JPH07161540A - Coil component - Google Patents

Abstract

PURPOSE:To enhance heat dissipation efficiency by setting the contact area, at an end part to be jointed with a high thermal conductivity member, at a predetermined value or above thereby improving the thermal conductivity at a lead-out part. CONSTITUTION:The contact area at the lower bent part, i.e., the connecting end part 36A, of each lead-out part is set at 3mm<2> or above so that the heat of copper loss can be transmitted efficiently to the board side. Consequently, the heat dissipation efficiency of a coil component can be enhanced significantly. The thermal conduction efficiency does not vary significantly even if the length of leg L10 or the plate thickness L' (T) at the lead-out part of a transformer component for small sized power supply is varied. On the contrary, the contact area S controls the thermal conduction efficiency which can be varied significantly by varying the contact area S.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a coil component such as a transformer, and more particularly to a coil component having improved heat radiation efficiency.

[0002]

2. Description of the Related Art Generally, a coil component such as a transformer, a choke coil, a noise filter is formed by winding a conductive wire many times, or a plurality of copper foil coils formed on a thin insulating plate made of resin or the like is laminated. Then, the copper foil coil of each layer is appropriately connected and formed, and rod-shaped pins or the like electrically connected to these are projected from the end and soldered to a printed circuit board or the like. Here, a conventional coil component will be described by taking a transformer for a switching power supply as an example. FIG. 9 shows a side view of a transformer for a conventional switching power supply. This transformer 2 has a large number of windings with an insulating tape interposed. The coil in the winding portion 4 is composed of a wound winding portion 4 and a core 6 made of, for example, ferrite, which surrounds the central portion and the outer periphery of the winding portion 4, and the coil in the winding portion 4 has a rod-shaped primary side and a secondary side. The side lead pins 8 and 10 are electrically connected. And
The lower ends of the lead pins 8 and 10 are attached to the printed circuit board 12.
Is soldered to the pattern.

Another conventional transformer is shown in FIG.
As shown in FIG. 0, a copper foil coil 16 is formed by etching on an insulating plate 14 made of a very thin resin or the like, and a large number of insulating plates 14 with a copper foil coil thus formed are maintained while maintaining the insulating state of the coil. Stack the sheets. Then, a plurality of lead pins 18A and 18B for selectively electrically connecting the plurality of laminated copper foil coils 16 are provided. In the illustrated example, the primary side lead pin 18A is provided on one side of the transformer, and the secondary side lead pin 18B is provided on the other side. A core 20 made of, for example, ferrite is provided so as to cover the inside and the outside of the transformer itself, and the lead pins 18A and 18B are provided.
Was attached to the printed circuit board by soldering in the same manner as shown in FIG.

[0004]

By the way, for example, OA
With regard to coil components used for switching power supplies such as devices, for example, transformers, miniaturization and thinning are desired from the viewpoint of effective use of space, and therefore higher frequencies are being promoted. In this way, as the frequency increases, the size of the coil component itself can be reduced and miniaturization can be achieved, but in this case, the surface area etc. is also reduced, so that the heat radiation efficiency is significantly reduced. Problems occur. Further, due to the skin effect in which the current concentrates on the outer peripheral portion of the conductor due to the high frequency, and the proximity effect in which the current is biased in the conductor due to the interaction with the magnetic field generated by the high frequency current flowing in other adjacent conductors, For this reason, the cross-sectional area of the conductor is equivalently reduced, the AC resistance is significantly increased, and the amount of heat generated due to copper loss is rapidly increased.

The situation at this time is shown in FIG. FIG. 11 shows the frequency characteristics of the AC resistance of the transformer. As is clear from the figure, the drive frequency is from 5 kHz to 5 kHz.
When it is increased to about 00 KHz, the AC resistance of the coil is doubled, and the amount of heat generation is also greatly increased. Under such circumstances, the transformer component having the above-described structure has a problem in that it cannot sufficiently dissipate heat and cannot cope with further higher frequency and smaller size. The present invention has been made to pay attention to the above problems and to solve them effectively. An object of the present invention is to provide a coil component in which the connection area of the connection end portion connected to the high thermal conductivity member is set to 3 mm ² or more to improve the thermal conductivity of the drawer portion and improve the heat dissipation efficiency. It is in.

