Embedded resistor copper foil, preparation method and application

Abstract

The invention relates to a buried resistance copper foil and a preparation method and application thereof, the buried resistance copper foil comprises a substrate copper foil and a buried resistance layer, the substrate copper foil comprises a raw foil and a nodulation layer, and the buried resistance layer comprises a corrosion inhibition layer, a resistance layer and a passivation layer. After being laminated with a hydrocarbon resin prepreg, the embedded resistor copper foil disclosed by the invention has excellent peel strength, and an embedded resistor prepared from the embedded resistor copper foil has high resistivity exceeding 1 * 10 <-3 > omega.cm; meanwhile, due to the existence of the slow release layer, the etching resistance of the resistance layer is greatly enhanced, and the resistance layer has a good application prospect.

Description

Technical Field

[0001] The present invention belongs to the technical field of electronic materials, and in particular relates to a buried barrier copper foil and a preparation method and application thereof. Background Art

[0002] Embedded passive technology (EPT) involves embedding passive components such as resistors and capacitors into printed circuit boards (PCBs) during the circuit board manufacturing process. This technology reduces the parasitic effects associated with surface-mount passive components, resulting in better signal transmission and less crosstalk. At the same time, it effectively frees up surface space, improving the integration and miniaturization of circuit boards, leading to the emergence of embedded resistor copper foil. Embedded resistor copper foil consists of two parts: a base copper foil and a resistor layer. After etching to create the pattern, the base copper foil serves as a support layer and provides a conductive circuit, while the resistor layer provides resistance. Embedded resistors are categorized into two technologies: thick film and thin film. Thick film technology involves screen-printing resistor paste onto copper foil. This method is susceptible to side etching or contamination from the etching solution during the resistor circuit manufacturing process, making resistance control difficult. Furthermore, the density of the paste coating will affect the electrical performance of the resistor after the window is opened. Thin film technology, on the other hand, involves depositing resistor material onto copper through processes such as electroplating or sputtering, ensuring uniformity and small size for the passive components.

[0003] At present, the main thin film buried resistor products are Ohmega-Ply series products produced by Ohmega electroplating method and TCR produced by Ticer sputtering method. R Compared to sputtering, the performance of the resistor layer produced by electroplating is less dependent on equipment, and higher resistivity can be achieved by electroplating non-metallic materials, achieving sufficient coating thickness in high-resistance products to ensure electrical reliability.

[0004] Due to the nature of the material, some domestic research on the resistance layer obtained by electroplating cannot exceed the resistivity of 1×10 -3 Ω·cm, the patterned buried resistor cannot carry a larger power and is easily corroded by etching solution during the downstream manufacturing process, resulting in a larger square resistance tolerance. The Ohmega-Ply series products produced by electroplating have a resistivity of 1.0×10 -3 Ω·cm, while providing high-value resistors, has also passed 2-8kV ESD stability testing, ensuring the electrical reliability of the resistor layer. However, with the iteration and update of high-frequency and high-speed PCB products, higher demands are placed on the electrical signal transmission integrity of copper foil. The products provided by Ohmega, when combined with high-performance materials such as hydrocarbon resin, provide poor peel strength. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide a buried copper foil and its preparation method and application. After the buried copper foil is pressed with a hydrocarbon resin prepreg, it has excellent peel strength, and the buried resistor prepared from the buried copper foil has a resistance of more than 1×10 -3 The resistivity of the resistor layer is high, and due to the presence of the slow-release layer, the etching resistance of the resistor layer is greatly enhanced, which has good application prospects.

[0006] The present invention provides a buried copper foil, comprising a base copper foil and a buried barrier layer, wherein the base copper foil comprises a raw foil and a nodular layer, and the buried barrier layer comprises a corrosion inhibition layer, a resistance layer, and a passivation layer; wherein the corrosion inhibition layer is in contact with the base copper foil; the base copper foil is subjected to a nodularization treatment, so that copper nodules in the nodular layer grow vertically in clusters on the treated surface of the raw foil; the buried copper foil has a resistance of 20 to 500 Ω / □ and a resistivity of 1.0 to 3.0×10 -3 The square resistance tolerance of products with specifications below 100Ω / □ shall not exceed ±5%, and the square resistance tolerance of products with specifications above 100Ω / □ shall not exceed ±10%.

