High power density PCB stator winding, micro axial flux motor and micro fan

Abstract

The utility model discloses a high power density PCB stator winding, micro axial flux motor and micro fan, including the circular composite PCB coil board, it has the first to eighth layer of upper and lower in turn superposed, each layer has the center through -hole and the U1 coil area, V1 coil area, W1 coil area, U2 coil area, V2 coil area, W2 coil area that are arranged along the circumference around the center through -hole, and the outer periphery of each layer is equipped with U1 land area, U2 land area, V1 land area, V2 land area, W1 land area and W2 land area between the corresponding adjacent coil area, and the corresponding area of each layer is set up to be opposite to each other, ensure that the coil of upper and lower layers is not affected by the cross line in axial alignment, make the coil not affected by the cross line, and the adjacent coil is close to symmetry, realize the magnetic field uniformity to reduce the fluctuation of electromagnetic torque, and six land areas and corresponding coil area directly butt joint, need not to go around the wire, and the end ineffective wire length is shortened, make motor or micro fan more compact and light and thin.

Description

Technical Field

[0001] This utility model relates to the stator technology of micro single-rotor single-stator axial flux motor, and in particular to a high power density PCB stator winding, micro axial flux motor and micro fan. Background Technology

[0002] As smart devices such as laptops, tablets, and mobile phones rapidly upgrade towards ultra-thin and lightweight designs, the installation space for their internal heat dissipation core components—microfans—has been compressed to the millimeter level. Simultaneously, the requirements for motor starting reliability, power density, and operational stability have significantly increased. PCB stator windings, due to their advantages of compact structure, no core losses, and high wiring precision, have become the mainstream technology for microfans.

[0003] Currently, the PCB stator winding technology used in the micro fan industry can be roughly divided into three types: single-phase PCB stator winding, three-phase distributed stator winding, and multi-pad three-phase distributed stator winding. Single-phase PCB stator winding: For example, in patent announcement CN200910136676.2, a micro fan has a single-phase PCB stator winding structure. Because the PCB stator is a non-circular structure, it can only be embedded in the base. Once it protrudes from the base, it will interfere with the rotor. Furthermore, this design lacks a back iron (magnetic component), so it cannot hold the fan blades, and the fan blades can easily fall out. Then, when one coil generates the N pole, its adjacent coil will generate the S pole. Thus, the magnetic pole distribution generated by the six coils in the circumferential direction is NSNSNS. This is a standard single-phase PCB motor winding scheme. That is to say, the number of coils in this winding is the same as the number of magnetic poles. Since there is no back iron, the rotor of this fan can stay in any position. When the geometric center of the magnetic pole of the fan blade is completely aligned with the geometric center of the coil, this point becomes a true dead point. At the true dead point, the torque generated by the motor is zero, and the fan cannot start. In addition, the coil area, through holes, and pads are not coordinated in layout. The through holes are randomly arranged in the effective area of ​​the coil, forcing the copper foil spacing to increase. Three-phase distributed stator windings: such as the high power density winding structure and axial magnetic field motor described in patent publication number CN201420624241.9, the PCB stator is also a non-circular structure, which can only be embedded in the base. Once it protrudes from the base, it will interfere with the rotor. Secondly, this three-phase PCB stator winding consists of three single-phase stator windings. The number of coils and the number of magnetic poles in each single-phase stator winding are equal. This is a typical single-phase motor winding. By connecting the three single-phase motor windings in parallel and arranging their phases reasonably, the solution is achieved. The problem is that it produces the effect of a three-phase motor. Although it is still a three-phase motor, it can be divided into three unit motors, each of which is a 6-slot, 6-pole single-phase motor. However, these three motors share a single rotor. During operation, the current fluctuations of each single-phase unit are easily superimposed, affecting the stability of the fan. In addition, the disordered single-coil area between layers is only configured with 5 wire holes (adapted to 6-layer boards), and the inter-layer connection path is random (such as jumping directly from the first layer to the fifth layer). It is necessary to reserve a clearance channel, further compressing the effective winding space. Multi-pad three-phase distributed stator winding: CN201910362391.4 A stator structure of a multi-combination adjustable PCB concentrated winding. In this PCB stator, only a portion of each layer of winding is used to house the winding. For a single-layer coil, the area utilization rate is relatively low. In addition, the space occupied at its end can only be used to connect ineffective conductors, which is a waste of space. The number of pads is as high as 24. In the interior of a micro fan, due to limited space, the fewer the number of pads, the better. 24 pads, too many pads, cause the wires to frequently bypass and interfere, making it impossible to achieve effective wiring.

[0004] Therefore, a new technical solution needs to be researched to address the above problems. Utility Model Content

[0005] In view of this, the present invention addresses the deficiencies of existing technologies, and its main objective is to provide a high-power-density PCB stator winding, a miniature axial flux motor, and a miniature fan. Each layer has U1, V1, W1, U2, V2, and W2 coil areas arranged circumferentially around a central through-hole. U1, U2, V1, V2, W1, and W2 pad areas are provided between adjacent coil areas on the outer periphery of each layer. Furthermore, the corresponding areas of each layer are vertically aligned, ensuring that coils in the upper and lower layers, unaffected by cross-wires, are axially aligned. This results in near-symmetrical adjacent coils, achieving a uniform magnetic field and reducing electromagnetic torque fluctuations. The six pads directly connect to the corresponding coil areas, eliminating the need for winding wires and shortening the length of ineffective end wires. The overall diameter of the PCB stator can be reduced, perfectly fitting the installation space of the miniature fan and solving the problem of difficult wiring with multiple pads in traditional designs. Secondly, the U1 spiral coil group is connected to the U2 spiral coil group via a crossover wire on the sixth layer, the V1 spiral coil group is connected to the V2 spiral coil group via a crossover wire on the seventh layer, and the W1 spiral coil group is connected to the W2 spiral coil group via a crossover wire on the eighth layer. The spiral coil design has a longer straight segment than the coils that are not affected by the crossover wires, in order to compensate for the resistance value and achieve resistance balance between the two types of coils, avoiding phase current fluctuations. Furthermore, the crossover wires are connected to the same phase coil areas in a layered manner, avoiding electromagnetic coupling interference between crossover wires of different phases, thereby further improving motor efficiency and solving the efficiency loss problem caused by traditional crossover wire interference.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: A high power density PCB stator winding includes a circular composite PCB coil board having first to eighth layers stacked sequentially. Each layer has a central through hole and U1 coil area, V1 coil area, W1 coil area, U2 coil area, V2 coil area, and W2 coil area arranged circumferentially around the central through hole. U1 pad area, U2 pad area, V1 pad area, V2 pad area, W1 pad area, and W2 pad area are provided between adjacent coil areas on the outer periphery of each layer, and the corresponding areas of each layer are arranged vertically opposite each other. Helical coil groups are provided in the U1 coil region, V1 coil region, W1 coil region, U2 coil region, V2 coil region, and W2 coil region. An inner wire-passing hole and an outer wire-passing hole are provided at the center of the inner ring of the helical coil group. The inner ring center and the outer wire-passing hole of each layer are arranged vertically opposite each other.

