Space type planar transformer and electronic device
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- DONGGUAN SUNLORD POWER DEVICE CO LTD
- Filing Date
- 2024-12-27
- Publication Date
- 2026-05-12
Smart Images
Figure CN119517568B_ABST
Abstract
Description
Technical Field
[0001] This application relates to the field of magnetic device technology, specifically to a spatial planar transformer and electronic device. Background Technology
[0002] In the manufacturing process of magnetic devices, planar transformers are transformers that use a planar structure instead of a traditional winding structure. They are widely used in various high-frequency, high-efficiency power systems, especially in applications with high space and performance requirements. In existing technologies, the winding coils of planar transformers are usually formed by developing and etching or laser etching processes on a PCB (printed circuit board). The winding method is usually helical wiring, and different windings are usually connected using through holes to allow signals to be transmitted between multiple layers of the PCB. However, when PCB wiring of existing planar transformers, it is necessary to consider avoiding the through holes with the coils. Buried or blind via structures are more expensive, and the coils also need to be bent to avoid the through holes, resulting in a larger size and lower cost-effectiveness of planar transformers. This situation needs to be changed. Summary of the Invention
[0003] In view of this, this application provides a spatial planar transformer and electronic device to solve the aforementioned technical problems.
[0004] To achieve the above objectives, based on the first aspect, the technical solution adopted is as follows:
[0005] A spatial planar transformer, comprising:
[0006] A first wiring board and at least one second wiring board are stacked together;
[0007] A magnetic pillar window is provided at the center of the first wiring board and the second wiring board. At least one first coil group and a second coil group are arranged on both the first wiring board and the second wiring board. The first coil group is wound around the outside of the magnetic pillar window, and the second coil group is spaced apart from the first coil group, or the second coil group is wound around the outside of the magnetic pillar window and is arranged alternately with the first coil group. Both the first wiring board and the second wiring board are provided with a group of connecting holes. The first coil group on the first wiring board is electrically connected to the second coil group on the second wiring board through the group of connecting holes, and the second coil group on the first wiring board is electrically connected to the first coil group on the second wiring board through the group of connecting holes.
[0008] This application is further configured such that: when the second coil group and the first coil group are spaced apart, the first coil group includes a plurality of first single-turn wire layers, the second coil group includes a second single-turn wire layer with the same number as the first single-turn wire layers, and the plurality of first single-turn wire layers are arranged sequentially from the vicinity of the magnetic pillar window to the distance from the magnetic pillar window.
[0009] This application is further configured such that: the first single-turn wire layer on the first wiring board and the second single-turn wire layer on the second wiring board form a continuous winding coil through the connecting hole group, and the output / input terminal of the winding coil extends to the side of the first wiring board and is connected to the PIN of the first wiring board.
[0010] This application is further configured such that: the connection hole group includes a plurality of first functional holes and second functional holes arranged linearly on the first wiring board and the second wiring board, the first functional holes and the second functional holes are designed to be far away from the magnetic pillar window, the first functional holes are connected to the first single-turn wire layer of the portion, and the second functional holes are connected to the beginning and end ends of the second single-turn wire layer.
[0011] This application is further configured such that the first functional hole on the first wiring board and the second functional hole on the second wiring board, and the projection of the first functional hole on the second wiring board and the second functional hole on the first wiring board in the direction perpendicular to the working surface of the first wiring board and the second wiring board coincide.
[0012] This application is further configured such that: when the second coil group and the first coil group are spaced apart, the first coil group has a ring structure design with a wiring gap, the second coil group has a rectangular structure design, the wiring gap is away from the second coil group, and the connecting hole group is located on the side of the second coil group and at the wiring gap of the first coil group respectively.
[0013] This application further specifies that: the spacing between adjacent first or second functional holes is ≥8mil, the diameter of the first or second functional hole includes 6-10mil, and the first and second functional holes include through holes or blind holes.
[0014] This application is further configured such that: when the second coil group is wound around the outside of the magnetic column window and alternately arranged with the first coil group, the first coil group includes a first helical layer, the second coil group includes a second helical layer, and the first helical layer and the second helical layer are arranged in parallel spirals on the outside of the magnetic column window.
