A prepreg and preparation method thereof and copper clad laminate

Abstract

The present invention discloses a prepreg and a preparation method thereof and a copper clad laminate. The preparation method of the prepreg comprises: placing a PTFE demulsified blank in a molding device for extrusion to obtain a plurality of PTFE sheets, wherein the molding device comprises a pressing plate and a pressing groove, and a slit is provided on the side wall of the pressing groove; stacking the plurality of PTFE sheets in the molding device for extrusion to obtain a plurality of PTFE sheets after secondary extrusion; repeating the above-mentioned extrusion steps of the sheets, cyclically extruding the PTFE sheets to obtain a PTFE prepreg blank; drying the PTFE prepreg blank to obtain a prepreg. The present invention obtains a prepreg with good dimensional stability and uniform and stable dielectric properties by adopting a molding device with a simple structure, which is beneficial to subsequent processing and product stability; this device utilizes the material properties of PTFE after fiberization, and adopts a cyclic extrusion process route to obtain a self-supporting PTFE prepreg with high mechanical strength.

Description

Technical Field

[0001] The invention relates to the technical field of prepreg preparation, and in particular to a prepreg, a preparation method thereof and a copper clad laminate. Background Art

[0002] At present, the common semi-cured sheet resin composition matrix includes epoxy resin, hydrocarbon resin, PPO, PTFE, etc. Among them, PTFE has the best performance in all aspects. It is a new type of thermoplastic organic material that can achieve high-frequency and high-speed transmission. PTFE has excellent chemical inertness, extremely strong high and low temperature resistance, aging resistance, insulation, flame retardancy and excellent dielectric properties. Most of the existing PTFE semi-cured sheets are prepared by a gluing device in which glass fiber cloth is impregnated with PTFE emulsion. The dielectric properties of the copper clad laminate prepared by this gluing device are unevenly distributed, which affects the high-frequency application scenarios at the back end.

[0003] Currently, most PTFE prepregs that do not contain glass fiber cloth are obtained by plunger extrusion, calendaring or molding. For PTFE materials, their mechanical properties cannot be guaranteed.

[0004] Therefore, the existing preparation method of prepreg needs to be improved and developed. Summary of the invention

[0005] In view of the above-mentioned deficiencies in the prior art, the object of the present invention is to provide a prepreg and a preparation method thereof and a copper clad laminate, aiming to solve the problems of uneven internal filler distribution, unstable mechanical properties and uneven dielectric properties of the prepreg prepared by the existing prepreg preparation method.

[0006] A method for preparing a prepreg, comprising the following steps:

[0007] S10, placing the PTFE demulsified embryo material in a molding device for extrusion to obtain a plurality of PTFE flakes;

[0008] S20, stacking the plurality of PTFE sheets and extruding them in the molding device to obtain a plurality of secondary extruded PTFE sheets;

[0009] S30, repeating step S20 several times, cyclically extruding the PTFE sheet material to obtain a PTFE prepreg blank;

[0010] S40, drying the PTFE prepreg blank to obtain a prepreg.

[0011] Optionally, in the method for preparing the prepreg, the molding device comprises: a pressing groove and a pressing plate adapted to the pressing groove; the pressing groove comprises a square groove body and slits at the same height opened on the side walls of the square groove body.

[0012] Optionally, in the method for preparing the semi-cured sheet, the square trough body comprises: a bottom plate, four columns and four side plates; the four columns are fixed on the bottom plate, each side plate is fixed between two adjacent columns, and the four side plates and the bottom plate form a square trough body with one end open; a slit is opened in the middle of each side plate, and the four slits are the same in size and shape.

[0013] Optionally, in the method for preparing the prepreg, the width of the slit is 5-10 mm; and the pillars located at the slit are triangular pillars.

[0014] Optionally, in the method for preparing the prepreg, the extrusion pressure in step S10 is 0.5-1 MPa; and the extrusion pressure in step S20 is 1-2 MPa.

[0015] Optionally, in the method for preparing the prepreg, each time the extrusion is repeated in step S30, the extrusion pressure is increased successively, and the pressure increment range is 1-5 MPa.

[0016] Optionally, in the method for preparing the prepreg, the step S10 specifically comprises:

[0017] The PTFE demulsified blank is placed in a pressing tank, and the pressing plate is heated at a temperature of 30-50° C.;

[0018] The PTFE demulsified blank is pressed downward by the pressing plate, and part of the PTFE demulsified blank is squeezed out from the slit to obtain a plurality of PTFE flakes.