[0007] As a preferred embodiment, the U1 coil area is provided with a U1 spiral coil group and a fourth wire-passing hole, a fifth wire-passing hole, a sixth wire-passing hole, and a seventh wire-passing hole located at the center of the inner ring of the U1 spiral coil group, as well as a first wire-passing hole, a second wire-passing hole, and a third wire-passing hole located on the outer periphery of the U1 spiral coil group; The V1 coil area is provided with a V1 spiral coil group and eleventh, twelfth, thirteenth and fourteenth wire holes located at the center of the inner ring of the V1 spiral coil group, as well as eighth, ninth and tenth wire holes located on the outer periphery of the V1 spiral coil group. The W1 coil area is provided with a W1 spiral coil group and eighteenth, nineteenth, twentieth, and twenty-first wire passing holes located at the center of the inner ring of the W1 spiral coil group, as well as fifteenth, sixteenth, and seventeenth wire passing holes located on the outer periphery of the W1 spiral coil group. The U2 coil area is provided with a U2 spiral coil group and a 25th, 26th, 27th and 28th wire through hole located at the center of the inner ring of the U2 spiral coil group, as well as a 22nd, 23rd and 24th wire through hole located on the outer periphery of the U2 spiral coil group. The V2 coil area is provided with a V2 spiral coil group and a 32nd, 33rd, 34th and 35th wire through hole located at the center of the inner ring of the V2 spiral coil group, as well as a 29th, 30th and 31st wire through hole located on the outer periphery of the V2 spiral coil group. The W2 coil area is provided with a W2 spiral coil group and a 39th, 40th, 41st and 42nd wire passing hole located at the center of the inner ring of the W2 spiral coil group, as well as a 36th, 37th and 38th wire passing hole located on the outer periphery of the W2 spiral coil group.

[0008] As a preferred embodiment, the series logic of the U1 coil region and the U2 coil region in layers one through eight is as follows: The following connections are made sequentially: the U1 pad area of ​​the fourth layer, the U1 spiral coil group of the fourth layer, the fourth via hole, the U1 spiral coil group of the second layer, the first via hole, the U1 spiral coil group of the first layer, the fifth via hole, the U1 spiral coil group of the third layer, the second via hole, the U1 spiral coil group of the fifth layer, the sixth via hole, the U1 spiral coil group of the eighth layer, the third via hole, the U1 spiral coil group of the seventh layer, the seventh via hole, the U1 spiral coil group of the sixth layer, the U2 spiral coil group of the sixth layer, the twenty-fifth via hole, the U2 spiral coil group of the seventh layer, the twenty-fourth via hole, the U2 spiral coil group of the eighth layer, the twenty-sixth via hole, the U2 spiral coil group of the fifth layer, the twenty-second via hole, the U2 spiral coil group of the third layer, the twenty-seventh via hole, the U2 spiral coil group of the first layer, the twenty-third via hole, the U2 spiral coil group of the second layer, the twenty-eighth via hole, the U2 spiral coil group of the fourth layer, and the U2 pad area of ​​the fourth layer.

[0009] As a preferred embodiment, the series logic of the V1 coil region and the V2 coil region in layers one through eight is as follows: The following connections are made sequentially: the third layer V1 pad area, the third layer V1 spiral coil group, the eleventh via, the first layer V1 spiral coil group, the eighth via, the second layer V1 spiral coil group, the twelfth via, the fourth layer V1 spiral coil group, the ninth via, the sixth layer V1 spiral coil group, the thirteenth via, the fifth layer V1 spiral coil group, the tenth via, the eighth layer V1 spiral coil group, the fourteenth via, the seventh layer V1 spiral coil group, the seventh layer V2 spiral coil group, the thirty-fifth via, the eighth layer V2 spiral coil group, the thirty-first via, the fifth layer V2 spiral coil group, the thirty-third via, the sixth layer V2 spiral coil group, the twenty-ninth via, the fourth layer V2 spiral coil group, the thirty-fourth via, the second layer V2 spiral coil group, the thirtieth via, the first layer V2 spiral coil group, the thirty-second via, the third layer V2 spiral coil group, and the third layer V2 pad area.

[0010] As a preferred embodiment, the series logic of the W1 coil region and the W2 coil region in layers one through eight is as follows: The following connections are made sequentially: the W1 pad area of ​​the second layer, the W1 spiral coil group, the eighteenth via, the W1 spiral coil group of the first layer, the fifteenth via, the W1 spiral coil group of the fourth layer, the nineteenth via, the W1 spiral coil group of the third layer, the sixteenth via, the W1 spiral coil group of the fifth layer, the twentieth via, the W1 spiral coil group of the seventh layer, the seventeenth via, the W1 spiral coil group of the sixth layer, the twenty-first via, the W1 spiral coil group of the eighth layer, the W2 spiral coil group of the eighth layer, the forty-second via, the W2 spiral coil group of the sixth layer, the thirty-eighth via, the W2 spiral coil group of the seventh layer, the fortieth via, the W2 spiral coil group of the fifth layer, the thirty-sixth via, the W2 spiral coil group of the third layer, the forty-first via, the W2 spiral coil group of the fourth layer, the thirty-seventh via, the W2 spiral coil group of the first layer, the thirty-ninth via, the W2 spiral coil group of the second layer, and the W2 pad area of ​​the second layer. The U1 spiral coil group, V1 spiral coil group, W1 spiral coil group, U2 spiral coil group, V2 spiral coil group, and W2 spiral coil group each include a first straight segment, a second straight segment, a third straight segment, and an arc segment. The arc segment is located at the end away from the central through hole, and the second straight segment is located close to the central through hole. The first, second, and third straight segments are connected sequentially, and the two ends of the arc segment are respectively connected to one end of the first and third straight segments. The connection between the arc segment, the first straight segment, and the second straight segment is rounded externally, and the connection between the second straight segment and the first and third straight segments is rounded internally. The rounded external corners between adjacent spiral coil groups form an outer triangular area, and the rounded internal corners between adjacent spiral coil groups form an inner triangular area.

[0011] As a preferred embodiment, the U1 pad area, U2 pad area, V1 pad area, V2 pad area, W1 pad area and W2 pad area can be used interchangeably to achieve reverse connection of current direction.

[0012] As a preferred embodiment, the composite PCB coil board is provided with at least four pads. When the composite PCB coil board is provided with four pads, they are defined as U pad, V pad, W pad and COM pad respectively. The U1 pad area, V1 pad area and W1 pad area are respectively provided on the U pad, V pad and W pad, and the U2 pad area, V2 pad area and W2 pad area are combined and provided on the COM pad. When a composite PCB coil board has six pads, they are defined as U pad, V pad, W pad and three COM pads respectively. The U1 pad area, V1 pad area and W1 pad area are respectively set on the U pad, V pad and W pad, and the U2 pad area, V2 pad area and W2 pad area are respectively set on one COM pad.

