JP2024004745A - Printed board structure and onboard apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve heat dissipation from electronic components that have two or more terminals having a potential difference.

SOLUTION: An electronic component 3 is located on a surface of a printed board 2. The printed board 2 comprises a first reverse side conductor layer 22a that is formed on a reverse side, a second reverse side conductor layer 22b that is formed on the reverse side and has a potential difference with respect to the first reverse side conductor layer, a first penetration part 23a that electrically connects a first terminal 3a of the electronic component 3 and the first reverse side conductor layer 22a, and a second penetration part 23b that electrically connects a second terminal 3b and the first reverse side conductor layer 22b. A first pattern part 29a is provided to the first reverse side conductor layer 22a and a second pattern part 29b is provided to the second reverse side conductor layer 22b, with the first and second pattern parts 29a, 29b covered with a resist part 25. Resist-less parts 27a, 27b that are not covered with the resist part 25 are provided to the first and second pattern parts 29a, 29b, respectively, with the resist-less parts 27a, 27b contacted with a heat dissipation sheet 41.

SELECTED DRAWING: Figure 2

COPYRIGHT: (C)2024,JPO&INPIT

Description

The present invention relates to a printed circuit board structure and in-vehicle equipment.

A printed circuit board with electronic components mounted thereon generates heat as the electronic components consume power. In order to prevent the functions and characteristics of electronic components from deteriorating when the amount of heat generated increases, a heat dissipating member such as a heat sink is sometimes attached to the printed circuit board. Hereinafter, a printed circuit board equipped with a heat dissipation member will be referred to as a "printed circuit board structure."

A semiconductor device as an example of a printed circuit board structure is disclosed in Patent Document 1 below. This semiconductor device includes a printed circuit board, electronic components on the printed circuit board, and a heat sink below the printed circuit board. The printed circuit board includes an insulating layer and a conductive layer. Each of the plurality of conductor layers includes a plurality of first conductor layers electrically connected to the electronic component, and a plurality of first conductor layers arranged at intervals and electrically insulated from each other. and a second conductor layer. a first through portion connected to each of the plurality of first conductor layers and extending from one main surface of the printed circuit board to the other main surface; It further includes a second penetrating portion extending from one main surface to the other main surface. The first conductor layer and the second conductor layer overlap in plan view at least in part, or are spaced apart from each other in the direction along one main surface.

International Publication No. 2017/208802

In the semiconductor device of Patent Document 1, it is necessary to laminate a plurality of conductive layers, so it is difficult to apply the semiconductor device to a case where there is no internal conductor layer, such as a double-sided substrate. In this case, heat dissipation from the semiconductor element may be insufficient depending on the circuit configuration.

Further, although the invention described in Patent Document 1 is intended to dissipate heat from semiconductor elements, heat generating parts are not limited to semiconductor elements, and electronic parts such as electrolytic capacitors, resistors, and inductors also generate a large amount of heat. It may happen. In particular, electrolytic capacitors, inductors, resistors, and the like used in power supply circuits tend to generate more heat due to the recent demand for higher output, so there is an urgent need to improve heat dissipation. These electronic components have at least two terminals with a potential difference, but the heat dissipation structure of Patent Document 1 lacks consideration of how to dissipate heat from the two terminals with a potential difference. There is.

For example, it has become difficult to ensure heat dissipation for in-vehicle equipment installed in automobiles due to the demand for compactness due to restrictions on installation space. Therefore, further improvement in heat dissipation is desired, especially in printed circuit board structures for in-vehicle equipment.

Therefore, an object of the present invention is to provide a printed circuit board structure that improves heat dissipation from an electronic component having two or more terminals that generate a potential difference.