[0019] Optionally, in the method for preparing the prepreg, the baking temperature is two-stage baking, the first stage is 60-80°C, and the second stage is 250-330°C.

[0020] A prepreg, wherein the prepreg is prepared by the above-mentioned preparation method.

[0021] A copper clad laminate, comprising the prepreg described above.

[0022] Beneficial effects: Compared with the prior art, the method for preparing a semi-cured sheet provided by the present invention utilizes the material properties of PTFE after fiberization and adopts a cyclic extrusion process route to obtain a self-supporting, high mechanical strength and stable PTFE semi-cured sheet. The semi-cured sheet does not contain glass fiber cloth, and the dielectric properties are uniform and stable. The method is simple and easy to operate. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 Schematic diagram of the structure of the PTFE prepreg molding device;

[0024] Figure 2 It is a schematic diagram of the structure of the slit-pressed groove column in the slit-pressed groove;

[0025] Figure 3 is a schematic cross-sectional view of a slit groove;

[0026] Figure 4 Schematic diagram of the process for manufacturing PTFE prepreg. DETAILED DESCRIPTION

[0027] The present invention provides a prepreg and a preparation method thereof and a copper clad laminate. To make the purpose, technical solution and effect of the present invention clearer and more specific, the present invention is further described in detail below. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0028] A method for preparing a prepreg, the method comprising the following steps:

[0029] S10, placing the demulsified PTFE blank in a molding device for extrusion to obtain a plurality of PTFE flakes.

[0030] Specifically, the PTFE refers to polytetrafluoroethylene (PTFE), and the demulsification is also called demulsification, which means that the emulsion is completely destroyed and becomes two immiscible phases. Figure 1 As shown, the molding device includes two parts, namely, a pressing plate 10 and a pressing groove 20. The pressing plate 10 includes: a body 11, a pressure part 12 fixed in the middle of the body 11 for contacting an external pressure device, and the body 11 is square in shape, and its size is adapted to the size of the pressing groove 20. The pressing groove 20 includes: a square groove body 21 and slits 22 opened at the same height on the side wall of the square groove body 21. The number of the slits 22 can be one, two, three or four. When the PTFE demulsified embryo material is extruded, part of the PTFE demulsified embryo material is extruded from the slits 22 to form PTFE sheets. It is easy to understand that when the number of the slits 22 is two, two PTFE sheets can be obtained by one extrusion. When the number of slits is one, one PTFE sheet can be obtained by one extrusion, so multiple extrusions can be used to obtain the corresponding number of sheets, such as four sheets obtained by extruding four times.

[0031] In this embodiment, the square trough body 21 includes: a bottom plate 23, four columns 24 and four side plates 25; the four columns 24 are fixed on the bottom plate 23, and each side plate 25 is fixed between two adjacent columns 24, and the four side plates 25 and the bottom plate 23 constitute a square trough body with one end open; a slit 22 is provided in the middle of each side plate 25. It is easy to understand that the pressing groove 20 can be regarded as a square column with one end open and a hollow center. A slit is provided at the same height on the four side walls of the square column. By setting four slits at the same height and with the same size and shape, four PTFE sheets of the same specification can be obtained at one time when extrusion is performed.

[0032] In this embodiment, by using a square pressing plate adapted to the square pressing groove, the pressure on the PTFE demulsified blank in the pressing groove during extrusion can be uniform in all directions, so that the obtained PTFE flakes are also uniform.

[0033] In this embodiment, combined with Figure 2 and Figure 3 The shape of the column is a triangular column in the middle (slit) of the two end cylinders, that is, the surface of the column at the slit is a plane. By setting the column at the slit as a triangular column, it is easier to extrude the PTFE demulsified blank from the slit into PTFE flakes.

[0034] For example, the length and width of the pressing plate are 200×200 mm, the width of the slit 22 is 5-10 mm, the depth of the pressing groove is 300 mm, and the distance between the lower edge of the slit and the bottom plate is 100 mm. The pressure during extrusion is 0.5-1 MPa.

[0035] After step S10, step S20 is included, wherein the plurality of PTFE sheets are stacked and extruded in the molding device to obtain a plurality of secondary extruded PTFE sheets.

[0036] Specifically, combined Figure 4 , stacking the PTFE sheets obtained in step S10 into the pressing groove, and performing secondary extrusion through the pressing plate to obtain the secondary extruded PTFE sheets. The strength of the obtained sheets is enhanced by performing secondary extrusion on the PTFE sheets. The extrusion pressure can be 1-2MPa.