[0007] According to the formula ①ρ=R S ×h, the resistivity of the resistance layer ρ≥1.0×10 -3 Ω·cm, and the resistivity can be adjusted to 1×10 -3 ~3.0×10 -3 Ω·cm.

[0008] Preferably, the thickness of the buried copper foil is between 12 and 35 μm. After being pressed with the CH RO04450F prepreg, a copper-clad laminate is formed. The peel strength thereof is tested to be between 0.6 and 1.3 kgf / mm.

[0009] Preferably, the Sdr of the treated surface of the nodular layer is 20-30%, the diameter of the copper nodules is between 300-500 nm, and the height of the stacked copper teeth cross section is between 2-6 μm.

[0010] Preferably, the corrosion-inhibiting layer comprises one or more elements selected from nickel, tin, cobalt, copper, chromium, zinc, palladium, aluminum, silicon, and oxygen. The thickness of the corrosion-inhibiting layer is 15 to 30 nm. The corrosion-inhibiting layer can be etched by a specific cleaning solution containing phosphorous acid, sulfuric acid, and a corrosion inhibitor. The corrosion inhibitor is selected from a compound containing a heterocyclic ring or a benzoheterocyclic compound containing a heterocyclic ring, wherein the heteroatoms in the heterocyclic ring are at least two of nitrogen, sulfur, and oxygen.

[0011] Preferably, the elements of the resistor layer are selected from nickel, phosphorus, and an alloy of one or more of cobalt, chromium, aluminum, oxygen, silicon, titanium, molybdenum, tungsten, manganese, and copper. The thickness of the resistor layer is 0.03 to 0.45 μm. The nickel content of the resistor layer is between 70 and 90 wt%, the phosphorus content is between 8 and 28 wt%, and the content of other elements is between 2 and 22 wt%.

[0012] Preferably, the passivation layer comprises oxides formed from one or more of cobalt, molybdenum, silicon, carbon, oxygen, aluminum, copper, chromium, zinc, and oxygen. The thickness of the passivation layer is 5 to 15 nm.

[0013] The present invention also provides a method for preparing a buried copper foil, comprising the following steps:

[0014] S1: performing nodularization treatment on the base copper foil;

[0015] S2: Electroplating a corrosion inhibition layer and a resistance layer in sequence on the base copper foil after the anode treatment;

[0016] S3: performing a passivation treatment on the above-mentioned resistance layer to form a passivation layer, that is, obtaining a buried resistance copper foil.

[0017] Preferably, the anode formation treatment in step S1 is a roughening and solidification treatment performed by applying an asymmetric positive and negative pulse alternating current in an acidic roughening solution of high concentration sulfuric acid and low concentration copper sulfate.

[0018] Furthermore, the composition of the acidic roughening solution is Cu 2+ 10-15 g / L, H2SO4 100-120 g / L, and an additive consisting of one or more of sodium tungstate, sodium molybdate, potassium dichromate, stannous sulfate, and palladium sulfate 5-200 mg / L.

[0019] Furthermore, the asymmetric positive and negative pulse alternating current is used for roughening and curing, specifically using a positive and negative pulse alternating current density for electroplating, and the current density of the negative pulse current is 0.5 to 2A / dm 2 ; The current density of the positive pulse current is 40~80A / dm 2 The time proportion of negative pulse current in each cycle is 1-10%, and the pulse frequency is 30-100Hz.

[0020] Preferably, in step S2, before electroplating the corrosion inhibition layer, the base copper foil that has undergone the anode treatment is pickled and activated with a 10-15 wt % sulfuric acid aqueous solution.

