Wiring board and mounting structure

Abstract

A wiring board according to the present disclosure comprises: an insulating substrate that has a first surface and a second surface on the opposite side from the first surface; a first pad and a second pad that are positioned on the first surface; a first circuit conductor that has a first end portion that is connected to the first pad and a second end portion that is positioned closer to the second surface side than the first end portion; a second circuit conductor that has a third end portion that is connected to the second pad and a fourth end portion that is positioned closer to the second surface side than the third end portion; and a third circuit conductor that connects the second end portion and the fourth end portion. The first circuit conductor and the second circuit conductor have a circuit structure of the same shape as each other, or have a plane-symmetric circuit structure that has a virtual plane that perpendicularly intersects a virtual straight line connecting the second end portion and the fourth end portion as the plane of symmetry.

Description

Wiring Board and Mounting Structure

[0001] The present invention relates to a wiring board and a mounting structure using the same.

[0002] In recent years, in wiring boards, power consumption has been increasing with the increase in capacity and speed, and the importance of confirming operations and characteristics in a high-temperature environment has been increasing. For example, in conventional wiring boards as described in Patent Documents 1 and 2, probes are connected to the front and back of the wiring board to confirm operations and characteristics.

[0003] Japanese Patent Application Laid-Open No. 4-120477, Japanese Patent No. 2901781

[0004] The wiring board according to the present disclosure includes an insulating substrate having a first surface and a second surface on the opposite side of the first surface, a first pad and a second pad located on the first surface, a first circuit conductor having a first end connected to the first pad and a second end located on the second surface side of the first end, a second circuit conductor having a third end connected to the second pad and a fourth end located on the second surface side of the third end, and a third circuit conductor connecting the second end and the fourth end. The first circuit conductor and the second circuit conductor have the same circuit structure as each other or have a plane-symmetric circuit structure with a virtual plane perpendicular to the virtual straight line connecting the second end and the fourth end as the symmetric plane.

[0005] The mounting structure according to the present disclosure includes the above wiring board and an electronic component connected to the wiring board.

[0006] It is an enlarged explanatory diagram for explaining a mounting structure in which an electronic component is mounted on a wiring board according to an embodiment of the present disclosure. It is a schematic diagram showing an example of a main part of a wiring board according to an embodiment of the present disclosure. It is a schematic diagram showing an example of the position of a second end in a main part of a wiring board according to an embodiment of the present disclosure. It is a schematic diagram showing another example of a main part of a wiring board according to an embodiment of the present disclosure. It is a schematic diagram showing still another example of a main part of a wiring board according to an embodiment of the present disclosure.

[0007] Conventional wiring boards, where probes are connected to both sides of the board to verify operation and characteristics, have difficulty verifying operation and characteristics in high-temperature environments. Specifically, one side of the wiring board is heated with a heater to create a high-temperature environment, making it impossible to connect probes to the side with the heater. Therefore, this disclosure provides a wiring board that can measure electrical characteristics in the actual temperature environment in which it is used.

[0008] A wiring board according to one embodiment of the present disclosure will be described with reference to Figures 1 to 5. Figure 1 is an enlarged explanatory diagram for illustrating a mounting structure 20 on which electronic components 8 are mounted on a wiring board 10 according to one embodiment of the present disclosure. Specifically, Figure 1 is a cross-sectional view showing the right half of the mounting structure 20. The wiring board 10 according to one embodiment includes an insulating substrate 1 and a solder resist 4.

[0009] The insulating substrate 1 has a structure in which insulating layers 2 and conductive layers 3 are alternately stacked. In the art, a laminate in which insulating layers and conductive layers are alternately stacked is sometimes referred to as an "insulating substrate." In this specification, "insulating substrate" also means a laminate in which insulating layers and conductive layers are alternately stacked.

[0010] As shown in Figure 1, in a wiring board 10 according to one embodiment, the insulating substrate 1 includes a core layer 1a and a build-up layer 1b. The core layer 1a includes a core insulating layer and a core conductor layer. The build-up layer 1b includes a build-up insulating layer and a build-up conductor layer.

