Liquid crystal polymer composite material as well as preparation method and application thereof

Abstract

The invention relates to a liquid crystal polymer composite material as well as a preparation method and application thereof. The liquid crystal polymer composite material comprises the following components: liquid crystal polymer resin, calcium carbonate and glass fibers. According to the liquid crystal polymer composite material, on the basis of considering the binding force of the plating layer, the problems that the glass fiber punctures the plating layer and the plating layer foams at a high temperature are effectively avoided.

Description

Technical Field

[0001] This invention relates to the field of engineering plastics technology, and more specifically, to a liquid crystal polymer composite material, its preparation method, and its application. Background Technology

[0002] Liquid crystal polymers (LCPs) are widely used in electronic connectors due to their excellent flowability, dimensional stability, and flame-retardant properties. To further improve their mechanical properties and expand their application range, glass fibers are often added to LCPs to obtain composite LCP materials.

[0003] In some special applications, components need to have high conductivity, but the product structure is very precise and cannot be directly processed with metal. Therefore, LCP material is chosen to injection mold such electronic components. To achieve high conductivity, one technical route is to develop conductive LCP material specifications by adding conductive fillers, but its conductivity still cannot reach the effect of metal. Another technical route is to plate a metal layer on the surface of LCP material parts to obtain high conductivity.

[0004] The process of plating a metal layer on the surface of LCP material parts mainly includes chemical surface roughening, undercoating, and metal plating. Chemical surface roughening uses acid to etch the surface of the part, thus obtaining a rough surface; the undercoating mainly involves electroless nickel plating and / or copper plating; and the metal plating layer is usually an electroplated metal layer such as copper, gold, silver, or tin. Currently, problems with metal plating on LCP material parts include glass fiber punctures in the plating, blistering of the plating after high temperatures, and insufficient adhesion of the plating.

[0005] Regarding the issue of glass fiber piercing the coating, after chemical roughening, the surface of LCP material parts becomes rough, exposing the glass fibers in the material. If a large number of piercings occur on the surface coating of the parts after electroplating, it will seriously affect the conductivity of the parts.

[0006] Regarding the issue of blistering in the plating layer after high temperature, the parts after electroplating metal need to be assembled with metal terminals and soldered to the motherboard through high-temperature reflow soldering. When blistering occurs in the plating layer after high temperature, it will lead to problems such as missing solder or poor soldering in the product.

[0007] Insufficient adhesion of the coating can affect the reliability of LCP material components as electronic products.

[0008] Existing technologies have conducted some research on the coating adhesion of LCP materials, such as the Chinese patent entitled "Liquid Crystal Polymer Material for Environmentally Friendly Electroplating and its Preparation Method". However, there is still a lack of technical means to solve the problems of glass fiber puncturing the coating and coating blistering after high temperature in LCP material parts.

[0009] Therefore, developing new technologies to solve the problems of glass fiber puncturing the coating, coating blistering after high temperature, and insufficient coating adhesion when plating metal layers on the surface of LCP material parts is of great significance. Summary of the Invention

[0010] The primary objective of this invention is to overcome the problems of glass fiber puncturing the coating, coating blistering after high temperature, and insufficient coating adhesion in the current technology when plating metal layers on the surface of LCP material parts, and to provide a liquid crystal polymer composite material.

[0011] A further object of the present invention is to provide a method for preparing the above-mentioned liquid crystal polymer composite material.

[0012] A further object of the present invention is to provide the application of the above-mentioned liquid crystal polymer composite material in the preparation of electronic connectors.

[0013] The above-mentioned objective of the present invention is achieved through the following technical solution:

[0014] A liquid crystal polymer composite material comprises the following components in parts by weight:

[0015] 99-101 parts of liquid crystal polymer resin,

[0016] 2-10 parts calcium carbonate

[0017] 15-100 parts glass fiber

[0018] The calcium carbonate has a particle size D50 of 3.2–8 μm;

[0019] In the liquid crystal polymer composite material, the mass of glass fibers with a retention length of 40-400 μm accounts for ≥80% of the total mass of glass fibers, the mass of glass fibers with a retention length of <40 μm accounts for <10% of the total mass of glass fibers, and the mass of glass fibers with a retention length of >400 μm accounts for <10% of the total mass of glass fibers.

[0020] In this invention, liquid crystal polymer resin is used as the main resin, accounting for at least 40% of the mass of the liquid crystal polymer composite material. The amount of calcium carbonate added can be 2 parts, 3 parts, 4 parts, 5 parts, 6 parts, 7 parts, 8 parts, 9 parts, or 10 parts; the amount of glass fiber added can be 15 parts, 20 parts, 25 parts, 30 parts, 35 parts, 40 parts, 45 parts, 50 parts, 55 parts, 60 parts, 65 parts, 70 parts, 75 parts, 80 parts, 85 parts, 90 parts, 95 parts, or 100 parts.

