Printed circuit board manufacturing method

Abstract

To prevent soldering defects of electronic components from occurring due to residues remaining on the surface of pads on which electronic components are mounted.SOLUTION: It has a substrate 12 having two main surfaces, at least one heat-dissipating conductor layer 20 formed on at least one of the two main surfaces of the substrate 12, and a solder resist layer 22 formed on the surface of the heat-dissipating conductor layer 20. A solder resist layer 22 is irradiated with a carbon dioxide laser to form a pad 73. Next, a femtosecond laser beam 64 is irradiated on the pad to remove the residue of the pad 73 and the surface of the heat-dissipating conductor layer 20 corresponding to the pad 73.SELECTED DRAWING: Figure 6

Description

[Technical field]

[0001] The present invention relates to a printed circuit board and a manufacturing method thereof, and more particularly to a printed circuit board having a laminate composed of a heat dissipation conductor layer and a solder resist layer on a heat dissipation surface, and a manufacturing method thereof. [Background technology]

[0002] In the manufacturing process of printed circuit boards according to the conventional technology, the outline and hole processing is performed, and then the surface is finished. The purpose of the surface finishing is to clean the copper foil surface, and the surface is degreased and derusted with acid. The above-mentioned printed circuit board and its manufacturing method are described in JP 2011-222962 A (Patent Document 1). In the manufacturing process of circuit boards, resin residue (smear) is generated when holes are drilled with a laser. The process of removing the smear is called desmearing.

[0003] If smear remains in the processed holes, it will prevent electrical conductivity between metals, which will cause defects such as poor electrical continuity during subsequent interlayer connections and insufficient mechanical bonding strength (delamination between layers). Therefore, it is necessary to perform a desmear process to remove smears after drilling. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2011-222962 A Summary of the Invention [Problem to be solved by the invention]

[0005] The resist of the printed circuit board is drilled with a carbon dioxide (CO2) laser beam to form pads 73 for connecting components. In the case of a resist containing nanofiller, the resin component of the resist remains as smears. [Means for solving the problem]

[0006] The present invention comprises a substrate having two main surfaces, at least one heat dissipation conductor layer formed on at least one of the two main surfaces of the substrate, and a solder resist layer formed on the surface of the heat dissipation conductor layer. The solder resist layer is formed with pads 73 by carbon dioxide (CO2) laser light. The surface of the pads 73 is irradiated with femtosecond laser light to remove the surface layer of the heat dissipation conductor layer. Effect of the Invention

[0007] In the present invention, the resist is perforated with a carbon dioxide (CO2) laser beam, and then the portion perforated with the carbon dioxide (CO2) is processed with a femtosecond laser beam to remove smears. During this processing, the surface of the conductor layer of the pad 73 is processed at the same time. By processing with a carbon dioxide (CO2) laser and femtosecond laser light, smears can be completely removed, allowing the electronic components to be mounted with good soldering. [Brief description of the drawings]

[0008] [Figure 1] FIG. 2 is a flowchart showing a method for manufacturing a printed circuit board according to the present invention. [Diagram 2] 3A to 3C are explanatory diagrams of the method for producing a printed circuit board according to the present invention. [Diagram 3] 1A to 1C are explanatory diagrams of a method for manufacturing a printed circuit board according to the present invention. [Figure 4] 3A to 3C are explanatory diagrams of the method for producing a printed circuit board according to the present invention. [Diagram 5] 3A to 3C are explanatory diagrams of the method for producing a printed circuit board according to the present invention. [Figure 6] 3A to 3C are explanatory diagrams of the method for producing a printed circuit board according to the present invention. [Figure 7] FIG. 2 is an explanatory diagram of a printed circuit board according to the present invention. [Figure 8] FIG. 2 is an explanatory diagram of a state in which electronic components are mounted on the printed circuit board of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] Hereinafter, the embodiments of the present invention will be described with reference to the attached drawings. In each drawing for explaining the embodiments of the present invention, elements and configurations having the same functions are given the same reference numerals, and the description may be omitted. In addition, the embodiments of the present invention described in this specification may be combined in part or in whole with each other.

