Acidic electrolytic copper plating solution, method for forming a preform layer, method for manufacturing a bonding sheet, method for manufacturing a bonding substrate, and method for manufacturing a bonded body.

Abstract

To provide an acid copper electroplating solution capable of forming a porous preform layer in a simple process, a method for forming a preform layer using the same, and a method for manufacturing a junction sheet including the preform layer.SOLUTION: An acid copper electroplating solution includes soluble copper salt, a specific azole compound, which is a copper ion electrocrystallization inhibitor containing two or more nitrogen atoms, acid, and water. A copper concentration is higher than or equal to 0.1 mol / L, an azole compound concentration is higher than or equal to 10 mmol / L and less than or equal to 50 mmol / L, and a chloride ion concentration is less than or equal to 10 ppm. A porous preform layer in which an average porosity consisting of copper particles is 11% to 17% is formed on one or both surfaces of a copper sheet and a substrate as a copper plating film by arranging a copper sheet or a substrate on the cathode side in the acid copper electroplating solution and performing copper electroplating. A surface of a copper particle is covered with smaller copper nanoparticles than an average particle size of the copper article.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] This invention relates to an acidic electrolytic copper plating solution for forming a porous preform layer for joining two components in the assembly and mounting of electronic components. It also relates to a method for forming a preform layer using this acidic electrolytic copper plating solution. Furthermore, it relates to a method for manufacturing a bonding sheet having a preform layer on a copper sheet, a method for manufacturing a bonding substrate having a preform layer on a substrate, and a method for manufacturing a bonded body using this bonding sheet or bonding substrate. [Background technology]

[0002] Conventionally, a method for producing this type of porous material has been disclosed in which a film is electroplated (hereinafter simply referred to as electrodeposition) using a composite plating method with polymer microparticles as a dispersant, and a porous film is produced by the decomposition and desorption of the polymer microparticles (see Non-Patent Literature 1). In this method for producing porous materials, nickel plating by a Watt bath is used as the matrix for composite plating, and highly crosslinked acrylic polymer microparticles are added to the bath as a dispersant. In this method, a soft iron plate coated on one side is used as the base material, and after pretreatment by alkaline degreasing, nickel plating is performed in a plating bath containing nickel sulfate, nickel chloride, and boric acid. By heat treatment at 500°C for 1 hour in air, the pore opening treatment of the plating film after co-deposition is performed to obtain a porous material. [Prior art documents] [Non-patent literature]

[0003] [Non-Patent Document 1] Tomohiko Nakamura, Minoru Matsuda, Development of Porous Materials Using Plating Technology, Kyoto Prefectural Small and Medium Enterprise Technology Center Technical Report, No. 61, pp. 36-38. [Overview of the project] [Problems that the invention aims to solve]

[0004] In the conventional porous film manufacturing method described above, the process of removing polymer fine particles other than the target metal is complex, and even if these are removed, there is a concern that some may remain.

[0005] The first object of the present invention is to provide an acidic electrolytic copper plating solution capable of forming a porous preform layer in a simple process. The second object of the present invention is to provide a method for forming a preform layer using this acidic electrolytic copper plating solution. The third object of the present invention is to provide a method for manufacturing a bonding sheet having a preform layer on a copper sheet. The fourth object of the present invention is to provide a method for manufacturing a bonding substrate having a preform layer on a substrate. Furthermore, the fifth object of the present invention is to provide a method for manufacturing a bonded body using a bonding sheet or a bonding substrate.

[0006] The first aspect of the present invention is an acidic electrolytic copper plating solution comprising a soluble copper salt, an azole compound having two to three nitrogen atoms in a five-membered ring, which is a copper ion electrodeposition inhibitor represented by the following formulas (1) to (4), an acid, and water, wherein the copper concentration is 0.1 mol / L or higher, the azole compound concentration is 10 mmol / L or higher and 50 mmol / L or lower, and the chloride ion concentration is 10 ppm or lower. The pH is between 0 and 5. This is an acidic electrolytic copper plating solution characterized by the following features.

[0007] [ka]

[0008] In formulas (1) to (4) above, R1 to R4 may be the same or different from each other, and are any of the following: an alkyl group having 10 or less carbon atoms, an alkenyl group having 10 or less carbon atoms, an alkynyl group having 10 or less carbon atoms, an aryl group having 10 or less carbon atoms, an aralkyl group having 10 or less carbon atoms, or an alkoxy group having 10 or less carbon atoms; or a group in which the hydrogen atoms of these are substituted with any of the following: a halogen atom, a hydroxyl group, a carboxyl group, an amino group, an alkyl-substituted amino group having 5 or less carbon atoms, a hydroxyalkyl-substituted amino group having 5 or less carbon atoms in an alkyl chain, a mercapto group, a hydroxyl group, a carboxyl group, a halogen atom, or a hydrogen atom.