[0037] After step S20, step S30 is included, in which step S20 is repeated several times to cyclically extrude the PTFE sheet material to obtain a PTFE prepreg sheet blank.

[0038] Specifically, the PTFE sheet obtained through secondary extrusion in step S20 is stacked in a pressure groove, and is extruded again, and the obtained PTFE sheet is stacked in a pressure groove and extruded, and the cycle is repeated for many times, such as 3-6 cycles. By adopting the mode of cyclic extrusion, the PTFE demulsification embryo material is fibrotic to form a self-supporting structure, and the obtained PTFE sheet has a stronger mechanical structure. Wherein, in the process of cyclic extrusion, the pressure of each cycle is increased successively, and the pressure increment is 1-5MPa.

[0039] For example, the previous extrusion pressure is 1MPa, the extrusion pressure in the second cycle is 2MPa, the extrusion pressure in the third cycle is 3MPa, and the extrusion pressure in the fourth cycle is 4MPa. It should be noted that the increments of the pressure increase in sequence may be the same or different, such as the previous extrusion pressure is 1MPa, the extrusion pressure in the second cycle is 2MPa, the extrusion pressure in the third cycle is 4MPa, the extrusion pressure in the fourth cycle is 5MPa, the extrusion pressure in the fifth cycle is 7MPa, and the extrusion pressure in the sixth cycle is 8MPa.

[0040] In this embodiment, by sequentially increasing the extrusion pressure during the cycle, the PTFE fiberization distribution is made more uniform, the dielectric properties are more stable, and the mechanical strength is higher. At the same time, since the size and shape of the slits on the molding device used are the same, a sheet with good dimensional stability can be obtained, which means that a prepreg blank with good dimensional stability can be obtained.

[0041] After step S30, the method further includes step S40 of drying the PTFE prepreg blank to obtain a prepreg.

[0042] Specifically, after step S30 cyclic extrusion, from the several sheets at the beginning, finally become an integral body, namely first be squeezed into sheet stock (preliminary Fibration) by PTFE demulsification embryo material, then sheet stock is cyclically extruded, PTFE Fibrosis is made, owing to be formed an integral body by uniform sheet stock cyclic extrusion, the PTFE prepreg obtained is also uniform.It is conducive to the stability of subsequent processing and product.And owing to be self-supporting, more stable than the PTFE prepreg dielectric property containing glass fiber cloth obtained by gluing device, PTFE is more evenly distributed.

[0043] In this embodiment, the PTFE semi-cured sheet blank is dried by placing it in an oven and baking it in two temperature stages. The first stage baking temperature can be 60-80°C, the baking time is 1-2 hours, and the second stage baking temperature is 250-330°C, the baking time is 1-2 hours.

[0044] In an implementation of this embodiment, step S10 specifically includes:

[0045] S100, placing the PTFE demulsified blank in a pressing tank, and heating the pressing plate at a heating temperature of 30-50° C.;

[0046] S200, pressing the pressing plate downward to press the PTFE demulsified blank, so that part of the PTFE demulsified blank is squeezed out from the slit to obtain a plurality of PTFE flakes.

[0047] Specifically, the pressing plate can be heated by electric heating or steam heating, such as setting a heating element on the upper heating plate, turning on the power to generate heat, or directly contacting the upper surface of the pressing plate with hot steam. By heating the pressing plate and controlling the heating temperature at 30-50°C, it can prevent the PTFE demulsified blank from adhering to the pressing plate during extrusion, and can also make it easier to extrude the PTFE demulsified blank to form a PTFE sheet, and give the sheet a certain strength. It should be noted that the temperature of the pressing plate can be controlled at 30-50°C during the cyclic extrusion process.

[0048] Based on the same inventive concept, the present invention also provides a prepreg, which is prepared by the above preparation method.

[0049] Exemplarily, a certain amount of PTFE demulsified blank is placed in a pressing groove, wherein the depth of the pressing groove is 300 mm, the length and width of the pressing plate are 200×200 mm, and the width of the slit on the side wall of the pressing groove is 5 mm. Then, the surface of the pressing plate is heated at a temperature of 30° C. The PTFE demulsified blank is pressed downward by the pressing plate, and the PTFE demulsified blank is squeezed out from the slit under the action of pressure to form a sheet. The extrusion pressure is 1 MPa, and the length of the sheet is 200 mm. Four sheets of sheet are stacked and put back into the pressing groove, and the stacked PTFE sheet is squeezed downward by the pressing plate. The pressure at this time is 2MPa, to obtain a secondary extruded PTFE sheet with a length of 200mm, then stack the four sheets and put them back into the pressing groove, and then use a pressing plate to press the stacked PTFE sheet downward, at this time the pressure is 3MPa, to obtain a third extruded PTFE sheet; the extrusion cycle is repeated 5 times, and the pressure increment during each cycle is 1MPa to obtain a PTFE semi-cured sheet blank, and the PTFE semi-cured sheet blank is put into an oven for baking, the first stage oven temperature is 65°C, and the baking is performed for 1 hour, and the second stage oven temperature is 270°C, and the baking is performed for 1 hour to obtain a PTFE semi-cured sheet.

