LIQUID CRYSTAL POLYMER FILM, AND COMPOSITE FILM OF LIQUID CRYSTAL POLYMER AND POLYIMIDE AND MANUFACTURING METHOD THEREOF

Abstract

A liquid crystal polymer film, and a composite film of liquid crystal polymer and polyimide and a manufacturing method thereof are provided. The liquid crystal polymer film includes 63 wt % to 74 wt % of p-hydroxybenzoic acid, 21 wt % to 26 wt % of 6-hydroxy-2-naphthoic acid, and 5 wt % to 11 wt % of p-hydroxycinnamic acid. The composite film is manufactured by thermocompressing a single layer or multi layers of liquid crystal polymer film and polyimide film so that the composite film can have high flatness and the surface roughness Sa of the composite film is ranging from 0.1 m to 10 m. In the production process of the composite film, the composite film is rolled up and attached to a copper foil to form a high frequency substrate with good processability. After peeling the polyimide film, the liquid crystal polymer film can be thermocompressed to form a four-layered, six-layered, eight-layered or eight-layered high frequency substrate.

Claims

1. A liquid crystal polymer film, comprising: 63 wt % to 74 wt % of p-hydroxybenzoic acid; 21 wt % to 26 wt % of 6-hydroxy-2-naphthoic acid; and 5 wt % to 11 wt % of p-hydroxycinnamic acid.

2. The liquid crystal polymer film according to claim 1, wherein a surface roughness Sa of the liquid crystal polymer film is from 0.1 m to 10 m.

3. A composite film of liquid crystal polymer and polyimide, comprising: a liquid crystal polymer film containing 63 wt % to 74 wt % of p-hydroxybenzoic acid, 21 wt % to 26 wt % of 6-hydroxy-2-naphthoic acid, and 5 wt % to 11 wt % of p-hydroxycinnamic acid; and a polyimide film disposed on the liquid crystal polymer film through a thermocompression process; wherein the polyimide film is capable of separating from the liquid crystal polymer film.

4. The composite film according to claim 3, wherein a thickness of the composite film ranges from 20 m to 300 m.

5. The composite film according to claim 3, wherein a dielectric constant of the composite film of liquid crystal polymer and polyimide ranges from 1 to 5.

6. The composite film according to claim 3, wherein a dielectric dissipation of the composite film of liquid crystal polymer and polyimide ranges from 0.0001 to 0.12.

7. A method for manufacturing a composite film of liquid crystal polymer and polyimide, comprising steps of: providing a liquid crystal polymer containing 63 wt % to 74 wt % of p-hydroxybenzoic acid, 21 wt % to 26 wt % of 6-hydroxy-2-naphthoic acid, and 5 wt % to 11 wt % of p-hydroxycinnamic acid; and disposing the liquid crystal polymer on a polyimide film through a thermocompression process to form the composite film of liquid crystal polymer and polyimide.

8. The method according to claim 7, wherein a set temperature of the thermocompression process ranges from 150 C. to 360 C.

9. The method according to claim 7, wherein a set pressure of the thermocompression process ranges from 10 kg/cm.sup.2 to 3000 kg/cm.sup.2.

10. The method according to claim 7, wherein duration of the thermocompression process ranges from 5 seconds to 60 seconds.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0042] The present disclosure will become more fully understood from the following detailed description and accompanying drawings.

[0043] FIG. 1 is a cross-sectional view of a copper clad laminate of the present disclosure.

[0044] FIG. 2 is a cross-sectional view of a four-layered printed circuit board of the present disclosure.

[0045] FIG. 3 is a cross-sectional view of a six-layered printed circuit board of the present disclosure.

[0046] FIG. 4 is a side view of a blown film machine with laminating equipment.

[0047] FIG. 5 is a partial enlarged view of section V of FIG. 4.

[0048] FIG. 6 is a schematic view of a double steel belt thermocompressor.

[0049] FIG. 7 is a flowchart of a method for manufacturing a composite film of liquid crystal polymer and polyimide of the present disclosure.

