Laminate and circuit board, and method for manufacturing a laminate.

Abstract

To provide a laminate capable of reducing cost and environmental load without performing zincate treatment conventionally required and excellent in adhesion between an aluminum base material and a nickel plating layer.SOLUTION: A laminate 1 includes an anchor shaped part 32 having a nickel plating layer 12 directly laminated on at least one surface of an aluminum base material 11 and having a part of the nickel plating layer 12 embedded in an anchor shape in the depth direction of the aluminum base material 11 on an interface between the nickel plating layer 12 and the aluminum base material 11. The anchor shaped part has one or more pieces / 120 μm in the TD direction in the microscopic field of a ND-TD cross-section.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a laminate, a circuit board, and a method for manufacturing a laminate.

Background Art

[0002] Conventionally, copper has been used in circuits such as printed wiring boards. In recent years, circuits using aluminum have been studied for the purpose of cost reduction and weight reduction.

[0003] Aluminum is a lightweight and inexpensive metal compared to copper. However, since the oxide film present on the surface hinders bonding with solder, the bonding strength is not sufficient even if soldering is directly performed on the surface of aluminum. Therefore, when performing soldering on the aluminum surface, for example, Patent Document 1 discloses a method of forming a zinc layer by zinc replacement plating and then forming a nickel plating layer thereon. By forming the zinc layer by this zinc replacement plating, the adhesion between the aluminum base material and the nickel plating layer can be ensured.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, the zinc replacement plating (zincate treatment) disclosed in Patent Document 1 not only has a long manufacturing process and high cost, but also has a large environmental load of waste liquid, which is a problem.

[0006] From the above background, it has been required that nickel plating can be directly performed on the aluminum surface without zinc replacement plating.

[0007] Therefore, the object of the present invention is to provide a laminate that eliminates the need for zincate treatment, which was previously required, thereby reducing costs and environmental impact, and that exhibits excellent adhesion between the aluminum substrate and the nickel plating layer. [Means for solving the problem]

[0008] In view of the above problems, the inventors of the present invention have found that by forming a specific uneven shape on the surface of an aluminum substrate, the adhesion between the aluminum substrate and the nickel plating is significantly improved, even without performing zincate treatment on the aluminum substrate.

[0009] In other words, the present invention has the following features. 1. The laminate of the present invention has a nickel plating layer directly laminated on at least one surface of an aluminum substrate, and at the interface between the nickel plating layer and the aluminum substrate, a portion of the nickel plating layer is embedded in an anchor shape in the depth direction of the aluminum substrate, or a portion of the aluminum substrate protrudes in an anchor shape in the depth direction of the nickel plating layer, and the anchor-shaped portions are arranged at a density of one or more per 120 μm in the TD direction in the microscopic field of view of the ND-TD cross section. 2. The aluminum substrate is preferably at least one of an aluminum foil with a thickness of 5 μm or more and 200 μm or less, and an aluminum plate with a thickness exceeding 200 μm and 2 mm or less. 3. The circuit board of the present invention is formed by laminating the laminate described in 1 or 2 above in a circuit pattern on at least one surface of an insulating substrate. 4. A method for manufacturing the laminate described in 1 or 2 above, comprising, in order, a step of roughening the surface of at least one surface of an aluminum substrate, and a plating step of plating nickel onto the surface of the roughened aluminum substrate. 5. Furthermore, the manufacturing method of the present invention comprises, in order, a step of roughening the surface of at least one surface of an aluminum substrate, and a plating step of plating nickel onto the surface of the roughened aluminum substrate, wherein the aluminum substrate is aluminum foil made of an aluminum alloy containing 0.2% by mass or more and 1.7% by mass or less of iron, and the roughening treatment is preferably chemical etching using hydrochloric acid as the etching solution. [Effects of the Invention]

[0010] The laminate of the present invention, by having the above configuration, exhibits excellent adhesion between the nickel plating layer and the aluminum substrate without the need for zincate treatment, and provides excellent adhesion strength with solder when the laminate is used in the circuit of a printed wiring board. Furthermore, the manufacturing method of the present invention can firmly bond the aluminum substrate and the nickel plating layer without including a zincate treatment step, and since it does not include the zincate treatment step, it can reduce costs and environmental impact. Moreover, the circuit board of the present invention is lighter and more cost-effective than conventional circuit boards using a copper substrate. [Brief explanation of the drawing]