[0021] Preferably, in step S2, power is applied between the anode plate and the rolled base copper foil to electroplate and form the corrosion inhibition layer and the resistance layer. The corrosion inhibition layer plating solution contains 7-15 g / L Ni 2+and 1-5g / L CrCl3; the resistance layer plating solution contains 20-40g / L Ni 2+ and 15-35 g / L NaH2PO2.

[0022] Preferably, in step S2, when electroplating, the electroplating solution of the corrosion inhibition layer and the resistance layer is 15 to 30 m 3 / h flow rate is continuously filtered with powdered activated carbon to remove solid impurities from the plating solution.

[0023] In addition, the resistance layer electroplating solution also contains a metal complexing agent, which is selected from one or more of potassium pyrophosphate, aminohydroxy complexing agent, mercapto complexing agent, organic phosphonate, and polyacrylic acid, with a concentration of 15 to 200 g / L.

[0024] In addition, the resistance layer electroplating solution further contains an oxidant, which is selected from one or more of peroxides, nitrates, manganates, chromates, molybdates, tungstates, nickelates, orthophosphates, and vanadates, with a concentration of 0.8 to 10 g / L.

[0025] Preferably, the electroplating solution of the passivation layer in step S3 contains 2-10 g / L of glucose and 0.5-1.5 g / L of CrO 3 .

[0026] Preferably, in step S2, the current density is 100-150A / dm 2 ;Electroplating solution temperature 60-80℃.

[0027] The present invention also provides an application of a buried resistor copper foil in preparing a buried resistor, which specifically includes the following steps:

[0028] First etching: The buried copper foil is laminated with a hydrocarbon prepreg CH RO04450F to produce a buried copper clad laminate, printed with a first photoresist and developed to produce a combined copper foil and buried resistor pattern, and the excess copper layer is etched using an alkaline cuprammonia etching solution;

[0029] Second etching: Use acidic copper sulfate solution to directionally etch away excess resistor material and strip off the remaining portion of the first photoresist layer;

[0030] The third etching: Use a second photoresist (which can be the same as or different from the first photoresist) to print and develop the conductor protection pattern, and use alkaline cuprammonia etching solution to remove the exposed copper layer again; use the corrosion inhibition layer cleaning solution to remove the corrosion inhibition layer on the surface of the resistor layer to expose the window resistor layer; finally, peel off the remaining part of the second photoresist layer to obtain the buried resistor.

[0031] In addition, the corrosion inhibition layer cleaning solution also contains a buffer selected from 5-30 g / L phosphoric acid, 2-10 g / L boric acid, and 10-40 g / L of one or more ammonium salt buffers such as ammonium chloride, ammonium sulfate, ammonium bicarbonate, and ammonium nitrate.

[0032] The general description of the present invention above is only intended to illustrate or explain the present invention, and does not limit the scope of the present invention.

[0033] Beneficial effects

[0034] The present invention performs a special nodularization treatment on the base copper foil, so that the copper nodules on the treated surface are evenly distributed. The copper nodules grow vertically in clusters on the treated surface of the raw foil, and the copper teeth have a moderate height, which not only ensures the bonding force during pressing, but also improves the thickness uniformity of the resistor layer. The buried resistor layer has a three-layer structure, in which the amorphous structure and special element ratio of the resistor layer inhibit the migration of electrons. The amorphous structure of the resistor layer and the uniform distribution of the copper nodules work together to help achieve a high resistivity of the resistor layer. The corrosion inhibition layer can prevent the etching solution from corroding the resistor layer, so that the resistor layer has a more uniform resistance value and excellent electrical properties. After the buried resistor copper foil is pressed with a hydrocarbon resin prepreg, it has excellent peel strength, and the buried resistor prepared from the buried resistor copper foil has a resistance of more than 1×10 -3 The resistivity of the resistor layer is high, and due to the presence of the slow-release layer, the etching resistance of the resistor layer is greatly enhanced, which has good application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 It is a schematic structural diagram of the buried copper foil of the present invention.