DETAILED DESCRIPTION OF THE EXEMPLARY EMBODIMENTS

[0050] The present disclosure is more particularly described in the following examples that are intended as illustrative only since numerous modifications and variations therein will be apparent to those skilled in the art. Like numbers in the drawings indicate like components throughout the views. As used in the description herein and throughout the claims that follow, unless the context clearly dictates otherwise, the meaning of a, an, and the includes plural reference, and the meaning of in includes in and on. Titles or subtitles can be used herein for the convenience of a reader, which shall have no influence on the scope of the present disclosure.

[0051] The terms used herein generally have their ordinary meanings in the art. In the case of conflict, the present document, including any definitions given herein, will prevail. The same thing can be expressed in more than one way. Alternative language and synonyms can be used for any term(s) discussed herein, and no special significance is to be placed upon whether a term is elaborated or discussed herein. A recital of one or more synonyms does not exclude the use of other synonyms. The use of examples anywhere in this specification including examples of any terms is illustrative only, and in no way limits the scope and meaning of the present disclosure or of any exemplified term. Likewise, the present disclosure is not limited to various embodiments given herein. Numbering terms such as first, second or third can be used to describe various components, signals or the like, which are for distinguishing one component/signal from another one only, and are not intended to, nor should be construed to impose any substantive limitations on the components, signals or the like.

[0052] A liquid crystal polymer is provided. The liquid crystal polymer film includes:

[0053] A. 63 wt % to 74 wt % of p-hydroxybenzoic acid;

[0054] B. 21 wt % to 26 wt % of 6-hydroxy-2-naphthoic acid; and

[0055] C. 5 wt % to 11 wt % of p-hydroxycinnamic acid.

[0056] The liquid crystal polymer film is produced by a blown film machine and is continuously rolled up by film laminating equipment. Two sides of the liquid crystal polymer film are fixed by the film laminating equipment so as to prevent the liquid crystal polymer film from deforming, forming wrinkles, and being hardened or embrittled due to a drop of temperature which may negatively impact the quality of the liquid crystal polymer film Subsequently, the liquid crystal polymer film is exposed to UV light, thermocompressing onto a polyimide film to form a composite film by a double steel belt thermocompressor. After being heated by a heater, the composite film is rolled up to complete the method for manufacturing the composite film of liquid crystal polymer and polyimide and to achieve the aim stated above. Further, properties of the composite film of liquid crystal polymer and polyimide are stable and will not change over time. The composite film of liquid crystal polymer and polyimide manufactured by the method of the present disclosure is flat and has few wrinkles.

[0057] The monomer in the liquid crystal resin to polymerize the liquid crystal polymer of the present disclosure is selected from the group consisting of a benzene ring, a naphthalene ring, and monomers including a benzene structure or a naphthalene structure with good heat resistance. Further, the main reacting functional group of the monomer is hydroxyl group or carboxylic acid group. In some embodiments, the monomer is modified by branched vinyl group, terminally branched hexenyl group, or terminally and medially branched vinyl group. In a preferable embodiment, the monomer can be p-hydroxycinnamic acid including medially branched vinyl group. The preferable addition amount of p-hydroxycinnamic acid is 5 wt % to 11 wt %. A more specific illustration thereof is provided below.

[0058] [UV Light Irradiation to Increase the Crosslinking Density]

[0059] After forming the liquid crystal polymer film in the step of blowing film, the liquid crystal polymer film is exposed to ultraviolet (UV) light to proceed photochemical reaction on carbon-carbon double bonds so that the degree of crosslinking of the liquid crystal polymer film can be increased. Specifically, the UV light can be a UV light with a single wavelength of 185 nm, a UV light with single wavelength of 254 nm, or a UV light with various wavelengths. For example, the UV light can be a UV light with wavelengths of 185 nm and 254 nm.