[0006]

According to the present invention, when the plate thickness and length of the lead-out portion are set within a reasonable design range, the heat radiation effect of the coil depends on the connection area between the lead-out portion and the high thermal conductive member. We have found that the rate is controlled, and by setting the connection area between this and the board to 3 mm ² or more, the copper loss heat can be efficiently transmitted to the board side and efficient heat dissipation can be achieved. It was made by finding out.

In order to solve the above problems, the present invention provides
In a coil component that is connected to a coil plate through a lead-out portion, the end portion of the lead-out portion is bent to form a connection end portion that is connected to a high thermal conductivity member, and the connection area of this connection end portion is 3 mm. ^It is configured to be set to ² or more.

[0008]

Since the present invention is configured as described above, when there are a plurality of coil plates, for example, each coil plate is laminated while maintaining an insulating state. Each of them is selectively connected by a lead-out portion having a predetermined heat conduction cross-sectional area and soldered to a pattern of a printed circuit board or the like, for example. Therefore, the heat generated by the copper loss in each coil plate is efficiently conducted to the printed circuit board side, which is a high thermal conductive member, through the plate-shaped lead-out portion, and the heat dissipation of the coil component itself can be effectively performed. It will be possible. At this time, the connection areas of the connection end portions connected to the board are set to 3 mm ² or more, respectively, to significantly reduce the contact thermal resistance in this area, and to improve the efficiency of conduction of copper heat loss to the board side. Especially high.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the coil component according to the present invention will be described below in detail with reference to the accompanying drawings. 1 is an enlarged perspective view showing a drawn-out portion of a coil component according to the present invention, FIG. 2 is a perspective view showing the coil component of the present invention, and FIG. 3 is a diagram showing a state in which the coil component of the present invention is attached to a metal substrate, FIG. 4 is a schematic configuration diagram showing an embodiment of the coil component according to the present invention. In this embodiment, as the coil component, a transformer of a switching power supply device will be described as an example.

As shown in the figure, the transformer 22 as a coil component has a primary coil plate 24 and a secondary coil plate 26 as coil plates. The primary-side coil plate 24 is formed into a quadrangular ring shape, a part of which is cut out by a copper plate having a thickness L1 of 0.1 mm or more and a width L2 of about 5 mm. Lead-out parts 30 and 32 made of the same member as the primary side coil plate 24, that is, a conductive plate, are connected to the ends of the side coil plates 24 in a downward direction, and their tips are bent in a horizontal direction to be connected. Ends 30A and 32A are formed. Therefore, the primary coil plate 24 is configured as a one-turn coil. Specifically, the primary side coil plate 24 and the lead-out portion 3
0 and 32 are formed, for example, by punching out a single copper plate, and the lead portions 30 and 32 are directed downward by bending the connection portion with the coil plate 24. The thickness L3 of the drawer portions 30 and 32 is set to, for example, 0.1 mm or more, and the width L4 is, for example, several mm.
And has a heat conduction area sufficient to efficiently conduct the heat of copper loss (Joule heat or the like) generated in the primary side coil plate 24.

On the other hand, the secondary coil plate 26 is also constructed in substantially the same manner as the primary coil plate 24. Specifically, the secondary coil plate 26 is composed of, for example, two coil plates 26A and 26B.
26B is formed in a quadrangular ring shape in which a part is cut out by a copper plate having a thickness L5 of 0.1 mm or more and a width L6 of about 5 mm. At the ends of the coil plates 26A and 26B on the side of the cutout portion 34, the secondary side coil plate 26 is formed.
The same member, that is, the drawer portion 36 made of a conductive plate,
38, 40, and 42 are connected downward, respectively, and the tips thereof are bent in the horizontal direction so that the connection end 36 is formed.
A, 38A, 40A and 42A are formed. Therefore, each of the coil plates 26A and 26B is configured as a one-turn coil. Specifically, each of the secondary side coil plates 26A, 26B and each of the lead portions 36 to 42 are formed by punching out, for example, one copper plate in the same manner as described above, and each of the lead portions 36, 38, 40,
42 is a connection part 44, 4 with the coil plates 26A and 26B.
It is directed downward by bending 6, 48 and 50. The thickness L7 of each of the drawer portions 36, 38, 40, 42 is set to, for example, 0.1 mm or more, and the width L8.
Is set to, for example, several mm, and has a heat conduction area sufficient to efficiently conduct the heat of copper loss generated in the secondary coil plates 26A and 26B.

