A peelable embedded resistance copper foil and a transfer method and application of the resistance layer thereof

Abstract

This invention provides a peelable buried resistive copper foil and its resistive layer transfer method and application. The buried resistive copper foil of this invention comprises, from bottom to top: a conductive layer, a release layer, and a resistive layer. The buried resistive copper foil of this invention enables direct testing and flexible transfer of the resistive layer. By peeling off the conductive layer, the resistive layer is directly exposed, thereby enabling direct testing of the sheet resistance value. This achieves rapid and non-destructive testing of the resistive layer performance, fundamentally eliminating quality risks. By transferring the resistive layer and using secondary lamination, it forms a customized buried resistive copper-clad laminate with the user-customized copper foil, achieving "decoupling" between the resistive layer product and the substrate copper foil, greatly improving the flexibility of product design and the autonomy of the supply chain.

Description

Technical Field

[0001] This invention relates to the field of printed circuit board materials technology, and in particular to a method and application for transferring a peelable buried copper foil and its resistive layer. Background Technology

[0002] As electronic products become smaller, lighter, and higher-performance, the integration of components on PCBs is increasing. Buried resistor technology directly fabricates resistors inside the PCB, replacing traditional surface-mount discrete resistors, thereby saving surface space and improving circuit performance and reliability.

[0003] Buried resistive copper foil is a key material for achieving embedded and high-density components on printed circuit boards. Currently, the structure of buried resistive copper foil products on the market is typically: a resistive layer / a fixed conductive copper layer. Users purchase a complete "finished product" from upstream material suppliers, where the resistive layer and a specific base foil are permanently bonded. This traditional structure has two inherent drawbacks: 1. Severe lag and high risk in sheet resistance testing: Users must first laminate the buried resistive copper foil into a copper-clad laminate, and then undergo complex processes such as pattern transfer and etching before testing the sheet resistance of the resistive layer. If the sheet resistance value is unqualified, the entire copper-clad laminate and all preceding processes are scrapped, resulting in huge losses; 2. Rigid product form and lack of flexibility: Users are locked into specific specifications of base foil (such as thickness and type) provided by material suppliers. If design changes require different specifications of base foil, the corresponding entire buried resistive copper foil product must be purchased again, making it impossible to achieve "decoupling" and free combination of the resistive layer and base foil. Summary of the Invention

[0004] In view of the shortcomings of the prior art described above, the purpose of this invention is to provide a method and application for transferring a peelable buried copper foil and its resistive layer, which solves the problems of serious lag and high risk in the sheet resistance test of the buried copper foil resistive layer in the prior art, as well as the rigid product form, lack of flexibility, and inability to achieve "decoupling" and free combination of the resistive layer and the base foil.

[0005] To achieve the above and other related objectives, the present invention provides a peelable buried resistive copper foil, which comprises, from bottom to top: a conductive layer, a release layer, and a resistive layer.

[0006] The present invention also provides a method for preparing the peelable buried resist copper foil as described above, comprising the following steps: 1) Pre-treat the surface of the conductive layer material; 2) Prepare a peelable coating and apply it to the pretreated conductive layer to form a peelable layer; 3) A resistive layer is deposited on the surface of the release layer using a DC magnetron sputtering process or an electroplating process is used to electroplat a resistive layer on the surface of the release layer to obtain a peelable buried resistive copper foil.

[0007] The present invention also provides a method for testing the sheet resistance of a peelable buried copper foil resistive layer as described above, comprising the following steps: S1. Provide a peelable buried resist copper foil as described in any one of claims 1 to 3; S2. Peel off the conductive layer and the release layer to expose the resistive layer. S3. Test the resistance value on the exposed resistive layer surface.

[0008] The present invention also provides an application of the above-described peelable buried resist copper foil for the preparation of buried resist copper clad laminates.

[0009] The present invention also provides a method for preparing a copper-clad laminate with embedded resist, comprising the following steps: (1) Press the resistive layer of the peelable buried copper foil as described above with the prepreg; (2) Peel off the conductive layer and the release layer to transfer the resistive layer onto the prepreg; (3) The copper foil on the substrate is pressed together with the resistive layer on the prepreg to obtain a copper-clad laminate with buried resistive layer.

