CN107122012B - Power transmission device and manufacturing method thereof - Google Patents

Abstract

The invention provides a power transmission device and a manufacturing method thereof. The power transmission device includes a first circuit board, a conductive base, a connecting component, a second circuit board and a fixing component. The conductive base is fixed on the first circuit board. The connecting element is arranged on the conductive base. The second circuit board is fixed on the connecting component. The fixing component is disposed on the second circuit board and connected to the conductive base through the second circuit board and the connecting component. The first circuit board is electrically connected to the second circuit board via the conductive base and the connecting element.

Description

Power transmission device and manufacturing method thereof

Technical field

The present invention mainly relates to a power transmission device, and in particular, to a power transmission device for computer equipment.

Background technique

Most computer equipment that consumes a large amount of power, such as network servers, is equipped with a power transmission device to transmit and supply the power supplied by the power supply device to the motherboard.

Since there are many electronic components on the power transmission device for voltage stabilization and power management, in order to properly utilize the internal space of the computer equipment. As shown in FIG. 1 , the electronic components P30 of the power transmission device P1 are generally disposed on two circuit boards P10 and P20 that are stacked on each other. In addition, since the amount of current passing through the power transmission device P1 is relatively large, it is also convenient to install the electronic components P30 on different circuit boards P10 and P20.

In the traditional technology, the power transmission device P1 uses the copper pillar P40 to support the upper circuit board P20 and space the two circuit boards P10 and P20 from each other. In addition, the power transmission device P1 uses two electrical connectors P50 to be respectively disposed on the circuit boards P10 and P20, and uses a wire P60 to connect the two electrical connectors P50.

However, although the current power transmission device meets the purpose of its use, it has not yet met many other requirements. Therefore, there is a need to provide an improved solution for the power transmission device that can reduce the manufacturing cost of the power transmission device.

Contents of the invention

An object of the present invention is to improve the power transmission device and reduce the manufacturing cost of the power transmission device;

Another object of the present invention is to provide a method for manufacturing a power transmission device with low manufacturing cost.

The invention provides a power transmission device, which includes a first circuit board, a conductive base, a connecting component, a second circuit board and a fixing component. The conductive base is fixed on the first circuit board. The connecting element is arranged on the conductive base. The second circuit board is fixed on the connecting component. The fixing component is disposed on the second circuit board and connected to the conductive base through the second circuit board and the connecting component. The first circuit board is electrically connected to the second circuit board via the conductive base and the connecting element.

The invention provides a power transmission device, which includes a first circuit board, a first conductive base, a second circuit board, a second conductive base, a connecting element, a first fixing element and a second fixing element. . The first conductive seat is fixed on the first circuit board. The second circuit board is located above the first circuit board. The second conductive seat is fixed on the second circuit board.

The connecting element connects the first conductive base and the second conductive base. The first fixing element passes through the connecting element and is connected to the first conductive base. The second fixing element passes through the connecting element and is connected to the second conductive base. The first circuit board is electrically connected to the second circuit board through the first conductive base, the connecting element and the second conductive base.

In some embodiments, the power transmission device further includes a conductive material, and the second circuit board further includes a conductive layer, wherein the conductive material is disposed on the conductive layer, and the connecting element is connected to the conductive layer through the conductive material.

In some embodiments, the fixing element is conductive and is in direct contact with and electrically connected to the conductive base, the connecting element and the second circuit board.

In some embodiments, the power transmission device further includes a first connector and a second connector. The first connector is provided on the first circuit board and is used to connect a power supply device. The second connector is provided on the second circuit board and is used to connect to a motherboard.

The invention provides a method for manufacturing a power transmission device, which includes fixing a conductive base to a first circuit board; coating a conductive material on a conductive layer of a second circuit board and adjacent to a second circuit board a conductive hole; setting a connecting element in the conductive material, and the connecting element is fixed to the second circuit board through the conductive material; placing the connecting element on the conductive base; inserting a fixing element through the second circuit board, the connecting element, and connecting to the conductive base, to fix the second circuit board to the first circuit board. The first circuit board is electrically connected to the second circuit board via the conductive base and the connecting element.

In some embodiments, the manufacturing method of the power transmission device further includes fixing a first connector and a first electronic component to the first circuit board; and fixing a second connector and a second electronic component to the second circuit board. circuit board.