[0036] Figure 2 This is a plan view (1K magnification) of the buried copper foil of the present invention scanned by an electron microscope.

[0037] Figure 3 This is a cross-sectional electron microscope scanning image (3K times) of the buried copper foil of the present invention.

[0038] Figure 4 This is a cross-sectional electron microscope scanning image (30K magnification) of the buried copper foil of the present invention.

[0039] Figure 5 This is a scanning electron microscope image (7K magnification) of the cross section of the resistor layer of the buried copper foil of the present invention.

[0040] Figure 6 This is the step of making the buried resistor of the buried copper foil of the present invention.

[0041] Figure 7 This is a square resistance test point diagram of the resistor layer of the buried copper foil of the present invention.

[0042] The reference numerals are as follows:

[0043] 1. Base copper foil; 11. Raw foil; 12. Tubular layer; 2. Buried barrier layer; 21. Corrosion inhibition layer; 22. Resistor layer; 23. Passivation layer. DETAILED DESCRIPTION

[0044] Below in conjunction with specific embodiment, further set forth the present invention.Should be understood that these embodiments are only used to illustrate the present invention and are not used in limiting the scope of the present invention.In addition, should be understood that after reading the content taught by the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms fall equally within the scope limited by the appended claims of the application.

[0045] Hereinafter, preferred embodiments of the present invention will be described in detail.

[0046] Example 1

[0047] Step S0:

[0048] The customized base copper foil is subjected to nodularization treatment: roughening and curing treatment is performed by applying asymmetric positive and negative pulse alternating current in an acidic roughening solution of high concentration sulfuric acid and low concentration copper sulfate.

[0049] Furthermore, the composition of the acidic roughening solution is Cu 2+ 10g / L, H2SO4 120g / L, additive sodium tungstate 10mg / L.

[0050] Furthermore, the asymmetric positive and negative pulse alternating current is used for roughening and curing, specifically using a positive and negative pulse alternating current density for electroplating, and the current density of the negative pulse current is 1.5A / dm 2 ; The current density of large pulse current is 60A / dm 2 The negative pulse current time in each cycle accounts for 8%, and the pulse frequency is 30Hz.

[0051] Step S1:

[0052] The customized base copper foil was pickled and activated using a 10 wt % sulfuric acid aqueous solution. The physical properties of the base copper foil are shown in Table 2.

[0053] Step S2:

[0054] ① Electroplating corrosion inhibition layer on the base copper foil, the slow-release layer plating solution contains 11g / L Ni 2+ , 3g / L CrCl3; the buffer is boric acid, the concentration is 15.2g / L;

[0055] ② Electroplate the resistor layer on the base copper foil. The resistor layer plating solution contains 30g / L Ni 2+, 25g / L NaH2PO2, the concentration of the complexing agent potassium pyrophosphate is 135g / L, the concentration of the oxidant Ni(NO3)2 is 3.2g / L; the current density is 100A / dm 2 ; Plating bath temperature 65℃;

[0056] Step S3:

[0057] S3: performing a passivation treatment on the resistor layer to form a passivation layer, namely, obtaining a buried copper foil; wherein the passivation solution contains 3.0 g / L of glucose and 0.5 g / L of CrO3.

[0058] Example 2

[0059] Different from Example 1, in step S2, the concentration of potassium pyrophosphate is 150 g / L and the concentration of Ni(NO3)2 is 6.1 g / L.

[0060] Example 3

[0061] Different from Example 1, in step S2, the concentration of potassium pyrophosphate is 150 g / L and the concentration of Ni(NO3)2 is 6.2 g / L.

[0062] Example 4

[0063] The difference from Example 1 is that in step S2, the concentration of boric acid is 20 g / L, the concentration of Ni(NO3)2 is 3.3 g / L, and the current density is 200 A / dm 2 .

