JP2018006675A - Printed circuit board - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a printed circuit board that is able to improve a quantity of heat applied to mount a component to a conductive layer, without changing the shape of a connecting conductor part for connecting an outside conductor part and the conductive layer (rand), in order to form a thermal rand.SOLUTION: A printed circuit board comprises: a plurality of wiring layers 2 having at least one solid wiring layer; a through-hole 3 on the peripheral wall of which a conductive layer 41 connected to the wiring layer 2 is formed; and an insulation layer 51 disposed on an outer end face exposed at each end in a thickness direction. At least one of the outer end faces has a heat transfer face 6 that thermally conducts with the conductive layer 41.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a printed circuit board, and more particularly to a printed circuit board that is a laminated board and includes a conductive layer for soldering that is performed when electronic components are mounted.

In general, a conductive layer (hereinafter referred to as “land”) is formed on a printed circuit board configured as a multilayer substrate, and the land and terminal pins of an electronic component (element or the like) are connected by soldering. And when performing such soldering, the solder containing lead was conventionally used.
However, environmental problems have recently been recognized as an important issue, and so-called “lead-free solder” that does not use lead, which is a heavy metal, has come to be used.
However, this lead-free solder has a higher melting point than conventional lead-containing solder, and therefore there is a problem that soldering cannot be performed unless a higher temperature is maintained.
In order to solve such problems, a so-called “thermal land” is often used.
When the thermal land is used, heat dissipation in the land is suppressed during soldering, and the temperature of the solder is unlikely to decrease, so that soldering can be performed efficiently (for example, see Patent Document 1).

Patent Document 1 discloses a multilayer printed wiring board.
The multilayer printed wiring board has a through hole, and a thermal land for suppressing thermal diffusion during soldering is formed around the through hole.
The thermal land includes an annular conductor portion (corresponding to a land) so as to surround the through hole, a plurality of insulating portions disposed outside the annular conductor portion (corresponding to the land), and outside the insulating portions. And an outer conductor portion disposed.
And in such a technique, in order to make conduction | electrical_connection favorable, four connection conductor parts (center angle 90 degree isolation | separation) which connect an annular conductor part (equivalent to a land) and an outer side conductor part to radial direction are separated. Is formed).

JP 2009-206327 A

In such a technique, when soldering is performed on the annular conductor (corresponding to a land), the path through which heat is diffused is only the connecting conductor, which is advantageous in terms of reducing heat loss. .
However, since the fact that the heat of the solder is released from the connecting conductor portion does not change, it is necessary to aim at further improvement in the amount of heat used in the annular conductor portion. In particular, when the periphery is a solid pattern, the heat release becomes significant, and thus a technique for improving the amount of heat used is further desired from this point.
Thus, in order to improve the amount of heat used in the annular conductor, one method is to further suppress heat release from the annular conductor. As an example of this, it is conceivable to reduce the area of the connecting conductor part (that is, to narrow the width). However, if the area of the connecting conductor part is reduced (that is, the width is narrowed) in this way, the energization allowable current amount There was a problem that became smaller.
Under such circumstances, when using a thermal land having a connecting conductor, the amount of heat used in the annular conductor (corresponding to a land) is maintained while maintaining the allowable current flow without changing the structure of the connecting conductor. The development of a technology that can improve the performance has been desired.

  An object of the present invention is to solve the above-described problems, and in forming a thermal land, the conductive layer is formed without changing the shape of the connecting conductor portion that connects the outer conductor portion and the conductive layer (land). An object of the present invention is to provide a printed circuit board capable of improving the amount of heat given to the (land) for component mounting.

  According to the printed circuit board according to the present invention, the above-described problem is that a plurality of wiring layers having at least one solid wiring layer, a through hole in which a conductive layer connected to the wiring layer is formed on a peripheral wall surface, and a thickness direction And an insulating layer disposed on the outer end surface exposed at both ends of each of the outer end surfaces, and at least one of the outer end surfaces is formed with a heat transfer surface that is in thermal communication with the conductive layer. Solved.