To sum up, the power transmission device of the present invention uses a conductive base, a connecting element and a fixing element to electrically connect two circuit boards, and to support the upper circuit board. Therefore, it can replace the electrical circuit used to electrically connect two circuit boards in the traditional technology. Connectors can also replace or reduce copper pillars in traditional technology, thereby reducing the manufacturing cost of power transmission devices.

Description of drawings

Figure 1 is a schematic diagram of a conventional power transmission device.

Figure 2 is a perspective view of the computer equipment of the present invention.

FIG. 3 is a perspective view of the first embodiment of the power transmission device of the present invention.

FIG. 4 is an exploded view of the first embodiment of the power transmission device of the present invention.

5 is a cross-sectional view of the first embodiment of the power transmission device of the present invention.

FIG. 6 is a flow chart of the manufacturing method of the power transmission device of the present invention.

FIG. 7 is a schematic diagram of the manufacturing method of the power transmission device of the present invention at an intermediate stage of the manufacturing process.

8 is a perspective view of a second embodiment of the power transmission device of the present invention.

FIG. 9 is an exploded view of the second embodiment of the power transmission device of the present invention.

FIG. 10 is a cross-sectional view of a second embodiment of the power transmission device of the present invention.

Among them, the reference symbols are explained as follows:

First circuit board 10

upper surface 11

Jack 12

Second circuit board 20

upper surface 21

lower surface 22

Conductive via 23

Conductive layer 24

Piercings 25

Conductive seat 30, 30a, 30b

Conductive body 31

Conductive top surface 331

Fixing hole 332

Pin 32

Connecting elements 40

Connect the body 41

Connect top 411

Connect base 412

Nose 42

Connection hole 43

First connection part 44

Second connection part 45

Central connection 46

Fixing elements 50, 50a, 50b

Screw head 51

screw 52

Computer Equipment A1

Chassis A10

Motherboard A20

Main electronics A30

Power supply unit A40

Power transmission unit A50

First connector B10

First Electronic Components B20

Second connector B30

Second electronic component B40

Arrangement direction D1

Conductive material M1

Power transmission device P1

Circuit board P10, P20

Electronic components P30

Copper Pillar P40

Electrical Connector P50

Wire P60

Detailed ways

The following description provides many different embodiments, or examples, for implementing various features of the invention. The components and arrangements described in the following specific examples are only used to concisely express the present invention. They are only used as examples and are not intended to limit the present invention. For example, description of a first feature on or above a second feature includes direct contact between the first and second features, or another feature disposed between the first and second features such that the second feature The first and second characteristics are not in direct contact.

In addition, the same component numbers and/or words are used in different examples in this specification. The foregoing is only used for simplicity and clarity, and does not mean that there is necessarily a relationship between different embodiments and settings.

The first and second terms in this specification are only used for the purpose of clear explanation and are not used to correspond to or limit the scope of the patent. In addition, terms such as first characteristic and second characteristic are not limited to the same or different characteristics.

The shapes, sizes, thicknesses and angles of inclination in the drawings may not be drawn to scale or may be simplified for the purpose of clear illustration and are provided for illustration only.

FIG. 2 is a perspective view of the computer device A1 of the present invention. The computer device A1 may be a server, such as a web server. The computer equipment A1 includes a chassis A10, a motherboard A20, a plurality of main electronic components A30, a power supply device A40 and a power transmission device A50. The motherboard A20 is installed in the chassis A10. The main electronic component A30 is disposed on the motherboard A20. The main electronic component A30 may include a central processing unit, a display chip, a memory, etc.

The power supply device A40 is used to supply power to the power transmission device A50. The power supply device A40 can be used to convert alternating current power into direct current power, and supply the direct current power to the power transmission device A50. The power transmission device A50 is connected to the motherboard A20 and the power supply device A40.

The power transmission device A50 is used to transmit the power transmitted by the power supply device A40 and transmit it to the motherboard A20. In some embodiments of Power over Ethernet (PoE) network power supply switch equipment, the power transmission device A50 can stabilize, reduce the voltage and reduce the current amount of the power provided by the power supply device A40, and then transmit the power to the motherboard. A20.

In some embodiments, power supply device A40 supplies 12V and 60A. The power transmission device A50 reduces the voltage of 12V to 5V, and outputs multiple sets of currents to the motherboard A20 respectively, thereby respectively supplying appropriate power to the main electronic component A30.

