Method for manufacturing circuit board, and circuit board

Abstract

Provided is a method for manufacturing a circuit board, the method comprising: first, preparing a glass laminate (10) having, as a core substrate of a package substrate, a first outer glass layer (11) having a first surface (10a), and a first inner glass layer (13) bonded to the first outer glass layer (11) on the opposite side from the first surface (10a); in this method for manufacturing a circuit board, a first hole (H1) penetrating at least the first outer glass layer (11) and the first inner glass layer (13) from the first surface (10a) toward the second surface (10b) is formed by irradiating the first surface (10a) with laser light (L). In this method for manufacturing a circuit board, the light absorptivity of the first inner glass layer (13) is lower than the light absorptivity of the first outer glass layer (11). As a result, it is possible to easily form a hole for providing a connection member (40) for electrically connecting a first terminal (20) formed on the first surface (10a) and a second terminal (30) formed on the second surface (10b).

Description

Manufacturing method of circuit board and circuit board Technical Field

[0001] This invention relates to a method for manufacturing a circuit board and the circuit board itself. Background Technology

[0002] Flip chip mounting is a known method for mounting integrated circuits formed on silicon wafers. In recent years, from the viewpoint of suppressing warping of the package substrate, glass laminates as the core substrate of the package substrate have been studied in this flip chip mounting process.

[0003] In flip-chip mounting, to effectively bring out the terminals, it is necessary to attach, for example, the side of the package substrate opposite to the mounting surface to the motherboard. In this case, it is necessary to form a through hole through the package substrate from the mounting surface toward the opposite side, and to provide connection members for making the terminals formed on the mounting surface and the opposite side surface conductive.

[0004] When the aforementioned glass laminate is used as the core substrate of the encapsulation substrate, a through hole for providing the aforementioned connecting member is formed in the glass laminate by irradiating the glass laminate with laser light. Non-Patent Document 1 discloses an example of a method for forming a through hole in a glass laminate by irradiating it with laser light.

[0005] Previous technical documents

[0006] Non-patent literature

[0007] Non-patent document 1: K. Demir et al., "First demonstration of copper-platedthrough-package-via (TPV) reliability in ultra-thin 3D glass interposers with double-side component assembly," 2015 IEEE 65th Electronic Components and Technology Conference (ECTC), pp. 666-671, 2015. Summary of the Invention

[0008] The technical problem to be solved by the invention

[0009] When the aforementioned through-hole is formed in a glass laminate by irradiation with laser light, the surface of the glass laminate is irradiated with laser light to gradually form a hole penetrating the glass layers constituting the glass laminate. At this time, it is necessary to release the vaporized components that have been vaporized by the laser light irradiation to the outside of the hole. Therefore, a method can be considered whereby the glass layers constituting the glass laminate are removed layer by layer sequentially while changing the irradiation position of the laser light, thereby ensuring sufficient time before the vaporized components move to the outside of the hole. However, in this method, alignment is required each time the irradiation position of the laser light is changed, resulting in a time-consuming laser irradiation process. Therefore, a method for manufacturing a circuit board is required that can easily form holes for mounting connection components on a circuit board having a glass laminate as a substrate.

[0010] means for solving technical problems

[0011] The present invention claims a method for manufacturing a circuit board that can easily form holes for mounting connection components on a circuit board having a glass laminate as a substrate.

[0012] Invention Effects

[0013] [1] One aspect of the present invention relates to a method for manufacturing a circuit board, the circuit board comprising: a substrate having a first surface and a second surface located on a side opposite to the first surface; a first terminal formed on the first surface; and a second terminal formed on the second surface and electrically connected to the first terminal, the method for manufacturing the circuit board comprising: a step of preparing a glass laminate having a first surface and a second surface as the aforementioned substrate and having a plurality of glass layers laminated thereon; and a step of irradiating the glass laminate with laser light, wherein in the preparation step a glass laminate having a first outer glass layer including a first surface and a first inner glass layer bonded to the first outer glass layer on a side opposite to the first surface is prepared, and in the irradiation step a first hole is formed by irradiating the first surface with laser light, extending from the first surface toward the second surface through at least the first outer glass layer and the first inner glass layer, the light absorption rate of the first inner glass layer being lower than the light absorption rate of the first outer glass layer.

[0014] In this manufacturing method, the light absorption rate of the first inner glass layer is lower than that of the first outer glass layer. That is, in the above-mentioned irradiation process, the time required for the laser light to penetrate the first inner glass layer is longer than the time required for the laser light to penetrate the first outer glass layer. On the other hand, the time required for the laser light to penetrate the first inner glass layer is shorter than the time required for the laser light to align the irradiation position. Therefore, by making the light absorption rate of the first inner glass layer lower than that of the first outer glass layer, during the formation of the first hole, the vaporized components can be released to the outside of the first hole while the laser light penetrates the first inner glass layer, thus shortening the time required for the laser light irradiation process. As a result, according to the circuit board manufacturing method described above [1], holes for setting connection components can be easily formed.

[0015] [2] According to the circuit board manufacturing method described in [1], in the preparation step, a glass laminate having a first inner glass layer including a second surface can be prepared. In the irradiation step, a first hole penetrating from the first surface to the second surface can be formed. In this case, even if the glass laminate is a double-layer structure having a first outer glass layer and a first inner glass layer, during the formation of the first hole, the vaporized components can be released to the outside of the first hole while the laser light penetrates the first inner glass layer, thus shortening the time required for the laser light irradiation step. Therefore, according to the circuit board manufacturing method described in [2] above, even if the glass laminate is a double-layer structure having a first outer glass layer and a first inner glass layer, it is possible to easily form a hole for providing a connecting component.

[0016] [3] According to the method for manufacturing a circuit board as described in [1], in the preparation step, a glass laminate with multiple glass layers and a second outer glass layer including a second surface can be prepared. In the irradiation step, a second hole can be formed, which extends from the second surface toward the first surface through at least the second outer glass layer and communicates with the first hole. In this case, even if the glass laminate has a structure with at least three or more layers including a first outer glass layer, a first inner glass layer and a second outer glass layer, during the formation of the first hole, the vaporized components can be released to the outside of the first hole while the laser light penetrates the first inner glass layer, thus shortening the time required for the laser irradiation step. Therefore, according to the method for manufacturing a circuit board as described in [3] above, even if the glass laminate has a structure with at least three or more layers including a first outer glass layer, a first inner glass layer and a second outer glass layer, it is possible to easily form a hole for setting a connecting component.

[0017] [4] According to the circuit board manufacturing method described in [3] above, in the preparation step, a glass layer stack having a second inner glass layer bonded to the second outer glass layer on the side opposite to the second surface can be prepared. In the irradiation step, a second hole penetrating the second outer glass layer and the second inner glass layer can be formed by irradiating the second surface with laser light. The light absorption rate of the second inner glass layer can be lower than that of the second outer glass layer. In this case, by making the light absorption rate of the second inner glass layer lower than that of the second outer glass layer, even during the formation of the second hole, the vaporized components can be released to the outside of the second hole while the laser light penetrates the second inner glass layer, thus shortening the time required for the laser irradiation step. Therefore, according to the circuit board manufacturing method described in [4] above, it is possible to further simplify the formation of holes for setting connection components.