[0011] The core insulating layer is an insulating layer 2 located approximately in the center of the insulating substrate 1 in the thickness direction. The core insulating layer is not particularly limited as long as it is made of an insulating material. Examples of insulating materials include epoxy resin, bismaleimide-triazine resin, polyimide resin, polyphenylene ether resin, and glass. Only one of these insulating materials may be used, or two or more may be used in combination. The thickness of the core insulating layer is not particularly limited and may be, for example, 200 μm or more and 1.8 mm or less.

[0012] The core insulating layer may contain reinforcing materials. Examples of reinforcing materials include insulating fabrics such as glass fibers, glass nonwoven fabrics, aramid nonwoven fabrics, aramid fibers, and polyester fibers. Only one type of reinforcing material may be used, or two or more types may be used in combination. Furthermore, the core insulating layer may contain dispersed inorganic insulating fillers such as silica, barium sulfate, talc, clay, glass, calcium carbonate, and titanium oxide. Only one type of inorganic insulating filler may be used, or two or more types may be used in combination.

[0013] On both sides of the insulating layer for the core, a conductive layer for the core, which is part of the conductive layer 3, is located. The conductive layer for the core is not particularly limited as long as it is made of a conductive material. Examples of conductive materials include metals such as copper. The thickness of the conductive layer for the core is not limited and may be, for example, 10 μm or more and 50 μm or less.

[0014] As shown in Figure 1, the core insulating layer has through-hole conductors 3a positioned to electrically connect the upper and lower surfaces of the core insulating layer. The through-hole conductors 3a are located within through-holes that penetrate from the upper surface to the lower surface of the core insulating layer. The through-hole conductors 3a are made of a metal such as copper. The through-hole conductors 3a are also part of the conductor layer 3.

[0015] The through-hole conductor 3a is connected to the core conductor layer formed on both sides of the core insulating layer. The through-hole conductor 3a may be formed integrally with the core conductor layer. The through-hole conductor 3a may be located only on the inner wall surface of the through-hole, or it may be filled inside the through-hole.

[0016] Although the insulating substrate 1 shown in Figure 1 includes a core layer 1a, the core layer 1a is not an essential component. For example, the insulating substrate 1 does not need to include a core layer 1a, as is generally the case with coreless substrates.

[0017] As shown in Figure 1, build-up layers 1b are located on both sides of the core layer 1a. The build-up layer 1b has a structure in which build-up insulating layers and build-up conductive layers are alternately stacked. As described above, in the case of an insulating substrate 1 that does not include the core layer 1a, the insulating substrate 1 includes only the build-up layer 1b.

[0018] The build-up insulating layer is an insulating layer 2 other than the core insulating layer. The build-up insulating layer is not particularly limited as long as it is made of an insulating material. Examples of insulating materials include epoxy resins, bismaleimide-triazine resins, polyimide resins, and polyphenylene ether resins. These resins may be used individually or in combination of two or more.

[0019] The build-up insulating layers may be made of the same resin or different resins. The build-up insulating layer and the core insulating layer may be made of the same resin or different resins. The thickness of the build-up insulating layer is not particularly limited and may be, for example, 10 μm or more and 100 μm or less. The build-up insulating layers may have the same thickness or different thicknesses.

[0020] The build-up insulating layer may contain reinforcing materials. Examples of reinforcing materials include insulating fabrics such as glass fibers, glass nonwoven fabrics, aramid nonwoven fabrics, aramid fibers, and polyester fibers. Only one type of reinforcing material may be used, or two or more types may be used in combination. Furthermore, the build-up insulating layer may contain dispersed inorganic insulating fillers such as silica, barium sulfate, talc, clay, glass, calcium carbonate, and titanium oxide. Only one type of inorganic insulating filler may be used, or two or more types may be used in combination.

