WO2014121878A1

WO2014121878A1 - Circuit board

Info

Publication number: WO2014121878A1
Application number: PCT/EP2013/077489
Authority: WO
Inventors: Jianghui YANG; Peng Chen; Yusheng MING; Haiquan CHEN
Original assignee: Osram GmbH
Current assignee: Osram GmbH
Priority date: 2013-02-05
Filing date: 2013-12-19
Publication date: 2014-08-14
Anticipated expiration: 2015-08-05
Also published as: CN103974598A

Abstract

The present invention relates to a circuit board (10) for an electronic device (100), the circuit board (10) comprising an insulating substrate (1) and a conducting layer (2) arranged at one side of the substrate (1), characterized in that the conducting layer (2) includes an electrode region (21) and at least one heat dissipation region (22) that is separated from the electrode region (21), wherein at least one through hole (23) is opened in the heat dissipation region (22), and at least one electrically isolated heat-conductive structure is provided between the electrode region (21) and the at least one heat dissipation region (22).

Description

Description Circuit Board Technical Field

The present invention relates to a circuit board for an elec^¬ tronic device, in particular a circuit board for an illumi^¬ nating device.

Background Art

With increasingly wide application of electronic devices, in particular illuminating apparatuses relating to LED technology, requirements on such electronic devices in electrical properties are heightened. For example, an illuminating de^¬ vice with an LED as light source has a driver circuit that is particularly configured for LED devices, such an LED driver circuit can be provided on a printed circuit board (PCB tech^¬ nology) , and such a conventional circuit board can provide stable electric energy for the LED driver circuit, in par^¬ ticular for an LED chip controlled by the same. Moreover, as heat dissipation performance of circuit boards is one of principal factors that influence the performances of elec^¬ tronic devices, e.g. luminous efficiency of LED devices, sta^¬ ble and reliable operation of the LED driver circuit can be assured in a situation that the circuit board has good heat dissipation performance. In addition, users pay more and more attention to insulation performance of circuit boards. If it can be assured that the circuit board per se has good heat dissipation performance, and simultaneously has good in^¬ sulation performance with respect to the LED driver circuit printed thereon, electronic devices, for example LED illumi^¬ nating devices, utilizing such a circuit board can run in various situations more stably and reliably. In a solution of the prior art, it is provided that an exist^¬ ing printed circuit board is used, e.g. a circuit board of FR4 or CEM-3, and such a circuit board has a relatively low thermal conductivity, which is about 0.4W/ (m*K) . In order to reduce the thermal resistance of such a circuit board as pos^¬ sible, to increase the thermal conductivity of said circuit board, a plurality of through holes for heat dissipation can be effectively opened on said circuit board. Figure 1 shows a schematic top view of an embodiment of a circuit board 10 according to the prior art. As shown in Figure 1, in said embodiment, the circuit board 10 has a conducting layer 2 for emplacing an electronic device, said conducting layer 2 includes an electrode region 21 which is divided into an anode electrode region and a cathode electrode region, the two electrode regions can be respectively in electrical connec^¬ tion with the positive pin and negative pin of the electronic device, for example of an LED chip. Moreover, in order to reduce the thermal resistance of said circuit board, a plu^¬ rality of through holes 23 is particularly opened in a pe- ripheral region of the conducting layer 2, and said through holes can be distributed in an array.

Figure 2 shows a sectional view of the circuit board as shown in Figure 1. As shown in Figure 2, an LED chip is carried on one side (top surface in the figure) of the circuit board 10, and a conducting layer 2 is arranged between the substrate 1 of the circuit board 10 and the LED chip. It can be identi^¬ fied hereby that the four through holes 23 shown in Figure 1 are respectively symmetrically positioned at both sides of the LED chip, and these through holes 23 penetrate the whole circuit board 10, in other words, successively penetrate the conducting layer 2 and the substrate 1. However, it is dis^¬ advantageous that the through holes 23 opened on the circuit board 10 would form unnecessary electrical connection paths, which would decrease electrical insulation performance of said circuit board. Thus, although said solution can obvi^¬ ously lower the thermal resistance of the circuit board and increase the thermal conductivity, it simultaneously de- creases the electrical insulation strength of the circuit board, which may bring adverse influences for an electronic device having such a circuit board mounted, for example, the stability and reliability of the electronic device during op^¬ eration are decreased. And said disadvantage greatly limits the application range of the circuit board in the prior art.