[0011] [Figure 1] (a) is a schematic cross-sectional view of the aluminum substrate before the surface roughening process, (b) is a schematic cross-sectional view of the aluminum substrate after the surface roughening process, and (c) is a schematic cross-sectional view of the aluminum substrate (laminated body) after the plating process. [Figure 2] This is a secondary electron image obtained by FE-SEM of the ND-TD cross-section of the laminate according to Example 1. [Figure 3] This is a secondary electron image obtained by FE-SEM of the ND-TD cross-section of the laminate according to Example 4. [Figure 4] This is a secondary electron image obtained by FE-SEM of the ND-TD cross-section of the laminate according to Comparative Example 3. [Figure 5] This is a secondary electron image obtained by FE-SEM of the ND-TD cross-section of an aluminum substrate after the surface roughening treatment step and before the plating step according to Example 1. [Modes for carrying out the invention]

[0012] The laminate of the present invention will be described in detail below with reference to the drawings.

[0013] (Laminated structure) As shown in Figure 1(c), the laminate of the present invention is characterized in that a nickel plating layer 12 is directly laminated on at least one surface of an aluminum substrate 11, and at the interface between the nickel plating layer 12 and the aluminum substrate 11, a part of the nickel plating layer 12 is embedded in an anchor shape in the depth direction (thickness direction) of the aluminum substrate 11, and the anchor-shaped portion is such that there is one or more per 120 μm in the TD direction in the microscopic field of view of the ND-TD cross section.

[0014] By possessing the above characteristics, when used in circuit products and soldered, it offers excellent solder adhesion strength (both between solder and nickel plating layer, and between nickel plating layer and aluminum substrate), while also reducing costs and environmental impact because it does not contain a zincate treatment layer between the aluminum substrate and the nickel plating layer.

[0015] (Aluminum base material) The aluminum substrate used in the laminate of the present invention has an uneven surface structure, and the shape of at least a part of the uneven structure corresponds to the shape of the anchor-shaped portion when a nickel plating layer is laminated to form a laminate. The aluminum substrate may be an aluminum plate or an aluminum foil. The material of the aluminum substrate can be known pure aluminum or an aluminum alloy. When using an aluminum alloy, an aluminum alloy can be used in which at least one alloying element from silicon (Si), iron (Fe), copper (Cu), manganese (Mn), magnesium (Mg), chromium (Cr), zinc (Zn), titanium (Ti), vanadium (V), gallium (Ga), nickel (Ni), calcium (Ca), and boron (B) is added within the necessary range, or an aluminum alloy with a limited content of the above alloying elements can be used. In particular, it is preferable to use an aluminum alloy foil containing 0.2 to 1.7 mass% iron, for example, aluminum alloy foils of materials such as 1N30, 8079, and 8021 as specified in JIS. When the iron concentration is within the above range, Al-Fe intermetallic compounds act as the starting point for the dissolution of aluminum during etching, allowing the desired surface shape to be achieved in a shorter time. Furthermore, aluminum alloy foil with an iron concentration within the above range exhibits good aluminum foil rolling properties. The composition of the above aluminum alloy can be measured, for example, by an ICP emission spectrometer (JIS H1307).

[0016] As shown in Fig. 1(b), the surface of the aluminum substrate 11 has an uneven shape corresponding to the shape of the anchor-like portions protruding from the interface with the nickel plating layer described later. In the recess 42 on the surface of the aluminum substrate, it is preferable that a protruding portion protruding from a part or all of the opening edge portion of the recess 42 toward the center in the opening width direction is formed in part or all of the recess 42. As a result, the opening width of the recess 42 becomes narrower than its inside, and the nickel plating formed so as to fill such a recess functions as an anchor-like portion that makes it difficult to separate the aluminum substrate 11 and the nickel plating layer 12. Also, when an isolated portion 46 (void) is observed (although it is a void in Fig. 1(b), it is observed as if nickel is isolated in Fig. 1(c)), a recess 42 exists in the depth direction within the visual field. That is, the isolated portion 46 (void) observed in the cross-sectional observation can be considered as a cross-section of the recess 42.