In order to achieve the above object, the present invention provides a printed circuit board on which a circuit pattern is formed, an electronic component disposed on the surface of the printed circuit board and provided with a first terminal and a second terminal, and a A printed circuit board structure comprising: a heat dissipation member disposed on a back surface; the printed circuit board has a first back conductor layer formed on the back surface; a second back side conductor layer having a potential difference with respect to the second back side conductor layer; a first penetration part that penetrates the printed circuit board and connects the first terminal and the first back side conductor layer; a second through-hole that connects the two terminals and the second back-side conductor layer; a first pattern portion that is connected to the circuit pattern and forms a part of the circuit pattern, the second back side conductor layer is connected to the second through portion, and the second connection portion and a second pattern section that is connected to and forms another part of the circuit pattern, and the printed circuit board further includes an insulating resist section that covers the first pattern section and the second pattern section. , each of the first pattern part and the second pattern part is provided with an unresisted part that is not covered with the resist part, and each of the unresisted parts is brought into contact with the heat dissipation member.

With the printed circuit board structure described above, the heat generated in the electronic component passes through the first terminal → the first through part, and the second terminal → the second through part, and then passes through the first back side conductor layer and the second through part. Conducts to the back side conductor layer. This heat is conducted to the first pattern section via the first connection section of the first back side conductor layer, and is conducted to the second pattern section via the second connection section of the second back side conductor layer. The heat is then conducted to the heat radiating member that contacts each unregistered portion of the first pattern portion and the second pattern portion, and is emitted to the atmosphere. Since heat passes through a conductor with good thermal conductivity from the terminal to the unresisted area, the thermal resistance along this path is small. In addition, since the first pattern part and the second pattern part and the heat dissipation member are in direct contact with each other in the unregistered part without intervening the resist part with low thermal conductivity, between the first pattern part and the heat dissipation member, Each thermal resistance between the second pattern part and the heat dissipation member can be minimized.

Therefore, the heat generated by the electronic component can be smoothly conducted from the terminal to the heat radiating member via the printed circuit board, and can be released from the heat radiating member into the atmosphere. As a result, it is possible to improve the heat dissipation performance of an electronic component that has two or more terminals that generate a potential difference and whose heat is mainly dissipated from the terminals, and it is possible to prevent an unexpected temperature rise of the electronic component.

On the other hand, if the distance between the unregistered portions is too short, there is a risk that the first pattern portion and the second pattern portion may be short-circuited due to conductive foreign matter interposed between the two unregistered portions. In order to prevent this short circuit, it is preferable to make the distance between the two unregistered portions as large as possible.

Specifically, it is preferable that the unregistered portions be arranged at least a prescribed distance apart, with the prescribed distance being the sum of the assumed maximum size of the conductive foreign object and twice the minimum creepage distance. .

This makes it possible to improve the heat dissipation of the electronic component while preventing short circuits in the unregistered portions.

Further, it is preferable that the respective unregistered portions are arranged with a distance of 3.8 mm or more.

This makes it possible to improve the heat dissipation of the electronic component while preventing short circuits in the unregistered portions.

The area of the unregistered part of the first pattern part is made larger than the area of the first connection part, and the area of the unregistered part of the second pattern part is made larger than the area of the second connection part. is preferred.

Thereby, a sufficient heat conduction area can be ensured between the first pattern part and the heat radiating member and between the second pattern part and the heat radiating member, so that the heat radiation effect is enhanced.

As described above, according to the present invention, it is possible to improve the heat dissipation performance of an electronic component having two or more terminals that generate a potential difference.

FIG. 3 is a plan view of the printed circuit board structure seen from the front side. 2 is a sectional view taken along the line II-II in FIG. 1. FIG. FIG. 3 is an enlarged bottom view of the printed circuit board structure from the back side with the heat dissipation member removed. 4 is a schematic cross-sectional view taken along the line IV-IV in FIG. 3. FIG. FIG. 3 is a side view of the printed circuit board structure. It is a table showing minimum creepage distance.

Embodiments of the present invention will be described below based on FIGS. 1 to 6.

