Composite metal foil and metal-clad laminate

Abstract

The invention discloses a composite metal foil and a metal-clad laminated plate, the composite metal foil comprises a substrate layer and a functional layer, the functional layer is laminated on one side of the substrate layer, the functional layer comprises a first resistance layer and a second resistance layer, the first resistance layer is arranged on one side of the substrate layer, and the second resistance layer is arranged on the other side of the substrate layer. The second resistance layer is arranged on one side, far away from the substrate layer, of the first resistance layer; wherein the density of the first resistive layer is greater than that of the second resistive layer. The functional layer is arranged on the substrate layer and comprises the first resistance layer and the second resistance layer which are different in density, and the density of the first resistance layer close to one side of the substrate layer is larger than that of the second resistance layer far away from the substrate layer, so that the compactness of the first resistance layer is better than that of the second resistance layer; compared with the first resistance layer, the second resistance layer is easier to etch, so that the line width of the upper bottom of the functional layer is obviously smaller than the line width of the lower bottom of the functional layer due to the difference of the exchange rate of etching liquid medicine in the thickness direction of the functional layer, the burr effect is effectively improved, and the precision of the resistance value and the reliability of the line quality are improved.

Description

Technical Field

[0001] The present invention relates to the technical field of electronic information materials, and in particular to a composite metal foil and a metal-clad laminate. Background Art

[0002] With the development of miniaturization, lightness, thinness and high integration of electronic devices, the internal resistance elements have gradually developed towards lightness and thinness, from traditional pin-connected resistors to surface-mounted resistors and then to embedded resistors. The use process of the embedded resistor is roughly as follows: a composite metal foil is attached to a circuit board, and an embedded resistor is etched through an etching process.

[0003] The commonly used composite metal foil for existing circuit boards includes a base layer and a resistor layer with uniform density that are stacked in sequence. The side of the resistor layer away from the base layer is pressed against the circuit board, and an etched circuit is made to achieve the effect of embedding the resistor in the circuit board. However, the inventor found during the implementation of this existing technology that there are the following technical problems in the existing technology: during the etching process, due to the difference in the etching solution exchange rate along the thickness direction of the resistor layer, the line width of the upper bottom of the resistor layer is significantly smaller than the line width of the lower bottom, resulting in serious burr residues, causing a difference between the resistor and the actual design and affecting the reliability of the circuit quality. To solve the above problems, it is urgently necessary to develop a composite metal foil and a metal-clad laminate with small etched circuit burrs, accurate resistance values and high circuit quality reliability. Summary of the Invention

[0004] An object of an embodiment of the present invention is to provide a composite metal foil that can reduce circuit burrs, improve the accuracy of resistance values and the reliability of circuit quality during etching.

[0005] To achieve the above object, an embodiment of the present invention provides a composite metal foil, including a base layer and a functional layer. The functional layer is laminated on one side of the base layer, and the functional layer includes a first resistor layer and a second resistor layer. The first resistor layer is disposed on one side of the base layer, and the second resistor layer is disposed on the side of the first resistor layer away from the base layer;

[0006] Wherein, the density of the first resistor layer is greater than the density of the second resistor layer.

[0007] As an improvement of the above solution, the density of the first resistor layer is more than 1.5 times the density of the second resistor layer.

[0008] As an improvement of the above solution, the density of the first resistor layer is 1.5 to 3 times the density of the second resistor layer.

[0009] As an improvement of the above solution, an intermediate resistor layer is further provided between the first resistor layer and the second resistor layer.

[0010] As an improvement of the above solution, the densities of the first resistance layer, the intermediate resistance layer, and the second resistance layer gradually decrease.

[0011] As an improvement of the above solution, the thickness of the first resistance layer is greater than or equal to the thickness of the second resistance layer.

[0012] As an improvement of the above solution, the functional layer includes at least one element of Ni, Co, Mo, Cr, Mg, Fe, Sn, Ti, Sn, and C; or the functional layer includes at least one element of Ni, Co, Mo, Cr, Mg, Fe, Sn, Ti, Sn, C and at least one element of P, Si, O, and N.

[0013] As an improvement of the above solution, the thickness of the base layer is 2 μm to 70 μm.