[0018] [5] According to the method for manufacturing a circuit board described in [4], the light absorption rate of the second inner glass layer may be lower than that of the first outer glass layer.

[0019] [6] According to the method for manufacturing a circuit board as described in [4] or [5], in the preparation step, a glass stack having a plurality of third inner glass layers located between a first inner glass layer and a second inner glass layer can be prepared. In the irradiation step, a first hole penetrating a portion of the first outer glass layer, the first inner glass layer, and a plurality of third inner glass layers can be formed, and a second hole penetrating the remaining third inner glass layers of the second outer glass layer, the second inner glass layer, and a plurality of third inner glass layers can be formed. The light absorption rate of the plurality of third inner glass layers can be lower than the light absorption rate of the first outer glass layer and the second outer glass layer. In this case, by making the light absorption rate of the plurality of third inner glass layers lower than the light absorption rate of the first outer glass layer and the second outer glass layer, in both the process of forming the first hole and the process of forming the second hole, the vaporized components generated by the laser light can be released to the outside of the first hole and the second hole, while shortening the time required for the laser light irradiation step. Therefore, according to the circuit board manufacturing method described above [6], holes for setting connection components can be easily formed.

[0020] [7] The method for manufacturing a circuit board according to any one of [1] to [6], wherein the plurality of glass layers can each be a glass plate. According to the method for manufacturing a circuit board described in [7] above, a glass laminate having a plurality of glass layers stacked on it can be easily prepared.

[0021] [8] According to the method for manufacturing a circuit board according to any one of [1] to [7], the plurality of glass layers can be bonded together by an adhesive. In this case, even if a defect exists in any one of the plurality of glass layers, since the plurality of glass layers are bonded together by an adhesive, the defect is unlikely to affect the other glass layers. Therefore, according to the method for manufacturing a circuit board according to [8] above, the mechanical strength of the glass layer stack can be improved.

[0022] [9] Another aspect of the present invention relates to a circuit board. The circuit board comprises: a glass laminate having a first surface and a second surface located on a side opposite to the first surface, and having a plurality of glass layers laminated thereon; a first terminal formed on the first surface; and a second terminal formed on the second surface and electrically connected to the first terminal. The plurality of glass layers have a first outer glass layer including the first surface, and a first inner glass layer bonded to the first outer glass layer on a side opposite to the first surface. A through-hole is formed in the glass laminate extending from the first surface toward the second surface. The light absorption rate of the first inner glass layer is lower than that of the first outer glass layer.

[0023]

[10] According to the circuit board of [9], the first inner glass layer may include the second surface.

[0024]

[11] According to the circuit board of [9], the plurality of glass layers may further have a second outer glass layer including a second surface. The light absorption rate of the first inner glass layer may be lower than that of the second outer glass layer.

[0025]

[12] According to the circuit board of

[11] , the plurality of glass layers may further have a second inner glass layer bonded to the second outer glass layer on the side opposite to the second surface. The light absorption rate of the second inner glass layer may be lower than that of the second outer glass layer.

[0026]

[13] According to the circuit board described in

[12] , the light absorption rate of the second inner glass layer may be lower than that of the first outer glass layer.

[0027]

[14] According to the circuit board of

[12] or

[13] , the plurality of glass layers may further have a plurality of third inner glass layers located between the first inner glass layer and the second inner glass layer. The light absorption rate of the plurality of third inner glass layers may be lower than the light absorption rate of the first outer glass layer and the light absorption rate of the second outer glass layer.

[0028]

[15] The circuit board according to any one of [9] to

[14] , wherein the plurality of glass layers may be glass plates.

[0029]

[16] The circuit board according to any one of [9] to

[15] , wherein the plurality of glass layers can be bonded by an adhesive. Attached Figure Description

[0030] Figure 1 shows an example of a circuit board according to the first embodiment of the present invention.

[0031] Figures 2(a) to (d) are cross-sectional views illustrating the manufacturing method of the circuit board shown in Figure 1.

[0032] Figures 3(a) to (d) are cross-sectional views illustrating the manufacturing method of the circuit board shown in Figure 1, showing the process performed after the process shown in Figure 2.

[0033] Figure 4 shows an example of a circuit board according to the second embodiment of the present invention.

[0034] Figures 5(a) to (d) are cross-sectional views illustrating the manufacturing method of the circuit board shown in Figure 4.

[0035] Figures 6(a) to (d) are cross-sectional views illustrating the manufacturing method of the circuit board shown in Figure 4, showing the process performed after the process shown in Figure 5.

[0036] Figure 7 shows an example of a circuit board according to the third embodiment of the present invention.

[0037] Figures 8(a) to (e) are cross-sectional views illustrating the manufacturing method of the circuit board shown in Figure 7. Detailed Implementation

[0038] Hereinafter, several embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the following description, the same or corresponding parts will be marked with the same symbols, and repeated descriptions will be omitted. Furthermore, regarding positional relationships such as up, down, left, and right, unless otherwise specified, the positional relationships shown in the accompanying drawings will be used. In the description and technical solutions of this specification, the terms "left," "right," "front," "back," "up," "down," "above," and "below" are used for illustrative purposes only and do not necessarily imply that these relative positions are always accurate. Moreover, the dimensional ratios of the accompanying drawings are not limited to those shown in the illustrations. Furthermore, in this specification, the term "process" is not limited to an independent process; even when it is difficult to clearly distinguish it from other processes, it is included in this terminology as long as the desired effect of the process is achieved.

[0039] [First Implementation]

[0040] Referring to Figures 1 to 3, the circuit board and the method for manufacturing the circuit board according to the first embodiment of the present invention will be described.

[0041] (Structure of the circuit board)

[0042] First, referring to FIG1, the structure of the circuit board according to the first embodiment will be described. FIG1 shows an example of the circuit board according to the first embodiment. As shown in FIG1, the circuit board 1 is, for example, the core substrate of the packaging substrate, and includes a glass laminate 10, a first terminal 20, a second terminal 30, and a connecting member 40. In the circuit board 1, the glass laminate 10 functions as a substrate and has a first surface 10a and a second surface 10b located on the side opposite to the first surface 10a.

[0043] The glass laminate 10 is constructed by stacking multiple glass layers; in this embodiment, it is constructed by stacking four glass layers. As shown in FIG1, the glass laminate 10 has a first outer glass layer 11, a second outer glass layer 12, a first inner glass layer 13, and a second inner glass layer 14 as four glass layers. In this embodiment, the first outer glass layer 11, the second outer glass layer 12, the first inner glass layer 13, and the second inner glass layer 14 are all glass plates.