Thus, since it is comprised, when heat is applied to the heat transfer surface, heat can be conducted to the conductive layer (land).
Therefore, in the conductive layer (land), the amount of heat for soldering can be improved, and the soldering workability is improved.

In this case, specifically, it is preferable that the heat transfer surface is the wiring layer exposed from the insulating layer because the heat transfer surface can be easily formed.
Furthermore, at this time, as another specific configuration, the heat transfer surface is a heat conductive member formed on an outer surface of the insulating layer, and the heat conductive member is directly or indirectly. It is preferable that the conductive layer is connected to the conductive layer so as to be able to conduct heat because the heat transfer surface can be easily formed even in this configuration.
Moreover, in this another concrete structure, the said heat conductive member is good to be connected with the said conductive layer by the heat conductive conducting wire.
And since a conductive layer (land) comprises a thermal land, the thermal efficiency in a conductive layer (land) further improves.

According to the present invention, a heat transfer surface is provided separately from the conductive layer (land), and the heat transfer surface is thermally connected to the conductive layer (land). By having such a structure, when heat is applied to the heat transfer surface, the heat is conducted to the conductive layer (land).
Thereby, when soldering to a conductive layer (land), high heat quantity can be secured.
Therefore, in forming the thermal land, without changing the shape of the connecting conductive portion connecting the outer conductor portion and the component mounting portion (without reducing the energization allowable current amount), the conductive layer (land) It is possible to improve the amount of heat given for component mounting.

It is a schematic block diagram of the printed circuit board (surface layer) which concerns on 1st embodiment of this invention. It is a top view which shows the printed circuit board (surface layer) which concerns on 1st embodiment of this invention. FIG. 3 is an end view taken along line AA in FIG. 2. It is explanatory drawing which shows the heat conduction of the printed circuit board which concerns on 1st embodiment of this invention. It is a top view which shows the printed circuit board (surface layer) which concerns on 2nd embodiment of this invention. FIG. 6 is an end view taken along line BB in FIG. 5.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
Note that the configuration described below does not limit the present invention and can be variously modified within the scope of the gist of the present invention.
The present embodiment is for a printed circuit board configured as a multilayer substrate, and is intended for a substrate in which a through hole is formed. The conductive layer (land) formed so as to surround the through hole constitutes a thermal land, and a structure for supplying heat to the conductive layer (land) is formed.

1 to 4 show a first embodiment of the present invention. FIG. 1 is a schematic configuration diagram of a printed circuit board (surface layer), FIG. 2 is a top view showing the printed circuit board (surface layer), and FIG. FIG. 4 is an explanatory view showing the heat conduction of the printed circuit board.
5 and 6 show a second embodiment of the present invention. FIG. 5 is a top view showing a printed circuit board (surface layer), and FIG. 6 is an end view taken along the line BB of FIG.

≪First embodiment≫
First, the first embodiment will be described.
The printed circuit board 1 according to the present embodiment will be described with reference to FIGS.
As shown in FIG. 3, the printed circuit board 1 according to the present embodiment is a so-called “multilayer printed circuit board”, and a plurality of wiring layers 2 are laminated to form a single printed circuit board 1. The wiring layer 2 is a plate formed of a material containing copper and having electrical conductivity and thermal conductivity.

In the present embodiment, the wiring layers 2A to 2D are a four-layer body laminated in the thickness direction, between the wiring layers 2A and 2B facing each other in the thickness direction, between the wiring layers 2B and 2C, and between the wiring layers 2C and 2D. Insulating layer 5 is interposed.
In addition, the insulating layer 5 is also formed on the outer surfaces of the wiring layer 2A and the wiring layer 2B so as to cover these outer surfaces, but in order to distinguish them, in this embodiment, the wiring layer 2A is used. The insulating layer 5 formed on the outer surface of the wiring layer 2B is particularly referred to as “surface resist layer 51”, and the other insulating layer 5 is referred to as “interlayer resist layer 52” if necessary. The insulating layer 5 is a film formed of glass fiber and epoxy resin.
Of the insulating layer 5, the “surface resist layer 51” corresponds to the “insulating layer” in the claims.

