High-performance buried resistor copper foil and preparation method thereof

Abstract

The invention relates to the field of electrolytic copper foil processing and application, and discloses a high-performance buried resistance copper foil and a preparation method thereof, the buried resistance copper foil structurally comprises a conductive layer, an isolation layer and a resistance layer; the conductive layer is a substrate copper foil, the isolation layer is made of nickel-cobalt or nickel-tin alloy, and the resistance layer is made of nickel-phosphorus alloy. The resistivity of the product can be improved, the resistivity is larger than or equal to 2.0 * 10 <-3 > omega.cm, and the ESD performance is better; the resistance temperature coefficient is small, the resistance value drift after high-temperature pressing is small, and the front-back difference value can be controlled within 1%.

Description

Technical Field

[0001] The present invention relates to the field of electrolytic copper foil processing and application, and particularly to a high-performance buried resistance copper foil and a preparation method thereof. Background Art

[0002] With the rapid development of the electronic information industry and the continuous update of portable electronic products, printed circuit boards (PCBs), which support electronic components, are also developing towards high density, multi-layer, easy encapsulation, and miniaturization. To meet the requirements, some passive devices that occupy a large amount of the PCB surface need to be buried inside the PCB. On the surface of traditional PCB boards, a large number of resistor components are arranged, occupying a large amount of board surface space. At the same time, the vias and wires used to match the resistors will affect the decoupling effect of the signal transmission impedance, resulting in problems with the integrity of the transmission line signal. Therefore, considering the reliability of PCB assembly, the stability and electrical performance of resistor devices, the burial of resistor devices is very necessary, and the emergence of buried resistance copper foil has well solved this problem.

[0003] However, due to the requirements and influences of PCB processing processes, buried resistance copper foil needs to have excellent resistance stability and reliability. The key lies in: 1. How to reduce the square resistance difference value of the material and ensure the square resistance stability of itself; 2. How to reduce the resistance temperature coefficient of the material and ensure the resistance value stability before and after high-temperature pressing; 3. How to improve the etching resistance of the material and ensure the resistance value stability before and after circuit processing; 4. How to prepare buried resistance copper foil with high resistivity and ensure the antistatic ability of the product. However, the existing buried resistance copper foil has low resistivity, large resistance value difference, high resistance temperature coefficient, and serious resistance value drift after processing. Summary of the Invention

[0004] The main purpose of the present invention is to solve the technical problems in the prior art that the buried resistance copper foil has low resistivity, large resistance value difference, high resistance temperature coefficient, and serious resistance value drift after processing. A high-performance buried resistance copper foil, the structure of the buried resistance copper foil includes a conductive layer, an isolation layer, and a resistance layer; the conductive layer is a base copper foil, the isolation layer is nickel-cobalt or nickel-tin alloy, and the resistance layer is nickel-phosphorus alloy.

[0005] As a preferred technical solution, the thickness of the conductive layer is 4.5 - 130 μm, the thickness of the isolation layer is 10 - 100 nm, and the thickness of the resistance layer is 50 - 1000 nm.

[0006] As a preferred technical solution, the surface roughness Rz of the treated surface of the base copper foil is 0.4 - 10 μm, the surface density is 40 - 1200 g / m2; the tensile strength is 200 - 800 MPa, and the elongation is 1 - 20%.

[0007] As a preferred technical solution, the resistance layer is passivated by an alkali solution.

[0008] The present invention also relates to a method for preparing a high-performance buried resistance copper foil, comprising the following steps:

[0009] S1. Using a copper foil as the base copper foil, and the base copper foil serves as the conductive layer;

[0010] S2. Performing a pre-treatment for isolation on the base copper foil to obtain an isolation layer, and the isolation layer is a nickel-cobalt or nickel-tin alloy;

[0011] S3. Uniformly electroplating a nickel-phosphorus alloy on the isolation layer to obtain a resistance layer;

[0012] S4. Performing a post-treatment of passivation on the prepared resistance layer to obtain a buried resistance copper foil.

