Circuit pattern manufacturing method and device

Abstract

Provided is a circuit pattern manufacturing method in which it is possible to form a recess in a circuit pattern without additional steps. The circuit pattern manufacturing method comprises: a pattern formation step for forming a circuit pattern semi-finished product 25 in which circuit conductors 3a patterned by double-sided etching of a copper plate material W are relatively joined by a thin joining part 23; and a circuit formation step for removing the joining part 23 by single-sided etching of the circuit pattern semi-finished product 25, and forming recesses 30 in surfaces of the circuit conductors 3a.

Description

Method and Apparatus for Manufacturing Circuit Pattern

[0001] The present invention relates to a method and an apparatus for manufacturing a circuit pattern to which other members such as electronic components, bus bars, and terminals are attached.

[0002] As a conventional circuit pattern, as disclosed in Patent Document 1, there is a circuit pattern in which a concave portion is provided in a connection terminal for connecting semiconductor elements within a mounting region of semiconductor elements on a wiring board. The concave portion of the connection terminal is formed by etching and is used for positioning the semiconductor elements.

[0003] However, such a concave portion had to be formed by etching in an additional process for the connection terminal.

[0004] Japanese Patent Application Laid-Open No. 2005-353854

[0005] The problem to be solved is that the concave portion on the circuit pattern had to be formed by an additional process.

[0006] The present invention provides a method for manufacturing a circuit pattern, including a pattern forming step of forming a circuit pattern semi-finished product in which circuit conductors patterned by double-sided etching on a material plate are joined at a relatively thin joint portion, and a circuit forming step of removing the joint portion by single-sided etching on the circuit pattern semi-finished product and forming a concave portion on the surface of the circuit conductor.

[0007] The present invention also provides an apparatus for manufacturing a circuit pattern, including a pattern forming apparatus for forming a circuit pattern semi-finished product in which circuit conductors patterned by double-sided etching on a material plate are joined at a relatively thin joint portion, and a circuit forming apparatus for removing the joint portion by single-sided etching on the circuit pattern semi-finished product and forming a concave portion on the surface of the circuit conductor.

[0008] The present invention can form a concave portion in the circuit pattern without adding a process while removing a relatively thin joint portion for connecting circuit conductors to each other.

[0009] Figure 1(A) is a schematic cross-sectional view of a metal-based circuit board according to an embodiment of the present invention, and Figure 1(B) is a schematic cross-sectional view of a metal-based circuit board according to a modified example of the present invention. Figure 2 is a perspective view of a pattern substrate. Figure 3 is a plan view of a circuit pattern. Figure 4 is an enlarged cross-sectional view showing a part of a circuit conductor. Figure 5 is a flowchart showing a method for manufacturing a circuit pattern. Figure 6 is a flowchart showing a method for manufacturing a metal-based circuit board as a post-process of the method for manufacturing a circuit pattern. Figure 7 is a schematic cross-sectional view showing the lamination status of the first laminating apparatus in a pattern forming apparatus. Figure 8 is a schematic cross-sectional view showing the exposure status in the exposure apparatus in a pattern forming apparatus. Figure 9 is a schematic cross-sectional view showing the development status in the developing apparatus in a pattern forming apparatus. Figure 10 is a schematic cross-sectional view showing the etching status in the double-sided etching apparatus in a pattern forming apparatus. Figure 11 is a schematic cross-sectional view showing the alkali peeling status in the peeling apparatus in a pattern forming apparatus. Figure 12 is a schematic cross-sectional view showing the lamination status in the second laminating apparatus in a circuit forming apparatus. Figure 13 is a schematic cross-sectional view showing the single-sided etching status in the single-sided etching apparatus in a circuit forming apparatus. Figure 14 is a perspective view showing the cutting of a circuit pattern from a pattern substrate. Figure 15 is a schematic cross-sectional view showing the transfer of a circuit pattern to a cushioning material. Figure 16 is a schematic cross-sectional view of the cushioning material on which the circuit pattern has been transferred. Figure 17 is a schematic cross-sectional view showing a vacuum heating press used to transfer a circuit pattern to an insulating layer on a metal substrate. Figure 18 is a schematic cross-sectional view of a metal-based circuit board. Figure 19(A) is a schematic cross-sectional view showing a circuit pattern on a protective film cut from a pattern substrate. Figure 19(B) is a schematic cross-sectional view showing a circuit pattern transferred to a cushioning material. Figure 19(C) is a schematic cross-sectional view showing a circuit pattern transferred to an insulating layer on a metal substrate.

[0010] One embodiment of the method for manufacturing a circuit pattern comprises pattern forming steps S1 to S5 and circuit forming steps S6 to S10. Pattern forming steps S1 to S5 involve double-sided etching of a material plate W to form a semi-finished circuit pattern 25 in which patterned circuit conductors 3a are joined by relatively thin joints 23. Circuit forming steps S6 to S10 involve single-sided etching of the semi-finished circuit pattern 25 to remove the joints 23 and form recesses 30 on the surface of the circuit conductors 3a.

