Wiring board manufacturing method

Abstract

This wiring board manufacturing method includes: a step for forming a first pattern sheet by forming a conductor pattern in a central region of a surface of a ceramic green sheet; a step for forming a second pattern sheet by forming a glass pattern adjacent to the conductor pattern in a region outside the central region of the surface of the first pattern sheet; a step for forming a first laminate by laminating a plurality of second pattern sheets or laminating a plurality of second pattern sheets and one or more first pattern sheets; a step for forming a second laminate by laminating a restraining sheet, composed of an inorganic composition having a higher sintering start temperature than the ceramic green sheet, on both surfaces in the lamination direction of the first laminate; and a step for sintering the second laminate.

Description

Method for manufacturing a wiring board

[0001] The disclosed embodiments relate to a method for manufacturing a wiring substrate.

[0002] 2. Description of the Related Art Conventionally, a multilayer wiring board has been known in which a plurality of ceramic base materials are used to form multiple layers and wiring is disposed between the layers.

[0003] Japanese Patent Laid-Open No. 7-86743 Japanese Patent Laid-Open No. 2003-78245

[0004] A method for manufacturing a wiring board according to one aspect of the embodiment includes the steps of: forming a conductive pattern in a central region of the surface of a ceramic green sheet to form a first pattern sheet; forming a glass pattern adjacent to the conductive pattern in a region outside the central region of the surface of the first pattern sheet to form a second pattern sheet; stacking a plurality of the second pattern sheets, or stacking a plurality of the second pattern sheets and one or more of the first pattern sheets, to form a first laminate; laminating constraint sheets made of an inorganic composition having a higher sintering start temperature than the ceramic green sheets on both sides of the first laminate in the stacking direction to form a second laminate; and firing the second laminate.

[0005] FIG. 1 is a perspective view showing an example of a wiring board according to an embodiment. FIG. 2 is a cross-sectional view taken along line A-A in FIG. 1 . FIG. 3 is a cross-sectional view taken along line B-B in FIG. 2 . FIG. 4 is a flowchart showing an example of a manufacturing process for a wiring board according to an embodiment. FIG. 5 is a diagram showing a specific example of a first pattern sheet forming step. FIG. 6 is a diagram showing a specific example of a conductor pattern. FIG. 7 is a diagram showing a specific example of a second pattern sheet forming step. FIG. 8 is a diagram showing a specific example of a glass pattern. FIG. 9 is a diagram showing a specific example of a first laminate forming step. FIG. 10 is a diagram showing a specific example of a second laminate forming step. FIG. 11 is a diagram showing a specific example of a second pattern sheet forming step in a manufacturing process for a wiring board according to Alternative Embodiment 1. FIG. 12 is a diagram showing a specific example of a second pattern sheet forming step in a manufacturing process for a wiring board according to Alternative Embodiment 2. FIG. 13 is a diagram showing a specific example of a first pattern sheet forming step in a manufacturing process for a wiring board according to Alternative Embodiment 3. FIG. 14 is a diagram showing a specific example of a first pattern sheet forming step in a manufacturing process for a wiring board according to Alternative Embodiment 3. FIG. 15 is a diagram showing a specific example of a second pattern sheet forming step in a manufacturing process for a wiring board according to Alternative Embodiment 3. Fig. 16 is a diagram showing a specific example of a second pattern sheet forming step in the manufacturing process of a wiring board according to another embodiment 3. Fig. 17 is a diagram showing a specific example of a second pattern sheet forming step in the manufacturing process of a wiring board according to another embodiment 4. Fig. 18 is a diagram showing a specific example of a second pattern sheet forming step in the manufacturing process of a wiring board according to another embodiment 4. Fig. 19 is a diagram showing a specific example of a first laminate forming step in the manufacturing process of a wiring board according to another embodiment 5.

[0006] Hereinafter, embodiments of a method for manufacturing a wiring board disclosed in the present application will be described with reference to the accompanying drawings. Note that the present disclosure is not limited to the embodiments described below. Furthermore, each embodiment can be appropriately combined within a range that does not cause contradictions in the processing content. Furthermore, the same components in each of the following embodiments are given the same reference numerals, and duplicated explanations will be omitted.

[0007] 2. Description of the Related Art Conventionally, a multilayer wiring board has been known in which a plurality of ceramic base materials are used to form multiple layers and wiring is disposed between the layers.

[0008] Such a wiring board can be obtained, for example, by the following method. First, a pattern sheet is formed on the surface of a ceramic green sheet (hereinafter also referred to as "green sheet" as appropriate), with a conductor pattern that will become the wiring formed in the central region. Next, a plurality of pattern sheets with conductor patterns formed thereon are stacked to form a laminate. Next, constraining sheets made of an inorganic composition that has a higher firing start temperature than the green sheet are stacked on both sides of the laminate in the stacking direction. Next, the laminate with the constraining sheets stacked thereon is fired.

[0009] However, in the conventional technology, the shrinkage of the green sheet in the planar direction due to sintering is greater in the peripheral area where no conductor pattern is formed than in the central area where the conductor pattern is formed, which promotes deformation of the conductor pattern in the planar direction, resulting in variations in the width and pitch of the wiring obtained by firing the conductor pattern, and potentially reducing the dimensional accuracy of the wiring.