[0013] As a preferred embodiment, the printed conductor width of the U1 spiral coil group, V1 spiral coil group, W1 spiral coil group, U2 spiral coil group, V2 spiral coil group, and W2 spiral coil group is 10-100µm, the printed conductor thickness is 10-100µm, the spacing between the printed conductors of adjacent spiral coils on the same layer is 2-50µm, the planar dimensions of the high power density PCB stator winding are 3mm×3mm-40mm×40mm, and the thickness of the PCB stator winding is 0.3mm-1.0mm.

[0014] A miniature axial flux motor includes a PCB stator winding and a rotor assembly. The PCB stator winding is a high power density PCB stator winding as described above. The number of poles of the helical coil group of the PCB stator winding and the rotor magnet of the rotor assembly adopts a three-phase six-slot eight-pole structure or a three-phase six-slot four-pole structure with slot pole matching. The rotor magnet and the helical coil group of the PCB stator winding are arranged opposite each other along the axial direction.

[0015] A miniature fan includes a base, a fan, an FPC flexible circuit board, a backplate, and a motor. The motor is a miniature axial flux motor as described above. The motor is mounted and positioned within the base. The solder pads of the PCB stator winding are soldered and fixed to the FPC flexible circuit board, which is disposed within the base. The fan is rotatably mounted on the rotor assembly of the motor and rotates synchronously with the rotor assembly. The backplate is embedded within the base, and the backplate and the rotor magnet of the rotor assembly are arranged axially and vertically opposite each other. The miniature fan has a planar dimension of 6mm×6mm-80mm×80mm and a thickness of 2mm-8mm.

[0016] Compared with the prior art, this utility model has significant advantages and beneficial effects. Specifically, as can be seen from the above technical solution, each layer has U1 coil area, V1 coil area, W1 coil area, U2 coil area, V2 coil area, and W2 coil area arranged circumferentially around the central through hole. U1 pad area, U2 pad area, V1 pad area, V2 pad area, W1 pad area, and W2 pad area are set between adjacent coil areas on the outer periphery of each layer. Moreover, the corresponding areas of each layer are arranged vertically and horizontally to ensure that the coils of the upper and lower layers are not affected by cross-wires and are axially aligned. This makes the adjacent coils of the coils not affected by cross-wires nearly symmetrical, achieving a uniform magnetic field to reduce the fluctuation of electromagnetic torque. Furthermore, the six pads are directly connected to the corresponding coil areas, eliminating the need for detour wires and shortening the length of ineffective wires at the ends. The overall diameter of the PCB stator can be reduced, fully adapting to the installation space of micro fans and solving the problem of difficult wiring with traditional multi-pads. Next is the composite PCB coil board with the first to eighth layers stacked vertically. Each layer has U1, V1, W1, U2, V2, and W2 coil areas arranged circumferentially around the central through hole, and the corresponding areas of each layer are aligned vertically. Compared with the traditional 6-layer board, the 8-layer structure increases the number of copper foil turns, improves motor efficiency, reduces power consumption, and significantly increases power density. The alignment of the areas of each layer avoids the ineffective gaps caused by misaligned layout, and improves the effective area utilization of the single-layer coil, thereby saving PCB board space. Furthermore, the vertical stacking of the first to eighth layers avoids uneven current caused by random jumps between layers, and the current is evenly distributed in each layer, effectively avoiding local overheating and extending the service life of the motor. Furthermore, by designing the wire-passing holes at the center of the inner ring of each layer of spiral coil group and the wire-passing holes on the outer periphery of the spiral coil group, the wire-passing holes in each layer of coil area are aligned vertically, avoiding the wire-passing holes from occupying the coil space, making the spacing between adjacent coils consistent with the spacing within the same coil, thereby improving space utilization and slot fill factor. Furthermore, through the structural design of the circular PCB coil board and the central through hole, the circular structure can naturally fit into the circular mounting groove of the base, achieving circumferential stability without the need for a fitting structure. This avoids the positioning failure problem that occurs when a non-circular structure is not fitted. Even if there are small protrusions on the base, the smooth circular edge will not form point-to-line contact interference with the rotor. The protrusion will only make slight contact with the arc edge. In addition, the central through hole is used for the connecting shaft of the micro fan to pass through. The connecting shaft itself can limit the radial displacement of the PCB coil board, ensuring that the PCB will not deviate from the center during operation. Another feature is the dedicated arrangement of the wire passage holes for each coil area. For example, the wire passage holes of the U1 spiral coil group are only located in the center of the inner ring or the outer periphery of the U1 coil area, without occupying the space of the adjacent coil areas. This makes the spacing between adjacent coils exactly equal to the spacing within the same coil, thereby maximizing the winding density.

[0017] To more clearly illustrate the structural features and effects of this utility model, the following detailed description of this utility model is provided in conjunction with the accompanying drawings and specific embodiments. Attached Figure Description

[0018] Figure 1 This is a wiring logic diagram of the first layer PCB coil board according to an embodiment of this utility model; Figure 2 This is a wiring logic diagram of the second layer PCB coil board according to an embodiment of this utility model; Figure 3 This is a wiring logic diagram of the third layer PCB coil board according to an embodiment of this utility model; Figure 4 This is a wiring logic diagram of the fourth layer PCB coil board according to an embodiment of this utility model; Figure 5 This is a wiring logic diagram of the fifth layer PCB coil board according to an embodiment of this utility model; Figure 6 This is a wiring logic diagram of the sixth layer PCB coil board according to an embodiment of this utility model; Figure 7 This is a wiring logic diagram of the seventh layer PCB coil board according to an embodiment of this utility model; Figure 8 This is a wiring logic diagram of the eighth layer PCB coil board according to an embodiment of this utility model; Figure 9 This is a structural diagram of a PCB coil board according to an embodiment of this utility model; Figure 10 This is a perspective view of a miniature fan according to an embodiment of the present invention; Figure 11 This is a cross-sectional view of a miniature fan according to an embodiment of this utility model; Figure 12 This is a current waveform diagram of a 6-slot 8-pole structure in an embodiment of this utility model; Figure 13 This is a power waveform diagram of an embodiment of the present invention using a 6-slot 8-pole structure; Figure 14 This is a torque waveform diagram of an embodiment of the present invention using a 6-slot 8-pole structure; Figure 15 This is a power waveform diagram of the existing technology using a 6-slot 8-pole structure; Figure 16 This is a torque waveform diagram using the existing technology with a 6-slot 8-pole structure; Figure 17 This is a structural diagram of a PCB coil board with six solder pads, as described in an embodiment of this utility model. Figure 18 This is a structural diagram of a PCB coil board with four solder pads, as described in an embodiment of this utility model.