[0021] A build-up conductor layer, which is part of the conductor layer 3, is located on the surface of the build-up insulating layer. The build-up conductor layer is not particularly limited as long as it is made of a conductive material. Examples of conductive materials include metals such as copper. The thickness of the build-up conductor layer is not limited and may be, for example, 1 μm or more and 30 μm or less.

[0022] The build-up conductor layers may be made of the same metal or different metals. The build-up conductor layers and the core conductor layer may be made of the same metal or different metals. The build-up conductor layers may have the same thickness or different thicknesses.

[0023] The build-up insulating layer contains via-hole conductors for electrically connecting the upper and lower surfaces of the build-up insulating layer. The via-hole conductors are located within via holes that penetrate from the upper surface to the lower surface of the build-up insulating layer. The via-hole conductors are made of a metal, such as copper. The via-hole conductors may be filled within the via holes or may be located only on the inner wall surface of the via holes. The via-hole conductors are part of the build-up conductor layer.

[0024] As shown in Figure 1, solder resist 4 may be located on the first surface 11 and the second surface 12 of the insulating substrate 1. The solder resist 4 is made of resin, and examples of the resin include acrylic-modified epoxy resin.

[0025] As shown in Figure 2, the insulating substrate 1 includes a first circuit conductor 71, a second circuit conductor 72, and a third circuit conductor 73. Figure 2 is a schematic diagram showing an example of the main part of a wiring board 10 according to one embodiment of the present disclosure. In Figure 2, the divisions of the fine insulating layer 2 are omitted. Although not shown in Figure 1, the first circuit conductor 71, the second circuit conductor 72, and the third circuit conductor 73 are not electrically connected to the electronic component 8 on the insulating substrate 1.

[0026] The first circuit conductor 71 includes a first end 61 and a second end 62. That is, the circuit from the first end 61 to the second end 62 is the first circuit conductor 71. The first end 61 is connected to the first pad 31. The first pad 31 is part of the conductor layer 3 and is located on the first surface 11 of the insulating substrate 1. For example, the first pad 31 may be a conductor layer 3 located on the first surface 11 that is exposed through an opening provided in the solder resist 4.

[0027] The second end portion 62 is located on the second surface 12 side of the first end portion 61. That is, the position of the second end portion 62 is not limited as long as it is located on the second surface 12 side of the first end portion 61. The second end portion 62 may be located on the second surface 12, as shown in Figure 2, or it may be located between the first surface 11 and the second surface 12, as shown in Figure 3. Figure 3 is a schematic diagram showing an example of the position of the second end portion 62 in the main part of a wiring board 10 according to one embodiment of the present disclosure. In Figure 3, the division of the fine insulating layer 2 is omitted.

[0028] The second circuit conductor 72 includes a third end 63 and a fourth end 64. That is, the circuit from the third end 63 to the fourth end 64 is the second circuit conductor 72. The third end 63 is connected to the second pad 32. The second pad 32 is part of the conductor layer 3 and is located on the first surface 11 of the insulating substrate 1. For example, the second pad 32 may be a conductor layer 3 located on the first surface 11 that is exposed through an opening provided in the solder resist 4.

[0029] The fourth end portion 64 is located on the second surface 12 side of the third end portion 63. That is, as long as it is located on the second surface 12 side of the third end portion 63, the position of the fourth end portion 64 is not limited. The fourth end portion 64 may be located on the second surface 12, as shown in Figure 2, or it may be located between the first surface 11 and the second surface 12, as shown in Figure 3. The fourth end portion 64 is located at the same depth as the second end portion 62 in the thickness direction of the insulating substrate 1. Specifically, the depth from the first surface 11 is the same for both the second end portion 62 and the fourth end portion 64.

[0030] The third circuit conductor 73 connects the second end 62 of the first circuit conductor 71 and the fourth end 64 of the second circuit conductor 72. The third circuit conductor 73 may be located on the second surface 12. That is, the second end 62, the fourth end 64, and the third circuit conductor 73 may all be located on the second surface 12. The position of the third circuit conductor 73 can be appropriately determined according to the desired design.