[0010] Therefore, there is a need for a technology that can improve the dimensional accuracy of wiring.

[0011] <Configuration of Wiring Board> First, the configuration of a wiring board 1 according to an embodiment will be described with reference to Figures 1 to 3. Figure 1 is a perspective view showing an example of a wiring board 1 according to an embodiment. Figure 2 is a cross-sectional view taken along line A-A in Figure 1. In the following, to clarify the positional relationships, mutually orthogonal X-axis, Y-axis, and Z-axis are defined, and the positive direction of the Z-axis is defined as the vertically upward direction.

[0012] As shown in FIGS. 1 and 2, the wiring board 1 has an insulating base 2 and a conductor layer 3 .

[0013] The insulating base 2 has a plurality of laminated ceramic insulating layers 4. The insulating base 2 has a structure in which a plurality of ceramic insulating layers 4 are integrated. The insulating base 2 has a first surface 21 and a second surface 22 located at both ends in the lamination direction (Z-axis direction). Although Fig. 1 and Fig. 2 show an example in which the insulating base 2 has seven ceramic insulating layers 4, there is no limit to the number of ceramic insulating layers 4 that the insulating base 2 has.

[0014] The ceramic insulating layer 4 may be, for example, a glass ceramic. Here, the glass ceramic may be any of a composite of a glass phase and ceramic particles, a composite of a glass phase and a crystalline phase formed by the crystallization of a portion of the glass phase, a composite in which ceramic particles exist in the glass phase, and a composite in which a glass phase exists at the grain boundaries between ceramic particles. The ceramic insulating layer 4 may be, for example, a ceramic composition that can be co-fired with copper, as described below.

[0015] The conductor layer 3 is, for example, a layer that forms wiring. The conductor layer 3 is located between each of the laminated ceramic insulating layers 4. The conductor layer 3 may be located on the first surface 21 and / or the second surface 22, which are the surfaces of the insulating base 2. The conductor layer 3 may be, for example, a layer obtained by firing a conductor paste containing copper powder. The conductor layer 3 is a copper metallized film.

[0016] The insulating base 2 also has a glass layer 5. The glass layer 5 may be formed by firing a glass paste containing glass powder, for example. The glass layer 5 is located in the peripheral portion 23AA of the insulating base 2, between two ceramic insulating layers 4 adjacent to each other in the stacking direction.

[0017] Here, the peripheral portion 23AA of the insulating base 2 refers to the portion extending from the side surface 23 connecting to the first surface 21 and the second surface 22 of the insulating base 2 to between adjacent ceramic insulating layers 4 in the stacking direction of the insulating base 2. The portion of the insulating base 2 extending between adjacent ceramic insulating layers 4 in the stacking direction is referred to as the peripheral region 23A. In other words, the peripheral portion 23AA refers to the region of the insulating base 2 that includes the side surface 23 and the peripheral region 23A.

[0018] By providing the glass layer 5 between two ceramic insulating layers 4 adjacent in the stacking direction in the peripheral edge portion 23AA of the insulating base 2, peeling or cracking of the ceramic insulating layers 4 in the insulating base 2 becomes less likely to occur.

[0019] Fig. 3 is a cross-sectional view taken along the line B-B in Fig. 2. Fig. 3 shows a plan view of the surface of the conductor layer 3 located below the uppermost ceramic insulating layer 4, as viewed from above (the Z-direction positive side) of the wiring substrate 1 shown in Fig. 2. As shown in Fig. 3, the glass layer 5 may be located on the surface of the ceramic insulating layer 4 with a gap between it and the end of the conductor layer 3. Alternatively, the glass layer 5 may be located in the peripheral region 23A of each ceramic insulating layer 4 constituting the insulating base 2 so as to surround the outer periphery of the conductor layer 3.

[0020] <Process for Manufacturing Wiring Board> Next, a process for manufacturing the wiring board 1 according to the embodiment will be described with a specific example and with reference to Fig. 4. Fig. 4 is a flowchart showing an example of the process for manufacturing the wiring board 1 according to the embodiment.

[0021] First, as shown in FIG. 5 , a conductive pattern 11 is formed in the central region of the surface of a green sheet 10 to form a first pattern sheet 12 (step S101). FIG. 5 illustrates a specific example of the first pattern sheet formation process. The green sheet 10, which will become the ceramic insulating layer 4 (see FIG. 2 ), is a ceramic green sheet made of, for example, glass ceramic and has a predetermined planar shape (e.g., rectangular). The green sheet 10 can be formed, for example, by adding and mixing a sintering aid, binder, solvent, dispersant, etc. to a glass powder (e.g., borosilicate alkaline earth oxide glass) as the main component material to form a slurry, and then molding this slurry using a doctor blade method. The conductive pattern 11, which will become the conductive layer, is formed, for example, by printing a conductive paste containing copper powder on the surface of the green sheet 10.