[0064] Example 5

[0065] The difference from Example 1 is that in step S2, the concentration of potassium pyrophosphate is 150 g / L, the concentration of Ni(NO3)2 is 6 g / L, the concentration of boric acid is 10 g / L, and the current density is 75 A / dm 2 .

[0066] Comparative Example 1

[0067] Different from Example 1, in step S2, the concentration of potassium pyrophosphate is 120 g / L, and Ni(NO3)2 is not added.

[0068] Comparative Example 2

[0069] Different from Example 1, in step S1, conventional HTE copper foil is used as the base copper foil.

[0070] Comparative Example 3

[0071] Different from Example 1, in step S1, conventional RTF copper foil is used as the base copper foil.

[0072] Comparative Example 4

[0073] Different from Example 1, in step S1, conventional HVLP copper foil is used as the base copper foil.

[0074] Comparative Example 5

[0075] Different from Comparative Example 1, in step S1, conventional HTE copper foil is used as the base copper foil.

[0076] The parameters and formulas of the above embodiments and comparative examples are shown in Table 1.

[0077] Table 1

[0078]

[0079]

[0080] Physical properties of base copper foil

[0081] The treated surface Rz of the base copper foil of the present invention was measured using a contact roughness tester, and the treated surface Sdr was measured using an optical laser confocal microscope. Tensile strength and elongation were measured using a room-temperature tensile testing machine and a 180°C high-temperature tensile testing machine. Table 2 shows the basic physical properties of the base copper foil.

[0082] Table 2

[0083]

[0084] Next, the properties of the manufactured buried copper foil samples (Examples 1 to 5 and Comparative Examples 1 to 4) were measured. The measurement method is as follows. Examples 1 to 5 are respectively designed by adjusting the formula, electroplating process and foil running time to design samples with different specifications of square resistance, namely 50Ω / □, 100Ω / □, 250Ω / □, 25Ω / □, and 500Ω / □. Comparative Examples 1 to 5 are respectively fixed with a 200nm thickness of the resistive layer, and the buried copper foil samples are obtained by electroplating the resistive layer on the customized copper foil, conventional HTE, RTF and HVLP base copper foil.

[0085] In order to more intuitively reflect the effects of the present invention, all embodiments and comparative examples adopt the same test procedure. The test items and methods are as follows. The specific test data are shown in Table 3.

[0086] ①Peel strength

[0087] The embedded copper clad laminate was produced by laminating the treated surface of the embedded copper foil with the hydrocarbon resin prepreg RO04450F. The bonding strength was tested using a 180° tensile testing machine. Only data showing no residual resistance layer on the PP board after peeling was valid.

[0088] ②Square resistance test

[0089] The copper clad laminate of the present invention, which is laminated with the embedded copper foil and hydrocarbon resin prepreg RO04450F, is etched with alkaline copper-ammonia etching solution to remove the surface copper layer, and then the residual corrosion inhibition layer is removed with corrosion inhibition layer cleaning solution to expose the entire resistance layer. The square resistance of the exposed resistance layer after etching is tested using a four-probe square resistance tester. The square resistance of the exposed resistance layer is within the range of 150mm*150mm. Figure 7 The square resistance is measured at 16 points at each of the positions shown.

[0090] ③Thickness test

[0091] The buried copper foil of the present invention uses a Hitachi XRF coating thickness tester to test the thickness of the resistor layer after the pressing plate is etched, and the resistivity ρ of the resistor layer is calculated according to formula ①.

[0092] ④Electrical performance

[0093] like Figure 6 As shown, the buried copper foil of the present invention was made into a 10 mil*10 mil square buried resistor according to the above pattern making method, and the resistance of the buried resistor was tested at room temperature by using a Fluke 8050A digital oscilloscope.

[0094] The embedded resistors were tested using the HBM model at ±2, ±4, ±6, and ±8 kV ESD levels according to the AEC-Q200 standard. After the ESD test, the embedded resistors were tested at room temperature and their resistance values were recorded. The drift of the resistance values before and after the test was calculated.