[0010] As described above, the method and application for transferring the peelable buried copper foil and its resistive layer of the present invention have the following beneficial effects: This invention, through its unique structural design, makes the resistive layer an independently testable and flexibly transferable "intermediate product." The sheet resistance of the resistive layer with peelable buried copper foil utilizes a direct testing method. This method is simple and fast, eliminating the need for traditional complex PCB manufacturing processes, and enabling rapid, non-destructive testing of resistive layer performance, fundamentally eliminating quality risks. The transfer application of the resistive layer with peelable buried copper foil allows for the free combination of the same resistive layer with different substrate copper foils. Through secondary lamination, it forms a customized buried copper clad laminate with a custom copper foil, achieving "decoupling" between the resistive layer product and the substrate copper foil, greatly improving product design flexibility and supply chain autonomy. Attached Figure Description

[0011] Figure 1 The diagram shown is a schematic representation of the structure of the peelable buried copper foil of the present invention.

[0012] Figure 2 The image shown is a photograph of the peelable buried copper foil with a carrier as described in Embodiment 4 of the present invention.

[0013] Explanation of icon numbers 101 Conductive Layer 201 Peel Layer 301 resistive layer 401 Carrier Layer Detailed Implementation

[0014] The following specific examples illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention.

[0015] In this invention, the terms "length", "width", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", and "outer" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this invention and simplifying the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0016] When a numerical range is disclosed herein, the range is considered continuous and includes the minimum and maximum values ​​of the range, as well as every value between the minimum and maximum values. Furthermore, when the range refers to an integer, it includes every integer between the minimum and maximum values ​​of the range. Additionally, when multiple ranges are provided to describe a feature or characteristic, the ranges may be combined. In other words, unless otherwise specified, all ranges disclosed herein should be understood to include any and all subranges to which they are included. For example, a specified range from “1 to 10” should be considered to include any and all subranges between the minimum value 1 and the maximum value 10. Exemplary subranges of the range 1 to 10 include, but are not limited to, 1 to 6.1, 3.5 to 7.8, 5.5 to 10, etc.

[0017] Furthermore, it should be understood that the one or more method steps mentioned in this invention do not preclude the existence of other method steps before or after the combined steps, or the insertion of other method steps between these explicitly mentioned steps, unless otherwise stated; moreover, unless otherwise stated, the numbering of each method step is merely a convenient tool for identifying each method step, and not for limiting the order of the method steps or limiting the scope of the invention. Changes or adjustments to their relative relationships, without substantially altering the technical content, should also be considered as within the scope of the invention.

[0018] The first aspect of the present invention provides a peelable buried resistive copper foil, which comprises, from bottom to top: a conductive layer, a release layer, and a resistive layer.

[0019] In some embodiments of the present invention, a carrier layer is further provided above the resistive layer. Preferably, the material of the carrier layer is selected from one or more of the following: resin adhesive, polyimide, modified polyimide, fiberglass cloth, fiberglass cloth composite material, paper substrate, composite substrate, HDI board, modified epoxy resin, modified acrylic resin, polyethylene terephthalate, polybutylene terephthalate, and polyethylene.

[0020] In some embodiments of the present invention, the carrier layer is an extremely thin metal layer with a thickness of 10-500 nm. For example, it can be 10-20 nm, 20-40 nm, 40-50 nm, 50-100 nm, 100-150 nm, 150-200 nm, 200-250 nm, 250-300 nm, 300-350 nm, 350-400 nm, 400-450 nm, or 450-500 nm. Its function is to protect the delicate resistive layer from scratches or oxidation during the transfer process. The thickness is sufficient for sheet resistance measurement, yet thin enough that its conductivity effect can be ignored in subsequent applications or it can be rapidly etched. The metal in the extremely thin metal layer is selected from one or more metals with low resistivity, such as copper, iron, nickel, chromium, aluminum, silicon, tungsten, molybdenum, thallium, yttrium, and iridium.

[0021] In some embodiments of the present invention, the conductive layer is an electrolytic copper foil.

[0022] In some embodiments of the present invention, the thickness of the conductive layer is 1~35um. For example, it is 1~6um, 6~12um, 12~18um, 18~20um, 20~25um, 25~30um, or 30~35um.

[0023] In some embodiments of the present invention, the raw material of the release layer is selected from one or more of silicone-modified acrylic acid, waterborne acrylic resin, UV-curable peelable adhesive, thermoplastic polyimide resin, and polyethylene terephthalate.