FIG. 1 is a plan view of the printed circuit board structure 1 seen from the front side, and FIG. 2 is a cross-sectional view taken along the line II--II in FIG. As shown in FIGS. 1 and 2, a printed circuit board structure 1 according to the present embodiment includes a printed circuit board 2, an electronic component 3 disposed on the front surface of the printed circuit board 2, which is a heat dissipation target, and a back surface of the printed circuit board 2. The main component is a heat dissipating member 4 disposed at.

As shown in FIG. 2, the printed circuit board 2 includes a base member 20 made of an insulating material, front-side conductor layers 21a and 21b formed on the front surface, and back-side conductor layers 22a and 22b formed on the back surface. have The front side conductor layers 21a, 21b and the back side conductor layers 22a, 22b are both formed of conductive foil such as copper foil (including copper alloy foil). In this embodiment, the two surface-side conductor layers 21a and 21b are formed as pads to which the terminals 3a and 3b of the electronic component 3 are soldered.

One of the back side conductor layers 22a (first back side conductor layer) has a first connection part 28a connected to a first penetration part 23a, which will be described later, and a first connection part 28a connected to the first connection part 28a to form an electronic circuit. A first pattern portion 29a constituting a part of the circuit pattern is provided (see FIG. 3). The other back side conductor layer 22b (second back side conductor layer) has a second connecting part 28b connected to a second through part 23b, which will be described later, and a second connecting part 28b connected to the second connecting part 28b to form an electronic circuit. A second pattern portion 29b constituting another part of the circuit pattern is provided (also see FIG. 3). The first connecting portion 28a is a portion located directly under one of the surface-side conductor layers 21a, and is directly connected to the first penetrating portion 23a. The second connecting portion 28b is located directly under the other surface-side conductor layer 21b, and is directly connected to the second penetrating portion 23a. Note that "connected" means being in an electrically connected state (the same applies hereinafter).

Note that the front-side conductor layers 21a and 21b may be configured as part of the circuit pattern. Further, the printed circuit board 2 may be a multilayer board in which a conductor layer is provided not only on the front side conductor layers 21a, 21b and the back side conductor layers 22a, 22b, but also on an intermediate portion apart from the front side and the back side. In this embodiment, the printed circuit board 2 is a rigid type in which the base member 20 is made of a rigid body, but a flexible type in which the base member 20 is made of a flexible material may also be used as the printed circuit board 2.

As the electronic component 3 to be heat radiated, an electronic component having two or more terminals 3a, 3b and generating a potential difference between the two terminals 3a, 3b, such as an electrolytic capacitor, is used. Electrolytic capacitor 3 is placed between the power supply and GND. One of the two terminals 3a and 3b pulled out from the inside (positive electrode), the first terminal 3a, is connected to the power supply side, and the other (cathode), the second terminal 3b, is connected to the GND side.

The electrolytic capacitor 3 generates heat corresponding to the product (I ² ×Rcon) of the square of the input/output current I and the internal resistance Rcon when power is supplied. The heat generated inside the capacitor is radiated to the outside through two routes: one is to conduct heat from the surface of the capacitor body to the surrounding air and radiate the heat, and the other is to conduct heat from the terminals 3a and 3b to the printed circuit board 2 and radiate the heat from the heat radiating member 4. There are two types of routes. Between the former and the latter, unless a heat dissipation member is attached to the surface of the capacitor body, the latter route usually radiates more heat than the former route. Therefore, the terminals 3a and 3b serve as main paths for conducting heat generated in the electrolytic capacitor 3 to the outside.

The terminals 3a and 3b are formed of the same material and the same shape using aluminum or copper (including aluminum alloy and copper alloy). Although there is some difference in the structure of the connection point between the terminals 3a and 3b and the capacitor body, the terminals 3a and 3b have approximately the same thermal conductivity.

