A printed circuit made by an additive method

Abstract

The utility model discloses a kind of printed circuits made of additive method, including substrate, patterned first adhesive layer and conductive powder circuit layer, first adhesive layer is attached to the top surface of substrate, conductive powder circuit layer is attached to the top surface of patterned first adhesive layer, the conductive powder includes metal conductive powder or non-metal conductive powder.The printed circuit made of additive method of the utility model has lower resistivity and cost.

Description

[Technical Field]

[0001] This utility model relates to printed circuits, and more particularly to a printed circuit manufactured by an additive manufacturing method. [Background Technology]

[0002] There are two main technical routes for manufacturing electronic circuits. The first is the traditional "subtractive method," which uses copper-clad laminates as a base and removes a large amount of copper through processes such as photolithography, development, and etching, leaving the desired circuit pattern. This method is mature, but it has inherent drawbacks such as a lengthy process, the generation of large amounts of chemical waste leading to environmental pollution, low raw material utilization (especially for the skin effect in high-frequency circuits, where a large amount of copper is wasted), and limited substrate selection.

[0003] The second method is the "additive manufacturing process," represented by screen-printed conductive pastes (such as conductive silver paste and carbon paste). This method can directly build circuits on various substrates, and the process is relatively short. However, its bottlenecks are also very prominent: 1) High cost: High-performance conductive pastes heavily rely on expensive silver powder; 2) Limited performance: After the paste cures, the conductive particles are three-dimensionally coated by an insulating resin binder, forming a point contact or surface contact conductive network. Its volume resistivity is much higher than that of pure metal, resulting in poor conductivity and large signal loss; 3) Poor solderability: The surface of the cured circuit is usually covered with a resin film, which hinders the wetting of standard solder, making soldering difficult. It requires the use of conductive adhesive or special low-temperature solder, which increases the complexity of the process and the risk of long-term reliability problems.

[0004] For example, US Patent No. US20100059260A1 discloses a composite metal thin film particle, a dispersion of the composite metal thin film particle, an ink for manufacturing a conductive substrate, a method for manufacturing a conductive substrate, and a conductive substrate, wherein the circuit formed by the method has metal particles in a conductive paste encapsulated in resin, and a sheet resistance > 50 mΩ / □.

[0005] Poor conductivity; after the circuit is cured, an insulating resin film remains on the surface, requiring laser cleaning or special solder, resulting in poor solderability and high cost. [Summary of the Invention]

[0006] The technical problem to be solved by this invention is to provide a printed circuit with low resistivity and low cost, which is manufactured by additive manufacturing.

[0007] To solve the above-mentioned technical problems, the present invention adopts a technical solution of an additive manufacturing method for a printed circuit, comprising a substrate, a patterned first adhesive layer, and a conductive powder circuit layer. The first adhesive layer is attached to the top surface of the substrate, and the conductive powder circuit layer is attached to the top surface of the patterned first adhesive layer. The conductive powder includes metallic conductive powder or non-metallic conductive powder.

[0008] The printed circuit described above includes a conductive plating layer, which is plated on the top surface of the conductive powder circuit layer.

[0009] The printed circuit described above uses a glass fiber reinforced epoxy resin composite substrate as its substrate and a hot melt adhesive layer as its first adhesive layer. The conductive powder circuit layer is a sprayed conductive powder layer with an average particle size of 0.1μm-2μm, and the conductive powder portion of the sprayed conductive powder layer is embedded in the first adhesive layer. The metal plating layer is a chemically plated copper layer with a thickness of 0.1μm-3μm.

[0010] The printed circuit described above is an RFID tag circuit, the substrate is a flexible substrate, and the conductive powder is aluminum powder, copper powder, graphite powder, or silver powder.

[0011] The printed circuit described above uses a paper substrate as its substrate, and the silver powder has an average particle size of 0.1μm-2μm.

[0012] The printed circuit described above includes a patterned second adhesive layer, the top surface of the substrate is curved, and the patterned second adhesive layer is attached to the top surface of the conductive powder circuit layer.

[0013] In the printed circuit described above, the substrate is a ceramic body, and the average particle size of the conductive powder is 0.1μm-2μm.

[0014] The printed circuit described above uses a printed circuit board as its substrate, which has circuitry already formed. The circuitry of the printed circuit board includes metal pads that are difficult to solder. The patterned first adhesive layer includes a conductive adhesive layer corresponding to the metal pads, and the conductive adhesive layer is on the top surface of the metal pads. The metal powder circuit layer includes a metal powder layer that is easy to solder.

