A conductive sheet and its preparation method
By combining chain-bead-shaped nickel powder conductive particles with a resin matrix, the problem of foreign monopoly on precious metal dendritic conductive microparticles has been solved, achieving low resistance and good conductivity stability, which has broad application value.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- ZHUHAI YUNENG TECHNOLOGY CO LTD
- Filing Date
- 2022-11-03
- Publication Date
- 2026-07-17
AI Technical Summary
In the existing technology, the precious metal dendritic conductive microparticles are monopolized by foreign countries, resulting in high costs and limited applications. At the same time, ordinary conductive particles are unevenly distributed after hot pressing, which affects the conductivity.
A conductive film is formed by mixing chain-bead-shaped nickel powder conductive particles with a resin matrix through vacuum mixing, achieving low resistance without the use of precious metals. The particle morphology is controlled by multi-walled carbon nanotube nucleating agents to prepare conductive sheets.
It achieves low resistance and good conductivity stability, breaking the monopoly of precious metals, and has similar conductivity properties to precious metals, but at a lower cost.
Abstract
Description
Technical Field
[0001] This invention belongs to the field of electronic component materials technology, specifically relating to a conductive sheet and its preparation method. Background Technology
[0002] With the rapid development of the electronics industry, electronic products are increasingly miniaturizing, lightweighting, and assembling with high density, greatly promoting the development of flexible printed circuit boards (PCBs). As a special component that connects electronic components and integrates component devices and wire connections, flexible printed circuit boards possess excellent properties such as lightness, thinness, diverse structures, and bending resistance, and can be widely used in mobile phones, LCD displays, and other fields. These flexible printed circuit boards utilize various conductive sheets to achieve high functionality.
[0003] To achieve flexible connections, conductive sheets primarily utilize conductive adhesives to achieve conductive interconnects. These adhesives typically consist of conductive fillers, a resin matrix, and additives. The resin matrix mainly serves as a binder and includes epoxy resin, acrylic resin, urethane resin, silicone rubber resin, bismaleimide resin, phenolic resin, melamine resin, and polyimide resin. Conductive fillers are used to form conductive pathways and can be made of materials such as carbon powder, silver powder, copper powder, nickel powder, solder powder, aluminum powder, silver-plated copper powder, and metal-plated resin balls.
[0004] Currently, achieving better conductivity through conductive particles of specific shapes has been extensively studied. Patent CN206134279U discloses a conductive adhesive film with irregularly shaped metal particles. The conductive adhesive layer includes an adhesive resin layer and several metal conductive particles embedded in the adhesive resin layer. The shapes of the metal conductive particles are dendritic, needle-like, sheet-like, and spherical, and at least two of these shapes are present. The particle size of the metal conductive particles is 2-22 μm. Because the metal conductive particles have various shapes, they tend to flow in multiple directions when deformed by hot pressing. This results in a multi-directional and highly dispersed distribution of the metal conductive particles in the conductive adhesive layer after pressing, thereby forming a conductive circuit with the grounding holes on the flexible circuit board. This gives the conductive adhesive layer excellent anisotropic conductivity, significantly improving conductivity and reducing the grounding impedance of the flexible circuit board. However, high-quality irregularly shaped conductive particles are largely monopolized by foreign countries, and their raw material sources are limited.
[0005] Dendritic conductive microparticles, especially those with a copper core and a silver coating, have been widely used. For example, a conductive sheet described in patent CN 103597551 A uses copper as the core of dendritic conductive microparticles, with a silver coating formed on the surface of this core; the silver coating accounts for more than 1% and less than 40% by weight of 100% by weight of the dendritic conductive microparticles (B). However, these dendritic conductive microparticles require the use of the precious metal silver, resulting in high costs; furthermore, the raw material source for these dendritic particles is monopolized by foreign countries, limiting their application. Summary of the Invention
[0006] In order to break the foreign monopoly on precious metal dendritic particles and achieve low resistance and performance without the need for precious metals such as silver plating, the primary objective of this invention is to provide a conductive sheet.
[0007] Another object of the present invention is to provide a method for preparing the above-mentioned conductive sheet.