[0095] The embedded resistors described above were subjected to three reflow cycles using an Electrovert ATMOS2000CR reflow oven at a peak temperature of 230°C. These three reflow cycles simulated the steps of wave soldering, reflow, and rework, emulating a typical circuit board assembly process. After the reflow cycles, the embedded resistors were tested at room temperature, and the resistance drift before and after the tests was calculated.

[0096] The embedded resistors described above were subjected to temperature shock resistance tests at -65°C to 125°C in a thermal shock test chamber according to Method 107 of GJB 360B-2009. The programmed thermal cycle lasted one hour per cycle, with a heating and dwell time of 15 minutes. Due to thermal inertia, the actual dwell time was approximately 7 minutes. After 210 thermal cycles, the embedded resistors were tested and their resistance values were recorded. The drift rate of the resistance values before and after the tests was calculated.

[0097] The above-mentioned buried resistor of the present invention is tested for the temperature coefficient of resistance (TCR) according to the MIL-STD-202Method 304 test standard. A detection probe station (HFSE-PB4) is used to heat and cool the device. The temperature is stabilized within the range of ±0.5°C and the test is divided into two temperature series. The first section is the TCR test of the 25°C→125°C heating process. The buried resistor is heated to 125°C and the resistance of the buried resistor is measured in steps of 25°C. The second section is the TCR test of the 25°C→-55°C cooling process. The resistance of the buried resistor at 25°C, -5°C, -30°C and -55°C is measured during the cooling process. According to the formula Calculate and take the maximum value of TCR of the two temperature series.

[0098] Table 3 Comparison of the effects of different embodiments and comparative examples

[0099]

[0100] Referring to Table 3, all buried copper foil samples manufactured according to Examples 1 to 5 have excellent peel strength, and no resistance layer remains on the peeled PP board, which is significantly better than the conventional HTE copper foil, RTF and HVLP copper foil in Comparative Examples 2 to 5. This is because the customized base copper foil uses fine anchoring nodule technology to stack the small copper nodules upward into conical copper teeth, and the copper teeth are tightly bonded to the dielectric layer by physical anchoring. In addition, the square resistance of the buried copper foil is in the range of 20 to 500Ω / □, the square resistance tolerance of products with specifications below 100Ω / □ does not exceed ±5%, and the square resistance tolerance of products with specifications below 100Ω / □ does not exceed ±10%, and the resistivity is in the range of 1.0 to 3.0×10 -3 In the range of Ω·cm, the buried copper foil sample of the present invention has better uniformity.

[0101] Furthermore, the resistors fabricated according to Examples 1 to 5 exhibited resistance drift within a range of ±0.05-0.5% after an 8kV ESD test, ±0.5-0.3% after a reflow soldering cycle test, and ±0.5-5% after a 210-hour thermal cycle test. The maximum TCR values for the resistors ranged from 30 to 200 ppm / °C over the 25-125°C temperature range, and from 50 to 403 ppm / °C over the 25--55°C temperature range. These results demonstrate that the embedded resistors fabricated according to the present invention exhibit excellent electrical reliability.

[0102] At the same time, comparing Example 1 and Comparative Example 1 with the same electroplating thickness of the resistor layer, the square resistance of the buried copper foil using an oxidant in the resistor layer plating solution is twice that of the buried copper foil not using an oxidant. This is because the oxidant acts on the redox process of nickel-phosphorus during the electroplating of the resistor layer, so that the nickel ions are not completely reduced, forming nickel hydroxide and nickel oxide with higher resistivity, and at the same time changing the microstructure of the amorphous nickel-phosphorus material, further improving the overall resistance of the resistor layer.

[0103] At the same time, it can be seen in Example 1 and Comparative Example 2 that the resistivity of the buried copper foil with customized nodular treatment surface is increased by half compared with the conventional HTE resistivity. This is because the resistance layer based on this extends the electron migration path in the microstructure, thereby increasing the resistivity of the resistance layer macroscopically.