[0010] The drawings and the following description are provided to enable those skilled in the art to fully understand the present disclosure, and are not intended to limit the subject matter described in the claims.

[0011] Hereinafter, a printed circuit board according to an embodiment will be described with reference to Fig. 7, Fig. 8, etc. Fig. 7 is a configuration diagram and an explanatory diagram of the printed circuit board of the present invention. Fig. 8 is a configuration diagram and an explanatory diagram showing a state in which electronic components such as LEDs are mounted on the printed circuit board of the present invention.

[0012] 7 and 8, the printed circuit board according to the embodiment includes a substrate 12. A large number of component mounting conductor layers 14, wiring conductor layers 16, and a circuit surface resist layer 18 are formed on the circuit surface of the substrate 12. A laminate 24 consisting of a large number of heat dissipation conductor layers 20 and a solder resist layer 22 is formed in a generally convex shape having an appropriate height on the heat dissipation surface of the substrate 12. The substrate 12 is formed, for example, from a base substrate 30 as shown in Fig. 2(a). The base substrate 30 has a thickness of 0.1 to 1.0 mm and is formed by bonding a metal layer 32 such as copper foil to the substrate 12 made of insulating resin. The substrate 12, the component mounting conductor layer 14, the wiring conductor layer 16, and the heat dissipation conductor layer 20 are formed by etching the copper foil.

[0013] In an embodiment, glass cloth epoxy resin laminates such as CS-3945 (double-sided) manufactured by Risho Kogyo Co., Ltd., CS-3940 (single-sided) manufactured by Risho Kogyo Co., Ltd., Nikaplex L-6504 manufactured by Nikkan Kogyo Co., Ltd., MCL-E-67 manufactured by Hitachi Chemical Co., Ltd., R-1705, R-1705SX, and R-1705SH manufactured by Panasonic Corporation, S11600 manufactured by Shengyi Technology Co., Ltd., and ELC-4768 manufactured by Sumitomo Bakelite Co., Ltd. may be used. In addition, in the embodiment, in addition to the glass cloth epoxy resin laminate, a paper phenol substrate, a paper epoxy substrate, a glass composite substrate, a liquid crystal polymer substrate, an alumina substrate, a polyimide substrate, etc. may be used. The component mounting conductor layer 14 is formed by etching a metal layer 32 made of copper foil having a thickness of 18 to 70 μm.

[0014] The conductor layer 14 for mounting components has two main surfaces and at least one side surface, one of which is in surface contact with the main surface of the substrate 12, and further, the side surface is in surface contact with the side surface of the first solder resist layer 18a. The side surface of the component mounting conductor layer 14 does not necessarily have to be in surface contact with the side surface of the first solder resist layer 18a. The first solder resist layer 18a covers the wiring conductor layer 16. A main surface of the second solder resist layer 18b is in surface contact with one main surface of the first solder resist layer 18a, forming a laminate having a substantially convex shape.

[0015] When electronic components that generate a large amount of heat, such as LEDs, are mounted on the component mounting conductor layer 14, it is necessary to increase the thermal conductivity around the component mounting conductor layer 14 to provide a heat dissipation effect.

[0016] The heat dissipation conductor layer 20 is formed by etching a metal layer 32 made of copper foil having a thickness of 18 to 70 μm. The heat dissipation conductor layer 20 has two main surfaces and at least one side surface, one of which is in surface contact with the main surface of the base material 12.

[0017] Generally, copper foil, which has good electrical and thermal conductivity and is inexpensive, is used for the heat dissipation conductor layer 20. However, it is known that the thermal expansion of copper foil is a major factor in warping and twisting due to thermal deformation in thin boards and low-cost boards with weak bending rigidity. According to the printed circuit board of the embodiment, a laminate 24 having a substantially convex shape is formed on the heat dissipation surface by exposing the side surface of the heat dissipation conductor layer 20 and the solder resist layer 22. As a result, the heat dissipation effect of the entire board is promoted by exposing the side surface of the heat dissipation conductor layer 20 and increasing the surface area of ​​the laminate 24, and further, the mechanical properties of the printed circuit board against warping and twisting are improved due to the accompanying reduction in thermal expansion of the copper foil.