[0009] A second aspect of the present invention is that by placing a copper sheet or substrate on the cathode side of the acidic electrolytic copper plating solution of the first aspect and performing acidic electrolytic copper plating (hereinafter sometimes simply referred to as "electrolytic copper plating"), a copper plating film consisting of copper particles is formed on one or both sides of the copper sheet or substrate. The preform layer defined below Average porosity is 11% More than 78% or less A method for forming a porous preform layer. That is the case. The average porosity of the preform layer That is, The arithmetic mean of the degree of porosity (P) calculated by the following formula (A), based on the total area (S1) of the preform layer and the area of ​​the void portion (S2) within the preform layer, which are obtained by image analysis of the cross-section of the preform layer using a scanning electron microscope. ru. P(%) = (S2 / S1) × 100 (A) A third aspect of the present invention is a method for forming the preform layer according to the second aspect, characterized in that the surface of the copper particles is coated with copper nanoparticles smaller than the average particle size of the copper particles, and the average particle size calculated from the BET value of the copper nanoparticles is 9.59 nm or more and 850 nm or less.

[0010] This invention 4 From this perspective, the copper sheet has a second side on one or both sides. or third This is a method for manufacturing a bonding sheet in which a porous preform layer is formed by the method described above.

[0011] This invention 5 The perspective is, 4A method of manufacturing a bonded body by laminating a base material and an electronic component through a bonding sheet manufactured by the method from the perspective of

[0012] The first 6 From the perspective of, a method for manufacturing a bonding substrate in which a porous preform layer is formed on one side of the substrate by the method of the or third perspective is provided.

[0013] The The seventh point is, A method of manufacturing a bonded body by laminating a bonding substrate manufactured by the method of the sixth perspective of the present invention and an electronic component through a porous preform layer, and pressing and heating the bonding substrate and the electronic component in the lamination direction.

Advantages of the Invention

[0014] In the acidic electrolytic copper plating solution of the first perspective of the present invention, since it contains a soluble copper salt, a specific azole compound which is a copper ion electrodeposition inhibitor containing two or more nitrogen atoms, an acid, and water, when electrolytic plating is performed, the azole compound which is a copper ion electrodeposition inhibitor is also adsorbed on the cathode surface together with copper ions. As a result, the electrodeposition of copper ions is strongly suppressed, the nucleation of copper is prioritized, and a porous preform layer composed of copper particles is formed as a copper plating film on the cathode surface.

[0015] In the method for forming a preform layer of the second perspective of the present invention, since a copper sheet or a substrate is arranged on the cathode side in the acidic electrolytic copper plating solution of the first perspective to perform electrolytic copper plating, different from the conventional method for manufacturing a porous film, a porous preform layer with an average porosity of 11% to 17% composed of copper particles whose surface is covered with copper nanoparticles can be formed on one side or both sides of the copper sheet or the substrate as a copper plating film in a simple process.

[0016] The 4 In the method for manufacturing a bonding sheet from the perspective of, a bonding sheet having a porous preform layer on one side or both sides of a copper sheet and having high strength of the sheet itself can be manufactured in a simple process.

[0017] This invention 5 In a method for manufacturing a joint from the perspective of, 4 By laminating a substrate and electronic components via a bonding sheet manufactured using the method described above, and then pressurizing and heating the substrate and electronic components in the lamination direction, the preform layer becomes a bonding layer, making it possible to manufacture a bonded body with high bonding strength.

[0018] This invention 6 In the method for manufacturing a bonding substrate from this perspective, a second or third By forming a porous preform layer using this method, a bonding substrate with high strength when bonded can be manufactured.

[0019] This invention 7 In a method for manufacturing a joint from the perspective of, 6 By laminating a bonding substrate and electronic components manufactured using the method described above, and then pressurizing and heating the bonding substrate and electronic components in the lamination direction to produce a bonded body, the preform layer becomes the bonding layer, and a bonded body in which the bonding substrate and electronic components are firmly bonded can be obtained. [Brief explanation of the drawing]

[0020] [Figure 1] This figure shows the process of forming porous preform layers on both sides of a copper sheet using the electrolytic copper plating method of this embodiment. [Figure 2] This figure schematically shows a bonding sheet in which porous preform layers are formed on both sides of a copper sheet according to this embodiment. [Figure 3] Figure 3(a) shows the process of forming a porous preform layer on one side of a substrate whose surface is made of copper or nickel by the electrolytic copper plating method of this embodiment. Figure 3(b) is a schematic diagram of a bonding substrate on which a porous preform layer has been formed on one side. [Figure 4]This figure shows a first method for manufacturing a bonded body using the bonding sheet of this embodiment. Figure 4(a) shows the bonding sheet being placed on a substrate, Figure 4(b) shows the electronic components being placed on the bonding sheet, followed by pressurization and heating, and Figure 4(c) shows the bonded body being manufactured after pressurization and heating. [Figure 5] This figure shows a second method for manufacturing a bonded body using the bonding substrate of this embodiment. Figures 5(a) to (d) show the manufacturing of a bonding substrate by forming a preform layer on a part of the substrate by electrolytic copper plating, and Figures 5(e) to (h) show the manufacturing of a bonded body by placing electronic components on the preform layer of the bonding substrate, and then pressurizing and heating it. [Figure 6] These are scanning electron microscope images of the preform layer of Example 1 of the present invention. Figure 6(a) is a photograph of the preform layer taken at a magnification of 50,000x, and Figure 6(b) is a photograph of the preform layer taken at a magnification of 100,000x. [Modes for carrying out the invention]

[0021] Next, embodiments for carrying out the present invention will be described based on the drawings.