[0104] At the same time, in Examples 3 and 5, the embedded resistors made from samples with a square resistance specification of ≥250Ω / □, after undergoing 2-8kV ESD, reflow soldering, and thermal cycle tests, have a resistance drift rate that is much greater than that of the embedded resistors made from samples with a square resistance specification of ≥250Ω / □. This is because the thickness of the resistor layer with a square resistance specification of ≥250Ω / □ is less than 120nm. According to Formula 1, the resistance value is inversely proportional to the thickness. The larger the square resistance specification, the greater the proportion of defects formed in the plating layer during the electroplating process of the resistor layer material, which in turn affects the electrical reliability of the resistor layer. Therefore, in practical applications, it is more necessary to increase the resistivity of the resistor layer material itself, so that high-resistance products can obtain a thicker resistor layer thickness, thereby improving the electrical reliability of the embedded resistor made of buried copper foil.

[0105] The present invention has been described above through the embodiments of the present invention, but the aforementioned embodiments are only examples of the technical concept of the present invention. It should be understood by those skilled in the art that various modifications and variations can be made without exceeding the basic features of the present invention. Therefore, the embodiments disclosed in the present invention are not intended to limit the technical concept of the present invention, but are only used for description, and the scope of the present invention is not limited by these embodiments. The scope of protection of the present invention should be interpreted based on the appended claims and fall within the scope of the appended claims.

Claims

1. A buried barrier copper foil, comprising a base copper foil and a buried barrier layer, characterized in that: The base copper foil includes a raw foil and a nodular layer, and the buried barrier layer includes a corrosion inhibition layer, a resistance layer, and a passivation layer; wherein the corrosion inhibition layer is in contact with the base copper foil; the base copper foil is subjected to a nodularization treatment so that the copper nodules in the nodular layer grow vertically in clusters on the treated surface of the raw foil; the resistance of the buried barrier copper foil is between 20 and 500 Ω / □, and the resistivity is between 1.0 and 3.0×10 -3 The square resistance tolerance of products with specifications below 100Ω / □ shall not exceed ±5%, and the square resistance tolerance of products with specifications above 100Ω / □ shall not exceed ±10%.

2. The buried copper foil according to claim 1, wherein: The peeling resistance of the buried copper foil on the dielectric layer of hydrocarbon resin is 0.6-1.3 kgf / mm.

3. The buried copper foil according to claim 1, wherein: The Sdr of the processed surface of the nodular layer is 20-30%, the diameter of the copper nodules is between 300-500 nm, and the height of the stacked copper teeth section is between 2-6 μm.

4. The buried copper foil according to claim 1, wherein: The elements of the corrosion inhibition layer are selected from one or an alloy composed of two or more elements of nickel, tin, cobalt, copper, chromium, zinc, palladium, aluminum, silicon, and oxygen.

5. The buried copper foil according to claim 1, wherein: The elements of the resistance layer are selected from nickel, phosphorus, and one or more elements of cobalt, chromium, aluminum, oxygen, silicon, titanium, molybdenum, tungsten, manganese, and copper.

6. The buried copper foil according to claim 1, wherein: The passivation layer includes oxides formed by one or more of cobalt, molybdenum, silicon, carbon, oxygen, aluminum, copper, chromium, zinc, and oxygen.

7. A method for preparing a buried copper foil, comprising the following steps: S1: performing nodularization treatment on the base copper foil; S2: electroplating a corrosion inhibition layer on the base copper foil after the anode treatment; S3: Electroplating a resistor layer on the corrosion inhibition layer and performing a passivation treatment to obtain a buried copper foil.

8. The preparation method according to claim 6, characterized in that: The agglomeration treatment in step S1 is a roughening and curing treatment performed by applying an asymmetric positive and negative pulse alternating current in an acidic roughening solution containing a metal salt additive.

9. The preparation method according to claim 6, characterized in that: The resistance layer electroplating solution in step S3 contains an oxidant.

10. Use of the buried resistor copper foil according to claim 1 in preparing a buried resistor.

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