[0021] Studies have found that liquid crystal polymer composite parts coated with metal exhibit blistering at high temperatures. This is because the micropores formed after the surface roughening of the parts are uneven, resulting in residual gas in the base metal layer and the roughened plastic surface. The gas expands at high temperatures.

[0022] The inventors of this invention have discovered that by controlling the proportion of glass fibers with smaller retention lengths (retention length < 40 μm) and larger retention lengths (retention length > 400 μm) in the total mass of the liquid crystal polymer composite material, the surface roughness uniformity of the composite material after roughening treatment can be improved. This improved roughness uniformity enhances the adhesion of the coating to the part and ensures the uniformity of micropores on the surface. At high temperatures, it prevents the formation of large bubbles due to gas expansion in some larger micropores, reducing the risk of blistering at high temperatures. Simultaneously, it avoids excessive exposure of long-retention glass fibers on the surface, reducing the risk of glass fibers puncturing the coating. If the proportion of glass fibers with smaller retention lengths (retention length < 40 μm) is too high, the surface roughness uniformity of the liquid crystal polymer composite material after roughening treatment will be poor, leading to poor coating adhesion. Furthermore, the uneven distribution of micropores easily results in the formation of large bubbles, increasing the risk of blistering. Conversely, if the proportion of glass fibers with larger retention lengths (retention length > 400 μm) is too high, the risk of glass fibers puncturing the coating increases. The amount of glass fiber relative to liquid crystal polymer resin also affects the coating adhesion, the risk of blistering at high temperatures, and the risk of glass fiber puncturing the coating. Therefore, it is necessary to control the amount of glass fiber relative to liquid crystal polymer resin.

[0023] However, simply adjusting the mass ratio and amount of glass fiber with smaller retention lengths (retention length < 40 μm) and larger retention lengths (retention length > 400 μm) in the liquid crystal polymer composite material is insufficient to achieve a satisfactory level of coating adhesion and reduce the risk of blistering at high temperatures. The inventors of this invention further discovered that adding a certain amount of calcium carbonate within a specific particle size range can effectively prevent blistering at high temperatures while maintaining good coating adhesion in the resulting liquid crystal polymer composite material. The reason for this may be that controlling the amount and particle size of calcium carbonate allows for more uniform dispersion on the surface of the part, and the micropores formed under acid corrosion treatment (chemical surface roughening uses acid to corrode the part surface) are more uniform and finer, thereby further improving the surface roughness uniformity of the part, thus enhancing the coating adhesion and reducing the risk of blistering at high temperatures.

[0024] In other words, the liquid crystal polymer composite material of the present invention effectively avoids the problems of glass fiber puncturing the coating and blistering of the coating at high temperatures, while taking into account the coating adhesion.

[0025] Liquid crystal polymer resins commonly used in this field can be used in this invention. For example, liquid crystal polymer resins polymerized from aromatic hydroxycarboxylic acids and aromatic dicarboxylic acids with one or more compounds selected from aromatic diols, aromatic hydroxyamines, or aromatic diamines; or liquid crystal polymer resins polymerized from different aromatic hydroxycarboxylic acids; or liquid crystal polymer resins polymerized from aromatic dicarboxylic acids with at least one compound selected from aromatic diols, aromatic hydroxyamines, or aromatic diamines; or liquid crystal polymer resins polymerized from polyesters such as polyethylene terephthalate with aromatic hydroxycarboxylic acids.

[0026] Optionally, the melting point of the liquid crystal polymer resin is ≥300℃, preferably 340~380℃. The melting point (Tm) of the liquid crystal polymer resin can be measured by differential scanning calorimetry.

[0027] Optionally, the melt viscosity of the liquid crystal polymer resin is 5–35 Pa·s; the melt viscosity can be measured according to ISO 11443-2021 at Tm+15℃ and 1000 s. -1 The temperature was measured under the specified conditions; Tm is the melting point of the liquid crystal polymer resin.

[0028] Preferably, the calcium carbonate has a particle size D50 of 3.5–8 μm, more preferably 4.5–6 μm. Specifically, it can be 4 μm, 5 μm, 6 μm, 7 μm, or 8 μm.

[0029] In this invention, the particle size D50 of calcium carbonate can be measured by a particle size analyzer.

[0030] Optionally, the average cross-sectional diameter of the glass fiber is 5–12 μm.