[0015] The printed circuit described above includes a chemical tin plating layer, and the easily solderable metal powder layer is a copper powder layer, with the chemical tin plating layer adhering to the top surface of the copper powder layer.

[0016] The additive manufacturing method of this invention produces printed circuits with lower resistivity and lower cost. [Image Description]

[0017] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments.

[0018] Figure 1 This is a schematic diagram of step 2 of the additive manufacturing process of printed circuit in Embodiment 1 of this utility model.

[0019] Figure 2 This is a schematic diagram of step 4 of the additive manufacturing process of printed circuit in Embodiment 1 of this utility model.

[0020] Figure 3This is a schematic diagram of the printed circuit product structure of Embodiment 1 of this utility model.

[0021] Figure 4 Yes, yes Figure 3 A magnified view of part I in the middle section.

[0022] Figure 5 This is a schematic diagram of step 1 of the additive manufacturing process of printed circuit in Embodiment 2 of this utility model.

[0023] Figure 6 This is a schematic diagram of step 2 of the additive manufacturing process of printed circuit in embodiment 2 of this utility model.

[0024] Figure 7 This is a schematic diagram of the printed circuit product structure of Embodiment 2 of this utility model.

[0025] Figure 8 yes Figure 7 A magnified view of part II in the middle section.

[0026] Figure 9 This is a schematic diagram of step 1 of the additive manufacturing process of printed circuit in embodiment 3 of this utility model.

[0027] Figure 10 This is a schematic diagram of step 2 of the additive manufacturing process of printed circuit in embodiment 3 of this utility model.

[0028] Figure 11 This is a schematic diagram of step 3 of the additive manufacturing process of printed circuit in embodiment 3 of this utility model.

[0029] Figure 12 This is a schematic diagram of step 4 of the additive manufacturing process of printed circuit in embodiment 3 of this utility model.

[0030] Figure 13 This is a schematic diagram of the printed circuit product structure of Embodiment 3 of this utility model.

[0031] Figure 14 yes Figure 13 A magnified view of part III in the middle section.

[0032] Figure 15 This is a schematic diagram of step 1 of the additive manufacturing process of printed circuit in embodiment 4 of this utility model.

[0033] Figure 16 This is a schematic diagram of step 2 of the additive manufacturing process for printed circuits in Embodiment 4 of this utility model.

[0034] Figure 17 This is a schematic diagram of step 3 of the additive manufacturing of printed circuit in embodiment 4 of this utility model.

[0035] Figure 18 This is a schematic diagram of the printed circuit product structure of Embodiment 4 of this utility model.

[0036] Figure 19 yes Figure 18 A magnified view of part IV in the middle section. [Detailed Implementation]

[0037] I. Example 1 of the additive manufacturing of printed circuits according to this utility model: Fabrication of solderable circuits on an FR-4 substrate using a direct method, such as... Figures 1 to 4 As shown, it includes the following steps:

[0038] 1) Substrate treatment: Select 1.6mm thick FR-4 epoxy resin board 1 as the insulating substrate and clean its surface with alcohol.

[0039] 2) Preparation of the patterned adhesive layer: Epoxy hot melt adhesive 2 is screen-printed using a 200-mesh screen to form a circuit pattern 2 with a line width of 0.2mm. Pre-bake at 85℃ for 3 minutes to maintain adhesion. Figure 1 As shown.

[0040] 3) Selective adhesion of metal powder: Spherical copper powder with an average particle size of 0.1-1μm (purity >99.9%) is sprayed using a fluidized bed, and excess powder is removed by vibration.

[0041] 4) Mechanical densification: In the semi-cured state of the adhesive, the copper powder layer 3 is rolled with a hot roller (pressure 0.8MPa, temperature 90℃), such as... Figure 2 As shown.

[0042] 5) Curing and Chemical Deposition: Hot-press curing at 150℃ for 10 minutes → Immersion in chemical copper deposition solution (CuSO4 20g / L, EDTA 35g / L, formaldehyde 10mL / L, 50℃) for 15 minutes, depositing a 0.5μm copper layer. 4. The structure of the printed circuit product is as follows: Figure 3 and Figure 4 As shown.

[0043] Technical effects of Embodiment 1 of this utility model:

[0044] 1) Sheet resistance ≤ 12 mΩ / □ (compared to undensified sample > 50 mΩ / □);

[0045] 2) The pad area can be directly reflow soldered with SnAgCu solder paste (peak temperature 245℃).

