Resistance conductive material as well as preparation method and application thereof

Abstract

The invention relates to a resistance conductive material as well as a preparation method and application thereof. The resistance conductive material comprises a copper foil layer, a transition layer and a resistance layer from bottom to top, the resistance layer comprises a dispersion reinforcing phase and a homogeneous phase; the dispersion enhancing phase is subjected to surface pretreatment before being added into the electroplating liquid. According to the invention, the transition layer and the dispersion reinforcing phase are introduced, the diffusion of copper into the resistance layer is inhibited through the synergistic effect of the transition layer and the dispersion reinforcing phase, the high resistivity of the resistance layer is maintained, and the application prospect is good.

Description

Technical Field

[0001] The present invention belongs to the technical field of electronic materials, and particularly relates to a resistive conductive material, a preparation method thereof, and an application thereof. Background Art

[0002] With the rapid development of the electronic information industry, printed circuit boards (PCBs) are developing towards high density, multi-layer, easy encapsulation, and miniaturization. Considering the reliability of PCB assembly, the stability and electrical performance of resistive devices, the embedding of resistive devices is very necessary, and the emergence of buried resistor copper foils has well solved this problem.

[0003] Currently, commercial buried resistor copper foils are usually prepared by attaching a resistive material on a copper foil substrate by electroplating or vacuum sputtering. The resistive materials include binary metal alloys, ternary metal alloys, and even quaternary alloy materials. Since these alloy materials all contain metal components, their resistivity is not high, usually less than 1×10 -3 Ω·cm. The power load per unit area (unit: W / in 2 ) and the antistatic discharge ability (ESD, unit: V) are both related to the resistivity of the material. When the sheet resistance R □ is certain, according to R □ =ρ / d, the larger the resistivity ρ, the larger the size d of the resistor, and the stronger the power load and ESD of the resistor.

[0004] During the production of buried resistor PCBs, chemical etching needs to be continuously carried out to obtain the resistor pattern, and the sheet resistance R □ of the resistor layer will inevitably be affected by etching. Making a barrier layer between the copper foil and the resistor layer can well protect the resistor layer from being affected by etching. However, the resistivity of the alloy materials used in the resistor layer is already not high, and the resistivity of the barrier layer is lower than that of the resistor layer. Once the barrier layer is added, the resistivity will be further reduced. Therefore, in order to obtain a stable buried resistor device, it is necessary to solve the problems of low resistivity and poor chemical etching resistance of existing resistive materials. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide a resistive conductive material, a preparation method thereof, and an application thereof. The resistive conductive material not only has a very high resistivity (greater than 3×10 -3 Ω·cm), but also has excellent etching resistance to etching solution.

[0006] The present invention provides a resistive conductive material, which comprises a copper foil layer, a transition layer, and a resistor layer from bottom to top; the resistor layer comprises a dispersion strengthened phase and a homogeneous phase; the dispersion strengthened phase is subjected to surface pretreatment before being added to the electroplating solution.

[0007] Preferably, the transition layer contains one or more elements of tin, nickel, zinc, chromium, oxygen, phosphorus, carbon, nitrogen, aluminum, titanium, silicon, cobalt, and contains at least one metal element.

[0008] Preferably, the thickness of the transition layer is 5 - 30 nm.

[0009] Preferably, the ratio of the surface roughness Ra of the side of the transition layer close to the copper foil layer to the thickness of the transition layer is between 30 - 600.

[0010] Preferably, the thickness of the resistance layer is 0.05 - 1 μm. The resistance layer and the copper foil layer can be electrically conducted.

[0011] Preferably, the dispersion strengthening phase is a metal oxide, a non - metal oxide or a ferrite; the homogeneous phase is a nickel - phosphorus alloy.

[0012] Further, the mass m 1 of the dispersion strengthening phase accounts for 2 15% - 35% of the total mass m of the resistance layer, and the ratio fluctuation does not exceed ±10%.

[0013] Further, in the nickel - phosphorus alloy, the phosphorus content is greater than 12 wt%.

[0014] Preferably, the dispersion strengthening phase includes one or more of silicon dioxide, boron oxide, zinc oxide, magnesium oxide, bismuth oxide, aluminum oxide, titanium dioxide, nickel oxide, tungsten oxide, cobalt oxide, copper oxide, chromium oxide, manganese oxide, zirconium oxide, zinc ferrite, magnetic iron oxide, nickel - zinc ferrite, copper - zinc ferrite.