FIG. 3 is a perspective view of the first implementation of the power transmission device A50 of the present invention. FIG. 4 is an exploded view of the first implementation of the power transmission device A50 of the present invention. FIG. 5 is a cross-sectional view of the first embodiment of the power transmission device A50 of the present invention. The power transmission device A50 includes a first circuit board 10 , a second circuit board 20 , two conductive seats 30 , two connecting components 40 and two fixing components 50 .

The first circuit board 10 and the second circuit board 20 are spaced apart from each other. In this embodiment, the first circuit board 10 and the second circuit board 20 are substantially parallel to each other. The first circuit board 10, the conductive base 30, the connecting components 40 and the fixing components 50 are arranged in an arrangement direction D1.

In this embodiment, the power transmission device A50 further includes a first connector B10, a plurality of first electronic components B20, a second connector B30, and a plurality of second electronic components B40. The first connector B10 and the first electronic component B20 are disposed on an upper surface 11 of the first circuit board 10 . In this embodiment, the first connector B10 and the first electronic component B20 are directly fixed and electrically connected to the first circuit board 10 . The first connector B10 is electrically connected to the first electronic component B20 via the first circuit board 10 .

The first connector B10 is used to connect the power supply device A40 in FIG. 2 . In other words, the power generated by the power supply device A40 is transmitted to the first circuit board 10 via the first connector B10. For example, the first electronic component B20 may be a voltage stabilizing component, an overcurrent protection component, a resistor, a capacitor, etc.

In this embodiment, the conductive base 30, the connecting element 40 and/or the fixing element 50 respectively form two electrode structures, wherein one of the two electrode structures is a positive electrode structure and the other is a negative electrode structure.

The second circuit board 20 is electrically connected to the first circuit board 10 through the above-mentioned electrode structure (conductive seat 30, connecting element 40 and/or fixing element 50). In other words, the power supplied by the power supply device A40 is processed by the first electronic component B20 and then transmitted to the second circuit board 20 through the above-mentioned electrode structure.

In this embodiment, the above-mentioned electrode structure is used to replace the higher-cost electrical connector in the traditional technology to electrically connect the first circuit board 10 and the second circuit board 20 , thereby reducing the manufacturing cost of the power transmission device.

The second connector B30 and the second electronic component B40 are disposed on an upper surface 21 of the second circuit board 20 . In this embodiment, the second connector B30 and the second electronic component B40 are directly fixed and electrically connected to the second circuit board 20 . The second electronic component B40 is electrically connected to the above-mentioned electrode structure through the second circuit board 20 .

The conductive base 30 is fixed on the first circuit board 10 . The conductive base 30 is conductive and made of conductive material, and is electrically connected to the first circuit board 10 . In this embodiment, the conductive base 30 is a power terminal, and the two conductive bases 30 are respectively a positive conductive terminal and a negative conductive terminal.

The conductive base 30 includes a conductive body 31 and a plurality of pins 32 . The conductive body 31 has a conductive top surface 331 and a fixing hole 332 . In this embodiment, the conductive top surface 331 is a plane and can be substantially parallel to the first printed circuit board. The conductive top surface 331 is spaced apart from the upper surface 11 . The fixing hole 332 is formed in the center of the conductive top surface 331 .

The pins 32 are connected to the conductive body 31 and are integrally formed with the conductive body 31 . The pin 32 is inserted into the jack 12 of the first circuit board 10 and is electrically connected to the first circuit board 10 . The jack 12 is formed on the upper surface 11 of the first circuit board 10 . In this embodiment, the pins 32 are soldered to the first printed circuit board, so that the conductive base 30 is fixed to the upper surface 11 of the first circuit board 10 .

The connecting element 40 is fixed on the second circuit board 20 and is disposed on the conductive base 30 . The connecting element 40 is conductive and made of conductive material. The connecting element 40 is electrically connected to the second circuit board 20 . In this embodiment, the connecting component 40 may be a surface-mounted device nut (SMD nut).

The connecting element 40 includes a connecting body 41 and a protruding portion 42 . The connecting body 41 can be a plate-shaped structure and has a connecting top surface 411 and a connecting bottom surface 412 . The above-mentioned connection top surface 411 is relative to the connection bottom surface 412. The protruding portion 42 is provided at the center of the connecting top surface 411 . The connecting body 41 also includes a connecting hole 43 that penetrates the center of the connecting body 41 and the protruding portion 42 .