[0013] As a preferred technical solution, in the step S2, the pre-treatment means for isolation is preferably electroplating; the electroplating solution for the pre-treatment for isolation contains one or a combination of nickel chloride hexahydrate, cobalt chloride hexahydrate, potassium pyrophosphate, glycine, stannous chloride dihydrate.

[0014] As a preferred technical solution, in the electroplating solution for the pre-treatment for isolation in the step S2, the concentration of nickel chloride hexahydrate is 10 - 50 g / L, the concentration of cobalt chloride hexahydrate is 0 - 50 g / L, the concentration of stannous chloride dihydrate is 0 - 50 g / L, the concentration of potassium pyrophosphate is 50 - 500 g / L, the concentration of glycine is 5 - 50 g / L, the temperature of the electroplating solution is 25 - 65 °C, and the pH of the electroplating solution is 8 - 10.

[0015] As a preferred technical solution, in the step S3, the nickel-phosphorus electroplating solution for electroplating the nickel-phosphorus alloy contains nickel sulfate hexahydrate, sodium hypophosphite monohydrate, phosphoric acid, and boric acid, wherein the concentration of nickel sulfate hexahydrate is 50 - 200 g / L, the concentration of sodium hypophosphite monohydrate is 5 - 50 g / L, the concentration of phosphoric acid is 5 - 50 g / L, the concentration of boric acid is 10 - 50 g / L, the temperature of the electroplating solution is 25 - 95 °C, and the pH of the electroplating solution is 1 - 4.

[0016] As a preferred technical solution, a directional adsorption substance is further added to the nickel-phosphorus electroplating solution, and the directional adsorption substance includes one or several of 1,4-butyne diol, sodium benzenesulfinate, and sodium dodecyl sulfate.

[0017] As a preferred technical solution, in the step S4, an electrochemical passivation method is used to perform a post-treatment of passivation on the resistance layer; the main component of the passivation solution for the post-treatment of passivation is a strong alkali solution, and the concentration of the strong alkali is 5% - 50% mass fraction; the strong alkali includes one or several of sodium hydroxide, potassium hydroxide, magnesium hydroxide, barium hydroxide, and ammonia water.

[0018] The present invention has the following beneficial effects:

[0019] Before preparing the nickel-phosphorus alloy resistance layer of the present invention, an isolation layer is introduced, and the component is nickel-cobalt alloy or nickel-tin alloy. The purpose is to prevent the damage to the nickel-phosphorus resistance layer during the alkaline etching of copper in the processing of the product. The stability of the resistance value before and after the etching window opening of the product is ensured, and the difference before and after can be controlled within 2%.

[0020] The present invention introduces a directional adsorption substance into the electroplating solution, so that the adsorption amount at the high-position points on the surface of the copper foil is more than that at the low-position points, thereby effectively suppressing tip discharge, avoiding too large current density at the tips, improving the uniformity of the electric field, so that the resistive material can be uniformly deposited on the surface of the copper foil, and the sheet resistance range is small, <1.5 Ω / sq. Here, the substance is generally 1,4-butynediol, sodium benzenesulfinate, sodium dodecyl sulfate, etc. having a surface-active effect.

[0021] The method of the present invention can improve the resistivity of the product, the resistivity ≥ 2.0×10-3 Ω·cm, and the ESD performance is better; the temperature coefficient of resistance is small, the resistance value drift is small after high-temperature pressing, and the difference before and after can be controlled within 1%. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 is a schematic structural diagram of the buried resistor copper foil;

[0023] Figure 2 is a planar SEM electron micrograph of the buried resistor copper foil, with a magnification of 20k;

[0024] Figure 3 is a cross-sectional SEM electron micrograph of the buried resistor copper foil, with a magnification of 100k.