[0014] As an improvement of the above solution, the antioxidant layer is laminated on one side of the base layer away from the functional layer.

[0015] To achieve the above object, an embodiment of the present invention further provides a metal-clad laminate, and the metal-clad laminate includes the composite metal foil described in any one of the above embodiments.

[0016] Compared with the prior art, the beneficial effect of the embodiment of the present invention is that by providing a functional layer on the base layer, the functional layer includes a first resistance layer and a second resistance layer with different densities, and the density of the first resistance layer closer to the base layer is greater than that of the second resistance layer away from the base layer, so that the compactness of the first resistance layer is better than that of the second resistance layer. Compared with the first resistance layer, the second resistance layer is easier to etch. Therefore, it is possible to avoid the line width of the upper bottom of the functional layer being significantly smaller than the line width of the lower bottom due to the difference in the etching solution exchange rate along the thickness direction of the functional layer, resulting in serious burr residues, effectively improving the burr effect, and improving the accuracy of the resistance value and the reliability of the circuit quality. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 is a schematic structural diagram of a first composite metal foil provided by an embodiment of the present invention;

[0018] Figure 2 is a schematic structural diagram of a second composite metal foil provided by an embodiment of the present invention;

[0019] Wherein, 1, base layer; 2, functional layer; 21, first resistance layer; 22, second resistance layer; 23, intermediate resistance layer; 3, antioxidant layer. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0020] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0021] In the description of the specification and the claims, it should be understood that the orientation or positional relationship indicated by the terms "upper", "lower", "left", "right", "front", "rear", "top", "bottom", "inner", "outer", etc. is based on the orientation or positional relationship shown in the accompanying drawings, and is only for the convenience of describing the embodiments of the present invention, rather than indicating or implying that the device or component referred to must have a specific orientation, be constructed and operated in a specific orientation, and thus cannot be understood as a limitation to the embodiments of the present invention.

[0022] In addition, the terms first, second, etc. in the specification and the claims are only used for the purpose of distinguishing the description of the same technical features, and cannot be understood as indicating or implying relative importance or implicitly indicating the quantity of the indicated technical features, nor necessarily describing the order or time sequence. The terms can be interchanged under appropriate circumstances. Thus, the features defined with "first" and "second" may explicitly or implicitly include at least one of the features.

[0023] Please refer to Figure 1 , Figure 1 which is a schematic structural diagram of a composite metal foil according to an embodiment of the present invention. The embodiment of the present invention provides a composite metal foil, which includes: a base layer 1 and a functional layer 2. The functional layer 2 is laminated on one side of the base layer 1, and the functional layer 2 includes a first resistance layer 21 and a second resistance layer 22. The first resistance layer 21 is disposed on one side of the base layer 1, and the second resistance layer 22 is disposed on the side of the first resistance layer 21 away from the base layer 1;

[0024] Among them, the density of the first resistance layer 21 is greater than the density of the second resistance layer 22.

[0025] It is worth noting that in practical applications, for example, when applied in the field of circuit boards, the functional layer 2 of the composite metal foil is laminated with the substrate of the circuit board. First, the circuit is made by acid etching, and then the base layer 1 is etched by alkaline etching to form the required circuit; for example, when applied in the field of electronic material production, the functional layer 2 of the composite metal foil is laminated on the composite material to make a flexible copper clad laminate.

[0026] In the embodiment of the present invention, the base layer 1 functions as a conductor and is used to fabricate circuits. It is formed by etching. Further, the material of the base layer 1 includes at least one of the following metal elements: nickel, aluminum, titanium, zinc, iron, copper. For example, in buried resistive copper foil, the material of the base layer 1 is usually copper.

