 such that the material of the adhesive layer 30 does not protrude to the other surface of the wiring board 20 through the through hole 21.SELECTED DRAWING: Figure 3

Description

The present disclosure relates to bonded substrates.

Patent Literature 1 discloses a bonded board in which a bonded circuit board for heat dissipation is bonded to a circuit board on which a plurality of mounted components are mounted. In this bonding board, the circuit board has a wiring pattern formed on the mounting surface and through holes penetrating through the circuit board. Parts are joined.

Japanese Patent Application Laid-Open No. 2003-243797

By the way, as in Patent Document 1, when a heat dissipation substrate is bonded to a circuit mounting substrate, an adhesive layer for bonding the substrates is formed between the stacked substrates. Such an adhesive layer can be composed of a thermosetting adhesive or a sheet-like adhesive sheet.

When the substrates are bonded together using a thermosetting adhesive, the laminated substrates and the adhesive are heated and pressed by a press to be integrally bonded. However, in order to prevent part of the adhesive from protruding from the through-hole to the surface of the substrate, processing such as filling the through-hole with a filler is required, which raises the problem of increased manufacturing costs.

On the other hand, a sheet-like adhesive sheet can be produced at a relatively low cost and can prevent the adhesive from entering the inside of the through-hole. However, since the thermal conductivity of the adhesive sheet is usually inferior to that of the adhesive, there is a problem that the heat transfer performance of transferring the heat generated by the mounted parts and the wiring pattern to the substrate for heat dissipation is lowered.

The present disclosure has been made to solve the above problems, and an object of the present disclosure is to obtain a bonded substrate capable of suppressing manufacturing costs and improving heat transfer performance.

A bonding substrate according to a first aspect of the present disclosure includes a wiring substrate having a through hole, and a metal plate bonded to one surface of the wiring substrate via an adhesive layer, the metal plate comprising: The wiring board has a concave portion formed in a surface facing the through hole, and in a state in which the metal plate is bonded to one side surface of the wiring board, a part of the material of the adhesive layer is the metal. By entering the recess of the plate, the material of the adhesive layer does not pass through the through hole and protrude to the other surface of the wiring board.

According to the bonded substrate according to the present disclosure, the bonded substrate includes the wiring substrate and the metal plate that are bonded via the adhesive layer, and the heat of the mounted components mounted on the wiring substrate is transferred to the metal plate to dissipate the heat. can do. The metal plate has a concave portion formed on a surface facing the through hole of the wiring substrate, and when the metal plate is bonded to one side surface of the wiring substrate, part of the material of the adhesive layer is the metal plate. It is configured to enter the concave portion of. Therefore, even if an adhesive with high thermal conductivity is used as the material of the adhesive layer, the material of the adhesive layer does not pass through the through holes and protrude to the other side of the wiring board. It is possible to reduce the manufacturing cost of the substrate and improve the heat transfer performance.

FIG. 2 is a plan side perspective view showing a state in which mounted components are mounted on the bonding substrate according to the first embodiment; 3 is a perspective view of a metal plate that constitutes the joint substrate according to the first embodiment; FIG. 4 is a partial cross-sectional view of the bonded substrate in the first embodiment; FIG. It is a partial top view which shows the modification of the metal plate which concerns on 1st Embodiment. FIG. 4 is a partial cross-sectional view corresponding to FIG. 3, showing the bonded substrate according to the second embodiment. It is a partial top view which shows the modification of the metal plate which concerns on 2nd Embodiment. FIG. 4 is a partial cross-sectional view corresponding to FIG. 3, showing a bonded substrate according to a third embodiment;

A first embodiment of the present invention will be described below with reference to FIGS. 1 to 3. FIG. In the present embodiment, for convenience of explanation, the directions indicated by arrows in the up/down, left/right, and front/rear directions shown in the drawings are defined as the up/down direction, left/right direction, and front/rear direction of the bonding substrate 10, respectively.

As shown in FIG. 1, the junction substrate 10 includes a wiring substrate 20 having conductive wiring on the surface and inside of an insulating substrate, and an adhesive layer 30 on the lower surface (one side surface) of the wiring substrate 20. It has a joined metal plate 40 .