[0008] The objective of this invention is achieved through the following technical solution:
[0009] A conductive sheet includes a conductive film layer, the conductive film layer comprising a resin matrix and chain-like nickel powder conductive particles distributed in the resin matrix;
[0010] The thickness of the conductive film and the particle size of the chain-bead nickel powder conductive particles satisfy the following conditions (I) and (II):
[0011] (I) The thickness of the conductive layer after being heated and pressed with the substrate at 150℃, 2MPa and 30min is 25 to 70:100 compared with the thickness of the conductive layer before heating and pressing.
[0012] (II) The average particle size D of the chain-bead nickel powder conductive particles 50 The thickness is less than 0.5 times that of the conductive film layer.
[0013] Furthermore, the average particle size D of the chain-bead nickel powder conductive particles 50 The particle size is 3–50 μm; and the weight percentage of the chain-bead-shaped nickel powder conductive particles in the conductive film layer is 50%–90%.
[0014] Furthermore, the average particle size D of the chain-bead nickel powder conductive particles 90 The average particle size D 50 1.5 to 5 times that.
[0015] Furthermore, the apparent density of the chain-like nickel powder conductive particles is 0.3–1.2 g / cm³. 3 .
[0016] Furthermore, the resin matrix is a thermosetting phenolic resin, epoxy resin, urethane resin, melamine resin, alkyd resin, or polyimide resin.
[0017] Furthermore, one side of the conductive film layer is covered with an insulating protective film layer, and the other side is attached with a reinforcing steel sheet.
[0018] The method for preparing the above-mentioned conductive sheet includes the following preparation steps:
[0019] (1) The chain-bead-shaped nickel powder conductive particles and the resin matrix are mixed evenly under vacuum to obtain a conductive adhesive.
[0020] (2) Apply a pressure of less than 2MPa and a temperature of less than 150°C to the conductive adhesive obtained in step (1) and attach it to the reinforcing steel sheet to form a steel sheet with a conductive film layer. Then, attach an insulating protective film layer to the conductive film layer to obtain a conductive sheet.
[0021] Furthermore, the chain-bead-shaped nickel powder conductive particles are prepared by the following method:
[0022] Soluble nickel salts are dissolved evenly in water, and then the temperature is raised to 50-80°C. Oxalic acid or ammonium oxalate precipitant and carbon nanotube nucleating agent are added under stirring to react. The resulting precipitate is washed, dried, and then thermally decomposed under vacuum or protective atmosphere at 300-600°C to obtain chain-bead-shaped conductive nickel powder particles.
[0023] Furthermore, the soluble nickel salt is at least one of nickel chloride, nickel sulfate, and nickel nitrate.
[0024] Furthermore, the carbon nanotube nucleating agent uses multi-walled carbon nanotubes with a diameter of 10–100 nm and an aspect ratio of 100–2000.
[0025] Compared with the prior art, the beneficial effects of the present invention are:
[0026] The conductive sheet of this invention uses specific chain-bead-shaped nickel powder conductive particles, achieving low resistance and performance without using silver-plated copper core dendritic conductive microparticles. This breaks the foreign monopoly on high-conductivity precious metal dendritic particles and has good application value. Detailed Implementation
[0027] The present invention will be further described in detail below with reference to embodiments, but the implementation of the present invention is not limited thereto.
[0028] Example 1
[0029] A conductive sheet according to this embodiment is prepared by the following method:
[0030] (1) Preparation of chain-bead-shaped conductive nickel powder particles:
[0031] Nickel sulfate was dissolved evenly in water, and then the temperature was raised to 70-75°C. Under stirring, oxalic acid precipitant with a molar amount of nickel ions twice and multi-walled carbon nanotube nucleating agent (with a diameter of about 20 nm and a length of about 10 μm) with a mass of 0.72% nickel ions were added to react the product. After filtration, the precipitate was washed with deionized water, dried under vacuum at 120°C, and then thermally decomposed under vacuum at 500-550°C for 3 hours to obtain chain-bead-shaped conductive nickel powder particles.
[0032] The average particle size D of the obtained chain-bead nickel powder conductive particles 50 It is 12.5μm, D 90 Its thickness is 28.7 μm; its apparent density is 0.6 g / cm³. 3 .