[0044] In the glass laminate 10, the first outer glass layer 11 and the second outer glass layer 12 constitute the outermost layer. Therefore, in this embodiment, the first outer glass layer 11 includes a first surface 10a as its surface, and the second outer glass layer 12 includes a second surface 10b as its surface.

[0045] In the glass laminate 10, the first inner glass layer 13 is bonded to the first outer glass layer 11 on the side opposite to the first surface 10a, and the second inner glass layer 14 is bonded to the second outer glass layer 12 on the side opposite to the second surface 10b. Furthermore, the first inner glass layer 13 and the second inner glass layer 14 are bonded to each other. Therefore, in the glass laminate 10, the first outer glass layer 11, the first inner glass layer 13, the second inner glass layer 14, and the second outer glass layer 12 are stacked sequentially. In this embodiment, the first outer glass layer 11, the second outer glass layer 12, the first inner glass layer 13, and the second inner glass layer 14 are bonded together by adhesive A.

[0046] In the glass stack 10, the light absorption rates of the first outer glass layer 11 and the first inner glass layer 13 are different, and the light absorption rates of the second outer glass layer 12 and the second inner glass layer 14 are different. Specifically, the light absorption rate of the first inner glass layer 13 is lower than that of the first outer glass layer 11, and the light absorption rate of the second inner glass layer 14 is lower than that of the second outer glass layer 12. The light absorption rate of the second inner glass layer 14 may be lower than that of the first outer glass layer 11. Here, light absorption rate refers to the proportion of light absorbed by each glass layer when light is incident on it. The higher the light absorption rate, the easier it is to absorb the incident light; the lower the light absorption rate, the less likely it is to absorb the incident light. Light absorption rate can be expressed, for example, using the absorption coefficient.

[0047] The light absorption rate of the first outer glass layer 11 is, for example, 0.5 cm. -1 Above and 3.5cm -1 Hereinafter, the light absorption rate of the first inner glass layer 13 is, for example, 0.1 cm. -1 Above and 1.0cm -1 The light absorption rate of the second outer glass layer 12 is, for example, 0.5 cm⁻¹. -1 Above and 3.5cm -1 Hereinafter, the light absorption rate of the second inner glass layer 14 is, for example, 0.1 cm. -1 Above and 1.0cm -1 the following.

[0048] As shown in Figure 1, a first terminal 20 is formed on a first surface 10a, and a second terminal 30 is formed on a second surface 10b. The first terminal 20 and the second terminal 30 are electrically connected to each other. In this embodiment, a through hole H is formed in the glass laminate 10, extending from the first surface 10a toward the second surface 10b. The first terminal 20 and the second terminal 30 are electrically connected to each other via a connecting member 40 disposed in the through hole H. The connecting member 40 may be, for example, a wiring or a via.

[0049] (Manufacturing method of circuit board)

[0050] Next, referring to Figures 2 and 3, the manufacturing method of the circuit board 1 will be described. Figures 2(a) to (d) are cross-sectional views for explaining the manufacturing method of the circuit board shown in Figure 1. Figures 3(a) to (d) are cross-sectional views for explaining the manufacturing method of the circuit board shown in Figure 1, showing the processes performed after the process shown in Figure 2.

[0051] The circuit board 1 can be manufactured, for example, through the following steps (a) to (c). That is, the manufacturing method of the circuit board 1 includes the following steps (a) to (c).

[0052] Step a) Prepare a glass laminate having a first surface and a second surface as a substrate, and have multiple glass layers stacked thereon, wherein the multiple glass layers have a first outer glass layer including the first surface, a second outer glass layer including the second surface, a first inner glass layer bonded to the first outer glass layer on the side opposite to the first surface, and a second inner glass layer bonded to the second outer glass layer on the side opposite to the second surface.

[0053] Step b), irradiating the glass laminate with laser light.

[0054] Step c), forming the connecting component, the first terminal and the second terminal.

[0055] Furthermore, the process of irradiating the glass laminate with laser light in b) above includes the following steps.

[0056] Step b1) forms a first hole by irradiating the first surface with laser light, extending from the first surface toward the second surface and penetrating the first outer glass layer and the first inner glass layer.

[0057] Step b2), repeat step b1 above.

[0058] In step b3), a second hole is formed by irradiating the second surface with laser light, extending from the second surface toward the first surface, penetrating the second outer glass layer and the second inner glass layer, and communicating with the first hole.

[0059] Step b4), repeat step b3 above.

[0060] [Process (a)]

[0061] Step (a) is the process of preparing the glass laminate 10. In step (a) of this embodiment, a glass laminate 10 having a first surface 10a and a second surface 10b and having multiple glass layers laminated thereon is prepared. The glass laminate 10 is, for example, a glass substrate. In this case, the glass laminate 10 may be, for example, a glass substrate with a thickness of 0.05 mm or more and 1.65 mm or less.

[0062] As shown in Figure 2(a), the glass laminate 10 prepared in step (a) of this embodiment has a first outer glass layer 11, a second outer glass layer 12, a first inner glass layer 13, and a second inner glass layer 14 as multiple glass layers. In the glass laminate 10 prepared in step (a), the first outer glass layer 11, the second outer glass layer 12, the first inner glass layer 13, and the second inner glass layer 14 are all glass plates. The first outer glass layer 11, the second outer glass layer 12, the first inner glass layer 13, and the second inner glass layer 14 are respectively made of, for example, alkali silicate glass, alkali-free glass, quartz glass, etc.

[0063] In the glass laminate 10, the first outer glass layer 11 and the second outer glass layer 12 constitute the outermost layer. Therefore, in the glass laminate 10 prepared in step (a), the first outer glass layer 11 includes a first surface 10a as its surface, and the second outer glass layer 12 includes a second surface 10b as its surface.

[0064] In the glass laminate 10 prepared in step (a), the first inner glass layer 13 is bonded to the first outer glass layer 11 on the side opposite to the first surface 10a, and the second inner glass layer 14 is bonded to the second outer glass layer 12 on the side opposite to the second surface 10b. Furthermore, the first inner glass layer 13 and the second inner glass layer 14 are bonded to each other. Therefore, in the glass laminate 10 prepared in step (a), the first outer glass layer 11, the first inner glass layer 13, the second inner glass layer 14, and the second outer glass layer 12 are sequentially stacked. The first outer glass layer 11, the second outer glass layer 12, the first inner glass layer 13, and the second inner glass layer 14 are bonded together by adhesive A.

[0065] In the glass laminate 10 prepared in step (a), the light absorption rates of the first outer glass layer 11 and the first inner glass layer 13 are different from each other, and the light absorption rates of the second outer glass layer 12 and the second inner glass layer 14 are different from each other. Specifically, the light absorption rate of the first inner glass layer 13 is lower than that of the first outer glass layer 11, and the light absorption rate of the second inner glass layer 14 is lower than that of the second outer glass layer 12. In the glass laminate 10 prepared in step (a), the light absorption rate of the second inner glass layer 14 may be lower than that of the first outer glass layer 11.