In this embodiment, the connecting top surface 411 is substantially parallel to the connecting bottom surface 412, and both the connecting top surface 411 and the connecting bottom surface 412 are planar. Connection bottom surface 412 contacts conductive top surface 331 . Since the connection bottom surface 412 and the conductive top surface 331 are both flat, there is a good electrical connection between the connection element 40 and the conductive base 30 .

The connecting top surface 411 of the connecting element 40 contacts the lower surface 22 of the second circuit board 20 , and the protruding portion 42 is located in a conductive hole 23 of the second circuit board 20 . In this embodiment, the lower surface 22 faces the upper surface 11 of the first circuit board 10 .

In this embodiment, the second circuit board 20 further includes a conductive layer 24 located on the lower surface 22 of the second circuit board 20 . In some embodiments, the conductive layer 24 is also located on the sidewall and/or the upper surface 21 of the conductive hole 23 .

In this embodiment, there is a conductive material M1 between the connecting element 40 and the second circuit board 20 . In other words, the conductive material M1 is disposed between the connecting element 40 and the second circuit board 20 . The connection element 40 is connected to the conductive layer 24 via the conductive material M1.

The fixing component 50 is disposed on the second circuit board 20 and passes through the second circuit board 20 and the connecting component 40 before being connected to the conductive base 30 . In some embodiments, the fixing component 50 is conductive and directly contacts and electrically connected to the conductive base 30 , the connecting component 40 and the second circuit board 20 . In some embodiments, the fixation element 50 is insulating.

In this embodiment, the fixing component 50 is a screw, which is locked on the conductive base 30 . The fixing component 50 has a screw head 51 and a screw rod 52 . The screw head 51 is connected to the screw rod 52 and is integrally formed with the screw rod 52 . The screw head 51 is connected to the upper surface 21 of the second circuit board 20 . The screw rod 52 passes through the conductive hole 23 and the connecting hole 43 to reach the fixing hole 332. As shown in FIG. 5 , one end of the screw rod 52 is locked in the fixing hole 332 of the conductive base 30 .

In this embodiment, since the conductive base 30 is fixed on the first circuit board 10 and the connecting element 40 is fixed on the second circuit board 20, when assembling the power transmission device A50, the connecting element 40 can be placed on the conductive base first. On the base 30, the fixing component 50 is then passed through the second circuit board 20 and the connecting component 40 and then locked or fixed to the conductive base 30, so that the assembly can be easily completed.

When the power transmission device A50 is disassembled, the fixing component 50 can be removed and the first circuit board 10 and the second circuit board 20 can be easily separated. Since the conductive layer 24 and the conductive material M1 on the lower surface 22 of the second circuit board 20 will not be worn when the power transmission device A50 is assembled or disassembled, the service life of the power transmission device A50 can be increased.

In this embodiment, the electrode structure (the conductive base 30, the connecting element 40 and the fixing element 50) is made of rigid materials such as metal. The electrode structure can firmly support the second circuit board 20 and connect the first circuit board 10 to the second circuit board 20. The two circuit boards 20 are spaced apart from each other. Therefore, the electrode structure can replace or reduce the copper pillars in the traditional technology, thereby reducing the manufacturing cost of the power transmission device.

FIG. 6 is a flow chart of the manufacturing method of the power transmission device A50 of the present invention. FIG. 7 is a schematic diagram of the manufacturing method of the power transmission device A50 of the present invention at an intermediate stage of the manufacturing process. It can be understood that in each step of the methods of the following embodiments, additional steps may be added before, after, and during each step, and some of the foregoing steps may be replaced, deleted, or moved.

In step S101 , the first connector B10 , the first electronic component B20 and the conductive base 30 are fixed to the first circuit board 10 . In step S103 , as shown in FIG. 7 , the conductive material M1 is coated on the conductive layer 24 of the second circuit board 20 and adjacent to the conductive hole 23 . At this time, the conductive material M1 is in a paste, molten or liquid state.

In this embodiment, the conductive layer 24 can be a copper foil layer, and the conductive material M1 can be solder paste or conductive glue. By covering the conductive layer 24 with the conductive material M1, there is no need to plate precious metals such as gold or silver on the conductive layer 24 to avoid oxidation of the conductive layer 24, thereby reducing the manufacturing cost of the power transmission device A50.