[0015] Further, on the side of the resistance layer away from the transition layer, metal clusters are distributed, and the components of the metal clusters are nickel and phosphorus.

[0016] Further, on the side of the resistance layer away from the transition layer, there is no dispersion strengthening phase distributed within a depth of 15 nm from the surface, and the dispersion strengthening phase is distributed in the homogeneous phase in the form of particles or clusters.

[0017] Further, on the side of the resistance layer away from the transition layer, the surface roughness Ra is between 1.0 - 3.0 μm, and Sdr is between 50% - 300%.

[0018] The present invention also provides a preparation method of a resistive conductive material, comprising the following steps:

[0019] S1. Prepare a copper foil layer;

[0020] S2. Prepare a transition layer on the copper foil layer;

[0021] S3. Prepare the electroplating solution used for the resistance layer;

[0022] S4. Electroplate on the transition layer using the above electroplating solution to obtain a resistive conductive material.

[0023] Further, in step S1, an existing copper foil production technology is used to prepare the copper foil layer. The existing production technologies include electrolysis and rolling, and the nominal thickness of the final copper foil layer is between 5 - 200 μm.

[0024] Further, in step S2, a transition layer is prepared on the copper foil layer by chemical methods or physical methods. Chemical methods include electroplating, electroless plating, chemical vapor deposition, etc., and physical methods include vacuum evaporation plating, ion plating, magnetron sputtering, etc.

[0025] Further, the composition of the electroplating solution in step S3 includes a nickel source, a phosphorus source, a stabilizer, a buffer, a pH regulator, an additive, and a dispersion strengthening phase. Among them, the nickel source is calculated by the concentration of nickel atoms and is 15 - 50 g / L; the phosphorus source is calculated by the concentration of phosphorus atoms and is 8 - 15 g / L; the concentration of the stabilizer is 0.1 - 5 g / L; the concentration of the buffer is 10 - 100 g / L; the concentration of the additive is 0.05 - 2 g / L; the concentration of the dispersion strengthening phase is 0.3 - 1 g / L; the concentration of the pH regulator can vary dynamically according to the actual pH of the electroplating solution, and the final pH of the electroplating solution is 1.5 - 3.

[0026] Further, the nickel source includes one or more of nickel sulfamate, nickel sulfate, nickel chloride, nickel carbonate, etc.; the phosphorus source includes one or more of sodium hypophosphite, phosphorous acid, hypophosphorous acid, etc.; the stabilizer includes one or more of thiourea, sodium acetate, sodium thiosulfate, potassium iodide, ethylenediaminetetraacetic acid, methyltetrahydrophthalic anhydride, etc.; the buffer includes one or more of boric acid, phosphoric acid, citric acid, lactic acid, malic acid, tartaric acid, etc.; the pH regulator includes one or more of sulfuric acid, ammonia water, sodium hydroxide, potassium hydroxide, etc.; the additive includes one or more of sodium dodecyl sulfate, sodium dodecylbenzenesulfonate, 2 - ethylhexyl sulfate, polyethylene glycol, sodium tungstate, saccharin, etc.

[0027] Further, the particle size D of the dispersion strengthening phase 90 is between 30 - 90 nm, and D 50 is between 15 - 48 nm, and the specific surface area is between 50 - 300 m 2 / g.

[0028] Further, a mixed solution of polyol and water is used as the solvent, and a surfactant is used as the treatment agent to perform surface pretreatment on the added dispersion strengthening phase.

[0029] Further, the polyol includes one or more of ethylene glycol, glycerol, diethylene glycol, pentaerythritol, butanediol, triethanolamine, xylitol, sorbitol, neopentyl glycol; the surfactant includes one or more of CTAB, cationic polyacrylamide, cetylpyridinium ammonium, cetyltrimethylammonium chloride, vinylpyrrolidone, tetradecyl-dimethylpyridinium bromide, the condensate of epichlorohydrin and ethylenediamine, dimethyldiallylammonium chloride, diethylaminoethyl acrylate; wherein the mass ratio of the polyol in the alcohol-water mixed solution is greater than 50%.