[0066] In the glass laminate 10 prepared in step (a), the light absorption rate of the first outer glass layer 11 is, for example, 0.5 cm. -1 Above and 3.5cm -1 Hereinafter, the light absorption rate of the first inner glass layer 13 is, for example, 0.1 cm. -1 Above and 1.0cm -1 Below. In the glass laminate 10 prepared in process (a), the light absorption rate of the second outer glass layer 12 is, for example, 0.5 cm. -1 Above and 3.5cm -1 Hereinafter, the light absorption rate of the second inner glass layer 14 is, for example, 0.1 cm. -1 Above and 1.0cm -1 the following.

[0067] To achieve a structure in which the light absorption rates of the first outer glass layer 11 and the first inner glass layer 13 are different, for example, the colors of the first outer glass layer 11 and the first inner glass layer 13 can be different. Similarly, to achieve a structure in which the light absorption rates of the second outer glass layer 12 and the second inner glass layer 14 are different, for example, the colors of the second outer glass layer 12 and the second inner glass layer 14 can be different.

[0068] In the glass laminate 10 prepared in step (a), the thicknesses of the first outer glass layer 11, the second outer glass layer 12, the first inner glass layer 13, and the second inner glass layer 14 may be the same or different from each other. The thicknesses of the first outer glass layer 11, the second outer glass layer 12, the first inner glass layer 13, and the second inner glass layer 14 are, for example, 0.035 mm or more and 0.7 mm or less, preferably 0.05 mm or more and 0.5 mm or less, and more preferably 0.1 mm or more and 0.3 mm or less.

[0069] [Process (b)]

[0070] Step (b) is the process of irradiating the glass laminate 10 with laser light. In step (b), firstly, the first surface 10a of the glass laminate 10 is irradiated with laser light. In step (b) of this embodiment, as shown in FIG2(b), the first surface 10a is irradiated with laser light L using a laser irradiation device 100. In this case, the laser irradiation device 100 identifies a positioning mark pre-set on the first surface 10a and irradiates the positioning mark with laser light L. In this embodiment, a plurality of the above-mentioned positioning marks are provided on the first surface 10a. The above-mentioned positioning marks are provided, for example, by etching or laser processing the first surface 10a.

[0071] As the laser irradiation device 100, known laser irradiation devices such as Nd:YAG (Neodymium-doped Yttrium Aluminum Garnet) lasers, lasers covering the near-infrared to visible and even ultraviolet regions formed by combining Nd:YAG lasers with wavelength conversion, KrF excimer lasers with a wavelength of 248 nm, ArF excimer lasers with a wavelength of 193 nm, and F2 excimer lasers with a wavelength of 157 nm can be used. From a processability point of view, Nd:YAG lasers are preferred as the laser irradiation device 100. When using an Nd:YAG laser as the laser irradiation device 100, a laser with the third harmonic wavelength (355 nm) is used. Furthermore, when using an Nd:YAG laser as the laser irradiation device 100, the pulse width of the Nd:YAG laser is set to, for example, 100 fs or more and 1 ns or less.

[0072] In step (b) of this embodiment, a first hole H1 is formed in the glass laminate 10 by irradiating the first surface 10a with laser light L, as shown in FIG2 (c). The first hole H1 extends from the first surface 10a toward the second surface 10b and penetrates the first outer glass layer 11 and the first inner glass layer 13. That is, in step (b) of this embodiment, the first hole H1 is formed by irradiating the first surface 10a with laser light L. The first hole H1 formed by the above method has, for example, a diameter of 0.02 mm or more and 0.15 mm or less.

[0073] Next, the first hole H1 is formed by repeatedly irradiating it with the laser light L. Thus, as shown in FIG2(d), a plurality of first holes H1 are formed in the glass laminate 10. The spacing between the plurality of first holes H1 is, for example, 0.04 mm or more and 1.0 mm or less. In the example shown in FIG2(d), three first holes H1 are formed in the glass laminate 10.

[0074] Next, the glass laminate 10 is flipped vertically, and laser light is irradiated onto the second surface 10b of the glass laminate 10. In step (b) of this embodiment, as shown in FIG3(a), laser light L is irradiated onto the second surface 10b using a laser irradiation device 100. In this case, similar to irradiating laser light L onto the first surface 10a, the laser irradiation device 100 identifies a positioning mark pre-set on the second surface 10b and irradiates the positioning mark with laser light L. Here, the positioning mark set on the second surface 10b is set at a position corresponding to the positioning mark set on the first surface 10a.

[0075] In step (b) of this embodiment, a second hole H2 is formed in the glass laminate 10 by irradiating the second surface 10b with laser light L, extending from the second surface 10b toward the first surface 10a and penetrating the second outer glass layer 12 and the second inner glass layer 14. That is, in step (b) of this embodiment, the second hole H2 is formed by irradiating the second surface 10b with laser light L. The diameter of the second hole H2 formed by irradiating the second surface 10b with laser light L is the same as the diameter of the first hole H1.

[0076] As described above, the positioning mark provided on the second surface 10b is positioned at a position corresponding to the positioning mark provided on the first surface 10a. Therefore, the second hole H2 formed in step (b) communicates with the first hole H1, thereby forming a through hole H in the glass laminate 10 that extends from the first surface 10a toward the second surface 10b. In step (b) of this embodiment, a through hole H is formed that extends from the first surface 10a toward the second surface 10b through the first outer glass layer 11, the first inner glass layer 13, the second inner glass layer 14, and the second outer glass layer 12.

[0077] Next, the second hole H2 is formed by repeated irradiation with the laser light L. Thus, as shown in FIG3(c), a plurality of second holes H2 are formed in the glass laminate 10, forming a plurality of through holes H. The spacing between the plurality of second holes H2 is, for example, the same as the spacing between the plurality of first holes H1. That is, in this embodiment, the spacing between the plurality of through holes H is, for example, the same as the spacing between the plurality of first holes H1. In the example shown in FIG3(c), three through holes H are formed in the glass laminate 10.

[0078] [Process (c)]

[0079] Step (c) is the process of forming the first terminal 20, the second terminal 30, and the connecting member 40 on the glass laminate 10. In step (c) of this embodiment, firstly, a conductive material is filled into the through hole H to form a through hole as the connecting member 40. In this case, the connecting member 40 is formed by filling the through hole H with a conductive paste as a conductive material. The conductive paste may contain, for example, copper.

[0080] Next, a first terminal 20 is formed on the first surface 10a, and a second terminal 30 is formed on the second surface 10b in a manner electrically connected to the first terminal 20. In step (c) of this embodiment, the second terminal 30 is formed on the second surface 10b in a manner electrically connected to the first terminal 20 via a connecting member 40. Thus, as shown in FIG3 (d), the first terminal 20 and the second terminal 30 are formed to be electrically connected to each other via the connecting member 40.