[0025] Reference numerals:

[0026] 1. Raw foil layer 2. Surface treatment layer 3. Isolation layer 4. Resistance layer. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0027] The terms "first", "second", "third", "fourth", etc. (if any) in the specification, claims and above-mentioned drawings of the present invention are used to distinguish similar objects, and do not have to be used to describe a specific order or sequence. In addition, the terms "comprising" or "having" and any variations thereof are intended to cover non-exclusive inclusion. For example, a process, method, system, product or device that includes a series of steps or units does not have to be limited to those steps or units clearly listed, but may include other steps or units not clearly listed or inherent to these processes, methods, products or devices.

[0028] Example 1:

[0029] Step S1:

[0030] Use commercially available HTE copper foil as the conductive layer. The thickness of the base copper foil is 130 μm, the roughness Rz of the treated surface is 10 μm, and the areal density is 1200 g / m 2 , the tensile strength is 800 MPa, and the elongation is 20%;

[0031] Step S2:

[0032] 1) Prepare the pre-treatment solution for isolation. Add the following reagents to industrial pure water: nickel chloride hexahydrate at 40 g / L, cobalt chloride hexahydrate at 10 g / L, potassium pyrophosphate at 300 g / L, and glycine at 25 g / L. Stir vigorously until the solution is clear. Adjust the pH of the solution to 8.7 and keep the solution temperature at 40 °C;

[0033] 2) Use an insoluble titanium plate as the anode and the base copper foil as the cathode. Place them parallel in the pre-treatment solution for isolation and conduct electroplating with a current density of 5 A / dm 2 , and an isolation layer is obtained on the treated surface of the copper foil with a thickness of 40 nm;

[0034] Step S3:

[0035] 1) Prepare the nickel-phosphorus electroplating solution. Add nickel sulfate hexahydrate at 100 g / L and sodium hypophosphite monohydrate at 10 g / L to industrial pure water and stir to dissolve evenly; then slowly add phosphoric acid at 30 g / L and boric acid at 20 g / L to the above mixed solution. Stir vigorously until the solution is clear. Adjust the pH of the solution to 1.8 and keep the solution temperature at 55 °C;

[0036] 2) Use the copper foil after pre-treatment for isolation as the cathode and conduct electroplating with a current density of 5 A / dm 2 , and the thickness of the resistance layer is 500 nm;

[0037] Step S4:

[0038] Use a 10% potassium hydroxide aqueous solution as the passivation treatment solution, with a current density of 1.5 A / dm 2 , a positive duty cycle of 70%, a negative duty cycle of 30%, and a frequency of 3000 Hz to deeply passivate the resistance layer for 5 minutes, and finally obtain a high-performance buried resistor copper foil product;

[0039] Step S5:

[0040] Test the performance of the buried resistor copper foil.

[0041] Example 2:

[0042] Step S1:

[0043] Use commercially available RTF copper foil as the conductive layer. The thickness of the base copper foil is 18μm, the surface roughness of the treated surface Rz = 3.5μμm, and the areal density is 151g / m 2 , the tensile strength is 315MPa, and the elongation is 7%;

[0044] Step S2:

[0045] 1) Prepare the pre-treatment solution for isolation. Add the following reagents to industrial pure water: nickel chloride hexahydrate at 45g / L, stannous chloride dihydrate at 50g / L, potassium pyrophosphate at 400g / L, and glycine at 35g / L. Stir vigorously until the solution is clear. Adjust the pH of the solution to 9 and keep the solution temperature at 55°C;

[0046] 2) Use an insoluble titanium plate as the anode and the base copper foil as the cathode. Place them parallel in the pre-treatment solution for isolation and conduct electroplating with a current density of 8A / dm 2 , and an isolation layer is obtained on the treated surface of the copper foil with a thickness of 80nm;

[0047] Step S3:

[0048] 1) Prepare the nickel-phosphorus electroplating solution. Add nickel sulfate hexahydrate at 150g / L and sodium hypophosphite monohydrate at 5g / L to industrial pure water and stir to dissolve evenly; then slowly add phosphoric acid at 40g / L and boric acid at 30g / L to the above mixed solution. Stir vigorously until the solution is clear. Adjust the pH of the solution to 2.5 and keep the solution temperature at 35°C;

[0049] 2) Use the copper foil after pre-treatment for isolation as the cathode and conduct electroplating with a current density of 8A / dm 2 , and the thickness of the resistance layer is 800nm;

[0050] Step S4:

[0051] Use a 15% potassium hydroxide aqueous solution as the passivation treatment solution, with a current density of 3A / dm 2 , a positive duty cycle of 90%, a negative duty cycle of 10%, and a frequency of 2000Hz to conduct deep passivation on the resistance layer for 3 minutes, and finally obtain a high-performance buried resistance copper foil product.

[0052] Step S5:

[0053] Test the performance of the buried resistance copper foil.

[0054] Example 3:

[0055] Step S1:

[0056] Use commercially available HTE copper foil as the conductive layer. The thickness of the base copper foil is 18μm, the surface roughness of the treated surface Rz = 7.0μm, and the areal density is 155g / m 2, the tensile strength is 530 MPa and the elongation is 11%;

[0057] Step S2:

[0058] 1) Prepare the pre-treatment solution for isolation. Add the following reagents to industrial pure water: nickel chloride hexahydrate at 30 g / L, stannous chloride dihydrate at 30 g / L, potassium pyrophosphate at 150 g / L, and glycine at 20 g / L. Stir vigorously until the solution is clear. Adjust the pH of the solution to 8 and keep the solution temperature at 50 °C;

[0059] 2) Use an insoluble titanium plate as the anode and the base copper foil as the cathode. Place them parallel in the pre-treatment solution for isolation and conduct electroplating with a current density of 2 A / dm 2 , and an isolation layer is obtained on the treated surface of the copper foil with a thickness of 20 nm;

[0060] Step S3:

[0061] 1) Prepare the nickel-phosphorus electroplating solution. Add nickel sulfate hexahydrate at 150 g / L and sodium hypophosphite monohydrate at 15 g / L to industrial pure water and stir to dissolve evenly; then slowly add phosphoric acid at 15 g / L and boric acid at 30 g / L to the above mixed solution. Stir vigorously until the solution is clear. Adjust the pH of the solution to 2.2 and keep the solution temperature at 75 °C;

[0062] 2) Use the copper foil that has undergone pre-treatment for isolation as the cathode and conduct electroplating with a current density of 2 A / dm 2 , and the thickness of the resistance layer is 300 nm;

[0063] Step S4:

[0064] Use a 30% aqueous potassium hydroxide solution as the passivation treatment solution, with a current density of 1 A / dm 2 , a positive duty cycle of 80%, a negative duty cycle of 20%, and a frequency of 4000 Hz to deeply passivate the resistance layer for 8 minutes, and finally obtain a high-performance buried resistance copper foil product.

[0065] Step S5:

[0066] Test the performance of the buried resistance copper foil.

[0067] Example 4:

[0068] Step S1:

[0069] Use a commercially available RTF copper foil as the conductive layer. The thickness of the base copper foil is 35 μm, the surface roughness Rz of the treated surface is 4.0 μm, and the areal density is 285 g / m 2 , the tensile strength is 420 MPa and the elongation is 8%;

[0070] Step S2:

[0071] 1) Prepare the pre - isolation treatment solution by adding the following reagents to industrial pure water: nickel chloride hexahydrate at 10 g / L, cobalt chloride hexahydrate at 30 g / L, potassium pyrophosphate at 200 g / L, and glycine at 15 g / L. Stir vigorously until the solution is clear, adjust the pH of the solution to 8.1, and maintain the solution temperature at 30 °C;