As described above, the electronic component 3 in this embodiment is an electronic component 3 that is provided with two terminals 3a and 3b having a potential difference, and the terminals 3a and 3b serve as the main heat dissipation path. Other electronic components that meet the above conditions include resistors, inductors, and the like. These electronic components 3 are mounted on the printed circuit board 2 by soldering the first terminals 3a to the first surface-side conductor layer 21a and soldering the second terminals 3b to the second surface-side conductor layer 21b. . The electronic component 3 may have three or more terminals 3a, 3b. In addition to the electrolytic capacitors, resistors, and inductors exemplified above, other electronic components such as semiconductor elements can be mounted on the printed circuit board 2.

As shown in FIG. 2, the printed circuit board 2 is provided with a plurality of through parts 23a and 23b that penetrate the printed circuit board 2 and connect the front conductor layers 21a and 21b and the back conductor layers 22a and 22b. The through parts 23a and 23b can be formed of a conductor such as copper that covers the inner periphery of the hole 24 (through via) that penetrates the printed circuit board 2. The terminals 3a and 3b of the electronic component 3 may be inserted into the hole 24 and soldered to the through parts 23a and 23b.

The penetrating portions 23a and 23b are arranged near the respective terminals 3a and 3b of the electronic component 3, respectively. One end of the first penetration part 23a is connected to the first surface side conductor layer 21a to which the first terminal 3a of the electronic component 3 is soldered, and the second penetration part 23a is connected to the second surface side conductor layer 21b to which the second terminal 3b is soldered. One end of the portion 23b is connected. In this embodiment, the first penetration parts 23a and the second penetration parts 23b are provided at three places, but the number of the first penetration parts 23a and the second penetration parts 23b is arbitrary, and both penetration parts 23a, 23b The number of each may be one, two or four or more.

The other end of the first through part 23a is connected to the first connecting part 28a of the first back side conductor layer 22a, and the other end of the second through part 23b is connected to the second connecting part 28b of the second back side conductor layer 22b. has been done. In this electronic circuit, a potential difference exists between the first back side conductor layer 22a and the second back side conductor layer 22b. Note that the first back conductor layer 22a including the first pattern portion 29a has the same potential as the first terminal 3a of the electronic component 3, and the second back conductor layer 22b including the second pattern portion 29b has the same potential as the second terminal 3b. They have the same potential.

The surface of the printed circuit board 2, except for the area facing various electronic components (not limited to the electronic component 3 to which heat is radiated), the first surface-side conductor layer 21a, and the second surface-side conductor layer 21b, It is covered with a resist portion 25 that becomes an insulating film. The back surface of the printed circuit board 2 is also covered with an insulating resist section 25, and the first pattern section 29a and the second pattern section 29b are covered with the resist section 25. Note that the first connecting portion 28a and the second connecting portion 28b are not covered with the resist portion 25, and the first connecting portion 28a and the second connecting portion 28b are exposed. That is, the resist portion 25 on the back surface of the printed circuit board 2 is formed in an area excluding the first connection portion 28a and the second connection portion 28b. Of the first back-side conductor layer 22a and the second back-side conductor layer 22b, areas around the penetration parts 23a, 23b and not covered with the resist part 25 become connection parts 28a, 28b.

As shown in FIG. 2, as the heat dissipation member 4, an insulating heat dissipation sheet 41 and a heat sink 42 (heat dissipation fin) are used in this embodiment. The heat dissipation sheet 41 is placed in contact with the back surface of the printed circuit board 2. The heat dissipation sheet 41 is made of a material that is flexible enough to be deformed following the irregularities on the back surface of the printed circuit board 2 and has excellent thermal conductivity. The heat sink 42 is attached to the printed circuit board 2 in contact with the heat dissipation sheet 41.

FIG. 3 is an enlarged plan view of the printed circuit board structure 1 (with the heat dissipating member 4 removed) seen from the back side, and FIG. 4 is a cross-sectional view taken along the line IV--IV in FIG. As shown in FIGS. 3 and 4, in the printed circuit board structure 1, the first pattern section 29a and the second pattern section 29b are not covered with the resist section 25, and each pattern section 29a, 29b is exposed. Unregistered portions 27a and 27b are formed. The unregistered portions 27a and 27b are brought into contact with a heat radiation sheet 41 serving as a heat radiation member 4 (see FIG. 2). The unregistered portions 27a and 27b may be provided at one location in each of the pattern portions 29a and 29b, or may be provided at multiple locations in each of the patterned portions 29a and 29b. Note that in FIGS. 3 and 4, the dotted pattern represents the surface of the resist portion 25.