[0019] Explanation of reference numerals in the attached diagram: 1. Central through hole; 2. U1 coil area 3. V1 coil area 4. W1 coil area 5. U2 coil area 6. V2 coil area 7. W2 coil area 21. U1 spiral coil group; 31. V1 spiral coil group 41. W1 spiral coil group; 51. U2 spiral coil group 61. V2 spiral coil group; 71. W2 spiral coil group 211. First straight segment; 212. Second straight segment 213. The third straight line segment; 214. The circular arc segment. 8. U1 pad area 9. U2 pad area 10. V1 pad area 11. V2 pad area 12. W1 pad area 13. W2 pad area 100, PCB stator winding 14. Rotor assembly 15. Base 16. Fan blades 17. FPC flexible circuit board 18. Back iron 19. Magnet. Detailed Implementation

[0020] Please refer to Figures 1 to 18 As shown, it illustrates the specific structure of an embodiment of the present invention.

[0021] In the description of this utility model, it should be noted that the directional terms such as "up", "down", "front", "back", "left", and "right" indicate the orientation and positional relationship based on the accompanying drawings or the orientation or positional relationship shown when wearing and using the device normally. They are only for the convenience of describing this utility model and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. They should not be construed as limiting the specific protection scope of this utility model.

[0022] A high power density PCB stator winding includes a circular composite PCB coil board.

[0023] It has eight layers stacked sequentially, namely, the first, second, third, fourth, fifth, sixth, seventh, and eighth PCB coil boards. Each layer has a central through hole 1 and U1 coil region 2, V1 coil region 3, W1 coil region 4, U2 coil region 5, V2 coil region 6, and W2 coil region 7 arranged circumferentially around the central through hole 1. Preferably, each layer has a central through hole 1 and U1 coil region 2, V1 coil region 3, W1 coil region 4, U2 coil region 5, V2 coil region 6, and W2 coil region 7 arranged circumferentially around the central through hole 1. The magnetic field gradient of adjacent coil regions is continuous, without local magnetic field discontinuity, which effectively reduces torque fluctuation caused by region misalignment, making the motor run more smoothly. Furthermore, the sequential arrangement avoids coil region crossing or uneven gaps, improves the effective winding area utilization rate of a single-layer PCB coil board, and further reduces ineffective gaps.

[0024] Each layer has U1 pad area 8, U2 pad area 9, V1 pad area 10, V2 pad area 11, W1 pad area 12, and W2 pad area 13 arranged between adjacent coil areas on the outer periphery, with the corresponding areas of each layer arranged vertically opposite each other; preferably, the U1 pad area 8, U2 pad area 9, V1 pad area 10, V2 pad area 11, W1 pad area 12, and W2 pad area 13 can be used interchangeably to achieve reverse current connection, which can directly realize the reverse direction of three-phase current, meet the forward and reverse rotation requirements of micro fans, without disassembling or modifying the winding structure, without developing multiple versions of PCB stators for different rotation requirements, the same product can adapt to multiple working conditions, and only external wiring needs to be adjusted during later maintenance, making the operation simple.

[0025] like Figure 17 As shown, when a composite PCB coil board has six pads, they are defined as U pad, V pad, W pad, and three COM pads. The U1, V1, and W1 pad areas are respectively located on the U, V, and W pads, while the U2, V2, and W2 pad areas are each located on one COM pad. This ensures uniform pad distribution and high soldering strength and positioning accuracy. U1, V1, and W1 refer to the head line pads, and the three COM pads refer to the tail line pads. Figure 17 The three COM pads in the diagram correspond to the U2 pad, V2 pad, and W2 pad, respectively.

[0026] like Figure 18As shown, the composite PCB coil board has at least four pads. When the composite PCB coil board has four pads, they are defined as U pad, V pad, W pad, and COM pad, respectively. The U1 pad area, V1 pad area, and W1 pad area are respectively located on the U pad, V pad, and W pad, while the U2 pad area, V2 pad area, and W2 pad area are combined and located on the COM pad. By placing the pad areas on the outer periphery of each layer as connection points, space is fully utilized, PCB space is saved, and the extra space occupied by the pads is avoided, which would affect the winding layout and the overall compactness of the motor structure. It also facilitates production processing and subsequent circuit connection operations. Among them, U1, V1, and W1 refer to the head wire pad, and the COM pad refers to the tail wire pad.

[0027] In the composite PCB coil board of each layer, the through holes at the center of the inner ring of each spiral coil group in coil area 2 (U1), coil area 3 (V1), coil area 4 (W1), coil area 5 (U2), coil area 6 (V2), and coil area 7 (W2) are all arranged vertically opposite each other. The through holes in each layer of coil area are arranged vertically opposite each other to avoid the through holes occupying the coil space, so that the spacing between adjacent coils is consistent with the spacing within the same coil, thereby improving the space utilization and slot fill rate.

[0028] Each of the U1, V1, W1, U2, V2, and W2 coil regions contains a spiral coil group. Each spiral coil group has an inner wire-passing hole at its inner ring center and an outer wire-passing hole located on its outer periphery. The inner ring centers of each layer are vertically aligned, and the outer wire-passing holes of each layer are also vertically aligned. The inner wire-passing hole is located at the center of the inner ring of the spiral coil group in the corresponding coil region.