[0072] 2) Use an insoluble titanium plate as the anode and the base copper foil as the cathode, place them parallel in the pre - isolation treatment solution, and conduct electroplating with a current density of 0.5 A / dm 2 to obtain an isolation layer on the treated surface of the copper foil, with the thickness of the isolation layer being 20 nm;

[0073] Step S3:

[0074] 1) Prepare the nickel - phosphorus electroplating solution by adding nickel sulfate hexahydrate at 150 g / L and sodium hypophosphite monohydrate at 20 g / L to industrial pure water, stir and dissolve evenly; then slowly add phosphoric acid at 20 g / L and boric acid at 35 g / L to the above - mentioned mixed solution, stir vigorously until the solution is clear, adjust the pH of the solution to 1, and maintain the solution temperature at 70 °C;

[0075] 2) Use the copper foil that has undergone pre - isolation treatment as the cathode, conduct electroplating with a current density of 3 A / dm 2 to obtain a resistance layer with a thickness of 200 nm;

[0076] Step S4:

[0077] Use a 20% potassium hydroxide aqueous solution as the passivation treatment solution, with a current density of 2 A / dm 2 , a positive duty cycle of 60%, a negative duty cycle of 40%, and a frequency of 1500 Hz to conduct deep passivation on the resistance layer for 6 minutes, finally obtaining a high - performance buried - resistance copper foil product.

[0078] Step S5:

[0079] Test the performance of the buried - resistance copper foil.

[0080] Example 5:

[0081] Step S1:

[0082] Use a commercially available VLP copper foil as the conductive layer, with the thickness of the base copper foil being 4.5 μm, the surface roughness Rz of the treated surface being 2.0 μm, the areal density being 40 g / m 2 , the tensile strength being 200 MPa, and the elongation being 1%;

[0083] Step S2:

[0084] 1) Prepare the pre - isolation treatment solution. Add the following reagents to industrial pure water: nickel chloride hexahydrate at 50 g / L, cobalt chloride hexahydrate at 50 g / L, potassium pyrophosphate at 500 g / L, and glycine at 50 g / L. Stir vigorously until the solution is clear. Adjust the pH of the solution to 10 and maintain the solution temperature at 65 °C;

[0085] 2) Use an insoluble titanium plate as the anode and the base copper foil as the cathode. Place them parallel in the pre - isolation treatment solution and conduct electroplating with a current density of 10 A / dm 2 , and obtain an isolation layer on the treated surface of the copper foil with a thickness of 100 nm;

[0086] Step S3:

[0087] 1) Prepare the nickel - phosphorus electroplating solution. Add nickel sulfate hexahydrate at 200 g / L and sodium hypophosphite monohydrate at 25 g / L to industrial pure water, stir and dissolve evenly; then slowly add phosphoric acid at 50 g / L and boric acid at 50 g / L to the above - mentioned mixed solution. Stir vigorously until the solution is clear. Adjust the pH of the solution to 3.1 and maintain the solution temperature at 95 °C;

[0088] 2) Use the copper foil treated by pre - isolation as the cathode and conduct electroplating with a current density of 10 A / dm 2 , and the thickness of the resistance layer is 1000 nm;

[0089] Step S4:

[0090] Use a 40% potassium hydroxide aqueous solution as the passivation treatment solution, with a current density of 0.01 A / dm 2 , a positive duty cycle of 50%, a negative duty cycle of 50%, and a frequency of 5000 Hz to deeply passivate the resistance layer for 10 min, and finally obtain a high - performance buried - resistance copper foil product.

[0091] Step S5:

[0092] Test the performance of the buried - resistance copper foil.