[0015] This application further specifies that: the connection hole group includes a third functional hole and a fourth functional hole disposed on the first wiring board and the second wiring board, wherein the third functional hole and the fourth functional hole are respectively connected to one end of the first spiral layer and the second spiral layer near the magnetic pillar window, and the other ends of the first spiral layer and the second spiral layer extend to the side of the first wiring board and the second wiring board and are connected to the pins of the first wiring board and the second wiring board.
[0016] According to the second aspect, the technical solution adopted is as follows:
[0017] An electronic device includes a spatial planar transformer as described in any of the above embodiments.
[0018] In summary, compared with the prior art, this application discloses a spatial planar transformer and an electronic device. The spatial planar transformer includes a first wiring board and at least one second wiring board stacked together. A magnetic column window is opened at the center of the first and second wiring boards. At least one first coil group and at least one second coil group are arranged on both the first and second wiring boards. The first coil group is wound around the outside of the magnetic column window, and the second coil group is spaced apart from the first coil group, or the second coil group is wound around the outside of the magnetic column window and alternates with the first coil group. Both the first and second wiring boards are provided with a group of connecting holes. The first coil group on the first wiring board is electrically connected to the second coil group on the second wiring board through the group of connecting holes, and the second coil group on the first wiring board is electrically connected to the first coil group on the second wiring board through the group of connecting holes. That is, through the above configuration, the spatial structure of the planar transformer is optimized and the cost performance of the device is improved. Attached Figure Description
[0019] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.
[0020] Figure 1 This is a schematic diagram of the structure of the first wiring board of the first type of spatial planar transformer of this application;
[0021] Figure 2 This is a schematic diagram of the structure of the second wiring board of the first type of spatial planar transformer in this application;
[0022] Figure 3 This is a schematic diagram of the spatial connection between the first coil group and the second coil group of this application;
[0023] Figure 4This is a schematic diagram of the structure of the first wiring board of the second type of spatial planar transformer of this application;
[0024] Figure 5 This is a schematic diagram of the structure of the second wiring board of the second type of spatial planar transformer in this application. Detailed Implementation
[0025] Exemplary embodiments will now be described in detail, examples of which are illustrated in the accompanying drawings. When the following description relates to the drawings, unless otherwise indicated, the same numerals in different drawings denote the same or similar elements. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with this application. Rather, they are merely examples of apparatuses and methods consistent with some aspects of this application as detailed in the appended claims.
[0026] It should be noted that, in this document, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes that element. Furthermore, components, features, and elements with the same names in different embodiments of this application may have the same meaning or different meanings, the specific meaning of which must be determined by its interpretation in that specific embodiment or further in conjunction with the context of that specific embodiment.
[0027] It should be understood that the specific embodiments described herein are merely illustrative of this application and are not intended to limit this application.
[0028] In the following description, the use of suffixes such as "module," "part," or "unit" to denote elements is solely for the purpose of illustrative purposes and has no specific meaning in itself. Therefore, "module," "part," or "unit" may be used interchangeably.
[0029] In the description of this application, it should be noted that the terms "upper," "lower," "left," "right," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing this application 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, and therefore should not be construed as a limitation on this application. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.
[0030] The technical solutions shown in this application will be described in detail below through specific embodiments. It should be noted that the order of description of the following embodiments is not intended to limit the priority of the embodiments.
[0031] Please refer to Figures 1 to 3 The spatial planar transformer of this application has a first wiring board 1 and at least one second wiring board 2 stacked together. A magnetic column window 3 is provided at the center of the first wiring board 1 and the second wiring board 2. At least one first coil group 4 and a second coil group 5 are arranged on the first wiring board 1 and the second wiring board 2. The first coil group 4 is wound around the outside of the magnetic column window 3. The second coil group 5 is spaced apart from the first coil group 4. A connection hole group 6 is provided on the first wiring board 1 and the second wiring board 2. The first coil group 4 on the first wiring board 1 is electrically connected to the second coil group 5 on the second wiring board 2 through the connection hole group 6, and the second coil group 5 on the first wiring board 1 is electrically connected to the first coil group 4 on the second wiring board 2 through the connection hole group 6.