[0081] The circuit board 1 shown in Figure 1 is manufactured through the above processes.

[0082] As explained above, in the manufacturing method of the circuit board 1 according to this embodiment, the light absorption rate of the first inner glass layer 13 is lower than that of the first outer glass layer 11. That is, in step (b), the time required for the laser light L to penetrate the first inner glass layer 13 is longer than the time required for the laser light L to penetrate the first outer glass layer 11. On the other hand, the time required for the laser light L to penetrate the first inner glass layer 13 is shorter than the time required for the alignment of the irradiation position of the laser light L. Therefore, by making the light absorption rate of the first inner glass layer 13 lower than that of the first outer glass layer 11, during the formation of the first hole H1, the vaporized components can be released to the outside of the hole while the laser light L penetrates the first inner glass layer 13, thus shortening the time required for the irradiation step of the laser light L. As a result, according to the manufacturing method of the circuit board 1, the through hole H for providing the connecting member 40 can be easily formed.

[0083] In the manufacturing method of the circuit board 1, even in a glass laminate with a structure of three or more layers, such as the glass laminate 10, during the formation of the first hole H1, it is possible to release vaporized components to the outside of the first hole H1 while the laser light L penetrates the first inner glass layer 13, thereby shortening the time required for the laser light L irradiation process. Therefore, according to the manufacturing method of the circuit board 1, even if the glass laminate has a structure of three or more layers, it is possible to easily form a through hole H for providing the connecting member 40.

[0084] In the manufacturing method of the circuit board 1, the light absorption rate of the second inner glass layer 14 is lower than that of the second outer glass layer 12. In this case, during the formation of the second hole H2, it is possible to release the vaporized components to the outside of the second hole H2 while the laser light L penetrates the second inner glass layer 14, thereby shortening the time required for the irradiation process of the laser light L. Therefore, according to the manufacturing method of the circuit board 1, it is possible to further simplify the formation of the through hole H for providing the connecting member 40.

[0085] In the manufacturing method of the circuit board 1, the first outer glass layer 11, the second outer glass layer 12, the first inner glass layer 13, and the second inner glass layer 14 are all glass plates. Therefore, according to the manufacturing method of the circuit board 1, in step (a), a glass laminate 10 having multiple glass layers stacked can be easily prepared.

[0086] In the manufacturing method of the circuit board 1, the first outer glass layer 11, the second outer glass layer 12, the first inner glass layer 13, and the second inner glass layer 14 are bonded together by adhesive A. In this case, even if defects exist in any of the glass layers 11, 12, 13, and 14, since each glass layer is bonded together by adhesive A, the defects are unlikely to affect the other glass layers. Therefore, according to the manufacturing method of the circuit board 1, the mechanical strength of the glass layer stack 10 can be improved.

[0087] [Second Implementation]

[0088] Next, referring to FIGS. 4 to 6, the circuit board and the method for manufacturing the circuit board according to the second embodiment of the present invention will be described. Hereinafter, the aspects that differ from those of the first embodiment will be mainly described, and descriptions that are the same as or repeated in the first embodiment will sometimes be omitted.

[0089] (Structure of the circuit board)

[0090] First, referring to FIG4, the structure of the circuit board 1A according to the second embodiment will be described. FIG4 shows an example of the circuit board according to the second embodiment of the present invention. As shown in FIG4, the circuit board 1A is, for example, the core substrate of the packaging substrate, and includes a glass laminate 10A, a first terminal 20, a second terminal 30, and a connecting member 40. Similar to the glass laminate 10, the glass laminate 10A has a first surface 10a and a second surface 10b.

[0091] Similar to the glass laminate 10, the glass laminate 10A is constructed by stacking multiple glass layers; in this embodiment, it is constructed by stacking six glass layers. As shown in FIG4, the glass laminate 10A has a first outer glass layer 11, a second outer glass layer 12, a first inner glass layer 13, a second inner glass layer 14, and multiple third inner glass layers 15a and 15b as six glass layers. In this embodiment, the first outer glass layer 11, the second outer glass layer 12, the first inner glass layer 13, the second inner glass layer 14, and the multiple third inner glass layers 15a and 15b are glass plates.

[0092] In the glass laminate 10A, the first outer glass layer 11 and the second outer glass layer 12 constitute the outermost layer. Therefore, in this embodiment, the first outer glass layer 11 includes a first surface 10a as its surface, and the second outer glass layer 12 includes a second surface 10b as its surface.

[0093] In the glass laminate 10A, a plurality of third inner glass layers 15a and 15b are located between the first inner glass layer 13 and the second inner glass layer 14. Specifically, the third inner glass layer 15a is bonded to the first inner glass layer 13 on the side opposite to the first surface 10a, and the third inner glass layer 15b is bonded to the second inner glass layer 14 on the side opposite to the second surface 10b. Furthermore, the third inner glass layers 15a and 15b are bonded to each other. Therefore, in the glass laminate 10A, the first outer glass layer 11, the first inner glass layer 13, the third inner glass layer 15a, the third inner glass layer 15b, the second inner glass layer 14, and the second outer glass layer 12 are stacked sequentially. In this embodiment, the first outer glass layer 11, the second outer glass layer 12, the first inner glass layer 13, the second inner glass layer 14, and the plurality of third inner glass layers 15a and 15b are respectively bonded by adhesive A.

[0094] In the glass laminate 10A, the light absorption rates of the third inner glass layers 15a and 15b are different from those of the first outer glass layer 11 and the second outer glass layer 12. Specifically, the light absorption rates of the third inner glass layers 15a and 15b are lower than those of the first outer glass layer 11 and the second outer glass layer 12.

[0095] The light absorption rate of the multiple third inner glass layers 15a and 15b is, for example, 0.1 cm⁻¹. -1 Above and 1.0cm -1 The light absorption rate of the third inner glass layer 15a and the light absorption rate of the third inner glass layer 15b can be the same or the same for each other.

[0096] The structures of the first terminal 20, the second terminal 30, and the connecting member 40 in the glass laminate 10A are the same as those in the glass laminate 10, so detailed descriptions are omitted.

[0097] (Manufacturing method of circuit board)

[0098] Next, referring to Figures 5 and 6, the manufacturing method of the circuit board 1A will be described. Figure 5 is a cross-sectional view for explaining the manufacturing method of the circuit board shown in Figure 4. Figure 6 is a cross-sectional view for explaining the manufacturing method of the circuit board shown in Figure 4, showing the process after the process shown in Figure 5.

[0099] The circuit board 1A can be manufactured, for example, through the following steps (d) to (f). That is, the manufacturing method of the circuit board 1A includes the following steps (d) to (f).