[0027] Preferably, the surface roughness Rz of the side of the functional layer 2 away from the base layer 1 satisfies the relational expression: 2μm ≤ Rz ≤ 4μm

[0028] It should be noted that in the embodiment of the present invention, by defining the surface roughness Rz of the side of the functional layer 2 away from the base layer 1 and satisfying 2μm ≤ Rz ≤ 4μm, the roughness of the side of the functional layer 2 away from the base layer 1 is moderate. There will be no situation where the surface roughness Rz of the functional layer 2 is too small, resulting in too weak bonding force between the side of the functional layer 2 away from the base layer 1 in the composite metal foil and the substrate of the circuit board, causing delamination and detachment, and making the circuit board unable to be processed and used normally. At the same time, there will also be no situation where the surface roughness Rz of the side of the functional layer 2 away from the base layer 1 is too large, resulting in the rough surface of the side of the functional layer 2 away from the base layer 1 in the composite metal foil piercing into the substrate of the circuit board, thus making it difficult to etch the resistive layer on the side of the functional layer 2 away from the base layer 1 cleanly, resulting in serious burr problems, causing resistance size deviation, inaccurate resistance value, deviation from the design value, and serious decline in the quality reliability of the entire circuit. Therefore, by defining the surface roughness Rz of the side of the functional layer 2 away from the base layer 1 as 2μm ≤ Rz ≤ 4μm, the etching burr problem can be better controlled. At the same time, there will be no situation of too weak bonding force with the substrate of the circuit board and delamination and detachment. Optionally, the surface roughness Rz of the side of the functional layer 2 away from the base layer 1 can be any value among 2μm, 2.5μm, 3μm, 3.5μm, 4μm or any interval composed of any two of these values.

[0029] In the embodiments of the present invention, the functional layer 2 functions to control the resistance. In the application of a circuit board, the functional layer 2 of the composite metal foil is laminated with the substrate of the circuit board. First, the circuit is fabricated by acid etching, and then the base layer 1 is etched by alkaline etching to form a preset resistance size and resistance value. In the prior art, the functional layer 2 is a single resistance layer. During etching, along the thickness direction of the functional layer 2, the closer the functional layer 2 is to the circuit board substrate, the slower the etching rate due to the slow exchange rate of the etching solution, resulting in incomplete etching, serious burrs, deviation in the resistance size, inaccurate resistance value, deviation from the design value, and a significant decrease in the reliability of the entire circuit quality. Therefore, to solve the above problems of burrs and circuit quality reliability, in the embodiments of the present invention, the functional layer 2 includes a first resistance layer 21 and a second resistance layer 22 made of the same material but with different densities. The density of the first resistance layer 21 closer to the base layer 1 is greater than that of the second resistance layer 22 away from the base layer, such that the compactness of the first resistance layer 21 is better than that of the second resistance layer 22. Compared with the first resistance layer 21, the second resistance layer 22 has a loose structure and is easier to etch. Therefore, it is possible to avoid the situation where the line width of the upper base of the functional layer 2 is significantly smaller than the line width of the lower base along the thickness direction due to the difference in the etching solution exchange rate, resulting in serious burr residues, effectively improving the burr effect, and improving the accuracy of the resistance value and the reliability of the circuit quality.

[0030] Specifically, in the embodiments of the present invention, the manufacturing method of the functional layer 2 includes one or a combination of production methods such as sputtering, evaporation plating, electroplating, and electroless plating, and is formed by layer-by-layer stacking on the base layer. Preferably, both the first resistance layer and the second resistance layer are formed by sputtering, evaporation plating, or a combination of sputtering and electroplating or electroless plating. Sputtering and evaporation plating are physical methods with simple processes and easy control of the density of each layer; when combined with other methods, it is easy to control the density of each layer to meet the density difference between the first resistance layer 21 and the second resistance layer 22.

[0031] In the composite metal foil provided by the embodiments of the present invention, by setting the first resistance layer 21 and the second resistance layer 22 with different densities and optimizing the density sizes of the first resistance layer 21 and the second resistance layer 22, the etching rate uniformity of the functional layer 2 can be controlled, which can reduce circuit burrs and improve the accuracy of the resistance value and the reliability of the circuit quality.

[0032] As a preferred solution, the density of the first resistance layer 21 is more than 1.5 times the density of the second resistance layer.

