Power Module

Abstract

The present invention discloses a power module, which includes a circuit board, a chip, a first heat-conducting insulating substrate and a second heat-conducting insulating substrate. The circuit board includes a board body and a metal block, wherein the metal block is embedded in the board body and exposed from a first surface and a second surface opposite to the board body. The chip is arranged on one side of the second surface of the board body corresponding to the metal block, and the chip is electrically and thermally connected to the metal block. The first heat-conducting insulating substrate is located on one side of the first surface of the board body and is arranged on the circuit board. The second heat-conducting insulating substrate is electrically and thermally connected to the chip.

Description

Technical Field

[0001] The invention relates to a power module capable of double-sided heat dissipation. Background Art

[0002] In the past, power semiconductor modules were mainly single-sided power modules; however, with the development of power electronics technology, the power of internal electronic components and systems has also increased, making the heating problem increasingly serious, and single-sided heat dissipation power modules are no longer sufficient.

[0003] For example, in the design of electric vehicles, power modules and drivers have been gradually integrated in recent years to improve system power density. This design is particularly advantageous in limited vehicle space. However, if the heat generated by these components cannot be effectively removed, the operating efficiency of the electric vehicle will be affected and even safety issues will arise. Therefore, how to develop a power module that can effectively achieve heat dissipation in a limited space and under the premise of reducing manufacturing costs has become the goal of relevant industry players. Summary of the invention

[0004] An object of the present invention is to provide a power module which can improve the above-mentioned problems.

[0005] One embodiment of the present invention provides a power module. The power module includes a circuit board, a chip, a first heat-conducting insulating substrate, and a second heat-conducting insulating substrate. The circuit board includes a board body and a metal block, wherein the metal block is embedded in the board body and exposed from a first surface and a second surface opposite to the board body. The chip is arranged on one side of the second surface of the board body corresponding to the metal block, and the chip is electrically and thermally connected to the metal block. The first heat-conducting insulating substrate is located on one side of the first surface of the board body and is arranged on the circuit board. The second heat-conducting insulating substrate is electrically and thermally connected to the chip.

[0006] In order to better understand the above and other aspects of the present invention, embodiments are given below and described in detail with reference to the accompanying drawings: BRIEF DESCRIPTION OF THE DRAWINGS

[0007] Figure 1 is a cross-sectional schematic diagram of a power module according to an embodiment of the present invention;

[0008] Figure 2A A perspective view showing a circuit board according to an embodiment of the present invention from a bottom perspective;

[0009] Figure 2B A three-dimensional diagram showing a circuit board according to an embodiment of the present invention from a top perspective;

[0010] Figure 2C is a three-dimensional diagram of a chip according to an embodiment of the present invention;

[0011] Figure 3 is a cross-sectional schematic diagram of a power module according to another embodiment of the present invention;

[0012] Figure 4 FIG. 4 is a cross-sectional schematic diagram of a power module according to another embodiment of the present invention.