Then, one lead-out portion 36 of the secondary coil plate 26A and one lead-out portion 40 of the other secondary coil plate 26B are horizontally displaced so as not to come into contact with each other when the coils are piled up. Formed. The other lead-out portion 38 of the secondary coil plate 26A and the other lead-out portion 42 of the other secondary coil plate 26B are positioned in the horizontal direction in the same manner as described above so as not to come into contact with each other when the coils are stacked. It is formed by shifting. These two secondary side coil plates 26A and 26B are connected in series in the end so that the inner side lead-out part 38 of one secondary side coil plate 26A and the inner side lead-out part of the other secondary side coil plate 26B are connected. 40 and 40 are coupled by, for example, a conductive coupling member 62 so that a current flows.

The secondary coil plates 26A, 2
The primary side coil plates 24 are inserted between 6B via an insulating plate 52 made of, for example, a resin, and the coil plates are laminated in an insulated state. Then, as shown in FIG.
4, 26 as a whole, the drawer parts 30, 32, 36, 3
The transformer 22 itself is completed by covering 8, 40 and 42 with a magnetic material 54 such as ferrite. In this case, the magnetic body 54 is also arranged as a core in the central portion of each coil plate 2 and the magnetic body 54 is also arranged in the coil plate 2 described above.
Insulated from 4, 26.

At this time, one lead-out portion 38 of the secondary coil plate 26A and one lead-out portion 42 of the other secondary coil plate 26B are connected via the conductive coupling member 62, and therefore, The secondary coil is a 2-turn coil,
Further, the primary coil is configured as a one-turn coil. In the illustrated example, the case of combining the one-turn coil and the two-turn coil has been described for simplification of description, but in reality, each has a large number of turns.

As shown in FIG. 1 and FIG. 3, each lead-out portion of the transformer 22 thus constructed has a high thermal conductivity member such as aluminum having a thickness of about 1 mm for improving heat dissipation efficiency. The copper foil pattern 59 (see FIG. 1) formed on the metal plate 56 made of epoxy resin with an insulating film 58 made of epoxy resin and having a thickness of about 80 μm is connected to a predetermined position by soldering or the like. Here, in this embodiment, as shown in FIG.
Connection end portions 30A, 32A, which are lower end bent portions of 6 to 42,
The connection area of 36A to 42A is set to 3 mm ² or more so that copper loss heat can be efficiently transmitted to the substrate 60 side.

In FIG. 1, the drawer portion 36 is shown as an example of each drawer portion, and the drawer portion 3 is shown.
The length L10 of the leg portion of 6 is set to, for example, about 5 mm, and the area S of the connecting end portion 36A bent in the horizontal direction in the drawing is S.
Is set to 3 mm ² or more, preferably 4 mm ² or more. That is, assuming that the length of the connection end portion 36A is L11, the relationship between this and L8 is set as in the following equation. L8 × L11 ≧ 3 mm ² The lower surface of the connection end portion 36A is connected to the copper foil pattern 59 on the substrate 60 by soldering or the like to fix the coil component.

In this case, since each coil plate has two lead-out parts, the number of coil plates is 2, 3, 4, depending on the number of coil plates in the entire coil.
When the number of sheets is 5, the total number of drawers is 4, 6, 8, and 10, respectively. Since it is necessary to hold the load of the coil component only by connecting these lead-out portions, the lead-out portion 36
Thickness L7 and thickness T of the connecting end portion 36A (equal to L7)
Is 0.2 mm or more, so that the coil component can be supported while ensuring a certain level of physical strength.