[0022] [Acidic electrolytic copper plating solution] The acidic electrolytic copper plating solution of this embodiment contains a soluble copper salt, an azole compound which is a copper ion deposition inhibitor having 2 to 3 nitrogen atoms in the five-membered ring shown in formulas (1) to (4) above, an acid, and water. Any bath solution can be used as long as it contains these components. Brighteners, surfactants, antioxidants, etc. can also be added as needed. Specific examples of soluble copper salts include copper sulfate, copper oxide, copper carbonate; copper alkanesulfonates such as copper methanesulfonate and copper propanoate; copper alkanolsulfonates such as copper isethionate and copper propanolsulfonate; and copper organic acids such as copper acetate, copper citrate, and copper tartrate. These can be used individually or in combination of two or more.

[0023] Furthermore, examples of acids include organic acids and inorganic acids. These include sulfuric acid; alkanesulfonic acids such as methanesulfonic acid and propanesulfonic acid; alkanolsulfonic acids such as isethionic acid and propanolsulfonic acid; and organic acids such as citric acid, tartaric acid, and formic acid. These can be used individually or in mixtures of two or more. Examples of water include deionized water and distilled water.

[0024] Next, we will describe azole compounds, which are copper ion electrodeposition inhibitors having two to three nitrogen atoms in a five-membered ring. Examples of azole compounds shown in formulas (1) to (4) above include imidazole, 2-aminoimidazole, pyrazole, 3-aminoimidazole, 1,2,3-triazole, 1,2,4-triazole, 3-amino-1,2,4-triazole, 3,5-diamino-1,2,4-triazole, and 3-amino-5-methylthio-1H-1,2,4-triazole.

[0025] The imidazole mentioned above is a type of azole compound shown in formula (1) above, and is represented by formula (5) below. 2-aminoimidazole is also a type of azole compound shown in formula (1) above, and is represented by formula (6) below. Pyrazole is also a type of azole compound shown in formula (2) above, and is represented by formula (7) below. 3-aminoimidazole is also a type of azole compound shown in formula (2) above, and is represented by formula (8) below. 1,2,3-triazole is also a type of azole compound shown in formula (3) above, and is represented by formula (9) below.

[0026] [ka]

[0027] Furthermore, 1,2,4-triazole is a type of azole compound shown in formula (4) above, and is represented by the following formula (10). Also, 3-amino-1,2,4-triazole is a type of azole compound shown in formula (4) above, and is represented by the following formula (11). Also, 3,5-diamino-1,2,4-triazole is a type of azole compound shown in formula (4) above, and is represented by the following formula (12). Furthermore, 3-amino-5-methylthio-1H-1,2,4-triazole is a type of azole compound shown in formula (4) above, and is represented by the following formula (13).

[0028] [ka]

[0029] [Method for manufacturing acidic electrolytic copper plating solution] The acidic electrolytic copper plating solution of this embodiment can be prepared by mixing the above-mentioned soluble copper salt, the above-mentioned copper ion electrodeposition inhibitor, an azole compound having 2 to 3 nitrogen atoms in a five-membered ring, an acid, and water.

[0030] In the prepared acidic electrolytic copper plating solution, the concentration of the soluble copper salt is 0.1 mol / L or higher, preferably 0.1 mol / L or higher and 1.0 mol / L or lower. If the concentration of the soluble copper salt is less than 0.1 mol / L, a preform layer as a copper plating film cannot be formed. The concentration of the azole compound, which is a copper ion deposition inhibitor, is 10 mmol / L or higher and 50 mmol / L or lower, preferably 10 mmol / L or higher and 30 mmol / L or lower. If the concentration of the azole compound is less than 10 mmol / L, the effect of suppressing copper ion deposition is poor, and the preform layer as a copper plating film does not become porous. If it exceeds 50 mmol / L, the deposition of copper ions is suppressed too much, making the copper plating film brittle and significantly degrading its strength. Alternatively, the azole compound may not dissolve in the solution and precipitate. There are no particular restrictions on the acid concentration, but pH 0 to 5 is preferred, and pH 1 to 3 is more preferred. Furthermore, the chloride ion concentration is 10 ppm or lower, preferably 5 ppm or lower. When the concentration exceeds 10 ppm, chloride ions adsorb onto the copper surface, inhibiting the formation of the preform layer as a copper plating film.

[0031] [Method for manufacturing porous preform layers and bonding sheets] A method for producing a bonding sheet having a preform layer on a copper sheet is described below, using the above-mentioned acidic electrolytic copper plating solution to form a preform layer on one or both sides of a copper sheet.

[0032] As shown in Figure 1, the above-mentioned acidic electrolytic copper plating solution 3 is placed in the plating tank 2 of the electrolytic copper plating apparatus 1, and a copper sheet 4, which is the object to be plated, and two copper materials 5,5 made of electrolytic copper or oxygen-free copper are placed in this solution so as to face both sides of the copper sheet 4. As shown in the figure, the copper sheet 4 is connected to the cathode 6 as the cathode, and the two copper materials 5,5 are connected to the anode 7 as soluble anodes, and by applying a voltage to the copper sheet 4 and the copper materials 5,5, a preform layer 8 as a copper plating film is formed on both sides of the copper sheet 4. In this embodiment, the copper sheet 4 is a copper foil, and the thickness of the copper sheet is exaggerated in Figure 1. Pure copper or a copper alloy can be used as the copper foil constituting the copper sheet 11. For example, oxygen-free copper, tough pitch copper, or phosphorus-deoxidized copper can be used. The copper foil can be rolled copper foil obtained by rolling such copper material, or electrolytic copper foil produced by the electrolytic copper plating method can be used. Here, copper material 5 was used as the soluble anode, but it is also possible to use an insoluble anode such as Pt / Ti instead of copper material 5. Furthermore, although not shown in the diagram, by placing the copper material 5 opposite only one side of the copper sheet 4, a bonding sheet having a preform layer on one side of the copper sheet 4 can be manufactured.