In step S105, before the conductive material M1 in a paste, molten or liquid state is solidified, the connecting element 40 is disposed on the conductive material M1 (as shown in FIG. 5). Since the conductive material M1 is in a paste, molten or liquid state at this time, the conductive material M1 can be well connected to the connecting element 40 and the conductive layer 24 of the second circuit board 20 .

After the conductive material M1 is solidified, the connecting element 40 is fixed to the second circuit board 20 through the solidified conductive material M1. In this embodiment, the second circuit board 20 can be left for a period of time, such as one minute, to allow the conductive material M1 to solidify.

Afterwards, the second connector and the second electronic component B40 can be fixed on the second circuit board 20 . The step of fixing the second connector and the second electronic component B40 to the second circuit board 20 may also be performed before step S103.

In step S107 , the connection component 40 is placed on the conductive base 30 . In step S109 , the fixing component 50 penetrates the second circuit board 20 , the connecting component 40 , and is connected to the conductive base 30 to fix the second circuit board 20 to the first circuit board 10 .

FIG. 8 is a perspective view of the second implementation of the power transmission device A50 of the present invention. FIG. 9 is an exploded view of the second embodiment of the power transmission device A50 of the present invention. FIG. 10 is a cross-sectional view of the second embodiment of the power transmission device A50 of the present invention.

The conductive seat 30 includes a plurality of conductive seats 30a and a plurality of conductive seats 30b. The conductive base 30a is fixed on the first circuit board 10. The conductive base 30b is fixed on the second circuit board 20 . The second circuit board 20 is located above the first circuit board 10 . The second circuit board 20 has a through hole 25 adjacent to the conductive base 30b.

The connecting element 40 connects the conductive base 30a and the conductive base 30b. The first circuit board 10 is electrically connected to the second circuit board 20 through the conductive seat 30a, the connecting element 40, and the conductive seat 30b. In this embodiment, the connecting element 40 has a Z-shaped structure. The connecting element 40 passes through the through hole 25 of the second circuit board 20 , and the conductive base 30 a is located below the through hole 25 .

In this embodiment, the connecting element 40 has a first connecting part 44 , a second connecting part 45 and a central connecting part 46 . The first connection part 44 is connected to the conductive top surface 331 of the conductive seat 30a, the second connection part 45 is connected to the conductive top surface 331 of the conductive seat 30b, and the central connection part 46 is connected to the first connection part 44 and the second connection part 45. The central connecting portion 46 passes through the perforation 25 .

The fixing element 50 includes a fixing element 50a and a fixing element 50b. The fixing element 50a passes through the first connecting portion 44 of the connecting element 40 and is connected to the conductive base 30a. The fixing element 50b passes through the second connecting portion 45 of the connecting element 40 and is connected to the conductive base 30b.

In this embodiment, the fixing element 50a is a screw, which is locked on the conductive base 30a, and the fixing element 50b is a screw, which is locked on the conductive base 30b.

In this embodiment, the fixing element 50a and the fixing element 50b are conductive. The fixing element 50a is in direct contact with and electrically connected to the conductive base 30a and the connecting element 40, and the fixing element 50b is in direct contact with and electrically connected to the conductive base 30b and the connecting element 40.

In this embodiment, the lengths of the first connection part 44 , the second connection part 45 and/or the central connection part 46 can be changed to accommodate the first circuit board 10 and the second circuit board 20 of different designs. In other words, the relative position between the conductive base 30 a and the conductive base 30 b can be adjusted according to the design of the first circuit board 10 and the second circuit board 20 . For example, in some embodiments, the conductive seat 30a may not be located below the through hole 25.

To sum up, the power transmission device of the present invention uses a conductive base, a connecting element and a fixing element to electrically connect two circuit boards, and to support the upper circuit board. Therefore, it can replace the electrical circuit used to electrically connect two circuit boards in the traditional technology. Connectors can also replace or reduce copper pillars in traditional technology, thereby reducing the manufacturing cost of power transmission devices.

The above disclosed features can be combined, modified, replaced or adapted with one or more disclosed embodiments in any appropriate manner and are not limited to specific embodiments.

