Polytetrafluoroethylene-based laser direct structuring material as well as preparation method and application thereof

Abstract

The invention discloses a polytetrafluoroethylene-based laser direct structuring material as well as a preparation method and application thereof. The laser direct structuring material comprises the following components in percentage by weight: 50-85% of polytetrafluoroethylene; 1-15% of a laser direct structuring additive; 1 to 10% of fluorine-containing polyimide micro powder; 1-10% of a mesoporous material; and 10-30% of an inorganic filler. The laser direct structuring material obtained by the invention shows excellent plating property, dielectric property and plating layer bonding strength.

Description

Technical Field

[0001] The present invention belongs to the field of functional polymer materials, and particularly relates to a polytetrafluoroethylene-based laser direct forming material, a preparation method thereof, and an application thereof. Background Art

[0002] LDS, namely laser direct structuring, the principle of which is to endow ordinary plastic components / circuit boards with functions such as electrical interconnection, support for components, support and protection of plastic casings, and functions such as shielding and antennas generated by the combination of mechanical entities and conductive patterns, and is applicable to the production of local fine circuits.

[0003] LDS can largely avoid the environmental pollution and water consumption of traditional plastic electroplating processes, simplify the production process, and through the flexible combination of the flexibility and precision of lasers with the plasticity and functionality of engineering plastics, provide a flexible and variable design space and can achieve rapid 3D forming, while having a high processing resolution.

[0004] For the specific application of LDS engineering plastics, the laser activation ability of the plastic substrate and the adhesion between the coating and the substrate after electroless plating are two key factors.

[0005] The difficulty in preparing polytetrafluoroethylene-based laser direct forming materials lies in that: due to the special structural characteristics of polytetrafluoroethylene itself, insufficient metal particles are released after laser irradiation during the laser engraving process; in the subsequent electroless plating process, it will directly lead to incomplete formation of the electroless plating layer and ineffective surface metallization. In our invention patent CN111497097B, for this technical problem, an innovative solution of adding a charring promoter with a specific molecular structure is adopted, which retains the excellent performance of low dielectric loss of PTFE materials while achieving surface direct metallization.

[0006] The applicant further conducted in-depth research on the coating adhesion strength and dielectric properties of this material and found that there is still room for further improvement in these two properties. Excellent coating adhesion strength and dielectric properties can provide a greater design space and freedom for antenna design under the requirements of high-frequency and high-speed related applications. Summary of the Invention

[0007] The purpose of the present invention is to provide a polytetrafluoroethylene-based laser direct forming material with excellent plating performance, dielectric properties, and coating adhesion strength. Specifically, through the design and regulation of the aggregate structure of the PTFE composite material system and the laser direct forming process, a high-density, high-precision, and three-dimensional fine circuit design is realized on the surface of PTFE, with a strong bond between the coating and the substrate, and the PTFE material maintains excellent dielectric properties.

[0008] The present invention also provides an article made of the laser direct forming material described above.

[0009] Specifically, the technical solution adopted by the present invention to solve its technical problems is as follows:

[0010] A laser direct forming additive, a fluorinated polyimide fine powder, a mesoporous material, and an inorganic filler are added to PTFE powder in a certain proportion. After mixing the components evenly, they are pressed into a shape and then sintered and plasticized to form a shape.

[0011] As an embodiment, the percentage of raw materials includes:

[0012]

[0013] Preferably, the weight percentage of the fluorinated polyimide is 3-8%.

[0014] Preferably, the weight percentage of the mesoporous material is 1-6%.

[0015] As a further preference, the percentage of its raw materials includes:

[0016]

[0017] As a further more preference, the weight percentage of polytetrafluoroethylene is 55-80%; further, preferably 55-70%.

[0018] As a further more preference, the weight percentage of the laser direct forming additive is 5-12%; further, preferably 8-12%.

[0019] As a further more preference, the weight percentage of the mesoporous material is 3-6%; more specifically, preferably 3-5%.

[0020] As a further more preference, the weight percentage of the fluorinated polyimide is 4-8%; more specifically, preferably 4-6%.