[0046] II. Example 2 of the additive manufacturing of printed circuits of this utility model: Fabrication of RFID tag circuits on a paper substrate using the release film transfer method, as shown below. Figures 5 to 8 As shown, it includes the following steps:

[0047] 1) Temporary carrier treatment: Silkscreen epoxy layer 2 (antenna pattern) onto 100μm PET release film 7, bake at 60℃ until semi-cured, as shown. Figure 5 As shown.

[0048] 2) Adhesive Layer Transfer: The release film is bonded to the surface of a 100g / m² paper substrate 1, and rolled (pressure 0.3MPa) to transfer the semi-cured adhesive layer 2 to the paper substrate 1, as shown below. Figure 6 As shown.

[0049] 3) Metal Powder Adhesion and Curing: After spraying silver powder with an average particle size of 0.5μm, it is heated and cured at 150℃ for 20 minutes to form the silver powder circuit layer 3 of the flexible antenna. The structure of the RFID tag circuit product is as follows: Figure 7 and Figure 8 As shown.

[0050] (The silver powder in this embodiment can be replaced with aluminum powder, copper powder, or graphite powder)

[0051] Technical effects of Embodiment 2 of this utility model:

[0052] 1) This embodiment omits the chemical plating step, resulting in very low cost for the RFID tag circuit.

[0053] 2) The Alien Higgs-4 chip can be bonded via ACF hot-press bonding, and the tag reading distance reaches 3.5m.

[0054] III. Example 3 of the additive manufacturing of printed circuits of this utility model: An antenna is fabricated on curved ceramic using a water-soluble film transfer method, such as... Figures 9 to 14 As shown, it includes the following steps:

[0055] 1) Patterning of the water-soluble film: Epoxy adhesive (spiral antenna pattern) is screen-printed onto a 100μm PVA water-soluble film 11 to form a patterned epoxy adhesive layer 2. Epoxy adhesive layer 2 is allowed to stand at room temperature for 30 minutes until semi-cured. Figure 9 As shown.

[0056] 2) Silver powder adhesion and curing: A silver powder layer 3 with an average particle size of 0.5μm is electrostatically sprayed. Epoxy adhesive layer 2 is cured for 10 minutes at 80℃. The silver powder layer 3 forms the primary circuit, such as... Figure 10 As shown.

[0057] 3) Print epoxy hot melt adhesive on the surface of the primary circuit to form epoxy hot melt adhesive layer 4, such as... Figure 11 As shown.

[0058] 4) Primary Circuit Transfer: The PVA water-soluble film 11 with epoxy hot melt adhesive layer 4 and silver powder layer 3 is bonded to the curved surface (radius of curvature R = 8 mm) of the zirconia ceramic 1. A soft scraper is used to smooth the surface, ensuring conformal contact. Figure 12 As shown.

[0059] 5) Dissolution of the water-soluble film: Immerse the zirconia ceramic 1 with the PVA water-soluble film 11 in 40℃ warm water for 5 minutes to dissolve the PVA water-soluble film, and then dry it with hot air at 60℃. The structure of the antenna product on the curved ceramic is as follows. Figure 13 and Figure 14 As shown.

[0060] Technical effects of Embodiment 3 of this utility model:

[0061] 1) The gap between curved surfaces is <10μm (detected by laser profilometer).

[0062] 2) Antenna resonant frequency deviation < 0.1MHz (design value 13.56MHz)

[0063] IV. Example 4 of the additive manufacturing of printed circuits of this utility model involves a solderability enhancement treatment for aluminum substrate pads, such as... Figures 15 to 19 As shown, it includes the following steps:

[0064] 1) Substrate preparation: An aluminum-based printed circuit board with pre-patterned circuitry is selected. The aluminum-based printed circuit board includes a 1.0mm thick FR-4 substrate 10. The aluminum-based circuit layer 11 on the substrate 10 has two pads 12, each measuring 1mm × 1mm. Figure 15 As shown.

[0065] 2) Local processing: Silver conductive adhesive is printed on the pad area using a precision screen (300 mesh) to form a silver conductive adhesive layer with a thickness of 10±2μm and a silver content of 80wt%. Figure 16 As shown.