[0060] It should be noted that the composite film of liquid crystal polymer and polyimide of the present disclosure is manufactured by disposing a liquid crystal polymer film on a polyimide film, instead of mixing liquid crystal polymer with polyimide to form a mixed film After the step of blowing film, if the thickness of the liquid crystal polymer film is thicker than 150 m, the liquid crystal polymer film will have a disadvantage of having a rough surface. If the thickness of the liquid crystal polymer film is thinner than 15 m, the liquid crystal polymer film cannot be provided with high dielectric constant (Dk) and low dielectric dissipation (Df).

[0061] In the thermocompression process, the liquid crystal polymer film is thermocompressed on a polyimide film at a temperature ranging from 150 C. to 360 C. by a double steel belt thermocompressor. In a preferable embodiment, the temperature range regulated in the thermocompression process is from 200 C. to 320 C. In addition, duration time regulated in the thermocompression process is over 5 seconds; preferably, duration time regulated in the thermocompression process is over 8 seconds so as to form the composite film. The thickness of the composite film can range from 20 m to 300 m; preferably, the thickness of the composite film can range from 30 m to 200 m.

[0062] 1. Thickness Measurement

[0063] A square sample with a length of 50 mm is cut from a central part of the liquid crystal polymer film. The square sample is measured by a film thickness consecutive tester (Fuji, S-2268) over 30 cm at machine direction (MD) and 30 cm at transverse direction (TD) so that an average longitudinal thickness and an average lateral thickness of the square sample can be obtained.

[0064] 2. Thickness Uniformity

[0065] A square sample with a length of 50 mm is cut from a central part of the liquid crystal polymer film. The square sample is measured by a film thickness consecutive tester (Fuji, S-2268) over 30 cm at machine direction (MD) and 30 cm at transverse direction (TD) so that an average longitudinal thickness and an average lateral thickness of the square sample can be obtained. A value to analyze the thickness uniformity is a difference between the maximum thickness and the minimum thickness.

[0066] 3. Average Roughness Sa

[0067] The average roughness Sa is measured by a non-contact surface roughness detector (Laser Micro scope VK-X1000) to process an optical microscope analysis. The measuring conditions are listed below:

[0068] (a) magnification: 5024;

[0069] (b) measuring length: 282 m; and

[0070] (c) measuring width: 247 m.

[0071] 4. Wrinkles of the Liquid Crystal Polymer Film

[0072] A sample in a size of A4 is cut from the liquid crystal polymer film to serve as a sample. The appearance of the sample is observed by naked eye and evaluated according to standards below.

[0073] : the flatness of the liquid crystal polymer film is good as an amount of the wrinkles on the liquid crystal polymer film is 0 to 1;

[0074] : the flatness of the liquid crystal polymer film is normal as an amount of the wrinkles on the liquid crystal polymer film is 2 to 3;

[0075] X: the flatness of the liquid crystal polymer film is bad as an amount of the wrinkles on the liquid crystal polymer film is over 3.

[0076] 5. Measurement of Dielectric Constant

[0077] The dielectric constant of the liquid crystal polymer film is measured by a vector network analyzer (Anritsu, ME7838E) at a frequency of 101 GHz.

[0078] 6. Measurement of Dielectric Dissipation

[0079] The dielectric dissipation of the liquid crystal polymer film is measured by a vector network analyzer (Anritsu, ME7838E) at a frequency of 105 GHz.

[0080] Examples below are provided for illustration of the embodiments. However, the example illustrated above is only one of the available embodiments and should not be taken as limitation of the scope of the present disclosure.

Example 1

[0081] The liquid crystal resin includes: A. p-hydroxybenzoic acid; B. 6-hydroxy-2-naphthoic acid; and C. p-hydroxycinnamic acid. The mass ratio of A/B/C is 68/24/8.

[0082] Referring to FIG. 7, the liquid crystal polymer film is prepared by a blown film machine. Two sides the liquid crystal polymer film are fixed by the film laminating equipment of the blown film machine so that the liquid crystal polymer film will not generate wrinkles or deform due to a drop of temperature and will have a flat surface with no wrinkles.