[0022] Fig. 6 is a diagram showing a specific example of the conductor pattern 11. Fig. 6 shows the position where the conductor pattern 11 is formed when viewed in a plan view from a direction perpendicular to the surface of the green sheet 10. As shown in Fig. 6, the conductor pattern 11 is formed in a central region of the surface of the green sheet 10, excluding a peripheral region 10A. The peripheral region 10A of the green sheet 10 is a portion that includes an area corresponding to the peripheral region 23A of the ceramic insulating layer 4 (see Fig. 3).

[0023] 7, a glass pattern 13 is formed adjacent to the conductor pattern 11 in the peripheral region 10A of the surface of the green sheet 10 constituting the first pattern sheet 12 to form a second pattern sheet 14 (step S102). Fig. 7 shows a specific example of the second pattern sheet forming step. The glass pattern 13, which becomes the glass layer, is formed, for example, by printing a glass paste containing glass powder on the surface of the green sheet 10.

[0024] In the step of forming the second pattern sheet 14 , the glass pattern 13 may be formed using a glass paste containing glass powder whose sintered body has a thermal expansion coefficient equal to or lower than that of the sintered body of the green sheet 10 .

[0025] In the step of forming the second pattern sheet 14, the glass pattern 13 may be formed using a glass paste containing glass powder having a glass transition point of 400°C or higher and 600°C or lower.

[0026] Fig. 8 is a diagram showing a specific example of the glass pattern 13. Fig. 8 shows the position where the glass pattern 13 is formed when viewed in a plan view from a direction perpendicular to the surface of the green sheet 10. As shown in Fig. 8, the glass pattern 13 is formed in the peripheral region 10A of the first pattern sheet 12 so as to surround the outer periphery of the conductor pattern 11. The glass pattern 13 is formed with a gap between it and the end of the conductor pattern 11.

[0027] Next, as shown in Fig. 9, for example, a plurality of second pattern sheets 14 (six layers in this example) are stacked to form a first laminate 15 (step S103). Fig. 9 is a diagram showing a specific example of the first laminate formation step. The first laminate 15 has an upper surface 15a and a lower surface 15b located at both ends in the stacking direction (Z-axis direction). A green sheet 10 on which neither the conductor pattern 11 nor the glass pattern 13 is formed is arranged on the outermost layer (top layer) of the first laminate 15.

[0028] Next, as shown in FIG. 10 , a second laminate 17 is formed by laminating a constraining sheet 16 made of an inorganic composition having a higher sintering start temperature than the green sheet 10 on the upper surface 15 a and the lower surface 15 b of the first laminate 15 in the lamination direction (step S104). FIG. 10 illustrates a specific example of the second laminate formation step. The inorganic composition constraining sheet 16 may be, for example, alumina. The constraining sheet 16 is formed, for example, by adding a binder to alumina powder and mixing them to prepare a slurry, which is then molded by a doctor blade method.

[0029] 10 is then fired at a predetermined temperature (e.g., 900 to 1000° C.) lower than the sintering start temperature of the constraining sheet 16 (step S105). The constraining sheet 16 is then removed from the fired second laminate 17, thereby completing the wiring board 1.

[0030] As described above, in the manufacturing process of the wiring board 1 according to the embodiment, the glass pattern 13 is formed adjacent to the conductor pattern 11 in the peripheral region 10A on the surface of the first pattern sheet 12 .

[0031] As a result, in the peripheral region 10A where the conductor pattern 11 of the first pattern sheet 12 is not formed, the shrinkage of the green sheet 10 in the planar direction due to sintering is limited by the glass pattern 13, thereby reducing deformation of the conductor pattern 11 in the planar direction.

[0032] Therefore, according to the embodiment, it is possible to reduce variations in the width, etc. of the conductor layer 3 obtained by firing the conductor pattern 11, thereby improving the dimensional accuracy of the wiring formed by the conductor layer 3.

[0033] In addition, in the embodiment, by forming the glass pattern 13 in the peripheral region 10A of the first pattern sheet 12, the difference in thickness between the peripheral region 23A (see Figure 2) and the central region of the wiring board 1 can be reduced.

[0034] If the glass pattern 13 were not formed in the peripheral region 10A of the first pattern sheet 12, the green sheet 10 would shrink more in the planar direction and less in the thickness direction in the peripheral region 10A than in the central region. Because the green sheet 10 shrinks less in the thickness direction in the peripheral region 10A of the first pattern sheet 12, the thickness of the peripheral region 23A (see FIG. 2 ) of the wiring board 1 may be greater than the thickness of the central region.

[0035] In contrast, in the embodiment, the glass pattern 13 is formed in the peripheral region 10A of the first pattern sheet 12, so that an increase in thickness in the peripheral region 23A of the wiring board 1 can be reduced.

[0036] Therefore, according to the embodiment, the possibility of a difference in thickness occurring between the peripheral region 23A and the central region of the wiring board 1 can be reduced due to the green sheet 10 shrinking less in the thickness direction in the peripheral region 10A than in the central region.

[0037] In addition, in the embodiment, by forming a glass pattern 13 in the peripheral region 10A of the first pattern sheet 12 so as to surround the outer periphery of the conductor pattern 11, deformation of the conductor pattern 11 in the planar direction can be reduced around the entire periphery of the conductor pattern 11.