[0021] As an embodiment, the laser direct forming additive includes a metal oxide, a filler coated with a metal oxide, a copper salt, a metal oxide spinel, an organometallic complex, or a combination thereof. For example, the metal oxide may be one or a mixture of at least two of zinc oxide, copper oxide, cobalt oxide, magnesium oxide, tin oxide, titanium oxide, iron oxide, aluminum oxide, nickel oxide, manganese oxide, chromium oxide. As a further preference, the laser activation substance is copper oxide, a copper salt, or a mixture thereof. More specifically, the laser direct forming additive is selected from one or more of tungsten-containing copper salts and copper chromium oxides.

[0022] As an embodiment, the fluorinated polyimide micropowder is synthesized by condensation polymerization of an aromatic dianhydride, an aromatic diamine and a capping agent, which is the same as the synthesis method of traditional polyimide, except that a fluorine-containing group is introduced into the main chain structure of the polyimide; for example, a fluorine-containing group can be introduced into the aromatic diamine, such as one or more trifluoromethyl groups. Common aromatic dianhydrides include: 3,3',4,4'-biphenyltetracarboxylic dianhydride, 3,3',4,4'-diphenylethertetracarboxylic dianhydride, 3,3',4,4'-benzophenonetetracarboxylic dianhydride, 4,4'-(hexafluoroisopropylidene)bisophthalic dianhydride, etc.; common aromatic diamines include: 1,4-bis(4'-amino-2'-trifluoromethylphenoxy)benzene, 4,4'-bis(4-amino-2-trifluoromethylphenoxy)biphenyl, 4,4'-bis(3-amino-5-trifluoromethylphenoxy)biphenyl, 3,4'-diaminodiphenyl ether, 4,4'-diaminodiphenyl ether, p-phenylenediamine, 1,3-bis(4-aminophenoxy)benzene, m-phenylenediamine, etc.

[0023] As an embodiment, the average particle size of the silicon-based mesoporous material is 50 - 1000 nm, and the pore size is 2 - 30 nm. As a further preference, the silicon-based mesoporous material is mesoporous molecular sieve and mesoporous silica.

[0024] As an embodiment, the inorganic filler comprises calcium carbonate, mica, talcum powder, montmorillonite, wollastonite, kaolin, barium sulfate, diatomite, titanium dioxide or any combination thereof.

[0025] In the present invention, the polytetrafluoroethylene-based laser direct forming material is made by the following steps:

[0026] (1) Mix polytetrafluoroethylene, laser direct forming additive, fluorinated polyimide micropowder, mesoporous material and inorganic filler evenly, and press and mold to obtain a blank;

[0027] (2) Sinter and plasticize the blank to obtain a polytetrafluoroethylene composite blank;

[0028] Optionally, enter step (3):

[0029] (3) The polytetrafluoroethylene composite blank can be machined through a series of mechanical processes to obtain a sample with a specific shape.

[0030] Optionally, enter step (4):

[0031] (4) Laser ablate the surface of the sample material through a laser activation process to form an etched area and activate the metal; then perform electroless plating, and respectively deposit copper, nickel and gold on the etched area, so as to form a product with a set conductive path on the surface.

[0032] Through the synergistic effect of fluorinated polyimide micropowder and mesoporous materials, the dielectric properties and coating adhesion strength of the material are further improved. The laser direct forming material obtained by this invention exhibits excellent plating performance, dielectric properties, and coating adhesion strength. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 It is a schematic structural diagram of a certain circuit element processed in Example 2 of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0034] The technical solutions of the present invention will be further described below in conjunction with specific embodiments. The following embodiments are intended to provide a complete disclosure and description to those of ordinary skill in the art on how to manufacture and evaluate the methods, devices, and systems disclosed and claimed herein. They are purely exemplary and are not intended to limit the present disclosure.

[0035] COMPARATIVE EXAMPLE

[0036] The total weight is 10 Kg. Polytetrafluoroethylene micropowder with a particle size of 120 microns (accounting for 65 wt% of the total material) is used, and 10 wt% of copper chromite oxide, 5 wt% of polyimide, and 20 wt% of calcium carbonate powder are added. After premixing the above raw materials evenly, they are kept under pressure for 5 minutes at a preforming pressure of 25 MPa. They are preheated at a heating rate of 120 °C / hour, sintered at 380 °C, and the holding time is 5 hours; then they are slowly cooled to 120 °C and annealed for 2 hours.