[0033] [Method for manufacturing porous preform layers and bonding substrates] Another electrolytic copper plating method is shown in Figure 3(a). In Figure 3(a), the same elements as those shown in Figure 1 are denoted by the same reference numerals. As shown in Figure 3(a), a substrate 4a whose substrate surface is made of copper or nickel is placed in the acidic electrolytic copper plating solution 3 of the electrolytic copper plating apparatus 1, and a copper material 5 is placed opposite one side of the substrate 4a, and electrolytic copper plating is performed in the same manner as the electrolytic copper plating shown in Figure 1. A resist film 4b is formed in advance on the surface of the substrate 4a so as to have openings at predetermined intervals. As a result, a porous preform layer 8 made of copper particles 12 is formed as a copper plating film within the openings of the resist film 4b formed on one side of the substrate 4a.

[0034] The conditions for electrolytic copper plating in the acidic electrolytic copper plating solution 3 shown in Figure 1 or Figure 3 are, for example, using a DC power supply, with a current density of 0.1 A / dm² in the copper sheet 4 or substrate 4a that is to be plated. 2 ~5A / dm 2 The degree, preferably 0.4 A / dm 2 ~1.0A / dm 2 Then, the liquid temperature is raised for about 30 to 150 minutes, preferably 60 to 120 minutes, and air and jet stirring or oscillating stirring are performed. When electrolytic copper plating is performed under the above conditions, azole compounds, which are copper ion deposition inhibitors, are adsorbed along with copper ions onto the cathode surface, which is the surface of the copper sheet 4 or substrate 4a. The presence of the azole compound strongly suppresses the deposition of copper ions, prioritizing copper nucleation, and a porous preform layer 8 consisting of copper particles 12 is formed on the cathode surface as a copper plating film.

[0035] After electrolytic copper plating, the copper sheet 4 with the preform layer shown in Figure 1 is removed from the acidic electrolytic copper plating solution 3. The substrate 4a with the preform layer shown in Figure 3 is also removed from the acidic electrolytic copper plating solution 3, and the resist layer 4b is removed. Subsequently, the copper sheet 4 or substrate 4a is washed with a cleaning solvent such as ethanol, water, or acetone, and then dried in the air using dry air. This yields a bonding sheet 10 having a porous preform layer 8 on both sides of the copper sheet 4, as shown in Figure 2. Alternatively, a bonding substrate 20 having a porous preform layer 8 on one side of the substrate 4a is obtained, as shown in Figure 3(b). To prevent surface oxidation, it is preferable to immerse the obtained bonding sheet 10 or bonding substrate 20 in a rust inhibitor mainly composed of benzotriazole and a surfactant for a predetermined time.

[0036] The thickness of the porous preform layer 8 of the copper sheet 4 or substrate 4a is preferably 15 μm to 50 μm. If the thickness of the preform layer is less than 15 μm, the strength of the preform layer itself decreases, making it difficult to handle. If the thickness of the preform layer exceeds 50 μm, the preform layer may not be able to follow the irregularities of each surface of the substrate or electronic component described later during bonding, which may reduce the bonding strength of the bonded body.

[0037] [Bonding sheet] The total thickness of the bonding sheet 10 obtained in this way is at least 25 μm, i.e., 25 μm or more. A preferred total thickness is 25 μm to 140 μm. If the total thickness is less than the lower limit of 25 μm, the strength of the bonding sheet itself may decrease. If the total thickness exceeds 140 μm, and the substrate is a circuit board to which electronic components are bonded, there is a risk that the board may not be able to absorb the warping. The total thickness of the bonding sheet is determined by completely encasing the bonding sheet in epoxy resin, cutting it perpendicular to the surface direction of the bonding sheet, and polishing the cut surface with an argon ion beam. Then, the polished surface is observed with an SEM (scanning electron microscope), and the thickness of the bonding sheet is measured at 100 or more random locations, and the average value is taken as the thickness of the bonding sheet.

[0038] The bonding sheet 10 shown in Figure 2, in which a porous preform layer 8 is formed on both sides of a copper sheet 4, will be described in detail. The porous preform layer 8 is formed in the form of an aggregate of copper particles, in which copper particles 12 are stacked on both sides of the copper sheet 4. The average porosity of this preform layer consisting of copper particles 12 is between 11% and 78%. If the average porosity is less than 11%, there are fewer copper particles that contribute to the sintering of the porous preform layer, and the sinterability of the copper particles decreases. If the average porosity exceeds 78%, the void ratio within the porous preform layer increases, making the preform layer 13 brittle and reducing the sinterability of the copper particles.

