Carrier metal foil, composite metal foil, and circuit board

Abstract

This invention discloses a carrier metal foil, a composite metal foil, and a circuit board. The carrier metal foil has a thickness of 6μm to 20μm and contains columnar crystals with a (220) texture and an extreme density of columnar crystals greater than or equal to 0.7. Since columnar crystals with a (220) texture possess intrinsic thermal stability, this invention, by limiting the thickness of the carrier metal foil to 6μm to 20μm and specifying an extreme density of columnar crystals with a (220) texture greater than or equal to 0.7, ensures a relatively stable coefficient of thermal expansion. Furthermore, in the circuit board manufacturing process, this effectively prevents warping of the circuit board substrate and improves the yield rate.

Description

Technical Field

[0001] This invention relates to the field of electronic information materials technology, and in particular to a carrier metal foil, a composite metal foil, and a circuit board. Background Technology

[0002] With the rapid development of global information technology towards digitalization and networking, there is a growing demand for ultra-high-capacity information transmission, high-frequency, high-speed, and ultra-high-density information processing. This undoubtedly places higher demands on PCBs (Printed Circuit Boards). Currently, fabricating PCBs capable of transmitting high-frequency signals requires the use of a metal foil containing a carrier. This metal foil is pressed onto the PCB substrate or prepreg, and the carrier is subsequently peeled off to facilitate subsequent exposure and development. During this process, the carrier often experiences significant variations in its CTE (Coefficient of Thermal Expansion), leading to warping of the entire PCB substrate. This hinders subsequent circuit fabrication, resulting in material waste and reduced yield. Summary of the Invention

[0003] This invention provides a carrier metal foil, a composite metal foil, and a circuit board, which have a low coefficient of thermal expansion and can ensure that the coefficient of thermal expansion is relatively stable during the circuit board manufacturing process, effectively preventing warping of the circuit board substrate and improving the yield.

[0004] To solve the above-mentioned technical problems, the first aspect of the present invention provides a carrier metal foil with a thickness of 6μm to 20μm, the carrier metal foil containing columnar crystals, and the extreme density of the columnar crystals with (220) texture is greater than or equal to 0.7.

[0005] As a preferred embodiment, the extreme density of columnar crystals with (111) texture in the carrier metal foil is less than or equal to 2.39.

[0006] As a preferred embodiment, the extreme density of columnar crystals with a (200) texture in the carrier metal foil is less than or equal to 1.97.

[0007] As a preferred embodiment, the grain size of the columnar crystals is 0.01μm to 20μm.

[0008] As a preferred embodiment, the roughness Rz of the carrier surface of the carrier metal foil is 0.4μm~2.5μm; wherein, the carrier surface is the surface used to connect the functional layer.

[0009] As a preferred embodiment, the material of the carrier metal foil includes at least one of nickel, chromium, copper, silver, gold, zinc, and aluminum.

[0010] As a preferred embodiment, an antioxidant layer is provided on at least one surface of the metal foil used as the carrier.

[0011] As a preferred embodiment, the material of the antioxidant layer includes at least one of nickel, chromium, copper, silver, gold, zinc, iron, titanium, and aluminum.

[0012] A second aspect of the present invention provides a composite metal foil, the composite metal foil comprising a carrier metal foil as described in any of the first aspects.

[0013] A third aspect of the present invention provides a circuit board, the circuit board comprising a circuit board substrate and a composite metal foil as described in the second aspect, which is pressed onto the circuit board substrate.

[0014] Compared with the prior art, the beneficial effect of the embodiments of the present invention is that by limiting the thickness of the carrier metal foil to 6μm~20μm and the extreme density of the (220) texture with preferred orientation to be greater than or equal to 0.7, the synergistic effect of the above technical features significantly reduces the thermal expansion coefficient of the carrier metal foil, and in the circuit board manufacturing process, it can ensure that the thermal expansion coefficient is relatively stable, thereby effectively avoiding warping of the circuit board substrate and improving the yield. Attached Figure Description