[0100] Step d) is a step of preparing a glass laminate, which has a first surface and a second surface as a substrate and has a plurality of glass layers stacked thereon. The plurality of glass layers have a first outer glass layer including the first surface, a second outer glass layer including the second surface, a first inner glass layer bonded to the first outer glass layer on the side opposite to the first surface, a second inner glass layer bonded to the second outer glass layer on the side opposite to the second surface, and a plurality of third inner glass layers located between the first inner glass layer and the second inner glass layer.

[0101] Step e), irradiating the glass laminate with laser light.

[0102] Process f), forming the connecting component, the first terminal and the second terminal.

[0103] Furthermore, the process of irradiating the glass laminate with laser light in step e) above includes the following steps.

[0104] In step e1, a first hole is formed by irradiating the first surface with laser light, extending from the first surface toward the second surface and penetrating the first outer glass layer, the first inner glass layer, and a portion of the third inner glass layers among a plurality of third inner glass layers.

[0105] Step e2), repeat step e1 above.

[0106] In step e3, a second hole is formed by irradiating the second surface with laser light, extending from the second surface toward the first surface, penetrating the second outer glass layer, the second inner glass layer, and the remaining third inner glass layer among a plurality of third inner glass layers, and communicating with the first hole.

[0107] Step e4), repeat step e3 above.

[0108] [Process (d)]

[0109] Step (d) is the process of preparing the glass laminate 10A. In step (d) of this embodiment, a glass laminate 10A having a first surface 10a and a second surface 10b and having multiple glass layers laminated thereon is prepared. The glass laminate 10A is, for example, a glass substrate. In this case, the glass laminate 10A may be, for example, a glass substrate with a thickness of 0.05 mm or more and 1.65 mm or less.

[0110] As shown in Figure 5(a), the glass laminate 10A prepared in step (d) of this embodiment has a first outer glass layer 11, a second outer glass layer 12, a first inner glass layer 13, a second inner glass layer 14, and a plurality of third inner glass layers 15a and 15b as multiple glass layers. The plurality of third inner glass layers 15a and 15b are also made of, for example, alkali silicate glass, alkali-free glass, quartz glass, etc.

[0111] In the glass laminate 10A, the first outer glass layer 11 and the second outer glass layer 12 also constitute the outermost layer. Therefore, in the glass laminate 10A prepared in step (d), the first outer glass layer 11 also includes a first surface 10a as its surface, and the second outer glass layer 12 also includes a second surface 10b as its surface.

[0112] In the glass laminate 10A prepared in step (d), a plurality of third inner glass layers 15a and 15b are located between the first inner glass layer 13 and the second inner glass layer 14. Specifically, the third inner glass layer 15a is bonded to the first inner glass layer 13 on the side opposite to the first surface 10a, and the third inner glass layer 15b is bonded to the second inner glass layer 14 on the side opposite to the second surface 10b. Furthermore, the third inner glass layers 15a and 15b are bonded to each other. Therefore, in the glass laminate 10A prepared in step (d), the first outer glass layer 11, the first inner glass layer 13, the third inner glass layer 15a, the third inner glass layer 15b, the second inner glass layer 14, and the second outer glass layer 12 are stacked sequentially. The first outer glass layer 11, the second outer glass layer 12, the first inner glass layer 13, the second inner glass layer 14, and the plurality of third inner glass layers 15a and 15b are respectively bonded by adhesive A.

[0113] In the glass laminate 10A prepared in step (d), the light absorption rates of the third inner glass layers 15a and 15b are different from those of the first outer glass layer 11 and the second outer glass layer 12. Specifically, the light absorption rates of the third inner glass layers 15a and 15b are lower than those of the first outer glass layer 11 and the second outer glass layer 12. Furthermore, the relationships between the light absorption rates of the first outer glass layer 11 and the first inner glass layer 13, and between the light absorption rates of the second outer glass layer 12 and the second inner glass layer 14, are the same as those in the glass laminate 10, and therefore detailed explanations are omitted.

[0114] In the glass laminate 10A prepared in process (d), the light absorption rate of the third inner glass layers 15a and 15b is, for example, 0.1 cm. -1 Above and 1.0cm -1 The following is a further explanation. Furthermore, the ranges of light absorption rates for the first outer glass layer 11, the second outer glass layer 12, the first inner glass layer 13, and the second inner glass layer 14 in the glass laminate 10A are the same as those in the glass laminate 10, therefore detailed explanations are omitted.

[0115] In order to achieve a structure in which the light absorption rates of the first outer glass layer 11 and the second outer glass layer 12 are different from the light absorption rates of the plurality of third inner glass layers 15a and 15b, for example, the colors of the first outer glass layer 11 and the second outer glass layer 12 can be different from the colors of the plurality of third inner glass layers 15a and 15b.

[0116] In the glass laminate 10A prepared in step (d), the thicknesses of the plurality of third inner glass layers 15a and 15b may be the same as, or different from, the thicknesses of the first outer glass layer 11, the second outer glass layer 12, the first inner glass layer 13, and the second inner glass layer 14. The thicknesses of the plurality of third inner glass layers 15a and 15b are, for example, 0.035 mm or more and 0.7 mm or less, preferably 0.05 mm or more and 0.5 mm or less, and more preferably 0.1 mm or more and 0.3 mm or less.

[0117] [Process (e)]

[0118] Step (e) is the process of irradiating the glass laminate 10A with laser light. In step (e), firstly, the first surface 10a of the glass laminate 10A is irradiated with laser light. In step (e) of this embodiment, as shown in FIG5(b), the first surface 10a is irradiated with laser light L using a laser irradiation device 100.

[0119] In step (e) of this embodiment, a first hole H1A is formed in the glass laminate 10A by irradiating the first surface 10a with laser light L, as shown in FIG5(c). The first hole H1A extends from the first surface 10a toward the second surface 10b and penetrates the first outer glass layer 11, the first inner glass layer 13, and the third inner glass layer 15a. The diameter of the first hole H1A is, for example, the same as the diameter of the first hole H1.

[0120] Next, the first hole H1A is formed by repeatedly irradiating it with the laser light L. Thus, as shown in FIG5(d), a plurality of first holes H1A are formed in the glass laminate 10A. The spacing between the plurality of first holes H1 is, for example, the same as the spacing between the plurality of first holes H1. In the example shown in FIG5(d), three first holes H1 are formed in the glass laminate 10A.

[0121] Next, the glass laminate 10A is reversed vertically, and laser light is irradiated onto the second surface 10b of the glass laminate 10A. In step (e) of this embodiment, as shown in FIG6(a), laser light L is irradiated onto the second surface 10b using a laser irradiation device 100.

[0122] In step (e) of this embodiment, a second hole H2A is formed in the glass laminate 10A by irradiating the second surface 10b with laser light L, extending from the second surface 10b toward the first surface 10a and penetrating the second outer glass layer 12, the second inner glass layer 14, and the third inner glass layer 15b. That is, in step (e) of this embodiment, the second hole H2A is formed by irradiating the second surface 10b with laser light L. The diameter of the second hole H2A formed by irradiating the second surface 10b with laser light L is, for example, the same as the diameter of the first hole H1A.