[0032] The spatial planar transformer has a magnetic column window 3 at the center of the first wiring board 1 and the second wiring board 2 to accommodate magnetic columns or magnetic core assemblies. The magnetic column windows 3 of the first wiring board 1 and the second wiring board 2 are concentrically arranged, and the first wiring board 1 and at least one second wiring board 2 are stacked to form a multi-layered spatial structure layout, so as to accommodate more winding coils in a limited volume.
[0033] The second coil group 5 is spaced apart from the first coil group 4 to ensure the magnetic field distribution on the first wiring board 1, reduce magnetic field interference and uneven coupling between the winding coils, and provide a connection hole group 6 on the first wiring board 1 and the second wiring board 2 so that the first coil group 4 on the first wiring board 1 can be electrically connected to the second coil group 5 on the second wiring board 2 to form a continuous winding coil. If this winding coil is set as a primary winding, the second coil group 5 on the first wiring board 1 is electrically connected to the first coil group 4 on the second wiring board 2 through the connection hole group 6 to form a secondary winding, thereby ensuring tight coupling between the windings on the first wiring board 1 and the second wiring board 2.
[0034] Among them, the connection hole group 6 not only serves as an electrical connection path, but also provides a channel for heat conduction to a certain extent. Especially in high-power application scenarios, it helps to guide the heat of the planar transformer from the inside to the outside for heat dissipation.
[0035] Unlike the spiral wiring in related technologies, the planar transformer of this application arranges the primary and secondary windings in layers through the first coil group 4 and the second coil group 5 across the structure and connects them electrically through the connecting hole group 6. Through this alternating arrangement, the primary and secondary windings are distributed on different wiring boards, that is, on the first wiring board 1 and at least one second wiring board 2, forming an efficient electromagnetic coupling path. This frees up the coil arrangement space on a single wiring board, reduces the wiring difficulty, and the layered arrangement of the primary and secondary windings and the electrical connection through the connecting hole group 6 not only improves the space utilization of the wiring board, but also enhances the magnetic coupling strength between the windings, reduces the mutual inductance interference of the winding circuit, and optimizes the electrical performance of the planar transformer.
[0036] Furthermore, based on the first coil group 4 and the second coil group 5 on the first wiring board 1 and the second wiring board 2, the ratio of the number of coil turns of the primary winding and the secondary winding can be adjusted to meet different voltage transformation requirements, thereby enabling the planar transformer structure to be adapted to applications of various power levels and frequency ranges, and improving the cost-effectiveness of the device.
[0037] It should be noted that both the first wiring board 1 and the second wiring board 2 can be PCB boards, and the PCB board material can be a high thermal conductivity material such as an aluminum substrate or a ceramic substrate.
[0038] In the specific implementation process, the first coil group 4 has a ring structure design with a wiring gap Q, and the second coil group 5 has a rectangular structure design. The wiring gap Q is designed to face away from the second coil group 5, and the connecting hole group 6 can be located on the side of the second coil group 5 and at the wiring gap of the first coil group 4, respectively. Thus, the first coil group 4 and the second coil group 5 do not need to avoid through holes on the first wiring board 1 and the second wiring board 2. That is, the first coil group 4 and the second coil group 5 are regularly arranged with the connecting hole group 6, thereby optimizing the spatial layout of the planar transformer, meeting the miniaturization design of the device, and making it suitable for application scenarios with strict requirements for compactness and electromagnetic compatibility.
[0039] Furthermore, the first coil group 4 includes several first single-turn wire layers 41, and the second coil group 5 includes the same number of second single-turn wire layers 51 as the first single-turn wire layers 41, so as to ensure that the first coil group 4 on the first wiring board 1 and the second coil group 5 on the second wiring board 2 form a continuous winding coil. The several first single-turn wire layers 41 are arranged sequentially from the vicinity of the magnetic post window 3 to the distance from the magnetic post window 3. At the same time, the first single-turn wire layers 41 are concentrically designed to form a first coil group 4 with a ring structure having a wiring gap Q.