[0015] Figure 1 This is a schematic diagram of the structure of the first type of carrier metal foil in the embodiments of the present invention; Figure 2 This is a schematic diagram of the structure of the second type of carrier metal foil in this embodiment of the invention; Figure 3 This is a schematic diagram of the structure of the third type of carrier metal foil in this embodiment of the invention; Among them, 1. carrier metal foil; 2. columnar crystals; 3. anti-oxidation layer. Detailed Implementation

[0016] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0017] In the description of this application, it should be noted that, unless otherwise defined, all technical and scientific terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used in this specification is for the purpose of describing specific embodiments only and is not intended to limit the invention. Those skilled in the art can understand the specific meaning of the above terms in this application based on the specific circumstances.

[0018] Please see Figure 1 The first aspect of the present invention provides a carrier metal foil 1, the thickness of the carrier metal foil 1 is 6μm~20μm, the carrier metal foil 1 contains columnar crystals 2, and the extreme density of the columnar crystals 2 with (220) texture is greater than or equal to 0.7.

[0019] It is worth noting that in practical applications, the carrier metal foil 1 is stacked with the functional layer. The functional layer is usually a thin metal foil used to form circuits after being pressed onto the circuit board substrate. The carrier metal foil 1 is used to support and protect the functional layer, so that the functional layer is not damaged by external contact or collision and meets the requirements for the production of extremely narrow circuits. After the functional layer is pressed onto the circuit board substrate, the carrier metal foil 1 needs to be peeled off.

[0020] To avoid excessive CTE variation of the carrier metal foil 1 during the circuit board manufacturing process, this embodiment first limits the thickness of the carrier metal foil 1 to 6μm~20μm, for example, its thickness is 6μm, 9μm, 11μm, 13μm, 15μm, 16μm, 17μm, 18μm, 19μm, 20μm, etc., and this embodiment does not make a specific limitation. The carrier metal foil 1 can be prepared by chemical deposition, physical vapor deposition or electrodeposition, and electrodeposition is preferred.

[0021] Furthermore, the carrier metal foil 1 contains columnar crystals 2, and the columnar crystals 2 with (220) texture have the intrinsic property of thermal stability. The limit of the columnar crystals 2 with (220) texture to be greater than or equal to 0.7 will make the CTE of the carrier metal foil 1 more stable and the rate of change smaller. At the same time, it will ensure that the roughness Rz of the carrier metal foil 1 will not fluctuate greatly within the set value range (for example, if the roughness Rz of the carrier metal foil 1 is set at 0.9 micrometers, the measured Rz value will be stable around 0.9 micrometers; if the roughness Rz of the carrier metal foil 1 is set at 1.2 micrometers, the measured Rz value will be stable around 1.2 micrometers and will not fluctuate greatly). For example, the pole density of columnar crystal 2 with (220) texture is 0.7, 0.9, 1.1, 1.5, 2.1, 3.2, 3.8, 4.2, 4.5, 4.8, or any range of two values. This embodiment does not impose a specific limitation. It is worth noting that pole density is a key parameter for quantifying the strength of texture. It refers to the degree of concentration of grain orientation in spatial distribution relative to random distribution in polycrystalline materials. It is obtained through pole figure statistics of EBSD (Electron BackScatter Diffraction). In this embodiment, the maximum density of columnar crystals 2 with (220) texture is greater than or equal to 0.7, ensuring a high proportion of columnar crystals 2 with (220) texture. This allows for the formation of a stable, preferred orientation within the carrier metal foil 1. Since the columnar crystals 2 with (220) texture possess intrinsic thermal stability, the stability of the thermal expansion coefficient of the carrier metal foil 1 can be significantly improved. Furthermore, in the circuit board fabrication process, a relatively stable thermal expansion coefficient can be ensured, effectively preventing warping of the circuit board substrate and improving yield. Specifically, the thermal expansion coefficient of the carrier metal foil 1 in this embodiment is stable with a small fluctuation range.

[0022] Preferably, the extreme density of the columnar crystal 2 with (220) texture is 0.7 to 3.3. For example, the extreme density of the columnar crystal 2 with (220) texture is preferably 0.7, 0.9, 1.1, 1.3, 1.5, 1.7, 1.9, 2.1, 2.3, 2.5, 2.8, 3, 3.1, 3.3, etc. or any two of these ranges. This embodiment will not elaborate further.