[0017] Alternatively, the anchor-like portion is a convex portion 44 protruding from the surface of the aluminum substrate 11. The convex portion 44 has a thick portion and a thin portion, and has a thin portion at a position close to the root of the convex portion (on the aluminum substrate side in the laminate), and a thick portion is arranged at a position close to the tip of the convex portion (on the nickel plating layer side in the laminate). It may have a convex shape. The convex portion 44 also functions as the anchor-like portion 34 in Fig. 1(c) by nickel plating. Also, when an isolated portion 48 (in Fig. 1(b), aluminum is isolated and surrounded by a void, but in Fig. 1(c), it is surrounded by nickel plating) is observed, the convex portion 44 exists in the depth direction within the visual field. That is, the isolated portion 48 (island-shaped aluminum) observed in the cross-sectional observation can be considered as a cross-section of the convex portion 44.

[0018] The surface of the aluminum substrate may or may not have a natural oxide film. Usually, it is known that the presence of the oxide film deteriorates the adhesion between the aluminum substrate and the plating layer, so it is better to have no oxide film. However, the aluminum substrate used in the laminate of the present invention can have strong adhesion to the nickel plating layer even if an oxide film is present by having a predetermined surface shape.

[0019] The surface roughness of the aluminum substrate is not particularly limited, but the arithmetic mean roughness Ra in the TD direction is preferably 0.25 μm or more and 1.50 μm or less, and the ten-point mean roughness Rz in the TD direction is preferably 2.5 μm or more and 10.0 μm or less. When the surface roughness is within the above range, the adhesion between the aluminum substrate and the nickel plating layer can be further strengthened. However, sufficient adhesion cannot be obtained when only the surface roughness is within the above range without the anchor portion. The surface roughness in this specification is the average value of N = 3 when measured with a stylus roughness meter (SURFCOM1400D manufactured by Tokyo Seimitsu Co., Ltd.) according to the JIS B0601:1994 standard. The TD direction is a direction perpendicular to the rolling direction during the production of the aluminum foil or aluminum plate and parallel to the rolling surface.

[0020] The thickness of the aluminum substrate is not particularly limited, but considering the productivity of the laminate of the present invention, when the aluminum substrate is an aluminum foil, it is preferably 5 μm or more and 200 μm or less. Within the above range, since the aluminum substrate has flexibility, the plating process can be continuously processed by roll-to-roll, so the productivity is improved. It is particularly preferable that the thickness of the aluminum substrate is 15 μm or more and 150 μm or less. Since the nickel plating layer is hard and has low flexibility, when the aluminum substrate is within the above range, the flexibility of the laminate is further improved, and the productivity can be further improved.

[0021] When the thickness of the aluminum substrate is less than 5 μm, the strength of the aluminum substrate itself decreases. Therefore, even if the adhesion between the aluminum substrate and the nickel plating layer and the adhesion between the laminate and the solder are sufficient, the substrate may break, so there is a possibility that sufficient adhesion strength cannot be exhibited.

[0024] 22>

[0022] (Nickel plating layer) In the laminate of the present invention, the nickel plating layer laminated on the surface of the aluminum substrate is a layer laminated by a plating process on the aluminum substrate, and may be a nickel plating layer laminated by either electroplating or electroless plating. The nickel plating layer may be laminated on one surface of the aluminum substrate or formed on both surfaces, but at least the interface with the aluminum substrate has an anchor-shaped portion.

[0023] The thickness of the nickel plating layer is preferably between 1 μm and 10 μm. Within this range, the adhesion between the aluminum substrate and the nickel plating layer, and between the nickel plating layer and the solder, is strengthened. If the nickel plating layer is less than 1 μm thick, it becomes difficult to uniformly plate the aluminum substrate surface, and adhesion to the solder may also be poor. If the nickel plating layer is more than 10 μm thick, the nickel plating layer becomes hard and brittle, which may result in a loss of flexibility when used in a laminate. Furthermore, if the laminate is applied to a circuit product, the risk of circuit breakage increases. The thickness of the nickel plating layer can be determined by observing the ND-TD cross-section within the microscope field of view, randomly measuring the length from the outermost part to the deepest part of the nickel plating layer in the ND direction (thickness direction) at five points, and calculating the average value. The ND-TD cross-section is a cross-section perpendicular to the rolling direction of the aluminum substrate, such as aluminum foil or aluminum plate.