[0029] The U1 coil region 2 is provided with a U1 spiral coil group 21 and a fourth wire through hole, a fifth wire through hole, a sixth wire through hole, and a seventh wire through hole located at the center of the inner ring of the U1 spiral coil group 21, as well as a first wire through hole, a second wire through hole, and a third wire through hole located on the outer periphery of the U1 spiral coil group 21. The V1 coil region 3 is provided with a V1 spiral coil group 31 and an eleventh wire through hole, a twelfth wire through hole, a thirteenth wire through hole, and a fourteenth wire through hole located at the center of the inner ring of the V1 spiral coil group 31, as well as an eighth wire through hole, a ninth wire through hole, and a tenth wire through hole located on the outer periphery of the V1 spiral coil group 31. The W1 coil region 4 is provided with a W1 spiral coil group 41 and eighteenth, nineteenth, twentieth and twenty-first wire passing holes located at the center of the inner ring of the W1 spiral coil group 41, as well as fifteenth, sixteenth and seventeenth wire passing holes located on the outer periphery of the W1 spiral coil group 41. The U2 coil region 5 is provided with a U2 spiral coil group 51 and a 25th wire through hole, a 26th wire through hole, a 27th wire through hole, and a 28th wire through hole located at the center of the inner ring of the U2 spiral coil group 51, as well as a 22nd wire through hole, a 23rd wire through hole, and a 24th wire through hole located on the outer periphery of the U2 spiral coil group 51. The V2 coil region 6 is provided with a V2 spiral coil group 61 and a 32nd, 33rd, 34th and 35th wire through hole located at the center of the inner ring of the V2 spiral coil group 61, as well as a 29th, 30th and 31st wire through hole located on the outer periphery of the V2 spiral coil group 61. The W2 coil region 7 is provided with a W2 spiral coil group 71 and a 39th wire through hole, a 40th wire through hole, a 41st wire through hole, and a 42nd wire through hole located at the center of the inner ring of the W2 spiral coil group 71, as well as a 36th wire through hole, a 37th wire through hole, and a 38th wire through hole located on the outer periphery of the W2 spiral coil group 71. And the series logic of U1 coil region 2 and U2 coil region 5 in layers 1 to 8: The following are the components of the U1 pad area (4th layer), U1 spiral coil group (4th layer), fourth via hole, U1 spiral coil group (21th layer), first via hole, U1 spiral coil group (21th layer), fifth via hole, U1 spiral coil group (21th layer), second via hole, U1 spiral coil group (21th layer), sixth via hole, U1 spiral coil group (21th layer), third via hole, U1 spiral coil group (21th layer), seventh via hole, U1 spiral coil group (21th layer), and U2 spiral wire (6th layer). Connect the following wires sequentially: coil group 51, the 25th wire guide hole, the 7th layer U2 spiral coil group 51, the 24th wire guide hole, the 8th layer U2 spiral coil group 51, the 26th wire guide hole, the 5th layer U2 spiral coil group 51, the 22nd wire guide hole, the 3rd layer U2 spiral coil group 51, the 27th wire guide hole, the 1st layer U2 spiral coil group 51, the 23rd wire guide hole, the 2nd layer U2 spiral coil group 51, the 28th wire guide hole, the 4th layer U2 spiral coil group 51, and the 4th layer U2 pad area 9. The series logic of V1 coil region 3 and V2 coil region 6 in layers 1 to 8: The third layer V1 pad area 10, the third layer V1 spiral coil group 31, the eleventh via, the first layer V1 spiral coil group 31, the eighth via, the second layer V1 spiral coil group 31, the twelfth via, the fourth layer V1 spiral coil group 31, the ninth via, the sixth layer V1 spiral coil group 31, the thirteenth via, the fifth layer V1 spiral coil group 31, the tenth via, the eighth layer V1 spiral coil group 31, the fourteenth via, the seventh layer V1 spiral coil group 31, and the seventh layer V2... The spiral coil group 61, the thirty-fifth through hole, the V2 spiral coil group 61 of the eighth layer, the thirty-first through hole, the V2 spiral coil group 61 of the fifth layer, the thirty-third through hole, the V2 spiral coil group 61 of the sixth layer, the twenty-ninth through hole, the V2 spiral coil group 61 of the fourth layer, the thirty-fourth through hole, the V2 spiral coil group 61 of the second layer, the thirty-second through hole, the V2 spiral coil group 61 of the first layer, the thirty-second through hole, the V2 spiral coil group 61 of the third layer, and the V2 pad area 11 of the third layer are connected sequentially. The series logic of W1 coil region 4 and W2 coil region 7 in layers 1 to 8: The second layer W1 pad area 12, W1 spiral coil group 41, eighteenth via hole, first layer W1 spiral coil group 41, fifteenth via hole, fourth layer W1 spiral coil group 41, nineteenth via hole, third layer W1 spiral coil group 41, sixteenth via hole, fifth layer W1 spiral coil group 41, twentieth via hole, seventh layer W1 spiral coil group 41, seventeenth via hole, sixth layer W1 spiral coil group 41, twenty-first via hole, eighth layer W1 spiral coil group 41, eighth layer W2 The following wires are connected sequentially: spiral coil group 71, the forty-second through hole, the sixth layer W2 spiral coil group 71, the thirty-eighth through hole, the seventh layer W2 spiral coil group 71, the fortieth through hole, the fifth layer W2 spiral coil group 71, the thirty-sixth through hole, the third layer W2 spiral coil group 71, the forty-first through hole, the fourth layer W2 spiral coil group 71, the thirty-seventh through hole, the first layer W2 spiral coil group 71, the thirty-ninth through hole, the second layer W2 spiral coil group 71, and the second layer W2 pad area 13.

[0030] In this embodiment, as Figures 1-8 As shown, to facilitate further explanation of the interlayer via connection logic and wiring logic, the coils of the 6 coil regions are defined by the symbol LXY, where X is the coil region number from 1 to 6, Y is the layer number from 1 to 8, and LXY represents the coil of the Y layer in the Xth coil region. The 8 layers of coils in the same coil region are collectively called the LX coil group. The 1st to 6th coil regions are respectively formed into L1X, L2X, L3X, L4X, L5X, and L6X coil groups. Each coil region is provided with 7 through holes, which are defined by the symbol VX, where V is the through hole and X is the number of the through hole. The 7 through holes in each coil region are 4 internal through holes and 3 external through holes. Coils in different layers within the same LX coil group are connected in series through the through holes. Three COM terminals are also provided between adjacent coil areas on the outer periphery of each layer. U1 is the start-line terminal of the U-phase winding, U2 is the end-line terminal of the U-phase winding, V1 is the start-line terminal of the V-phase winding, and V2 is the end-line terminal of the V-phase winding; W1 is the start-line terminal of the W-phase winding, and W2 is the end-line terminal of the W-phase winding. The L1X coil group and L4X coil group are connected in series to form the U-phase, and their electrical connection path is as follows: The current flows in from the U-phase head wire, connects coils L14, L12, L11, L13, L15, L18, L17, and L16 in sequence, then connects to L46 of the L4X coil group via a jumper wire, and then connects to coils L47, L48, L45, L43, L41, L42, and L44 in sequence, finally flowing out from the U-phase tail wire; among them, the interlayer series connection within the L1X coil group passes through wire holes V4, V1, V5, V2, V6, V3, and V7 in sequence; the interlayer series connection within the L4X coil group passes through wire holes V25, V24, V26, V22, V27, V23, and V28 in sequence; The L2X coil group and the L5X coil group are connected in series to form phase V, and their electrical connection path is as follows: The current flows in from the V-phase lead wire, and connects in sequence to coils L23, L21, L22, L24, L26, L25, L28, and L27. Then, it is connected to L57 of the L5X coil group through a jumper wire, and then connected in sequence to coils L58, L55, L56, L54, L52, L51, and L53. Finally, it flows out from the V-phase tail wire. Among them, the interlayer series connection within the L2X coil group passes through wire holes V11, V8, V12, V9, V13, V10, and V14 in sequence, and the interlayer series connection within the L5X coil group passes through wire holes V35, V31, V33, V29, V34, V30, and V32 in sequence. The L3X coil group and the L6X coil group are connected in series to form phase W; their electrical connection path is as follows: The current flows in from the W phase head wire, and connects in sequence to coils L32, L31, L34, L33, L35, L37, L36, and L38. Then it is connected to L68 of the L6X coil group through a crossover wire, and then connected in sequence to coils L66, L67, L65, L63, L64, L61, and L62. Finally, it flows out from the W phase tail wire. Among them, the interlayer series connection of the L3X coil group passes through the wire holes V18, V15, V19, V16, V20, V17, and V21 in sequence, and the interlayer series connection of the L6X coil group passes through the wire holes V42, V38, V40, V36, V41, V37, and V39 in sequence.