[0039] As shown in the enlarged view of Figure 2, the copper particles 12 are coated on their surface with copper nanoparticles 12a having an average particle size smaller than the average particle size of the copper particles 12. Copper plating is performed using the acidic electrolytic copper plating solution characteristic of this embodiment, and the azole compound is adsorbed onto the copper surface, suppressing copper electrodeposition and prioritizing nucleation, thereby forming copper nanoparticles 12a on the surface of the copper particles 12. Due to this characteristic structure, when the porous preform layer 8 is pressurized, the copper particles easily sinter with each other to form a robust bonding layer. Here, because the average particle size of the copper nanoparticles is a composite of fine copper particles and even finer nanoparticles, it is difficult to calculate the average particle size from a microscope image, so the average particle size is calculated from BET measurement. Thus, the average particle size of the copper nanoparticles calculated from BET measurement is between 9.59 nm and 850 nm. If the average particle size of the copper nanoparticles is outside this range, the copper particles will not sinter easily. A preferred range is between 50 nm and 300 nm.

[0040] The average porosity of the preform layer 8 described above is calculated by image analysis of the cross-section of the preform layer 8 using a scanning electron microscope. The arithmetic mean of the porosity (P) obtained by the following formula (A) is taken as the average porosity. Specifically, the measurement is taken by taking three images in different fields of view, and the average value of the calculated porosity is taken as the average porosity. P(%) = (S2 / S1) × 100 (A) However, in equation (A), P is the porosity of the preform layer, S1 is the total area of ​​the preform layer, and S2 is the area of ​​the void portion in the preform layer.

[0041] Furthermore, the average particle size of the copper nanoparticles mentioned above is measured using the BET method on the porous preform layer. The BET method measurement is performed using Macsorb's HM-model-1201. A copper sheet with a preform layer is cut into 2 mm squares, packed into a measurement cell, and measured using the single-point BET method. The mass of the copper sheet is subtracted from the measured value and converted to the mass of the preform layer itself. From the calculated BET measurement value, the particle size of the copper nanoparticles is calculated based on the following equation (B). Note that the coefficient 335.95 in equation (B) below is a value calculated from the theoretical values ​​of copper density, copper nanoparticle surface area, and copper nanoparticle volume. The average particle size of the copper nanoparticles (d) is the average value obtained by measuring three times using the BET method. d(nm) = 335.95 / (BET measurement value (m 2 / g)) (B)

[0042] [First method for manufacturing a bonded body using a bonding sheet] A first method for manufacturing a joined body using the above-mentioned joining sheet 10 will be described. As shown in Figure 4(a), first, a substrate 16 is prepared, such as an oxygen-free copper plate, various heat dissipation substrates, an FR4 (Flame Retardant Type 4) substrate, or Kovar. Electronic components 17 are prepared, such as silicon chip elements or LED chip elements. Next, the bonding sheet 10 is placed in a predetermined position on the substrate 16, and as shown in Figure 4(b), the electronic components 17 are placed on the bonding sheet 10 on the substrate 16. In this state, the bonding sheet 10 is heated in a heating furnace under a nitrogen atmosphere at a temperature of 250°C to 350°C for 1 to 30 minutes. In some cases, the substrate 16 and the electronic components 17 may be bonded while applying a pressure of 1 MPa to 20 MPa. As a result, as shown in Figure 4(c), the bonding sheet 10 becomes a bonding layer 15, and this bonding layer 15 bonds the electronic components 17 to the substrate 16, resulting in a bonded body 18.

[0043] [Second method for manufacturing a bonded body using a bonding substrate] A second method for manufacturing a bonded body using a bonding substrate will be described. As shown in Figure 5, in this method, a bonding body 44 is formed using a bonding substrate 40 on which a porous preform layer 8 is formed on the surface of a substrate 46.

[0044] The porous preform layer 8 shown in Figure 5 is the same as the porous preform layer 8 shown in Figure 2. The substrate 46 has a surface made of copper or nickel. For example, this substrate 46 is an oxygen-free copper plate, or a Si substrate with a copper metallized surface, or an oxygen-free copper plate with a nickel plated surface. The electronic component 47 shown in Figure 5 is the same as the electronic component 17 shown in Figure 4.

[0045] First, as shown in Figure 5(a), a substrate 46 made of copper or nickel is prepared, and as shown in Figure 5(b), the surface of the substrate 46 is masked and patterned with a resist film 41 so that it has openings 46a at predetermined intervals. In this state, it is placed in the acidic electrolytic copper plating solution described above, and as shown in Figure 5(c), a porous preform layer 8 is formed on the openings 46a. Then, as shown in Figure 5(d), the resist film 41 is removed to create a bonding substrate 40 with a porous preform layer 8 formed on the substrate 46. This electrolytic copper plating can be performed by the method described above. In the above description, the preform layer 8 was formed only on the openings 46a, but the preform layer 8 may be formed on the entire surface of the substrate 46 without providing the resist film 41.