The printed circuit board 1 is formed with a through hole 3 for inserting an electronic component and soldering and connecting the electronic component. The through-hole 3 is a hole that penetrates in the thickness direction, and is connected to the wiring layer 2A and the wiring layer 2D (that is, one and the other outer layers disposed at the end in the thickness direction) on the inner wall surface. A through-hole conductor portion 3a is provided. In the wiring layer 2A and the wiring layer 2D, a thermal land 4 for suppressing thermal diffusion during soldering is formed around the through hole 3.
Further, a solid pattern is formed around the thermal land 4, and the solid pattern is connected to a ground or a power source.

In the present embodiment, the multilayer printed circuit board 1 is exemplified by a structure composed of four wiring layers 2 (2A to 2D). However, the present invention is not limited to this, and the gist of the present invention. Any number of layers may be used without departing from the above.
The electronic component mounted in the through hole 3 may be any component such as a connector or an electric field capacitor. In the present embodiment, the electronic component is a winding K that constitutes an armature of a fanless brushless motor. The winding K is soldered in a state of passing through the through hole 3.

In the present embodiment, the thermal land 4 is configured to include at least a land 41, an insulating portion 42, and a connecting conductor portion 43 as shown in FIGS. The “land 41” corresponds to the “conductive layer” in the claims.
The land 41 according to the present embodiment is a ring-shaped portion as viewed from above and is formed so as to surround the through hole 3, and is composed of, for example, a conductive member that conducts heat and electricity.
As shown in FIG. 1, the land 41 is a portion for performing soldering in a state where the winding K penetrates the through hole 3.
Although the periphery of the land 41 is the wiring layer 2, in this embodiment, for convenience of explanation, a portion of the wiring layer 2 around the land 41 is referred to as an “outer conductor portion 21”.

Further, the insulating portion 42 according to the present embodiment divides and insulates the land 41 and the outer conductor portion 21 so that the ring is divided into four equal parts along the concentric circumference of the land 41. Is formed. This may be formed, for example, by etching away the surface layer of the outer conductor portion 21 (wiring layer 2).
Further, the connecting conductor portion 43 according to the present embodiment is made of a conductive member that conducts heat and electricity, and is formed so as to connect the land 41 and the outer conductor portion 21 in the radial direction. . In other words, it is formed between the dividing positions of the adjacent insulating portions 42, 42, that is, between them.

In the thermal land 4 configured as described above, the path through which the heat applied to the land 41 is diffused to the outer conductor portion 21 is limited to only the four connecting conductor portions 43 to reduce the heat diffusion to the surroundings. Can be made.
However, in order to further improve the thermal efficiency in the land 41, the preheat land 6 is formed in the present embodiment.
Hereinafter, the preheat land 6 will be described.

The preheat land 6 according to the present embodiment is a portion formed slightly apart from the land 41.
The preheat land 6 is a portion where the surface resist layer 51 is removed and the surface (outer side surface) of the wiring layer 2 (in this embodiment, the wiring layer 2A) is exposed.
Therefore, the preheat land 6 corresponds to a “heat transfer surface” in the claims. More specifically, in the preheat land 6, the surface exposed to the outside after the surface resist layer 51 is removed corresponds to a “heat transfer surface” in the claims.

Since it is configured in this way, as shown in FIG. 4, the heat H <b> 2 applied to the preheat land 6 is conducted from the outer conductor portion 21 → the connecting conductor portion 43 → the land 41.
Therefore, both the heat H1 given from the solder iron and the heat conducted from the heat H2 given to the preheat land 6 are given to the solder.
Therefore, even if the heat H1 is diffused from the connecting conductor portion 43, the heat H2 given to the preheat land 6 is conducted, so that the temperature of the solder is prevented from being lowered, and the soldering on the land 41 is prevented. Thermal efficiency is improved.
As a method of applying the heat H2 to the preheat land 6, any method may be used as long as it does not depart from the spirit of the present invention. Examples include a method of applying warm air to the preheat land 6 and a method of applying a soldering iron.