[0011] In single-sided etching, the intermediate portion 3b of the cross-section of the circuit conductor 3a in the layer direction is formed into a bulging shape in a direction intersecting the layer direction, and the bulging shape may be made into a smooth surface in the layer direction.

[0012] In the pattern formation steps S1 to S5, a semi-finished circuit pattern 25 may be formed in which a tongue portion 23a, shaped to match the coupling portion 23, is provided around the outermost periphery of the portion corresponding to the circuit pattern 3. In this case, in the circuit formation steps S6 to S10, the coupling portion 23 may be removed and the tongue portion 23a may be removed along with the formation of the recess 30 by single-sided etching.

[0013] In this case, the depth of the recess 30 may be greater than or equal to the thickness of the connecting portion 23 and the tongue portion 23a.

[0014] The circuit pattern manufacturing apparatus comprises a pattern forming apparatus 21 and a circuit forming apparatus 33. The pattern forming apparatus 21 forms a semi-finished circuit pattern 25 in which patterned circuit conductors 3a are joined by relatively thin joints 23 by double-sided etching of a material plate W. The circuit forming apparatus 33 removes the joints 23 and forms recesses 30 on the surface of the circuit conductors 3a by single-sided etching of the semi-finished circuit pattern 25.

[0015] [Metal-Based Circuit Board] Figure 1(A) is a schematic cross-sectional view of a metal-based circuit board according to an embodiment of the present invention, and Figure 1(B) is a schematic cross-sectional view of a metal-based circuit board according to a modified example of the present invention.

[0016] In the following explanation, "layer direction" refers to the thickness direction of the circuit pattern or the direction in which the circuit pattern is stacked relative to the metal base circuit board. The direction intersecting the layer direction (intersecting direction) refers to the plane direction along the surface of the circuit pattern. "Up" refers to the direction of gravity when the circuit pattern is placed horizontally. "Down" refers to the direction of gravity when the circuit pattern is placed horizontally.

[0017] The metal-based circuit board 1 shown in Figure 1(A) is equipped with a thick circuit pattern 3 to meet the needs of high-current applications. This metal-based circuit board 1 is manufactured using a pattern substrate W1, which will be described later. The metal-based circuit board 1 is constructed by laminating a metal substrate 5, an insulating layer 7, and a circuit pattern 3.

[0018] The metal substrate 5 is, for example, a plate-like body made of a single metal or an alloy. Materials that can be used for the metal substrate 5 include aluminum, iron, copper, aluminum alloy, or stainless steel. The metal substrate 5 may further contain nonmetals such as carbon. For example, the metal substrate 5 may contain aluminum compounded with carbon. Furthermore, the metal substrate 5 may have a single-layer structure or a multi-layer structure.

[0019] The metal substrate 5 has high thermal conductivity. For example, copper has a thermal conductivity of 370 to 400 W·m-1·K-1, aluminum has a thermal conductivity of 190 to 220 W·m-1·K-1, and iron has a thermal conductivity of 60 to 80 W·m-1·K-1.

[0020] The metal substrate 5 may or may not be flexible. The thickness of the metal substrate 5 is set, for example, within the range of 1.0 to 3.0 mm.

[0021] Furthermore, the metal-based circuit board 1 can also be configured as a metal-based circuit board using a heat sink-shaped metal substrate.

[0022] An insulating layer 7 is laminated on this metal substrate 5.

[0023] The insulating layer 7 is a plate-like body made of insulating material. In addition to electrically insulating the circuit pattern 3 from the metal substrate 5, it also acts as an adhesive to bond them together. For this reason, resin is generally used for the insulating layer 7.

[0024] The thickness of the insulating layer 7 is set to 60 to 150 μm. This insulating layer 7 is required to have high heat resistance to the high heat generation of the elements mounted on the circuit pattern 3, and high heat transfer properties to transfer this heat to the metal substrate 5. For this reason, it is preferable that the insulating layer 7 further contains an inorganic filler.

[0025] As the matrix resin for the insulating layer 7, for example, epoxy resins such as bisphenol A type epoxy resin, bisphenol F type epoxy resin, and triazine type epoxy resin, and cyanate resins such as bisphenol E type cyanate resin, bisphenol A type cyanate resin, and novolac type cyanate resin can be used individually or in combination of two or more types. In addition, a curing agent such as an amine or phenol resin is used in combination with the epoxy resin. In some cases, two or more curing agents may be mixed from the same amine compound. Furthermore, a catalyst for curing may also be added.

[0026] The inorganic filler contained in the insulating layer 7 is preferably one that has excellent electrical insulation properties and high thermal conductivity. Examples include alumina, silica, aluminum nitride, boron nitride, silicon nitride, magnesium oxide, etc., and it is preferable to use one or more selected from these as the inorganic filler.