[0023] As a preferred embodiment, in the carrier metal foil 1, the extreme density of columnar crystals 2 with (111) texture is less than or equal to 2.39.

[0024] Specifically, to further ensure that the carrier metal foil 1 has a low coefficient of thermal expansion, this embodiment also limits the extreme density of columnar crystals 2 with (111) texture in the carrier metal foil 1 to less than or equal to 2.39. For example, the extreme density of columnar crystals 2 with (111) texture is 0.3, 0.5, 0.7, 0.9, 1.1, 1.3, 1.5, 1.7, 1.9, 2.1, 2.39, or any range of two values. This embodiment does not make a specific limitation here. By limiting the extreme density of columnar crystals 2 with (111) texture to the above range, this embodiment can ensure that the extreme density of columnar crystals 2 with (111) texture is not too high, that is, ensure that the proportion of columnar crystals 2 with (111) texture is not too high. At the same time, it works synergistically with the extreme density of (220) texture to avoid the problem of high and large fluctuations in the coefficient of thermal expansion during the circuit board manufacturing process, thereby effectively avoiding the warping of the circuit board substrate.

[0025] Furthermore, if the extreme density of columnar crystals 2 with (111) texture is too high, their relatively low thermal stability may cause the carrier metal foil 1 to warp easily during the process of preparing copper-clad laminates or substrates under high temperature and pressure. Therefore, the extreme density of columnar crystals 2 with (111) texture is limited to not being too high. At the same time, the extreme density of columnar crystals 2 with (220) texture works synergistically to help improve the overall CTE stability of the carrier metal foil 1, making it more suitable for the process of preparing copper-clad laminates or substrates and improving the yield.

[0026] As a preferred embodiment, in the carrier metal foil 1, the extreme density of columnar crystals 2 with (200) texture is less than or equal to 1.97.

[0027] Specifically, in order to further ensure that the carrier metal foil 1 has relatively stable thermal properties, this embodiment also limits the extreme density of columnar crystals 2 with (200) texture in the carrier metal foil 1 to be less than or equal to 1.97. For example, the extreme density of columnar crystals 2 with (200) texture is 0.3, 0.5, 0.7, 0.9, 1.1, 1.3, 1.5, 1.7, 1.97 or any two of these values. This embodiment does not make any specific limitation here. Taking electroplated copper foil as an example, the thermal stability of (200) texture is lower than that of (220) texture. Therefore, in this embodiment, by limiting the extreme density of columnar crystals 2 with (200) texture to the above range, it is possible to ensure that the extreme density of columnar crystals 2 with (200) texture is not too high, that is, to ensure that the proportion of columnar crystals 2 with (200) texture is not too high, thereby reducing its negative impact on the CTE of the carrier metal foil 1, so that the carrier metal foil 1 has better ductility. At the same time, it works synergistically with the extreme density of columnar crystals 2 with (220) texture, so that the carrier metal foil 1 has higher CTE thermal stability, and can ensure that the coefficient of thermal expansion is relatively stable in the circuit board manufacturing process, which can further avoid the warping of the circuit board substrate and improve the yield.

[0028] Furthermore, if the extreme density of columnar crystals 2 with (200) texture is too high, the tensile strength and ductility of the carrier metal foil 1 will be poor. By limiting the extreme density of columnar crystals 2 with (200) texture to the above range, the tensile strength, ductility and toughness of the carrier metal foil 1 can be improved, making it more stable in the production process and reducing the risk of cracks and fractures.

[0029] Specifically, in order to make the carrier metal foil 1 have better thermal stability or a smaller CTE than the above situation, the extreme density of columnar crystals 2 with (220) texture in the carrier metal foil 1 is greater than or equal to 0.7, the extreme density of columnar crystals 2 with (111) texture is less than or equal to 2.39, and the extreme density of columnar crystals 2 with (200) texture is less than or equal to 1.97, and the above three parameters are achieved in synergy.