[0038] Therefore, according to the embodiment, the dimensional accuracy of the wiring formed by the conductor layer 3 can be further improved.

[0039] 7 shows that the peripheral region 10A of the green sheet 10 forms the glass pattern 13 in a position corresponding to the peripheral region 23A of the ceramic insulating layer 4 of the wiring substrate 1 obtained after firing, but the present disclosure is not limited to this. For example, the following steps can be mentioned.

[0040] A green sheet having a larger area than the size of green sheet 10 shown in Fig. 7 is used. The glass pattern is formed so that its width is wider from the edge of conductor pattern 11 outward than glass pattern 13 shown in Fig. 7. The region outside the central region on the surface of the first pattern sheet means to include a range wider from the central region outward than peripheral region 10A shown in Figs. 7 and 8.

[0041] Next, a laminate is formed using a pattern sheet (corresponding to the second pattern sheet 14) on which a glass pattern is formed with a wide width.

[0042] Next, when forming the first laminate 15 and the second laminate 17 from the laminate, the laminate is cut in the stacking direction so that the laminate has the same size as the first laminate 15 shown in Figure 9 and the second laminate 17 shown in Figure 10.

[0043] In the embodiment, the glass pattern 13 is formed with a gap between it and the end of the conductor pattern 11 .

[0044] This reduces the possibility of the conductor pattern 11 and the glass pattern 13 overlapping each other and causing a step, even if the conductor pattern 11 and the glass pattern 13 are deformed due to the pressure and heat treatment used to form the first laminate 15 or the second laminate 17.

[0045] Therefore, according to the embodiment, it is possible to reduce the deterioration of dimensional accuracy caused by the occurrence of steps.

[0046] In the embodiment, the glass pattern 13 is formed using a glass paste containing glass powder whose sintered body has a thermal expansion coefficient equal to or lower than that of the sintered body of the green sheet 10 .

[0047] As a result, during the cooling process after firing of the second laminate 17, the thermal expansion coefficient of the glass layer 5 obtained by sintering the glass pattern 13 becomes equal to or lower than the thermal expansion coefficient of the ceramic insulating layer 4 obtained by sintering the green sheet 10. As a result, a compressive stress acts on the glass layer 5, and the glass layer 5 is constrained by the ceramic insulating layer 4. In this case, the thermal expansion coefficient of the glass layer 5 can be controlled by the amount of crystals precipitated in the glass pattern 13. The amount of crystals precipitated in the glass pattern 13 can be adjusted by changing the maximum temperature during firing, the holding time thereof, the heating rate, and the cooling rate.

[0048] Therefore, according to the embodiment, the possibility of cracks occurring in the glass layer 5 can be reduced, and it is possible to obtain a wiring board 1 that maintains high dimensional accuracy and has high durability.

[0049] In the embodiment, the glass pattern 13 is formed using a glass paste containing glass powder having a glass transition point of 400° C. or more and 600° C. or less.

[0050] As a result, the temperature range above the glass transition point of the glass pattern 13 becomes close to room temperature, and the viscoelasticity (ductility) of the glass pattern 13 can be maintained at temperatures close to room temperature during the cooling process after firing of the second laminate 17.

[0051] Therefore, according to the embodiment, the possibility of cracks occurring in the glass layer 5 can be reduced, and it is possible to obtain a wiring board 1 that maintains high dimensional accuracy and has high durability.

[0052] In addition, in the embodiment, by placing a green sheet 10 on which no conductor pattern 11 or glass pattern 13 is formed on the outermost layer (top layer) of the first laminate 15, the possibility of a step occurring on the upper surface 15a of the first laminate 15 can be reduced.

[0053] Therefore, according to the embodiment, the restraining sheet 16 can be stably laminated onto the upper surface 15a of the first laminate 15.

[0054] <Other Embodiments> Next, various other embodiments will be described with reference to Figures 11 to 19. In the various other embodiments below, the same components as those in the embodiment will be assigned the same reference numerals, and redundant description will be omitted.

[0055] 11 is a diagram showing a specific example of a second pattern sheet forming step in the manufacturing process of the wiring board 1 according to Alternative Embodiment 1. In the second pattern sheet forming step according to Alternative Embodiment 1, the formation mode of the glass pattern 13 differs from that of the embodiment.

[0056] Specifically, in another embodiment 1, as shown in FIG. 11, a glass pattern 13 is formed in contact with an end 18 of a conductor pattern 11 .

[0057] As a result, in another embodiment 1, the conductor pattern 11 and the glass pattern 13 are constrained by each other during the cooling process after firing of the second laminate 17, making it difficult for the conductor pattern 11 to deform in the planar direction.

[0058] As a result, according to the first alternative embodiment, the dimensional accuracy of the wiring formed by the conductor layer 3 can be further improved.

[0059] 12 is a diagram showing a specific example of a second pattern sheet forming step in the manufacturing process of the wiring board 1 according to another embodiment 2. In the second pattern sheet forming step according to another embodiment 2, the shape of the conductor pattern 11 and the formation mode of the glass pattern 13 are different from those in another embodiment 1.