[0018] The circuit surface resist layer 18 and the solder resist layer 22 have "resistance to etching liquid" and "resistance to ink stripping liquid" in addition to "solder resist properties," and are formed by resist printing using solder resist ink.

[0019] In this case, "etching solution resistance" refers to the property that the solder resist layer 22 is not dissolved by an etching solution, that is, etching acid resistance, and solder resist peeling resistance that the solder resist layer 22 is not peeled off by an etching solution.

[0020] Moreover, the term "ink remover solution resistance" refers to alkali resistance, i.e., the property that the solder resist layer 22 is not dissolved by an ink remover solution, and solder resist removal resistance, i.e., the property that the solder resist layer 22 is not peeled off by an ink remover solution. In the printed circuit board of the embodiment, the circuit surface resist layer 18 is formed on the circuit surface, and the solder resist layer 22 is formed on the heat dissipation surface.

[0021] The circuit surface resist layer 18 and the solder resist layer 22 each have two main surfaces and at least one side surface. On the circuit surface, the first-layer solder resist layer 18a is formed so as to cover the wiring conductor layer 16, one of the two main surfaces of the first-layer solder resist layer 18a is in surface contact with the main surface of the base material 12, and further, at least one side surface of the first-layer solder resist layer 18a is in surface contact with a side surface of the component mounting conductor layer 14.

[0022] One of the two main surfaces of the second solder resist layer 18b is in surface contact with the main surface of the first solder resist layer 18a, and the other main surface and a side surface are exposed.

[0023] In contrast, on the heat dissipation surface, the solder resist layer 22 is formed on the other of the two main surfaces of the heat dissipation conductor layer 20, and the side surfaces as well as the other main surface of the heat dissipation conductor layer 20 are exposed.

[0024] On the heat dissipation surface, the side surface of the heat dissipation conductor layer 20 and the solder resist layer 22 are exposed to form a laminate 24 having a generally convex shape. As a result, the heat dissipation effect of the entire board is promoted by the exposure of the side surface of the heat dissipation conductor layer 20 and the expansion of the surface area of ​​the laminate 24, and the heat dissipation conductor layer is also accompanied by this. For example, the mechanical properties of the printed circuit board against warping and twisting are improved by the reduction in thermal expansion of the copper foil.

[0025] In the printed circuit board according to the embodiment, in addition to the laminate 24 having a substantially convex shape on the main surface of the base material 12, a laminate having the same shape as the substantially convex laminate 24 is formed on the same main surface. A gap is formed between the side surfaces of both laminates, and the component mounting conductor layer 14 is provided at a position relative to the gap with the base material 12 as a boundary. The length of the gap parallel to the main surface of the base material 12 is shorter than the length of the component mounting conductor layer 14 parallel to the main surface of the base material 12 . In this way, the heat dissipation effect is also promoted by the fact that the component mounting conductor layer 14 is close to the side surface of the heat dissipation conductor layer 20. In the printed circuit board according to the embodiment, a through hole penetrating the base material 12 or the base material 12 and the conductor layer 14 for mounting components may be provided.

[0026] 8, the solder resist layer 22 is drilled with a CO2 laser beam. The solder resist layer 22 is also removed with a CO2 laser beam to form pads 73 for mounting electronic components. The pads 73 are irradiated with a femtosecond laser beam to remove smears on the pads 73 and to remove the surface (surface layer) of the heat dissipation conductor layer 20. An electronic component 72 that generates a large amount of heat, such as an LED, is mounted on the solder resist layer 22 , and the connection terminals of the electronic component 72 and pads 73 are electrically connected by solder 71 .

[0027] Fig. 1 is a flow chart for explaining the manufacturing process of the printed circuit board shown in Fig. 7. In the flow chart, side A is the circuit side, and side B is the heat dissipation side. The heat dissipation conductor layer 20 on side B also serves as wiring for supplying voltage to the electronic components 72.