[0123] The second hole H2A formed in step (e) communicates with the first hole H1A, thereby forming a through hole H that extends from the first surface 10a toward the second surface 10b. In step (e) of this embodiment, a through hole H is formed that extends from the first surface 10a toward the second surface 10b through the first outer glass layer 11, the first inner glass layer 13, the third inner glass layer 15a, the second inner glass layer 14, the third inner glass layer 15b, and the second outer glass layer 12.

[0124] Next, the second hole H2A is formed by repeatedly irradiating it with the laser light L. Thus, as shown in FIG6(c), a plurality of second holes H2A and a plurality of through holes H are formed in the glass laminate 10A. The spacing between the plurality of second holes H2A is, for example, the same as the spacing between the plurality of first holes H1A. That is, in this embodiment, the spacing between the plurality of through holes H is, for example, the same as the spacing between the plurality of first holes H1A. In the example shown in FIG6(c), three through holes H are formed in the glass laminate 10A.

[0125] [Process (f)]

[0126] Step (f) is the process of forming a first terminal 20, a second terminal 30, and a connecting member 40 on the glass laminate 10A. In step (f) of this embodiment, the first terminal 20 and the second terminal 30, which are electrically connected to each other through the connecting member 40, are formed in the same way as in step (c), as shown in (d) of FIG6.

[0127] The circuit board 1A shown in Figure 4 is manufactured through the above processes.

[0128] As explained above, in the manufacturing method of the circuit board 1A, the light absorption rates of the plurality of third inner glass layers 15a and 15b are lower than the light absorption rates of the first outer glass layer 11 and the second outer glass layer 12. In the manufacturing method of the circuit board 1A, by making the light absorption rates of the plurality of third inner glass layers 15a and 15b lower than the light absorption rates of the first outer glass layer 11 and the second outer glass layer 12, in both the process of forming the first hole H1A and the process of forming the second hole H2A, it is possible to release the vaporized components generated by the laser light L to the outside of the first hole H1A and the second hole H2A, while shortening the time required for the irradiation process of the laser light L. Therefore, the manufacturing method of the circuit board 1A can easily form through holes H for setting connecting components.

[0129] [Third Implementation]

[0130] Next, referring to FIGS. 7 and 8, the circuit board and the method for manufacturing the circuit board according to the third embodiment of the present invention will be described. Hereinafter, the aspects that differ from those of the first embodiment will be mainly described, and descriptions that are the same as or repeated in the first embodiment will sometimes be omitted.

[0131] (Structure of the circuit board)

[0132] First, referring to FIG7, the structure of the circuit board 1B according to the third embodiment will be described. FIG7 shows an example of the circuit board according to the third embodiment. As shown in FIG7, the circuit board 1B is, for example, the core substrate of the packaging substrate, and includes a glass laminate 10B, a first terminal 20, a second terminal 30, and a connecting member 40. Similar to the glass laminate 10, the glass laminate 10B has a first surface 10a and a second surface 10b.

[0133] Similar to the glass laminate 10, the glass laminate 10B is also constructed by stacking multiple glass layers; in this embodiment, it is constructed by stacking two glass layers. As shown in FIG7, the glass laminate 10B has a first outer glass layer 11 and a first inner glass layer 13 as two glass layers. In this embodiment, the first outer glass layer 11 and the first inner glass layer 13 are both glass plates.

[0134] In the glass laminate 10B, the first outer glass layer 11 and the first inner glass layer 13 constitute the outermost layer. Therefore, in this embodiment, the first outer glass layer 11 includes a first surface 10a as its surface, and the first inner glass layer 13 includes a second surface 10b as its surface. In the glass laminate 10B, the first outer glass layer 11 and the first inner glass layer 13 are stacked sequentially. In this embodiment, the first outer glass layer 11 and the first inner glass layer 13 are bonded together by an adhesive A.

[0135] The structures of the first terminal 20, the second terminal 30, and the connecting member 40 in the glass laminate 10B are the same as those in the glass laminate 10, so detailed descriptions are omitted.

[0136] (Manufacturing method of circuit board)

[0137] Next, referring to FIG8, the manufacturing method of the circuit board 1B will be described. FIG8 is a cross-sectional view for illustrating the manufacturing method of the circuit board shown in FIG7.

[0138] The circuit board 1B can be manufactured, for example, through the following steps (g) to (i). That is, the manufacturing method of the circuit board 1B includes the following steps (g) to (i).

[0139] Step g), a step of preparing a glass laminate, which serves as a substrate and has a first surface and a second surface, and has multiple glass layers stacked thereon, the multiple glass layers having a first outer glass layer including the first surface and a first inner glass layer including the second surface.

[0140] Process h), where laser light is irradiated onto the glass laminate.

[0141] Process i), forming the connecting component, the first terminal and the second terminal.

[0142] Furthermore, the process of irradiating the glass laminate with laser light in the above-mentioned h) includes the following steps.

[0143] In process h1, a first hole is formed by irradiating the first surface with laser light, extending from the first surface toward the second surface and penetrating the first outer glass layer and the first inner glass layer.

[0144] Process h2), repeating the above h1).

[0145] [Process (g)]

[0146] Step (g) is the process of preparing the glass laminate 10B. In step (g) of this embodiment, a glass laminate 10B having a first surface 10a and a second surface 10b and having multiple glass layers laminated thereon is prepared. The glass laminate 10B is, for example, a glass substrate. In this case, the glass laminate 10B may be, for example, a glass substrate with a thickness of 0.05 mm or more and 1.65 mm or less.

[0147] As shown in Figure 8(a), the glass laminate 10B prepared in step (g) of this embodiment has a first outer glass layer 11 and a first inner glass layer 13 as multiple glass layers. Since the materials of each glass layer in the glass laminate 10B are the same as those of each glass layer in the glass laminate 10, detailed description is omitted.

[0148] In the glass laminate 10B, the first outer glass layer 11 and the first inner glass layer 13 constitute the outermost layer. Therefore, in the glass laminate 10B prepared in step (g), the first outer glass layer 11 includes a first surface 10a as its surface, and the first inner glass layer 13 includes a second surface 10b as its surface. As described above, the first inner glass layer 13 is bonded to the first outer glass layer 11 on the side opposite to the first surface 10a. Therefore, in the glass laminate 10B prepared in step (g), the first outer glass layer 11 and the first inner glass layer 13 are stacked sequentially.

[0149] [Process (h)]

[0150] Step (h) is the process of irradiating the glass laminate 10B with laser light. In step (h), firstly, the first surface 10a of the glass laminate 10B is irradiated with laser light. In step (h) of this embodiment, as shown in FIG8(b), the first surface 10a of the glass laminate 10B is irradiated with laser light L using a laser irradiation device 100.