[0060] 12 , the end 18 of the conductor pattern 11 has an end face 18a that is inclined so that the distance from the surface of the green sheet 10 decreases toward the periphery of the green sheet 10 that constitutes the first pattern sheet 12. In addition, in the second embodiment, the glass pattern 13 is formed so as to overlap the inclined end face 18a of the conductor pattern 11.

[0061] As a result, in another embodiment 2, the contact area between the conductor pattern 11 and the glass pattern 13 can be increased compared to when the end face 18a of the conductor pattern 11 is not inclined with respect to the surface of the green sheet 10.

[0062] Therefore, according to another embodiment 2, the restraining force between the conductor pattern 11 and the glass pattern 13 is increased, making the conductor pattern 11 less likely to deform in the planar direction, and as a result, the dimensional accuracy of the wiring formed by the conductor layer 3 can be further improved.

[0063] 13 and 14 are diagrams showing a specific example of a first pattern sheet forming step in the manufacturing process of a wiring board 1 according to another embodiment 3. FIG. 14 shows the position where a conductor pattern 11 is formed when viewed in a plan view from a direction perpendicular to the surface of a green sheet 10. FIGS. 15 and 16 are diagrams showing a specific example of a second pattern sheet forming step in the manufacturing process of a wiring board 1 according to another embodiment 3. FIG. 16 shows the position where a glass pattern 13 is formed when viewed in a plan view from a direction perpendicular to the surface of a green sheet 10. In the manufacturing process of a wiring board 1 according to another embodiment 3, the formation modes of the conductor pattern 11 and the glass pattern 13 differ from those of the embodiment.

[0064] 13 and 14, a conductor pattern 11 is formed in the first pattern sheet formation process, including a plurality of (three in this case) parallel-extending strip-shaped conductor patterns 19. In addition, as shown in FIGS. 15 and 16, a glass pattern 13 is further formed between adjacent strip-shaped conductor patterns 19 in the second pattern sheet formation process.

[0065] This can reduce deformation of the adjacent strip-shaped conductor patterns 19 in the planar direction.

[0066] In another embodiment 3, the glass pattern 13 is formed with a gap between the sides of the adjacent strip-shaped conductor patterns 19 .

[0067] This reduces the possibility of the strip conductor pattern 19 and the glass pattern 13 overlapping each other and creating a step, even if the strip conductor pattern 19 and the glass pattern 13 are deformed due to the pressure and heat treatment used to form the first laminate 15 or the second laminate 17.

[0068] 17 and 18 are diagrams showing a specific example of a second pattern sheet forming step in the manufacturing process of wiring board 1 according to Alternative Embodiment 4. Fig. 18 shows the position where glass pattern 13 is formed when viewed in a plan view from a direction perpendicular to the surface of green sheet 10. In the second pattern sheet forming step according to Alternative Embodiment 4, the formation mode of glass pattern 13 differs from that of Alternative Embodiment 3.

[0069] Specifically, in another embodiment 4, as shown in FIGS. 17 and 18, the glass pattern 13 is formed in contact with the sides of a plurality of adjacent strip-shaped conductor patterns 19 .

[0070] As a result, in another embodiment 4, the strip conductor patterns 19 and the glass pattern 13 are constrained to each other during the cooling process after firing of the second laminate 17, making it difficult for the strip conductor patterns 19 to deform in the planar direction.

[0071] 19 is a diagram showing a specific example of a first laminate formation step in the manufacturing process of the wiring board 1 according to another embodiment 5. In the first laminate formation step according to another embodiment 5, the formation mode of the first laminate 15 differs from that of the embodiment.

[0072] 19, a plurality of (here, three layers) second pattern sheets 14 and one or more (here, three layers) first pattern sheets 12 are laminated to form a first laminate 15. The first laminate 15 preferably contains second pattern sheets 14 in a ratio of 10% to 90% by number of layers.

[0073] This reduces the occurrence of steps at the peripheral portion of the first laminate 15 due to the thickness of the glass pattern 13 of the second pattern sheet 14, compared to when all layers of the first laminate 15 are composed of the second pattern sheet 14.

[0074] As described above, the method for manufacturing a wiring board according to the embodiment includes the steps of forming a conductor pattern (for example, conductor pattern 11) in a central region of the surface of a ceramic green sheet (for example, green sheet 10) to form a first pattern sheet (for example, first pattern sheet 12), and forming a glass pattern (for example, glass pattern 13) adjacent to the conductor pattern in a region (for example, peripheral region 10A) outside the central region of the surface of the first pattern sheet to form a second pattern sheet (for example, second pattern sheet 14). the step of laminating a plurality of second pattern sheets or a plurality of second pattern sheets and one or more first pattern sheets to form a first laminate (for example, first laminate 15), the step of laminating constraining sheets (for example, constraining sheets 16) made of an inorganic composition having a sintering start temperature higher than that of the ceramic green sheets on both sides (for example, upper surface 15a and lower surface 15b) in the lamination direction (for example, Z-axis direction) of the first laminate to form a second laminate (for example, second laminate 17), and the step of firing the second laminate. This can improve the dimensional accuracy of the wiring.