[0093] Example 6:

[0094] Step S1:

[0095] Use a commercially available HVLP copper foil as the conductive layer. The thickness of the base copper foil is 12 μm, the surface roughness Rz of the treated surface is 0.4 μm, the areal density is 107 g / m 2 , the tensile strength is 300 MPa, and the elongation is 8%;

[0096] Step S2:

[0097] 1) Prepare the pre - isolation treatment solution by adding the following reagents to industrial pure water: nickel chloride hexahydrate at 15 g / L, stannous chloride dihydrate at 10 g / L, potassium pyrophosphate at 50 g / L, and glycine at 5 g / L. Stir vigorously until the solution is clear, adjust the pH of the solution to 9.5, and maintain the solution temperature at 25 °C;

[0098] 2) Use an insoluble titanium plate as the anode and the base copper foil as the cathode, and place them parallel in the pre - isolation treatment solution. Apply electroplating with a current density of 0.1 A / dm 2 , and obtain an isolation layer on the treated surface of the copper foil with a thickness of 10 nm;

[0099] Step S3:

[0100] 1) Prepare the nickel - phosphorus electroplating solution by adding nickel sulfate hexahydrate at 50 g / L and sodium hypophosphite monohydrate at 50 g / L to industrial pure water, and stir to dissolve evenly; then slowly add phosphoric acid at 5 g / L and boric acid at 40 g / L to the above - mentioned mixed solution. Stir vigorously until the solution is clear, adjust the pH of the solution to 4.0, and maintain the solution temperature at 25 °C;

[0101] 2) Use the copper foil after pre - isolation treatment as the cathode, apply electroplating with a current density of 1 A / dm 2 , and the thickness of the resistance layer is 50 nm;

[0102] Step S4:

[0103] Use a 50% potassium hydroxide aqueous solution as the passivation treatment solution, with a current density of 5 A / dm 2 , a positive duty cycle of 100%, a negative duty cycle of 0%, and a frequency of 500 Hz to deeply passivate the resistance layer for 1 minute, and finally obtain a high - performance buried - resistance copper foil product.

[0104] Step S5:

[0105] Test the performance of the buried - resistance copper foil.

[0106] Comparative Example 1:

[0107] Step S1:

[0108] Use a commercially available HTE copper foil as the conductive layer. The thickness of the base copper foil is 130 μm, the surface roughness Rz of the treated surface is 10 μm, the areal density is 1200 g / m 2 , the tensile strength is 800 MPa, and the elongation is 20%;

[0109] Step S2:

[0110] No pre - isolation treatment

[0111] Step S3:

[0112] 1) Prepare a nickel-phosphorus electroplating solution by adding 240 g / L of nickel sulfate hexahydrate, 45 g / L of nickel chloride hexahydrate, 15 g / L of phosphorous acid, and 30 g / L of boric acid to industrial pure water, and stir to dissolve evenly; adjust the pH of the solution to 1.25 and maintain the solution temperature at 70 °C;

[0113] 2) Use the copper foil after pre-treatment by isolation as the cathode, conduct electroplating with a current density of 3 A / dm 2 , and the thickness of the resistance layer is 500 nm;

[0114] Step S4:

[0115] No post-treatment by passivation

[0116] Step S5:

[0117] Test the performance of the buried resistance copper foil.

[0118] Comparative Example 2:

[0119] Step S1:

[0120] Use a commercially available RTF copper foil as the conductive layer. The thickness of the base copper foil is 18 μm, the surface roughness Rz of the treated surface is 3.5 μm, the surface density is 151 g / m 2 , the tensile strength is 315 MPa, and the elongation is 7%;

[0121] Step S2:

[0122] No pre-treatment by isolation

[0123] Step S3:

[0124] 1) Prepare a nickel-phosphorus electroplating solution by adding 150 g / L of nickel sulfate hexahydrate and 5 g / L of sodium hypophosphite monohydrate to industrial pure water, and stir to dissolve evenly; then slowly add 40 g / L of phosphoric acid and 30 g / L of boric acid to the above mixed solution, stir vigorously until the solution is clear, adjust the pH of the solution to 2.5, and maintain the solution temperature at 35 °C;