[0033] In an embodiment of the present invention, the density difference between the first resistance layer 21 and the second resistance layer 22 included in the functional layer 2 is further optimized. Among them, the density of the first resistance layer 21 is more than 1.5 times the density of the second resistance layer. Exemplarily, the density of the first resistance layer 21 is 2 times, 2.5 times, 3 times, 3.5 times, 4 times, 4.5 times, 5 times, 5.5 times, 6 times, etc. of the density of the second resistance layer. This embodiment does not make specific limitations on this. It can be understood that if the multiple of the density of the first resistance layer 21 to the density of the second resistance layer 22 is less than 1.5, the compactness of the first resistance layer 21 is not much different from that of the second resistance layer 22, that is to say, the looseness of the first resistance layer 21 is equivalent to that of the second resistance layer 22, and it is impossible to solve the problem that the closer the functional layer 2 is to the circuit board substrate along the thickness direction of the functional layer 2, the slower the etching speed due to the slow exchange speed of the etching solution, and then the etching is not clean, resulting in serious burrs, causing resistance size deviation, inaccurate resistance value, deviation from the design value, and serious decline in the reliability of the entire circuit quality. Or, it will be found that the compactness of the first resistance layer 21 is worse than that of the second resistance layer 22, that is to say, the first resistance layer 21 is more loose than the second resistance layer 22 and is easier to etch, resulting in more serious etching burr phenomenon and serious decline in the reliability of the entire circuit quality. Therefore, in the embodiment of the present invention, the multiple of the density of the first resistance layer 21 to the density of the second resistance layer 22 is limited to more than 1.5 times, which can better control the etching burr problem and improve the reliability of the circuit quality. Preferably, the density of the first resistance layer 21 is 1.5 times to 3 times the density of the second resistance layer 22. In an embodiment of the present invention, the density difference between the first resistance layer 21 and the second resistance layer 22 is further optimized. Within this multiple range, the burr effect formed by etching the composite metal foil is better. It will not be unable to avoid the etching burr problem caused by the etching solution exchange speed due to the small density difference between the first resistance layer 21 and the second resistance layer 22. At the same time, it will not increase the manufacturing process difficulty and cost of the composite metal foil, as well as increase the difficulty of adjusting the etching process due to the too large density difference between the first resistance layer 21 and the second resistance layer 22.

[0034] It should be noted that the multiple described in the present invention refers to the ratio of the two. Exemplarily, the multiple of the density of the first resistance layer 21 to the density of the second resistance layer in the embodiment of the present invention is limited to more than 1.5 times, which means that the ratio of the density of the first resistance layer 21 to the density of the second resistance layer is more than 1.5. This explanation will not be repeated below.

[0035] Please refer to Figure 2 , Figure 2 which is a schematic structural diagram of another composite metal foil according to an embodiment of the present invention. The composite metal foil further includes an intermediate resistance layer 23, and the intermediate resistance layer 23 is disposed between the first resistance layer 21 and the second resistance layer 22.

[0036] In the embodiment of the present invention, the intermediate resistance layer 23 functions to adjust the etching rate of the functional layer 2. The intermediate resistance layer 23 has at least one layer, and no specific limitation is made herein in this embodiment. It can be understood that if the density difference between the first resistance layer 21 and the second resistance layer 22 is too large, it is easy to occur that the second resistance layer 22 is etched rapidly, resulting in etching at the bottom of the circuit, weakening the bonding force between the circuit and the substrate, and further resulting in the phenomenon of circuit detachment. If the density difference between the first resistance layer 21 and the second resistance layer 22 is too small, and thus the etching rate difference between the first resistance layer 21 and the second resistance layer 22 is small, although the circuit burr becomes smaller, the effect is not significant and the quality reliability of the circuit board cannot be improved. Therefore, in the embodiment of the present invention, at least one intermediate resistance layer 23 is provided between the first resistance layer 21 and the second resistance layer 22, which can adjust the etching rates of the first resistance layer 21 and the second resistance layer 22, so that the circuit burr can be further controlled.

[0037] Preferably, the densities of the first resistance layer 21, the intermediate resistance layer 23, and the second resistance layer 22 gradually decrease.

[0038] It is worth noting that in the embodiment of the present invention, the relationship between the densities of the first resistance layer 21, the intermediate resistance layer 23, and the second resistance layer 22 is further optimized. The inventor found during the implementation of the embodiment of the present invention that when the densities of the first resistance layer 21, the intermediate resistance layer 23, and the second resistance layer 22 gradually decrease, the effect of etching the functional layer 2 gently and stably can be controlled. While ensuring the bonding force of the circuit, the circuit burr can be controlled to the minimum value, or even without burr, achieving the effect of accurately controlling the resistance value and improving the quality reliability of the circuit.