[0075] (Sample Preparation) First, a green sheet (200 mm x 200 mm x 200 μm thick) containing a glass-ceramic raw material powder was prepared. The glass-ceramic raw material powder was a mixed powder of borosilicate alkaline earth oxide glass and silica particles. Specifically, a mixed powder was used in which 50 parts by mass of silica particles were added to 100 parts by mass of borosilicate alkaline earth oxide glass. In addition, a butyral-based organic resin was used as the organic vehicle for the green sheet.

[0076] The conductive paste for the conductive layer was a mixture of copper powder and alkaline earth borosilicate glass powder. A cellulose-based organic resin was used as the organic vehicle. The solid content was 100 parts by mass of copper powder and 30 parts by mass of alkaline earth borosilicate glass powder.

[0077] Next, a glass paste for forming the glass layer was prepared. A cellulose-based organic resin was used as the organic vehicle. A borosilicate alkaline earth oxide glass powder was also used as the glass powder for the glass paste. In this case, the glass transition temperature of the borosilicate alkaline earth oxide glass powder was set to 500°C. The yield point of the glass powder used for the green sheet was set to 700°C.

[0078] Next, a conductive paste was printed in a solid pattern in the central region of the green sheet, leaving a peripheral region (3 mm) unprinted, to form a conductive pattern (dry film). The thickness of the dry film of the conductive pattern was approximately 20 μm. The area of ​​the ceramic insulating layer of the wiring substrate 1 was assumed to be 100 mm × 100 mm, and the size of the conductive pattern was 96 mm × 96 mm.

[0079] Next, a glass paste was printed on the peripheral portion of the green sheet of the first pattern sheet to produce a second pattern sheet having a glass pattern. The thickness of the glass pattern was the same as that of the conductor pattern. The thickness of the conductor pattern tended to gradually decrease toward the end. The following two arrangements (1) and (2) were adopted for the glass pattern relative to the conductor pattern: (1) A distance of approximately 0.1 mm from the conductor pattern (see, for example, Figure 7); (2) A shape in which the end of the conductor pattern becomes thinner toward the tip, i.e., a shape with a so-called inclined surface, and the glass pattern overlaps the inclined surface (see, for example, Figure 12).

[0080] Next, multiple second pattern sheets and one or more first pattern sheets (30 layers in total) were stacked, and then a plain green sheet without a conductor pattern or glass pattern was placed on top of the top layer. This was followed by pressurization and heating (30 MPa, 100°C, 10 minutes) to produce a first laminate. The size of the first laminate was approximately 100 mm x 100 mm x 7 mm. In the first laminate, the layers on which the glass patterns were formed were the 1st, 5th, 10th, 15th, 20th, 25th, and 30th layers from the bottom side of the first laminate.

[0081] Next, alumina sheets serving as restraint sheets were placed on both sides of the first laminate to produce a second laminate for firing. The alumina sheets were arranged to cover the entire surfaces of both sides of the first laminate. The alumina sheets were prepared by adding butyral resin to alumina powder with an average particle size of 3 μm. In this case, borosilicate alkaline earth glass powder was also added to the alumina sheet. The amount of borosilicate alkaline earth glass powder added was 20% by volume relative to the alumina powder. The alumina sheets have the property of causing almost no firing shrinkage at the temperature at which the first laminate is sintered. The alumina sheets have a sintering start temperature higher than the sintering start temperature of the first laminate. The alumina sheets have a thickness of 1 mm.

[0082] As a comparative example, a laminate was formed in the same manner as above using the manufacturing method, by laminating 30 layers of a first pattern sheet in which a conductive pattern was formed on a green sheet, and alumina sheets were similarly placed on both sides of this to produce a second laminate, which was a laminate for firing.

[0083] Ten samples of each of the following wiring substrates, Samples 1 to 3, were prepared. Sample 1: A sample in which the glass pattern was spaced apart from the conductor pattern (corresponding to FIG. 7). Sample 2: A sample in which the glass pattern overlapped the inclined surface (end face) of the conductor pattern (corresponding to FIG. 12). Sample 3: A sample in which no glass pattern was formed (comparative example).

[0084] The firing was carried out under the conditions that the material was degreased in a wet nitrogen atmosphere, and then in a dry nitrogen atmosphere at a maximum temperature of 900° C. and maintained for 2 hours.

[0085] (Evaluation of Samples) Evaluation was carried out on the samples after firing.

[0086] First, the surface of the fired sample was polished to remove the glass ceramic insulating layer on the surface and expose the solid conductor layer, which was located at the 1st, 15th, and 30th layers from the top surface of the wiring board.