[0037] EXAMPLE 1

[0038] The total weight is 10 Kg. Polytetrafluoroethylene micropowder with a particle size of 120 microns (accounting for 65 wt% of the total material) is used, and 10 wt% of copper chromite oxide, 5 wt% of fluorinated polyimide micropowder (self-made, prepared by reacting 4,4'-bis(4-amino-2-trifluoromethylphenoxy)biphenyl and 3,3',4,4'-biphenyltetracarboxylic dianhydride), and 20 wt% of calcium carbonate powder are added. After premixing the above raw materials evenly, they are kept under pressure for 5 minutes at a preforming pressure of 25 MPa. They are preheated at a heating rate of 120 °C / hour, sintered at 380 °C, and the holding time is 5 hours; then they are slowly cooled to 120 °C and annealed for 2 hours.

[0039] EXAMPLE 2

[0040] The total weight is 10 Kg. Polytetrafluoroethylene fine powder with a particle size of 120 microns (accounting for 61 wt% of the total material) is used, 10 wt% of copper chromite oxide is added, 5 wt% of fluorinated polyimide fine powder (self-made, prepared by reacting 4,4'-bis(4-amino-2-trifluoromethylphenoxy)biphenyl and 3,3',4,4'-biphenyltetracarboxylic dianhydride), 4 wt% of silicon-based mesoporous molecular sieve (MCM-41), and 20 wt% of calcium carbonate powder. After premixing the above raw materials evenly, they are kept under pressure for 5 minutes at a preforming pressure of 25 MPa. They are preheated at a heating rate of 120 °C / hour, sintered at 380 °C, and the holding time is 5 hours; then slowly cooled to 120 °C and annealed for 2 hours.

[0041] Example 3

[0042] The total weight is 10 Kg. Polytetrafluoroethylene fine powder with a particle size of 120 microns (accounting for 63 wt% of the total material) is used, 12 wt% of copper tungsten oxide is added, 5 wt% of fluorinated polyimide fine powder (self-made, prepared by reacting 4,4'-bis(4-amino-2-trifluoromethylphenoxy)biphenyl and 3,3',4,4'-biphenyltetracarboxylic dianhydride), and 20 wt% of calcium carbonate powder. After premixing the above raw materials evenly, they are kept under pressure for 5 minutes at a preforming pressure of 25 MPa. They are preheated at a heating rate of 120 °C / hour, sintered at 380 °C, and the holding time is 5 hours; then slowly cooled to 120 °C and annealed for 2 hours.

[0043] Example 4

[0044] The total weight is 10 Kg. Polytetrafluoroethylene fine powder with a particle size of 120 microns (accounting for 59 wt% of the total material) is used, 12 wt% of copper tungsten oxide is added, 5 wt% of fluorinated polyimide fine powder (self-made, prepared by reacting 4,4'-bis(4-amino-2-trifluoromethylphenoxy)biphenyl and 3,3',4,4'-biphenyltetracarboxylic dianhydride), 4 wt% of silicon-based mesoporous molecular sieve (MCM-41), and 20 wt% of calcium carbonate powder. After premixing the above raw materials evenly, they are kept under pressure for 5 minutes at a preforming pressure of 25 MPa. They are preheated at a heating rate of 120 °C / hour, sintered at 380 °C, and the holding time is 5 hours; then slowly cooled to 120 °C and annealed for 2 hours.

[0045] The PTFE sheets made of the materials obtained from the comparative example and Examples 1 - 4 are processed to obtain a specific shape, and then laser ablation is performed on their surfaces to form an etching area and activate the metal; then electroless plating is carried out to form a conductive path in the etching area. Figure 1 It is a schematic structural diagram of a certain circuit element processed in Example 2 of the present invention.

[0046] The comparison of plating performance, dielectric properties, and coating adhesion of the comparative examples and Examples 1-4 is shown in Table 1. Regarding the plating performance, the test standard is ASTM B568. The plating index is calculated based on the coating thickness of the test sample and the coating thickness of the reference sample, and its data setting value is between 1 and 10, where 10 corresponds to the best plating performance. Generally, it is considered that this index should be greater than or equal to 9 to meet the practical requirements. The adhesion is tested by the cross-cut test method. The peeling of the coating on the cross-cut is inspected using a magnifying glass, and the coating adhesion grade of the product is determined by referring to the adhesion standard. Generally, 4B-5B is considered qualified. In addition, the dielectric properties (dielectric constant and dielectric loss) of the obtained samples are tested under the condition of a frequency of 10 GHz.