[0083] The liquid crystal polymer film with a thickness of 50 m is exposed to UV light to increase the degree of crosslinking Subsequently, the liquid crystal polymer film is thermocompressed on a polyimide film with a thickness of 50 m by a double steel belt thermocompressor so that the composite film of liquid crystal polymer and polyimide is formed and the adhesive force between the liquid crystal polymer film and the polyimide film is good. The double steel belt thermocompressor has two steel plates respectively disposed on a relative top end and a relative bottom end. In Example 1, the set temperature of the double steel belt thermocompressor is 250 C. and the set pressure of the double steel belt thermocompressor is 50 kg/cm.sup.2. The various physical properties of the composite film of liquid crystal polymer and polyimide are listed in Table 1.

Example 2

[0084] The composite film of liquid crystal polymer and polyimide in Example 2 is manufactured by a similar method as illustrated in Example 1. The difference between Example 2 and Example 1 is that the mass ratio of A/B/C in the liquid crystal resin is 70/24/6. The liquid crystal resin is used to form the liquid crystal polymer film by the blown film machine.

[0085] The liquid crystal polymer film with a thickness of 50 m is exposed to UV light to increase the degree of crosslinking Subsequently, the liquid crystal polymer film is thermocompressed on a polyimide film with a thickness of 75 m by the double steel belt thermocompressor so that the composite film of liquid crystal polymer and polyimide is formed. The double steel belt thermocompressor has two steel plates respectively disposed on a relative top end and a relative bottom end. In Example 2, the set temperature of the double steel belt thermocompressor is 230 C. and the set pressure of the double steel belt thermocompressor is 100 kg/cm.sup.2. The various physical properties of the composite film of liquid crystal polymer and polyimide are listed in Table 1.

Example 3

[0086] The composite film of liquid crystal polymer and polyimide in Example 3 is manufactured by a similar method as illustrated in Example 1. The difference between Example 3 and Example 1 is that the mass ratio of A/B/C in the liquid crystal resin is 73/25/2. The liquid crystal resin is used to form the liquid crystal polymer film by the blown film machine.

[0087] The liquid crystal polymer film with a thickness of 25 m is exposed to UV light to increase the degree of crosslinking Subsequently, the liquid crystal polymer film is thermocompressed on a polyimide film with a thickness of 50 m by the double steel belt thermocompressor so that the composite film of liquid crystal polymer and polyimide is formed and the adhesive force between the liquid crystal polymer film and the polyimide film is good. The double steel belt thermocompressor has two steel plates respectively disposed on a relative top end and a relative bottom end. In Example 3, the set temperature of the double steel belt thermocompressor is 230 C. and the set pressure of the double steel belt thermocompressor is 80 kg/cm.sup.2. The various physical properties of the composite film of liquid crystal polymer and polyimide are listed in Table 1.

Comparative Example 1

[0088] The composite film of liquid crystal polymer and polyimide in Comparative Example 1 is manufactured by a similar method as illustrated in Example 1. The difference between Comparative Example 1 and Example 1 is that the mass ratio of A/B/C in the liquid crystal resin is 60/20/20. The liquid crystal resin is used to form the liquid crystal polymer film by the blown film machine.

[0089] The liquid crystal polymer film with a thickness of 75 m is exposed to UV light to increase the degree of crosslinking Subsequently, the liquid crystal polymer film is thermocompressed on a polyimide film with a thickness of 100 m by the double steel belt thermocompressor so that the composite film of liquid crystal polymer and polyimide is formed and the adhesive force between the liquid crystal polymer film and the polyimide film is good. The double steel belt thermocompressor has two steel plates respectively disposed on a relative top end and a relative bottom end. In Comparative Example 1, the set temperature of the double steel belt thermocompressor is 260 C. and the set pressure of the double steel belt thermocompressor is 100 kg/cm.sup.2. The various physical properties of the composite film of liquid crystal polymer and polyimide are listed in Table 1.

Comparative Example 2

[0090] The composite film of liquid crystal polymer and polyimide in Comparative Example 2 is manufactured by a similar method as illustrated in Example 1. The difference between Comparative Example 2 and Example 1 is that the mass ratio of A/B/C in the liquid crystal resin is 50/40/10. The liquid crystal resin is used to form the liquid crystal polymer film by the blown film machine.