[0031] Although the length of the third circuit conductor 73 is not limited, a shorter length is preferable in that it allows for more accurate measurement of electrical characteristics. For example, the third circuit conductor 73 may have a length of 1 mm or less, as long as it is long enough to connect the second end 62 and the fourth end 64.

[0032] The size (area) of the first pad 31 and the size (area) of the land to which the second end 62 is connected are not limited. For example, the size of the first pad 31 and the size of the land to which the second end 62 is connected may be the same or different. The size (area) of the second pad 32 and the size (area) of the land to which the fourth end 64 is connected are not limited. For example, the size of the second pad 32 and the size of the land to which the fourth end 64 is connected may be the same or different.

[0033] The size of the first pad 31 and the size of the second pad 32 are approximately the same. The size of the land to which the second end 62 is connected and the size of the land to which the fourth end 64 is connected are approximately the same. "Approximately the same" means that they are considered the same if the difference is within the range of manufacturing tolerances, and that they are the same size if they are between 95% and 105% of the standard size.

[0034] If the size of the first pad 31 (second pad 32) and the size of the land to which the second end 62 (fourth end 64) is connected are different, as shown in Figure 4, the land to which the second end 62 (fourth end 64) is connected may be smaller than the first pad 31 (second pad 32). Figure 4 is a schematic diagram showing another example of the main part of a wiring board 10 according to one embodiment of the present disclosure.

[0035] The land to which the second end 62 (fourth end 64) is connected is the land to which the third circuit conductor 73 is connected. If the third circuit conductor 73 is connected to the land to which the smaller second end 62 (fourth end 64) is connected, signal reflection is reduced. As a result, noise is further reduced in the high-frequency range. The land to which the second end 62 (fourth end 64) is connected may be a pad corresponding to a flip-chip attach (FCA). The first pad 31 (second pad 32) may be a pad corresponding to a ball grid array (BGA).

[0036] In a wiring board 10 according to one embodiment, the first circuit conductor 71 and the second circuit conductor 72 either have the same circuit structure shape, or they have a plane-symmetrical circuit structure with a virtual plane perpendicular to a virtual line connecting the second end 62 and the fourth end 64 as the plane of symmetry. A circuit structure with the same shape shape means a circuit structure that overlaps precisely when superimposed. On the other hand, a plane-symmetrical circuit structure means a circuit structure that does not overlap when superimposed, but is in a so-called mirror image relationship.

[0037] For circuit structures of the same shape and symmetrical in plane, the length of the first circuit conductor 71 (length from the first end 61 to the second end 62) and the length of the second circuit conductor 72 (length from the third end 63 to the fourth end 64) are the same. Because the lengths of the first circuit conductor 71 and the second circuit conductor 72 are the same, the electrical characteristics can be measured by the measurement method described later, by connecting the measurement probe to the first pad 31 and the second pad 32 located on the first surface 11, without having to connect the measurement probe to the pads located on the front and back surfaces of the wiring board 10.

[0038] Next, a method for measuring the electrical characteristics of the first circuit conductor 71 (the wiring to be measured) will be described. Electrical characteristics include insertion loss and reflection loss. A measuring probe is connected to the first pad 31 and the second pad 32. Then, the electrical characteristics (for example, insertion loss) from the first end 61 through the third circuit conductor 73 to the third end 63 are measured. During measurement, the second surface 12 side may be heated with a heater or the like. The heating temperature should be set appropriately according to the temperature environment in which the wiring board 10 is used.

[0039] The measurement results are not for the first circuit conductor 71 (the wiring being measured), but for the section from the first end 61 to the third end 63. As mentioned above, the length of the first circuit conductor 71 and the length of the second circuit conductor 72 are the same. Therefore, half of the measured value approximates the measured value of the first circuit conductor 71 (the wiring being measured). Since the measurement results also include the third circuit conductor 73, half of the measured value corresponds to the length of the first circuit conductor 71 (second circuit conductor 72) and half of the length of the third circuit conductor 73. For this reason, as mentioned above, the third circuit conductor 73 should be as short as possible.