[0030] As a preferred embodiment, the grain size of the columnar crystal 2 is 0.01μm to 20μm.

[0031] Specifically, in this embodiment, the grain size of the columnar crystal 2 is further defined as 0.01 μm to 20 μm, preferably 0.2 μm to 20 μm. For example, the grain size of the columnar crystal 2 can be 0.02 μm, 0.05 μm, 0.08 μm, 0.1 μm, 0.13 μm, 0.15 μm, 0.2 μm, 0.5 μm, 0.7 μm, 0.9 μm, 1.3 μm, 1.5 μm, 1.8 μm, 2.1 μm, 2.5 μm, 2.8 μm, 3 μm, 3.2 μm, 3.5 μm, 5 μm, 8 μm, 10 μm, 12 μm, 15 μm, 18 μm, 20 μm, etc., or any range of two values. This embodiment does not impose a specific limitation. It is worth noting that the grain size is the diameter along the largest circumcircle of the grain. Grain size has a certain influence on the plastic deformation of polycrystalline structures. The finer the grains, the higher the strength. This is because finer grains have more grain boundaries, which increases the resistance to dislocation movement, making the crystal structure of the carrier metal foil 1 less prone to plastic deformation. Therefore, by limiting the grain size of the columnar crystals 2 to the above-mentioned range, this embodiment can avoid the columnar crystals 2 from being too small and easily undergoing grain morphology changes, thereby avoiding CTE instability. At the same time, it can also avoid the columnar crystals 2 from being too large and affecting the roughness Rz of the carrier metal foil 1.

[0032] The grain size range of columnar crystal 2 can be obtained through EBSD statistics or by statistically analyzing a large number of columnar crystal 2 grain sizes. The grain size of a single columnar crystal 2 is the average of the long axis measurement value and the short axis measurement value of columnar crystal 2.

[0033] As a preferred embodiment, the roughness Rz of the carrier surface of the carrier metal foil 1 is 0.4μm~2.5μm; wherein, the carrier surface is the surface used to connect the functional layer.

[0034] Specifically, in this embodiment, the roughness Rz of the carrier surface of the carrier metal foil 1 is further defined as 0.4μm~2.5μm, preferably 0.7μm~1.5μm. For example, the roughness Rz of its carrier surface is 0.5μm, 0.7μm, 0.8μm, 0.9μm, 1μm, 1.1μm, 1.2μm, 1.3μm, 1.4μm, 1.5μm, 2.1μm, 2.4μm, 2.5μm, etc., or any range of two values. This embodiment does not make specific limitations here. It is worth noting that, since the carrier surface is used to connect the functional layer, the surface roughness Rz directly affects the peel force and adhesive strength between the carrier metal foil 1 and the functional layer. By limiting the surface roughness Rz to the above range, on the one hand, it can avoid the surface roughness Rz being too small, which would result in insufficient adhesive strength between the carrier metal foil 1 and the functional layer after the functional layer is bonded to the carrier metal foil 1, thus preventing the functional layer from easily detaching from the carrier metal foil 1. On the other hand, it can avoid the surface roughness Rz being too large, which would result in excessive peel force between the carrier metal foil 1 and the functional layer, making it difficult to peel the carrier metal foil 1 from the functional layer after it is pressed onto the circuit board substrate, leading to damage to the functional layer or partial residue of the carrier metal foil 1 on the functional layer.

[0035] As a preferred embodiment, the material of the carrier metal foil 1 includes at least one of nickel, chromium, copper, silver, gold, zinc and aluminum.

[0036] Specifically, the carrier metal foil 1 in this embodiment can be made of nickel, chromium, copper, silver, gold, zinc, or aluminum, or it can be an alloy material composed of two or more of nickel, chromium, copper, silver, gold, zinc, and aluminum. This embodiment does not impose any specific limitations. Preferably, the carrier metal foil 1 is made of copper.

[0037] As a preferred embodiment, an antioxidant layer 3 is provided on at least one side surface of the carrier metal foil 1.