[0024] The surface roughness of the nickel plating layer on the side opposite to the aluminum substrate is not particularly limited, but when applied to circuit products, it is preferable that the roughness is such that interfacial delamination between the nickel plating layer surface and the solder is less likely to occur after soldering.

[0025] (anchor) As an example of a cross-section of the laminate of the present invention, the shape of the anchor-shaped portion will be explained using the schematic diagram in Figure 1(c). The anchor-shaped portion refers to an anchor-shaped portion 32 (projection) that protrudes from the nickel plating layer toward the aluminum substrate, and the anchor-shaped portion 32 (projection) has a thicker diameter portion and a thinner diameter portion, with the thicker portion located towards the deeper part and the thinner portion towards the shallower part in the depth (ND) direction of the aluminum substrate. In this specification, when observed in the ND-TD cross section within the microscope field of view, isolated nickel portions 36 located on the aluminum substrate side, spaced apart from the interface between the aluminum substrate and the nickel plating layer, are also treated as anchor-shaped portions. This is because, as illustrated in Figure 1(c), when the isolated portion 36 is observed in cross-sectional observation, a protrusion exists in the depth direction within the field of view; in other words, the isolated portion 36 observed in cross-sectional observation is a cross-section of the protrusion. Furthermore, it is preferable that the length of the anchor-shaped portion in the thickness direction be 1 μm or more. When the length of the anchor-shaped portion in the thickness direction is 1 μm or more, the adhesion between the aluminum substrate and the nickel plating layer can be made stronger.

[0026] Furthermore, the anchor-shaped portion may be a projection 34 that protrudes in an anchor shape from the aluminum substrate toward the nickel plating layer. Also, an isolated portion 38 of aluminum present on the nickel plating layer side is also treated as an anchor-shaped portion.

[0027] (Measurement method) The anchor-shaped portions 32, 34, 36, and 38 should ideally be present at a rate of one or more per 120 μm in the TD direction in the microscope field of view of the ND-TD cross section. The number of anchor-shaped portions in this case can be determined by observing the cross section at a magnification of 1000x using FE-SEM, observing a 120 μm range in the TD direction within the observation field, counting the anchor-shaped portions corresponding to the above at the interface between the nickel plating layer on the soldering side and the aluminum substrate, and then calculating the average value of 5 points by randomly changing the field of view. By ensuring that there is one or more anchor-shaped portions per 120 μm in the TD direction, excellent adhesion between the aluminum substrate and the nickel plating layer can be more reliably ensured. When nickel plating layers are laminated on both sides of the aluminum substrate and soldering is performed on both sides of the nickel plating layer, the interface between each nickel plating layer and the aluminum substrate should be measured and evaluated separately.

[0028] (Circuit board) The laminate of the present invention can be suitably used in circuit boards. That is, according to another aspect of the present invention, a circuit board is provided in which the above-mentioned laminate is formed in a circuit pattern on at least one surface of an insulating substrate and laminated thereon. By using the laminate of the present invention as a material for a circuit board, it is possible to obtain a circuit board that is lighter and less expensive than conventionally used copper, and has excellent soldering strength even when using untreated aluminum as the base material. The laminate may be provided on one side of the insulating substrate or on both sides. The insulating substrate is not particularly limited and can be made of known resins, glass, ceramics, or composite materials of two or more of these. Preferably, a substrate made of insulating resin is preferred in terms of lightness. Specifically, rigid substrates include substrates made of resins such as paper phenolic resin, glass cloth epoxy resin, and polyamide resin. Flexible substrates include substrates made of films such as PET (polyethylene terephthalate) film, PEN (polyethylene naphthalate) film, and PI (polyimide) film. Among these, a resin substrate that has heat resistance and can withstand the heat during soldering is preferred. On the other hand, glass substrates include soda-lime glass substrates and alkali-free glass substrates, and ceramic substrates include alumina substrates and aluminum nitride substrates.

[0029] Furthermore, known adhesives can be used to bond the insulating substrate and the laminate. Examples include urethane adhesives, acrylic adhesives, silicone adhesives, epoxy adhesives, and the like.