[0031] In this invention, the average cross-sectional diameter of the glass fiber can be measured by scanning electron microscopy (SEM).

[0032] Preferably, the mass percentage of glass fiber in the liquid crystal polymer composite material is 12-50%.

[0033] More preferably, the glass fiber content in the liquid crystal polymer composite material is 31%–50% by mass. Within this range, the risk of blistering of the liquid crystal polymer composite material coating at high temperatures is lower.

[0034] More preferably, the glass fiber mass percentage in the liquid crystal polymer composite material is 12% to 32%. Within this range, the risk of the glass fiber puncturing the coating is lower.

[0035] Preferably, the liquid crystal polymer composite material further includes 0.1 to 3 parts of other additives.

[0036] Optionally, the other additives are at least one of antioxidants or lubricants.

[0037] Optionally, the antioxidant is selected from at least one of amine antioxidants, phenolic antioxidants, or sulfur antioxidants.

[0038] Optionally, the lubricant is selected from at least one of linear low-density polyethylene (LLDPE), silicone oil, fluoropolymers, metal stearate, metal montanic acid, alkyl stearate, montanic ester wax, or polyethylene wax.

[0039] The preparation method of the above-mentioned liquid crystal polymer composite material is characterized by comprising the following steps: mixing the components other than glass fiber to obtain a mixture; adding the mixture from the main feed port of the extruder, adding the glass fiber from the side feed port of the extruder, melting and extruding, and granulating to obtain the liquid crystal polymer composite material.

[0040] The application of the above-mentioned liquid crystal polymer composite material in the preparation of electronic connectors is also within the scope of protection of this invention.

[0041] The electronic connector is a connector with a surface electroplated metal layer.

[0042] A liquid crystal polymer composite material part includes a resin material and a metal layer plated on the surface of the resin material, wherein the resin material is the aforementioned liquid crystal polymer composite material.

[0043] Compared with the prior art, the beneficial effects of the present invention are:

[0044] The liquid crystal polymer composite material of the present invention effectively avoids the problems of glass fiber puncturing the coating and blistering of the coating at high temperatures, while taking into account the coating adhesion. Detailed Implementation

[0045] To more clearly and completely describe the technical solution of the present invention, the present invention will be further described in detail below through specific embodiments. It should be understood that the specific embodiments described herein are only for explaining the present invention and are not intended to limit the present invention. Various changes can be made within the scope of the claims of the present invention.

[0046] The reagents used in the various embodiments and comparative examples of this invention are described below:

[0047] Liquid crystal polymer resin 1# (LCP1#): Zhuhai Wantong Special Engineering Plastics, Vicryst R800, liquid crystal polymer resin with melting point Tm of 350℃±10℃;

[0048] Liquid crystal polymer resin 2# (LCP2#): Zhuhai Wantong Special Engineering Plastics, Vicryst R8200, liquid crystal polymer resin with melting point Tm of 370℃±10℃;

[0049] Calcium carbonate A: Purchased from Mouheng Materials Technology, model VGEM-8, particle size D50 is 2.8μm;

[0050] Calcium carbonate B: Purchased from Mouheng Materials Technology, model VGEM-12, particle size D50 is 3.5μm;

[0051] Calcium carbonate C: Purchased from Mouheng Materials Technology, model VGEM-20, particle size D50 is 5μm;

[0052] Calcium carbonate D: Purchased from Mouheng Materials Technology, model VGEM-30, particle size D50 is 8μm;

[0053] Calcium carbonate E: purchased from Mouheng Materials Technology, model VGEM-45, particle size D50 is 11μm;

[0054] Glass fiber A: Purchased from Owens Corning, model 923, with an average cross-sectional diameter of 10 μm and an initial average length of 3 mm;

[0055] Glass fiber B: purchased from Owens Corning, model FT771, with an average cross-sectional diameter of 6μm and an initial average length of 3mm;

[0056] Other additives #1: Lubricant, linear low-density polyethylene, commercially available.

[0057] Unless otherwise specified, all components (e.g., other additives 1#) used in the parallel examples and comparative examples are the same commercially available products.

[0058] The liquid crystal polymer composite materials provided in the embodiments and comparative examples of the present invention were subjected to performance testing according to the following test methods:

[0059] (1) The characterization method of the retention length and distribution of glass fibers is as follows: Take the liquid crystal polymer composite materials of each example and comparative example, and obtain the ash content of the liquid crystal polymer composite materials according to ISO 3451-1:2008; place the ash in 100 mL of 95% industrial alcohol and disperse it with an ultrasonic machine for 2 min, then use a pipette to take 2 mL from the bottom and place it on a clean glass slide, take a picture with an optical microscope at 500x magnification, measure the retention length of 1000 glass fibers, count the distribution of the retention length of glass fibers and calculate the weight ratio of different lengths.

