TWI821550B - Manufacturing method of polyimide composite film for flexible metal foil substrate - Google Patents

Abstract

The invention refers to a method for manufacturing a polyimide composite film for a flexible metal foil substrate, which includes the following steps: providing a polyimide solution; providing a fluorine polymer particle, and combining it with a dispersant and The organic solution is mixed to prepare a fluorine polymer particle dispersion; the polyamide acid solution is made into a colloidal polyimide film; the fluorine polymer particle dispersion is coated on the colloidal polyimide film , and then baked to form a polyimide composite film.

Description

Manufacturing method of polyimide composite film for flexible metal foil substrate

The invention relates to a method for manufacturing a polyimide composite film for a flexible metal foil substrate. The method involves coating a fluorine polymer particle dispersion on a colloidal polyimide film and then baking it to form a film. , in order to achieve the effect of improving the production yield of polyimide composite film.

Flexible printed circuit boards have been widely used in various electronic products in daily life, such as the bending parts of mobile phones, tablet devices, notebook computers and other products. This kind of flexible printed circuit board and its covering base material must consider the electrical properties, heat resistance, chemical resistance and dimensional stability of the material. Therefore, polyimide is usually used as the base material of the flexible printed circuit board and the covering layer.

In recent years, with the arrival of 5G high-frequency transmission applications, high transmission frequency and high data transmission volume, signal loss may occur during the transmission process. In order to effectively reduce signal loss, it is particularly important to reduce the dielectric constant (Dk) and dielectric loss (Df) of the polyimide film. The Dk and Df of the polyimide film can be reduced through molecular structure design. However, the current limit is that Dk is still higher than 3.0 and Df is higher than 0.004 at 10GHz.

Among various polymer materials, fluorine polymers are known to have lower Dk and Df materials, with Dk<2.5 and Df<0.001 at 10GHz. Therefore, relevant developers have tried to use them in metal foil-clad substrate materials. For example, glass fiber cloth is impregnated with fluorine polymer and pressed with copper foil to make a substrate; another example is that fluorine polymer is coated on a polyimide film and pressed with copper foil.

A method for manufacturing a polyimide composite film for a flexible metal foil substrate. The method involves coating a fluorine polymer particle dispersion on the surface of a previously prepared polyimide film, drying it, and then drying it. It is melted in a high-temperature oven to form a film. However, in the continuous roll-to-roll coating production process, the surface energy difference between the dried fluoropolymer particles and the polyimide film is too large, and the affinity of the interface between the two is very poor, causing the fluoropolymer particles to The surface layer of the polyimide membrane is prone to peeling off, causing problems such as membrane surface defects and production line pollution, thus limiting the use and production of the composite membrane. Moreover, the fluorine polymer is coated on the polyimide film surface and then baked at high temperature. Since the fluorine polymer shrinks when melted, the composite film will be curled or wavy, which will affect the yield. In addition, the above-mentioned composite film method is to first complete the production of the polyimide film base material and then apply the fluorine polymer particle dispersion. This requires more than two coating processes and high-temperature processes, which has a negative impact on cost and yield. have a considerable impact.

The present invention is a method for manufacturing a polyimide film for a flexible metal foil substrate, which is characterized by including the following steps: providing a polyimide solution; providing a fluorine polymer particle, and combining it with a dispersant; Mixing organic solutions to prepare a fluorine polymer particle dispersion; making the polyamide acid solution into a colloidal polyimide film; and coating the fluorine polymer particle dispersion on the colloidal polyimide film on the film, and then baked to form a polyimide composite film.

Therefore, the present invention has the following effects: 1. Improve the adhesion between the fluorine polymer particle layer and the colloidal polyimide film during the production process, thereby preventing film surface defects and production line pollution caused by powder falling off during production; 2. . Single-sided or double-sided composite layer coating can be completed directly during the polyimide film production process, which can shorten and simplify the manufacturing process of the composite film and avoid curling; 3. The present invention can improve the performance of flexible metal foil-clad substrates The bonding strength between metal foil and composite film.