<< Second Embodiment >>
Next, a second embodiment will be described with reference to FIGS. 5 and 6.
In the second embodiment, the configuration of the preheat land 6 is different from that of the first embodiment. In addition, since structures other than this preheat land 6 are the same as that of the said 1st embodiment, description is abbreviate | omitted.
In order to distinguish from the preheat land 6 described above, this embodiment is referred to as a second preheat land 106.

As shown in FIG. 6, the second preheat land 106 includes a heating unit 161 that is a rectangular plate-like body and a heat conduction medium 162.
The heating unit 161 according to the present embodiment is a rectangular plate formed of the same thermally conductive material as the wiring layer 2.
The heating unit 161 is attached to the outer surface of the surface resist layer 51 formed on the outer surface of the wiring layer 2A. For this reason, unlike the first embodiment, the heating unit 161 and the wiring layer 2 </ b> A are blocked in terms of heat conduction.
The heat conducting medium 162 according to the present embodiment is a conducting wire formed of a heat transfer material.
The heat conduction medium 162 has one end connected to the heating unit 161 and the other end connected to the land 41.

Since it is configured in this manner, the heat H <b> 1 given to the heating unit 161 is transmitted to the land 41 through the heat conductive medium 162. That is, the heating unit 161 is connected in a heat conductive manner by the heat conductive medium 162.
Therefore, in the present embodiment, the outer surface of the heating unit 161 corresponds to a “heat transfer surface” in the claims.

In the present embodiment, the heating unit 161 and the land 41 are indirectly connected by the heat conducting medium 162, but the present invention is not limited to this. For example, the heating unit 161 and the heat conducting medium are integrated. The heating unit 161 and the land 41 may be directly connected.
Further, the heating unit 161 may be configured to penetrate the surface resist 51, and the bottom surface (the surface opposite to the outer surface) of the heating unit 161 may be configured to contact the wiring layer 2A.

In each of the above embodiments, for explaining the functions of the preheat land 6 and the second preheat land 106, the relationship between one preheat land 6 and the second preheat land 106 and one thermal land 4 is illustrated. It is not limited to.
That is, one preheat land 6 and the second preheat land 106 are provided for the plurality of thermal lands 4, and heat is applied to the plurality of thermal lands 4 by the one preheat land 6 and the second preheat land 106. It is good also as a simple structure.

1 .... Printed circuit board, 2 (2A to 2B) ... Wiring layer, 21 ... Outer conductor,
3. ・ Through hole, 3a ・ ・ Through hole conductor part,
4. Thermal land,
41..Land (conductive layer), 42..Insulating part, 43..Connecting conductor part,
5 .. Insulating layer 51.. Surface resist layer 52.. Interlayer resist layer
6. Preheat land (heat transfer surface),
106 .. Second preheat land, 161 .. Heating part, 162 .. Heat conduction medium,
K winding

Claims (5)

A plurality of wiring layers having at least one layer of solid wiring layer, a through hole in which a conductive layer connected to the wiring layer is formed on the peripheral wall surface, and an outer end surface exposed at both ends in the thickness direction And an insulating layer
A printed circuit board, wherein a heat transfer surface that is thermally connected to the conductive layer is formed on at least one of the outer end surfaces.   The printed circuit board according to claim 1, wherein the heat transfer surface is the wiring layer exposed from the insulating layer.   The heat transfer surface is a heat conductive member formed on the outer surface of the insulating layer, and the heat conductive member is directly or indirectly connected to the conductive layer so as to conduct heat. The printed circuit board according to claim 1.   The printed circuit board according to claim 3, wherein the heat conductive member is connected to the conductive layer by a heat conductive wire. The printed circuit board according to claim 1, wherein the conductive layer forms a thermal land.

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