[0060] (2) Bubbling Risk Test of Electroplated Layer: Using a twin-screw extruder, liquid crystal polymer composite material was used to mold 100 square plates (64mm*64mm*1mm) using a single-screw injection molding machine. The plates were then electroplated using a mature electroplating process. The 100 plates were placed in a 260℃ constant temperature oven and baked for 30 minutes. The percentage of plates with bubbling was then counted. Bubbling Risk Assessment Criteria: Grade A: Bubbling ratio ≤10%, fully meeting product usage requirements; Grade B: Bubbling ratio 10%-20%, basically meeting product usage requirements; Grade C: Bubbling ratio 20%-50%, only partially meeting product usage requirements; Grade D: Bubbling ratio ≥50%, completely failing to meet product usage requirements.

[0061] (3) Risk test of glass fiber puncture electroplating layer: Five 64mm*64mm*1mm square plates were molded from liquid crystal polymer composite material obtained by twin-screw extruder using a single-screw injection molding machine. The plates were then electroplated using a mature electroplating process. The number of punctures on the front and back of the five plates was counted. Risk assessment standard for glass fiber puncture coating layer: Level I: Number of puncture points ≤ 20, fully meets product usage requirements; Level II: Number of puncture points ≤ 50, basically meets product usage requirements; Level III: Number of puncture points ≤ 100, only meets some product usage requirements; Level IV: Number of puncture points ≥ 100, completely fails to meet product usage requirements.

[0062] (4) Cross-cut test: Referring to ISO2409-2013, use a cross-cut cutter to make 100 (10×10) 1mm×1mm small grids on the surface of a 250×250mm electroplated sample. Each grid line should penetrate to the bottom layer of the liquid crystal polymer composite material sample. Clean the test area with a brush. Firmly adhere the test grids with 3M No. 600 adhesive tape and rub the tape vigorously with an eraser to increase the contact area and force between the tape and the test area. Hold one end of the tape and quickly tear it off vertically (90°). Perform the same test twice at the same location. The evaluation level is as follows:

[0063] Table 1

[0064]

[0065] The liquid crystal polymer composite materials of the embodiments and comparative examples of the present invention were prepared by the following preparation method:

[0066] Weigh each component according to the formula; mix all components except glass fiber to obtain a mixture; then feed the mixture into the twin-screw extruder through the main feed port; feed the glass fiber into the twin-screw extruder through different side feed ports at T... m The liquid crystal polymer composite material is obtained by melting, extruding, and granulating at +10℃.

[0067] In this invention, the retained length and distribution of glass fibers in the liquid crystal polymer composite material are related to the initial average length of the glass fibers, the fiber insertion position (side feed port position), the screw speed of the twin-screw extruder, and the screw's length-to-diameter ratio. Methods known in the art for controlling the retained length and distribution of glass fibers (such as controlling the initial average length of the glass fibers, changing the fiber insertion position, controlling the screw speed of the twin-screw extruder, or controlling the screw's length-to-diameter ratio) can all be applied to this invention. In this invention, the screw speed and length-to-diameter ratio of the twin-screw extruder are kept constant, while the initial average length or insertion position of the glass fibers is changed to alter the retained length and distribution of the glass fibers. Specifically, the twin-screw extruder of the present invention has four side feed ports, with the first, second, third, and fourth side feed ports located sequentially away from the motor end and close to the extruder outlet. Since the glass fiber breaks and shortens in length when sheared by the screw in the extruder, glass fibers with different retention lengths and different retention length distributions can be obtained by adding them from the side feed ports at different positions. If the glass fiber is added from the side feed port close to the motor end (e.g., the first side feed port), the glass fiber is sheared for a longer time in the extruder, resulting in a shorter retention length. If the glass fiber is added from the side feed port away from the motor end (e.g., the fourth side feed port), the glass fiber is sheared for a shorter time in the extruder, resulting in a longer retention length. In the examples 1-7, 9-14 and comparative examples 3-8, the glass fibers were added from the second side feed port of the twin-screw extruder; in the example 8, the glass fiber was added from the third side feed port of the twin-screw extruder; in the comparative example 1, the glass fiber was added from the first side feed port of the twin-screw extruder; and in the comparative example 2, the glass fiber was added from the fourth side feed port of the twin-screw extruder.

[0068] Examples 1-13

[0069] Examples 1-13 provide a series of liquid crystal polymer composite materials, the formulations of which are shown in Table 2.