[0039] As a preferred solution, the thickness of the first resistance layer 21 is greater than or equal to the thickness of the second resistance layer 22.

[0040] In the embodiment of the present invention, by defining that the thickness of the first resistance layer 21 is greater than or equal to that of the second resistance layer 22, the difference in the difficulty of etching rates between the first resistance layer 21 and the second resistance layer 22 is further strengthened, and smaller burrs can be further achieved. It can be understood that when the thickness of the first resistance layer 21 is greater than or equal to that of the second resistance layer 22, the etching rate of the second resistance layer 22 will relatively increase, which can avoid the line width of the upper bottom of the functional layer 2 being significantly smaller than the line width of the lower bottom due to the difference in the etching solution exchange rate along the thickness direction of the functional layer 2, resulting in serious burr residue, effectively improving the burr effect, and improving the accuracy of the resistance value and the quality reliability of the circuit.

[0041] As a preferred solution, the functional layer 2 comprises at least one element of Ni, Co, Mo, Cr, Mg, Fe, Sn, Ti, Sn and C; or the functional layer 2 comprises at least one element of Ni, Co, Mo, Cr, Mg, Fe, Sn, Ti, Sn, C and at least one element of P, Si, O, N.

[0042] It should be noted that the material of the functional layer 2 directly determines the resistance value and the etching effect. The functional layer 2 defined in the embodiments of the present invention has excellent resistance characteristics and etching stability, and can accurately control the resistance.

[0043] Preferably, the functional layer 2 comprises Ni and P. It should be noted that in the embodiments of the present invention, the functional layer 2 comprises Ni and P. Ni is a conductor and P is a non-conductor. By adjusting the ratio of Ni and P, functional layers 2 with different resistance values can be obtained. At the same time, the functional layer 2 has excellent etching uniformity and can cover a wider application range.

[0044] As a preferred solution, the thickness of the base layer 1 is 2 μm to 70 μm.

[0045] In the embodiments of the present invention, the base layer 1 functions as a conductor and is used for making circuits. By setting the thickness of the base layer 1 to 2 μm to 70 μm, it will not occur that the circuit has poor conductivity and pinholes due to the too thin base layer 1, which affects the conduction function of the circuit; at the same time, it will not occur that the circuit is too hard and the bending property becomes poor due to the too thin base layer 1, which affects the assembly of the circuit board. Therefore, setting the thickness of the base layer 1 to 2 μm to 70 μm can not only ensure the conduction function of the circuit, but also prevent abnormal phenomena such as springback and circuit breakage during the assembly of the circuit board, and ensure the quality reliability and processing stability of the circuit.

[0046] Combined Figure 1 and Figure 2 As shown, in order to better protect the composite metal foil, an antioxidant layer 3 is further laminated on the side of the base layer 1 away from the functional layer 2 in this embodiment, which is used to prevent the composite metal foil from undergoing an oxidation reaction and affecting the quality before lamination. It can be understood that if the antioxidant layer 3 is not included, the side of the base layer 1 away from the functional layer 2 is prone to oxidation under conditions such as temperature, water vapor, and corrosive gases, resulting in abnormal circuit processing; therefore, in the embodiments of the present invention, the antioxidant layer 3 is provided on the side of the base layer 1 away from the functional layer 2, which can prevent substances such as temperature, water vapor, and corrosive gases from undergoing an oxidation reaction with the side of the base layer 1 away from the functional layer 2, thereby protecting the composite metal foil and improving the quality performance.

[0047] Specifically, the type of the antioxidant layer 3 is not limited by the material of the functional layer 2, and the antioxidant layer 3 is selected from at least one of an organic antioxidant layer, an inorganic antioxidant layer, and a metal antioxidant layer.

[0048] In a second aspect of the embodiments of the present invention, a metal-clad laminate is provided, and the metal-clad laminate includes the composite metal foil according to any one of the first aspect.