Summary of the Invention

In order to solve the existing problem in the prior art, the present invention provides a novel circuit board for an elec^¬ tronic device. The circuit board according to the present invention has the characteristic of low thermal resistance, so as to assure a good heat dissipation effect of the circuit board during a working state. In addition, such a circuit board can simultaneously have high insulation strength, so as to advantageously satisfy the requirements of a user on its insulation performance.

An object of the present invention is achieved through a cir^¬ cuit board for an electronic device, viz. said circuit board comprises an insulating substrate and a conducting layer arranged at one side of the substrate, characterized in that the conducting layer includes an electrode region and at least one heat dissipation region that is separated from the electrode region, wherein at least one through hole is opened in the heat dissipation region, and at least one electrically isolated heat-conductive structure is provided between the electrode region and the at least one heat dissipation re^¬ gion. The present invention provides a design for improving the circuit board in the prior art, which divides the elec- trode region and the heat dissipation region of the conduct^¬ ing layer configured as top surface of the circuit board, that are integrally provided according to the prior art, into at least two regions separated from each other, so as to form an electrode region and at least one heat dissipation region that is electrically isolated from the electrode region. In order to enable the circuit board according to the present invention to have a good heat dissipation effect, at least one, probably a plurality of through holes is preferably opened in said heat dissipation region according to actual demands, and the or these through holes can act as typical heat dissipation structure in a circuit board to dissipate heat of the circuit board. At least one electrically iso^¬ lated heat-conductive structure is particularly preferably provided between the electrode region and the at least one heat dissipation region, in order that the circuit board ac^¬ cording to the present invention has a good heat dissipation effect, and simultaneously a good insulation effect. Said heat-conductive structure transfers the heat of the electrode region to the heat dissipation region in a form of "heat- conductive bridge", while the electric charges of the elec^¬ trode region would not be transferred to the heat dissipation region together with the heat. By means of said heat- conductive structure, not only an additional heat dissipation effect is realized, but also a fine electrical isolation ef^¬ fect is represented. Thus, the circuit board according to the present invention provides the possibility of simultane^¬ ously assuring good heat dissipation performance and good in^¬ sulation performance. In a preferable embodiment according to the present inven^¬ tion, the heat-conductive structure is a heat conductor, with both edges respectively overlapped the electrode region and the attributive heat dissipation region. In this case, the heat-conductive structure configured in such a manner, due to its electrical isolation performance, can provide an effec^¬ tive and simple way for heat transfer without detracting the insulation performance, while the electrode region and the heat dissipation region are electrically isolated.

It is preferable that the heat conductor is a ceramic plate. Ceramic has fine heat-conductive performance, and good insu^¬ lation performance. In a situation that the heat conductor is made of a ceramic material in accordance with dimensions of international standard, not only the limited space on the circuit board can be effectively saved, so that the circuit board obtains an advantageous structural layout; the heat conductor can also be enabled to improve the heat dissipation effect of said circuit board without detracting the insula- tion performance of said circuit board. In addition, the heat conductor of such a specification may also be extensively applied to other illuminating devices having enough space, to improve their heat dissipation effect.