[0024] In some embodiments of the present invention, the sheet resistance of the resistive layer is from 10 Ω / sq to 1000 Ω / sq. For example, 10Ω / sq~50Ω / sq, 50Ω / sq~100Ω / sq, 100Ω / sq~150Ω / sq, 150Ω / sq~200Ω / sq、200Ω / sq~250Ω / sq、250Ω / sq~300Ω / sq、300Ω / sq~350Ω / sq、350Ω / sq~ 400Ω / sq, 400Ω / sq~450Ω / sq, 450Ω / sq~500Ω / sq, 500Ω / sq~600Ω / sq, 600Ω / sq~700Ω / sq, 700Ω / sq~800Ω / sq, 800Ω / sq~900Ω / sq or 900Ω / sq~1000Ω / sq.

[0025] A second aspect of the present invention provides a method for preparing the peelable buried resist copper foil as described above, comprising the following steps: 1) Pre-treat the surface of the conductive layer material; 2) Prepare a peelable coating and apply it to the pretreated conductive layer to form a peelable layer; 3) A resistive layer is deposited on the surface of the release layer using a DC magnetron sputtering process or an electroplating process is used to electroplat a resistive layer on the surface of the release layer to obtain a peelable buried resistive copper foil.

[0026] In some embodiments of the present invention, the pretreatment step in step 1) includes: sequentially subjecting the conductive layer material to alkaline washing to remove oil, rinsing with deionized water, and plasma activation treatment. This removes oil and impurities from the conductive layer surface and activates the surface microstructure. The plasma activation power is 150-600W, for example, 150-200W, 200-250W, 250-300W, 300-350W, 350-400W, 400-500W, or 500-600W; the treatment time is 20-150s, for example, 20-30s, 30-40s, 40-50s, 50-70s, 70-90s, 90-100s, 100-120s, 120-140s, or 140-150s; and the activation atmosphere is a mixture of argon and oxygen.

[0027] In some embodiments of the present invention, the peelable buried resistive copper foil in step 2) further includes a carrier layer, which is obtained by deposition on the surface of the resistive layer using a DC magnetron sputtering process.

[0028] In some embodiments of the present invention, the preparation of the peelable coating in step 2) includes the following steps: weighing the raw material of the peelable layer and dissolving it in a solvent, and stirring at high speed to obtain a uniform peelable coating; the solvent is N-methylpyrrolidone.

[0029] In some embodiments of the present invention, the target material for the DC magnetron sputtering process described in step 3) is a nickel-chromium alloy target with a Ni:Cr ratio of 60~90 at%:10~40 at%, for example, 60~70 at%:10~40 at%, 70~80 at%:10~40 at%, 80~90 at%:10~40 at%, 60~90 at%:10~20 at%, 60~90 at%:20~30 at%, or 60~90 at%:30~40 at%; the sputtering atmosphere is argon, and the working pressure is 0.1~0.5 Pa, for example, 0.1~0.2 Pa, 0.2~0.3 Pa, 0.3~0.4 Pa, or 0.4~0.5 Pa; the sputtering power is 5~15 kW, for example, 5~7 kW, 7~9 kW, 9~10 kW, 10~12 kW, or 12~14 kW. kW or 14~15 kW; substrate travel speed is controlled at 5.0~20 m / min, for example 5.0~7 m / min, 7~9 m / min, 9~10 m / min, 10~12 m / min, 12~14 m / min, 14~16 m / min, 16~18 m / min or 18~20 m / min.

[0030] In some embodiments of the present invention, the electroplating solution in step 3) includes nickel sulfate, nickel chloride, boric acid, phosphorous acid, glycine, saccharin, and sodium dodecyl sulfate; the pH of the electroplating solution is 2-6, for example, 2-2.5, 2.5-3, 3-3.5, 3.5-4, 4-5, or 5-6; the foil feeding speed of the electroplating process is 4-20 m / min, for example, 4-6 m / min, 6-8 m / min, 8-10 m / min, 10-12 m / min, 12-14 m / min, 14-16 m / min, 16-18 m / min, or 18-20 m / min; and the current density is 1-15 A / dm³. 3 For example, 1~3A / dm 3 3~5 A / dm 3 5~7 A / dm 3 7~9 A / dm 3 9~10 A / dm 3 10~12A / dm 3 12~14 A / dm 3 Or 14~15 A / dm 3 The temperature is 40~90℃, for example, 40~50℃, 50~60℃, 60~70℃, 70~80℃ or 80~90℃.

[0031] A third aspect of the present invention provides a method for testing the sheet resistance of a peelable buried resistive copper foil as described above, comprising the following steps: S1. Provide a peelable buried resist copper foil as described in any one of claims 1 to 3; S2. Peel off the conductive layer and the release layer to expose the resistive layer. S3. Test the resistance value on the exposed resistive layer surface.