S1: Provide a polyamide solution

S2: Preparation of monofluoropolymer particle dispersion

S3: Make the polyamide acid solution into a colloidal polyimide membrane

S4: Coat the fluorine polymer particle dispersion on both sides of the colloidal polyimide film

S5: Bake to form polyimide composite film

10: Fluorine polymer particle dispersion

12: Colloidal polyimide membrane

14: Fluorine polymer layer

16:Polyimide membrane

Figure 1 is a flow chart of the manufacturing method of the polyimide composite film for flexible metal foil-clad substrates according to the present invention.

Figure 2 is a first schematic diagram of the present invention.

Figure 3 is a second schematic diagram of the present invention.

Please refer to the first to third figures. The manufacturing method of the polyimide composite film for flexible metal foil-clad substrates of the present invention includes the following steps: providing a polyimide solution (S1), which is composed of two Obtained by mixing and reacting amine and dianhydride; providing monofluoropolymer particles, mixing them with a dispersant and an organic solution to prepare a monofluoropolymer particle dispersion 10 (S2); adding the polyamide solution The colloidal polyimide film 12 is made (S3); and the fluorine polymer particle dispersion 10 is coated on both sides of the colloidal polyimide film 12 (S4), and then baked to make the fluorine The fluoropolymer particle dispersion 10 and the colloidal polyimide film 12 form a fluoropolymer layer 14 and a polyimide film 16 respectively to form a polyimide composite film (S5).

Step S1: Preparation of polyamide solution

One or more diamines and one or more dianhydride monomers are provided for mixing and reaction to polymerize into a polyamide solution.

Among them, the diamine monomer can be: 4,4'-diaminodiphenyl ether (4,4' - ODA), 3,4'-diaminodiphenyl ether (3,4' - ODA), m-phenylene ether Diamine (MPD), p-phenylenediamine (PPD), 2,2'-bis(trifluoromethyl)diaminobiphenyl (TFMB), 4,4'-diaminodiphenyl-2,2-propane , 4,4'-diaminodiphenylmethane, 4,4'-diaminodiphenylamine, benzidine, 4,4'-diaminodiphenyl sulfide, 4,4'-diaminodiphenyl Turine, 3,3'-diaminodiphenyl styrene, 4,4'-diamino-2,2'-dimethyl-1,1'-biphenyl, 4,4'-diamino-3, 3'-1,1'-dimethylbiphenyl, 1,5-diaminonaphthalene, 3,3'-dimethoxybenzidine, 1,4-bis-(p-aminophenoxy) -Benzene, 1,3-bis-(p-aminophenoxy)-benzene, or any mixture thereof.

Among them, the dianhydride monomer can be: pyromellitic dianhydride (PMDA), 2,3,6,7-naphthalenetetracarboxylic dianhydride, 3,3',4,4'-biphenyltetracarboxylic dianhydride Anhydride, 1,2,5,6-naphthalenetetracarboxylic dianhydride, 2,2',3,3'-biphenyltetracarboxylic dianhydride, 2,2-bis-(3,4-dicarboxyphenyl )-propane dianhydride, bis-(3,4-dicarboxyphenyl)-terebic dianhydride, bis-(3,4-dicarboxyphenyl)-ether dianhydride, 2,2-bis-(2,3 -Dicarboxyphenyl)-propane dianhydride, 1,1-bis-(2,3-dicarboxyphenyl)-ethane dianhydride, 1,1-bis-(3,4-dicarboxyphenyl)- Ethane dianhydride, bis-(2,3-dicarboxyphenyl)-methane dianhydride, bis-(3,4-dicarboxyphenyl)-methane dianhydride, 3,4,3',4'-di benzophenone tetracarboxylic dianhydride, or any mixture thereof.

Step S2: Preparation of fluorine polymer particle dispersion

Fluorine polymers that can be used in the present invention include: polychlorotrifluoroethylene (PCTFE), fluorinated ethylene propylene copolymer (FEP), polyvinyl fluoride (PVF), polyvinylidene fluoride (PVDF), ethylene trifluorochlorine It is composed of one or more of ethylene copolymer (ECTFE), tetrafluoroethylene perfluoroether copolymer (PFA), and ethylene tetrafluoroethylene copolymer (ETFE). Fluorine polymers are in the form of particles dispersed in organic solvents. The average particle size is 1 to 20 microns, preferably 1 to 10 microns. If the particle size is too small, it will be difficult to disperse, and if the particle size is too large, the film surface will be uneven. . The melting point of the fluorine polymer should be between 260°C and 350°C, so that the particles can be melted and formed into a film while being baked during the manufacturing process of the polyimide colloidal film. It also ensures the reliability of subsequent high-temperature processes for flexible substrates.