[0151] In step (h) of this embodiment, a first hole H1B is formed in the glass laminate 10B by irradiating the first surface 10a with laser light L, as shown in FIG8(c). The hole extends from the first surface 10a toward the second surface 10b, penetrating the first outer glass layer 11 and the first inner glass layer 13. The diameter of the first hole H1B is, for example, the same as the diameter of the first hole H1. As described above, in this embodiment, the glass laminate 10B has two glass layers: the first outer glass layer 11 and the first inner glass layer 13. Therefore, in step (h) of this embodiment, the first hole H1B becomes a through hole H extending from the first surface 10a toward the second surface 10b. That is, in step (h) of this embodiment, it can be said that the through hole H is formed by irradiating the glass laminate 10B with laser light.

[0152] Next, the first hole H1B (through hole H) is formed by repeatedly irradiating it with the laser light L. Thus, as shown in FIG8(d), multiple first holes H1B are formed as through holes H in the glass laminate 10B. The spacing between the multiple first holes H1B is, for example, the same as the spacing between the multiple first holes H1. In the example shown in FIG8(d), three first holes H1B (through holes H) are formed in the glass laminate 10B.

[0153] [Process (i)]

[0154] Step (i) is the process of forming a first terminal 20, a second terminal 30, and a connecting member 40 on the glass laminate 10B. In step (i) of this embodiment, the first terminal 20 and the second terminal 30, which are electrically connected to each other through the connecting member 40, are formed in the same manner as in step (c), as shown in FIG8 (e).

[0155] The circuit board 1B shown in Figure 7 is formed through the above processes.

[0156] As explained above, in the manufacturing method of circuit board 1B, the light absorption rate of the first inner glass layer 13 is lower than that of the first outer glass layer 11. Therefore, even in a glass laminate with a double-layer structure such as glass laminate 10B, during the formation of the first hole H1B (through hole H), it is possible to release vaporized components to the outside of the first hole H1B while removing the first inner glass layer 13 with laser light L, thus shortening the time required for the irradiation process of laser light L. Therefore, according to the manufacturing method of circuit board 1B, holes for providing connecting members 40 can be easily formed.

[0157] Symbol Explanation

[0158] 1, 1A, 1B - Circuit board; 10, 10A, 10B - Glass laminate; 10a - First surface; 10b - Second surface; 11 - First outer glass layer; 12 - Second outer glass layer; 13 - First inner glass layer; 14 - Second inner glass layer; 15a, 15b - Third inner glass layer; 20 - First terminal; 30 - Second terminal; A - Adhesive; H - Through hole; H1, H1A, H1B - First hole; H2, H2A - Second hole; L - Laser light.

Claims

1. A method for manufacturing a circuit board, the circuit board comprising: a substrate having a first surface and a second surface located on a side opposite to the first surface; a first terminal formed on the first surface; and a second terminal formed on the second surface and electrically connected to the first terminal, the method comprising: a step of preparing a glass laminate having the first surface and the second surface as the substrate and having a plurality of glass layers laminated thereon; and a step of irradiating the glass laminate with laser light, wherein in the preparation step, the plurality of glass layers are prepared to have a glass laminate including a first outer glass layer of the first surface and a first inner glass layer bonded to the first outer glass layer on a side opposite to the first surface, and in the irradiation step, a first hole is formed by irradiating the first surface with laser light, extending from the first surface toward the second surface through at least the first outer glass layer and the first inner glass layer, the light absorption rate of the first inner glass layer being lower than the light absorption rate of the first outer glass layer.

2. The method for manufacturing a circuit board according to claim 1, wherein, In the preparation process, the first inner glass layer, including the second surface, is prepared into a glass laminate. In the irradiation process, the first hole is formed, extending from the first surface to the second surface.

3. The method for manufacturing a circuit board according to claim 1, wherein, The preparation process further includes the glass stack comprising a second outer glass layer including the second surface, and the irradiation process further includes the formation of a second hole that extends from the second surface toward the first surface through at least the second outer glass layer and communicates with the first hole.

4. The method for manufacturing a circuit board according to claim 3, wherein, In the preparation process, the plurality of glass layers are further comprising a glass layer stack having a second inner glass layer bonded to the second outer glass layer on the side opposite to the second surface. In the irradiation process, a second hole is formed penetrating the second outer glass layer and the second inner glass layer by irradiating the second surface with the laser light. The light absorption rate of the second inner glass layer is lower than that of the second outer glass layer.

5. The method for manufacturing a circuit board according to claim 4, wherein, The light absorption rate of the second inner glass layer is lower than that of the first outer glass layer.

6. The method for manufacturing a circuit board according to claim 4 or 5, wherein, In the preparation step, a glass stack having a plurality of third inner glass layers located between the first inner glass layer and the second inner glass layer is prepared. In the irradiation step, a first hole is formed penetrating the first outer glass layer, the first inner glass layer, and a portion of the plurality of third inner glass layers. A second hole is formed penetrating the second outer glass layer, the second inner glass layer, and the remaining third inner glass layers. The light absorption rate of the plurality of third inner glass layers is lower than that of the first outer glass layer and the second outer glass layer.

7. The method for manufacturing a circuit board according to any one of claims 1 to 6, wherein, The multiple glass layers are glass plates.

8. The method for manufacturing a circuit board according to any one of claims 1 to 7, wherein, The plurality of glass layers are bonded together by an adhesive.

9. A circuit board comprising: a glass laminate having a first surface and a second surface located on a side opposite to the first surface, and having a plurality of glass layers laminated thereon; a first terminal formed on the first surface; and a second terminal formed on the second surface and electrically connected to the first terminal, the plurality of glass layers having: a first outer glass layer including the first surface; and a first inner glass layer bonded to the first outer glass layer on a side opposite to the first surface, a through hole formed in the glass laminate extending from the first surface toward the second surface, the light absorption rate of the first inner glass layer being lower than the light absorption rate of the first outer glass layer.

10. The circuit board according to claim 9, wherein, The first inner glass layer includes the second surface.

11. The circuit board according to claim 9, wherein, The plurality of glass layers further have a second outer glass layer including the second surface, wherein the light absorption rate of the first inner glass layer is lower than that of the second outer glass layer.

12. The circuit board according to claim 11, wherein, The plurality of glass layers also have a second inner glass layer bonded to the second outer glass layer on the side opposite to the second surface, the light absorption rate of the second inner glass layer being lower than that of the second outer glass layer.

13. The circuit board according to claim 12, wherein, The light absorption rate of the second inner glass layer is lower than that of the first outer glass layer.

14. The circuit board according to claim 12 or 13, wherein, The plurality of glass layers further include a plurality of third inner glass layers located between the first inner glass layer and the second inner glass layer, wherein the light absorption rate of the plurality of third inner glass layers is lower than that of the first outer glass layer and the second outer glass layer.

15. The circuit board according to any one of claims 9 to 14, wherein, The multiple glass layers are glass plates.

16. The circuit board according to any one of claims 9 to 15, wherein, The plurality of glass layers are bonded together by an adhesive.

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