[0013] Explanation of symbols

[0014] 100, 200, 300...Power modules

[0015] 200S1, 300S1…The first side of the power module

[0016] 200S2, 300S2… Second side of the power module

[0017] 110, 210…circuit board

[0018] 111, 211…Plate body

[0019] 111a, 211a ... the first surface of the plate

[0020] 111b, 211b ... the second surface of the plate

[0021] 112…Metal block

[0022] 113…Metal layer

[0023] 114, 214…gate drive wiring layer

[0024] 114a, 214a…local metal layer

[0025] 114L…Layout

[0026] 114P...Welding pad

[0027] 115…Power wiring layer

[0028] 115A…First surface terminal

[0029] 115B…Second surface terminal

[0030] 120, 120A, 120B, 120C, 120D...chip

[0031] 120R…Chip placement area

[0032] 121…first electrode

[0033] 122…Second electrode

[0034] 123…Third electrode

[0035] 130…first thermally conductive insulating substrate

[0036] 131…First insulation layer

[0037] 132…First conductor layer

[0038] 140…second thermally conductive insulating substrate

[0039] 141…Second insulation layer

[0040] 142…Second conductor layer

[0041] 150…Electronic components

[0042] 150A...Driver chip

[0043] 150B…Other components

[0044] 160…Passive components

[0045] 270…First lead frame

[0046] 280…Second lead frame

[0047] 290…Third lead frame

[0048] HS…Heat source

[0049] P1, P2, P3, P4…path

[0050] R1…First wiring area

[0051] R2…Second wiring area DETAILED DESCRIPTION

[0052] The following will illustrate multiple embodiments of the present invention with the accompanying drawings. For the sake of clarity, many practical details will be described together in the following description. However, it should be understood that these practical details should not be used to limit the present invention. That is to say, in some embodiments of the present invention, these practical details are not necessary. In addition, in order to simplify the drawings, some existing conventional structures and elements will be illustrated in a simple schematic manner in the drawings. And, unless otherwise indicated, the same element symbols in different drawings can be regarded as corresponding elements. In addition, in the drawings, for the sake of clarity, the sizes of layers, films, plates, regions or substrates are enlarged. The drawings of these drawings are to clearly express the connection relationship between the elements in these embodiments, rather than to show the actual size of each element, or its proportional relationship.

[0053] It should be understood that when an element such as a layer, film, plate, region, or substrate is referred to as being "on" or "connected to" another element, it can be directly on or connected to another element, or there can be intervening elements. Conversely, when an element is referred to as being "directly on" or "directly connected to" another element, there are no intervening elements. In addition, "connected" can refer to physical and / or electrical connections. Furthermore, "electrically connected" or "coupled" can indicate the presence of other elements between two elements.

[0054] Exemplary embodiments will be described below with reference to cross-sectional views which are schematic diagrams of idealized embodiments. Variations in the drawings as a result of, for example, manufacturing techniques and / or tolerances are foreseeable. The embodiments described herein should not be limited to the specific shapes of the regions as shown, but include deviations, for example, caused by manufacturing. For example, a flat region shown in the drawings may generally have rough and / or nonlinear features. Therefore, the regions shown in the drawings are schematic in nature, and their shapes are not intended to imply their precise shapes, nor to limit the present invention.

[0055] Figure 1 is a schematic cross-sectional view of a power module 100 according to an embodiment of the present invention. Figure 2A The circuit board 110 is a three-dimensional view from a bottom perspective according to an embodiment of the present invention. Figure 2B The circuit board 110 according to an embodiment of the present invention is shown in a three-dimensional diagram from a top perspective. Figure 2C is a three-dimensional diagram of a chip 120 according to an embodiment of the present invention.

[0056] Please refer to Figure 1 The power module 100 includes a circuit board 110, a chip 120, a first heat-conducting insulating substrate 130, and a second heat-conducting insulating substrate 140. The power module 100 can be integrated into a power conversion system such as an inverter, such as an inverter of an electric vehicle or a hybrid electric vehicle (EV / HEV), but the present invention is not limited thereto.

[0057] The circuit board 110 is, for example, a direct bonded copper (DBC) substrate or a direct plated copper (DPC) substrate. Figure 1 , Figure 2A and Figure 2BThe circuit board 110 includes a board body 111, and wiring layers (shown as including a gate drive wiring layer 114 and a power wiring layer 115) distributed on a first surface 111a and a second surface 111b opposite to the board body 111, wherein the material of the board body 111 is, for example, ceramic, and the wiring layers 114 and 115 are, for example, copper layers. In other embodiments, the circuit board 110 may be other types of circuit boards, and the board body 111 and the wiring layers 114 and 115 may be other appropriate materials. For example, the material of the board body 111 may also be glass fiber (such as FR4 epoxy glass cloth laminate, etc.) or ceramic (such as aluminum oxide or aluminum nitride, etc.).

[0058] In addition, the circuit board 110 further includes a metal block 112, which is embedded in the board body 111 and exposed from the first surface 111a and the second surface 111b of the board body 111. For example, the board body 111 has a through hole penetrating the first surface 111a and the second surface 111b, and the metal block 112 is embedded in the through hole.

[0059] The chip 120 is disposed on one side of the second surface 111b of the board 111 at a position corresponding to the metal block 112, and is connected to the metal block 112, and the connection includes electrical connection and thermal connection. The chip 120 (shown as including chips 120A and 120B) can be a power chip, such as an insulated gate bipolar transistor (IGBT), a metal-oxide-semiconductor field effect transistor (MOSFET) or a diode.