The composition of the fluorine polymer particle dispersion includes: fluorine polymer particles account for the total dispersion 10~60% by weight of liquid, preferably 30~50% by weight, to ensure a tight structure between particles after coating and drying; 2~7% by weight of dispersant, preferably 2~5%, the addition amount is too low to achieve The fluorine polymer particles are evenly dispersed. If it is too high, it will affect the characteristics of the fluorine layer. In addition, an additional polyamide solution can also be added to increase the structural stability of the fluorine layer. The amount added should be less than the total solid content of the dispersion. 20% by weight, preferably 10% by weight or less. Too high an added amount will reduce the dielectric properties of the fluorine layer. The configuration method is: add fluorine polymer particles into the mixed solvent of dispersant and solvent, and disperse it with a homogenizer for 2 hours. In another example, after the above dispersion is completed, 20% polyamide solution is added and mixed with a homogenizer.

Step S3: Preparation of colloidal polyimide film substrate

Mix a dehydrating agent such as acetic anhydride and a catalyst such as triethylamine, pyridine, isoquinoline or picoline in a polyamide solvent, apply it on the support, and bake it at a temperature ranging from 50 to 150°C. Transform it into a colloidal film. The solvent content of the colloidal polyimide film is controlled by adjusting the baking temperature curve of the oven, and the baking temperature range is 50~150°C. The solvent content of colloidal polyimide membranes ranges from 20 to 60% by weight. A solvent content above 60% by weight will cause defects on the film surface at high temperatures. A solvent content below 20% by weight will not have good affinity with the fluorine polymer particles. .

Step S4: Coating with fluorine polymer particle dispersion

The fluorine polymer particle dispersion can be coated on one or both sides of the colloidal polyimide film. The coating method is not limited, and slot die, micro gravure, comma coating, and roll coating can be used.

Step S5: Bake to form polyimide composite film

After the fluorine polymer particle dispersion is coated on the colloidal polyimide film, it is baked in the high-temperature section. The temperature of the high-temperature oven is between 150~550°C, and the maximum temperature is preferably 350~550°C to ensure that the polyimide film is The imine film is completely closed-looped and the fluorine polymer particles are melted to form a film. It is baked while extending in the TD direction to avoid the shrinkage phenomenon causing uneven film surface.

In order to verify the efficacy of the present invention, the semi-finished polyimide composite film whose fluorine polymer particle layer has been dried but has not yet been melted into a film was taken out from the baking section below 200°C, and a hundred-grid adhesion test was conducted in accordance with ASTM D3359 specifications.

Flexible metal foil substrate production

The flexible metal foil substrate of the present invention is formed by continuously pressing the above-mentioned polyimide composite film and metal foil using a heated metal rolling machine or a double-belt hot press. A vacuum flat hot press can also be used. Evaluate the experimental results of polyimide composite membranes. The composition of the metal foil is not particularly limited, including copper, nickel, aluminum and other metals or alloys. Electrolytic copper foil or rolled copper foil is commonly used, and the thickness is not particularly limited.

Example 1

Step S1: Preparation of polyamide solution

Dissolve 10Kg (50mole%) of 4,4'-diaminodiphenyl ether and 5.4Kg (50mole%) of p-phenylenediamine in 157Kg of dimethylacetamide (DMAc), then take 10.9Kg (50mole) %) of pyromellitic dianhydride and about 14.7Kg (50 mole%) of 3,3',4,4'-biphenyltetracarboxylic dianhydride were added for reaction to obtain a 20% polyamic acid solution.

Step S2: Preparation of fluorine polymer particle dispersion

After mixing 30Kg of dimethylacetamide solvent and 0.4Kg of dispersant, 20Kg of PFA particles were added to the above solution, and then stirred with a homogenizer at 5000rpm for 2 hours to obtain a 40% by weight fluorine polymer particle dispersion.

Step S3: Preparation of colloidal polyimide film substrate

Mix the polyamic acid solution with the dehydrating agent and the catalyst. The molar ratio of polyamic acid: dehydrating agent: catalyst is 1:2:1. Apply it on the steel plate, bake it in the oven, and then apply it on the steel plate. Peel off to obtain a solvent content of 60%. Colloidal polyimide film.