It is preferable that the through hole penetrates the sub- strate. An effective and direct heat-conductive path can be formed by opening a through hole on the conducting layer of said circuit board and enabling the same to penetrate the substrate of said circuit board. Such a heat-conductive path improves the heat dissipation effect of said circuit board. Moreover, as there is a safe and reliable insulation distance between the electrode region of the circuit board and the through hole, the electrical insulation effect between elec^¬ trical assemblies mounted on the electrode region and the through hole is achieved. Thus, it is assured that the cir- cuit board per se has good insulation strength, so as to en^¬ sure that the electronic device using said circuit board has a stable working environment. It is preferable that the heat conductor is fixed on the con^¬ ducting layer by SM . Said technology can mount said heat conductor on the conducting layer and firmly fix it on said layer, without affecting the original layout of the circuit board as much as possible. Moreover, the cost and time for manufacturing the whole circuit board can be decreased through said mainstream mounting technique.

It is preferable that a first solder pad is provided at the side of the heat conductor facing to the electrode region, and a second solder pad is provided at the side of the heat conductor facing to the heat dissipation region. Said heat conductor is connected with and fixed on the conducting layer of the circuit board through said first and second solder pads, and acts as an effective way of transferring heat.

Moreover, said design further allows an enough insulation distance to exist between the electrode region and the heat dissipation region.

It is preferable that the ceramic plate is made from any of AI₂O₃ or A1N, or from their mixtures. Aluminum oxide and aluminum nitride have relatively high thermal conductivity and relatively good insulation strength, the thermal conduc^¬ tivity of a heat-conducting plate could therefore be greatly improved, if a ceramic plate made from the two kinds of sub^¬ stances mentioned above or their mixture is used as heat- conducting plate. Such a ceramic plate can transfer heat of the electrode region to the heat dissipation region as much as possible to lower the temperature of a high temperature region (viz. the electrode region) of the circuit board and to achieve a good heat dissipation effect. It is preferable that the electronic device is fixed on the electrode region. The electrode region on said circuit board ^

has a space for mounting and fixing the electronic device, an effective electrical connection is therefore realized by mounting said electronic device at said position, and an ef^¬ fect of providing a good working environment for said elec- tronic device can also be realized through the high heat dis^¬ sipation performance and high insulation performance of said circuit board.

It is preferable that the electrode region includes an anode region and a cathode region that are separated from each other, and the positive and negative pins of the electronic devices are respectively in electrical connection with the anode region and the cathode region. As the conducting layer of said circuit board is divided into the anode region and cathode region separated from each other, a way for direct electrical connection can be provided for the electronic de^¬ vice, and in this case, it is convenient to electrically con^¬ nect the positive and negative pins of the electronic device respectively with the corresponding anode region and cathode region on the circuit board. And such an electrical connec^¬ tion is direct, simple and effective.

It is preferable that the conducting layer includes two heat dissipation regions that are symmetrically located at both sides of the electrode region. The object of improving the heat dissipation effect of said circuit board can be achieved through the arrangement of a plurality of heat dissipation regions. Moreover, as the heat dissipation regions are ar^¬ ranged at both sides of said electrode region, an uniform and overall heat dissipation path can be formed on the circuit board, so as to obtain the effect of an overall heat dissipa- tion on said circuit board to assure a good working environ^¬ ment of said circuit board. It is preferable that the substrate is made of FR4 or CEM-3 base material. Said base material has good flame-retardant effect, and can be adequately adaptive to certain severe ap^¬ plication environments to assure the service life of said circuit board. Moreover, said FR4 or CEM-3 base material is a relative common material, which can not only be widely ap^¬ plied to enhance heat dissipation effect of circuit boards, but also effectively save manufacturing costs of circuit boards . Brief Description of the Drawings

The accompanying drawings constitute a part of the present Description and are used to provide further understanding of the present invention. Such accompanying drawings illustrate the embodiments of the present invention and are used to de- scribe the principles of the present invention together with the Description. In the accompanying drawings the same components are represented by the same reference numbers. As shown in the drawings :

Figure 1 shows a schematic top view of an embodiment of a circuit board according to the prior art;

Figure 2 shows a sectional view of the circuit board as shown in Figure 1 ;

Figure 3 shows a sectional view of an embodiment of a circuit board according to the present invention; and Figure 4 shows a schematic top view of an embodiment of the circuit board according to the present invention.