[0027] The filling ratio of the inorganic filler in the insulating layer 7 can be appropriately set depending on the type of inorganic filler. For example, the filling ratio of the inorganic filler is preferably 85% by volume or less, and more preferably 30 to 85% by volume, based on the total volume of the matrix resin contained in the insulating layer 7.

[0028] In addition to the matrix resin and inorganic filler described above, the insulating layer 7 may further contain, for example, a coupling agent, a dispersant, and the like.

[0029] In addition, a semi-cured insulating sheet can be used as the insulating layer 7.

[0030] A circuit pattern 3 is layered on top of this insulating layer 7.

[0031] Circuit pattern 3 is a plate-like body made of a conductive material, such as copper. In this embodiment, circuit pattern 3 is made of a circuit copper material with a thickness of 3.0 mm, exceeding 0.8 mm, and is designed to handle high currents.

[0032] This circuit pattern 3 comprises a plurality of electrically independent circuit conductors 3a. The configuration of the plurality of circuit conductors 3a is formed according to the required characteristics of the circuit pattern 3.

[0033] The thickness of each circuit conductor 3a in the layer direction is set to 0.8 to 3.0 mm, depending on the thickness of the circuit pattern 3. However, the thickness of each circuit conductor 3a in the layer direction can also be set outside the above range depending on the specifications of the metal base circuit board 1.

[0034] In the cross-section of each circuit conductor 3a, the intermediate portion 3b in the layer direction bulges out in a direction intersecting the lower surface 3d, which is at least the portion located on the insulating layer 7. In this embodiment, the intermediate portion 3b in the layer direction bulges out in a direction intersecting both the upper surface 3c and the lower surface 3d. Each circuit conductor 3a has a shape in which the same cross-section is continuous in the circumferential direction.

[0035] A recess 30 is formed on the upper surface 3c of the circuit conductor 3a. The recess 30 functions as an alignment mark when mounting other components such as electronic components or busbars, or as a mounting part for press-fitting and attaching terminals.

[0036] The recess 30 has an inverted truncated cone shape, being circular in plan view and inverted trapezoidal in cross-section. Since the recess 30 is formed by etching as described later, the shape of the recess 30 can be appropriately set according to the resist pattern.

[0037] The depth of the recess 30 in the layer direction is set based on the thickness of the connecting portion 23 and the tongue portion 23a, as will be described later. In this embodiment, the depth of the recess 30 is greater than or equal to the thickness of the connecting portion 23 and the tongue portion 23a.

[0038] The middle part 3b of the circuit conductor 3a in the layer direction is an appropriate position between the upper surface 3c and the lower surface 3d of the circuit conductor 3a in the layer direction. The middle part 3b in Fig. 1(A) is located slightly closer to the lower surface 3d than the vertical center of the circuit conductor 3a. The middle part 3b of the modified example in Fig. 1(B) is located slightly closer to the upper surface 3c than the vertical center of the circuit conductor 3a.

[0039] The bulging shape of this middle part 3b is formed by a gently curved surface in the layer direction. The gently curved surface in the layer direction has no sharp peaks (tips) or angular parts such as sharp corners in the intersecting direction with respect to the layer direction, and is continuous as a curved surface in the layer direction. The gently curved surface of this middle part 3b is a convex curved surface in this embodiment.

[0040] The upper and lower surfaces 3e and 3f with respect to the middle part 3b are substantially straight inclined surfaces and are continuous with the middle part 3b. Note that the surfaces 3e and 3f can also be formed in a concave curved surface shape as shown in Fig. 4 described later.

[0041] The lower surface 3d of the circuit conductor 3a in Fig. 1(A) is wider than the upper surface 3c. In the circuit conductor 3a of the modified example in Fig. 1(B), contrary to the circuit conductor 3a in Fig. 1(A), the width of the upper surface 3c is formed wider than the width of the lower surface 3d.

[0042] In the circuit conductor 3a of Fig. 1(A), the interval between the middle parts 3b of adjacent circuit conductors 3a is set to about 2 mm, and the interval between the lower surfaces 3d is about 2.1 mm. In the circuit conductor 3a of Fig. 1(B), when the interval between the bulging surfaces 3b of the circuit conductor 3a is set to about 2 mm, the interval between the lower surfaces 3d is about 2.2 mm.

[0043] Such a metal base circuit board 1 has a bulging shape in which the middle part 3b in the layer direction of the circuit conductor 3a is a convex curved surface with a gently curved surface in the layer direction as described above.

[0044] Therefore, the cross-sectional area of the circuit conductor 3a can be increased by the bulging shape of the middle part 3b of the circuit conductor 3a. Accordingly, the metal base circuit board 1 is easily adaptable to an increase in current and is also advantageous for a large current.

[0045] Since the bulging shape of the circuit conductor 3a is formed by a gently curved surface in the layer direction of the intermediate portion 3b of the circuit conductor 3a, it is possible to suppress a short circuit between adjacent circuit conductors 3a at this portion.