[0125] 2) Use the copper foil after pre-treatment by isolation as the cathode, conduct electroplating with a current density of 8 A / dm 2 , and the thickness of the resistance layer is 800 nm;

[0126] Step S4:

[0127] Use a 15% aqueous potassium hydroxide solution as the passivation treatment solution, with a current density of 3 A / dm 2 , a positive duty cycle of 90%, a negative duty cycle of 10%, and a frequency of 2000 Hz to deeply passivate the resistance layer for 3 minutes, and finally obtain a high-performance buried resistance copper foil product.

[0128] Step S5:

[0129] Test the performance of the buried resistance copper foil.

[0130] Comparative Example 3:

[0131] Step S1:

[0132] Use a commercially available HTE copper foil as the conductive layer. The thickness of the base copper foil is 18 μm, the surface roughness Rz of the treated surface is 7.0 μm, the surface density is 155 g / m 2 , the tensile strength is 530 MPa, and the elongation is 11%;

[0133] Step S2:

[0134] 1) Prepare the pre-treatment solution for isolation. Add the following reagents to industrial pure water: nickel chloride hexahydrate at 30 g / L, stannous chloride dihydrate at 30 g / L, potassium pyrophosphate at 150 g / L, and glycine at 20 g / L. Stir vigorously until the solution is clear. Adjust the pH of the solution to 8 and keep the solution temperature at 50 °C;

[0135] 2) Use an insoluble titanium plate as the anode and the base copper foil as the cathode. Place them parallel in the pre-treatment solution for isolation and conduct electroplating with a current density of 2 A / dm 2 to obtain an isolation layer on the treated surface of the copper foil. The thickness of the isolation layer is 20 nm;

[0136] Step S3:

[0137] 1) Prepare the nickel-phosphorus electroplating solution. Add nickel sulfate hexahydrate at 150 g / L and sodium hypophosphite monohydrate at 15 g / L to industrial pure water and stir to dissolve evenly; then slowly add phosphoric acid at 15 g / L and boric acid at 30 g / L to the above mixed solution. Stir vigorously until the solution is clear. Adjust the pH of the solution to 2.2 and keep the solution temperature at 75 °C;

[0138] 2) Use the copper foil after pre-treatment for isolation as the cathode and conduct electroplating with a current density of 2 A / dm 2 to obtain a resistance layer with a thickness of 300 nm;

[0139] Step S4:

[0140] No post-treatment for deep passivation.

[0141] Step S5:

[0142] Test the performance of the buried resistance copper foil.

[0143]

[0144]

[0145]

[0146]

[0147] Results of Examples and Comparative Examples

[0148]

[0149] By comparing Example 1 and Comparative Example 1, it can be found that the buried resistor copper foil prepared by the present invention has a higher resistivity compared with the conventional process, increasing from 5.0×10 -4 Ω·cm to 2.25×10 -3 Ω·cm; better electrostatic discharge resistance performance, increasing from 900V to 3000V; lower temperature coefficient of resistance, decreasing from 110PPM / ℃ to below 55PPM / ℃, and the resistance value fluctuation after pressing is within 1%; better etching resistance performance, and the resistance value fluctuation after etching window opening is within 2%.

[0150] By comparing Example 2 and Comparative Example 2, it can be found that the product with the isolation pretreatment process has better etching resistance performance, and the resistance value fluctuation after etching window opening is within 2%.

[0151] By comparing Example 3 and Comparative Example 3, it can be found that the product with the deep passivation post-treatment process has a higher resistivity compared with the product without the deep passivation post-treatment process, increasing from 6.0×10 -4 Ω·cm to 2.3×10 -3 Ω·cm; better electrostatic discharge resistance performance, increasing from 1100V to 2000V.