[0032] When the peelable buried resistor copper foil of the present invention consists only of a conductive layer, a release layer, and a resistive layer, it can be designed as a traditional roll sample. When testing the resistance value, ordinary plastic tape, such as PI tape, PET tape, or any tape that makes the adhesion between the resistive layer and the tape greater than 0.5N / mm, can be directly applied to the end of the resistive layer away from the conductive layer. The sheet resistance value of the buried resistor copper foil can be easily tested by simply peeling off the conductive layer, without the need for etching or other related processes on the PCB end, so as to determine whether it meets the requirements.

[0033] The fourth aspect of the present invention provides an application of the above-described peelable buried resist copper foil for the preparation of buried resist copper clad laminates.

[0034] The fifth aspect of this invention provides a method for preparing an embedded resist copper-clad laminate, comprising the following steps: (1) Press the resistive layer of the peelable buried copper foil as described above with the prepreg; (2) Peel off the conductive layer and the release layer to transfer the resistive layer onto the prepreg; (3) The copper foil on the substrate is pressed together with the resistive layer on the prepreg to obtain a copper-clad laminate with buried resistive layer.

[0035] In some embodiments of the present invention, the substrate copper foil is selected from HTE series copper foil, RTF series copper foil, and HVLP series copper foil. It can also be any non-copper foil material compatible with the prepreg to meet the needs of users in different fields.

[0036] The present invention will be further described in detail below with reference to specific embodiments and comparative examples. The described embodiments are only for explaining the present invention and are not intended to limit the scope of protection of the present invention. Experimental methods in the following embodiments that do not specify specific conditions were performed according to conventional experimental conditions in the art.

[0037] In the embodiments of the present invention, the conductive layer 101 is made of copper foil products from Defu Technology.

[0038] Example 1: Preparation of peelable buried resist copper foil without carrier layer 1) Pre-treated 18µm electrolytic copper foil is used. The pretreatment steps include: sequentially performing alkaline washing to remove oil, rinsing with deionized water, and plasma activation treatment to remove oil and impurities from the conductive layer surface and activate the surface microstructure. The plasma activation power is 150~600W, the treatment time is 20~150s, and the activation atmosphere is a mixture of argon and oxygen.

[0039] 2) Coating release layer 201: Preparation of peelable coating: Weigh 100 parts by weight of thermoplastic polyimide resin, add 5 parts by weight of epoxy modified silicone release agent, and 200 parts by weight of N-methylpyrrolidone (NMP) as solvent, and stir at 2000 rpm for 30 minutes using a high-speed disperser to obtain a uniform peelable coating.

[0040] The peelable coating is placed in the surface treatment line groove and applied to the pretreated electrolytic copper foil surface. The coating speed is 10 m / min and the film thickness is controlled at 1 μm.

[0041] 3) Deposition of resistive layer 301: The electrolytic copper foil roll processed in the above steps is loaded into the unwinding system of a multi-chamber continuous magnetron sputtering equipment, and the vacuum is evacuated to a background vacuum level of 1x10⁻¹⁰. -3 Pa~1x10 -5 Pa; The resistive layer was deposited using DC magnetron sputtering: the target material was a nickel-chromium alloy target (Ni:Cr = 80:20 at%), the sputtering atmosphere was high-purity argon (99.999%), the working pressure was set to 0.3 Pa, the sputtering power was 5 kW, and the substrate (i.e., copper foil) travel speed was controlled to 5.0 m / min.

[0042] Using the above process, a nickel-chromium alloy resistor layer 301 with a thickness of 60 ± 5 nm and a sheet resistance of 50 ± 2.5 Ohm / sq is deposited on the release layer 201. Sheet resistance uniformity is monitored online using a four-probe tester, and the intra-wafer non-uniformity is < ±5%. A roll-shaped buried resistive copper foil product without a carrier layer is obtained.

[0043] Example 2: Preparation of peelable buried resist copper foil with carrier layer 1) Use pretreated 18um electrolytic copper foil, and the pretreatment steps are the same as in Example 1.

[0044] 2) Coating release layer 201: Preparation of peelable coating: Weigh 100 parts by weight of thermoplastic polyimide resin, add 5 parts by weight of epoxy modified silicone release agent, and 200 parts by weight of N-methylpyrrolidone (NMP) as solvent, and stir at 2000 rpm for 30 minutes using a high-speed disperser to obtain a uniform peelable coating.