[0030] (Method of manufacturing a laminate) The laminate of the present invention can be suitably manufactured by the following steps. Specifically, the process comprises, in order, a step of roughening at least one surface of an aluminum substrate, and a plating step of plating nickel onto the roughened surface of the aluminum substrate. Preferably, the aluminum substrate is an aluminum foil made of an aluminum alloy containing 0.2% by mass or more and 1.7% by mass or less of iron, and the surface roughening treatment is chemical etching using hydrochloric acid as the etching solution. The following details each step.

[0031] (Process for roughening the surface of an aluminum substrate) In the step of roughening at least one surface of an aluminum substrate, the aluminum substrate is prepared prior to this. The aluminum substrate before surface roughening can be one manufactured by known methods. For example, a molten aluminum or aluminum alloy having the above-mentioned predetermined composition can be prepared, and the resulting ingot can be appropriately homogenized. Subsequently, the ingot can be subjected to hot rolling and cold rolling to obtain an aluminum substrate. Furthermore, an intermediate annealing treatment may be performed during the cold rolling process at a temperature of 50 to 500°C, particularly in the range of 150 to 400°C. Alternatively, after the cold rolling process, an annealing treatment may be performed at a temperature of 150 to 650°C, particularly in the range of 200 to 400°C, to obtain a soft aluminum substrate. By performing the annealing treatment, not only can the flexibility of the aluminum substrate be improved, but the rolling oil on the surface of the aluminum substrate can also be removed.

[0032] The thickness of the aluminum substrate before roughening treatment is not particularly limited. Considering the productivity of the laminate of the present invention, in the case of aluminum foil, it is preferably 5 μm to 200 μm, and particularly preferably 15 μm to 150 μm. In the case of aluminum plate, it is preferably more than 200 μm and 2 mm or less in thickness. The thickness of the aluminum substrate is appropriately adjusted in the cold rolling process by controlling the spacing between the rolling rolls, the load, etc.

[0033] The method for roughening the aluminum substrate before surface roughening is not limited, and any method that can obtain the predetermined surface irregularity shape of the present invention is acceptable. In particular, surface roughening by chemical etching is preferred, and chemical etching using hydrochloric acid as the etching solution is even more preferred.

[0034] An unstable oxide film containing oil and fine particles exists on the surface of the aluminum substrate due to the rolling process. However, the roughening treatment removes this oxide film, and further dissolves the aluminum substrate surface, forming a complex uneven shape. The aluminum substrate surface does not dissolve uniformly across its entire surface; rather, the dissolution progresses in the thickness direction, leaving some aluminum intact. As a result, the depressions extend in the depth direction of the aluminum substrate, and the opening width of these depressions becomes narrower than the interior.

[0035] Chemical etching is carried out using acidic or alkaline solutions. For example, single solutions of sulfuric acid, phosphoric acid, chromic acid, nitric acid, hydrofluoric acid, acetic acid, caustic soda, ferric chloride, perchloric acid, etc., or mixtures of two or more of these, can be used as etching solutions. Alternatively, the above solutions may be appropriately diluted with a solvent such as water and used as etching solutions. Preferably, an aqueous solution of hydrochloric acid with a concentration of 0.5% to 40% by mass can be used.

[0036] The etching time and etching solution temperature can be appropriately adjusted depending on the type and concentration of the etching solution and the shape and size of the required surface irregularities on the aluminum substrate. For example, when the solution temperature is room temperature (around 20°C), it is preferable to perform the etching process for about 20 to 200 seconds using the immersion method or the spray method. The etching solution may also be heated to shorten the etching time.

[0037] The surface roughening treatment may be performed on one or both sides of the aluminum substrate. Usually, it is sufficient to apply it to only one side, in which case a nickel plating layer is laminated onto the roughened surface of the aluminum substrate, and when performing soldering, for example, the soldering is applied to the roughened and nickel-plated surface.

[0038] Furthermore, prior to the surface roughening treatment, degreasing and cleaning may be performed as necessary. The method of degreasing and cleaning is not particularly limited and known methods can be used, for example, by using an alkaline solution such as an aqueous solution of caustic soda.