[0028] 2 to 6 are explanatory diagrams for explaining the method for manufacturing the printed circuit board of the present invention shown in FIGS. A method for manufacturing a printed circuit board according to a preferred embodiment of the present invention will now be described with reference to these drawings. In the first step S11 shown in FIG. 1, a base substrate 30 having metal layers 32 formed on both sides of a base material 12 is prepared as shown in FIG. 2(a).

[0029] The metal layer 32 is to become the heat dissipation conductor layer 20, the component mounting conductor layer 14, and the wiring conductor layer 16 through the etching process described below, and is made of copper foil, which is an inexpensive metal with good electrical and thermal conductivity. After the end of step S11 in the manufacturing process, a pre-printing process in step S12 in the manufacturing process is performed.

[0030] In FIG. 2(b), the solder resist ink is used to perform pattern printing including resist printing on the heat dissipation surface of the base material 12 (step S13), and then the solder resist ink is cured (step S14) to form a solder resist layer 22.

[0031] Examples of solder resist ink include ultraviolet curing ink that is cured by ultraviolet light and thermosetting ink that is cured by heat (including photo development type), and an insulating resin with a thickness of 5 to 30 μm is used.

[0032] In the embodiment, after the solder resist layer 22 is formed using the solder resist ink, an etching solution is used. Therefore, the solder resist ink is required to further have "etchant resistance" so that the solder resist layer 22 is not corroded by the etching solution.

[0033] In the embodiment, examples of ultraviolet-curable solder resist inks that may be used include PLAS FINE PSR-310 (A-99F), PLAS FINE PSR-310 (SC-84), and PLAS FINE PSR-310 (SW-26) manufactured by GOO Chemical Industry Co., Ltd., SSR-1600WS110 and SSR-1600WS35 manufactured by San-ei Chemical Industry Co., Ltd., and USR-2B14-84-200 and USR-2G14-94-250 manufactured by Tamura Chemical Industry Co., Ltd.

[0034] As the thermosetting solder resist ink, LE-6000S manufactured by San-ei Chemical Industry Co., Ltd., PSR-4000 G24K, PSR-4000 LEW3, S-40 T1, etc. manufactured by Taiyo Ink Mfg. Co., Ltd. are used.

[0035] In step S15, as shown in FIG. 3(a), a pattern is printed on the circuit surface of the substrate 12 using an etching resist ink, and then the etching resist ink is cured (step S16) to form an etching resist layer 52. As the etching resist ink, an ink having a thickness of 5 to 30 μm and capable of being peeled off by an alkaline solution is used.

[0036] In the embodiment, the etching resist ink is PLAS FINE PER-51B manufactured by GOO Chemical Industry Co., Ltd., PLAS FINE PER-213 manufactured by the same company. B-5, PER-57BH, etc. may also be used. In step S17, as shown in FIG. 3(b), the heat dissipation conductor layer 20 that serves as a base for the solder resist layer 22 is formed by etching.

[0037] Ferric chloride and cupric chloride are used as etching solutions. Ferric chloride is used at a concentration of 42% or less and at a temperature of 15 to 55°C, usually around 40°C. Cupric chloride is used at a concentration of 40% or less and at a temperature of 15 to 55°C, usually around 40°C.

[0038] In the embodiment, the main component of the etching solution may be ferric chloride solution manufactured by Rasa Kogyo Co., Ltd. or copper (II) chloride dihydrate manufactured by Yoneyama Kogyo Co., Ltd., and the auxiliary components of the etching solution may be hydrochloric acid, hydrogen peroxide, etc. In step S18, as shown in FIG. 4(a), the ink is peeled off, thereby removing the etching resist layer 52. In the embodiment, as the ink stripping liquid, in addition to an aqueous sodium hydroxide solution manufactured by Kaneka Corporation, an aqueous sodium carbonate solution or the like may be used.