[0040] It is understandable that the number of first single-turn layers 41 of the first coil group 4 on the first wiring board 1 is different from the number of first single-turn layers 41 of the first coil group 4 on the second wiring board 1, that is, the ratio of the number of coil turns of the primary winding to the number of coil turns of the secondary winding is not 1.
[0041] The connecting hole group 6 includes several first functional holes 61 and second functional holes 62 arranged linearly on the first wiring board 1 and the second wiring board 2. The first functional holes 61 connect to the first single-turn wire layer 41, and the second functional holes 62 connect to the beginning and end of the second single-turn wire layer 51. Combined with the aforementioned first coil group 4 having a ring structure design with wiring gap Q and the second coil group 5 having a rectangular structure design, the wiring design of the planar transformer on the first wiring board 1 and the second wiring board 2 does not need to consider the problem of avoiding through holes in related technologies, and can also avoid the coil bending due to avoiding through holes, thereby optimizing the spatial layout of the planar transformer and meeting the miniaturization design of the device.
[0042] The design of the first functional hole 61 and the second functional hole 62 being far away from the magnetic pillar window 3 effectively avoids the adverse effects of the opening of the holes on the withstand voltage performance of the magnetic pillar, and also eliminates the need to add other insulating media to the magnetic pillar (such as high-temperature tape or insulating sheet wrapped around the magnetic pillar), thereby reducing the cost of raw materials and manufacturing processes for the device.
[0043] Preferably, the projections of the first functional hole 61 on the first wiring board 1 and the second functional hole 62 on the second wiring board 2, and the projections of the first functional hole 61 on the second wiring board 2 and the second functional hole 62 on the first wiring board 1 in the direction perpendicular to the working surfaces of the first wiring board 1 and the second wiring board 2, coincide. This regular arrangement of the functional holes on the first wiring board 1 and the second wiring board 2, and the design of the overlapping functional holes, ensures that the functional connection between the first wiring board 1 and the second wiring board 2 is achieved in the shortest path, reducing the complex layout of the wires, thereby maximizing the use of the limited wiring board area, optimizing the functional space, and facilitating the electrical connection between the first coil group 4 on the first wiring board 1 and the second coil group 5 on the second wiring board 2, as well as the electrical connection between the second coil group 5 on the first wiring board 1 and the first coil group 4 on the second wiring board 2.
[0044] It should be noted that the first single-turn wire layer 41 on the first wiring board 1 and the second single-turn wire layer 51 on the second wiring board 2 form a continuous winding coil through the connecting hole group 6. Specifically, the first single-turn wire layer 41 on the first wiring board 1 is connected to the second single-turn wire layer 51 on the second wiring board 2 through the first functional hole 61 on the first wiring board 1 and the second single-turn wire layer 51 on the second wiring board 2 through the second functional hole 62 on the second wiring board 2 to form a continuous winding coil. The output / input terminal 34a of this winding coil extends to the side of the first wiring board 1 and is connected to the PIN 1a of the first wiring board 1.
[0045] Similarly, the second single-turn wire layer 51 on the first wiring board 1 is connected to the first single-turn wire layer 41 on the second wiring board 2 through the second functional hole 62 on the first wiring board 1 to form a continuous winding coil. The output / input terminal 34b of this winding coil extends to the side of the first wiring board 2 and is connected to the PIN 2a of the first wiring board 2.
[0046] Therefore, the first coil group 4 and the second coil group 5 are arranged in layers based on the first wiring board 1 and the second wiring board 2 through the first single-turn wire layer 41 and the second single-turn wire layer 51, and are electrically connected through the first functional hole 61 and the second functional hole 62. Through this alternating arrangement, the winding coils are distributed on different wiring boards, that is, on the first wiring board 1 and at least one second wiring board 2, forming an efficient electromagnetic coupling path. This frees up the coil arrangement space on a single wiring board, reduces the wiring difficulty, not only improves the space utilization of the wiring board, but also enhances the magnetic coupling strength between windings, reduces the mutual inductance interference of the winding circuit, and optimizes the electrical performance of the planar transformer.