Step S4: Coating with fluorine polymer particle dispersion

The fluorine polymer particle dispersion is coated on both sides of the colloidal polyimide film.

Step S5: Bake to form polyimide composite film

Enter the high-temperature oven section for baking. The temperature of the high-temperature oven is between 150 and 550°C to obtain a polyimide composite film covered with a fluorine polymer layer on both sides. The thickness is fluorine polymer layer/polyimide film/ Fluorine polymer layer = 12 microns/50 microns/microns, and conduct appearance evaluation.

During the baking process, the semi-finished polyimide composite film whose fluorine polymer particle layer has been dried but has not yet been melted into a film is obtained in the baking section below 200°C, and a hundred-grid test is carried out.

Soft copper-clad substrate production

Take the above-mentioned polyimide composite film with a size of 20cm×30cm and laminate it with copper foil (Mitsui Metal TQ-M4-VSP 12um, Rz: 0.6 micron) using a vacuum flat plate hot press. The lamination conditions are as follows: temperature rise from room temperature to 340°C at 5°C per minute, and constant temperature at 340°C for 10 minutes. The pressure is 30Kgf/cm ² . After completion, the copper foil adhesion strength test is performed.

Solvent content test of colloidal polyimide membrane

Colloidal film solvent content = (colloidal film weight - dry film weight) × 100/colloidal film weight

The dry film weight is the weight of the colloidal polyimide film after baking it in an oven at 200°C for 12 minutes.

Hundred grid test

According to ASTM D3359, the hundred-grid test results are divided into 5B: no shedding; 4B: less than 5% shedding; 3B: 5~15% shedding; 2B: 15~35% shedding; 1B: 35~65% shedding; 0B: higher than 65% fell off.

Hand touch test

Use your fingers to directly press and contact the fluorine polymer layer of the semi-finished polyimide composite film to observe whether there is peeling, powder loss, etc.

Appearance evaluation

Visually confirm whether there are any appearance defects caused by peeling of the fluorine layer in the area of 20cm×30cm of the polyimide composite film. It is divided into A: no defects; B: less than 3 defects; C: more than 3 defects.

Copper foil adhesion test

The test method is in accordance with the standard of IPC-TM-650 2.4.9 to test the peel strength of the copper foil and polyimide composite film.

Example 2

Repeat the steps of Example 1, but control the baking temperature in step S3 to obtain a colloidal polyimide film with a solvent content of 30%.

Example 3

Repeat the steps of Example 1, but control the baking temperature in step S3 to obtain a colloidal polyimide film with a solvent content of 20%.

Example 4

Repeat the steps of Example 2, except that 20% by weight of polyamide relative to the total solid composition is added to the fluorine polymer particle dispersion produced in step S2, as in step B.

Step B: Preparation of fluorine polymer particle dispersion

After mixing 17.5Kg of dimethylacetamide solvent and 0.4Kg of dispersant, add 25Kg of the polyamide solution prepared in step S1 and 20Kg of PFA particles into the above solution, and then stir with a homogenizer at 5000rpm for 2 hours, as 40% by weight fluorine polymer particle dispersion.

Comparative example 1

Repeat the steps of Example 1, but control the baking temperature in step S3 to obtain a colloidal polyimide film with a solvent content of 70%.

Comparative example 2

Repeat steps S1 and S2 of Example 1, and continue with steps C, D and E.

Step C. Preparation of polyimide film substrate

Mix the polyamic acid solution with a dehydrating agent and a catalyst in a molar ratio of polyamic acid:dehydrating agent:catalyst of 1:2:1, apply it on the steel plate, and bake it in an oven before peeling off the steel plate. , and then enter the high-temperature oven for baking, and then a polyimide film with complete reaction and drying is obtained as the base material.

Step D. Fluorine polymer particle dispersion coating

The fluorine polymer particle dispersion is coated on both sides of the polyimide film prepared in step C.

Step E: Baking to form polyimide composite film

Enter the oven for baking. The high-temperature oven temperature is between 150 and 550°C to obtain a polyimide composite film covered with a fluorine polymer layer on both sides. The thickness is fluorine polymer layer/polyimide film/fluorine. Polymer layer = 12 microns/50 microns/12 microns, and conduct appearance evaluation.

