Multilayer printed wiring board and manufacturing method for the same

Abstract

To provide a multilayer printed wiring board with reduced size and weight, in which the deformation at the manufacture is prevented, and a manufacturing method for the same.SOLUTION: A multilayer printed wiring board 100 includes a conductive layer lamination circuit part 110 and an insulating layer lamination circuit part 120. The conductive layer lamination circuit part 110 includes three or more conductive layers 11 to 13, and a first insulating layer 20. The insulating layer lamination circuit part 120 includes two conductive layers 11, 12, the first insulating layer 20, and one or more second insulating layers 40. The first insulating layer 20 is held between any two conductive layers among the three or more conductive layers in the conductive layer lamination circuit part 110. The first insulating layer 20 is held between any two layers among the conductive layers and the second insulating layers 40 in the insulating layer lamination circuit part 120. In each conductive layer, a predetermined wiring pattern is provided.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present disclosure relates to a multilayer printed wiring board and a method for manufacturing the same. [Background technology]

[0002] Improving power density and reducing size and weight are important issues for motor-inverter systems, which are widely used in electric mobility, industrial equipment, etc. These demands are particularly high in the field of mobility, where installation space is severely restricted and weight reduction leads to improved driving range.

[0003] As a means of improving the output density of inverters, a structure is used in which the main circuit wiring that conducts large currents, which previously used bus bars, is replaced with a printed circuit board using thick copper wiring by utilizing low-loss semiconductor devices and high-density mounting technology.

[0004] One possible way to further reduce the size of the device is to place the control circuit and the main circuit on the same board. In this case, a large current would flow through some of the wiring on the board.

[0005] For example, Patent Document 1 discloses a configuration in which an auxiliary substrate is mounted on a copper foil pattern of a printed wiring board, concentrating current flow in areas where heat generation is likely to occur, thereby lowering resistance and suppressing heat generation. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] JP 2018-137343 A Summary of the Invention [Problem to be solved by the invention]

[0007] In the manufacture of printed wiring boards, copper foil is usually placed on both sides of a resin sheet and heated and pressed to form a copper-clad laminate, on which multiple prepregs made by impregnating glass cloth with resin are laminated, and copper foil is further placed on top of the prepregs, which are then heated and pressed to melt the prepregs and bond the copper foil. By repeating this process, a multilayer printed wiring board having multiple copper layers is manufactured. Unnecessary parts of each copper layer are removed, for example, by etching, to form a wiring pattern.

[0008] When arranging the main circuit wiring and the control circuit wiring on the same board for miniaturization, the thickness of the copper layer on the surface wiring needs to be thin in order to mount the fine-pitch components used in the control circuit section, whereas the main circuit section needs to have a thick inner layer in order to conduct a large current.

[0009] Since large currents do not flow through the control circuit section, thick copper wiring is not necessary. However, if the thick copper wiring located on the inner layer of the control circuit section is removed, steps will remain even after the prepreg is laminated and melted, causing problems such as deformation of the board surface, such as dents.

[0010] For this reason, in some cases unnecessary thick copper wiring is left on the inner layer of the control circuit to prevent deformation of the board. However, the weight of the extra thick copper wiring limits the possibility of reducing the weight of the board.

[0011] An object of the present disclosure is to reduce the size and weight of a multilayer printed wiring board and to prevent deformation during its manufacture. [Means for solving the problem]

[0012] The multilayer printed wiring board of the present disclosure includes a conductor layer laminate circuit section and an insulating layer laminate circuit section, the conductor layer laminate circuit section includes three or more conductor layers and a first insulating layer, the insulating layer laminate circuit section includes two conductor layers, a first insulating layer, and one or more second insulating layers, a first insulating layer is sandwiched between any two of the three or more conductor layers in the conductor layer laminate circuit section, and a first insulating layer is sandwiched between any two of the conductor layers and the second insulating layer in the insulating layer laminate circuit section, and the conductor layers are provided with a predetermined wiring pattern. Effect of the Invention

[0013] According to the present disclosure, it is possible to reduce the size and weight of a multilayer printed wiring board, and to prevent deformation during its manufacture. [Brief description of the drawings]