[0038] Specifically, this embodiment considers that in the application of composite metal foil with carrier metal foil 1, the outer surface of carrier metal foil 1 is exposed to the air environment and is easily contaminated by moisture, dust, and other objects in the air, leading to oxidation and a significantly shortened storage time. Furthermore, severe oxidation of the carrier metal foil 1 also greatly increases the oxidation probability of the functional layer it supports. In addition, due to the oxidation of the carrier metal foil 1, oxidized powder falls off its surface during the peeling process, increasing the amount of airborne dust and other contaminants during peeling, and consequently increasing the adsorption of these contaminants on the surface of the peeled functional layer. Moreover, if the outer surface of the carrier metal foil 1 is severely oxidized, it will be difficult to provide adequate protection for the functional layer, or the functional layer may easily detach automatically. Furthermore, during the pressing process, oxidized points may detach and adhere to the surface of the press plate, contaminating the press and affecting subsequent pressing processes. Therefore, in this embodiment, by providing an anti-oxidation layer 3 on at least one side surface of the carrier metal foil 1, the outer surface of the carrier metal foil 1 is not easily contaminated by moisture, dust and other objects in the air, and can maintain a relatively dry and clean surface state. At the same time, it is not easily oxidized, which can ensure the normal storage and use of the composite metal foil with the carrier metal foil 1 in this embodiment, and is beneficial to extending the storage time.

[0039] It is understood that, in this embodiment, the antioxidant layer 3 may be disposed only on one side of the surface of the carrier metal foil 1, such as... Figure 2 As shown, it can also be disposed on opposite sides of the metal foil 1 used as a carrier, such as... Figure 3 As shown, this embodiment is not specifically limited here.

[0040] As a preferred embodiment, the material of the antioxidant layer 3 includes at least one of nickel, chromium, copper, silver, gold, zinc, titanium, and aluminum.

[0041] Specifically, the material of the antioxidant layer 3 in this embodiment can be nickel, chromium, copper, silver, gold, zinc, titanium or aluminum, or it can be an alloy material composed of two or more of nickel, chromium, copper, silver, gold, zinc, titanium and aluminum. This embodiment does not make specific limitations. By using metal materials to form the antioxidant layer 3, a dense, continuous and chemically stable metal oxide film can be quickly formed on the surface of the carrier metal foil 1. The oxide film will adhere tightly to the surface of the foil, thereby isolating the contact between air, water vapor, acid and alkali and other corrosive media and the substrate of the carrier metal foil 1, and preventing the substrate metal from being oxidized to form loose oxides from the source.

[0042] A second aspect of the present invention provides a composite metal foil, the composite metal foil comprising a carrier metal foil as described in any embodiment of the first aspect.

[0043] It is understood that the composite metal foil in this embodiment may be composed of a carrier metal foil and a thin metal foil as a functional layer stacked together, or it may be composed of a carrier metal foil, a release layer and a thin metal foil as a functional layer stacked together in sequence.

[0044] A third aspect of the present invention provides a circuit board, the circuit board comprising a circuit board substrate and a composite metal foil as described in the second aspect, which is pressed onto the circuit board substrate.

[0045] The carrier metal foil, composite metal foil, and circuit board provided in the embodiments of the present invention have at least the following beneficial effects: (1) Since columnar crystals with (220) texture have the intrinsic property of high thermal stability, by limiting the thickness of the carrier metal foil to 6μm~20μm and the extreme density of columnar crystals with (220) texture in the carrier metal foil to be greater than or equal to 0.7, preferential orientation can be achieved in the carrier metal foil. Since columnar crystals with (220) texture have the intrinsic property of thermal stability, the thermal stability of the carrier metal foil is significantly improved. In the circuit board manufacturing process, the coefficient of thermal expansion can be kept relatively stable, thereby effectively avoiding warping of the circuit board substrate and improving the yield.

[0046] (2) By limiting the extreme density of columnar crystals with (111) texture to less than or equal to 2.39, it can be ensured that the extreme density of columnar crystals with (111) texture will not be too high, that is, the proportion of columnar crystals with (111) texture will not be too high, and it works in synergy with the extreme density of columnar crystals with (220) texture to avoid the problem of high and large fluctuation of thermal expansion coefficient in the circuit board manufacturing process, thereby effectively avoiding the warping of the circuit board substrate.