[0046] In the circuit conductors 3a shown in FIGS. 1(A) and 1(B), the width of the lower surface 3d of the circuit conductor 3a laminated on the insulating layer 7 is smaller than the width in the intermediate portion 3b. Therefore, the occurrence of ion migration on the insulating layer 7 between the circuit conductors 3a can be suppressed.

[0047] Since it is possible to suppress a short circuit between adjacent circuit conductors 3a and the occurrence of ion migration, a dense arrangement of the circuit patterns 3 is possible in the metal base circuit board 1. In particular, for the circuit conductor 3a in FIG. 1(A), the width of the lower surface 3d is wider than the width of the upper surface 3c, and the adhesive force to the insulating layer 7 can be made larger than that of the circuit conductor 3a in FIG. 1(B).

[0048] [Pattern Substrate] FIG. 2 is a perspective view of the pattern substrate. FIG. 3 is a plan view of the circuit pattern. FIG. 4 is an enlarged cross-sectional view showing a part of the circuit conductor.

[0049] As shown in FIG. 2, the pattern substrate W1 of this embodiment is formed by laminating a plurality of circuit patterns 3 on a protective sheet 9. The pattern substrate W1 is manufactured by a method for manufacturing a circuit pattern using double-sided etching and single-sided etching as described later.

[0050] The protective sheet 9 is used as it is as a back surface protective film laminated on the back surface of the circuit pattern semi-finished product 25 during single-sided etching performed from the surface of the circuit pattern semi-finished product 25 as described later.

[0051] The circuit pattern 3 is generally as described above. When manufactured by double-sided etching and single-sided etching of wet etching on the copper plate material W, the typical cross-sectional shape is as shown in FIG. 4. The manufacturing method by double-sided etching and single-sided etching will be described later. In FIG. 4, only the intermediate portion 3b on one side in the crossing direction is shown in the cross-section of the circuit conductor 3a.

[0052] In Figure 4, the intermediate portion 3b, which is a curved convex surface, is located in the center between the upper and lower surfaces 3c and 3d of the circuit conductor 3a, or slightly closer to the upper surface 3c (t1 - t2 ≤ t2).

[0053] The upper and lower surfaces 3e and 3f of the bulging intermediate portion 3b are formed in a concave curved shape. The intermediate portion 3b and surfaces 3e and 3f are smooth and continuous in the layer direction without sharp edges on the circumferential surface of the circuit conductor 3a. As described above, the intermediate portion 3b protrudes in a direction that intersects with the upper surface 3c and the lower surface 3d.

[0054] The position of the recess 30 in the circuit conductor 3a in a plan view can be, for example, at the diagonal corner of the circuit conductor 3a. However, the location of the recess 30 can be set as appropriate depending on its purpose.

[0055] A metal-based circuit board 1 can be manufactured using the circuit pattern 3 on this pattern substrate W1.

[0056] [Manufacturing Method for Circuit Patterns and Metal-Based Circuit Boards] Figure 5 is a flowchart showing the manufacturing method for circuit patterns. Figure 6 is a flowchart showing the manufacturing method for metal-based circuit boards as a post-process to the manufacturing method for circuit patterns. In this embodiment, the manufacturing method for circuit patterns and the manufacturing method for metal-based circuit boards are implemented on a continuous line, but these manufacturing methods can also be implemented on separate lines.

[0057] As shown in Figure 5, the method for manufacturing a circuit pattern comprises pattern formation steps S1 to S5 and circuit formation steps S6 to S10.

[0058] The pattern formation steps S1 to S5 involve double-sided etching of the copper foil or copper plate material W as the material plate (see Figures 7 to 10). This forms a semi-finished circuit pattern 25 in which the individual circuit conductors 3a constituting the circuit pattern 3 are joined by relatively thin joints 23 (see Figure 11).

[0059] In the circuit formation steps S6 to S10, one-sided etching is performed on the joint portion 23 and the outermost tongue portion 23a of the circuit pattern 3 from one side of the semi-finished circuit pattern 25 (see Figure 13). This creates a bulging shape in the middle portion 3b of the cross-section in the layer direction of each circuit conductor 3a, and obtains a circuit pattern 3 in which the bulging shape becomes a smooth surface in the layer direction.

[0060] The pattern formation steps S1 to S5 are performed by a pattern formation apparatus. The circuit formation steps S6 to S10 are performed by a circuit formation apparatus.

[0061] Figures 7 to 11 are schematic cross-sectional views of a pattern forming apparatus that realizes pattern forming steps S1 to S5, and Figures 12 to 13 are schematic cross-sectional views of a circuit forming apparatus that realizes circuit forming steps S6 to S10.