[0060] The first heat-conducting insulating substrate 130 and the second heat-conducting insulating substrate 140 are respectively located on one side of the first surface 111a and the second surface 111b of the board body 111 and are disposed on the circuit board 110, and the second heat-conducting insulating substrate 140 is further electrically and thermally connected to the chip 120. The first heat-conducting insulating substrate 130 and the second heat-conducting insulating substrate 140 are respectively thermally connected to the chip 120, so that the heat generated by the heat source HS of the chip 120 is effectively transferred out by double-sided heat dissipation.

[0061] The first heat-conductive insulating substrate 130 is, for example, a copper-clad ceramic substrate or a directly electroplated copper ceramic substrate. In detail, the first heat-conductive insulating substrate 130 may include a first insulating layer 131 and two first conductor layers 132, the two first conductor layers 132 are respectively disposed on opposite sides of the first insulating layer 131, and one of the first conductor layers 132 is connected to the metal block 112 (including thermal connection and electrical connection), and the other first conductor layer 132 may be thermally connected to an additional heat dissipation device to further improve the heat dissipation efficiency, but the present invention is not limited thereto. In other embodiments, the first heat-conductive insulating substrate 130 is, for example, an insulated metal substrate (IMS), and the other first conductor layer 132 may be omitted from being disposed on the other side.

[0062] Please refer to Figure 1 , the power module 100 may further include a metal layer 113, which is formed on the first surface 111a of the board 111 at a position corresponding to the metal block 112. In this way, the chip 120 can be thermally connected to the first thermally conductive insulating substrate 130 through the metal block 112 and the metal layer 113. Generally speaking, the thickness of the metal block 112 is greater than that of the metal layer 113. For example, the thickness of the metal block 112 may be greater than 500μm, and the thickness of the metal layer 113 may be less than 500μm. Here, the metal layer 113 may be selectively provided according to design requirements. In other embodiments, the provision of the metal layer 113 may be omitted, and the chip 120 may be directly thermally connected to the first thermally conductive insulating substrate 130 through the metal block 112.

[0063] On the other hand, the second heat-conductive insulating substrate 140 is, for example, a copper-clad ceramic substrate or a directly electroplated copper ceramic substrate. In detail, the second heat-conductive insulating substrate 140 may include a second insulating layer 141 and two second conductor layers 142, the two second conductor layers 142 are respectively disposed on opposite sides of the second insulating layer 141, and one of the second conductor layers 142 is connected to the chip 120 (including thermal connection and electrical connection), and the other second conductor layer 142 can be thermally connected to an additional heat dissipation device to further improve the heat dissipation efficiency, but the present invention is not limited thereto. In other embodiments, the second heat-conductive insulating substrate 140 is, for example, an insulating metal plate, and the other second conductor layer 142 on the other side can be omitted.

[0064] Through the above configuration, the first thermally conductive insulating substrate 130 and the second thermally conductive insulating substrate 140 can be directly or indirectly thermally connected to the chip 120 respectively, and the heat generated by the heat source HS can be transferred from one side of the first thermally conductive insulating substrate 130 along the path P1, and can also be transferred from the second thermally conductive insulating substrate 140 along the path P2.

[0065] Please refer to Figure 1 , Figure 2A and Figure 2B, the circuit board 110 has adjacent first wiring area R1 and second wiring area R2. The chip 120 is configured in the first wiring area R1. The gate drive wiring layer 114 is electrically connected to the chip 120 and is located in the first wiring area R1. Specifically, the gate drive wiring layer 114 is disposed on the second surface 111b of the board body 111. The power wiring layer 115 is electrically connected to the chip 120 and is located in the second wiring area R2. Specifically, the power wiring layer 115 may include a first surface terminal 115A and a second surface terminal 115B, which are respectively disposed on the first surface 111a and the second surface 111b of the board body 11 to provide power to the chip 120. In the embodiment, the cross-sectional area of ​​the line located in the second wiring area R2 is larger than that of the first wiring area R1. Since the power wiring layer 115 needs to provide current input and output with a larger power, the cross-sectional area of ​​the line of the power wiring layer 115 is larger than that of the gate drive wiring layer 114. For example, the cross-sectional area of ​​the power wiring layer 115 is greater than 10000 μm 2 The cross-sectional area of ​​the gate drive wiring layer 114 is 6000 μm 2 the following.