[0049] For the composite metal foil and the metal-clad laminate provided by the embodiments of the present invention, the beneficial effects are as follows: By providing the functional layer 2 on the base layer 1, the functional layer 2 includes a first resistance layer 21 and a second resistance layer 22 with different densities. The density of the first resistance layer 21 on the side close to the base layer 1 is greater than that of the second resistance layer 22 far from the base layer 1, so that the compactness of the first resistance layer 21 is better than that of the second resistance layer 22. Compared with the first resistance layer 21, the structure of the second resistance layer 22 is more porous and easier to etch. Therefore, it is possible to avoid the line width of the upper bottom of the functional layer being significantly smaller than the line width of the lower bottom due to the difference in the etching solution exchange rate along the thickness direction of the functional layer, resulting in serious burr residues, effectively improving the burr effect, and improving the accuracy of the resistance value and the reliability of the circuit quality.

[0050] In order to reflect the beneficial effects of a composite metal foil and a metal-clad laminate provided by the embodiments of the present invention, several embodiments and comparative examples will be described below.

[0051] Example 1:

[0052] A composite metal foil includes a base layer 1 and a functional layer 2. The functional layer 2 is laminated on one side of the base layer 1, and the functional layer includes a first resistance layer 21 and a second resistance layer 22. The first resistance layer 21 is disposed on one side of the base layer 1, and the second resistance layer 22 is disposed on the side of the first resistance layer 21 away from the base layer 1; both the first resistance layer 21 and the second resistance layer 22 are alloys of Ni and P; the thickness of the first resistance layer 21 is 80 nm, the thickness of the second resistance layer is 20 nm, and the density of the first resistance layer 21 is 7.5 g / cm 3 , and the density of the second resistance layer 22 is 5 g / cm 3 . The composite metal foil is laminated on a circuit board substrate, and according to the circuit design, it is sequentially subjected to acid etching and alkaline etching, and burr observation is carried out.

[0053] Example 2:

[0054] The structure of the composite metal foil in this example is the same as that in Example 1, except that: the density of the first resistance layer 21 is 7.5 g / cm 3 , and the density of the second resistance layer 22 is 3.7 g / cm 3Press the composite metal foil onto the circuit board substrate. According to the circuit design, successively perform acid etching and alkaline etching, and observe the burrs.

[0055] Example 3:

[0056] The structure of the composite metal foil in this example is the same as that in Example 1, except that: the density of the first resistance layer 21 is 7.5 g / cm 3 , and the density of the second resistance layer 22 is 2.5 g / cm 3 Press the composite metal foil onto the circuit board substrate. According to the circuit design, successively perform acid etching and alkaline etching, and observe the burrs.

[0057] Example 4:

[0058] The structure of the composite metal foil in this example is the same as that in Example 1, except that: the density of the first resistance layer 21 is 7.5 g / cm 3 , and the density of the second resistance layer 22 is 2 g / cm 3 Press the composite metal foil onto the circuit board substrate. According to the circuit design, successively perform acid etching and alkaline etching, and observe the burrs.

[0059] Example 5:

[0060] The structure of the composite metal foil in this example is the same as that in Example 1, except that: the density of the first resistance layer 21 is 7.5 g / cm 3 , and the density of the second resistance layer 22 is 1 g / cm 3 Press the composite metal foil onto the circuit board substrate. According to the circuit design, successively perform acid etching and alkaline etching, and observe the burrs.

[0061] Example 6:

[0062] The structure of the composite metal foil in this example is the same as that in Example 1, except that: the thickness of the first resistance layer 21 is 80 nm, and the thickness of the second resistance layer 22 is 50 nm. Press the composite metal foil onto the circuit board substrate. According to the circuit design, successively perform acid etching and alkaline etching, and observe the burrs.

[0063] Comparative Example 1:

[0064] A composite metal foil includes a base layer 1 and a functional layer 2. The functional layer 2 is laminated on one side of the base layer 1, and the functional layer includes a single resistance layer, and the resistance layer is an alloy of Ni and P; the density of the resistance layer is 7.5 g / cm 3 , and the thickness of the resistance layer is 80 nm. Press the composite metal foil onto the circuit board substrate. According to the circuit design, successively perform acid etching and alkaline etching, and observe the burrs.