[0062] Figure 7 is a schematic cross-sectional view showing the lamination process in the first laminating apparatus of the pattern forming apparatus. Figure 8 is a schematic cross-sectional view showing the exposure process in the exposure apparatus of the pattern forming apparatus. Figure 9 is a schematic cross-sectional view showing the development process in the developing apparatus of the pattern forming apparatus. Figure 10 is a schematic cross-sectional view showing the double-sided etching process in the double-sided etching apparatus of the pattern forming apparatus. Figure 11 is a schematic cross-sectional view showing the alkaline peeling process in the alkaline peeling apparatus of the pattern forming apparatus.

[0063] In Figure 5, step S1 is the first film lamination step of the pattern formation process. In this step, film lamination is performed using the first laminating device 11 shown in Figure 7, which is included in the pattern formation apparatus.

[0064] In other words, the copper plate material W is pre-processed to a predetermined size and supplied together with dry films 13a and 13b between the rollers 11a and 11b of the first laminating device 11. As a result, the dry films 13a and 13b are attached to both sides of the copper plate material W. Dry films 13a and 13b with a thickness of about 100 μm are used. However, dry films 13a and 13b with other thicknesses, such as about 40 μm, may also be used.

[0065] Step S2 is the exposure step of the pattern formation process. In this step, the dry films 13a and 13b are exposed using the exposure device 15 shown in Figure 8, which is included in the pattern formation apparatus. Specifically, exposure films 17a and 17b are placed on the dry films 13a and 13b on the front and back sides of the copper plate material W. Then, the exposure device 15 exposes the dry films 13a and 13b through the exposure films 17a and 17b.

[0066] Step S3 is the development step of the pattern formation process. In this step, development is performed using a developing device (not shown) included in the pattern formation apparatus, as shown in Figure 9. That is, the dry films 13a and 13b on the front and back of the copper plate material W exposed in step S2 are developed, and the unhardened portions of the dry films 13a and 13b are removed. As a result, the dry films 13a and 13b remaining after development become the resist pattern 19.

[0067] Step S4 is the double-sided etching step of the pattern formation process. In this step, double-sided etching is performed using the double-sided etching apparatus 21 shown in Figure 10, which is included in the pattern formation apparatus. That is, the double-sided etching apparatus 21 sprays ferric chloride etching solution onto both sides of the copper plate material W via the resist pattern 19. Cupric chloride or alkaline etching solution can also be used as the etching solution. Note that in Figure 10, the double-sided etching apparatus 21 is shown conceptually only. A well-known double-sided etching machine can be used as this double-sided etching apparatus 21.

[0068] Double-sided etching is performed, for example, by spraying at a liquid temperature of 45°C and a spray pressure of 0.4 MPa for about 30 minutes. However, the conditions such as the liquid temperature for double-sided etching can be changed in various ways by setting the joint portion 23 and the tongue portion 23a.

[0069] This double-sided etching process forms a semi-finished circuit pattern 25 in which patterned circuit conductors 3a constituting the circuit pattern 3 are joined by relatively thin joints 23. In the semi-finished circuit pattern 25, a tongue portion 23a with a shape corresponding to the joint 23 is formed on the outermost periphery of the portion 3A corresponding to the circuit pattern 3 in which the circuit conductors 3a are joined by the joints 23.

[0070] The tongue portion 23a is formed in a circumferential manner so as to surround the entire portion 3A corresponding to the circuit pattern 3. The thickness and protrusion dimensions of the tongue portion 23a are formed to be approximately the same as the thickness of the coupling portion 23 and the dimensions spanning between the circuit conductors 3a. However, the thicknesses of the coupling portion 23 and the tongue portion 23a can be made different.

[0071] Step S5 is the alkali stripping step of the pattern formation process. In this step, alkali stripping is performed using an alkali stripping device (not shown) included in the pattern formation apparatus, as shown in Figure 11. That is, after development, the resist pattern 19 corresponding to the circuit pattern 3 is removed by an alkaline solution, and a semi-finished circuit pattern 25 is obtained.

[0072] Figure 12 is a schematic cross-sectional view showing the lamination process in the second laminating apparatus of the circuit formation apparatus. Figure 13 is a schematic cross-sectional view showing the single-sided etching process in the single-sided etching apparatus of the circuit formation apparatus.

[0073] Step S6 is the second film lamination step of the circuit formation process. The second film lamination step, together with the exposure step of step S7 and the development step of step S8, constitutes a sheet lamination process and forms the resist pattern 31 as described later.

[0074] In this second film lamination process, film lamination is performed by the second laminating device 27 shown in Figure 12, which is included in the circuit forming apparatus. Specifically, the semi-finished circuit pattern 25 is supplied between the rollers 27a and 27b of the second laminating device 27 together with the dry film 29 and the protective sheet 9, which is a back surface protective film.

[0075] In this process, the dry film 29 is attached to the surface of the semi-finished circuit pattern 25, and the protective sheet 9, which is a back-side protective film, is attached to the back surface. The front and back sides of the semi-finished circuit pattern 25 can be arbitrarily selected. A dry film 29 with a thickness of approximately 100 μm is used. However, a dry film 29 with a different thickness, such as 40 μm, may also be used.