The wiring board 20 is a rectangular plate-shaped printed wiring board having predetermined widths in the front-rear direction and the left-right direction and having the thickness direction in the vertical direction. The upper surface (the surface on the other side) of the wiring board 20 serves as a mounting area for mounting a plurality of mounted components. Specifically, a wiring pattern 22 (conductor layer) formed of copper foil is bonded to the upper surface of the wiring board 20, and various circuits are configured by mounting a plurality of mounting components on the wiring pattern 22. Four semiconductor elements 24 , one capacitor 26 , and four electrode terminals 28 are mounted on the wiring board 20 as an example of a plurality of mounted components. The four semiconductor elements 24 can constitute rectifying elements of a rectifying circuit, switching elements of an inverter circuit, etc. under the control of a control unit (not shown) having a CPU. In this embodiment, the plurality of mounted components described above are mounted on the upper surface of the wiring board 20 using solder printing bonding.

As shown in FIG. 3, the wiring board 20 has a plurality of through holes 21 penetrating through the wiring board 20 in the thickness direction. Among these through-holes 21, those having conductor portions 21A filmed (plated) on the inner peripheral surface serve as through-holes for conducting between layers of the wiring substrate 20 and for electrically connecting terminals of mounted components. Configure. Moreover, those having no conductor portion 21A on the inner peripheral surface constitute non-through holes for fixing parts.

As shown in FIG. 2, the metal plate 40 has a predetermined width in the front-rear direction and the left-right direction, and is formed in a rectangular plate shape with the thickness direction extending in the vertical direction. The metal plate 40 is made of aluminum, copper, or a highly heat-dissipating metal material containing these as main components. Configure.

In this embodiment, a sheet-like adhesive that forms the adhesive layer 30 and the wiring substrate 20 are laminated on the metal plate 40, and these are heated and pressed inside the mold of a press machine to form the bonded substrate 10. (joining process). The sheet-like adhesive is, for example, a thermosetting adhesive containing epoxy resin as a main component, and functions as an adhesive by being melted by heating. In addition, these materials are also insulating materials, and form an insulating layer that secures insulation between the wiring board 20 and the metal plate 40 after curing. In the bonding process, a pressure load is applied to the adhesive layer 30 in a melted state by a pressing machine, so that part of the material of the adhesive layer 30 is extruded and flows into the through hole 21 on the wiring substrate 20 side. At this time, if the amount of the adhesive flowing into the through hole 21 is large, the adhesive protrudes through the through hole 21 to the upper surface side of the wiring board 20 , and the hardened adhesive forms a convex portion on the upper surface of the wiring board 20 . formed.

After that, a resist film is attached to the upper surface of the wiring substrate 20, heated, and pressed to form a resist on the upper surface of the bonding substrate 10. Then, a component (semiconductor element 24) is attached to the wiring pattern 22 on the upper surface by solder printing. , capacitor 26, electrode terminal 28, etc.) are joined. If a convex portion is formed on the upper surface of the wiring board 20 in the bonding process described above, there is a problem that the resist film cannot be pasted in the resist forming process. This resist forming process can be performed by applying a liquid resist solution to the upper surface of the wiring board 20 instead of using a resist film. Since it becomes difficult to place the substrate 20 in close contact with the upper surface of the substrate 20, there arises a problem that the solder printing process cannot be performed. Even if the amount of adhesive protruding from the upper surface of the wiring board 20 is small, the adhesive mixed into the solder as an impurity can reduce the mechanical bonding strength of the solder and reduce the power loss during energization. It may affect the size.