[0087] Next, the dimensions of each exposed conductor layer were measured. The dimensional measurement method for the conductor layer was as follows: The coefficient of variation (standard deviation / average value) of the dimensions of the conductor layer on the wiring substrate was determined by measuring the positional deviation of the four corners (four corners) of the conductor layer after firing, using the positions of the four corners (four corners) of the rectangular conductor pattern before firing as the reference. A digital microscope capable of storing two-dimensional coordinates was used for the measurement. When determining the relationship between the positions of the four corners (four corners) of the conductor pattern before firing and the positions of the four corners (corners) of the conductor layer after firing, the positions of the four corners of the conductor pattern before firing were determined, and these positions were used as the reference point. The reference points, which were the positions of the four corners of the conductor pattern before firing, were stored in the digital microscope in advance. At this time, one of the four corners was used as the reference origin, and the other three were used as reference points. Next, similar measurements were performed on the conductor layer formed on the wiring substrate after firing. For the conductor layer, one corner in the same positional relationship as the conductor pattern was used as the reference origin. The reference origin of the conductor layer formed on the fired wiring board was aligned with the reference origin of the conductor pattern before firing, and one of the two sides of the conductor layer extending approximately perpendicular to the reference origin was aligned with the side of the conductor pattern in the same direction. Next, the positions of three corners on the conductor layer other than the reference origin were determined. The deviations of the positions of the three corners on the conductor layer other than the reference origin from the positions of the three corners on the conductor pattern other than the reference origin were determined. The positions of the three corners on the conductor pattern other than the reference origin were designated Cg2, Cg3, and Cg4. The positions of the three corners on the conductor layer other than the reference origin were designated C2, C3, and C4. The deviations of the positions of the three corners of the conductor layer from the positions of the three corners of the conductor pattern were determined as C2-Cg2, C3-Cg3, and C4-Cg4, respectively. Such measurements were performed on three layers, namely, the 1st layer, the 15th layer, and the 30th layer, for one wiring board. Ten wiring boards were fabricated under one set of conditions, and the coefficient of variation was calculated from these.

[0088] (Results) The coefficient of variation (standard deviation / average value) of the dimensions of the first and 30th conductor layers was 1.2 for Sample 1 and 2.5 for Sample 3, where Sample 2 was set to 1.

[0089] Furthermore, the coefficient of variation (standard deviation / average value) of the dimensions of the 15th conductor layer was 1.5 for sample 1 and 3.5 for sample 3, assuming that sample 2 was 1.

[0090] As described above, the coefficients of variation for Samples 1 and 2, which are examples, were 1.5 or less. In contrast, the coefficient of variation for Sample 3, which is a comparative example, was greater than 1.5. These results show that the conductor layers of Samples 1 and 2, which are examples, have less dimensional variation than the conductor layer of Sample 3, which is a comparative example; in other words, the dimensional accuracy of the conductor layer is higher.

[0091] The present disclosure has been described in detail above, but the present disclosure is not limited to the above-described embodiments, and various modifications, improvements, etc. are possible within the scope that does not deviate from the gist of the present disclosure.

[0092] In addition, the following supplementary notes are disclosed regarding the above-described embodiment.

[0093] (Supplementary Note 1) A method for manufacturing a wiring board, comprising: a step of forming a first pattern sheet by forming a conductor pattern in a central region of the surface of a ceramic green sheet; a step of forming a second pattern sheet by forming a glass pattern adjacent to the conductor pattern in a region of the surface of the first pattern sheet outside the central region; a step of stacking a plurality of the second pattern sheets, or stacking a plurality of the second pattern sheets and one or more of the first pattern sheets, to form a first laminate; a step of stacking constraint sheets made of an inorganic composition having a sintering start temperature higher than that of the ceramic green sheets on both sides of the first laminate in the stacking direction to form a second laminate; and a step of firing the second laminate.

[0094] (Appendix 2) The method for manufacturing a wiring board according to Appendix 1, wherein the step of forming the second pattern sheet includes forming the glass pattern using a glass paste containing glass powder whose sintered body has a thermal expansion coefficient equal to or lower than that of the sintered body of the ceramic green sheet.

[0095] (Supplementary Note 3) The method for manufacturing a wiring board according to Supplementary Note 1 or 2, wherein the step of forming the second pattern sheet forms the glass pattern using a glass paste containing glass powder having a glass transition point of 400°C or higher and 600°C or lower.

[0096] (Supplementary Note 4) The method for manufacturing a wiring board according to any one of Supplementary Notes 1 to 3, wherein the step of forming the second pattern sheet includes forming the glass pattern on the outside of the first pattern sheet so as to surround the periphery of the conductor pattern.

[0097] (Supplementary Note 5) The method for manufacturing a wiring board according to any one of Supplementary Notes 1 to 4, wherein the step of forming the second pattern sheet includes forming the glass pattern at a distance from an end of the conductor pattern.

[0098] (Supplementary Note 6) The method for manufacturing a wiring board according to any one of Supplementary Notes 1 to 4, wherein the step of forming the second pattern sheet comprises forming the glass pattern in contact with an end of the conductor pattern.

[0099] (Appendix 7) The method for manufacturing a wiring board according to Appendix 6, wherein an end of the conductor pattern has an end face that is inclined so that the distance from the surface of the ceramic green sheet decreases toward the periphery of the ceramic green sheet that constitutes the first pattern sheet, and the step of forming the second pattern sheet includes forming the glass pattern so as to overlap the inclined end face of the conductor pattern.

[0100] (Appendix 8) A method for manufacturing a wiring board according to any one of Appendices 1 to 7, wherein the step of forming the first pattern sheet forms the conductor pattern including a plurality of strip-shaped conductor patterns extending in parallel, and the step of forming the second pattern sheet further forms the glass pattern between adjacent ones of the plurality of strip-shaped conductor patterns.