[0014] [Figure 1] 1 is a schematic perspective view showing a multilayer printed wiring board according to a first embodiment. [Diagram 2] FIG. 1 is a schematic perspective view showing a conventional multilayer printed wiring board. [Diagram 3] 2 is a top view of the multilayer printed wiring board 100 of FIG. [Figure 4] FIG. 2 is a flow diagram showing an example of a method for manufacturing the multilayer printed wiring board according to the first embodiment. [Diagram 5] 4 is a flow diagram showing another example of the method for manufacturing the multilayer printed wiring board according to the first embodiment. FIG. [Figure 6] FIG. 11 is a schematic perspective view showing a multilayer printed wiring board according to a second embodiment. [Figure 7] FIG. 11 is a schematic perspective view showing a multilayer printed wiring board according to a third embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] The present disclosure relates to a technology for reducing the size and weight of a multilayer printed wiring board used as a power conversion device or the like that conducts a large current.

[0016] Hereinafter, the multilayer printed wiring board according to the present disclosure will be described with reference to the drawings. In the drawings used in this specification, the same or corresponding components are denoted by the same or similar reference numerals, and repeated description of these components may be omitted.

[0017] [Embodiment 1] 1 is a schematic perspective view showing a multilayer printed wiring board according to embodiment 1. In the following description, the upper surface in the figure is called the "upper surface" and the lower surface is called the "lower surface."

[0018] The multilayer printed wiring board 100 shown in this figure has a copper layer 11 on the upper surface and a copper layer 12 on the lower surface, as well as a copper layer 13 between the copper layer 11 and the copper layer 12. The multilayer printed wiring board 100 has a structure in which six wiring board layers are stacked in total. An insulating layer 20 is provided between each of the copper layers 11, 12, and 13. In other words, the copper layers 11, 12, and 13 and the insulating layer 20 are stacked alternately. Electrical connection between the copper layers 11, 12, and 13 in the thickness direction is made through vias 30.

[0019] In addition, although this figure shows a case where the copper layer 13 has four layers, the multilayer printed wiring board of the present disclosure is not limited to the configuration shown in this figure, and the copper layer 13 may have three or less layers, i.e., one layer, two layers, or three layers.

[0020] In this figure, the multilayer printed wiring board 100 is divided into a main circuit section 110 and a control circuit section 120. The copper layer 13 is not arranged inside the control circuit section 120. In an area corresponding to the copper layer 13 of the main circuit section 110, an insulating member 40 having a thickness similar to that of the copper layer 13 is arranged. In other words, the copper layer 13 and the insulating member 40 are arranged at approximately the same position (height) in the thickness direction (height direction in the figure) of the multilayer printed wiring board 100. The insulating member 40 is formed of, for example, a sheet-like resin. The insulating member 40 has a higher melting temperature than the material constituting the insulating layer 20. In addition, since the insulating member 40 is a resin, its thermal conductivity is much lower than that of the copper layer 13.

[0021] The insulating layer 20 (first insulating layer) sandwiched between two copper layers 13 (conductor layers) and the first insulating layer sandwiched between insulating members 40 (second insulating layers) form an integrated, approximately flat layer.

[0022] Furthermore, the conductor layer and the second insulating layer sandwiching the integrated, substantially flat, first insulating layer have substantially the same thickness.

[0023] FIG. 2 is a schematic perspective view showing a conventional multilayer printed wiring board.

[0024] In the multilayer printed wiring board 101 shown in this figure, a copper layer 13 is disposed in a main circuit section 110 and a control circuit section 120. The insulating member 40 in FIG. 1 is not disposed.

[0025] FIG. 3 is a top view of the multilayer printed wiring board 100 of FIG.

[0026] 3, the main circuit section 110 includes a power semiconductor 111, a smoothing capacitor 112, and the like. These are circuits through which a large current flows. The power semiconductor 111 and the smoothing capacitor 112 are electrically connected to each other by a copper layer 11.