[0066] In the embodiment, the power module 100 may further include an electronic component 150 (shown as including a driver chip 150A and other components 150B). The electronic component 150 is located in the first wiring region R1. The driver chip 150A may provide a driving signal to the chip 120 through the gate driving wiring layer 114.

[0067] like Figure 2A As shown, the gate drive wiring layer 114 may include a plurality of layout lines 114L and solder pads 114P, and the circuit board 110 also has a chip placement area 120R. Figure 1 , Figure 2A and Figure 2C , the chip 120 may include a first electrode 121, a second electrode 122, and a third electrode 123. When the chip 120 is disposed on one side of the second surface 111b of the board 111, the first electrode 121 is aligned with the welding pad 114P and electrically connected to the welding pad 114P, and the second electrode 122 is aligned with the metal block 112 and electrically connected to the metal block 112. Therefore, the driving chip 150A can give the chip 120 a driving signal on the path P3 through the gate driving wiring layer 114.

[0068] Please refer to Figure 1 and Figure 2B, one of the first conductor layers 132 of the first heat-conducting insulating substrate 130 is further electrically connected to the first surface terminal 115A. In addition, the height between the top surface of the metal layer 113 and the first surface 111a of the board body 111 is consistent with the thickness of the first surface terminal 115A, so as to avoid the metal block 112 having insufficient thickness and having a height difference with the first surface terminal 115A, so that the first conductor layer 132 of the first heat-conducting insulating substrate 130 can smoothly contact the first surface terminal 115A and the metal layer 113 at the same time, ensuring the electrical connection structure between the three.

[0069] Here, the metal layer 113 may be the same metal layer structure as the first surface terminal 115A. For example, the first surface terminal 115A and the metal layer 113 may be a copper layer electroplated on the first surface 111a of the board 111 at the same time, but the present invention is not limited thereto. In another embodiment, the metal layer 113 may be an integral structure with the metal block 112 itself.

[0070] One of the second conductor layers 142 of the second thermally conductive insulating substrate 140 is further electrically connected to the second surface terminal 115B. In addition, in some embodiments, the circuit board 100 may further include a partial metal layer 114a, which is correspondingly disposed between the metal block 112 and the chip 120 (the partial metal layer 114a is shown between the metal block 112 and the chip 120A), so that the third electrode 123 (shown in FIG. Figure 2C ) is consistent with the height of the second surface 111b of the board body 111 to avoid the chip 120 being insufficiently thick and having a height difference with the second surface terminal 115B, so that the second conductor layer 142 of the second thermally conductive insulating substrate 140 can smoothly contact the second surface terminal 115B and the chip 120 at the same time, ensuring the electrical connection structure among the three.

[0071] Here, the local metal layer 114a may be the same metal layer structure as the gate driving wiring layer 114. For example, the gate driving wiring layer 114 and the local metal layer 114a may be copper layers electroplated on the second surface 111b of the board 111 at the same time, but the invention is not limited thereto.

[0072] Through the above configuration, a continuous conductive path P4 can be established in the power module 100, and power can be provided to the chip 120 through the path P4 to operate the chip 120. In addition, since the loop inductances of power input and output can offset each other, the parasitic inductance can be further reduced.

[0073] Since the gate drive wiring layer 114 and the drive chip 150A of the drive chip 120 are directly manufactured on the circuit board 110 in this embodiment, the chip 120 does not need to be electrically connected to the drive circuit by wire bonding as in the conventional design, and the signal transmission distance can be shortened and the parasitic inductance can be reduced. In addition, by designing the metal block 112 to be embedded in the circuit board 110, the alignment of the metal block 112 is easy, which greatly reduces the difficulty of the manufacturing process. The embedded metal block 112 can be used as an electrical and thermal conduction path, and can also avoid the occurrence of short circuits, and can also improve the heat dissipation effect while reducing the volume of the power module 100.

[0074] Moreover, in the embodiment, the circuit with a larger cross-sectional area is arranged in the second wiring area R2, and the circuit in the second wiring area R2 bears a larger power load, so the temperature in this area is higher. However, since most of the heat can be transferred through the first thermally conductive insulating substrate 130 and the second thermally conductive insulating substrate 140, the temperature in the first wiring area R1 can be effectively controlled to prevent the heat from affecting the operation of the driver chip 150A.