[0039] (Plating process involving nickel plating) In the method for manufacturing a laminate of the present invention, the nickel plating layer can be formed by known methods, such as electroplating or electroless plating. Specifically, following a surface roughening treatment, nickel plating is performed on the surface of the aluminum substrate by immersing it in an electrolytic nickel plating solution and applying an electric current, or by immersing it in an electroless nickel plating solution. At this time, an anchor-shaped portion is formed by the nickel plating layer being laminated so as to fit into the recesses, or by the nickel plating layer being laminated so as to surround the convex portions. The formation of the anchor-shaped portion ensures adhesion between the aluminum substrate and the nickel plating layer. By providing a laminate having an anchor-shaped portion at the interface as described above, the present invention can obtain plating adhesion and adhesion strength after soldering equivalent to that of a laminate that has undergone zincate treatment, while omitting the zincate treatment, which has a high process load.

[0040] After forming the nickel plating layer, post-treatment may be performed to improve solder wettability. Post-treatment methods include copper plating, tin plating, and gold plating.

[0041] The present invention will be specifically described below with reference to examples and comparative examples. However, the present invention is not limited to the examples. [Examples]

[0042] (Example 1) Aluminum foil (JIS-8021 material, rigid foil, 35 μm thick, 200 mm x 300 mm) was prepared as the aluminum substrate. Next, both sides of the prepared aluminum foil were subjected to a surface roughening treatment by etching with a hydrochloric acid aqueous solution (8% by mass concentration) at a liquid temperature of 25°C for 40 seconds using the spray method. After the surface roughening treatment, the aluminum foil was washed with water and dried, and the surface roughness of the roughened side of the aluminum foil was measured using a stylus-type surface roughness meter (SURFCOM1400D, manufactured by Tokyo Seimitsu Co., Ltd.). Next, the aluminum foil, after surface roughening, was immersed in an electroless nickel plating solution (Top Nicolon MP-GE heavy metal-free medium phosphorus type manufactured by Okuno Pharmaceutical Co., Ltd.) to perform nickel plating. The solution temperature was set to 90°C, and the foil was immersed for 15 minutes to form a nickel plating layer. After that, it was washed with water and dried to produce a laminate.

[0043] (Cross-sectional observation) A sample was cut from the obtained laminate for observation, and the cross-section (ND-TD) of the sample was smoothed using a cross-section polisher (SM-09010, JEOL Ltd.). Then, a cross-section of a certain region of the ND-TD cross-section, including the nickel plating layer and the interface between the nickel plating layer and the aluminum substrate, was observed using a field emission scanning electron microscope (JSM-7200F, JEOL Ltd.) FE-SEM (see Figure 2). Figure 2 shows that multiple anchor-like structures are formed. In addition, the number of anchor-like structures at the interface between the nickel plating layer and the aluminum substrate on the soldering side was counted in a 120 μm range in the TD direction within a 1000x magnification microscope field of view. The above observation was performed in 5 fields of view, and the average value was calculated. If there was one or more anchor-like structures per 120 μm (TD), it was marked with a circle (○); if there was less than one, it was marked with a cross (×). The ND-TD cross-section of the aluminum substrate with a surface roughened before nickel plating was observed in the same manner (see Figure 5). From Figure 5, it can be seen that recesses (42) and isolated areas (46) are formed on the surface of the aluminum substrate.

[0044] (Soldering evaluation) On one surface of a nickel-plated layer of a laminate evaluation sample (size 60mm x 70mm), solder paste containing Sn, Ag, and Cu (product name "SN97C P506 D4", manufactured by Nippon Superior Co., Ltd.) was applied in two dots with a center distance of 3.35mm, each dot having an area of ​​1.25mm x 1.60mm and a thickness of 80μm. A 3216 type chip resistor was then placed so as to uniformly span across these two dots.

[0045] The aforementioned sample was placed in a benchtop vacuum solder reflow system (RSS-450-210, manufactured by Unitem Japan Co., Ltd.), evacuated, and then heated to 250°C in a nitrogen atmosphere with a flow rate of 1 L / min, and held for 30 seconds.