[0047] Optionally, the spacing between adjacent first functional holes 61 or second functional holes 62 is ≥8 mil to ensure that sufficient electrical insulation distance can still be provided under the high-density wiring conditions of the first wiring board 1 and the second wiring board 2, avoiding electrical interference or short circuit risks. This spacing setting can also avoid process defects such as hole wall cracking or thermal stress concentration during the machining or drilling process between functional holes, thereby improving the manufacturing reliability of the wiring board.
[0048] The diameter of the first functional hole 61 or the second functional hole 62 is 6-10 mil.
[0049] The spacing and aperture design of the first functional hole 61 or the second functional hole 62 can effectively reduce the resistance and inductance loss in the conductive path and improve the efficiency of the first coil group 4 and the second coil group 5.
[0050] Preferably, the diameter of the first functional hole 61 or the second functional hole 62 includes 8 mil.
[0051] Of course, the spacing and aperture design of the first functional hole 61 or the second functional hole 62 in this application are not limited to this, and can be adapted to meet environmental needs, which will not be elaborated here.
[0052] In the specific implementation process, the first functional hole 61 or the second functional hole 62 includes a through hole or a blind hole.
[0053] On the other hand, reference Figure 4 and Figure 5The spatial planar transformer has a first wiring board 1 and at least one second wiring board 2 stacked together. A magnetic column window 3 is provided at the center of the first wiring board 1 and the second wiring board 2. At least one first coil group 4 and a second coil group 5 are arranged on the first wiring board 1 and the second wiring board 2. The first coil group 4 is wound around the outside of the magnetic column window 3, and the second coil group 5 is wound around the outside of the magnetic column window 3 and is arranged alternately with the first coil group 4. Both the first wiring board 1 and the second wiring board 2 are provided with a connection hole group 6. The first coil group 4 on the first wiring board 1 is electrically connected to the second coil group 5 on the second wiring board 2 through the connection hole group 6, and the second coil group 5 on the first wiring board 1 is electrically connected to the first coil group 4 on the second wiring board 2 through the connection hole group 6.
[0054] The design of the first coil group 4 of the spatial planar transformer being wound on the outside of the magnetic column window 3, and the second coil group 5 being wound on the outside of the magnetic column window 3 and alternately arranged with the first coil group 4, maximizes the effective wiring space of the wiring board and improves the space utilization of the transformer. In addition, the alternating arrangement of the first coil group 4 and the second coil group 5 makes the winding arrangement of the planar transformer compact, which can optimize the magnetic flux distribution of the device, reduce the leakage inductance of the device, increase the coupling ability, and thus improve the device performance.
[0055] Preferably, the first coil group 4 includes a first helical layer 43, and the second coil group 5 includes a second helical layer 44. The first helical layer 43 and the second helical layer 44 are arranged in parallel spirals on the outside of the magnetic column window 3.
[0056] Additionally, the connection hole group 6 includes a third functional hole 63 and a fourth functional hole 64 disposed on the first wiring board 1 and the second wiring board 2, wherein the third functional hole 63 and the fourth functional hole 64 are respectively connected to one end of the first spiral layer 43 and the second spiral layer 44 near the magnetic pillar window 3, and the other ends of the first spiral layer 43 and the second spiral layer 44 extend to the side of the first wiring board 1 and the second wiring board 2 and are connected to the pins of the first wiring board 1 and the second wiring board 2.
[0057] That is, the first spiral layer 43 on the first wiring board 1 of the planar transformer is connected to the second spiral layer 44 on the second wiring board 2 through the third functional hole 63 on the first wiring board 1 through the fourth functional hole 64 on the second wiring board 2 to form a continuous winding coil. The second spiral layer 44 on the first wiring board 1 is connected to the first spiral layer 43 on the second wiring board 2 through the fourth functional hole 64 on the first wiring board 1 through the third functional hole 63 on the second wiring board 2 to form a continuous winding coil.