[0045] The peelable coating is placed in the surface treatment line groove and applied to the pretreated electrolytic copper foil surface. The coating speed is 10 m / min and the film thickness is controlled at 1 μm.

[0046] 3) Deposition of resistive layer 301: The electrolytic copper foil roll processed in the above steps is loaded into the unwinding system of a multi-chamber continuous magnetron sputtering equipment, and the vacuum is evacuated to a background vacuum level of 1x10⁻¹⁰. -3 Pa~1x10 -5 Pa; The resistive layer was deposited using DC magnetron sputtering: the target material was a nickel-chromium alloy target (Ni:Cr = 80:20 at%), the sputtering atmosphere was high-purity argon (99.999%), the working pressure was set to 0.3 Pa, the sputtering power was 5 kW, and the substrate (i.e., copper foil) travel speed was controlled to 5.0 m / min.

[0047] Using the above process, a nickel-chromium alloy resistor layer 301 with a thickness of 60 ± 5 nm and a sheet resistance of 50 ± 2.5 Ohm / sq was deposited on the release layer 201. The sheet resistance uniformity was monitored online using a four-probe tester, and the intra-wafer non-uniformity was < ±5%.

[0048] 4) Preparation of carrier layer 401 The carrier layer was deposited using a DC magnetron sputtering process: the target material was a copper target, the sputtering atmosphere was high-purity argon (99.999%), the working pressure was set to 0.3 Pa, the sputtering power was 2 kW, and the substrate (i.e., copper foil) travel speed was controlled to 10 m / min; a carrier layer with a thickness of 10~15 nm was obtained, resulting in a buried resist copper foil product containing carrier layer 401.

[0049] Example 3: Preparation of peelable buried resist copper foil with carrier layer 1) Use pretreated 18um electrolytic copper foil, and the pretreatment steps are the same as in Example 1.

[0050] 2) Coating release layer 201: Preparation of peelable coating: Weigh 100 parts by weight of thermoplastic polyimide resin, add 5 parts by weight of epoxy modified silicone peeling agent, and 200 parts by weight of N-methylpyrrolidone (NMP) as solvent, and stir at 2000 rpm for 30 minutes using a high-speed disperser to obtain a uniform coating.

[0051] The peelable coating is placed in the surface treatment line groove and applied to the pretreated electrolytic copper foil surface. The coating speed is 10 m / min and the film thickness is controlled at 1 μm.

[0052] 3) Deposition of resistive layer 301: The copper foil rolls processed by the above steps are loaded into the electrolytic copper foil surface treatment line.

[0053] The electroplating solution for the nickel-phosphorus resistive layer was prepared using 2000 g of nickel sulfate, 500 g of nickel chloride, 400 g of boric acid, 150 g of phosphorous acid, 50 g of glycine (as a complexing agent to stabilize the plating solution), 15 g of saccharin (as a stress reliever), and 0.5 g of sodium dodecyl sulfate (as a wetting agent to reduce pinholes). The reagents were dissolved in deionized water and stirred thoroughly. The pH was adjusted to 2.0 ± 0.1 with dilute sodium hydroxide solution. The foil feeding speed was 4 m / min, and the current density was 10 A / dm³. 3 The temperature is 60℃.

[0054] Using the above process, a nickel-phosphorus alloy resistor layer 301 with a thickness of 60 ± 5 nm and a sheet resistance of 50 ± 2.5 Ohm / sq was deposited on the release layer 201. The sheet resistance uniformity was monitored online using a four-probe tester, and the intra-wafer non-uniformity was < ±5%.

[0055] 4) Preparation of carrier layer 401 The carrier layer was deposited using a DC magnetron sputtering process: the target material was a copper target, the sputtering atmosphere was high-purity argon (99.999%), the working pressure was set to 0.3 Pa, the sputtering power was 2 kW, and the substrate (i.e., copper foil) travel speed was controlled to 10 m / min; a carrier layer with a thickness of 10~15 nm was obtained, resulting in a buried resist copper foil product containing carrier layer 401.

[0056] Example 4: Preparation of peelable buried resist copper foil with carrier layer 1) 18µm electrolytic copper foil was used, and the pretreatment steps were the same as in Example 1.

[0057] 2) Coating release layer 201: Preparation of peelable coating: Weigh 100 parts by weight of thermoplastic polyimide resin, add 5 parts by weight of epoxy modified silicone peeling agent, and 200 parts by weight of N-methylpyrrolidone (NMP) as solvent, and stir at 2000 rpm for 30 minutes using a high-speed disperser to obtain a uniform coating.