As described above, the area S of the connecting end portion 36A is set to 3
By setting it to mm ² or more, the heat dissipation efficiency of copper loss heat of the coil component can be greatly improved.
The reason for this is that as a transformer component for a switching power supply which is downsized, the heat conduction efficiency is not so great even if the leg length L10 and the plate thickness L7 (T) of the drawer portion are changed within the allowable range. This is because the connection area S does not change and the heat conduction efficiency is controlled by the connection area S, and the heat conduction efficiency can be largely changed by changing the rate. This will be described with reference to the concept of thermal resistance and FIG. 5. FIG. 5 shows a state in which heat from a heat source 64 corresponding to a coil plate flows through each thermal resistance and is finally transmitted to the heat radiating side which is the substrate 60. Shows.

First, in consideration of heat conduction, from the heat source 64, the conduction heat resistance R1 of the portion corresponding to the leg portion of the length L10 of the extraction portion 36 and the connection portion heat resistance between the connection end portion 36A and the substrate 60. R2 is connected in series toward the substrate 60, which is a high thermal conductivity member. And considering the heat dissipation,
A heat dissipation resistor R3 that regulates the amount of heat that is dissipated into the atmosphere from the legs is connected in parallel to the series circuit.
Here, the conduction heat resistance R1 and the dissipation heat resistance R3 change too much even if they are changed within an appropriate range used as a transformer component, except when the length L10 or the thickness L7 of the leg portion of the drawer portion is extremely changed. On the other hand, the thermal contact resistance R2, which changes depending on the connection area S, fluctuates greatly, which limits the heat conduction efficiency. Therefore, as described above, by setting the connection area S to 3 mm ² or more, it is possible to greatly reduce the thermal resistance and significantly improve the heat conduction efficiency.

Next, the operation of this embodiment configured as described above will be described. First, the drawing-out portion 30 of each coil plate 24, 26A, 26B constituting the transformer 22,
32, 36-42 connection ends 30A, 32A, 36A,
38A, 40A and 42A are soldered and connected to the copper foil pattern 59 on the metal substrate 60 which is a high thermal conductive member. In this case, the lead-out portions 38, 40 inside the secondary side coil plates 26A, 26B are electrically connected by the conductive coupling member 62 so that a current flows through the entire secondary side coil plate 26.

When a current flows through the primary coil plate 24 and the secondary coil plates 26A and 26B in the above-described state, Joule heat is generated in each coil plate due to copper loss. This Joule heat is generated by, for example, the primary coil plate 2
In FIG. 4, it is transmitted through the lead portions 30 and 32, and is transmitted to the metal portion 56 of the metal substrate 60 via the connecting end portions 30A and 32A at the lower end portion. Therefore, the Joule heat due to the copper loss of the primary side coil plate 24 is effectively radiated.
Similarly, in the secondary side coil plates 26A, 26B, the Joule heat due to copper loss is transmitted through the lead portions 36, 38, 40, 42, and the metal portion 56 of the metal substrate 60 via the connecting end portions 36A, 38A, 40A, 42A. Be transmitted to. Therefore, similarly, the Joule heat due to the copper loss of the secondary side coil plates 26A and 26B is also effectively radiated.

In this case, in order to enhance the heat radiation effect, it is preferable to set the heat conduction cross-sectional area of each of the drawer portions 30, 32, 36, 38, 40 and 42 to a large value. It will be set according to the capacity or the amount of heat generation in the secondary side coil plates 26A and 26B to which the lead-out portion is connected, and in order to efficiently dissipate heat, the thickness of each lead-out portion is set as described above. It is preferable to set the width to, for example, 0.2 mm or more and the width to 2 mm or more. In this way, each coil plate is made of a metal plate such as a copper plate, and a part of this metal plate is drawn out as it is as a drawer portion without providing a relay terminal or the like, and a predetermined heat conduction interruption is made to this drawer portion. Since the area is provided, the copper loss heat generated in the coil plate can be efficiently radiated to the metal substrate 60 side through the lead-out portion. The lead-out portion is not limited to the copper plate, and any material may be used as long as it is a metal plate having electrical conductivity and thermal conductivity.