[0070] Table 2. Formulations (parts by weight) for Examples 1-13

[0071]

[0072]

[0073] Comparative Examples 1-8

[0074] Comparative Examples 1-8 provide a series of liquid crystal polymer composite materials, the formulations of which are shown in Table 3.

[0075] Table 3 shows the formulations (parts by weight) for Comparative Examples 1–8.

[0076]

[0077] The properties of the liquid crystal polymer composite materials of each embodiment and comparative example were determined according to the test methods mentioned above, and the test results are shown in Table 4.

[0078] Table 4. Performance test results of liquid crystal polymer composite materials in each embodiment and comparative example.

[0079]

[0080]

[0081] As can be seen from Table 4:

[0082] The liquid crystal polymer composite materials in Examples 1-13 all had a cross-cut adhesion test rating of 0 or 1, a blistering risk rating of A or B, and a glass fiber puncture risk rating of I or II. This indicates that the liquid crystal polymer composite material of the present invention effectively avoids the problems of glass fiber puncture and blistering of the coating at high temperatures while taking into account the coating adhesion.

[0083] In Comparative Example 1, the percentage of glass fibers with a length <40 micrometers was too high, resulting in poor coating adhesion and a high risk of blistering at high temperatures in the resulting liquid crystal polymer composite material. In Comparative Example 2, the percentage of glass fibers with a length >400 micrometers was too high, leading to a high risk of fiber punctures in the coating. In Comparative Example 3, the D50 of the added calcium carbonate was too low, resulting in poor coating adhesion and a high risk of blistering at high temperatures in the resulting liquid crystal polymer composite material. In Comparative Example 4, the D50 of the added calcium carbonate was too high, resulting in poor coating adhesion and a high risk of blistering at high temperatures in the resulting liquid crystal polymer composite material. In Comparative Examples 5 (no calcium carbonate added) and 6 (too much calcium carbonate added), both resulted in poor coating adhesion and a high risk of blistering at high temperatures in the resulting liquid crystal polymer composite material. In Comparative Example 7, the amount of added glass fibers was too low, resulting in a high risk of blistering at high temperatures in the coating of the resulting liquid crystal polymer composite material. The amount of glass fiber added in Comparative Example 8 was too high, resulting in a higher risk of the glass fiber puncturing the coating in the liquid crystal polymer composite material.

[0084] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the implementation of the present invention. Those skilled in the art can make other variations or modifications based on the above description. It is neither necessary nor possible to exhaustively describe all embodiments here. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the claims of the present invention.

Claims

1. A liquid crystal polymer composite material, characterized in that, The components include the following parts by weight: 99-101 parts of liquid crystal polymer resin, 2-10 parts calcium carbonate 15-100 parts glass fiber The calcium carbonate has a particle size D50 of 3.2–8 μm; In the liquid crystal polymer composite material, glass fibers with a retention length of 40-400 μm account for ≥80% of the total mass of glass fibers, glass fibers with a retention length <40 μm account for <10% of the total mass of glass fibers, and glass fibers with a retention length >400 μm account for <10% of the total mass of glass fibers.

2. The liquid crystal polymer composite material according to claim 1, characterized in that, The melting point of the liquid crystal polymer resin is ≥300℃.

3. The liquid crystal polymer composite material according to claim 1, characterized in that, The calcium carbonate has a particle size D50 of 4.5–6 μm.

4. The liquid crystal polymer composite material according to claim 1, characterized in that, The average diameter of the cross-section of the glass fiber is 5–12 μm.

5. The liquid crystal polymer composite material according to claim 1, characterized in that, The glass fiber content in the liquid crystal polymer composite material is 12% to 50% by mass.

6. The liquid crystal polymer composite material according to claim 1, characterized in that, The liquid crystal polymer composite material also includes 0.1 to 3 parts of other additives.

7. The liquid crystal polymer composite material according to claim 6, characterized in that, The other additives are at least one of antioxidants or lubricants.

8. A method for preparing the liquid crystal polymer composite material according to any one of claims 1 to 7, characterized in that, The process includes the following steps: mixing the components other than glass fiber to obtain a mixture; adding the mixture from the main feed port of the extruder and adding the glass fiber from the side feed port of the extruder, melting and extruding, and granulating to obtain the liquid crystal polymer composite material.

9. The use of the liquid crystal polymer composite material according to any one of claims 1 to 7 in the preparation of electronic connectors.

10. A liquid crystal polymer composite material part, characterized in that, It includes a resin material and a metal layer plated on the surface of the resin material, wherein the resin material is any one of the liquid crystal polymer composite materials according to claims 1 to 7.

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