[0058] The peelable coating is placed in the surface treatment line groove and applied to the pretreated electrolytic copper foil surface. The coating speed is 10 m / min and the film thickness is controlled at 1 μm.

[0059] 3) Deposition of resistive layer 301: The copper foil rolls processed by the above steps are loaded into the electrolytic copper foil surface treatment line.

[0060] The electroplating solution for the nickel-phosphorus resistive layer was prepared using 2000 g of nickel sulfate, 500 g of nickel chloride, 400 g of boric acid, 150 g of phosphorous acid, 50 g of glycine, 15 g of saccharin, and 0.5 g of sodium dodecyl sulfate. The reagents were dissolved in deionized water and stirred thoroughly. The pH was adjusted to 2.0 ± 0.1 with dilute sodium hydroxide solution. The foil feeding speed was 4 m / min, and the current density was 10 A / dm³. 3 The temperature is 60℃.

[0061] Using the above process, a nickel-phosphorus alloy resistor layer 301 with a thickness of 60 ± 5 nm and a sheet resistance of 50 ± 2.5 Ohm / sq was deposited on the release layer 201. The sheet resistance uniformity was monitored online using a four-probe tester, and the intra-wafer non-uniformity was < ±5%.

[0062] 4) Preparation of carrier layer 401 The embedded copper foil treated in the above steps is then laminated with standard FR-4 epoxy resin (model S1000-2M from Shengyi Technology). The resistive layer 301 is bonded to the carrier layer 401. Pre-lamination is first performed at 100℃ and a pressure of 5 kgf / cm². 2 The vacuum degree of the press is controlled below 50 Pa, and the pre-pressing time is 10 min. The second step is formal pressing, where full pressure of 25 kgf / cm² is applied when the temperature reaches 100℃, and the temperature is increased from room temperature to 180℃ at a rate of 1.5-2.0℃ / min. The temperature is then held at 180℃ for 90 minutes, maintaining a vacuum throughout. During this process, the FR-4 prepreg is completely cured and firmly bonded to the resistive layer 301, forming a peelable buried resistive copper foil with a carrier.

[0063] Example 5: Direct test method for sheet resistance of resistive layer: S1. The peelable embedded copper foil obtained in Example 1 is cut into any size with an area of ​​5cm×5cm or more.

[0064] S2. Place a piece of tape on the table and attach the resistor layer 301 to the tape.

[0065] S3. Pull the conductive layer 101 upward by hand or at a uniform speed of 300 mm / min. The conductive layer 101 will fall off together with the release layer 201. The surface of the resistive layer 301 after being torn off is smooth and continuous, without any damage or residue.

[0066] S4. Immediately use a four-probe tester (Helper HP2526) to measure the exposed surface of the 301 resistivity layer. Five points were selected at the center and around the sample for measurement. The sheet resistance values ​​were 49.8 Ohm / sq, 50.5 Ohm / sq, 49.5 Ohm / sq, 51.0 Ohm / sq, and 50.2 Ohm / sq. The average value was 50.2 Ohm / sq, which is highly consistent with the nominal value of 50 Ohm / sq and has good uniformity.

[0067] Example 6: Direct test method for sheet resistance of resistive layer: S1. The peelable embedded copper foil obtained in Example 4 is cut into any size with an area of ​​5cm×5cm or more.

[0068] S2. Pull the conductive layer 101 upward by hand or at a uniform speed of 300 mm / min. The conductive layer 101 will fall off together with the release layer 201. The surface of the resistive layer 301 after being torn off is smooth and continuous, without any damage or residue.

[0069] S3. Immediately use a four-probe tester (Helper HP2526) to measure the exposed surface of the 301 resistivity layer. Five points were selected at the center and around the sample for measurement. The sheet resistance values ​​were 49.9 Ohm / sq, 50.4 Ohm / sq, 49.5 Ohm / sq, 50.0 Ohm / sq, and 50.2 Ohm / sq, with an average value of 50 Ohm / sq, which is highly consistent with the nominal value of 50 Ohm / sq and has good uniformity.