[0046] After reflow soldering was complete, the shear strength of the soldered chip resistors was measured using a bond tester (Nordson DAGE series 4000). The tool movement speed was 0.3 mm / second. When the aluminum substrate in the laminate is aluminum foil, it is preferable to reinforce the evaluation sample by heat-bonding it to the FR-4 substrate using prepreg. Ten measurements were taken, and the average value was taken as the adhesion strength. The results of the adhesion strength (shear strength) are shown in Table 1. ○ indicates a shear strength of 50N or higher, and × indicates a shear strength of less than 50N.

[0047] (Example 2) A laminate was fabricated in the same manner as in Example 1, except that the etching solution temperature was set to 15°C and the etching time to 15 seconds.

[0048] (Example 3) A laminate was fabricated in the same manner as in Example 1, except that the etching solution temperature was 30°C and the etching time was 20 seconds.

[0049] (Example 4) A laminate was fabricated in the same manner as in Example 1, except that the aluminum foil composition was 1N30 hard foil, the foil thickness was 15 μm, and the etching solution temperature was 30°C. Figure 3 shows an FE-SEM observation of the ND-TD cross section. From Figure 3, it can be seen that multiple anchor-shaped portions have been formed.

[0050] (Example 5) The laminate was fabricated in the same manner as in Example 4, except that the etching solution temperature was set to 37°C.

[0051] (Comparative Example 1) The laminate was prepared in the same manner as in Example 1, except that no surface roughening treatment was performed.

[0052] (Comparative Example 2) The laminate was fabricated in the same manner as in Example 1, except that the surface roughening treatment involved sanding the surface with SiC Paper #500 (manufactured by Struers) instead of acid etching.

[0053] (Comparative Example 3) A laminate was prepared in the same manner as in Comparative Example 1, except that 1N99 soft aluminum foil with a foil thickness of 120 μm was used. Figure 4 shows an FE-SEM image of the ND-TD cross section. From Figure 4, it can be seen that no anchor-shaped portion was formed in the laminate of Comparative Example 3.

[0054] Each example and comparative example was evaluated. The results are shown in Table 1.

[0055] [Table 1]

[0056] As shown in the results above, the laminate of the present invention exhibits excellent adhesion between the aluminum substrate and the nickel plating layer, even without zincate treatment, and therefore demonstrates superior adhesion strength when soldered. [Explanation of symbols]

[0057] 1. Laminate 2. Aluminum substrate before roughening treatment 11. Aluminum base material 12 Nickel plating layer 32, 34 Anchor-shaped part (protruding part) 36, 38 Anchor-like part (isolated part) 42 recess 44 Convex part 46 Isolated area 48 Isolated area

Claims

1. A step of roughening at least one surface of an aluminum substrate, The process includes, in this order, a plating step of plating nickel onto the surface of the roughened aluminum substrate, The aluminum substrate is an aluminum foil made of an aluminum alloy containing 0.2% by mass or more and 1.7% by mass or less of iron. The aforementioned surface roughening treatment is chemical etching using hydrochloric acid as the etching solution. The laminate obtained by the aforementioned plating process A method for manufacturing a laminate, characterized in that a nickel plating layer is directly laminated on at least one surface of the aluminum substrate, and at the interface between the nickel plating layer and the aluminum substrate, a portion of the nickel plating layer is embedded in an anchor shape in the depth direction of the aluminum substrate, or a portion of the aluminum substrate protrudes in an anchor shape in the depth direction of the nickel plating layer, and the anchor-shaped portion is present at one or more per 120 μm in the TD direction in the microscopic field of view of the ND-TD cross section.

2. The method for manufacturing a laminate according to claim 1, characterized in that the aluminum substrate is at least one of an aluminum foil having a thickness of 5 μm or more and 200 μm or less, and an aluminum plate having a thickness of more than 200 μm and 2 mm or less.

3. The method for manufacturing a laminate according to Claim 1, wherein the aluminum substrate is an aluminum alloy foil of material 1N30, 8079, or 8021 as defined in JIS.

4. The method for manufacturing a laminate according to claim 1, wherein the length in the thickness direction of the anchor-shaped portion is 1 μm or more.

5. A method for manufacturing a circuit board using a laminate obtained by the method for manufacturing a laminate according to any one of Claims 1 to 4, A method for manufacturing a circuit board, comprising the step of forming the laminate in a circuit pattern on at least one surface of an insulating substrate and then stacking them.

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