[0039] Sodium hydroxide is used at a concentration of 10% or less and at a temperature of 15 to 50°C, usually around 30°C. Sodium carbonate is used at a concentration of 5% or less and at a temperature of 15 to 50°C, usually around 30°C.

[0040] In the embodiment, since the ink remover liquid is used after the solder resist layer 22 is formed using the solder resist ink, the solder resist ink is further required to have "ink remover liquid resistance" so that the solder resist layer 22 is not corroded by the ink remover liquid.

[0041] A pre-printing process is performed in step S19, and in step 31, as shown in FIG. 4(b), after the pre-printing process (step S19), a pattern is printed on the circuit surface of the substrate 12 using solder resist ink, and then the solder resist ink is cured (step 32) to form a first solder resist layer 18a.

[0042] In step S33, as shown in FIG. 5(a), a pattern is printed using solder resist ink on the first solder resist layer 18a formed on the circuit surface of the substrate 12 to form a second solder resist layer 18b (circuit resist layer 18), and then the solder resist ink is cured (step 34) to form a laminate consisting of the solder resist layers.

[0043] In step S35 of the manufacturing process of the printed circuit board according to the embodiment, the outline and holes are processed, and then the surface is finished. The surface is finished to clean the copper foil surface, and degrease and remove rust with acid.

[0044] In an embodiment, the chemical abrasive may be MECBRITE CB-5612 manufactured by MEC Corporation, or TECH CL-8 manufactured by ADEKA CORPORATION, and the rust inhibitor may be ToughAce F2 manufactured by Shikoku Chemical Industry Co., Ltd., or MECSEAL CL-5018 manufactured by MEC Corporation.

[0045] Next, as shown in FIG. 5(b), a CO2 laser device 61 generates a CO2 laser beam 62, and the CO2 laser beam 62 is irradiated onto the solder resist layer 22 to form pads 73 for connecting electronic components 72 (step S36).

[0046] The scanning direction of the CO2 laser light 62 can be controlled at high speed and with high precision by controlling the galvanometer mirror. In addition, the CO2 laser device 61 has a high output and can remove the solder resist film 22.

[0047] It is preferable to use a continuous oscillation mode CO2 laser device 61. However, it is preferable to use a pulse oscillation type CO2 laser device 61 when the energy of the laser light pulse is strong and the pads 73 for irradiating the CO2 laser light 62 are discretely arranged.

[0048] The CO2 laser light 62 output from the pulsed CO2 laser device 61 is on / off controlled by a Q switch, which tends to cause variations in pulse intensity. Therefore, it is preferable to remove the solder resist layer 22 by irradiating the area to be modified with multiple laser pulses. The CO2 laser light 62 preferably has an output of 1.5 to 4.0 W and a frequency of 1 KHz to 5 KHz. In order to improve the heat dissipation properties of the solder resist layer 22, the resist contains a filler, which often has a relatively large particle size.

[0049] The solder resist layer 22 containing the filler is less processable by the CO2 laser light 62. In addition, the filler is not processed by the CO2 laser light 62 and remains on the pads 73.

[0050] In order to remove the filler with the CO2 laser beam 62, the focal offset is set in the positive direction and processing is performed with a relatively high output, causing melting of both the surface and bottom of the via. When the solder resist layer 22 melts, the resin component adheres to the heat dissipation conductor layer 20.

[0051] Although a chemical agent can be used to remove the resin component adhering to the pads 73, the solder resist layer 22 is relatively sensitive to chemical agents, and the chemical agent deteriorates the solder resist layer 22 in the areas other than the pads 73. Therefore, the filler and the like on the pads 73 cannot be removed satisfactorily using only the CO2 laser light 62. FIG. 6(a) shows a substrate in which holes corresponding to pads 73 have been formed in the solder resist layer 22 using a CO 2 laser beam 62. As shown in FIG. 6(b), the femtosecond laser device 63 irradiates the pad 73 with femtosecond laser light 62 (step S37).

[0052] The pulse width of the femtosecond laser light 62 is very short, and the heat dissipation conductor layer 20 is heated to a temperature exceeding the melting point before thermal diffusion occurs, causing evaporation, so that processing can be performed with little thermal influence.