[0047] Table 1

[0048]

[0049] As can be seen from Table 1, compared with the comparative example, in Example 1, using fluorinated polyimide to replace conventional polyimide as the charring promoter can further reduce the dielectric constant and dielectric loss of the PTFE composite material system; in Example 2, with the introduction of mesoporous molecular sieve, the dielectric properties of the composite material sample are further improved, and the dielectric constant and dielectric loss can be controlled at a lower level. A similar trend can be further verified in Examples 3 and 4 when tungsten-containing copper salt is used as the laser direct structuring additive. At the same time, the results of Example 2 and Example 4 show that the addition of fluorinated polyimide and mesoporous molecular sieve can further improve the adhesion performance while obtaining better dielectric properties. The reason is that the introduction of fluorine-containing groups on the main chain structure of polyimide as the charring promoter in the system is beneficial to its compatibility with the PTFE substrate and is conducive to further reducing dielectric loss. The special structure of the mesoporous molecular sieve forms a certain anchoring effect, which helps the adhesion of the metal on the substrate surface and can significantly improve the bonding strength between the coating and the substrate.

Claims

1. A polytetrafluoroethylene-based laser direct structuring material, characterized in that: Mainly made of the following components in weight percentage:

2. The polytetrafluoroethylene-based laser direct structuring material according to claim 1, characterized in that: The laser direct structuring additive includes a metal oxide, a metal oxide coated filler, a copper salt, a metal oxide spinel, an organometallic complex, or a combination thereof.

3. The polytetrafluoroethylene-based laser direct structuring material according to claim 1, characterized in that: The mesoporous material is a silicon-based mesoporous material.

4. The polytetrafluoroethylene-based laser direct structuring material according to claim 1, characterized in that: The inorganic filler comprises calcium carbonate, mica, talc, montmorillonite, wollastonite, kaolin, barium sulfate, diatomaceous earth, titanium dioxide or any combination thereof.

5. The polytetrafluoroethylene-based laser direct structuring material according to claim 1, characterized in that: The mass ratio of the fluorinated polyimide powder to the mesoporous material is 1-1.5:

1.

6. The polytetrafluoroethylene-based laser direct structuring material according to claim 1, characterized in that: The weight percentage of the fluorine-containing polyimide powder is 3-8%; the weight percentage of the mesoporous material is 1-6%.

7. The polytetrafluoroethylene-based laser direct structuring material according to claim 1, characterized in that: The laser direct forming additive is one or more of tungsten-containing copper salts and copper-chromium oxides; the silicon-based mesoporous material is one or more of mesoporous molecular sieves and mesoporous silica.

8. The polytetrafluoroethylene-based laser direct structuring material according to any one of claims 1 to 7, characterized in that: Made by the following steps: (1) uniformly mixing polytetrafluoroethylene, laser direct forming additives, fluorinated polyimide powder, mesoporous material and inorganic filler, and pressing to obtain a preform; (2) Sintering and plasticizing the molded blank to obtain a polytetrafluoroethylene composite material blank.

9. A product with a conductive path on the surface, obtained by subjecting the polytetrafluoroethylene-based laser direct forming material according to any one of claims 1 to 7 to sample processing, laser processing and chemical plating.

10. A method for preparing a polytetrafluoroethylene-based laser direct structuring material or product according to any one of claims 1 to 9, characterized in that: The steps include: (1) uniformly mixing polytetrafluoroethylene, laser direct forming additives, fluorinated polyimide powder, mesoporous material and inorganic filler, and pressing to obtain a preform; (2) sintering and plasticizing the molded blank to obtain a polytetrafluoroethylene composite material blank; Optional step (3): (3) The PTFE composite material blank is subjected to corresponding mechanical processing to obtain a sample of a set shape; Optional step (4): (4) The surface of the sample material is lasered through a laser activation process to form an etched area and activate the metal; then chemical plating is performed to plate copper, nickel and gold on the etched area respectively, thereby forming a product with a conductive path on the surface.

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