[0027] On the other hand, the control circuit unit 120 is equipped with a microcomputer 121, a driver integrated circuit 122 (driver IC), etc. These are circuits through which a relatively small current flows. The microcomputer 121 and the driver integrated circuit 122 are electrically connected by a copper layer 11.

[0028] FIG. 4 is a flow diagram showing an example of a method for manufacturing a multilayer printed wiring board according to this embodiment.

[0029] In this figure, first, copper foil 14 is attached to both sides of resin sheet 21 to prepare copper-clad laminate 50 (step S410). Then, unnecessary portions of copper foil 14 are removed by etching or the like to form a wiring pattern (step S420).

[0030] Next, for example, a high heat resistant resin sheet is placed as the insulating member 40 on the portion located on the inner layer of the control circuit section 120 (step S430). Then, one or more prepregs 22 are laminated on both sides of the insulating member 40, and copper foil 14 is further laminated thereon (step S440). In this case, both the main circuit section 110 and the control circuit section 120 are covered with the prepregs 22 and the copper foil 14. In this state, the resin contained in the prepregs 22 is melted by applying heat and pressure, bonding the copper foil 14 and forming the insulating layer 20 (step S450). The resin contained in the prepregs 22 also penetrates between the copper foil 14 and the insulating member 40.

[0031] The insulating layer 20 includes a resin sheet 21 and a prepreg 22. The insulating layer 20 is a first insulating layer. The insulating member 40 is a second insulating layer. Therefore, the heating in step S450 is performed at a temperature higher than the temperature at which the material of the first insulating layer melts and lower than the temperature at which the material of the second insulating layer melts. Here, the melting temperature does not necessarily mean the melting point due to the nature of the resin, but means the temperature at which it melts and flows. Therefore, it may also indicate a temperature range.

[0032] By repeating the above steps, the multilayer printed wiring board 100 is fabricated.

[0033] When the prepreg 22 contains an epoxy resin, the molding temperature of the prepreg 22 is about 180° C. or less. The epoxy resin contained in the prepreg 22 may be in a semi-cured state. The insulating member 40 needs to be made of a material that does not melt even when the prepreg 22 melts. Therefore, suitable materials for the insulating member 40 include, for example, polyimide, polyamide, polyethylene terephthalate (PET), polyphenylene sulfide (PPS), and the like.

[0034] FIG. 5 is a flow diagram showing another example of the method for manufacturing a multilayer printed wiring board according to the present embodiment.

[0035] In this figure, a copper-clad laminate 50 in which copper foil 14 is attached to both sides of a resin sheet 21, and a copper-clad laminate 60 in which copper foil 14 is attached to one side of the resin sheet 21 and, for example, a high heat-resistant resin sheet is attached as an insulating member 40 to the other side are prepared (step S510). Then, unnecessary parts of the copper foil 14 are removed by etching or the like to form a wiring pattern, and a part of the insulating member 40 located inside the main circuit section 110 is removed (step S520). A prepreg 22 is sandwiched between the copper-clad laminates 50 and 60 and laminated (step S530). This is heated and pressurized to melt the resin contained in the prepreg 22, and the insulating layer 20 is formed together with the resin sheet 21 (step S540). This process is repeated to prepare a multilayer printed wiring board 100.

[0036] The operation of the multilayer printed wiring board 100 of this embodiment will now be described.

[0037] In high-output devices such as power converters, which require compact size, light weight, and high output density, the main circuit that conducts a large current is often composed of a bus bar. Due to the reduction of loss in power elements and the improvement of mounting technology, mounting the main circuit on a printed wiring board has been proposed, which is effective not only in terms of high output density but also in terms of productivity and cost. On the other hand, although control circuits that do not require a relatively large current are also mounted on a printed wiring board, they are usually configured separately from the main circuit board due to different design standards.

[0038] A conventional multilayer printed wiring board 101 shown in Fig. 2 is an example of a case where a main circuit section 110 and a control circuit section 120 are mounted on the same board. A copper layer 13 is arranged inside the board to enable conduction of the large current required for the main circuit section 110. Although the copper layer 13 is not required in the inner layer of the control circuit section 120, removing the wiring in this portion results in a large difference in the total thickness of the copper layers in the entire board between the main circuit section 110 and the control circuit section 120, which causes a problem of dents being formed on the surface of the printed wiring board after processing.