[0033] (2) Preparation of conductive sheet:
[0034] 1) Chain-bead-shaped conductive nickel powder particles and epoxy resin matrix were uniformly mixed under vacuum, with a weight percentage of 70:30, to obtain a conductive adhesive. The thickness of the obtained conductive adhesive after being heated and pressed with the substrate at 150℃, 2MPa, and 30min was compared with the thickness of the conductive layer before heating and pressing, showing a ratio of 60:100.
[0035] 2) Apply a pressure of less than 2 MPa and a temperature of less than 150°C to the conductive adhesive obtained in step 1) and attach it to the reinforcing steel sheet to form a steel sheet with a conductive film layer of 36 μm thickness. Then, attach an insulating protective film layer on the conductive film layer to obtain a conductive sheet.
[0036] Example 2
[0037] A conductive sheet according to this embodiment is prepared by the following method:
[0038] (1) Preparation of chain-bead-shaped conductive nickel powder particles:
[0039] Nickel sulfate was dissolved evenly in water, and then the temperature was raised to 70-75°C. Under stirring, ammonium oxalate precipitant with a molar amount of nickel ions twice and multi-walled carbon nanotube nucleating agent (with a diameter of about 40 nm and a length of about 10 μm) with a mass of 0.50% nickel ions were added to react the product. After filtration, the precipitate was washed with deionized water, dried under vacuum at 120°C, and then thermally decomposed under vacuum at 450-500°C for 3 hours to obtain chain-bead-shaped conductive nickel powder particles.
[0040] The average particle size D of the obtained chain-bead nickel powder conductive particles 50 It is 17.3 μm, D 90 Its thickness is 42.6 μm; its apparent density is 0.5 g / cm³.3 .
[0041] (2) Preparation of conductive sheet:
[0042] 1) Chain-bead-shaped conductive nickel powder particles and epoxy resin matrix were uniformly mixed under vacuum, with a weight percentage of 75:25, to obtain a conductive adhesive. The thickness of the obtained conductive adhesive after being heated and pressed with the substrate at 150℃, 2MPa, and 30min was compared with the thickness of the conductive layer before heating and pressing, showing a ratio of 50:100.
[0043] 2) Apply a pressure of less than 2 MPa and a temperature of less than 150°C to the conductive adhesive obtained in step 1) and attach it to the reinforcing steel sheet to form a steel sheet with a conductive film layer of 30 μm thickness. Then, attach an insulating protective film layer on the conductive film layer to obtain a conductive sheet.
[0044] Example 3
[0045] A conductive sheet according to this embodiment is prepared by the following method:
[0046] (1) Preparation of chain-bead-shaped conductive nickel powder particles:
[0047] Nickel sulfate was dissolved evenly in water, and then the temperature was raised to 70-75°C. Under stirring, ammonium oxalate precipitant with a molar amount of nickel ions twice and multi-walled carbon nanotube nucleating agent (with a diameter of about 10 nm and a length of about 5 μm) with a mass of 1.05% nickel ions were added to react the product. After filtration, the precipitate was washed with deionized water, dried under vacuum at 120°C, and then thermally decomposed under vacuum at 550-600°C for 3 hours to obtain chain-bead-shaped conductive nickel powder particles.
[0048] The average particle size D of the obtained chain-bead nickel powder conductive particles 50 It is 8.8μm, D 90 Its thickness is 21.6 μm; its apparent density is 0.4 g / cm³. 3 .
[0049] (2) Preparation of conductive sheet:
[0050] 1) Chain-bead-shaped conductive nickel powder particles and epoxy resin matrix were uniformly mixed under vacuum, with a weight percentage of 80:20, to obtain a conductive adhesive. The thickness of the conductive adhesive after being heated and pressed with the substrate at 150℃, 2MPa, and 30min was measured to be 65:100 compared to the thickness of the conductive layer before heating and pressing.
[0051] 2) Apply a pressure of less than 2 MPa and a temperature of less than 150°C to the conductive adhesive obtained in step 1) and attach it to the reinforcing steel sheet to form a steel sheet with a conductive film layer of 38 μm thickness. Then, attach an insulating protective film layer on the conductive film layer to obtain a conductive sheet.
[0052] Comparative Example 1
[0053] Compared with Example 1, the conductive sheet in this comparative example was prepared by using ordinary spherical nickel powder conductive particles instead of chain-bead nickel powder conductive particles.