[0066] 3) Densification of metal powder: Spread 0.3μm spherical copper powder, then hot press (0.5MPa, 120℃, 30s) to embed the copper powder into the adhesive layer, forming a copper powder layer 5. Figure 17 As shown.

[0067] 4) Chemical deposition: Immersion in tin-plating solution (SnSO4 15g / L, thiourea 80g / L, pH=1.5, 30℃) for 120 seconds to form a tin layer 1-2μm thick. Figure 18 and Figure 19 As shown.

[0068] Technical effects of Embodiment 4 of this utility model:

[0069] 1) The wetted area of ​​the solder pads is increased to >95% (original aluminum solder pads <60%).

[0070] 2) Welding tensile strength can reach 8.2N (J-STD-002 standard).

[0071] The substrate of Embodiment 4 of this utility model is an etched aluminum-based printed circuit board. By applying a composite process of conductive adhesive, metal powder and chemical deposition, the industry problem of poor solderability of aluminum / nickel pads is specifically solved.

[0072] Although the conductive powder in the above embodiments of this utility model is described using metal powder as an example, when welding performance is not a concern, non-metallic conductive powder can be used instead of metal powder as the conductive powder in this utility model. For example, graphite powder or graphene powder can be used as the conductive powder to construct the conductive circuit of this utility model, achieving most of the technical effects of the above embodiments of this utility model. The printed circuits fabricated by the additive manufacturing method in the above embodiments of this utility model have the following beneficial effects:

[0073] 1) High-precision circuit molding is achieved on diverse substrates such as paper, curved ceramics, and flexible polymers through temporary carrier transfer method (water-soluble film / PET release film).

[0074] 2) The circuit formed by using exposed metal powder + chemical deposition technology has low resistivity and low sheet resistance; the surface is not covered with resin and is compatible with standard SnAgCu solder paste.

[0075] 3) For aluminum / nickel substrate pads, a local enhancement process of conductive adhesive + dense copper powder + chemical tin plating is used to increase the solder pull force of aluminum / nickel substrate pads by 135%.

[0076] 4) Compared with circuits formed by ink printing, the amount of metal used can be reduced by 60%, and inexpensive copper powder can be used instead of silver powder, resulting in a significant reduction in total cost.

Claims

1. A printed circuit fabricated by an additive manufacturing method, comprising a substrate, characterized in that, It includes a patterned first adhesive layer and a conductive powder circuit layer. The first adhesive layer is attached to the top surface of the substrate, and the conductive powder circuit layer is attached to the top surface of the patterned first adhesive layer. The conductive powder includes metallic conductive powder or non-metallic conductive powder.

2. The printed circuit according to claim 1, characterized in that, It includes a metal plating layer, which is plated on the top surface of the conductive powder circuit layer.

3. The printed circuit according to claim 2, characterized in that, The substrate is a glass fiber reinforced epoxy resin matrix composite substrate, the first adhesive layer is a hot melt adhesive layer; the conductive powder circuit layer is a sprayed conductive powder layer with an average particle size of 0.1μm-2μm, and the conductive powder portion of the sprayed conductive powder layer is embedded in the first adhesive layer; the metal plating layer is a chemically plated copper layer with a thickness of 0.1μm-3μm.

4. The printed circuit according to claim 1, characterized in that, The printed circuit is an RFID tag circuit, the substrate is a flexible substrate, and the conductive powder is aluminum powder, copper powder, silver powder, or graphite powder.

5. The printed circuit according to claim 4, characterized in that, The substrate is a paper substrate, and the average particle size of the conductive powder is 0.1μm-2μm.

6. The printed circuit according to claim 1, characterized in that, It includes a patterned second adhesive layer, the top surface of the substrate is curved, and the patterned second adhesive layer is attached to the top surface of the conductive powder circuit layer.

7. The printed circuit according to claim 6, characterized in that, The substrate is a ceramic body, and the conductive powder has an average particle size of 0.1μm-2μm.

8. The printed circuit according to claim 1, characterized in that, The substrate is a printed circuit board with pre-formed circuitry, the circuitry of which includes metal pads that are difficult to solder; the patterned first adhesive layer includes a conductive adhesive layer corresponding to the metal pads, the conductive adhesive layer being on the top surface of the metal pads; the metal powder circuit layer includes a metal powder layer that is easy to solder.

9. The printed circuit according to claim 8, characterized in that, It includes a chemically plated tin layer, and the easily solderable metal powder layer is a copper powder layer, with the chemically plated tin layer adhering to the top surface of the copper powder layer.

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