[0076] Step S7 is the exposure step of the circuit formation process, and step S8 is the development step of the circuit formation process. Steps S7 and S8 are carried out in the same way as steps S2 and S3 of the pattern formation process. Therefore, after the dry film 29 is exposed using an exposure apparatus as shown in Figure 8, the exposed dry film 29 is developed.

[0077] The dry film 29 remaining after development forms the resist pattern 31 shown in Figure 13, with the planned locations for the bonding portion 23, tongue portion 23a, and recess 30 exposed on the surface of one side of the semi-finished circuit pattern 25. A protective sheet 9, which is a back surface protective film, is laminated and attached to the back surface of the other side of the semi-finished circuit pattern 25.

[0078] Step S9 is the single-sided etching step of the circuit formation process. In this step, single-sided etching is performed using the single-sided etching apparatus 33 shown in Figure 13, which is included in the circuit formation apparatus. That is, the single-sided etching apparatus 33 sprays ferric chloride etching solution onto one side of the circuit pattern semi-finished product 25 via the resist pattern 31. Note that in Figure 13, the single-sided etching apparatus 33 is shown conceptually only. A well-known single-sided etching machine can be used as this single-sided etching apparatus 33.

[0079] As with the above, cupric chloride or an alkaline etching solution can also be used as the etching solution. This single-sided etching is performed at a liquid temperature of 45°C and a spray pressure of 0.4 MPa for an etching time of about 5 minutes. However, the conditions such as the liquid temperature for single-sided etching can be changed in various ways depending on the thickness of the bonding portion 23 and the tongue portion 23a and their position in the layer direction. This single-sided etching etches and removes the bonding portion 23 and the tongue portion 23a, and forms the recess 30 (see Figure 19).

[0080] The joint portion 23 and the tongue portion 23a are not completely removed, but are left so that the peripheral surface of each circuit conductor 3a bulges out at the intermediate portion 3b. In this case, as etching progresses, the etching solution will spread evenly across the bulging shape in the layer direction as well.

[0081] Therefore, the bulging surface is formed as an arc-shaped convex curved surface as shown in Figure 4. The shape of the convex curved surface of the intermediate portion 3b can be adjusted by setting the liquid temperature, spray pressure, and etching time. The position of the intermediate portion 3b between the upper surface 3c and the lower surface 3d, the size of the bulging shape, and the width of the upper surface 3c and the lower surface 3d can be adjusted by setting the vertical position and thickness of the joint portion 23 and the tongue portion 23a, as well as the liquid temperature, spray pressure, and etching time for single-sided etching.

[0082] The recess 30 can be formed by single-sided etching, removing the joint portion 23 and the tongue portion 23a without adding any further steps. During this single-sided etching, the formation position of the recess 30 can be precisely set in relation to the joint portion 23 and the tongue portion 23a. As a result, the positional accuracy of the recess 30 on the circuit conductor 3a can be improved. This allows, for example, the recess 30 to be precisely formed in the center of the circuit conductor 3a, thereby improving the heat dissipation of other mounted components.

[0083] Furthermore, since the recess 30 is formed along with the removal of the connecting portion 23 and the tongue portion 23a, it can have a depth at least the same as the thickness of the connecting portion 23 and the tongue portion 23a. However, by continuing single-sided etching after the removal of the connecting portion 23 and the tongue portion 23a, the depth of the recess 30 can be made greater than the thickness of the connecting portion 23 and the tongue portion 23a.

[0084] Therefore, since the depth of the recess 30 can be set based on the thickness of the connecting portion 23 and the tongue portion 23a, it is easy to set the appropriate depth relative to the thickness of the circuit pattern 3 (circuit conductor 3a).

[0085] In this embodiment in particular, single-sided etching creates a bulge shape in the intermediate portion 3b of the cross-section of the circuit conductor 3a in the layer direction, intersecting the layer direction, while also making the bulge shape a smooth surface in the layer direction. Through this single-sided etching, the depth of the recess 30 can be appropriately set.

[0086] Moreover, the recess 30 can be easily and reliably formed by single-sided etching that removes the joint portion 23 and the tongue portion 23a, without intentionally performing partial etching.

[0087] Step S10 is the alkali stripping step of the circuit formation process. In this step, the same process as the alkali stripping step in step S5 is performed. That is, after single-sided etching in step S9, the resist pattern 31 is removed by alkali stripping in the alkali stripping device included in the circuit formation apparatus. As a result, the pattern substrate W1 shown in Figure 2 is obtained as the result. The circuit pattern 3 is attached to the protective sheet 9, which is a back surface protective film, on the pattern substrate W1.

[0088] Using the pattern substrate W1 obtained as shown in Figure 2, the metal base circuit board 1 is completed by the substrate lamination process S11 to S14 shown in Figure 6.