During the baking process, the semi-finished polyimide composite film whose fluorine polymer particle layer has been dried but has not yet been melted into a film is obtained in the baking section below 200°C, and is subjected to a hundred grid test and a hand touch test.

Comparative example 3

Repeat the steps of comparison 2, except that 20% by weight of polyamide relative to the total solid composition is added to the fluorine polymer particle dispersion produced in step S2, as in step B.

Examples 1 to 3 are compared with Comparative Example 2. Comparing the semi-finished products, in the example, the fluorine polymer particle dispersion is coated on the colloidal polyimide film, which has better adhesion than coating on the dry film, and does not fall off when touched directly. After completing step D, the appearance of Examples 1 to 3 is obviously better than that of Comparative Example 2.

Comparing Examples 1 to 3 with Comparative Example 1, in the Examples, coating the fluorine polymer particle dispersion on the colloidal polyimide film significantly helps the adhesion of the fluorine coating layer, but in Comparative Example 1 , when the solvent content of the colloidal polyimide film is higher than 70%, cracks on the film surface will occur.

Example 2, Example 4 and Comparative Example 3 are compared. Comparing the semi-finished products, adding a polyamide solution as an adhesive between the fluorine particles and coating it on the colloidal film significantly improved the adhesion; although Comparative Example 3 was coated on the dry film, the adhesion was improved, but the 100-square test Only promoted to B1.

Examples 1 to 4 have a significant improvement in the adhesion with the copper foil, which is due to the improvement in the adhesion between the polyimide base film and the fluorine polymer layer.

Those skilled in the art will understand that various changes or modifications made to the present invention without departing from the scope defined in the appended patent application are part of the present invention.

S1: Provide a polyamide solution

S2: Preparation of monofluoropolymer particle dispersion

S3: Make the polyamide acid solution into a colloidal polyimide membrane

S4: Coat the fluorine polymer particle dispersion on both sides of the colloidal polyimide film

S5: Bake to form polyimide composite film

Claims (8)

A method for manufacturing a polyimide composite film for a flexible metal foil-covered substrate, which allows metal foil to be attached to the composite film. The method includes the following steps: providing a polyimide solution; and providing a fluorine polymer particle. , its average particle size is 1~20 microns, and its melting point is 260-350°C. Mix it with a dispersant and an organic solution to prepare a monofluoropolymer particle dispersion. The dispersant accounts for 2~7% of the weight of the dispersion. %, in which the solid weight percentage of the fluorine polymer dispersion is 30~50wt%; the polyamide acid solution is coated on a support, and a colloidal polyimide film is formed on the support by a closed-loop method , the solvent content of the colloidal polyimide film is between 20 and 60% by weight, and the colloidal polyimide film is peeled off from the support; and the fluorine polymer particle dispersion is coated on the peeled on the colloidal polyimide film, and then bake it at 150~550°C to form a polyimide composite film with a fluorine polymer layer. As described in item 1 of the patent application, the method for manufacturing a polyimide composite film for flexible metal foil substrates, wherein the polyamide acid solution is mixed and reacted with diamine and dianhydride monomers in an organic solution. And get. As described in item 1 of the patent application, in the method for manufacturing a polyimide composite film for a flexible metal foil substrate, the fluorine polymer particle dispersion may further include a polyimide solution. As described in item 1 of the patent application, the method for manufacturing a polyimide composite film for flexible metal foil-clad substrates, wherein the solvent content of the colloidal polyimide film is between 20 and 60 wt%. As described in item 1 of the patent application, the method for manufacturing a polyimide composite film for flexible metal foil-clad substrates, wherein the baking temperature for making the colloidal polyimide film is 50 to 150°C. As described in item 1 of the patent application, the method for manufacturing a polyimide composite film for flexible metal foil-clad substrates, wherein the baking temperature of the composite film is 150~550°C. As described in item 1 of the patent application, the method for manufacturing a polyimide composite film for flexible metal foil substrates, wherein the fluorine polymer particle dispersion is coated on both sides of the colloidal polyimide film . As described in item 1 of the patent application, the manufacturing method of polyimide composite film for flexible metal foil-clad substrates, in which the hundred-grid test of the semi-finished polyimide composite film is 2B or above.

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