[0040] To improve the accuracy of the measurement of the first circuit conductor 71 (the wiring to be measured), the wiring board 10 may have a structure as shown in Figure 5. Figure 5 is a schematic diagram showing yet another example of the main parts of the wiring board 10 according to one embodiment of the present disclosure. The structure shown in Figure 5 further includes a fourth circuit conductor 74, a fifth circuit conductor 75, and a sixth circuit conductor 76 in addition to the first circuit conductor 71, the second circuit conductor 72, and the third circuit conductor 73. The first circuit conductor 71, the second circuit conductor 72, and the third circuit conductor 73 are as described above, and a detailed explanation is omitted.

[0041] The fourth circuit conductor 74 includes a fifth end 65 and a sixth end 66. That is, the circuit from the fifth end 65 to the sixth end 66 is the fourth circuit conductor 74. The fifth end 65 is connected to the third pad 33. The third pad 33 is part of the conductor layer 3 and is located on the first surface 11 of the insulating substrate 1. For example, the third pad 33 may be a conductor layer 3 located on the first surface 11 that is exposed through an opening provided in the solder resist 4.

[0042] The sixth end portion 66 is located on the second surface 12 side of the fifth end portion 65. That is, as long as it is located on the second surface 12 side of the fifth end portion 65, the position of the sixth end portion 66 is not limited. The sixth end portion 66 may be located on the second surface 12 as shown in Figure 5, or it may be located between the first surface 11 and the second surface 12.

[0043] The fifth circuit conductor 75 includes a seventh end portion 67 and an eighth end portion 68. That is, the circuit from the seventh end portion 67 to the eighth end portion 68 is the fifth circuit conductor 75. The seventh end portion 67 is connected to the fourth pad 34. The fourth pad 34 is a part of the conductor layer 3 and is located on the first surface 11 of the insulating substrate 1. For example, the fourth pad 34 may be the conductor layer 3 that is exposed from an opening provided in the solder resist 4 among the conductor layers 3 located on the first surface 11.

[0044] The eighth end portion 68 is located closer to the second surface 12 side than the seventh end portion 67. That is, as long as it is located closer to the second surface 12 side than the seventh end portion 67, the position of the eighth end portion 68 is not limited. The eighth end portion 68 may be located on the second surface 12 as shown in FIG. 5, or may be located between the first surface 11 and the second surface 12.

[0045] As shown in FIG. 5, the fourth circuit conductor 74 has the same circuit structure in shape as the first circuit conductor 71, and the fifth circuit conductor 75 has the same circuit structure in shape as the second circuit conductor 72. Therefore, the position of the sixth end portion 66 is set based on the position of the second end portion 62, and the position of the eighth end portion 68 is set based on the position of the fourth end portion 64. This "position" means the position in the thickness direction of the insulating substrate 1 (depth from the first surface 11).

[0046] The sixth circuit conductor 76 connects the sixth end portion 66 of the fourth circuit conductor 74 and the eighth end portion 68 of the fifth circuit conductor 75. The sixth circuit conductor 76 may be located on the second surface 12. That is, the sixth end portion 66, the eighth end portion 68, and the sixth circuit conductor 76 may be located on the second surface 12. The position of the sixth circuit conductor 76 is set based on the position of the third circuit conductor 73.

[0047] The size (area) of the third pad 33 and the size (area) of the land to which the sixth end portion 66 is connected are not limited. For example, the size of the third pad 33 and the size of the land to which the sixth end portion 66 is connected may be the same or different. The size (area) of the fourth pad 34 and the size (area) of the land to which the eighth end portion 68 is connected are not limited. For example, the size of the fourth pad 34 and the size of the land to which the eighth end portion 68 is connected may be the same or different.