[0030] Further, add 1 - 10 g of the dispersion strengthening phase into the mixed solution of polyol and water, and ultrasonically stir for 0.5 - 2 h; then add the surfactant into the mixed solution and continue ultrasonically stirring for 1 - 5 h, maintaining the solution temperature at 30 - 60 °C, and the weight ratio of the dispersion strengthening phase to the surfactant is 1:5 - 1:15.

[0031] Further, after the surface pretreatment of the dispersion strengthening phase is completed, separate it using a high-speed centrifuge, wash it successively with ethanol and water, and finally dry it in vacuum at a drying temperature of 80 °C.

[0032] Further, add the treated dispersion strengthening phase into the electroplating solution, and introduce air into the electroplating solution to fully disperse each component in the electroplating solution, with an air flow rate of 0.5 - 5 m 3 / min.

[0033] Further, the electroplating in step S4 is as follows: using a DSA titanium material as the anode, a copper foil as the cathode opposite to the anode, wherein the copper foil is fixed on an insulating substrate, the electroplating solution temperature is 30 - 60 °C, the current density is 0.5 - 20 A / dm 2 , and the electroplating method is pulse electroplating with a duty cycle of 30% - 100%.

[0034] The present invention also provides an application of a resistive conductive material in the preparation of a copper clad laminate, including the following steps:

[0035] S5. Press the resistive conductive material and a prepreg (PP) to obtain a copper clad laminate material (FCCL);

[0036] S6. Etch and perform performance tests on the pressed FCCL.

[0037] Further, before pressing in step S5, wash the obtained resistive conductive material clean, dry it at 80 °C with hot air, and then press the side with the resistive layer against the prepreg.

[0038] Further, the prepreg includes epoxy resin-based PP, hydrocarbon resin-based PP, PTFE resin-based PP, PPO / PPE resin-based PP, bismaleimide (BMI) and polymaleimide resin-based PP, LCP liquid crystal polymer, cyanate resin-based PP, ABF resin-based PP, phenolic resin-based PP, etc.

[0039] Further, in step S6, the pressed resist conductive material is etched, and the copper foil layer and the transition layer are completely etched and dissolved, and the remaining resist layer adheres tightly to the cured PP board.

[0040] Further, the etching solution is preferably an alkaline copper ammonia etching solution.

[0041] Further, in step S6, an XRF thickness gauge is used to measure the thickness of the resist layer, and a surface resistance meter is used to test the surface resistance of the resist layer, and the resistivity of the resist layer is calculated.

[0042] Further, in step S6, the surface resistance of the resist layer at different etching times is tested to obtain the etching resistance of the resist layer.

[0043] Beneficial effects

[0044] In the present invention, a dispersion strengthening phase is added to the resist layer. The dispersion strengthening phase has a nanoscale size and is distributed in the nickel-phosphorus homogeneous phase in the form of particles or clusters, playing the role of an anchoring site, inhibiting the diffusion of defects in the homogeneous phase, cutting off the intrusion path of the etching solution into the resist layer, and improving the etching resistance of the resist layer; and the dispersion strengthening phase belongs to an insulator and does not have conductivity, which can hinder the transmission of electrons, extend the transmission path of electrons, and increase the resistivity of the resist layer; secondly, the copper foil layer is prone to diffusion reaction with the resist layer, and the introduction of the transition layer and the dispersion strengthening phase, through their synergistic effect, inhibits the diffusion of copper into the resist layer, maintains the high resistivity of the resist layer, and has good application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] Figure 1 is a schematic structural diagram of the resist conductive material of the present invention;

[0046] Figure 2 is a partially enlarged schematic structural diagram of the resist conductive material of the present invention;

[0047] Figure 3 is a schematic structural diagram of the pressed resist conductive material;

[0048] Figure 4 is a schematic structural diagram of the etched resist conductive material. DETAILED DESCRIPTION OF THE INVENTION

[0049] The present invention will be further described below in conjunction with specific embodiments. It should be understood that these embodiments are only used to illustrate the present invention and not to limit the scope of the present invention. In addition, it 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 also fall within the scope defined by the appended claims of this application.