[0058] Therefore, the first coil group 4 and the second coil group 5 are arranged in layers based on the first wiring board 1 and the second wiring board 2 through the first helical layer 43 and the second helical layer 44, and are electrically connected through the third functional hole 63 and the fourth functional hole 64. With this arrangement, the winding coils are distributed on different wiring boards, that is, on the first wiring board 1 and at least one second wiring board 2, forming an efficient electromagnetic coupling path. This frees up the coil arrangement space on a single wiring board, reduces the wiring difficulty, improves the space utilization of the wiring board, meets the requirements of device miniaturization, enhances the magnetic coupling strength between windings, reduces mutual inductance interference of winding circuits, and optimizes the electrical performance of the planar transformer.
[0059] This application also discloses an electronic device, including a spatial planar transformer as described in any of the above embodiments. For other working principles and processes of the electronic device in this embodiment, please refer to the description of the spatial planar transformer in the above embodiment, which will not be repeated here.
[0060] The spatial planar transformer and electronic device provided in this application have been described in detail above. Specific examples have been used to illustrate the principles and implementation methods of this application. It should be noted that the descriptions of each embodiment in this application have different emphases. Parts not described in detail or in a certain embodiment can be referred to the relevant descriptions of other embodiments.
[0061] The above are merely preferred embodiments of this application and do not limit the patent scope of this application. The technical features of the technical solution of this application can be combined arbitrarily. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. Any equivalent structural or procedural transformations made using the content of this application's specification and drawings, or direct or indirect applications in other related technical fields, are also included within the patent protection scope of this application, as long as the combination of these technical features does not contradict each other.
Claims
1. A spatial planar transformer, characterized in that, include: A first wiring board and at least one second wiring board are stacked together; A magnetic pillar window is provided at the center of the first wiring board and the second wiring board. At least one first coil group and a second coil group are arranged on the first wiring board and the second wiring board respectively. The first coil group is wound around the outside of the magnetic pillar window, and the second coil group on the same wiring board is located on one side of the first coil group and is spaced apart from the first coil group. Both the first wiring board and the second wiring board are provided with a group of connecting holes. The first coil group on the first wiring board is electrically connected to the second coil group on the second wiring board through the group of connecting holes, and the second coil group on the first wiring board is electrically connected to the first coil group on the second wiring board through the group of connecting holes. The first coil group on the same wiring board has a ring structure design with a wiring gap, the second coil group has a rectangular structure design, the wiring gap is away from the second coil group, and the connecting hole group is located on the side of the second coil group and at the wiring gap of the first coil group, respectively.
2. The spatial planar transformer as described in claim 1, characterized in that, The first coil group includes a plurality of first single-turn wire layers, the second coil group includes a number of second single-turn wire layers equal to the number of first single-turn wire layers, and the plurality of first single-turn wire layers are arranged sequentially from the magnetic pillar window to the distance from the magnetic pillar window.
3. The spatial planar transformer as described in claim 2, characterized in that, The first single-turn layer on the first wiring board and the second single-turn layer on the second wiring board form a continuous winding coil through the connecting hole group. The output / input terminal of the winding coil extends to the side of the first wiring board and is connected to the pin of the first wiring board.
4. The spatial planar transformer as described in claim 2, characterized in that, The connection hole group includes a plurality of first functional holes and second functional holes arranged linearly on the first wiring board and the second wiring board. The first functional holes and second functional holes are designed to be away from the magnetic pillar window. The first functional holes are connected to the first single-turn wire layer of the portion, and the second functional holes are connected to the beginning and end of the second single-turn wire layer.
5. The spatial planar transformer as described in claim 3, characterized in that, The projections of the first functional hole on the first wiring board and the second functional hole on the second wiring board, and the projections of the first functional hole on the second wiring board and the second functional hole on the first wiring board in a direction perpendicular to the working surfaces of the first and second wiring boards, coincide.
6. The spatial planar transformer as described in claim 4, characterized in that, The spacing between adjacent first or second functional holes is ≥8mil, the diameter of the first or second functional hole is 6-10mil, and the first or second functional hole includes through holes or blind holes.
7. An electronic device, characterized in that, Including the spatial planar transformer as described in any one of claims 1 to 6.