[0031] Preferably, the U1 spiral coil group 21 of the sixth layer passes through the V1 coil region 3 and the W1 coil region 4 of the sixth layer, and is connected to the U2 spiral coil group 51 of the sixth layer by a cross-wire in the same layer; The V1 spiral coil group 31 of the seventh layer passes through the W1 coil region 4 and the U2 coil region 5 of the seventh layer, and is connected in series with the V2 spiral coil group 61 of the seventh layer by a cross-wire in the same layer. The W1 spiral coil group 41 of the eighth layer passes through the U2 coil region 5 and V2 coil region 6 of the eighth layer. The same layer crossover line is connected in series with the W2 spiral coil group 71 of the eighth layer. The length of its straight segment is longer than the length of the straight segment of the coil that is not affected by the crossover line, so as to perform resistance compensation, realize the resistance balance of the two types of coils, avoid phase current fluctuations, and the crossover line connects the same phase coil region according to the layer level, avoiding electromagnetic coupling interference between different phase crossover lines, further improving motor efficiency, solving the efficiency loss problem caused by traditional crossover line interference, and matching the crossover line path with the coil region layout, eliminating the need for long-distance traces on the surface layer, further saving PCB space.

[0032] Preferably, the U1 spiral coil group 21, V1 spiral coil group 31, W1 spiral coil group 41, U2 spiral coil group 51, V2 spiral coil group 61, and W2 spiral coil group 71 each include a first straight segment 211, a second straight segment 212, a third straight segment 213, and an arc segment 214. The arc segment 214 is located at the end away from the central through hole 1, and the second straight segment 212 is located close to the central through hole 1. The first straight segment 211, the second straight segment 212, and the third straight segment 213 are connected sequentially. Then, the two ends of the arc segment 214 are respectively connected to one end of the first straight segment 211 and the third straight segment 213, so that there is still enough effective conductor near the center through hole 1 of the inner coil, avoiding the waste of magnetic flux caused by the blank inner coil, and the electromagnetic conversion efficiency is higher. The length of its straight segment is longer than the length of the straight segment of the coil that is not affected by the cross wire, so as to perform resistance compensation, realize the resistance balance of the two types of coils, avoid phase current fluctuation, and the cross wires are connected to the same phase coil area in a layered manner to avoid electromagnetic coupling interference between cross wires of different phases, and the motor efficiency is further improved.

[0033] Preferably, the connection between the arc segment 214, the first straight segment 211, and the second straight segment 212 is rounded on the outside, and the connection between the second straight segment 212 and the first straight segment 211 and the third straight segment 213 is rounded on the inside. The rounded outside between adjacent spiral coil groups forms an outer triangular area, and the rounded inside between adjacent spiral coil groups forms an inner triangular area. This minimizes torque loss to the motor without affecting the wiring.

[0034] Because the coil shape uses three straight segments, one circular arc, and four rounded corners, the through-hole pads can be placed in the blank areas between adjacent coils, thus maximizing the effective coil area and improving motor performance. The electromagnetic simulation results of the motor are as follows:

[0035] Resistance values ​​for each phase: U phase 18.1 ohms, V phase 18.0 ohms, W phase 18.1 ohms, resistivity calculated at 0.0185 Ohm.mm² / m.

[0036] like Figures 12-14 As shown, this is the simulation result (19000 RPM) of this 8-layer board with 6 slots and 8 poles. Figures 15-16 As shown, the simulation results (19000RPM) of a 6-layer board with 6 slots and 8 poles are shown. The six slots refer to the six stator coils, and the four or eight poles are the number of poles of the rotor magnet.

[0037] Preferably, the U1 spiral coil group 21, V1 spiral coil group 31, W1 spiral coil group 41, U2 spiral coil group 51, and V2 spiral coil group 61 are wound with printed conductors. The printed conductor width and thickness of the U1 spiral coil group 21, V1 spiral coil group 31, W1 spiral coil group 41, U2 spiral coil group 51, V2 spiral coil group 61, and W2 spiral coil group 71 are 10-100µm, and the spacing between the printed conductors of adjacent spiral coils in the same layer is 2-50µm. This can meet the current requirements of the micro fan and avoid overheating caused by excessively thin conductors. The spacing between adjacent spiral coils is minimized to maximize the reduction of coil gap and increase winding density while ensuring insulation performance.

[0038] The planar dimensions of the PCB stator winding are 3mm×3mm-40mm×40mm, and the thickness of the PCB stator winding is 0.3mm-1.0mm. This ensures that the PCB coil board, as the core driving component, can be stably embedded inside the micro fan (such as the fan frame and stator area). The thin design of the PCB coil board can reduce the overall height occupied by the micro fan. Combined with the micro fan's height of as low as 2mm, the entire fan assembly can be adapted to the installation space of ultra-thin devices (such as micro fans), meeting the requirements of miniaturization and flattening structure. Preferably, the high power density PCB stator winding further includes two driving boards, which are disposed above or below the circular PCB coil board for mounting the driving circuit.

[0039] A miniature axial flux motor includes a PCB stator winding 100 and a rotor assembly 14. The PCB stator winding 100 is a high-power-density PCB stator winding. The helical coil group of the PCB stator winding and the rotor magnet 19 of the rotor assembly 14 adopt a three-phase six-slot eight-pole structure or a three-phase six-slot four-pole structure with slot-pole matching. The rotor magnet 19 and the helical coil group of the PCB stator winding are arranged axially opposite each other to achieve axial flux coupling. The rotor assembly 14 includes a motor housing, magnet 19, and shaft. The shaft is mounted on a bearing. The lower end face of the shaft may be selectively provided with wear-resistant plates to support the shaft, reduce frictional wear between the shaft and the base 15 during rotation, reduce noise, and improve operational stability.

[0040] A miniature fan includes a base 15, a fan, an FPC flexible board 17, a backplate 18, and a motor. The motor is a miniature axial flux motor, which is mounted and positioned within the base 15. The solder pads of the PCB stator winding are soldered and fixed to the FPC flexible board. The FPC flexible board 17 is disposed within the base 15. The fan is rotatably mounted on the rotor assembly 14 of the motor and rotates synchronously with the rotor assembly 14. The backplate is embedded within the base 15, and the backplate 18 and the rotor magnet 19 of the rotor assembly 14 are arranged axially and vertically opposite each other to enhance the magnetic field strength between the rotor magnet 19 and the PCB stator winding. The miniature fan has a planar dimension of 6mm×6mm-80mm×80mm and a thickness of 2mm-8mm.

[0041] The base 15 has a shaft hole near its center, and a bearing is installed inside the shaft hole. The fan blades 16 are fitted onto the motor housing, and one end of the shaft is fixed to the center of the motor housing. The magnet 19 is installed inside the motor housing. When the PCB coil board is powered on, the generated magnetic field drives the magnet 19 and the motor housing to rotate together, thereby driving the fan blades 16 to rotate and achieve the function of blowing air for heat dissipation. If only a motor is required, the fan blades 16 can be omitted.

[0042] The back iron 18 is embedded in the base 15. That is, during injection molding, the back iron 18 is pre-positioned in the mold cavity, and the base 15 is formed by injection molding, thus embedding the back iron 18 in the base 15, and its position corresponds to that of the magnet 19. Because the back iron 18 is located within the base 15 and is relatively high, the distance between it and the magnet 19 is shortened, which increases the magnetic pull and effectively reduces the eddy current effect, thereby improving motor efficiency.