[0050] Example 1

[0051] Step S1:

[0052] Copper foil is obtained by electrolysis and its surface is treated. The nominal thickness of the copper foil is 18 μm.

[0053] Step S2:

[0054] Electroless nickel-tin alloy is plated on the matte surface of the copper foil as a transition layer, where the mass fraction of tin is 60%, the total thickness of the transition layer is 15 nm, and the roughness Ra = 0.9 μm.

[0055] Step S3:

[0056] 1) First, prepare a pretreatment solution for the dispersion strengthening phase. Mix ethylene glycol, diethylene glycol, and water to obtain an aqueous polyol solution. The total mass is calculated according to 100 mass parts, and the mass ratio of the above three components is 40:15:45. Stir evenly and set aside;

[0057] 2) Secondly, take 1 g of nickel oxide as the dispersion strengthening phase, with a particle size D 90 = 80 nm, D 50 = 42 nm, and a specific surface area of 235 m 2 / g, and add it to the above aqueous polyol solution. Ultrasonically stir for 1 h;

[0058] 3) To the above polyol solution, continue to add 5 g of CTAB, and continue to ultrasonically stir for 2 h. Maintain the temperature at 30 °C in a water bath;

[0059] 4) Centrifuge to separate nickel oxide, wash it successively with ethanol and deionized water, and place it in a vacuum drying oven at 80 °C for 2 h of drying;

[0060] 5) Prepare a nickel-phosphorus electroplating solution. The nickel source is nickel sulfate, the phosphorus source is phosphorous acid, the stabilizer is thiourea, the buffer is phosphoric acid, and the additive is sodium dodecyl sulfate. Use sulfuric acid and sodium hydroxide to adjust the pH of the solution. The specific concentrations are: nickel sulfate 120 g / L, phosphorous acid 25 g / L, thiourea 0.2 g / L, phosphoric acid 40 g / L, sodium dodecyl sulfate 0.05 g / L, and the pH of the solution is 2.0;

[0061] 6) Add the dried nickel oxide to the nickel - phosphorus electroplating solution at a concentration of 0.6 g / L, and while stirring, introduce air with an air flow rate of 0.5 m³ / min to obtain the electroplating solution.

[0062] Step S4:

[0063] Use a DSA titanium material as the anode and a copper foil as the cathode, where the copper foil is fixed on an insulating substrate. The temperature of the electroplating solution is 30 °C, and the current density is 0.5 A / dm 2 , Pulse - energize for 20 min with a duty cycle of 90% to obtain a resistive conductive material. The surface roughness Ra of the surface of the resistive layer away from the transition layer is 1.05 μm, and sdr = 55%.

[0064] Step S5:

[0065] Remove the obtained resistive conductive material from the substrate, wash it clean with water, dry it at 80 °C, and then tightly press - laminate its resistive layer with an FR4 prepreg. The lamination temperature is 200 °C, and the lamination time is 3 h.

[0066] Step S6:

[0067] Place the press - laminated resistive conductive material horizontally on the sample stage, and use the multi - point spraying method to horizontally etch the copper foil layer and the transition layer of the resistive conductive material. The horizontal moving speed of the sample stage is 5 m / min; after etching is completed, the resistive layer is completely exposed. Measure the thickness of the resistive layer and test the sheet resistance of the resistive layer at different etching times.

[0068] Example 2

[0069] Differing from Example 1, in Step S3, use the same weight of tungsten oxide as the dispersion strengthening phase, with particle sizes D 90 = 85 nm, D 50 = 40 nm, and a specific surface area of 220 m 2 / g.

[0070] Example 3

[0071] Differing from Example 1, in Step S3, use the same weight of titanium dioxide as the dispersion strengthening phase, with particle sizes D 90 = 90 nm, D 50 = 48 nm, and a specific surface area of 215 m 2 / g.

[0072] Example 4

[0073] Differing from Example 1, in Step S3, use the same weight of silicon dioxide as the dispersion strengthening phase, with particle sizes D 90 = 40 nm, D 50 = 25 nm, and a specific surface area of 290 m2 / g.

[0074] Example 5

[0075] Different from Example 1, in step S3, bismuth oxide of the same weight is used as the dispersion strengthening phase, and the particle sizes D 90 = 78 nm, D 50 = 36 nm, and the specific surface area is 250 m 2 / g.