[0089] Figure 14 is a perspective view showing the cutting of a circuit pattern from a pattern substrate. Figure 15 is a schematic cross-sectional view showing the transfer of a circuit pattern to a cushioning material. Figure 16 is a schematic cross-sectional view of the cushioning material on which the circuit pattern has been transferred. Figure 17 is a schematic cross-sectional view showing a vacuum heating press used to transfer a circuit pattern to an insulating layer on a metal substrate. Figure 18 is a schematic cross-sectional view of a metal-based circuit board.

[0090] As shown in Figure 14, one circuit pattern 3 is cut out from the pattern substrate W1, and as shown in Figure 15, the circuit pattern 3 is transferred to the cushioning material 35 on its surface. Next, as shown in Figure 16, the protective sheet 9 is peeled off, and as shown in Figure 17, the circuit pattern 3 is attached to the insulating layer 7 on the metal substrate 5 with the back side of the protective sheet 9 removed. Furthermore, as shown in Figure 18, the cushioning material 35 is peeled off from the surface of the circuit pattern 3, and the circuit pattern 3 is subjected to pressurized heat treatment to complete the metal base circuit board 1.

[0091] Furthermore, in Figure 6, step S11 is the cutting step of the substrate lamination process. In this step, one circuit pattern 3 is cut from the pattern substrate W1 obtained as described above, as shown in Figure 14. In this cutting, the protective sheet 9 is cut, and one circuit pattern 3 is cut out together with the protective sheet 9.

[0092] Step S12 is the transfer process of the substrate lamination process. In this process, as shown in Figure 15, the surface of the circuit pattern 3 is facing the surface of the cushioning material 35, and the circuit pattern 3 is transferred to the cushioning material 35 by pressing. At this time, the relative positions of the individual circuit conductors 3a of the circuit pattern 3 are accurately maintained by the protective sheet 9.

[0093] The cushioning material 35 is made of urethane, for example, with a thickness of 3 to 5 mm. The surface of the cushioning material 35 is provided with an adhesive layer. The surface of the circuit pattern 3 is held in place by adhesion to the adhesive layer on the surface of the cushioning material 35. The adhesive strength of the cushioning material 35 is set higher than the holding force of the circuit pattern 3 by the protective sheet 9. Therefore, by peeling off the protective sheet 9 after pressing, the circuit pattern 3 is transferred to the cushioning material 35 as shown in Figure 16.

[0094] Step S13 is the vacuum heating press step of the substrate lamination process. In this step, as shown in Figure 17, the circuit pattern 3 held by the cushioning material 35 is pressed onto the insulating layer 7 on the metal substrate 5 by vacuum heating press.

[0095] At this time, the cushioning material 35 bends when the adhesive portion of each circuit conductor 3a receives a reaction force from each circuit conductor 3a, and deforms so that the remaining portion of each circuit conductor 3a, excluding the adhesive portion, reaches the insulating layer 7. Due to the elasticity of this cushioning material 35, each circuit conductor 3a can be properly pressed onto the uncured insulating layer 7 during vacuum heating press.

[0096] Therefore, the thickness of the cushioning material 35 is set according to the thickness of the circuit conductor 3a being pressed. That is, the cushioning material 35 is thicker when the circuit conductor 3a is thick, and thinner when the circuit conductor 3a is thin. This relationship between thickness and the elasticity of the cushioning material 35 can be determined by prior experimentation.

[0097] Step S14 is the completion step of the substrate lamination process. In this step, after the insulating layer 7 has solidified, the cushioning material 35 is peeled off. This completes the metal base circuit board 1 shown in Figure 18.

[0098] The relationship between the steps S11 to S14 and the bulge shape is shown in Figures 19(A) to 19(C). Figure 19(A) is a schematic cross-sectional view showing the circuit pattern on the protective film cut from the pattern substrate. Figure 19(B) is a schematic cross-sectional view showing the circuit pattern transferred to the cushioning material. Figure 19(C) is a schematic cross-sectional view showing the circuit pattern transferred to the insulating layer on the metal substrate.

[0099] In step S11, the cutting process causes the lower surface 3d of each circuit conductor 3a of the circuit pattern 3 to be held by the cut protective sheet 9, while the upper surface 3c of each circuit conductor 3a and its recess 30 are exposed.

[0100] In the transfer process of step S12, the individual circuit conductors 3a of the circuit pattern 3 are inverted, the upper surface 3c and recess 30 of each circuit conductor 3a are covered with cushioning material 35, and the lower surface 3d of each circuit conductor 3a is exposed.

[0101] In the vacuum heating press and finishing processes of steps S13 and S14, each circuit conductor 3a is inverted again, and its lower surface 3d is fixed to the insulating layer 7. After the insulating layer 7 hardens, the cushioning material 35 is peeled off using a peeling roller (not shown), exposing the upper surface 3c and recess 30 of each circuit conductor 3a.