Further, in the present invention, in order to further enhance the heat radiation effect, the connecting end portions 30A, 32A, 36 of the respective lead-out portions are provided.
The connection area of A, 38A, 40A, 42A is set to 3 mm ² or more. Therefore, as shown in FIG. 1, the copper loss heat H1 generated in the coil plate is transmitted through the lead-out portion, for example, the legs of 36, and a part of the copper loss heat H2 is dissipated to the atmosphere, and most of The copper loss heat H3 is radiated from the connection end portion, for example, 36A, to the substrate 60 side, and high heat radiation efficiency can be exhibited. FIG. 6 is a graph showing the temperature rise of the coil plate when the connection area is changed at the time of a copper loss of 2 watts, and in the graph, the curve A1 is the lead-out portion, that is, the plate thickness T of the connection end portion is 0.5 mm. In the case of, the curve A2 shows the case where the plate thickness T is 2 mm. The output voltage at this time was 5 V, and a current of 40 amperes was passed.

As is apparent from the figure, as the connection area S is increased, the amount of temperature rise sharply decreases, and the plate thickness T
Irrespective of the above, the reduction rate greatly changes at the connection area of 3 mm ² , and an inflection point is observed here. That is, by setting the connection area S to 3 mm ² or more, preferably 4 mm ² or more, regardless of the plate thickness T, the copper loss heat generated in the coil plate can be efficiently generated in the metal substrate 60.
It turned out that heat can be released to the side. It should be noted that even if the wattage of copper loss or the plate thickness is changed, a characteristic curve similar to the curves A1 and A2 is shown, and in each case, an inflection point appears at a connection area of about 3 mm ² .

As described above, the reason why the temperature rise greatly depends on the connection area is that the copper heat loss H2 radiated from the leg portion of the extraction end portion is conducted from the connection end portion 36A to the substrate 60 side as described above. This is because it is much smaller than the copper heat loss H3, and the connection area S controls the heat dissipation efficiency of the coil plate.
Further, the heat generated by the iron loss of the magnetic body 54 that constitutes the core of the transformer 22 causes the metal substrate 60 with which the core is in direct contact.
The heat can be dissipated via.

In the above-mentioned embodiment, each coil plate and its lead-out portion are constructed as an integral body, but the present invention is not limited to this, and the coil plate and the plate-like lead-out portion may be connected by soldering or the like. May be. Further, although both the primary side coil plate 24 and the secondary side coil plates 26A and 26B are configured by plate-shaped members, the present invention is not limited to this, and one of the coil plates is replaced by a winding made of a normal copper wire. A coil is used on the primary side or the secondary side by a wire and an insulating tape wound around it,
Therefore, it can be applied to the case where the terminal is formed by the lead pin. In this case, the winding used is in close contact with the other coil plate via the insulating tape,
Joule heat or the like on the winding side can be efficiently transmitted to the coil plate side, and in this case as well, the heat dissipation efficiency of the entire transformer can be improved.

Further, in the above embodiment, the lead-out portion is connected to the metal substrate 60 side, but the present invention is not limited to this, and the lead-out portion may be connected to a radiator or the like via, for example, a thin insulating sheet. You may Although a thin rectangular parallelepiped shape was used as the transformer 22 in the above-described embodiment, the shape of the transformer is not limited to the shape of the transformer. For example, as shown in FIG. It can also be applied to a transformer formed by forming a core 70 around the line portion 68. In this case, a lead-out portion 72 having a predetermined heat conduction cross-sectional area is pulled out from the lower side surface of the winding portion 68, and the tip end portion is bent in the same manner as shown in FIG. 1 to form a connecting end portion 72A, This is connected to the metal substrate 60. Also, as the substrate, an aluminum nitride substrate,
A boron nitride substrate or the like can also be used.