[0039] 1, an insulating member 40 having a similar thickness to the copper layer 13 is disposed inside the control circuit section 120. This makes the thickness uniform across the entire board, preventing dents from forming on the board surface after processing. The insulating member 40 may be, for example, a resin material having a higher heat resistance than the prepreg 22, or a sponge-like member impregnated with resin during a process of heating and pressurizing.

[0040] In this manner, the multilayer printed wiring board 100 of the present embodiment can be made lighter than conventional boards because a certain portion of the copper layer 13 inside the board is replaced with insulating material 40 such as resin.

[0041] In addition, since the resin of the insulating member 40 has a much lower thermal conductivity than the copper layer 13, the heat generated in the main circuit section 110 is less likely to be transmitted to the control circuit section 120. This makes it possible to prevent the control circuit section 120, which is equipped with many components with relatively low heat resistance, from being deteriorated or damaged.

[0042] In this embodiment, copper is given as an example of a conductor, but the conductor according to the present disclosure is not limited to copper, and alloys of silver, gold, platinum, nickel, etc. can be used. This is because all of these alloys have lower electrical resistance and higher thermal conductivity than ordinary resins.

[0043] Furthermore, the resin or the like of the insulating member 40 has a lower density than the alloy used for the conductor, which contributes to making the multilayer printed wiring board 100 lighter. [Embodiment 2] In this embodiment, only the configuration different from the first embodiment will be described.

[0044] FIG. 6 is a schematic perspective view showing a multilayer printed wiring board according to the second embodiment.

[0045] As shown in the figure, in the multilayer printed wiring board 102, the thickness of the upper copper layer 11a and the lower copper layer 12a are thinner than the thickness of the inner copper layer 13. The other configurations are the same as those in the first embodiment.

[0046] The operation of the multilayer printed wiring board 102 of this embodiment will now be described.

[0047] 6, the thickness of the upper copper layer 11a and the lower copper layer 12a are reduced, which allows fine processing of the wiring pattern on the component mounting surface. In addition, the weight of the multilayer printed wiring board can be reduced.

[0048] Components mounted on the control circuit section 120 include microcomputers and the like that have many terminals and require fine-pitch mounting. If the upper copper layer 11a and the lower copper layer 12a are made thicker to conduct the large current required for the main circuit section 110, fine processing of the wiring pattern becomes difficult.

[0049] Therefore, in order to be able to conduct the large current required for the main circuit section 110, it is effective to make the thickness of the internal copper layer 13 relatively large, and to realize the fine wiring pattern required for the control circuit section 120, it is effective to make the thicknesses of the upper copper layer 11a and the lower copper layer 12a relatively small. [Embodiment 3] In this embodiment as well, only the configuration different from the first embodiment will be described.

[0050] FIG. 7 is a schematic perspective view showing a multilayer printed wiring board according to the third embodiment.

[0051] As shown in the figure, the multilayer printed wiring board 103 has a plurality of slits 130 at the boundary between the main circuit section 110 and the control circuit section 120. The other configurations are the same as those in the first embodiment.

[0052] The operation of multilayer printed wiring board 103 of this embodiment will now be described.

[0053] 7 has a plurality of slits 130, which has the effect of suppressing the transfer of heat generated in the main circuit section 110 to the control circuit section 120. In addition, by providing a spatial gap between the main circuit section 110 and the control circuit section 120, it has the effect of improving the insulation between them.

[0054] In the above embodiment, the multilayer printed wiring board is divided into the main circuit section 110 and the control circuit section 120, but the main circuit section 110 and the control circuit section 120 are not limited to circuits having the above functions, and the main circuit section 110 is a circuit section in which a relatively large amount of current flows when current is applied, while the control circuit section 120 is a circuit section in which a relatively small amount of current flows when current is applied. Therefore, the main circuit section 110 can be called the "conductor layer laminated circuit section," and the control circuit section 120 can be called the "insulating layer laminated circuit section."

