Flexible metal laminate and preparation method of the same

Abstract

This disclosure relates to a flexible metal laminate including a porous polyimide resin layer including 30 wt % to 95 wt % of a polyimide resin, and 5 wt % to 70 wt % of fluorine-containing resin particles, wherein micropores having a diameter of 0.05 μm to 20 μm are distributed in the porous polyimide resin layer, and a method for preparing the same.

Claims

1. A flexible metal laminate, comprising: a porous polyimide resin layer comprising 30 wt % to 95 wt % of a polyimide resin, and 5 wt % to 70 wt % of fluorine-containing resin particles, and a metal thin film layer provided on at least one side of the porous polyimide resin layer, wherein the fluorine-containing resin particles have an average particle diameter (D50) of 0.05 μm to 9.5 μm, wherein micropores having a diameter of 0.05 μm to 20 μm are uniformly distributed in the porous polyimide resin layer, wherein the porous polyimide resin layer has a density of 1.2 g/cm.sup.2 to 1.9 g/cm.sup.2, and wherein the porous polyimide resin layer comprises 0.1 vol % to 2 vol % of the micropores.

2. The flexible metal laminate according to claim 1, wherein the polyimide resin has a weight average molecular weight of 1000 to 500,000.

3. The flexible metal laminate according to claim 1, wherein the porous polyimide resin layer has a thickness of 0.1 μm to 200 μm.

4. The flexible metal laminate according to claim 1, wherein the fluorine-containing resin particles include at least one compound selected from the group consisting of polytetrafluoroethylene (PTFE), a tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA), a tetrafluoroethylene-hexafluoropropylene copolymer (FEP), an ethylene-tetrafluoroethylene copolymer resin (ETFE), a tetrafluoroethylene-chlorotrifluoroethylene copolymer (TFE/CTFE), and an ethylene-chlorotrifluoroethylene resin (ECTFE).

5. The flexible metal laminate according to claim 1, wherein the porous polyimide resin layer has a dielectric constant of 2.7 or less at 5 GHz.

6. The flexible metal laminate according to claim 1, wherein the flexible metal laminate comprises one or more porous polyimide resin layers.

7. The flexible metal laminate according to claim 1, further comprising at least one thermoplastic polyimide resin layer having a thickness of 0.1 μm to 200 μm.

8. The flexible metal laminate according to claim 1, wherein the metal thin film comprises at least one metal selected from the group consisting of copper, iron, nickel, titanium, aluminum, silver, gold, and alloys of two or more of the foregoing metals.

9. The flexible metal laminate according to claim 8, wherein the metal thin film has a thickness of 0.1 μm to 50 μm.

10. A method for preparing a flexible metal laminate of claim 1, comprising the steps of: thermally curing a resin composition comprising 30 wt % to 95 wt % of a polyamic acid resin and 5 wt % to 70 wt % of fluorine-containing resin particles at a temperature range of around 280° C. to 320° C. while varying a temperature-raising rate to form a porous polyimide resin layer; depositing a metal thin film layer on at least one side of the porous polyimide resin layer, wherein the step of forming a porous polyimide resin layer comprises raising the temperature of the resin composition at a rate of 3° C./min to 10° C./min at a temperature range of equal to or less than 300° C., and raising the temperature at a rate of 0.2° C./min to 2° C./min at a temperature range of greater than 300° C.

11. The method according to claim 10, wherein the temperature raising is completed at 340° C. to 370° C.

12. The method according to claim 10, wherein the step of forming a porous polyimide resin layer further comprises coating the resin composition on a substrate to a thickness of 0.1 μm to 200 μm, before the thermal curing.

13. The method according to claim 10, wherein the step of depositing a metal thin film on at least one side of the porous polyimide resin layer comprises depositing a metal thin film comprising at least one metal selected from the group consisting of copper, iron, nickel, titanium, aluminum, silver, gold, and alloys of two or more of the foregoing metals on at least one side of the porous polyimide resin layer, while applying pressure of 500 Kgf to 3000 Kgf at a temperature of 250° C. to 450° C.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 shows a cross-sectional SEM photograph of a polyimide resin.

DETAILED DESCRIPTION OF THE EMBODIMENTS

(2) Hereinafter, the present invention will be explained in detail with reference to the following examples. However, these examples are only to illustrate the invention, and the scope of the invention is not limited thereto.