The area of one unregistered part 27a is made larger than the area of the first connecting part 28a that is not covered by the resist part 25, and the area of the other unregistered part 27b is made larger than the area of the first connecting part 28a that is not covered by the resist part 25. The area is made larger than the area of the connecting portion 28b. Thereby, a sufficient heat conduction area can be ensured and the efficiency of heat conduction to the heat dissipation member 4 can be increased.

Furthermore, from the viewpoint of improving heat dissipation, it is recommended to arrange one of the unregistered parts 27a and 27b close to the first connection part 28a, and arrange the other unregistered part 27b close to the second connection part 28b. preferable.

In the printed circuit board structure 1 described above, the heat generated in the electronic component 3 is transmitted from the first terminal 3a to the first surface-side conductor layer 21a to the first penetration portion 23a to the first connection portion 28a to the first pattern. The unregistered portion is passed through the first path consisting of the portion 29a and the second path consisting of the second terminal 3b → second surface-side conductor layer 21b → second penetration portion 23b → second connection portion 28b → first pattern portion 29b. It is conducted to 27a and 27b. Then, this heat is conducted to the heat dissipation sheet 41 that contacts the unregistered portions 27a and 27b, and further conducted to the heat sink 42 and released into the atmosphere. In the paths from the terminals 3a, 3b to the unregistered portions 27a, 27b, heat passes through conductors having good thermal conductivity, so the thermal resistance in each path is small.

Further, each pattern portion 29a, 29b and the heat dissipation sheet 41 are in direct contact with each other at unregistered portions 27a, 27b without intervening the resist portion 25 having low thermal conductivity. Therefore, the thermal resistance between each pattern portion 29a, 29b and the heat dissipation sheet 41 can be minimized. The heat dissipation sheet 41 may be brought into contact not only with the unregistered parts 27a and 27b, but also with one or both of the first connection part 28a and the second connection part 28b. Further, the heat dissipation sheet 41 may be made non-contact with either or both of the first connecting portion 28a and the second connecting portion 28b. Note that if the heat dissipation sheet 41 is brought into contact only with the first connection part 28a and the second connection part 28b without contacting with the unregistered parts 27a and 27b, the heat conduction area will be insufficient, so that sufficient heat dissipation effect cannot be achieved. cannot be expected.

With the printed circuit board structure 1 described above, as shown in FIG. , heat can be radiated from the heat sink 42. As a result, it is possible to improve the heat dissipation performance of the electronic component 3, which has two or more terminals that generate a potential difference and whose heat is mainly dissipated from the terminals 3a and 3b, and it is possible to suppress the temperature rise of the electronic component 3.

On the other hand, if the separation distance X (see FIG. 3) between the unregistered parts 27a and 27b is too short, conductive foreign matter that unexpectedly interposed between the unregistered parts 27a and 27b during the manufacturing process may cause the There is a possibility that the pattern portion 29a and the second pattern portion 29b may be short-circuited.

Specifically, this separation distance X is preferably set to be equal to or greater than a specified distance determined from the following formula.
Specified distance = maximum expected conductive foreign object size + minimum creepage distance x 2

In this embodiment, the conductive foreign matter is assumed to be a solder ball generated during a soldering process. The maximum size of the solder ball is approximately φ1 mm. The minimum creepage distance can be determined from the table (see FIG. 6) specified in the IEC standard (IEC62368-1). The minimum creepage distance depends on the voltage, contamination level, and material group, so it must be selected according to the manufacturing process and application. In this embodiment, the contamination level is 2 and the material group is IIIa. Furthermore, since the printed circuit board structure 1 of the present embodiment is intended to be used in in-vehicle equipment of an automobile (for example, an electric oil pump), the voltage is 12V, but considering the load dump voltage, the operating voltage is Assume 100V.