[0046] As shown in Figure 5(e), the electronic component 47 is bonded to the porous preform layer 8 of the bonding substrate 40. Specifically, the bonding substrate 40, on which the porous preform layer 8 is formed, is placed on a pressure plate 42. As shown in Figure 5(f), the electronic component 47 is placed on the preform layer 8 to obtain a laminate. Then, as shown in Figure 5(g), the laminate consisting of the bonding substrate 40 and the electronic component 47 is pressed in the stacking direction by the pressure plate 42 and the pressure plate 43. These pressing conditions are the same as those for the substrate 16 and the electronic component 17 shown in Figure 4(a). As a result, as shown in Figure 5(h), the preform layer 8 becomes the bonding layer 45, bonding the bonding substrate 40 and the electronic component 47, and a bonded body 44 is obtained.

[0047] Although not shown in the diagram, the substrate may be an oxygen-free copper plate without a preform layer on its surface, or a substrate with a copper metallized bonding surface, while the electronic component may have a preform layer formed on its bonding surface. Alternatively, although not shown in the diagram, a preform layer may be formed on both the substrate and the bonding surface of the electronic component. Forming preform layers on both surfaces is preferable as it further enhances the bonding strength between the substrate and the electronic component. [Examples]

[0048] Next, embodiments of the present invention will be described in detail along with comparative examples. In Examples 1 to 20 and Comparative Examples 1 to 10 shown below, copper plating was performed on Si wafers patterned by the method shown in Figure 5.

[0049] First, Table 1 below shows the types, structural formulas, and compound names of the copper ion electrodeposition inhibitors used in Examples 1-20 and Comparative Examples 1-10.

[0050] [Table 1]

[0051] In Table 1 above, the copper ion electrodeposition inhibitors, tetrazole No. 10 and 5-amino-1H-tetrazole No. 11, are represented by formulas (14) and (15), respectively. These azole compounds do not belong to formulas (1) to (4) described above.

[0052] [ka]

[0053] <Example 1> First, a Si wafer (thickness: 1.2 mm) with a copper layer of approximately 500 nm thickness formed on its surface by sputtering was used as the object to be plated. The surface of this Si wafer was patterned with photoresist so that there were 6002 perfectly circular openings with a diameter of 75 μm per die (15 mm square). As a treatment before copper plating this Si wafer, it was hydrophilized using a plasma cleaner. Next, the Si wafer was pre-wetted with pure water and then immersed in a 10% by mass sulfuric acid aqueous solution for acid cleaning. After acid cleaning, the Si wafer was rinsed with water, and copper plating was performed on one side of the patterned surface of the Si wafer using the plating apparatus 1 shown in Figure 3, which contained the copper plating solution shown below.

[0054] A copper plating bath was prepared with the following liquid composition. The plating conditions are also shown. Table 2 below shows the characteristic items of the plating bath composition and plating conditions for Example 1. In Example 1, 3,5-diamino-1,2,4-triazole of formula (12) shown as No. 8 in Table 1 was used as the copper ion electrodeposition inhibitor.

[0055] [Plating bath composition] Copper sulfate pentahydrate (Cu 2+ (As): 0.1 mol / L Copper ion electrodeposition inhibitor (3,5-diamino-1,2,4-triazole): 10 mmol / L Chloride ions: 0 ppm Deionized water: Remaining portion [Plating conditions] Bath temperature: 26℃ Bath pH: 2.5 Cathode current density: 0.4 A / dm 2

[0056] By immersing a Si wafer in the above copper plating solution and performing plating under the above plating conditions, a porous preform layer consisting of copper particles was formed on the Si wafer. Figures 6(a) and (b) show scanning electron microscope images of the surface of the preform layer in Example 1.

[0057] [Table 2]

[0058] <Examples 2 to 20 and Comparative Examples 4 to 10> In Examples 2 to 20 and Comparative Examples 4 to 10, the concentration of copper sulfate pentahydrate was made the same as in Example 1 or changed, the type of copper ion electrodeposition inhibitor was made the same as in Example 1 or changed, the concentration of the copper ion electrodeposition inhibitor was made the same as in Example 1 or changed, and the chloride ion concentration was made the same as in Example 1 or changed. Also, the cathode current density during plating was made the same as in Example 1 or changed. Otherwise, copper plating was performed in the same manner as in Example 1. Among the compositions of the plating baths and plating conditions of Examples 2 to 20 and Comparative Examples 4 to 10, the characteristic items are shown in Table 2 above and Table 3 below, respectively. By performing plating in the same manner as in Example 1, in Examples 2 to 20 and Comparative Examples 4 and 5, a porous preform layer composed of copper particles was formed as a copper plating film on the Si wafer. However, in Comparative Examples 6 to 10, since the electrodeposition of copper ions was poor, the copper plating film was not uniformly formed on the Si wafer.

[0059]

Table 3

[0060] <Comparative Example 1> In Comparative Example 1, the concentration of copper sulfate pentahydrate was 1.0 mol / L, and the cathode current density during plating was 3.0 A / dm 2 As such, copper plating was performed on the Si wafer in the same manner as in Example 1. In Comparative Example 1, no copper ion electrodeposition inhibitor was used. The chloride ion concentration in the copper plating solution was 80 ppm.

[0061] <Comparative Example 2> In Comparative Example 2, the concentration of copper sulfate pentahydrate was 1.0 mol / L, and the cathode current density during plating was 3.0 A / dm 2Copper plating was performed on a Si wafer in the same manner as in Example 1. In Comparative Example 1, no copper ion deposition inhibitor was used. The chloride ion concentration in the copper plating solution was 5 ppm.