[0152] As mentioned above, the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that: they can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements for some of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A high-performance buried resistor copper foil, characterized in that, The structure of the buried resistor copper foil includes a conductive layer, an isolation layer, and a resistor layer; the conductive layer is a base copper foil, the isolation layer is a nickel-cobalt or nickel-tin alloy, and the resistor layer is a nickel-phosphorus alloy.

2. The high-performance buried resistor copper foil according to claim 1, wherein The thickness of the conductive layer is 4.5 - 130 μm, the thickness of the isolation layer is 10 - 100 nm, and the thickness of the resistor layer is 50 - 1000 nm.

3. A high-performance buried resistor copper foil according to claim 1, characterized in that, The surface roughness Rz of the treated surface of the base copper foil is 0.4 - 10 μm, the surface density is 40 - 1200 g / m2; the tensile strength is 200 - 800 MPa, and the elongation is 1 - 20%.

4. A high-performance buried resistor copper foil according to claim 1, characterized in that, The resistor layer is passivated by an alkaline solution.

5. A preparation method of a high-performance buried resistor copper foil, characterized in that, It includes the following steps: S1. Use copper foil as the base copper foil, and the base copper foil serves as the conductive layer; S2. Perform pre-treatment before isolation on the base copper foil to obtain an isolation layer, and the isolation layer is a nickel-cobalt or nickel-tin alloy; S3. Uniformly electroplate nickel-phosphorus alloy on the isolation layer to obtain a resistor layer; S4. Perform post-treatment passivation on the prepared resistor layer to obtain a buried resistor copper foil.

6. The preparation method of a high-performance buried resistor copper foil according to claim 5, characterized in that, In the step S2, the pre-treatment method before isolation is preferably electroplating; the electroplating solution for pre-treatment before isolation contains one or a combination of nickel chloride hexahydrate, cobalt chloride hexahydrate, potassium pyrophosphate, glycine, stannous chloride dihydrate.

7. The preparation method of a high-performance buried resistor copper foil according to claim 5, characterized in that, In the electroplating solution for pre-treatment before isolation in the step S2, the concentration of nickel chloride hexahydrate is 10 - 50 g / L, the concentration of cobalt chloride hexahydrate is 0 - 50 g / L, the concentration of stannous chloride dihydrate is 0 - 50 g / L, the concentration of potassium pyrophosphate is 50 - 500 g / L, the concentration of glycine is 5 - 50 g / L, the temperature of the electroplating solution is 25 - 65 °C, and the pH of the electroplating solution is 8 - 10.

8. The preparation method of a high-performance buried resistor copper foil according to claim 5, characterized in that, In the step S3, the nickel-phosphorus electroplating solution for electroplating nickel-phosphorus alloy contains nickel sulfate hexahydrate, sodium hypophosphite monohydrate, phosphoric acid, and boric acid, where the concentration of nickel sulfate hexahydrate is 50 - 200 g / L, the concentration of sodium hypophosphite monohydrate is 5 - 50 g / L, the concentration of phosphoric acid is 5 - 50 g / L, the concentration of boric acid is 10 - 50 g / L, the temperature of the electroplating solution is 25 - 95 °C, and the pH of the electroplating solution is 1 - 4.

9. The preparation method of a high-performance buried resistor copper foil according to claim 5, characterized in that, A directional adsorption substance is also added to the nickel-phosphorus electroplating solution, and the directional adsorption substance includes one or a combination of 1,4-butynediol, sodium benzenesulfinate, sodium dodecyl sulfate.

10. The preparation method of a high-performance buried resistor copper foil according to claim 5, characterized in that, In the step S4, the resistor layer is subjected to post-treatment passivation using an electrochemical passivation method; the main component of the passivation solution for post-treatment passivation is a strong alkaline solution, and the concentration of the strong base is 5% - 50% by mass fraction; the strong base includes one or a combination of sodium hydroxide, potassium hydroxide, magnesium hydroxide, barium hydroxide, and ammonia water.

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