[0076] Example 6

[0077] Different from Example 1, in step S3, zinc ferrite of the same weight is used as the dispersion strengthening phase, and the particle sizes D 90 = 86 nm, D 50 = 40 nm, and the specific surface area is 186 m 2 / g.

[0078] Example 7

[0079] Different from Example 1, in step S3, a pretreatment solution of the dispersion strengthening phase is prepared, and the polyols used are ethylene glycol, sorbitol, and water, with a mass ratio of 35:20:45, and other conditions are the same as those in Example 1.

[0080] Example 8

[0081] Different from Example 1, in step S3, the surfactant is vinylpyrrolidone.

[0082] Example 9

[0083] Different from Example 1, in step S2, a nickel-carbon alloy is used as the transition layer on the matte surface of the copper foil, where the mass fraction of nickel is 92%, the total thickness of the transition layer is 15 nm, and the roughness Ra = 0.88 μm.

[0084] Comparative Example 1

[0085] Different from Example 1, in step S3, no dispersion strengthening phase is added.

[0086] Comparative Example 2

[0087] Different from Example 1, in step S3, after the dispersion strengthening phase is fully dispersed in the alcohol-water mixed solution, no surfactant is used for subsequent surface treatment of the dispersion strengthening phase.

[0088] Comparative Example 3

[0089] Different from Example 1, in step S3, the mass fraction ratio of ethylene glycol, diethylene glycol, and water is 30:15:55, and other conditions are the same as those in Example 1.

[0090] Comparative Example 4

[0091] Different from Example 1, in step S3, the electroplating conditions were as follows: the temperature of the electroplating solution was 30°C, the current density was 0.5 A / dm 2 , pulsed power was applied for 20 min, and the duty cycle was 25%.

[0092] Comparative Example 5

[0093] Different from Example 1, the resistive conductive material did not have a transition layer.

[0094] To more intuitively reflect the effects of the present invention, the same pressing plate, etching, and testing procedures (steps S5 and S6) were used for all examples and comparative examples. The specific test data are shown in Table 1.

[0095]

[0096]

[0097] To more clearly highlight the beneficial effects of the present invention, the following provides a detailed description of the examples and comparative examples.

[0098] Comparing Comparative Example 1 with Example 1, if no dispersion strengthening phase is added to the resistive layer, the resistivity will be very low, only 0.5×10 -3 Ω·cm, and the change rate of the resistivity within 12 min is 540%, and the resistivity is very unstable. Such a resistive conductive material has no practical use value. Comparing Comparative Example 2 with Example 1, without using a surfactant to treat the surface of the dispersion strengthening phase, the mass ratio of the dispersion strengthening phase in the resistive layer is only 7.8%, and the resistivity of the resistive layer is only 1.5×10 -3 Ω·cm, and the change rate of the resistivity also reaches 113%, which is relatively unstable. Comparing Comparative Example 3 with Example 1, the mass ratio of polyol is less than 50%, and the dispersion strengthening phase cannot be fully dispersed, affecting the final resistivity. Comparing Comparative Example 4 with Example 1, reducing the duty cycle reduces the thickness of the resistive layer, and the incorporation amount of the dispersion strengthening phase also decreases to 10% by mass, and the resistivity decreases to 1.8×10 -3 Ω·cm. Comparing Comparative Example 5 with Example 1, without a transition layer, the change rate of the resistivity increases from 10.4% to 20%, which is because the copper element in the copper foil layer diffuses into the resistive layer.

[0099] Comparing Examples 2, 3, and 5 with Example 1, it can be seen that replacing nickel oxide with other substances, such as tungsten oxide, titanium dioxide, and bismuth oxide, can also achieve the effect of increasing resistivity. Comparing Example 4 with Example 1, the specific surface area of the dispersion strengthening phase is the largest, which is beneficial to the dispersion of the dispersion strengthening phase in the plating solution, and then increases its proportion in the resistance layer, and the resistivity also reaches the maximum of 5.3×10 -3 Ω·cm. Comparing Example 6 with Example 1, the specific surface area of zinc ferrite is small, which is not conducive to dispersion in the plating solution, so its resistivity is the lowest among all examples. Comparing Example 7 with Example 1, using sorbitol instead of diethylene glycol and adjusting the ratio can also achieve the effect of increasing resistivity, and the change rate of resistivity is also relatively good. Comparing Example 8 with Example 1, using vinylpyrrolidone instead of CTAB also has a good effect. Comparing Example 9 with Example 1, the composition of the transition layer has changed, and the resistivity has increased slightly. When the etching time is 12 min, the change rate of resistivity drops to 7.69%.