Therefore, in the metal plate 40 of this embodiment, as shown in FIG. Each of the plurality of recesses 42 is formed of a through hole penetrating through the metal plate 40 in the plate thickness direction, and is arranged at a position corresponding to the through hole 21 on the wiring board 20 side in a state of being joined to the wiring board 20 . ing. Therefore, in the bonding process, part of the melted material of the adhesive layer 30 also flows into the concave portion 42 of the metal plate 40 in a dispersed manner, passes through the through hole 21 on the side of the wiring board 20 , and protrudes onto the upper surface of the wiring board 20 . configured to prevent

Further, since the recess 42 penetrates the metal plate 40 in the plate thickness direction, the air pushed out by the adhesive is discharged without remaining inside the recess 42 . As a result, no air bubbles are generated inside the concave portion 42, so that the melted adhesive naturally flows into the concave portion 42 due to its own weight. Further, in this embodiment, by setting the opening area of the recess 42 to be larger than that of the through hole 21 on the wiring substrate 20 side, the flow resistance in the recess 42 is reduced, and the flowing adhesive is actively pushed into the recess 42 . is guided to

(Action and effect)
As described above, in the bonding substrate 10 according to the present embodiment, the wiring substrate 20 and the metal plate 40 are bonded via the adhesive layer 30, and the heat of the components mounted on the wiring substrate 20 is dissipated. , is transmitted to the metal plate 40 and radiated to the outside through the metal plate 40 .

As shown in FIG. 3 , the metal plate 40 has recesses 42 formed in the surface facing the through holes 21 of the wiring board 20 , and when the metal plate 40 is bonded to the wiring board 20 , the adhesive layer A part of the material of 30 is configured to enter the concave portion 42 of the metal plate 40 . Therefore, it is possible to prevent the material of the adhesive layer 30 from protruding from the upper surface of the wiring board 20 through the through hole 21, so that the bonded substrate can be formed in a single bonding process using a heat press. Substrate manufacturing costs can be suppressed. In addition, as the material of the adhesive layer 30, an adhesive having higher thermal conductivity than a sheet-like adhesive sheet can be used, so that the heat transfer performance of the adhesive layer 30 can be improved.

Further, in this embodiment, the opening area of the recess 42 of the metal plate 40 is set larger than the through hole 21 of the wiring board 20 . As a result, the flow resistance of the material of the adhesive layer 30 is smaller when it flows into the recess 42 than when it flows into the through hole 21, so the amount of adhesive flowing into the recess 42 can be increased. .

Furthermore, since the recesses 42 are formed of through holes penetrating the metal plate 40 in the plate thickness direction, the air pushed out by the adhesive layer 30 does not stay inside the recesses 42 . Therefore, inside the recess 42 , the flow of the material of the adhesive layer 30 is not hindered by stagnant air bubbles, etc., and the adhesive layer 30 naturally flows into the recess 42 due to its own weight. In this manner, the material of the adhesive layer 30 can be actively flowed to the inside of the recess 42 with a simple configuration.

In addition, in the present embodiment, since each of the plurality of recesses 42 is formed at a position corresponding to the through hole 21 on the wiring board 20 side, the adhesive layer 30 flowing into the through hole 21 on the wiring board 20 side is material can be efficiently dispersed and guided to the recess 42 .

Further, in this embodiment, the adhesive layer 30 is made of an insulating material, and the adhesive layer 30 constitutes an insulating layer that ensures insulation between the wiring board 20 and the metal plate 40 . Therefore, compared with the configuration in which an insulating layer is formed separately from the adhesive layer 30, the insulating distance can be easily changed and adjusted, and the material cost can be reduced.

(Modified example of the first embodiment)
In the above-described embodiment, the plurality of recesses 42 formed in the metal plate 40 are arranged at positions corresponding to the through holes 21 on the wiring substrate 20 side. A common metal plate 40 cannot be used for the wiring board of the product. Therefore, from the viewpoint of increasing the versatility of the metal plate 40, the configuration of the metal plate 50 according to the modification shown in FIG. 4 may be applied. In addition, about the same component part as 1st Embodiment mentioned above, the same number is attached and the description is abbreviate|omitted.

As shown in FIG. 4, in the metal plate 50, a plurality of concave portions 42 are regularly arranged along the arrangement reference lines L arranged in a grid pattern. The plurality of recesses 42 are formed at positions where the vertical line L1 and the horizontal line L2 of the arrangement reference line L intersect, and are evenly arranged on the upper surface of the metal plate 50 at predetermined intervals.