[0043] Alternatively, the base 15 can be replaced with an LDS base 15. The surface of the LDS base 15 has an LDS circuit formed by the LDS process. The LDS circuit includes traces, solder joints, metal contacts, and other structures. The FPC flexible board 17 is replaced by the LDS circuit. That is, the LDS circuit has six solder joints corresponding to the solder pads U1, V1, W1, U2, V2, and W2 on the PCB coil board.

[0044] The key design feature of this invention is that each layer has a U1 coil area, a V1 coil area, a W1 coil area, a U2 coil area, a V2 coil area, and a W2 coil area arranged circumferentially around a central through-hole. U1 pad areas, U2 pad areas, V1 pad areas, V2 pad areas, W1 pad areas, and W2 pad areas are provided between adjacent coil areas on the outer periphery of each layer. Furthermore, the corresponding areas of each layer are vertically aligned, ensuring that coils in the upper and lower layers, unaffected by cross-wires, are axially aligned. This results in nearly symmetrical adjacent coils, achieving a uniform magnetic field and reducing electromagnetic torque fluctuations. The six pads directly connect to their corresponding coil areas, eliminating the need for winding wires and shortening the length of ineffective end wires. The overall diameter of the PCB stator can be reduced, perfectly fitting the installation space of a miniature fan and solving the problem of difficult wiring with traditional multi-pad designs. Secondly, the U1 spiral coil group is connected to the U2 spiral coil group via a crossover on the sixth layer, the V1 spiral coil group is connected to the V2 spiral coil group via a crossover on the seventh layer, and the W1 spiral coil group is connected to the W2 spiral coil group via a crossover on the eighth layer. The spiral coil design has a longer straight segment than the coils that are not affected by the crossover, in order to compensate for the resistance value and achieve resistance balance between the two types of coils, avoiding phase current fluctuations. Furthermore, the crossovers are connected to the same phase coil areas in a layered manner, avoiding electromagnetic coupling interference between crossovers of different phases, which further improves motor efficiency and solves the efficiency loss problem caused by traditional crossover interference. In addition, the crossover path matches the coil area layout, eliminating the need for long-distance traces on the surface layer and further saving PCB space. Next is the composite PCB coil board with the first to eighth layers stacked vertically. Each layer has U1, V1, W1, U2, V2, and W2 coil areas arranged circumferentially around the central through hole, and the corresponding areas of each layer are aligned vertically. Compared with the traditional 6-layer board, the 8-layer structure increases the number of copper foil turns, improves motor efficiency, reduces power consumption, and significantly increases power density. The alignment of the areas of each layer avoids the ineffective gaps caused by misaligned layout, and improves the effective area utilization of the single-layer coil, thereby saving PCB board space. Furthermore, the vertical stacking of the first to eighth layers avoids uneven current caused by random jumps between layers, and the current is evenly distributed in each layer, effectively avoiding local overheating and extending the service life of the motor. Furthermore, by designing the wire-passing holes at the center of the inner ring of each layer of spiral coil group and the wire-passing holes on the outer periphery of the spiral coil group, the wire-passing holes in each layer of coil area are aligned vertically, avoiding the wire-passing holes from occupying the coil space, making the spacing between adjacent coils consistent with the spacing within the same coil, thereby improving space utilization and slot fill factor. Furthermore, through the structural design of the circular PCB coil board and the central through hole, the circular structure can naturally fit into the circular mounting groove of the base, achieving circumferential stability without the need for a fitting structure. This avoids the positioning failure problem that occurs when a non-circular structure is not fitted. Even if there are small protrusions on the base, the smooth circular edge will not form point-to-line contact interference with the rotor. The protrusion will only make slight contact with the arc edge. In addition, the central through hole is used for the connecting shaft of the micro fan to pass through. The connecting shaft itself can limit the radial displacement of the PCB coil board, ensuring that the PCB will not deviate from the center during operation. Another feature is the dedicated arrangement of the wire passage holes for each coil area. For example, the wire passage holes of the U1 spiral coil group are only located in the center of the inner ring or the outer periphery of the U1 coil area, without occupying the space of the adjacent coil areas. This makes the spacing between adjacent coils exactly equal to the spacing within the same coil, thereby maximizing the winding density.

[0045] The above description is merely a preferred embodiment of the present utility model and does not constitute any limitation on the technical scope of the present utility model. Therefore, any minor modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present utility model shall still fall within the scope of the technical solution of the present utility model.

Claims

1. A high power density PCB stator winding, characterized in that: It includes a circular composite PCB coil board, which has first to eighth layers stacked vertically; each layer has a central through hole and U1 coil area, V1 coil area, W1 coil area, U2 coil area, V2 coil area and W2 coil area arranged circumferentially around the central through hole, and U1 pad area, U2 pad area, V1 pad area, V2 pad area, W1 pad area and W2 pad area are arranged between adjacent coil areas on the outer periphery of each layer, and the corresponding areas of each layer are arranged vertically opposite each other; Helical coil groups are provided in the U1 coil region, V1 coil region, W1 coil region, U2 coil region, V2 coil region, and W2 coil region. An inner wire-passing hole and an outer wire-passing hole are provided at the center of the inner ring of the helical coil group. The inner ring center and the outer wire-passing hole of each layer are arranged vertically opposite each other.

2. The high power density PCB stator winding according to claim 1, characterized in that: The U1 coil area is provided with a U1 spiral coil group and a fourth wire through hole, a fifth wire through hole, a sixth wire through hole, and a seventh wire through hole located at the center of the inner ring of the U1 spiral coil group, as well as a first wire through hole, a second wire through hole, and a third wire through hole located on the outer periphery of the U1 spiral coil group. The V1 coil area is provided with a V1 spiral coil group and eleventh, twelfth, thirteenth and fourteenth wire holes located at the center of the inner ring of the V1 spiral coil group, as well as eighth, ninth and tenth wire holes located on the outer periphery of the V1 spiral coil group. The W1 coil area is provided with a W1 spiral coil group and eighteenth, nineteenth, twentieth, and twenty-first wire passing holes located at the center of the inner ring of the W1 spiral coil group, as well as fifteenth, sixteenth, and seventeenth wire passing holes located on the outer periphery of the W1 spiral coil group. The U2 coil area is provided with a U2 spiral coil group and a 25th, 26th, 27th and 28th wire through hole located at the center of the inner ring of the U2 spiral coil group, as well as a 22nd, 23rd and 24th wire through hole located on the outer periphery of the U2 spiral coil group. The V2 coil area is provided with a V2 spiral coil group and a 32nd, 33rd, 34th and 35th wire through hole located at the center of the inner ring of the V2 spiral coil group, as well as a 29th, 30th and 31st wire through hole located on the outer periphery of the V2 spiral coil group. The W2 coil area is provided with a W2 spiral coil group and a 39th, 40th, 41st and 42nd wire passing hole located at the center of the inner ring of the W2 spiral coil group, as well as a 36th, 37th and 38th wire passing hole located on the outer periphery of the W2 spiral coil group.