Detailed Description of the Embodiments

The circuit board 10 for an electronic device 100 according to the present invention comprises an insulating substrate 1 and a conducting layer 2 arranged at one side of the sub^¬ strate 1, characterized in that the conducting layer 2 in^¬ cludes an electrode region 21 and at least one heat dissipa- tion region 22 that is separated from the electrode region 21 , wherein at least one through hole 23 is opened in the heat dissipation region 22, and at least one electrically isolated heat-conductive structure is provided between the electrode region 21 and the at least one heat dissipation re- gion 22.

Figure 3 shows a sectional view of an embodiment of the cir^¬ cuit board 10 according to the present invention. As shown in Figure 3, said circuit board 10 comprises a substrate 1 and a conducting layer 2, which further includes an electrode region 21 and at least one heat dissipation region 22 (there are two heat dissipation regions in the present embodiment) , wherein said electrode region 21 is preferably positioned be^¬ tween the two heat dissipation regions 22, and maintains a certain distance with respect to the two heat dissipation re- gions 22.

Moreover, at least one through hole 23 is opened in the heat dissipation region 22, and at least one heat-conductive structure is arranged between said electrode region 21 and the heat dissipation region 22, while Figure 3 only schemati- cally shows two through holes 23 and two heat-conductive structures configured as heat conductors 3. Said heat con^¬ ductor 3 has the function of electrically isolating the elec^¬ trode region 21 and the heat dissipation region 22 from each other. Thus, the two heat conductors 3 are symmetrically overlapped between the electrode region 21 and the attribu^¬ tive heat dissipation region 22, respectively. Furthermore, said heat conductor 3 can be a ceramic plate made from any one of aluminum oxide (AI₂O3) or aluminum nitride (A1N) or any one of their mixtures. A ceramic plate with said compo^¬ sition has a relatively high thermal conductivity and rela^¬ tively good insulation strength. The use of a ceramic mate- rial to manufacture said heat conductors in accordance with dimensions of international standard can not only effectively save the limited space on the circuit board, so that the cir^¬ cuit board obtains an advantageous physical structural lay^¬ out; but also enable said heat conductors to transfer heat as efficiently as possible without detracting the insulation performance of said circuit board, so as to improve the heat dissipation effect of said circuit board.

Of course, in an unshown embodiment, it is also considerable to select other suitable materials to form the substrate. In addition, more heat dissipation regions may be asymmetrically arranged at one side or both sides of the electrode region according to the demands. And the size and shape of the through holes can also be correspondingly changed according to actual demands . Figure 3 further shows that the through holes 23 penetrating the circuit board 10 are opened in the respective heat dissi^¬ pation regions 22, and said through hole 23 penetrates the conducting layer 2 and the substrate 1 under the conducting layer 2, successively. Moreover, the heat conductors 3 are respectively in fixed connection with the electrode region 21 and the heat dissipation region 22 at both sides in the horizontal direction as shown in the figure by means of a first solder pad 4 and a second solder pad 5. The first solder pad 4 is specifically arranged at the side facing to the elec- trode region 21, and the second solder pad 5 is specifically provided at the side facing to the heat dissipation region 22. Figure 4 shows a schematic top view of an example of the cir^¬ cuit board 10 according to the present invention. Said fig^¬ ure only schematically shows the circuit board. As shown in Figure 4, the substrate of said circuit board 10 utilizes FR4 or CEM-3 base material, and a heat conductor 3 performing in^¬ sulated heat conductance in a form of "heat-conductive bridge" is arranged on the conducting layer 2 of said circuit board 10. Specifically, both edges of said heat conductor 3 are respectively fixed on the electrode region 21 and the heat dissipation region 22 of the conducting layer 2 through SMT (SMT) .