[0070] Example 7: Preparation of Customized Embedded Resistor Copper-Clad Boards (1) The peelable buried resist copper foil prepared in Example 1 was laminated with standard FR-4 epoxy resin (model: Shengyi Technology S1000-2M). The resistive layer was bonded to the FR-4 epoxy resin. First, pre-lamination was performed at a temperature of 100°C and a pressure of 5 kgf / cm. 2 The vacuum degree of the press is controlled below 50 Pa, and the pre-pressing time is 10 min. The second step is to perform formal pressing. When the temperature reaches 100℃, full pressure is applied at a pressure of 25 kgf / cm², and the temperature is increased from room temperature to 180℃ at a rate of 1.5-2.0℃ / min. The temperature is held at 180℃ for 90 minutes, and the vacuum is maintained throughout the process. During this process, the FR-4 prepreg is completely cured and firmly bonded to the resistive layer 301. Then, the conductive layer 101 is peeled off, exposing the resistive layer 301.

[0071] (2) Final lamination with the user-selected substrate copper foil Prepare the user-selected substrate copper foil: In this example, it is an 18μm thick ultra-low profile (HVLP) copper foil (Defu Technology). The product with exposed resistive layer 301 obtained in step (1) above is stacked with the substrate copper foil (resistive layer 301 is bonded to the processed surface of the substrate copper foil). This stack is subjected to a standard multilayer board vacuum lamination process: the temperature is raised from room temperature to 180℃ at a rate of 1.5~2.0℃ / min, held at 180℃ for 90 minutes, and the pressure is 30 kgf / cm², with vacuum maintained throughout the process. (3) After lamination, a standard embedded resistor copper-clad board is obtained. During subsequent circuit fabrication, cross-sectional analysis confirmed that the resistor layer 301 was completely and smoothly embedded between the cured prepreg and the base copper foil, with a clear interface and no delamination.

[0072] Comparative Example 1 Comparative Example 1 uses a commercially available traditional buried copper foil of a certain brand (structure: nickel-chromium alloy resistive layer / 18μm bottom foil).

[0073] Testing the sheet resistance of its resistive layer involved first pressing it together with the core board to form a copper-clad laminate. Dry film was then applied to the base foil, exposed, and developed to create a test pattern. The exposed copper was etched away using acidic copper chloride etching solution to form individual resistance strips. Next, an alkaline etching solution was used to create windows to expose the resistive layer. The resistance value of the resistance strips was measured using a multimeter, and the sheet resistance was then calculated. The entire process took over 6 hours and consumed a large amount of auxiliary materials (dry film, chemicals). Ultimately, the test revealed that the sheet resistance exceeded the standard, rendering the entire copper-clad laminate unusable.

[0074] Comparative Example 1 vividly demonstrates the significant advantage of the "pre-testing" approach of this invention.

[0075] Comparative Example 2 Comparative Example 1 uses a commercially available traditional buried copper foil of a certain brand (structure: nickel-chromium alloy resistive layer / 18μm bottom foil).

[0076] Testing the sheet resistance of its resistive layer: First, it was pressed together with the core board to form a copper-clad laminate. Then, an alkaline etching solution was used to etch away the surface copper layer. Finally, a sheet resistance meter was used to measure the specific sheet resistance value. The entire process took 4 hours. The final test revealed that the sheet resistance exceeded the standard, rendering the entire copper-clad laminate unusable. The process consumed a large amount of chemicals, and being in the space containing the chemicals posed a health hazard. This highlights the significant time and safety advantages of this invention, which allows for the peeling off of the embedded resistive copper foil to test the sheet resistance value simply by peeling off the conductive layer.

[0077] In summary, this invention provides a peelable buried resistor copper foil structure that enables direct testing and flexible transfer of the resistor layer. By peeling off the conductive layer 101, the resistor layer 301 can be directly exposed, allowing for direct testing of the sheet resistance value. This achieves rapid, non-destructive testing of the resistor layer performance, fundamentally eliminating quality risks. By transferring the resistor layer 301 and using secondary lamination to form a customized buried resistor copper-clad laminate with a user-customized copper foil, the "decoupling" of the resistor layer product from the substrate copper foil is achieved, greatly enhancing product design flexibility and supply chain autonomy.

[0078] Therefore, this invention effectively overcomes the various shortcomings of the prior art and has high industrial application value.

[0079] It should be noted that the illustrations provided in this embodiment are only schematic representations of the basic concept of the present invention. Therefore, the drawings only show the components related to the present invention and are not drawn according to the actual number, shape and size of the components in the actual implementation. In the actual implementation, the form, quantity and proportion of each component can be arbitrarily changed, and the layout of the components may also be more complex.