[0050] Based on the same inventive concept, the present invention also provides a copper clad laminate, wherein the prepreg in the copper clad laminate is the PTFE prepreg described above. Because the PTFE prepreg does not contain glass fiber cloth, its performance is more stable, thereby making the electrical performance of the copper clad laminate more stable.

[0051] In summary, the present invention provides a prepreg and a preparation method thereof and a copper clad laminate, wherein the preparation method of the prepreg comprises: placing a PTFE demulsified blank in a molding device for extrusion to obtain a plurality of PTFE sheets, wherein the molding device comprises a pressing plate and a pressing groove, and a slit is provided on the side wall of the pressing groove; stacking the plurality of PTFE sheets in the molding device for extrusion to obtain a plurality of secondary extruded PTFE sheets; repeating the above-mentioned sheet extrusion step, cyclically extruding the PTFE sheets, to obtain a PTFE prepreg blank; and drying the PTFE prepreg blank to obtain a prepreg.

[0052] The present invention adopts a simple-structured molding device to obtain a prepreg with good dimensional stability and uniform and stable dielectric properties, which is beneficial to subsequent processing and product stability; this device utilizes the material properties of PTFE after fiberization and adopts a cyclic extrusion process route to obtain a self-supporting PTFE prepreg with high mechanical strength. Compared with the device of the traditional gluing process, this device method obtains a PTFE prepreg without glass fiber cloth, and the performance is more uniform and stable.

[0053] It should be understood that the application of the present invention is not limited to the above examples. For ordinary technicians in this field, improvements or changes can be made based on the above description. All these improvements and changes should fall within the scope of protection of the claims attached to the present invention.

Claims

1. A method for preparing a prepreg, characterized in that: The steps include: S10, placing the PTFE demulsified embryo material in a molding device for extrusion to obtain a plurality of PTFE flakes; S20, stacking the plurality of PTFE sheets and extruding them in the molding device to obtain a plurality of secondary extruded PTFE sheets; S30, repeating step S20 several times, cyclically extruding the PTFE sheet material to obtain a PTFE prepreg blank; S40, drying the PTFE prepreg blank to obtain a prepreg; The forming device comprises: a pressing groove and a pressing plate adapted to the pressing groove; the pressing groove comprises: a square groove body and a slit at the same height on the side wall of the square groove body; The square trough body comprises: a bottom plate, four columns and four side plates; the four columns are fixed on the bottom plate, each side plate is fixed between two adjacent columns, and the four side plates and the bottom plate form a square trough body with one end open; a slit is opened in the middle of each side plate, and the four slits are the same in size and shape.

2. The method for preparing a prepreg according to claim 1, characterized in that: The width of the slit is 5-10 mm; the pillar located at the slit is a triangular pillar.

3. The method for preparing a prepreg according to claim 1, characterized in that: The extrusion pressure in step S10 is 0.5-1 MPa; the extrusion pressure in step S20 is 1-2 MPa.

4. The method for preparing a prepreg according to claim 1, characterized in that: Each time the extrusion is repeated in step S30, the extrusion pressure is increased successively, and the pressure increment range is 1-5 MPa.

5. The method for preparing a prepreg according to claim 1, characterized in that: The step S10 specifically includes: The PTFE demulsified blank is placed in a pressing tank, and the pressing plate is heated at a temperature of 30-50° C.; The PTFE demulsified blank is pressed downward by the pressing plate, and part of the PTFE demulsified blank is squeezed out from the slit to obtain a plurality of PTFE flakes.

6. The method for preparing a prepreg according to claim 1, characterized in that: Step S40 is baked in two steps, the baking temperature is 60-80° C. in the first stage and 250-330° C. in the second stage.

7. A prepreg, characterized in that: The preparation method is described in any one of claims 1 to 6.

8. A copper clad laminate, characterized in that: The present invention comprises the prepreg as claimed in claim 7.

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