Figure 4 further shows that two heat dissipation regions 22 are provided on said conducting layer 2, which are symmetrically positioned at both sides of the electrode layer 21. The object of improving the heat dissipation effect of the circuit board 10 according to the present invention can be achieved by arranging a plurality of heat dissipation regions 22. Moreover, as the heat dissipation regions are arranged at both sides of said electrode region, heat produced locally on said circuit board can be uniformly and overall trans^¬ ferred to other regions having relative lower temperatures, so as to realize an overall heat dissipation effect of said circuit board and assure a good working environment of said circuit board. In addition, an electronic device 100 can be mounted on the electrode region 21 of said circuit board 10, a simple and easy electrical connection can therefore be realized. Said electrode region 21 further includes an anode region 211 and a cathode region 212, which are separated from each other and with which the positive and negative pins of the electronic device 100 are respectively in electrical connection. Thus, a way of direct electrical connection is provided for the electronic device 100, and it is convenient to electrically connect the positive and negative pins of the electronic de^¬ vice 100 with the corresponding anode region 211 and the cathode region 212 on the circuit board, which electrical connection is direct, simple and effective.

The above is merely preferred embodiments of the present in^¬ vention but not to limit the present invention. For the per^¬ son skilled in the art, the present invention may have vari^¬ ous alterations and changes. Any alterations, equivalent substitutions, improvements, within the spirit and principle of the present invention, should be covered in the protection scope of the present invention.

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List of reference signs

1 substrate

2 conducting layer

3 heat conductor

4 first solder pad

5 second solder pad

10 circuit board

21 electrode region

22 heat dissipation region 23 through hole

100 electronic device

211 anode region

212 cathode region

Claims

Patent claims

1. A circuit board (10) for an electronic device (100), the circuit board (10) comprises an insulating substrate (1) and a conducting layer (2) arranged at one side of the substrate (1), characterized in that the conducting layer (2) includes an electrode region (21) and at least one heat dissipation region (22) that is separated from the electrode region (21), wherein at least one through hole (23) is opened in the heat dissipation region (22), and at least one electrically isolated heat-conductive structure is provided between the electrode region (21) and the at least one heat dissipation region (22) .

2. The circuit board according to Claim 1, characterized in that the heat-conductive structure is a heat conductor (3) with both edges respectively overlapped the elec^¬ trode region (21) and the heat dissipation region (22) for the electrode region.

3. The circuit board according to Claim 2, characterized in that the heat conductor (3) is a ceramic plate.

4. The circuit board according to any one of Claims 1 to 3, characterized in that the through hole (23) penetrates the substrate (1) .

5. The circuit board according to Claim 3, characterized in that the heat conductor (3) is fixed on the conducting layer (2) by SMT .

6. The circuit board according to Claim 5, characterized in that a first solder pad (4) is provided at a side of the heat conductor (3) facing to the electrode region (21), and a second solder pad (5) is provided at a side of the heat conductor (3) facing to the heat dissipation region (22) .

7. The circuit board according to Claim 3, characterized in that the ceramic plate is made from any one of AI₂O₃ or A1N, or their mixtures.

8. The circuit board according to any one of Claims 1 to 3, characterized in that the electronic device (100) is fixed on the electrode region (21) .

9. The circuit board according to Claim 8, characterized in that the electrode region (21) includes an anode region

(211) and a cathode region (212) that are separated from each other, and the positive and negative pins of the electronic device are respectively in electrical connec^¬ tion with the anode region (211) and the cathode region

(212) .

10. The circuit board according to any one of Claims 1 to 3, characterized in that the conducting layer (2) includes two heat dissipation regions (22) that are symmetrically located at both sides of the electrode region (21) .

11. The circuit board according to any one of Claims 1 to 3, characterized in that the substrate (1) is made of FR4 or CEM-3 base material.