According to the metal plate 50 configured as described above, it is possible to uniformly distribute a part of the adhesive layer material extruded during molding to the plurality of recesses 42 in the predetermined region where the plurality of recesses 42 are arranged. Therefore, since a joint substrate can be formed using a common metal plate between products of different types, versatility is excellent.

A bonding substrate 60 according to the second embodiment will be described below with reference to FIG. In addition, about the same component part as 1st Embodiment mentioned above, the same number is attached and the description is abbreviate|omitted. The bonding substrate 60 according to the second embodiment is characterized in that the recessed portions 64 formed in the metal plate 62 are configured by linear recessed grooves. Other configurations are the same as those of the first embodiment.

The metal plate 62 is bonded to the lower surface of the wiring board 20 via the adhesive layer 30 and has a plurality of recesses 64 at positions corresponding to the through holes 21 on the wiring board 20 side. The cross sections of the two recesses 64A and 64B shown in FIG. 5 both show the recesses 64 having the same configuration, but the recesses 64A are cut along the direction perpendicular to the extending direction of the recesses 64. , and a recess 64B shows a cross section of the recess 64 cut along the extending direction. As shown in this figure, as an example, the recess 64 is formed in the shape of a rectangular groove that opens toward the wiring board 20 , and one end 641 extending linearly reaches the end of the metal plate 62 . It has become. As a result, even when the metal plate 62 is bonded to the wiring board 20 , the space in the recess 64 does not become a closed space, and one end 641 leading to the end of the metal plate 62 is positioned inside and outside the recess 64 . are communicated.

(Action and effect)
According to the above configuration, one end 641 of the groove forming the recess 64 reaches the end of the metal plate 62 to allow communication between the inside and the outside of the recess 42 . Therefore, the material of the adhesive layer 30 that has flowed into the recess 64 allows the air pushed out from the recess 64 to be released to the outside through one end 641 . Therefore, since the air pushed out by the adhesive layer 30 does not stay inside the recess 64, the flow of the material of the adhesive layer 30 is not hindered, and the air naturally flows into the recess 64 by the weight of the adhesive layer 30. can be

Further, since the concave portion 64 is formed of a linear concave groove, it can be extended along the wiring pattern 22 of the wiring substrate 20, for example. In this case, one recess 64 can correspond to a plurality of through holes 21, and the flow of the adhesive layer 30 can be efficiently controlled.

(Modification of Second Embodiment)
In the above embodiment, the plurality of recesses 64 formed in the metal plate 62 are arranged at positions corresponding to the through holes 21 on the wiring board 20 side. The common metal plate 62 cannot be used for the wiring board 20 of the product. Therefore, from the viewpoint of increasing the versatility of the metal plate 62, the configuration of the metal plate 70 according to the modification shown in FIG. 6 may be applied. In addition, about the same component part as 2nd Embodiment mentioned above, the same number is attached and the description is abbreviate|omitted.

As shown in FIG. 6, in the metal plate 70, a plurality of recesses 64A extending in the vertical direction and a plurality of recesses 64B extending in the horizontal direction intersect and are regularly arranged to form a lattice. A plurality of recesses 64 ( 64 A, 64 B) forming a lattice shape may be formed in a predetermined area of the metal plate 70 or may be formed in the entire area of the metal plate 70 . When formed over the entire area of the metal plate 70 , both ends of the plurality of recesses 64 reach the ends of the metal plate 70 , so the recesses 64 can be formed in the metal plate 70 by cutting or forging. .

According to the metal plate 70 having the above configuration, it is possible to uniformly disperse part of the adhesive layer material extruded during molding in the predetermined area area where the recesses 64 are arranged. For this reason, a common metal plate can be used to form a joint substrate between products of different types, which is excellent in versatility.

A bonding substrate 80 according to the third embodiment will be described below with reference to FIG. In addition, about the same component part as 1st Embodiment mentioned above, the same number is attached and the description is abbreviate|omitted. This third embodiment is characterized in that a sheet piece 82 for closing the opening of the through hole 21 is provided on the lower surface (one side surface) of the wiring board 20 . Further, since the opening of the through hole 21 is closed by the sheet piece 82, the metal plate 84 does not have a structure corresponding to the recess 42 of the first embodiment. Other configurations are the same as those of the first embodiment.