[0065] Comparative Example 2:

[0066] The composite metal foil structure of this comparative example is the same as that of Comparative Example 1, except that the thickness of the resistance layer is 100 nm. The composite metal foil is laminated on the circuit board substrate, and according to the circuit design, it is successively subjected to acid etching and alkaline etching, and the burrs are observed.

[0067] Comparative Example 3:

[0068] The composite metal foil structure of this comparative example is the same as that of Comparative Example 1, except that the thickness of the resistance layer is 130 nm. The composite metal foil is laminated on the circuit board substrate, and according to the circuit design, it is successively subjected to acid etching and alkaline etching, and the burrs are observed.

[0069] As shown in Table 1 below, the etching burr conditions of the composite metal foils of the above-mentioned Examples 1-6 and Comparative Examples 1-3 are shown (the industry standard for burrs ≤ 3 μm).

[0070] Table 1. Etching Burrs of Composite Metal Foils of Examples 1-6 and Comparative Examples 1-3

[0071]

[0072] It can be seen that by applying the composite metal foil of this example, the burr effect can be effectively improved, and the accuracy of the resistance value and the reliability of the circuit quality can be improved.

[0073] All in all, by providing the functional layer 2 on the base layer 1, the functional layer 2 includes a first resistance layer 21 and a second resistance layer 22 with different densities. The density of the first resistance layer 21 (7.5 g / cm 3 ) close to the base layer 1 is greater than that of the second resistance layer 22 (5 g / cm 3 , 3.7 g / cm 3 , 2.5 g / cm 3 , 2 g / cm 3 , 1 g / cm 3 ) far from the base layer 1, so that the compactness of the first resistance layer 21 is better than that of the second resistance layer 22. Compared with the first resistance layer 21, the structure of the second resistance layer 22 is more porous and easier to etch. Therefore, it is possible to avoid the line width of the upper bottom of the functional layer being significantly smaller than the line width of the lower bottom due to the difference in the etching solution exchange rate along the thickness direction of the functional layer, resulting in serious burr residues, effectively improving the burr effect, and improving the accuracy of the resistance value and the reliability of the circuit quality.

[0074] The above are the preferred embodiments of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and refinements can be made, and these improvements and refinements are also regarded as the protection scope of the present invention.

Claims

1. A composite metal foil, characterized in that, It includes a base layer and a functional layer. The functional layer is laminated on one side of the base layer, and the functional layer includes a first resistance layer and a second resistance layer. The first resistance layer is disposed on one side of the base layer, and the second resistance layer is disposed on the side of the first resistance layer away from the base layer; Among them, the density of the first resistance layer is greater than the density of the second resistance layer.

2. The composite metal foil according to claim 1, characterized in that, The density of the first resistance layer is more than 1.5 times the density of the second resistance layer.

3. The composite metal foil according to claim 2, wherein, The density of the first resistance layer is 1.5 to 3 times the density of the second resistance layer.

4. The composite metal foil according to claim 1, characterized in that, An intermediate resistance layer is also provided between the first resistance layer and the second resistance layer.

5. The composite metal foil according to claim 4, wherein, The densities of the first resistance layer, the intermediate resistance layer, and the second resistance layer gradually decrease.

6. The composite metal foil according to claim 1, wherein The thickness of the first resistance layer is greater than or equal to the thickness of the second resistance layer.

7. The composite metal foil according to claim 1, characterized in that, The functional layer includes at least one element among Ni, Co, Mo, Cr, Mg, Fe, Sn, Ti, Sn, and C; or the functional layer includes at least one element among Ni, Co, Mo, Cr, Mg, Fe, Sn, Ti, Sn, C and at least one element among P, Si, O, and N.

8. The composite metal foil according to claim 1, wherein The thickness of the base layer is 2 μm to 70 μm.

9. The metal foil according to any one of claims 1-8, characterized in that An antioxidant layer is laminated on the side of the base layer away from the functional layer.

10. A metal-clad laminate, characterized in that, The metal-coated laminate includes the composite metal foil according to any one of claims 1-9.

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