[0047] (3) By limiting the extreme density of columnar crystals with (200) texture to less than or equal to 1.97, it can be ensured that the extreme density of columnar crystals with (200) texture is not too high, that is, the proportion of columnar crystals with (200) texture is not too high, reducing its negative impact on the CTE of the carrier metal foil. In addition, the extreme density of columnar crystals with (220) texture works synergistically to make the carrier metal foil have higher thermal stability or lower CTE change rate, and can ensure that the coefficient of thermal expansion is relatively stable in the circuit board manufacturing process, which can further avoid the warping of the circuit board substrate and improve the yield.

[0048] (4) By limiting the grain size of columnar crystals to 0.01μm~20μm, it is possible to avoid the grain size of columnar crystals being too small and easily causing changes in grain morphology, thereby avoiding CTE instability. At the same time, it is possible to avoid the grain size of columnar crystals being too large and affecting the roughness Rz of the metal foil used as a carrier.

[0049] To fully demonstrate the beneficial effects of the carrier metal foil provided in the embodiments of the present invention, the following description is provided in conjunction with specific embodiments and comparative examples.

[0050] Example 1 A carrier metal foil, wherein the carrier metal foil is a copper foil, the thickness of the carrier metal foil is 18 μm, the carrier metal foil contains columnar crystals, and the extreme density of the columnar crystals with (220) texture is 0.7, the grain size of the columnar crystals is 0.2 μm to 14 μm, and a zinc-nickel anti-oxidation layer is provided on the non-carrier surface of the carrier metal foil.

[0051] Example 2 A carrier metal foil, wherein the carrier metal foil is a copper foil, the thickness of the carrier metal foil is 18 μm, the carrier metal foil contains columnar crystals, and the extreme density of columnar crystals with (220) texture is 0.7, the extreme density of columnar crystals with (111) texture is 2.27, the grain size of the columnar crystals is 0.2 μm to 14 μm, and a zinc-nickel anti-oxidation layer is provided on the non-carrier surface of the carrier metal foil.

[0052] Example 3 A carrier metal foil, wherein the carrier metal foil is a copper foil, the thickness of the carrier metal foil is 18 μm, the carrier metal foil contains columnar crystals, and the extreme density of columnar crystals with (220) texture is 0.7, the extreme density of columnar crystals with (111) texture is 2.30, the extreme density of columnar crystals with (200) texture is 1.92, the grain size of the columnar crystals is 0.2 μm to 14 μm, and a zinc-nickel anti-oxidation layer is provided on the non-carrier surface of the carrier metal foil.

[0053] Example 4 A carrier metal foil, wherein the carrier metal foil is a copper foil, the thickness of the carrier metal foil is 18 μm, the carrier metal foil contains columnar crystals, and the extreme density of columnar crystals with (220) texture is 0.9, the extreme density of columnar crystals with (111) texture is 1.98, the extreme density of columnar crystals with (200) texture is 1.87, the grain size of the columnar crystals is 0.2 μm to 14 μm, and a zinc-nickel anti-oxidation layer is provided on the non-carrier surface of the carrier metal foil.

[0054] Comparative Example 1 A metal foil for a carrier, the metal foil for the carrier being a copper foil, the thickness of the metal foil for the carrier being 18 μm, the metal foil for the carrier containing columnar crystals, and the pole density of the columnar crystals having a (220) texture being 0.4, the pole density of the columnar crystals having a (111) texture being 2.57, the pole density of the columnar crystals having a (200) texture being 2.13, the grain size of the columnar crystals being 0.2 μm to 10 μm, and a zinc-nickel antioxidant layer being provided on the non-carrier surface of the metal foil for the carrier.