[0075] In addition, in the embodiment, some electronic components can also be integrated into the power module 100. Alternatively, in another embodiment, some passive components 160 such as capacitors and inductors can also be integrated into the power module 100. Figure 1 and Figure 2A , other components 150B can be arranged on one side of the second surface 111b of the board body 111 and arranged on the circuit board 110. Other components 150B are, for example, control chips, temperature sensors, etc., and the present invention is not limited to this. For example, when the control chip learns that the temperature is abnormal through the temperature sensor, it can promptly control the driving chip 150A to operate the chip 120 to provide a protection mechanism.

[0076] Please refer to Figure 3 , which is a cross-sectional schematic diagram of a power module 200 according to another embodiment of the present invention. The power module 200 includes a circuit board 210, a first heat-conducting insulating substrate 130, a second heat-conducting insulating substrate 140, a first lead frame 270, a second lead frame 280, and a third lead frame 290. The circuit board 210 includes a board body 211 and a gate drive wiring layer 214. The board body 211 and the gate drive wiring layer 214 are similar to Figure 1 The board body 111 and the gate driving wiring layer 114 of the power module 100. The first thermally conductive insulating substrate 130 and the second thermally conductive insulating substrate 140 are respectively disposed on one side of the first surface 211a and the second surface 211b of the board body 211.

[0077] In addition, when there are multiple chips 120, the circuit board 210 may further include a local metal layer 214a, which is correspondingly disposed between the metal block 112 and the thinner chip 120A to compensate for the height difference caused by the different thicknesses between the chip 120A and the chip 120B.

[0078] and Figure 1 The difference between the power module 100 and the power module 100 mainly lies in the design of the circuit board 210 and the first lead frame 270, the second lead frame 280, and the third lead frame 290. The other identical or similar parts are represented by the same reference numerals and contents and are not repeated here.

[0079] The power module 200 has a first side 200S1 and a second side 200S2 opposite to each other. The first lead frame 270 is disposed on the first side 200S1 of the power module 200 and is electrically connected to the chip 120 to transmit a driving signal to the chip 120. Specifically, the first lead frame 270 can be electrically connected to the chip through a gate driving wiring layer 214 disposed on the second surface 211b of the board 211.

[0080] The second lead frame 280 and the third lead frame 290 are disposed on the second side 200S2 of the power module 200 and are electrically connected to the chip 120 to provide power to the chip 120. Specifically, the second lead frame 280 can be electrically connected to the chip 120 through the second conductor layer 142 of the second thermally conductive insulating substrate 140. The third lead frame 290 can be electrically connected to the chip 120 through the first conductor layer 132 of the first thermally conductive insulating substrate 130 and the metal block 112 of the board body 211.

[0081] Please refer to Figure 4 , which is a cross-sectional schematic diagram of a power module 300 according to another embodiment of the present invention. Figure 3 The power module 300 is similar to the power module 200, in that the first lead frame 270 is disposed on the first side 300S1 of the power module 300, and the second lead frame 280 and the third lead frame 290 are disposed on the second side 300S2 of the power module 300. The difference is that the power module 300 further includes another chip 120C, 120D, which is electrically and thermally connected between the metal block 112 and the first conductor layer 132 of the first thermally conductive insulating substrate 130.

[0082] Through the above configuration, the embedded metal block 112 can serve as an electrical and thermal conduction path, and can simultaneously reduce the volume of the power modules 200 and 300 and improve the heat dissipation effect.

[0083] In summary, in the power module of the embodiment of the present invention, a metal block is directly embedded in the circuit board, so that the metal block serves as an electrical and thermal conduction path. This design can avoid short circuits and improve the heat dissipation effect while reducing the volume of the power module. In addition, a continuous conductive path for providing chip power can be established in the power module, and the loop inductance of the power input and output can offset each other to reduce parasitic inductance.

[0084] Furthermore, in some embodiments, the driver chip for driving the chip and the gate drive wiring layer connecting the driver chip and the chip can be fabricated on the circuit board at the same time, so the chip does not need to be electrically connected to the driving circuit by wire bonding as in the traditional design, and the signal transmission distance can be shortened and the parasitic inductance can be reduced. In addition, the design of burying the metal block in the circuit board makes it easy to align the metal block, greatly reducing the difficulty of the manufacturing process.