[0054] The average particle size D of the spherical nickel powder conductive particles 50 It is 12.2 μm, D 90 Its thickness is 18.0 μm; its apparent density is 4.8 g / cm³. 3 .
[0055] The thickness of the conductive adhesive obtained from the test after being heated and pressed with the substrate at 150℃, 2MPa and 30min was 92:100 compared with the thickness of the conductive layer before heating and pressing.
[0056] Comparative Example 2
[0057] Compared with Example 1, this comparative example does not involve the addition of multi-walled carbon nanotube nucleating agents in the preparation of nickel powder conductive particles. The specific preparation steps are as follows:
[0058] (1) Preparation of conductive nickel powder particles:
[0059] Nickel sulfate was dissolved evenly in water, and then the temperature was raised to 70-75°C. Under stirring, oxalic acid precipitant with a molar amount of nickel ions was added to react. After filtration, the precipitate was washed with deionized water, dried under vacuum at 120°C, and then thermally decomposed under vacuum at 500-550°C for 3 hours to obtain conductive nickel powder particles.
[0060] The obtained nickel powder conductive particles are amorphous, with an average particle size D. 50 It is 10.4 μm, D 90 Its thickness is 27.7 μm; its apparent density is 3.5 g / cm³. 3 .
[0061] (2) The preparation of the conductive sheet is the same as in Example 1.
[0062] The thickness of the conductive adhesive obtained from the test after being heated and pressed with the substrate at 150℃, 2MPa and 30min was 81:100 compared with the thickness of the conductive layer before heating and pressing.
[0063] Comparative Example 3
[0064] Compared with Example 1, this comparative example does not use multi-walled carbon nanotube nucleating agents in the preparation of nickel powder conductive particles. Instead, multi-walled carbon nanotubes are added during the preparation of the conductive sheet. The specific preparation steps are as follows:
[0065] (1) The preparation of nickel powder conductive particles is the same as that of comparative example 2.
[0066] (2) Preparation of conductive sheet:
[0067] 1) The nickel powder conductive particles obtained in step (1) were mixed uniformly with multi-walled carbon nanotubes (approximately 20 nm in diameter and 10 μm in length) containing 0.72% nickel ions by mass and an epoxy resin matrix under vacuum kneading. The weight percentage of nickel powder conductive particles to epoxy resin matrix was 70:30, resulting in a conductive adhesive. The thickness of the conductive adhesive after being heated and pressed with the substrate at 150°C, 2 MPa, and 30 min was measured to be 82:100 compared to the thickness of the conductive layer before heating and pressing.
[0068] 2) Apply a pressure of less than 2 MPa and a temperature of less than 150°C to the conductive adhesive obtained in step 1) and attach it to the reinforcing steel sheet to form a steel sheet with a conductive film layer of 36 μm thickness. Then, attach an insulating protective film layer on the conductive film layer to obtain a conductive sheet.
[0069] Comparative Example 4
[0070] Compared with Example 1, this comparative example uses dendritic conductive microparticles with a silver coating formed on the surface of copper core, as described in CN 103597551 A, instead of chain-bead nickel powder conductive particles. The rest are the same.
[0071] The average particle size D of the dendritic conductive microparticles in the silver-coated copper core 90 The average particle size is 25 μm, and the average particle size D is... 50 The thickness is 13 μm; the apparent density is 0.7 g / cm³. 3 .
[0072] The thickness of the conductive adhesive obtained from the test after being heated and pressed with the substrate at 150℃, 2MPa and 30min was 60:100 compared with the thickness of the conductive layer before heating and pressing.
[0073] The conductive sheets obtained in the above embodiments and comparative examples were subjected to initial resistivity measurement and conductivity stability test (resistivity was measured after repeated bending at 90° 100 times). The test results are shown in Table 1 below.