[0055] The conductor layer laminated circuit portion has a low heat transfer resistance since it contains a relatively large number of conductor layers such as copper layers, whereas the insulating layer laminated circuit portion has a high heat transfer resistance since it contains a relatively large number of resin insulating members, etc.

[0056] The specific configuration of the multilayer printed wiring board according to the present disclosure is not limited to the above-described embodiment, and even if there are design changes and the like within the scope of the present disclosure, they are included in the present disclosure. [Explanation of symbols]

[0057] 11, 11a, 12, 12a, 13: copper layer, 14: copper foil, 20: insulating layer, 21: resin sheet, 22: prepreg, 30: via, 40: insulating member, 50, 60: copper-clad laminate, 100, 101, 102, 103: multilayer printed wiring board, 110: main circuit section, 111: power semiconductor, 112: smoothing capacitor, 120: control circuit section, 121: microcomputer, 122: driver integrated circuit, 130: slit.

Claims

1. A conductor layer laminated circuit portion; An insulating layer laminated circuit portion, The conductor layer laminated circuit portion includes three or more conductor layers and a first insulating layer, The insulating layer laminated circuit portion includes two conductor layers, the first insulating layer, and one or more second insulating layers, the first insulating layer is sandwiched between any two of the three or more conductor layers in the conductor layer laminated circuit portion; the first insulating layer is sandwiched between any two layers of the conductor layer and the second insulating layer in the insulating layer laminated circuit portion; A multilayer printed wiring board, wherein the conductor layer is provided with a predetermined wiring pattern.

2. 2. The multilayer printed wiring board according to claim 1, wherein the first insulating layer sandwiched between the conductor layers and the first insulating layer sandwiched between the second insulating layer or between the second insulating layer and the conductor layer constitute an integrated, approximately flat layer.

3. 3. The multilayer printed wiring board according to claim 2, wherein the conductor layer and the second insulating layer sandwiching the integrated substantially flat first insulating layer have substantially the same thickness.

4. 2. The multilayer printed wiring board according to claim 1, wherein the melting temperature of the material of said second insulating layer is higher than the melting temperature of the material of said first insulating layer.

5. 2. The multilayer printed wiring board according to claim 1, wherein the conductor layers disposed inside the multilayer printed wiring board have a thickness dimension larger than that of the conductor layers disposed on the outer surface of the multilayer printed wiring board.

6. 2. The multilayer printed wiring board according to claim 1, further comprising a slit provided between said conductor layer laminated circuit portion and said insulating layer laminated circuit portion.

7. the first insulating layer includes an epoxy resin; 5. The multilayer printed wiring board of claim 4, wherein the second insulating layer comprises polyimide, polyamide, polyethylene terephthalate, or polyphenylene sulfide.

8. The multilayer printed wiring board of claim 1 , wherein the first insulating layer comprises a prepreg.

9. 10. The multilayer printed wiring board of claim 1, which is a power conversion device.

10. A conductor layer laminated circuit portion; An insulating layer laminated circuit portion, The conductor layer laminated circuit portion includes three or more conductor layers and a first insulating layer, The insulating layer laminated circuit portion includes two conductor layers, the first insulating layer, and one or more second insulating layers, the first insulating layer is sandwiched between any two of the three or more conductor layers in the conductor layer laminated circuit portion; the first insulating layer is sandwiched between any two layers of the conductor layer and the second insulating layer in the insulating layer laminated circuit portion; A method for manufacturing a multilayer printed wiring board, in which a predetermined wiring pattern is provided on the conductor layer, comprising the steps of: The method includes a step of arranging the conductor layer, the first insulating layer, and the second insulating layer at predetermined positions, stacking them, and heating them; The method for manufacturing a multilayer printed wiring board, wherein the heating is performed at a temperature higher than the melting temperature of the material of the first insulating layer and lower than the melting temperature of the material of the second insulating layer.

11. The method for producing a multilayer printed wiring board according to claim 10, further comprising the step of providing the wiring pattern by etching the conductor layer.

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