[0102] In the completed metal-based circuit board 1, the recesses 30 on the surface of the circuit pattern 3 can be used as alignment marks or mounting areas for terminals when mounting other components such as electronic components or busbars. In this embodiment, since the depth of the recesses 30 is appropriately set, the recesses 30 can be reliably used as alignment marks or mounting areas, enabling secure mounting of other components and terminals.

[0103] As described above, the method for manufacturing the circuit pattern of this embodiment comprises a pattern forming step of forming a semi-finished circuit pattern 25 in which the patterned circuit conductors 3a of the circuit pattern 3 are joined by relatively thin joints 23 by double-sided etching of a copper plate material W, and a circuit forming step of removing the joints 23 by single-sided etching of the semi-finished circuit pattern 25 and forming a recess 30 on a part of the surface of the circuit conductor 3a.

[0104] Therefore, in the circuit pattern manufacturing method of this embodiment, the recess 30 can be formed in the circuit pattern 3 without adding any steps, along with the removal of the joint portion 23 by single-sided etching. At this time, the position of the recess 30 can be accurately set in relation to the joint portion 23 and the tongue portion 23a, and as a result, the positional accuracy of the recess 30 on the circuit conductor 3a can be improved.

[0105] Furthermore, it is possible to easily set an appropriate depth for the recess 30 formed in the circuit pattern 3 relative to the thickness of the circuit pattern 3.

[0106] Furthermore, in this embodiment, the single-sided etching is performed such that the intermediate portion 3b of the cross-section of the circuit conductor 3a in the layer direction is given a bulging shape in a direction intersecting the layer direction, and that this bulging shape is made into a smooth surface in the layer direction.

[0107] This single-sided etching makes it easier and more reliable to set the appropriate depth of the recess 30.

[0108] The pattern formation process forms a semi-finished circuit pattern 25 in which a tongue portion 23a shaped to correspond to a connecting portion 23 is provided around the outermost periphery of a portion 3A corresponding to the circuit pattern 3 of the semi-finished circuit pattern 25. The circuit formation process removes the connecting portion 23 and forms a recess 30, as well as the tongue portion 23a, by single-sided etching.

[0109] Therefore, the depth of the recess 30 is greater than or equal to the thickness of the connecting portion 23 and the tongue portion 23a, making it easier and more reliable to set the appropriate depth.

[0110] The circuit pattern manufacturing apparatus includes a double-sided etching apparatus that forms a semi-finished circuit pattern 25 in which patterned circuit conductors 3a of the circuit pattern 3 are joined by relatively thin joints 23 by double-sided etching of a copper plate material W, and a single-sided etching apparatus that removes the joints 23 and forms recesses 30 on a part of the surface of the circuit conductors 3a by single-sided etching of the semi-finished circuit pattern 25.

[0111] Therefore, in the circuit pattern manufacturing apparatus of this embodiment, it is possible to easily set the appropriate depth of the recess 30 formed in the circuit pattern 3 relative to the thickness of the circuit pattern 3.

[0112] 3 Circuit pattern 3a Circuit conductor 3b Intermediate part 21 Double-sided etching apparatus (pattern forming apparatus) 23 Joint part 23a Tongue part 25 Semi-finished circuit pattern 30 Recess 33 Single-sided etching apparatus (circuit forming apparatus) W Copper plate material (material plate) W1 Pattern substrate S1-S5 Pattern forming process S6-S10 Circuit forming process

Claims

1. A method for manufacturing a circuit pattern, comprising: a pattern forming step of forming a semi-finished circuit pattern in which patterned circuit conductors are joined at relatively thin joints by double-sided etching on a material plate; and a circuit forming step of removing the joints and forming recesses on the surface of the circuit conductors by single-sided etching on the semi-finished circuit pattern.

2. A method for manufacturing a circuit pattern according to claim 1, wherein the single-sided etching is performed to form a bulge shape in the direction intersecting the layer direction of the intermediate portion of the cross-section of the circuit conductor, and to make the bulge shape a smooth surface in the layer direction.

3. A method for manufacturing a circuit pattern according to claim 1 or 2, wherein the pattern forming step comprises forming a circuit pattern semi-finished product having a tongue portion having a shape corresponding to the coupling portion circumferentially on the outermost periphery of the portion corresponding to the circuit pattern of the circuit pattern semi-finished product, and the circuit forming step comprises removing the coupling portion and forming the recess, along with removing the tongue portion, by single-sided etching.

4. A method for manufacturing a circuit pattern according to claim 3, wherein the depth of the recess is greater than or equal to the thickness of the connecting portion and the tongue portion.

5. A circuit pattern manufacturing apparatus comprising: a pattern forming apparatus that forms a semi-finished circuit pattern in which patterned circuit conductors are joined at relatively thin joints by double-sided etching on a material plate; and a circuit forming apparatus that removes the joints and forms recesses on the surface of the circuit conductors by single-sided etching on the semi-finished circuit pattern.

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