[0062] <Comparative Example 3> In Comparative Example 3, the concentration of copper sulfate pentahydrate was 1.0 mol / L, and the cathode current density during plating was 3.0 A / dm². 2 Copper plating was performed on a Si wafer in the same manner as in Example 1. In Comparative Example 3, in order to compare it with organic compounds other than azole compounds as a copper ion deposition inhibitor, a general additive containing 50 ppm of 3,3-dithiobis(1-propanesulfonic acid) disodium and 300 ppm of polyethylene glycol (Mw: 3400) was used. The chloride ion concentration in the copper plating solution was 80 ppm.

[0063] <Comparative Evaluation> <Measurement of chloride ion concentration> The chloride ion concentration of the copper plating solution after bath preparation was measured by ion chromatography (Thermo SCIENTIFIC, instrument name: Dionex ICS-2100, separation column: Dionex IonPac™ AS12A (4 × 200 mm)).

[0064] <Average porosity of the porous preform layer and average particle size of copper nanoparticles> The average porosity of the porous preform layer of the 25 types of bonding substrates obtained in Examples 1-20 and Comparative Examples 1-5, and the average particle size of the copper nanoparticles coating the copper particles constituting this preform layer, were determined using the method described above. These results are shown in Tables 2 and 3 above.

[0065] <Manufacturing of jointed parts> As shown in Figure 5(f), chips 47 were placed on the preform layers 8 of 25 types of bonding substrates 40 obtained in Examples 1 to 20 and Comparative Examples 1 to 5, and a bonded body 44 was obtained by pressurizing and heating as shown in Figure 5(g). The chips 47 consist of a 2.5 mm square Si wafer (thickness: 1.2 mm) with copper metallization applied to the outermost surface. This bonding was performed using a pressure-heat bonding device (Alpha Design; HTB-MM) under a nitrogen atmosphere, at a temperature of 300°C and a pressure of 30 MPa for 30 minutes. The shear strength of 22 types of bonded structures was measured as follows.

[0066] <Method for measuring the shear strength of a joint> The shear strength of the bonded structure was measured using a shear strength evaluation tester (Bond Tester; Dage Series 4000, manufactured by Nordson Advanced Technology Co., Ltd.). Specifically, the shear strength was measured by fixing the Si wafer, which is the substrate of the bonded structure, horizontally, and pressing the chip horizontally from the side with a shear tool at a position 50 μm above the surface (top surface) of the bonding layer, and measuring the strength at which the chip fractured. The movement speed of the shear tool was set to 0.1 mm / second. Three strength tests were performed for each condition, and the arithmetic mean of these tests was used as the measured bond strength. The shear strengths of 22 types of bonded structures are shown in Table 2 above. A bond strength of 15 MPa or higher was considered "good," 1.7 MPa or higher but less than 15 MPa was considered "slightly poor," and less than 1.7 MPa was considered "poor." In the bond strength in Table 2, "-" means that the chip 47 and the bonding substrate 40 were not bonded when an attempt was made to bond them, or that the chip 47 peeled off before the bond strength could be measured. These results are shown in Table 2 above.

[0067] As is clear from Table 3, Comparative Examples 1 and 2 did not contain a copper ion deposition inhibitor that has the function of forming a porous copper plating film. In Comparative Example 3, the added copper ion deposition inhibitor did not have the function of forming a porous copper plating film. Therefore, although a copper plating film was formed in Comparative Examples 1 to 3, the average porosity was "0%" in each case, and the copper plating film was not porous. As a result, in Comparative Examples 1 and 2, the chip and the bonding substrate were not bonded, and the judgment was "poor" in both cases. In Comparative Example 3, the bonding strength was low at "12.4 MPa", and the judgment was "somewhat poor".

[0068] In Comparative Example 4, the copper ion concentration was too low at "0.01 mol / L," resulting in insufficient electrodeposition. The average porosity was low at "8%," and the average particle size of the copper nanoparticles was 42 nm. As a result, the copper plating film was a preform layer with a low degree of porosity. Consequently, the bonding strength was low at "9.2 MPa," and the evaluation was "somewhat poor."

[0069] In Comparative Example 5, the concentration of 3,5-diamino-1,2,4-triazole, a copper ion deposition inhibitor, was too low at "5 mmol / L". As a result, copper ion deposition was not sufficiently suppressed, the average porosity was low at "5%", and the average particle size of copper nanoparticles was 77 nm. This resulted in a preform layer with a low degree of porosity as a copper plating film. Consequently, the bonding strength was low at "6.3 MPa", and the evaluation was "somewhat poor".

[0070] In Comparative Example 6, the concentration of 3,5-diamino-1,2,4-triazole, a copper ion deposition inhibitor, was too high at "75 mmol / L," resulting in almost no copper ion deposition and no copper plating film being formed. Therefore, the bonding strength was not measured. The result was "poor."

[0071] In Comparative Example 7, the chloride ion concentration was too high at "25 ppm". As a result, chloride ions adsorbed onto the copper surface, inhibiting the adsorption of the azole compound, which is necessary for forming a porous structure, and thus a porous copper plating film was not formed. Therefore, the bonding strength was not measured. The result was "poor".