[0048] The size of the third pad 33 and the size of the fourth pad 34 are substantially the same. The size of the land to which the sixth end portion 66 is connected and the size of the land to which the eighth end portion 68 is connected are substantially the same. "Substantially the same" means that it can be regarded as the same within the degree of manufacturing error, and if it is 95% or more and 105% or less with respect to the reference size, it means that they are of the same size. The size of the first pad 31, the size of the second pad 32, the size of the third pad 33, and the size of the fourth pad 34 may be substantially the same. The size of the land to which the second end portion 62 is connected, the size of the land to which the fourth end portion 64 is connected, the size of the land to which the sixth end portion 66 is connected, and the size of the land to which the eighth end portion 68 is connected may be substantially the same.

[0049] When the size of the third pad 33 (fourth pad 34) is larger than the size of the land to which the sixth end portion 66 (eighth end portion 68) is connected, the land to which the second end portion 62 (fourth end portion 64) is connected may be smaller than the first pad 31 (second pad 32).

[0050] The land to which the sixth end portion 66 (eighth end portion 68) is connected is the land to which the sixth circuit conductor 76 is connected. When the sixth circuit conductor 76 is connected to a smaller land to which the sixth end portion 66 (eighth end portion 68) is connected, signal reflection is reduced. As a result, in the high-frequency region, noise is further reduced. The land to which the sixth end portion 66 (eighth end portion 68) is connected may be a pad corresponding to a flip chip attach (FCA). The third pad 33 (fourth pad 34) may be a pad corresponding to a ball grid array (BGA).

[0051] The length L2 of the sixth circuit conductor 76 is 0.5 times or 2 times the length L1 of the third circuit conductor 73. That is, the third circuit conductor 73 and the sixth circuit conductor 76 have a length such that the longer one is twice the length of the shorter one. By having such a configuration for the third circuit conductor 73 and the sixth circuit conductor 76, electrical characteristics can be measured more accurately.

[0052] Next, a method for measuring the electrical characteristics of the first circuit conductor 71 (the wiring to be measured) in a wiring board 10 having the structure shown in Figure 5 will be described. In the structure shown in Figure 5, the length L2 of the sixth circuit conductor 76 is twice the length L1 of the third circuit conductor 73. First, a measuring probe is connected to the first pad 31 and the second pad 32. Then, the electrical characteristics (for example, insertion loss) from the first end 61 through the third circuit conductor 73 to the third end 63 are measured. The obtained measurement result is referred to as the first measurement result. In other words, the first measurement result is the measurement result for the first circuit conductor 71, the second circuit conductor 72, and the third circuit conductor 73.

[0053] Next, the measuring probe is connected to the third pad 33 and the fourth pad 34. Then, the electrical characteristics (e.g., insertion loss) from the fifth end 65 through the sixth circuit conductor 76 to the seventh end 67 are measured. The obtained measurement result is designated as the second measurement result. Of course, the second surface 12 side may be heated with a heater or the like during measurement.

[0054] As described above, the length of the first circuit conductor 71 and the length of the second circuit conductor 72 are the same. Therefore, since the fourth circuit conductor 74 has the same circuit structure as the first circuit conductor 71, and the fifth circuit conductor 75 has the same circuit structure as the second circuit conductor 72, the lengths of the fourth circuit conductor 74 and the fifth circuit conductor 75 are also the same. In other words, the lengths of the first circuit conductor 71, the second circuit conductor 72, the fourth circuit conductor 74, and the fifth circuit conductor 75 are all the same.

[0055] Next, the measured value in the obtained second measurement result is halved. Half of the measured value in the second measurement result corresponds to the length of the fourth circuit conductor 74 (length of the fifth circuit conductor 75) and half the length of the sixth circuit conductor 76. Half of the measured value in the second measurement result becomes the third measurement result. Subtracting the third measurement result from the first measurement result ("first measurement result" - "third measurement result") gives the measurement result (measured value) of the first circuit conductor 71 (the wiring being measured). These calculation formulas can be expressed as follows: Electrical characteristics of (first circuit conductor + second circuit conductor + third circuit conductor) - Electrical characteristics of (fourth circuit conductor + fifth circuit conductor + sixth circuit conductor) ÷ 2 = Electrical characteristics of the first circuit conductor