Although the present invention is disclosed above in various embodiments, these are only examples and are not used to limit the scope of the present invention. Anyone skilled in the art can make some modifications without departing from the spirit and scope of the present invention. Changes and embellishments. Therefore, the above embodiments are not intended to limit the scope of the present invention. The scope of protection of the present invention shall be determined by the scope of the appended claims.

Claims (16)

1. A power transmission device, comprising: a first circuit board, the first circuit board has an upper surface and a lower surface; a conductive base fixed on the upper surface of the first circuit board; a second circuit board, the second circuit board has an upper surface and a lower surface, the upper surface is relative to the lower surface, and the lower surface of the second circuit board faces the upper surface of the first circuit board; A connecting element, the connecting element is disposed between the lower surface of the second circuit board and the conductive base, and is fixed on the lower surface of the second circuit board; and A fixing component is disposed on the upper surface of the second circuit board and connected to the conductive base through the second circuit board and the connecting component, The first circuit board is electrically connected to the second circuit board via the conductive base and the connecting element. 2. The power transmission device of claim 1, further comprising a conductive material, and the second circuit board further comprising a conductive layer, wherein the conductive material is disposed on the conductive layer, and the connection element is connected to the conductive layer through the conductive material. The conductive layer is connected. 3. The power transmission device of claim 2, wherein the conductive layer comprises a copper foil layer. 4. The power transmission device of claim 1, wherein the fixing element is a screw, and the screw is locked to the conductive base. 5. The power transmission device of claim 1, wherein the fixing element is conductive and directly contacts and electrically connected to the conductive base, the connecting element and the second circuit board. 6. A method of making a power transmission device, including: fixing a conductive base to a first circuit board; Coating a conductive material on a conductive layer of a second circuit board and adjacent to a conductive hole of a second circuit board; A connecting element is provided on the conductive material, and the connecting element is fixed to the second circuit board through the conductive material; placing the connection component on the conductive base; and A fixing element penetrates the second circuit board, the connecting element, and is connected to the conductive base to fix the second circuit board to the first circuit board, The first circuit board is electrically connected to the second circuit board via the conductive base and the connecting element. 7. The method of manufacturing a power transmission device as claimed in claim 6, wherein the conductive layer is a copper foil layer. 8. The method of manufacturing a power transmission device as claimed in claim 6, wherein the fixing element is a screw locked to the conductive base. 9. The method of manufacturing a power transmission device as claimed in claim 6, wherein the fixing element is made of conductive material and is directly in contact with and electrically connected to the conductive base, the connecting element and the second circuit board. 10. The method of manufacturing a power transmission device according to claim 6, further comprising: fixing a first connector and a first electronic component to the first circuit board; and A second connector and a second electronic component are fixed to the second circuit board. 11. A power transmission device, comprising: a first circuit board, the first circuit board has an upper surface and a lower surface; a first conductive base fixed on the upper surface of the first circuit board; A second circuit board is located above the first circuit board, the second circuit board has an upper surface and a lower surface, and the lower surface of the second circuit board faces the upper surface of the first circuit board; a second conductive base fixed on the upper surface of the second circuit board; a connecting element connecting the first conductive base and the second conductive base, wherein the portion of the connecting element connected to the first conductive base is disposed between the lower surface of the second circuit board and the first conductive base; A first fixing element passes through the connecting element and is connected to the first conductive base; and A second fixing element passes through the connecting element and is connected to the second conductive base, The first circuit board is electrically connected to the second circuit board via the first conductive base, the connecting element, and the second conductive base. 12. The power transmission device of claim 11, wherein the first fixing element is a screw locked to the first conductive base, and the second fixing element is a screw locked to the second conductive base . 13. The power transmission device of claim 11, wherein the first fixing element and the second fixing element are conductive, and the first fixing element is in direct contact with and electrically connected to the first conductive base and the connection component, and the second fixing component is directly in contact with and electrically connected to the second conductive base and the connecting component. 14. The power transmission device of claim 11, wherein the second circuit board has a through hole adjacent to the second conductive base, and the connecting element passes through the through hole. 15. The power transmission device of claim 11, wherein the connecting element has a first connecting portion connected to the first conductive base, a second connecting portion connected to the second conductive base, and a second connecting portion connected to the second conductive base. A connecting part and a central connecting part of the second connecting part, wherein the second circuit board has a through hole, and the central connecting part passes through the through hole. 16. The power transmission device as claimed in claim 11, wherein the connecting element has a Z-shaped structure.