[0085] In addition, in some embodiments, the circuit board can be further divided into a first wiring area and a second wiring area. Circuits with a larger cross-sectional area (e.g., a power wiring layer for transmitting power) are arranged in the second wiring area. The circuits in the second wiring area bear a larger power load, so the temperature in this area is higher. However, since most of the heat can be transferred through the first thermally conductive insulating substrate and the second thermally conductive insulating substrate, the temperature in the first wiring area can be effectively controlled to prevent the heat from affecting the operation of electronic components (e.g., chips, driver chips) or circuits (e.g., gate drive wiring layers) located in the first wiring area.

[0086] Although the present invention is disclosed in conjunction with the above embodiments, it is not intended to limit the present invention. A person skilled in the art of the present invention may make various modifications and improvements without departing from the spirit and scope of the present invention. Therefore, the scope of protection of the present invention shall be based on the definition of the attached claims.

Claims

1. A power module, characterized in that: include: A circuit board comprises a board body and a metal block, wherein the metal block is embedded in the board body and exposed from a first surface and a second surface opposite to the board body; A chip is disposed on one side of the second surface of the board body corresponding to the metal block, and the chip is electrically and thermally connected to the metal block; A first heat-conducting insulating substrate is located on one side of the first surface of the board body and is disposed on the circuit board; A second heat-conducting insulating substrate is located on one side of the second surface of the board body and is electrically and thermally connected to the chip, and the chip is located between the board body and the second heat-conducting insulating substrate; as well as A power wiring layer is electrically connected to the chip to provide power to the chip, wherein the power wiring layer includes a first surface terminal and a second surface terminal, which are respectively disposed on the first surface and the second surface of the board body. The power is provided to the chip via a continuous conductive path to make the chip operate. The conductive path passes through the second surface terminal, the second conductor layer of the second thermally conductive insulating substrate, the chip, the metal block, the first conductor layer of the first thermally conductive insulating substrate and the first surface terminal.

2. The power module as claimed in claim 1, wherein the circuit board has a first wiring area and a second wiring area adjacent to each other, the chip is configured in the first wiring area, and the cross-sectional area of ​​the circuit in the second wiring area is larger than the cross-sectional area of ​​the circuit in the first wiring area.

3. The power module as claimed in claim 2, wherein the circuit board further comprises a gate drive wiring layer disposed on the second surface of the board body and electrically connected to the chip, and the gate drive wiring layer is located in the first wiring area. The power module as claimed in claim 2 , wherein the power wiring layer is located in the second wiring area.

5. The power module as claimed in claim 1, wherein the circuit board further comprises a metal layer, which is correspondingly disposed between the metal block and the first conductor layer, and the height of the metal layer from the first surface of the board body is consistent with the thickness of the first surface terminal. The power module as claimed in claim 5 , wherein the metal block and the metal layer are an integrated structure.

7. The power module as claimed in claim 1, wherein the circuit board further comprises a partial metal layer correspondingly disposed between the metal block and the chip so that the height of the chip from the second surface of the board body is consistent with the thickness of the second surface terminal. The power module as claimed in claim 1 , wherein the chip is a power chip. 9 . The power module as claimed in claim 1 , further comprising a temperature sensor located on one side of the second surface of the board body and disposed on the circuit board.

10. The power module of claim 1, wherein the power module has a first side and a second side opposite to each other, and further comprising: A first lead frame is disposed on the first side of the power module and is electrically connected to the chip; A second lead frame is disposed on the second side of the power module and is electrically connected to the chip; as well as The third lead frame is disposed on the second side of the power module and is electrically connected to the chip. 11 . The power module as claimed in claim 10 , wherein the second lead frame is electrically connected to the chip via the second conductor layer. 12 . The power module as claimed in claim 10 , wherein the third lead frame is electrically connected to the chip via the first conductive layer.

13. The power module as claimed in claim 10, wherein the circuit board further comprises a gate drive wiring layer disposed on the second surface of the board body and electrically connected to the chip, and the first lead frame is electrically connected to the chip via the gate drive wiring layer. 14 . The power module as claimed in claim 12 , further comprising another chip electrically and thermally connected between the metal block and the first conductor layer.

15. The power module as claimed in claim 10, wherein the number of the chips is plural, and the circuit board further comprises a local metal layer correspondingly disposed between the metal block and the chips so that the heights of the chips from the second surface of the board body are consistent.

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