[0074] Table 1
[0075] Example 1 <![CDATA[1.85×10 -3 ]]> <![CDATA[2.71×10 -3 ]]> Example 2 <![CDATA[1.76×10 -3 ]]> <![CDATA[2.66×10 -3 ]]> Example 3 <![CDATA[1.59×10 -3 ]]> <![CDATA[2.47×10 -3 ]]> Comparative Example 1 <![CDATA[5.36×10 -1 ]]> <![CDATA[14.28×10 -1 ]]> Comparative Example 2 <![CDATA[5.48×10 -3 ]]> <![CDATA[8.52×10 -3 ]]> Comparative Example 3 <![CDATA[5.02×10 -3 ]]> <![CDATA[7.61×10 -3 ]]> Comparative Example 4 <![CDATA[1.75×10 -3 ]]> <![CDATA[2.54×10 -3 ]]>
[0076] As shown in Table 1, the conductive sheet of this invention uses specific chain-bead-shaped nickel powder conductive particles, which exhibit better conductivity and conductivity stability compared to ordinary spherical nickel powder conductive particles and amorphous nickel powder conductive particles. It also possesses conductivity and conductivity stability consistent with imported high-performance silver-coated copper-core dendritic conductive microparticles, demonstrating promising market prospects. Furthermore, the comparison between Comparative Examples 2 and 3 and Example 1 shows that adding multi-walled carbon nanotubes as a nucleating agent during the preparation of the nickel powder conductive particles significantly affects the morphology of the particles and reduces their apparent density, significantly reducing the ratio of the thickness of the conductive adhesive after heat pressing to its thickness before heat pressing, and achieving better conductivity and conductivity stability. However, the improvement in performance from adding multi-walled carbon nanotubes during the preparation of the conductive sheet is limited, indicating that the performance improvement mainly lies in the composite process and synergistic effect of the nickel powder conductive particles and multi-walled carbon nanotubes.
[0077] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within the protection scope of the present invention.
Claims
1. A conductive sheet, characterized in that, It includes a conductive film layer, wherein the conductive film layer comprises a resin matrix and chain-bead-shaped nickel powder conductive particles distributed in the resin matrix; The thickness of the conductive film and the particle size of the chain-bead nickel powder conductive particles satisfy the following conditions (I) and (II): (I) The thickness of the conductive layer after being heated and pressed with the substrate at 150℃, 2MPa and 30min is 25~70:100 compared with the thickness of the conductive layer before heating and pressing. (II) The average particle size D of the chain-bead nickel powder conductive particles 50 The thickness is less than 0.5 times that of the conductive film layer; The average particle size D of the chain-bead-shaped nickel powder conductive particles 50 The particle size is 3~50μm; and the weight percentage of the chain-bead-shaped nickel powder conductive particles in the conductive film layer is 50%~90%. The chain-bead-shaped conductive nickel powder particles are prepared by the following method: Soluble nickel salts are added to water and dissolved evenly. Then the temperature is raised to 50-80℃, and oxalic acid or ammonium oxalate precipitant and carbon nanotube nucleating agent are added under stirring to react. The resulting precipitate is washed and dried, and then thermally decomposed under vacuum or protective atmosphere at 300-600℃ to obtain chain-bead-shaped conductive nickel powder particles. The carbon nanotube nucleating agent uses multi-walled carbon nanotubes with a diameter of 10-100 nm and an aspect ratio of 100-2000. The apparent density of the chain-like nickel powder conductive particles is 0.3~1.2 g / cm³. 3 .
2. The conductive sheet according to claim 1, characterized in that, The soluble nickel salt is at least one of nickel chloride, nickel sulfate, and nickel nitrate.
3. A conductive sheet according to claim 1, characterized in that, The average particle size D of the chain-bead-shaped nickel powder conductive particles 90 The average particle size D 50 1.5 to 5 times that.
4. A conductive sheet according to claim 1, characterized in that, The resin matrix is a thermosetting phenolic resin, epoxy resin, urethane resin, melamine resin, alkyd resin, or polyimide resin.
5. A conductive sheet according to claim 1, characterized in that, One side of the conductive film layer is covered with an insulating protective film layer, and the other side is attached with a reinforcing steel sheet.
6. A method for preparing a conductive sheet according to any one of claims 1 to 5, characterized in that, The preparation steps include the following: (1) The chain-bead-shaped nickel powder conductive particles and the resin matrix are mixed evenly under vacuum to obtain a conductive adhesive; (2) Apply a pressure of less than 2MPa and a temperature of less than 150°C to the conductive adhesive obtained in step (1) and attach it to the reinforcing steel sheet to form a steel sheet with a conductive film layer. Then, attach an insulating protective film layer to the conductive film layer to obtain a conductive sheet.