Further, in the above embodiment, the coil plate 2
Although a metal plate having a thickness of, for example, about 0.2 mm is used as each of 4, 26A, and 26B, the present invention is not limited to this. For example, a coil plate having a thickness as shown in FIG. About 30 to 150 μm metal foil 7
It is also applicable to the case of using 6, 78. In FIG. 8, the primary side coil plate is omitted and only the secondary side coil plate is shown. Specifically, the secondary coil plate 80 is composed of metal foils 76, 78 made of copper or the like deposited on the surfaces of the insulating plates 82, 84 made of thin resin or the like by a thin film forming operation. The metal foils 76 and 78 are formed in a quadrangular ring shape, a part of which is cut,
Lead-out portions 36, 38, 40, 42 made of a conductive plate are formed in the same manner as shown in FIG. 4 so as to vertically penetrate the metal foil in the vicinity of the cut portion. Each penetrating portion is electrically connected to the metal foil with, for example, solder. Each of the lead-out portions 36, 38, 40 and 42 has a thickness of about 0.2 mm and a width of about several mm as described above, and has a heat conduction cross-sectional area of a predetermined size. Is configured. In addition, the connecting end 36 of each drawer
The connection area of A, 38A, 40A and 42A is set to be 3 mm ² or more.

Then, the two secondary side metal foils 76, 78
A transformer is formed by inserting a metal foil on the primary side (not shown) between them and stacking them. Also in this case, the Joule heat or the like generated in the metal foils 76, 78 is radiated to the metal substrate 60 side through the lead-out portions 36, 38, 40, 42 made of plate-shaped members. At this time, the contact areas of the connection end portions are set to be 3 mm ² or more, respectively, so that the heat generated by the transformer itself can be radiated more efficiently.

Further, as a result of being able to greatly improve the heat generation efficiency of the coil component itself, further miniaturization and thinning due to higher frequency can be promoted, and a switching power supply incorporating such a coil component can be miniaturized. Can also be promoted. In the above embodiments, the transformer is used as an example of the coil component, but the present invention is not limited to this, and the present invention can be applied to other coil components such as a choke coil and a noise filter. .

[0031]

As described above, according to the coil component of the present invention, the following excellent operational effects can be exhibited. The heat generated in the coil component, particularly the heat generated due to copper loss, can be efficiently dissipated through the plate-shaped drawer portion, and the heat dissipation efficiency of the coil component itself can be significantly improved. . Moreover, since the connection area of each connection end connected to the substrate is set to 3 mm ² or more, the thermal resistance is extremely reduced, and the heat dissipation efficiency of the coil component itself can be further improved. Therefore, as the frequency becomes higher, the output of the coil component itself can be increased, the size and thickness of the coil component can be reduced, and the size of the switching power supply using the coil component can be reduced.

[Brief description of drawings]

FIG. 1 is an enlarged perspective view showing a lead-out portion of a coil component according to the present invention.

FIG. 2 is a perspective view showing a coil component of the present invention.

FIG. 3 is a plan view showing a state where the coil component of the present invention is attached to a metal substrate.

FIG. 4 is a schematic configuration diagram showing an embodiment of a coil component according to the present invention.

FIG. 5 is a diagram showing a thermal resistance equivalent circuit of a drawer portion.

FIG. 6 is a graph showing a temperature rise of the coil plate when the connection area is changed at the time of copper loss of 2 watts.

FIG. 7 is a plan view showing another coil component to which the present invention is applied.

FIG. 8 is a schematic configuration diagram showing another embodiment of the present invention.

FIG. 9 is a plan view showing a conventional transformer.

FIG. 10 is a partial cross-sectional perspective view showing another conventional transformer.

FIG. 11 is a graph showing frequency characteristics of AC resistance of a transformer.

[Explanation of symbols]

 22 Transformers (Coil Parts) 24 Coil Plates (Primary Side) 26A, 26B Coil Plates (Secondary Side) 30, 32 Drawouts 30A, 32A Connection Ends 36, 38, 40, 42 Drawouts 36A, 38A, 40A, 42A Connection end portion 52 Insulation plate 54 Magnetic material 60 Metal substrate (high thermal conductivity member) 72 Draw-out portion 72A Connection end portion 76, 78 Metal foil (coil plate) S Connection area

Claims (1)

[Claims] 1. A coil component formed by connecting to a coil plate through a lead-out portion, wherein an end portion of the lead-out portion is bent to form a connecting end portion to be connected to a high thermal conductivity member, and the connecting end portion is formed. The coil component is characterized in that the connection area of is set to 3 mm ² or more.