[0100] Note that the above is only the preferred embodiment of the embodiments of the present invention and the technical principles applied. Those skilled in the art will understand that the embodiments of the present invention are not limited to the specific embodiments described here. Various obvious changes, re-adjustments, and substitutions can be made by those skilled in the art without departing from the protection scope of the embodiments of the present invention. Therefore, although the embodiments of the present invention have been described in more detail through the above embodiments, the embodiments of the present invention are not limited to the above embodiments. Without departing from the concept of the embodiments of the present invention, more other equivalent embodiments can be included, and the scope of the embodiments of the present invention is determined by the scope of the appended claims.

Claims

1. A resistive conductive material, characterized in that: The resistive conductive material comprises a copper foil layer, a transition layer and a resistor layer from bottom to top; the resistor layer comprises a dispersed enhanced phase and a homogeneous phase; the dispersed enhanced phase is subjected to surface pretreatment before being added into the electroplating solution.

2. The resistive conductive material according to claim 1, characterized in that: The transition layer contains one or more elements of tin, nickel, zinc, chromium, oxygen, phosphorus, carbon, nitrogen, aluminum, titanium, silicon, and cobalt, and contains at least one metal element; the thickness of the transition layer is 5-30nm; the thickness of the resistance layer is 0.05-1μm.

3. The resistive conductive material according to claim 1, characterized in that: The dispersed reinforcement phase is metal oxide, non-metal oxide or ferrite; the homogeneous phase is nickel-phosphorus alloy.

4. The resistive conductive material according to claim 1 or 3, characterized in that: The dispersion reinforcement phase includes one or more of silicon dioxide, boron oxide, zinc oxide, magnesium oxide, bismuth oxide, aluminum oxide, titanium dioxide, nickel oxide, tungsten oxide, cobalt oxide, copper oxide, chromium oxide, manganese oxide, zirconium oxide, zinc ferrite, magnetic iron oxide, nickel zinc ferrite, and copper zinc ferrite.

5. The resistive conductive material according to claim 1, characterized in that: The mixed solution of polyol and water is used as solvent and the surfactant is used as treating agent to pre-treat the surface of the dispersion reinforcement phase.

6. The resistive conductive material according to claim 1, characterized in that: Metal clusters are distributed on the surface of the resistance layer away from the transition layer.

7. A method for preparing the resistive conductive material as claimed in claim 1, comprising the following steps: S1. Preparing a copper foil layer; S2. Preparing a transition layer on the copper foil layer; S3. Prepare the plating solution used for the resistor layer; S4. Electroplating is performed on the transition layer using the above electroplating solution to obtain a resistive conductive material.

8. The preparation method according to claim 7, characterized in that: The electroplating solution in step S3 comprises a nickel source, a phosphorus source, a stabilizer, a buffer, a pH regulator, an additive and a dispersion enhancement phase.

9. The preparation method according to claim 8, characterized in that: The nickel source includes one or more of nickel sulfamate, nickel sulfate, nickel chloride, and nickel carbonate; the phosphorus source includes one or more of sodium hypophosphite, phosphorous acid, and hypophosphorous acid; the stabilizer includes one or more of thiourea, sodium acetate, sodium thiosulfate, potassium iodide, ethylenediaminetetraacetic acid, and methyltetrahydrophthalic anhydride; the buffer includes one or more of boric acid, phosphoric acid, citric acid, lactic acid, malic acid, and tartaric acid; the pH adjuster includes one or more of sulfuric acid, ammonia water, sodium hydroxide, and potassium hydroxide; the additive includes one or more of sodium dodecyl sulfate, sodium dodecylbenzene sulfonate, sodium 2-ethylhexyl sulfate, polyethylene glycol, sodium tungstate, and saccharin.

10. Use of the resistive conductive material according to claim 1 in preparing a copper clad laminate.

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