[0056] Since the length L2 of the sixth circuit conductor 76 is twice the length L1 of the third circuit conductor 73, half the length of the sixth circuit conductor 76 is equal to the length L1 of the third circuit conductor 73. Therefore, when the third measurement result is subtracted from the first measurement result, the measured values ​​corresponding to the measurement results of the second circuit conductor 72 and the third circuit conductor 73 are subtracted from the first measurement result, and the measurement result (measured value) of the first circuit conductor 71 (the wiring to be measured) is obtained. In the wiring board 10 having the structure shown in Figure 5, the measurement result of the first circuit conductor 71 (the wiring to be measured) can be obtained with higher accuracy than the measurement result that includes the length of the first circuit conductor 71 and half the length of the third circuit conductor 73.

[0057] At this time, as shown in Figure 5, the first circuit conductor 71, the second circuit conductor 72, the third circuit conductor 73, the fourth circuit conductor 74, the fifth circuit conductor 75, and the sixth circuit conductor 76 are located on the same wiring board. As a result, the finish of each conductor falls within the same manufacturing variation range, allowing for more accurate measurement of electrical characteristics.

[0058] Even if the length L2 of the sixth circuit conductor 76 is half the length L1 of the third circuit conductor 73, it is still possible to measure the electrical characteristics of the first circuit conductor 71 (the wiring to be measured). Specifically, the measurement results obtained by connecting the measuring probe to the third pad 33 and the fourth pad 34 are taken as the first measurement results, and the measurement results obtained by connecting the measuring probe to the first pad 31 and the second pad 32 are taken as the second measurement results. Since the first circuit conductor 71 has the same circuit structure as the fourth circuit conductor 74, the measurement results for the first circuit conductor 71 (the wiring to be measured) can be obtained by determining the measurement results for the fourth circuit conductor 74.

[0059] In the wiring board 10 according to one embodiment, the method for forming the first circuit conductor 71, second circuit conductor 72, third circuit conductor 73, fourth circuit conductor 74, fifth circuit conductor 75, and sixth circuit conductor 76 is not limited. For example, a circuit structure having the above-described structure may be formed using at least one of plating and metal foil. Plating or exposure and development may be carried out by known methods. The first circuit conductor 71, second circuit conductor 72, third circuit conductor 73, fourth circuit conductor 74, fifth circuit conductor 75, and sixth circuit conductor 76 are formed in areas that are not electrically connected to the electronic components 8 connected to the mounting area of ​​the wiring board 10.

[0060] Next, the mounting structure according to this disclosure will be described with reference to Figure 1. The mounting structure 20 according to one embodiment includes a wiring board 10 according to one embodiment and an electronic component 8 located in the mounting area of ​​the wiring board 10.

[0061] In the mounting area where the electronic component 8 is mounted, a mounting structure 20 according to one embodiment is obtained by connecting the conductive layer 3 (pad) exposed from an opening in the solder resist 4 located on the surface of the build-up layer 1b to the electrodes of the electronic component 8 via solder 5. Examples of electronic components 8 include semiconductor integrated circuit elements and optoelectronic elements. In the mounting structure 20 according to one embodiment, conductive layers 3 (pads) exposed from openings in the solder resist 4 may also be located on the surface (first surface 11) opposite to the surface (second surface 12) on which the electronic component 8 is mounted. A motherboard, for example, may be connected to this pad via solder 5, and further electronic components 8 may be connected via solder 5.

[0062] The embodiments of this disclosure have been described above. However, the invention relating to this disclosure is not limited to the embodiments described above, and various modifications and improvements are possible within the scope of this disclosure as shown in (1) to (6) below.