[0072] In Comparative Example 8, the chloride ion concentration was too high at "50 ppm". As a result, chloride ions adsorbed onto the copper surface, inhibiting the formation of the preform layer as a copper plating film. Furthermore, the concentration of 3,5-diamino-1,2,4-triazole, a copper ion electrodeposition inhibitor, was too low at "0.15 mmol / L". This prevented sufficient surface adsorption to form a porous copper plating film, and therefore, a porous copper plating film was not formed. For this reason, the bonding strength was not measured. The judgment was "poor".

[0073] In Comparative Examples 9 and 10, tetrazoles (No. 10, formula (14)) and 5-amino-1H-tetrazoles (No. 11, formula (15)), which do not belong to formulas (1) to (4), were used as copper ion deposition inhibitors. As a result, the adsorption of the copper ion deposition inhibitors to the copper surface was too strong, and copper ion deposition hardly occurred, so no copper plating film was formed. Therefore, bonding strength was not measured. The judgment was "poor".

[0074] In contrast to these, as is clear from Table 2, in Examples 1 to 20, the average porosity of the preform layer and the average particle size calculated from the BET value were appropriately controlled. The average porosity of the preform layer formed on the Si wafer was within the aforementioned range of 11% to 78%, and the average particle size of the copper nanoparticles calculated from the BET value was also within the aforementioned range of 9.59 nm to 850 nm. A porous preform layer was formed consisting of copper particles. When the bonding substrate and chip of Examples 1 to 20 were bonded, the bonding substrate and chip were firmly bonded, and all bonding evaluations were "good". [Industrial applicability]

[0075] The acidic electrolytic copper plating solution of the present invention can be used to form a porous preform layer for joining two components in the assembly and mounting of electronic components. [Explanation of Symbols]

[0076] 8 Preform Layers 10 Bonding sheets 11 Copper Sheets 12 copper particles 12a Copper nanoparticles 15, 45 bonding layer 16 Base material 17, 47 Electronic components 18, 44 zygote 20, 40 Bonding substrate 46 Substrates (Si wafers)

Claims

1. An acidic electrolytic copper plating solution comprising a soluble copper salt, an azole compound having two to three nitrogen atoms in a five-membered ring which is a copper ion electrodeposition inhibitor represented by the following formulas (1) to (4), an acid, and water, An acidic electrolytic copper plating solution characterized by having a copper concentration of 0.1 mol / L or more, an azole compound concentration of 10 mmol / L or more and 50 mmol / L or less, a chloride ion concentration of 10 ppm or less, and a pH of 0 to 5. 【Chemistry 1】 In formulas (1) to (4) above, R1 to R4 may be the same or different from each other, and are any of the following: an alkyl group having 10 or less carbon atoms, an alkenyl group having 10 or less carbon atoms, an alkynyl group having 10 or less carbon atoms, an aryl group having 10 or less carbon atoms, an aralkyl group having 10 or less carbon atoms, or an alkoxy group having 10 or less carbon atoms, or a group in which the hydrogen atoms of these are substituted with any of the following: a halogen atom, a hydroxyl group, a carboxyl group, an amino group, an alkyl-substituted amino group having 5 or less carbon atoms, a hydroxyalkyl-substituted amino group having 5 or less carbon atoms in an alkyl chain, or a mercapto group, or any of the following: an amino group, an alkyl-substituted amino group having 5 or less carbon atoms, a hydroxyalkyl-substituted amino group having 5 or less carbon atoms in an alkyl chain, a mercapto group, a hydroxyl group, a carboxyl group, a halogen atom, or a hydrogen atom.

2. A method for forming a porous preform layer on one or both sides of the copper sheet or substrate as a copper plating film, wherein the preform layer consists of copper particles and has an average porosity of 11% or more and 78% or less, as defined below. This method involves placing a copper sheet or substrate on the cathode side of an acidic electrolytic copper plating solution according to claim 1 and performing acidic electrolytic copper plating. The average porosity of the preform layer is calculated by analyzing the cross-section of the preform layer using a scanning electron microscope over the entire area (S) of the preform layer. 1 ) and the area of ​​the void portion in the preform layer (S 2 This is the arithmetic mean of the porosity (P) calculated using the following formula (A) based on the above. P(%)= (S 2 / S 1 )×100 (A)

3. The method for forming a preform layer according to Claim 2, wherein the surface of the copper particles is coated with copper nanoparticles smaller than the average particle size of the copper particles, and the average particle size calculated from the BET value of the copper nanoparticles is 9.59 nm or more and 850 nm or less.

4. A method for manufacturing a bonding sheet, wherein a porous preform layer is formed on one or both sides of the copper sheet by the method of claim 2 or 3.

5. A method for manufacturing a bonded body by laminating a substrate and an electronic component via a bonding sheet manufactured by the method of claim 4, and then pressurizing and heating the substrate and the electronic component in the lamination direction.

6. A method for manufacturing a bonding substrate, wherein a porous preform layer is formed on one side of the substrate by the method of claim 2 or 3.

7. A method for manufacturing a bonded body by laminating a bonding substrate manufactured by the method of claim 6 and an electronic component via a porous preform layer, and then pressurizing and heating the bonding substrate and the electronic component in the lamination direction.

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