[0080] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the invention. Any person skilled in the art can modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by those skilled in the art without departing from the spirit and technical concept disclosed in the present invention should still be covered by the claims of the present invention.

Claims

1. A peelable buried resist copper foil, characterized in that, From bottom to top, it includes: a conductive layer (101), a release layer (201), and a resistive layer (301).

2. The peelable buried resist copper foil according to claim 1, characterized in that, A carrier layer (401) is also provided above the resistive layer (301).

3. The peelable buried resist copper foil according to claim 2, characterized in that, It also includes one or more of the following features: a1) The conductive layer (101) is an electrolytic copper foil; a2) The raw material of the release layer (201) is selected from one or more of the following: silicone-modified acrylic acid, water-based acrylic resin, UV-curable peelable adhesive, thermoplastic polyimide resin, and polyethylene terephthalate. a3) The sheet resistance of the resistive layer (301) is 10Ω / sq to 1000Ω / sq; a4) The material of the carrier layer (401) is selected from one or more of the following: resin adhesive, polyimide, modified polyimide, fiberglass cloth, fiberglass cloth composite material, paper substrate, composite substrate, HDI board, modified epoxy resin, modified acrylic resin, polyethylene terephthalate, polybutylene terephthalate, and polyethylene; or, the carrier layer (401) is an extremely thin metal layer with a thickness of 10~500nm.

4. A method for preparing a peelable buried resist copper foil according to any one of claims 1 to 3, characterized in that, Includes the following steps: 1) Pre-treat the surface of the conductive layer (101); 2) Prepare a peelable coating and apply the peelable coating to the pretreated conductive layer (101) to form a peelable layer (201). 3) A resistive layer (301) is deposited on the surface of the release layer (301) by DC magnetron sputtering or by electroplating the resistive layer (301) on the surface of the release layer (301) to obtain a peelable buried resistive copper foil.

5. The method for preparing peelable buried resist copper foil according to claim 4, characterized in that, It also includes one or more of the following features: b1) The pretreatment steps in step 2) include: sequentially performing alkaline washing to remove oil, rinsing with deionized water, and plasma activation treatment on the material of the conductive layer (101); b2) The peelable buried copper foil in step 2) also includes a carrier layer (401), which is obtained by deposition on the surface of the resistor layer (301) using a DC magnetron sputtering process; b3) The preparation of the peelable coating in step 2) includes the following steps: weigh the raw material of the peelable layer (201) and dissolve it in a solvent, and stir at high speed to obtain a uniform peelable coating. The solvent is N-methylpyrrolidone.

6. The method for preparing peelable buried resist copper foil according to claim 4, characterized in that, In step 3), the target material for the DC magnetron sputtering process is a nickel-chromium alloy target with Ni:Cr = 60~90 at%:10~40 at%, the sputtering atmosphere is argon, the working pressure is 0.1~0.5 Pa, the sputtering power is 5~15 kW, and the substrate travel speed is controlled at 5.0~20 m / min. Alternatively, the electroplating solution in step 3) includes nickel sulfate, nickel chloride, boric acid, phosphorous acid, glycine, saccharin, and sodium dodecyl sulfate; the pH of the electroplating solution is 2-6; the foil feeding speed of the electroplating process is 4-20 m / min, and the current density is 1-15 A / dm. 3 The temperature is 40~90℃.

7. A method for testing the sheet resistance of a peelable buried resistive copper foil as described in any one of claims 1 to 3, characterized in that, Includes the following steps: S1. Provide a peelable buried resist copper foil as described in any one of claims 1 to 3; S2. Peel off the conductive layer (101) and the release layer (201) to expose the resistive layer (301) of the product. S3. Test the sheet resistance on the exposed resistive layer (301) surface.

8. An application of the peelable buried resist copper foil as described in any one of claims 1 to 3, characterized in that, Used to prepare buried resist copper-clad laminates.

9. A method for preparing an embedded resist copper-clad laminate, characterized in that, Includes the following steps: (1) Press the resistive layer (301) of the peelable buried copper foil as described in any one of claims 1 to 3 with a prepreg; (2) Peel off the conductive layer (101) and the release layer (201) to transfer the resistive layer (301) onto the prepreg; (3) The copper foil on the substrate is pressed together with the resistive layer (301) on the prepreg to obtain a copper-clad buried resistive layer.

10. The method for preparing buried resist copper-clad laminate according to claim 9, characterized in that, The base copper foil is selected from one of the HTE series copper foil, RTF series copper foil, and HVLP series copper foil.

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