[0055] The metal foil for the carrier in the above embodiments and comparative examples is laminated with the same thin copper foil layer by layer to form a composite metal foil, and then the same lamination process (laminating for 2 hours under the conditions of a temperature of 210 °C and a pressure of 25 kg / cm 2 ) is used to laminate the composite metal foil on the same P sheet or prepreg, and it is observed whether the circuit board substrate warps and the warping height is measured with a ruler. The CTE of the metal foil for the carrier in the embodiments and comparative examples in this process is measured and the CTE change rate is calculated. The calculation method of the CTE change rate is [(CTE 高 -CTE 低 ) × 100%] / CTE 低 , where CTE is the test value under the condition of a temperature of 120 °C - 300 °C, CTE 高 is the highest CTE value, CTE 低 is the lowest CTE value, the heating rate is 10 °C / min, the sampling direction of the sample is the MD direction of the metal foil for the carrier (i.e., the machine production direction of the copper foil). In addition, if the CTE change rate value is less than or equal to 50%, it is qualified, and if the CTE change rate value is greater than 50%, it is unqualified. The test results of multiple test samples are statistically shown in Table 1 below: Table 1 Test Results of Metal Foil for Carrier

[0056] As can be seen from Table 1, since the thickness of the metal foil for the carrier in Embodiments 1 to 4 above satisfies 6 μm to 20 μm, the metal foil for the carrier all contains columnar crystals, and the pole density of the columnar crystals having a (220) texture all satisfies greater than or equal to 0.7. Since the columnar crystals having a (220) texture have the intrinsic property of thermal stability, the thermal stability of the metal foil for the carrier is significantly improved. During the lamination test, the CTE change rates of the metal foils for the carrier in Embodiments 1 to 4 all satisfy less than or equal to 50%, that is, the coefficient of thermal expansion is relatively stable, thereby ensuring that the warping height of the circuit board substrate is small and effectively avoiding the warping of the circuit board substrate.

[0057] In Comparative Example 1, the extreme density of columnar crystals with (220) texture in the carrier metal foil is too small, while the extreme density of columnar crystals with (111) texture and columnar crystals with (200) texture is too large. This results in poor thermal stability of the carrier metal foil. During the pressing test, its CTE change rate is greater than 50%, that is, the change in the coefficient of thermal expansion is large. This leads to excessive warpage height of the circuit board substrate, which exceeds 4mm, that is, the circuit board substrate shows obvious warpage.

[0058] The above description represents the preferred embodiments of the present invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of the present invention, and these improvements and modifications are also considered to be within the scope of protection of the present invention.

Claims

1. A metal foil for a carrier, characterized in that, The thickness of the carrier metal foil is 6μm~20μm, the carrier metal foil contains columnar crystals, and the extreme density of the columnar crystals with (220) texture is greater than or equal to 0.

7.

2. The carrier metal foil as described in claim 1, characterized in that, In the carrier metal foil, the extreme density of columnar crystals with (111) texture is less than or equal to 2.

39.

3. The carrier metal foil as described in claim 1, characterized in that, In the carrier metal foil, the extreme density of columnar crystals with (200) texture is less than or equal to 1.

97.

4. The carrier metal foil as described in claim 1, characterized in that, The grain size of the columnar crystals is 0.01μm to 20μm.

5. The carrier metal foil as described in claim 1, characterized in that, The roughness Rz of the carrier surface of the carrier metal foil is 0.4μm~2.5μm; wherein, the carrier surface is the surface used to connect the functional layer.

6. The carrier metal foil as described in claim 1, characterized in that, The material of the carrier metal foil includes at least one of nickel, chromium, copper, silver, gold, zinc, and aluminum.

7. The carrier metal foil as described in claim 1, characterized in that, An antioxidant layer is provided on at least one side surface of the metal foil used as the carrier.

8. The carrier metal foil as described in claim 7, characterized in that, The material of the antioxidant layer includes at least one of nickel, chromium, copper, silver, gold, zinc, iron, titanium and aluminum.

9. A composite metal foil, characterized in that, The composite metal foil includes a carrier metal foil as described in any one of claims 1 to 8.

10. A circuit board, characterized in that, The circuit board includes a circuit board substrate and a composite metal foil as described in claim 9, which is pressed onto the circuit board substrate.

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