Under the above conditions, the minimum creepage distance is 1.4 mm from FIG. 6, so the specified distance is 1 mm+1.4 mm×2=3.8 mm. Therefore, it is preferable that the distance X between the unregistered portions 27a and 27b is 3.8 mm or more. This makes it possible to improve the heat dissipation of the electronic component 3 while preventing short circuits in the unregistered portions 27a and 27b.

Although the use of the printed circuit board structure 1 described above is not particularly limited, it can be used, for example, in a power supply circuit. As the electronic component 3 to be heat radiated, a power supply smoothing capacitor in a power supply circuit, an inductor or capacitor of an LC filter, an inductor of a step-up circuit or a step-down circuit, a current detection resistor, etc. can be applied.

The printed circuit board structure according to the present invention can be widely used in devices that require compactness. For example, in-vehicle equipment for automobiles is constantly required to be made more compact, but there is a problem that the more compact the equipment is, the lower its heat dissipation performance becomes. By using the above-described printed circuit board structure in such in-vehicle equipment, it is possible to meet the demand for downsizing of in-vehicle equipment while ensuring sufficient heat dissipation. Examples of this type of in-vehicle equipment include, in addition to the electric oil pump already mentioned, a vehicle control unit (VCU), an inverter, a DC-DC converter, an electric actuator, and the like.

1 Printed circuit board structure 2 Printed circuit board 3 Electronic component 3a First terminal 3b Second terminal 4 Heat radiation member 21a First front side conductor layer 21b Second front side conductor layer 22a First back side conductor layer 22b Second back side conductor layer 23a First penetration part 23b Second penetration part 25 Registration part 27a Unregistered part 27b Unregistered part 28a First connection part 28b Second connection part 29a First pattern part 29b Second pattern part 41 Heat dissipation sheet 42 Heat sink

Claims (5)

A printed circuit board comprising: a printed circuit board on which a circuit pattern is formed; an electronic component disposed on the surface of the printed circuit board and having a first terminal and a second terminal; and a heat dissipation member disposed on the back surface of the printed circuit board. A structure,
The printed circuit board has a first back side conductor layer formed on the back side, a second back side conductor layer formed on the back side and having a potential difference with respect to the first back side conductor layer, and a second back side conductor layer that penetrates the printed board. a first penetration part that connects the first terminal and the first back side conductor layer through the printed circuit board, and a second penetration part that penetrates the printed circuit board and connects the second terminal and the second back side conductor layer. Prepare,
The first back side conductor layer includes a first connection part connected to the first penetration part, and a first pattern part connected to the first connection part and forming a part of the circuit pattern,
The second back side conductor layer includes a second connection part connected to the second penetration part and a second pattern part connected to the second connection part and forming another part of the circuit pattern. Prepare,
The printed circuit board further includes an insulating resist portion covering the first pattern portion and the second pattern portion,
A printed circuit board structure characterized in that each of the first pattern part and the second pattern part is provided with an unresisted part that is not covered with the resist part, and each of the unresisted parts is brought into contact with the heat dissipation member. . 2. The print according to claim 1, wherein each of the unregistered portions is arranged at least a specified distance apart, with the specified distance being a value obtained by adding twice the minimum creepage distance to the maximum size of an assumed conductive foreign object. Substrate structure. 2. The printed circuit board structure according to claim 1, wherein the unregistered portions are spaced apart from each other by 3.8 mm or more. The area of the unregistered part of the first pattern part is larger than the area of the first connection part, and the area of the unregistered part of the second pattern part is larger than the area of the second connection part. The printed circuit board structure according to item 1. An in-vehicle device comprising the printed circuit board structure according to any one of claims 1 to 4.

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