[0091] The liquid crystal polymer film with a thickness of 100 m is exposed to UV light to increase the degree of crosslinking Subsequently, the liquid crystal polymer film is thermocompressed on a polyimide film with a thickness of 125 m by the double steel belt thermocompressor so that the composite film of liquid crystal polymer and polyimide is formed and the adhesive force between the liquid crystal polymer film and the polyimide film is good. The double steel belt thermocompressor has two steel plates respectively disposed on a relative top end and a relative bottom end. In Comparative Example 2, the settemperature of the double steel belt thermocompressor is 270 C. and the set pressure of the double steel belt thermocompressor is 100 kg/cm.sup.2. The various physical properties of the composite film of liquid crystal polymer and polyimide are listed in Table 1.

TABLE-US-00001 TABLE 1 Comparative Example Example 1 2 3 1 2 Liquid crystal polymer film Mass ratio of 68/24/8 70/24/6 73/25/2 60/20/20 50/40/10 A/B/C Thickness (m) 50 50 25 75 100 Uniformity of 3.5 4 3.8 6 8 thickness(m) Surface 2.4 2.8 2.6 3.1 4.3 roughness(m) Wrinkles X X evaluation Polyimide film Thickness (m) 50 75 50 100 125 Thermocompression parameters Temperature 250 230 230 260 270 ( C.) Pressure 50 100 80 100 100 (kg/cm.sup.2) Duration 8 15 6 20 25 (second) Dielectric properties of the composite film Dk (101 GHz) 3.4 3.5 3.6 3.8 3.9 Df (101 GHz) 0.0021 0.0025 0.003 0.0032 0.0039

[0092] [Results and Discussion]

[0093] According to results, a preferable component and content of the liquid crystal resin includes A. 68 wt % of p-hydroxybenzoic acid; B. 24 wt % of 6-hydroxy-2-naphthoic acid; and C. 8 wt % of p-hydroxycinnamic acid. The liquid crystal resin is used to form the liquid crystal polymer film by the blown film machine. The liquid crystal polymer film is exposed to UV light to process photochemical reaction on carbon-carbon double bonds so that the degree of crosslinking and the toughness of the liquid crystal polymer film can be increased. If the content of C. p-hydroxycinnamic acid is larger than 20 wt %, the liquid crystal polymer film will be hardened and embrittled after the UV irradiation. If the content of C. p-hydroxycinnamic acid is smaller than 5 wt %, the texture of the liquid crystal polymer film will be soft.

[0094] In the thermocompressing process, the double steel belt thermocompressor machine has two steel plates respectively disposed on a relative top end and a relative bottom end. The liquid crystal polymer film and the polyimide film are thermocompressed to form the composite film. If the set temperature of the double steel belt thermocompressor is over 279 C., the liquid crystal polymer film cannot separate from the polyimide film. If the set temperature of the double steel belt thermocompressor is lower than 100 C., the liquid crystal polymer film will tend to peel from the polyimide film easily.

[0095] In conclusion, the liquid crystal polymer film, and the composite film of liquid crystal polymer and polyimide and the manufacturing method thereof of the present disclosure have the technical feature of regulating the component and content of the liquid crystal film to maintain the dielectric constant of the composite film higher than or equal to 3.0 and the dielectric dissipation of the composite film lower than or equal to 0.003. Therefore, the composite film of liquid crystal polymer and polyimide can be applied to the high frequency substrate so as to provide good processability to the high frequency substrate.

[0096] The foregoing description of the exemplary embodiments of the disclosure has been presented only for the purposes of illustration and description and is not intended to be exhaustive or to limit the disclosure to the precise forms disclosed. Many modifications and variations are possible in light of the above teaching.

[0097] The embodiments were chosen and described in order to explain the principles of the disclosure and their practical application so as to enable others skilled in the art to utilize the disclosure and various embodiments and with various modifications as are suited to the particular use contemplated. Alternative embodiments will become apparent to those skilled in the art to which the present disclosure pertains without departing from its spirit and scope.