[0101] (Supplementary Note 9) The method for manufacturing a wiring board according to Supplementary Note 8, wherein the step of forming the second pattern sheet includes forming the glass pattern at intervals from each side of the plurality of adjacent strip-shaped conductor patterns.

[0102] (Supplementary Note 10) The method for manufacturing a wiring board according to Supplementary Note 8, wherein the step of forming the second pattern sheet includes forming the glass pattern in contact with each side of the plurality of adjacent strip-shaped conductor patterns.

[0103] (Appendix 11) The method for manufacturing a wiring board according to any one of Appendices 1 to 10, wherein the step of forming the first laminate comprises arranging a ceramic green sheet on the outermost layer of the first laminate, the ceramic green sheet having neither a conductor pattern nor a glass pattern formed thereon.

[0104] (Appendix 12) The method for manufacturing a wiring board described in any one of Appendices 1 to 11, wherein the step of forming the first laminate includes stacking a plurality of the second pattern sheets and one or more of the first pattern sheets to form a first laminate, and the first laminate has the second pattern sheets in a ratio of 10% to 90% by number of layers.

[0105] Further advantages and alternative embodiments may readily occur to those skilled in the art. Therefore, the invention in its broader aspects is not limited to the specific details and representative embodiments shown and described above. Accordingly, various modifications may be made without departing from the spirit or scope of the general inventive concept as defined by the appended claims and their equivalents.

[0106] REFERENCE SIGNS LIST 1 wiring substrate 2 insulating base 3 conductor layer 4 ceramic insulating layer 5 glass layer 10 green sheet 10A peripheral region 11 conductor pattern 12 first pattern sheet 13 glass pattern 14 second pattern sheet 15 first laminate 15a upper surface 15b lower surface 16 restraining sheet 17 second laminate 18 end 18a end surface 19 strip-shaped conductor pattern 23 side surface 23A peripheral region 23AA peripheral portion

Claims

1. A method for manufacturing a wiring board, comprising: forming a conductor pattern in a central region of the surface of a ceramic green sheet to form a first pattern sheet; forming a glass pattern adjacent to the conductor pattern in a region outside the central region of the surface of the first pattern sheet to form a second pattern sheet; stacking a plurality of the second pattern sheets, or stacking a plurality of the second pattern sheets and one or more of the first pattern sheets, to form a first laminate; laminating constraint sheets made of an inorganic composition having a sintering start temperature higher than that of the ceramic green sheets on both sides in the stacking direction of the first laminate to form a second laminate; and firing the second laminate.

2. The method for manufacturing a wiring board according to claim 1, wherein the step of forming the second pattern sheet comprises forming the glass pattern using a glass paste containing glass powder whose sintered body has a thermal expansion coefficient lower than that of the sintered body of the ceramic green sheet.

3. A method for manufacturing a wiring board as described in claim 1, wherein the step of forming the second pattern sheet comprises forming the glass pattern using a glass paste containing glass powder having a glass transition point of 400°C or higher and 600°C or lower.

4. A method for manufacturing a wiring board as described in claim 1, wherein the step of forming the second pattern sheet includes forming the glass pattern on the outside of the first pattern sheet so as to surround the outer periphery of the conductor pattern.

5. A method for manufacturing a wiring board as described in claim 1, wherein the step of forming the second pattern sheet comprises forming the glass pattern with a gap between the end of the conductor pattern and the glass pattern.

6. A method for manufacturing a wiring board as described in claim 1, wherein the step of forming the second pattern sheet comprises forming the glass pattern in contact with an end of the conductor pattern.

7. A method for manufacturing a wiring board as described in claim 6, wherein an end of the conductor pattern has an end face that is inclined so that the distance from the surface of the ceramic green sheet becomes smaller toward the periphery of the ceramic green sheet constituting the first pattern sheet, and the step of forming the second pattern sheet includes forming the glass pattern by overlapping the inclined end face of the conductor pattern.

8. A method for manufacturing a wiring board as described in claim 1, wherein the step of forming the first pattern sheet forms the conductor pattern including a plurality of strip-shaped conductor patterns extending in parallel, and the step of forming the second pattern sheet further forms the glass pattern between adjacent ones of the plurality of strip-shaped conductor patterns.

9. A method for manufacturing a wiring board as described in claim 8, wherein the step of forming the second pattern sheet includes forming the glass pattern with a space between each of the sides of the adjacent plurality of strip-shaped conductor patterns.

10. A method for manufacturing a wiring board as described in claim 8, wherein the step of forming the second pattern sheet includes forming the glass pattern in contact with each side of the plurality of adjacent strip-shaped conductor patterns.

11. The method for manufacturing a wiring board according to claim 1, wherein the step of forming the first laminate comprises arranging a ceramic green sheet on the outermost layer of the first laminate, the ceramic green sheet having neither a conductor pattern nor a glass pattern formed thereon.

12. A method for manufacturing a wiring board as described in claim 1, wherein the step of forming the first laminate comprises stacking a plurality of the second pattern sheets and one or more of the first pattern sheets to form a first laminate, and the first laminate has the second pattern sheets in a ratio of 10% to 90% by number of layers.

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