[0053] The femtosecond laser light 62 removes residues on the pads 73 that could not be removed by the CO2 laser light 64, and also removes the surface (surface layer) of the heat dissipation conductor layer 20. Also, fine irregularities are formed on the surface of the heat dissipation conductor layer 20, or the surface is roughened (step 37). The processed or roughened state can be easily achieved by changing or setting the laser intensity of the femtosecond laser light 64 and the moving speed of the irradiated laser pulse.

[0054] The femtosecond laser device 63 generates femtosecond laser light 64, which generally has a pulse width of subpicoseconds to tens of femtoseconds. When the ultrashort pulse laser light 64 of subpicoseconds to tens of femtoseconds is irradiated onto a material, the pulse width is sufficiently short compared to the thermal diffusion time of the material, so that light energy can be effectively input to the irradiated area.

[0055] As a result, it is possible to localize the thermal effects on the periphery of the irradiation, enabling highly accurate micromachining. In addition, because the electric field strength of the laser light is extremely high, it is possible to induce nonlinear effects such as multiphoton absorption and multiphoton ionization in a spatially selective manner only in the area where the beam is focused.

[0056] Since the femtosecond green laser is a second harmonic wave, it is possible to extract a relatively high output, and the irradiated laser light is well absorbed by the heat dissipation conductor layer 20 as well.

[0057] The wavelength of light emitted by the femtosecond green laser is preferably 500 nm to 550 nm, and the pulse width is preferably 1 femtosecond to 1000 femtoseconds.

[0058] When a picosecond laser is used, the wavelength of light emitted by the picosecond laser is preferably 500 nm to 550 nm, and the pulse width is preferably 1 picosecond to 10 picoseconds.

[0059] Residues on the surface of the heat dissipation conductor layer 20 are removed. The surface of the heat dissipation conductor layer 20 is roughened and processed by a picosecond laser light having a pulse width in units of picoseconds or a femtosecond laser light having a pulse width in units of femtoseconds.

[0060] The surface processing of the heat dissipation conductor layer 20 described in Fig. 6(b) etc. may be repeated multiple times. The residue is removed by the irradiation of the laser light 64, and fine irregularities are formed, which improves the wettability of the solder 71. The laser light 64 is preferably in the range of 0.4 W to 0.6 W, and the appropriate frequency is 100 KHz to 500 kHz.

[0061] Through the above steps, the printed circuit board of the present invention shown in Fig. 7 is completed. Next, as shown in Fig. 8, electronic components 72 are mounted on the printed circuit board and soldered 71 (step 39). After that step, as shown in step 39, surface finishing such as cleaning is performed.

[0062] In the printed circuit board according to the embodiment of the present invention, heat generated from the component mounting conductor layer 14 on the circuit surface is conducted through the substrate 12 to the gaps formed between the side surfaces of the above-mentioned generally convex-shaped laminate 24 on the heat dissipation surface, and to the heat dissipation conductor layer 20.

[0063] Moreover, heat generated from electronic components 72 that generate a large amount of heat, such as LEDs, is dissipated via the heat dissipation conductor layer 20. The heat dissipation conductor layer 20 also serves as wiring for supplying the voltage and current of the electronic components 72. The heat that reaches the gap is directly released to the outside, whereas the heat that reaches the heat dissipation conductor layer 20 is released to the outside through the exposed side surface.