[0063] (1) The wiring board according to the present disclosure includes an insulating substrate having a first surface and a second surface on the opposite side of the first surface, a first pad and a second pad located on the first surface, a first circuit conductor having a first end connected to the first pad and a second end located on the second surface side of the first end, a second circuit conductor having a third end connected to the second pad and a fourth end located on the second surface side of the third end, and a third circuit conductor connecting the second end and the fourth end. The first circuit conductor and the second circuit conductor have circuit structures of the same shape as each other, or have a plane-symmetric circuit structure with a virtual plane that intersects perpendicularly with a virtual line connecting the second end and the fourth end as the plane of symmetry. (2) The wiring board described in (1) above further includes a third pad and a fourth pad located on the first surface, a fourth circuit conductor having a fifth end connected to the third pad and a sixth end located on the second surface side of the fifth end, a fifth circuit conductor having a seventh end connected to the fourth pad and an eighth end located on the second surface side of the seventh end, and a sixth circuit conductor connecting the sixth end and the eighth end. The fourth circuit conductor has the same circuit structure as the first circuit conductor. The fifth circuit conductor has the same circuit structure as the second circuit conductor. The length of the sixth circuit conductor is 0.5 or 2 times the length of the third circuit conductor. (3) The wiring board described in (1) above is located on the second surface. (4) The wiring board described in (2) above is located on the second surface. (5) The mounting structure relating to this disclosure includes a wiring board as described in any of (1) to (4) above and an electronic component connected to the wiring board. (6) In the mounting structure described in (5) above, the electronic component is located on the second surface.

[0064] The wiring board relating to this disclosure has the configuration described in the section on means for solving the problem, thereby enabling the measurement of electrical characteristics under the actual temperature environment in which it is used.

[0065] This disclosure can be used as a wiring board and mounting structure.

[0066] 1 Insulating substrate 11 First side 12 Second side 1a Core layer 1b Build-up layer 2 Insulating layer 3 Conductor layer 3a Through-hole conductor 31 First pad 32 Second pad 33 Third pad 34 Fourth pad 4 Solder resist 5 Solder 61 First end 62 Second end 63 Third end 64 Fourth end 65 Fifth end 66 Sixth end 67 Seventh end 68 Eighth end 71 First circuit conductor 72 Second circuit conductor 73 Third circuit conductor 74 Fourth circuit conductor 75 Fifth circuit conductor 76 Sixth circuit conductor 8 Electronic components 10 Wiring board 20 Mounting structure

Claims

1. A wiring board comprising: an insulating substrate having a first surface and a second surface on the opposite side of the first surface; a first pad and a second pad located on the first surface; a first circuit conductor having a first end connected to the first pad and a second end located on the second surface side of the first end; a second circuit conductor having a third end connected to the second pad and a fourth end located on the second surface side of the third end; and a third circuit conductor connecting the second end and the fourth end, wherein the first circuit conductor and the second circuit conductor have circuit structures of the same shape as each other, or have a plane-symmetrical circuit structure with a virtual plane perpendicular to a virtual line connecting the second end and the fourth end as the plane of symmetry.

2. A wiring board according to claim 1, further comprising: a third pad and a fourth pad located on the first surface; a fourth circuit conductor having a fifth end connected to the third pad and a sixth end located on the second surface side of the fifth end; a fifth circuit conductor having a seventh end connected to the fourth pad and an eighth end located on the second surface side of the seventh end; and a sixth circuit conductor connecting the sixth end and the eighth end, wherein the fourth circuit conductor has a circuit structure of the same shape as the first circuit conductor, the fifth circuit conductor has a circuit structure of the same shape as the second circuit conductor, and the length of the sixth circuit conductor is 0.5 or 2 times the length of the third circuit conductor.

3. The wiring board according to claim 1 or 2, wherein the third circuit conductor is located on the second surface.

4. The wiring board according to claim 2, wherein the third circuit conductor and the sixth circuit conductor are located on the second surface.

5. A mounting structure comprising a wiring board according to any one of claims 1 to 4 and an electronic component connected to the wiring board.

6. The mounting structure according to claim 5, wherein the electronic component is located on the second surface.

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