3. The high power density PCB stator winding according to claim 2, characterized in that: The series logic of the U1 coil region and the U2 coil region in layers one through eight: The following connections are made sequentially: the U1 pad area of ​​the fourth layer, the U1 spiral coil group of the fourth layer, the fourth via hole, the U1 spiral coil group of the second layer, the first via hole, the U1 spiral coil group of the first layer, the fifth via hole, the U1 spiral coil group of the third layer, the second via hole, the U1 spiral coil group of the fifth layer, the sixth via hole, the U1 spiral coil group of the eighth layer, the third via hole, the U1 spiral coil group of the seventh layer, the seventh via hole, the U1 spiral coil group of the sixth layer, the U2 spiral coil group of the sixth layer, the twenty-fifth via hole, the U2 spiral coil group of the seventh layer, the twenty-fourth via hole, the U2 spiral coil group of the eighth layer, the twenty-sixth via hole, the U2 spiral coil group of the fifth layer, the twenty-second via hole, the U2 spiral coil group of the third layer, the twenty-seventh via hole, the U2 spiral coil group of the first layer, the twenty-third via hole, the U2 spiral coil group of the second layer, the twenty-eighth via hole, the U2 spiral coil group of the fourth layer, and the U2 pad area of ​​the fourth layer.

4. The high power density PCB stator winding according to claim 2, characterized in that: The series logic of the V1 coil region and the V2 coil region from the first to the eighth layers: The following connections are made sequentially: the third layer V1 pad area, the third layer V1 spiral coil group, the eleventh via, the first layer V1 spiral coil group, the eighth via, the second layer V1 spiral coil group, the twelfth via, the fourth layer V1 spiral coil group, the ninth via, the sixth layer V1 spiral coil group, the thirteenth via, the fifth layer V1 spiral coil group, the tenth via, the eighth layer V1 spiral coil group, the fourteenth via, the seventh layer V1 spiral coil group, the seventh layer V2 spiral coil group, the thirty-fifth via, the eighth layer V2 spiral coil group, the thirty-first via, the fifth layer V2 spiral coil group, the thirty-third via, the sixth layer V2 spiral coil group, the twenty-ninth via, the fourth layer V2 spiral coil group, the thirty-fourth via, the second layer V2 spiral coil group, the thirtieth via, the first layer V2 spiral coil group, the thirty-second via, the third layer V2 spiral coil group, and the third layer V2 pad area.

5. The high power density PCB stator winding according to claim 2, characterized in that: The series logic of the W1 coil region and the W2 coil region in layers one through eight: The following connections are made sequentially: the W1 pad area of ​​the second layer, the W1 spiral coil group, the eighteenth via, the W1 spiral coil group of the first layer, the fifteenth via, the W1 spiral coil group of the fourth layer, the nineteenth via, the W1 spiral coil group of the third layer, the sixteenth via, the W1 spiral coil group of the fifth layer, the twentieth via, the W1 spiral coil group of the seventh layer, the seventeenth via, the W1 spiral coil group of the sixth layer, the twenty-first via, the W1 spiral coil group of the eighth layer, the W2 spiral coil group of the eighth layer, the forty-second via, the W2 spiral coil group of the sixth layer, the thirty-eighth via, the W2 spiral coil group of the seventh layer, the fortieth via, the W2 spiral coil group of the fifth layer, the thirty-sixth via, the W2 spiral coil group of the third layer, the forty-first via, the W2 spiral coil group of the fourth layer, the thirty-seventh via, the W2 spiral coil group of the first layer, the thirty-ninth via, the W2 spiral coil group of the second layer, and the W2 pad area of ​​the second layer. The U1 spiral coil group, V1 spiral coil group, W1 spiral coil group, U2 spiral coil group, V2 spiral coil group, and W2 spiral coil group each include a first straight segment, a second straight segment, a third straight segment, and an arc segment. The arc segment is located at the end away from the central through hole, and the second straight segment is located close to the central through hole. The first, second, and third straight segments are connected sequentially, and the two ends of the arc segment are respectively connected to one end of the first and third straight segments. The connection between the arc segment, the first straight segment, and the second straight segment is rounded externally, and the connection between the second straight segment and the first and third straight segments is rounded internally. The rounded external corners between adjacent spiral coil groups form an outer triangular area, and the rounded internal corners between adjacent spiral coil groups form an inner triangular area.

6. The high power density PCB stator winding according to claim 1, characterized in that: The U1 pad area, U2 pad area, V1 pad area, V2 pad area, W1 pad area, and W2 pad area can be used interchangeably to achieve reverse current direction connection.

7. The high power density PCB stator winding according to claim 1, characterized in that: The composite PCB coil board is provided with at least four pads. When the composite PCB coil board is provided with four pads, they are defined as U pad, V pad, W pad and COM pad respectively. The U1 pad area, V1 pad area and W1 pad area are respectively provided on the U pad, V pad and W pad. The U2 pad area, V2 pad area and W2 pad area are combined and provided on the COM pad. When a composite PCB coil board has six pads, they are defined as U pad, V pad, W pad and three COM pads respectively. The U1 pad area, V1 pad area and W1 pad area are respectively set on the U pad, V pad and W pad, and the U2 pad area, V2 pad area and W2 pad area are respectively set on one COM pad.

8. The high power density PCB stator winding according to claim 2, characterized in that: The printed conductor width of the U1 spiral coil group, V1 spiral coil group, W1 spiral coil group, U2 spiral coil group, V2 spiral coil group, and W2 spiral coil group is 10-100µm, the printed conductor thickness is 10-100µm, the spacing between the printed conductors of adjacent spiral coils on the same layer is 2-50µm, the planar dimensions of the high power density PCB stator winding are 3mm×3mm-40mm×40mm, and the thickness of the high power density PCB stator winding is 0.3mm-1.0mm.

9. A miniature axial flux motor, characterized in that: It includes a PCB stator winding and a rotor assembly. The PCB stator winding is a high power density PCB stator winding as described in any one of claims 1 to 8. The number of poles of the rotor magnet of the PCB stator winding and the rotor assembly adopts a three-phase six-slot eight-pole structure or a three-phase six-slot four-pole structure with slot pole matching. The rotor magnet and the helical coil group of the PCB stator winding are arranged opposite each other along the axial direction.

10. A miniature fan, characterized in that: The device includes a base, a fan, an FPC flexible circuit board, a back iron, and a motor. The motor is a miniature axial flux motor as described in claim 9. The motor is installed and positioned within the base. The solder pad area of ​​the PCB stator winding is soldered and fixed to the FPC flexible circuit board. The FPC flexible circuit board is disposed within the base. The fan is rotatably mounted on the rotor assembly of the motor and rotates synchronously with the rotor assembly. The back iron is embedded within the base, and the back iron and the rotor magnet of the rotor assembly are arranged vertically opposite each other along the axial direction. The planar dimensions of the miniature fan are 6mm×6mm-80mm×80mm, and the thickness is 2mm-8mm.

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