[0064] Therefore, in the printed circuit board according to the embodiment, heat can be released from both the gaps generated between the side surfaces of the approximately convex-shaped laminate and from the heat dissipation conductor layer 20, which further promotes the heat dissipation effect and improves the mechanical properties of the printed circuit board against warping and twisting due to the accompanying reduction in thermal expansion of the copper foil. [Industrial Applicability]

[0065] In the present invention, pads 73 are processed in the solder resist layer 22 by using a CO2 laser beam 62, and the resulting residues and the like are removed by irradiating with a femtosecond laser beam 64. Therefore, pads 73 with good solder wettability can be formed. The present invention can be applied to printed circuit boards and their manufacturing methods that promote the heat dissipation effect of the entire printed circuit board and improve mechanical properties such as resistance to warping and twisting. [Explanation of symbols]

[0066] 12 Base material 14 Conductive layer for component mounting 16 Conductor layer for wiring 18 Circuit surface resist layer 20 Heat dissipation conductive layer 24 Laminated layer having a roughly convex shape 30 Base Board 32 Metal layer (copper foil) 52 Etching resist layer 61 CO2 Laser Equipment 62 CO2 laser light 63 Femtosecond Laser Device 64 Femtosecond Laser Light 71 Solder 72 Electronic Components 73 Pad

Claims

1. A base substrate having a first surface and a second surface, the base substrate having a first metal layer formed on the first surface and a second metal layer formed on the second surface, forming a solder resist layer containing a filler on the first metal layer; a first step of forming an etching resist layer on the second metal layer; a second step of etching the first metal layer using the solder resist layer to form a heat dissipation conductor layer; a third step of irradiating the solder resist layer with a CO2 laser beam to form a first pad on the heat dissipation conductor layer; a fourth step of irradiating the first pad with femtosecond laser light to form irregularities or roughen the surface of the first pad; A method for manufacturing a printed circuit board, comprising a fifth step of arranging an electronic component having a first connection terminal, and soldering the first connection terminal and the first pad.

2. A base substrate having a first surface and a second surface, the base substrate having a first metal layer formed on the first surface and a second metal layer formed on the second surface, a solder resist ink containing a filler for improving heat dissipation is pattern-printed on the first metal layer, and the solder resist ink is cured to form a solder resist layer; a first step of forming an etching resist layer on the second metal layer; using the solder resist layer to etch the first metal layer to form a heat dissipation conductor layer; a second step of etching the second metal layer using the etching resist layer; a third step of irradiating the solder resist layer with a CO2 laser beam to form a first pad on the heat dissipation conductor layer; a fourth step of irradiating the first pad with femtosecond laser light to form irregularities or roughen the surface of the first pad; A method for manufacturing a printed circuit board, comprising a fifth step of arranging an electronic component having a first connection terminal, and soldering the first connection terminal and the first pad.

3. A base substrate having a first surface and a second surface, the base substrate having a first metal layer formed on the first surface and a second metal layer formed on the second surface, a solder resist ink containing a filler for improving heat dissipation is pattern-printed on the first metal layer, and the solder resist ink is cured to form a solder resist layer; a first step of forming an etching resist layer on the second metal layer; using a solder resist layer to etch the first metal layer to form a first heat dissipation conductor layer and a second heat dissipation conductor layer; a second step of etching the second metal layer using the etching resist layer to form a wiring conductor layer; a third step of irradiating the solder resist layer on the first heat dissipation conductor layer with a CO2 laser beam to form a first pad on the first heat dissipation conductor layer, and irradiating the solder resist layer on the second heat dissipation conductor layer with a CO2 laser beam to form a second pad on the second heat dissipation conductor layer; a fourth step of irradiating the first pad and the second pad with femtosecond laser light to form irregularities or roughen the surfaces of the first pad and the second pad; A method for manufacturing a printed circuit board, comprising a fifth step of arranging an electronic component having a first connection terminal and a second connection terminal, soldering the first connection terminal to the first pad, and soldering the second connection terminal to the second pad.

4. 4. The method for manufacturing a printed circuit board according to claim 1, 2 or 3, wherein the CO2 laser light is a pulsed laser light, and the frequency of the pulse is 1 KHz to 5 KHz.

5. 4. The method for manufacturing a printed circuit board according to claim 1, wherein the wavelength of the femtosecond laser light is 500 nm to 550 nm, and the pulse width of the femtosecond laser light is 1 femtosecond to 1000 femtoseconds.

6. 4. The method for manufacturing a printed circuit board according to claim 1, 2 or 3, wherein the first metal layer is made of copper foil and has a thickness of 18 to 70 μm.

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