As shown in FIG. 7, the wiring board 20 is provided with a plurality of sheet pieces 82 . Each of the plurality of sheet pieces 82 is a sheet-like small piece, and is arranged so as to close the openings of the plurality of through holes 21 formed in the wiring board 20 . The sheet piece 82 is composed of, for example, an adhesive sheet provided with adhesive surfaces on both sides of a sheet member made of an insulating material.

In the manufacturing process, first, with the protective film on one side of the adhesive sheet peeled off, half cuts in the shape of the sheet pieces 82 are formed on the surface of the adhesive sheet corresponding to the positions of the wiring board 20 . Next, using a peeling tape or the like, the surrounding adhesive sheet is peeled off so that only the sheet piece 82 remains on the protective film remaining on one side of the adhesive sheet. After that, the lower surface of the wiring board 20 is pressed from above the sheet piece 82 . Finally, by peeling off the remaining protective film, the sheet piece 82 that closes the opening of the through hole 21 is adhered to the lower surface of the wiring board 20 . The wiring board 20 is laminated on the metal plate 84 and the adhesive with the sheet piece 82 adhered thereto, and is joined using a pressing machine in the same manner as in the first embodiment.

(Action and effect)
According to the above configuration, the sheet piece 82 closes the opening of the through hole 21 formed in the wiring board 20 at the interface between the wiring board 20 and the adhesive layer 30 . Therefore, the sheet piece 82 can prevent part of the melted material of the adhesive layer 30 from flowing into the through hole 21 due to the pressure of the pressing machine, so that the material of the adhesive layer 30 does not enter the through hole 21 . Moreover, the sheet piece 82 is arranged only around the through hole 21, and the wiring board 20 and the metal plate 40 are bonded via the adhesive layer 30 having high thermal conductivity. As a result, deterioration in thermal conductivity due to the sheet piece 82 can be suppressed as much as possible, and desired heat transfer performance can be ensured.

[supplementary explanation]
Although the wiring board is configured as a multilayer board in each of the above-described embodiments and modifications, the present invention can also be applied to a single-sided board or a double-sided board.

In the first embodiment, the recess 42 of the metal plate 40 is configured as a through hole, but the present invention is not limited to this. may

In the third embodiment, one sheet piece closes one through-hole 21. However, when a plurality of through-holes 21 are provided close to each other, one sheet piece can close a plurality of through-holes 21. It may be configured to block the opening of the hole 21 .

REFERENCE SIGNS LIST 10 junction substrate 20 wiring substrate 30 adhesive layer 40 metal plate 21 through hole 42 concave portion 50 metal plate
60 bonding substrate 62 metal plate 64 recess (64A, 64B)
70 metal plate

Claims (7)

a wiring board having a through hole;
a metal plate bonded to one side surface of the wiring board via an adhesive layer,
the metal plate has a concave portion formed in a surface facing the through hole of the wiring board;
When the metal plate is bonded to one surface of the wiring board, part of the material of the adhesive layer enters the recess of the metal plate, so that the material of the adhesive layer passes through the through hole. a joint substrate configured so as not to protrude from the other side surface of the wiring substrate. 2. The bonding substrate according to claim 1, wherein an opening area of said recess is set larger than an opening area of said through hole of said wiring board. 3. The bonded substrate according to claim 1, wherein the recess is formed of a through hole penetrating through the metal plate in the plate thickness direction. The concave portion is composed of a linear concave groove,
2. The bonded substrate according to claim 1, wherein one end of said groove reaches an end of said metal plate. The bonding substrate according to any one of claims 1 to 4, wherein the recess is formed at a position corresponding to the through hole on the wiring substrate side. The bonded substrate according to any one of claims 1 to 5, wherein said metal plate has a plurality of said recesses arranged regularly. the material of the adhesion layer is made of an insulating material;
The bonded substrate according to any one of claims 1 to 6, wherein the adhesive layer constitutes an insulating layer.

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