Preparation Examples: Preparation of Polyamic Acid Solution

Preparation Example 1: Preparation of Polyamic Acid Solution Including Fluorine-Containing Resin (P1)

(3) A 1 L polyethylene (PE) bottle was charged with nitrogen, 765 g of dimethylacetamide (DMAc), 219 g of polytetrafluoroethylene (PTFE) micropowder (particle size: about 1.0 μm to 5.0 μm), and 765 g of beads having a diameter of 2 mm were introduced therein, and the resultant was stirred in a ball milling apparatus.

(4) Into a 500 mL round-bottom flask, 16 g of a solution in which the PTFE micropowder was dispersed, 107 g of dimethylacetamide, 13 g of pyromellitic dianhydride, and 20 g of 2,2′-bis(trifluoromethyl)-4,4′-diaminobiphenyl were introduced, and the resultant was reacted while stirring and while flowing nitrogen at 50° C. for 10 h therein to obtain a polyamic acid solution (P1) having a viscosity of about 25,000 cps.

Preparation Example 2: Preparation of a Polyamic Acid Solution Including Fluorine-Containing Resin (P2)

(5) A 1 L polyethylene (PE) bottle was charged with nitrogen, 765 g of dimethylacetamide (DMAc), 219 g of polytetrafluoroethylene (PTFE) micropowder (particle size: about 1.0 μm to 5.0 μm), and 765 g of beads having a diameter of 2 mm were introduced therein, and the resultant was stirred in a ball milling apparatus.

(6) Into a 500 mL round-bottom flask, 73 g of a solution in which the PTFE micropowder was dispersed, 115 g of dimethylacetamide, 11.609 g of pyromellitic dianhydride, and 17.391 g of 2,2′-bis(trifluoromethyl)-4,4′-diaminobiphenyl were introduced, and the resultant was reacted while stirring and while flowing nitrogen at 50° C. therein for 10 h to obtain a polyamic acid solution (P2) having a viscosity of about 100,000 cps.

Preparation Example 3: Preparation of a Polyamic Acid Solution Including Fluorine-Containing Resin (P3)

(7) Into a 500 mL round-bottom flask, 107 g of dimethylacetamide, 13 g of pyromellitic dianhydride, and 20 g of 2,2′-bis(trifluoromethyl)-4,4′-diaminobiphenyl were introduced, and the resultant was reacted while stirring and while flowing nitrogen at 50° C. therein for 10 h to obtain a polyamic acid solution (P3) having a viscosity of about 25,000 cps.

Examples 1 and 2 and Comparative Examples 1 and 2: Preparation of a Polyimide Resin Film for a Flexible Metal Laminate and a Flexible Metal Laminate

Examples 1 and 2

(8) (1) Preparation of a Polyimide Resin Film

(9) The polyamic acid solutions respectively prepared in Preparation Examples 1 to 2 were coated on the matte side of a copper foil (thickness: 12 μm) so that the final thickness became 25 μm, and then dried at 80° C. for 10 min. The temperature of the dried product was raised from room temperature at a rate of 5° C./min at a temperature range of equal to or less than 300° C., and curing was progressed at a rate of 1° C./min at a temperature range of greater than 300° C. and 350° C. or less. After the curing was completed, the copper foil was etched to prepare a polyimide resin film with a thickness of 25 μm.

(10) (2) Preparation of Flexible Metal Laminate

(11) By applying pressure of 1700 Kgf to the polyimide resin films respectively obtained in Examples 1 and 2 and the copper foil with a thickness of 12 μm at 380° C. to laminate them, a metal laminate was prepared.

Comparative Example 1

(12) (1) Preparation of a Polyimide Resin Film

(13) A polyimide resin film with a thickness of 25 μm was prepared by the same method as Example 1, except using the polyamic acid solution obtained in Preparation Example 3 instead of the polyamic acid solution prepared in Preparation Example 1.

(14) (2) Preparation of a Flexible Metal Laminate

(15) By applying pressure of 1700 Kgf to the above-obtained polyimide resin film and the copper foil with a thickness of 12 μm at 380° C. to laminate them, a metal laminate was prepared.

Comparative Example 2

(16) (1) Preparation of a Polyimide Resin Film

(17) The polyamic acid solution of Preparation Example 2 was coated on the matte side of the copper foil (thickness: 12 μm) so that the final thickness became 25 μm, and then dried at 80° C. for 10 min. The temperature of the dried product was raised from room temperature in a nitrogen oven, and curing was progressed at 350° C. for 30 min.

(18) After the curing was completed, the copper foil was etched to prepare a polyimide resin film with a thickness of 25 μm.

(19) (2) Preparation of a Flexible Metal Laminate

(20) By applying pressure of 1700 Kgf to the above-obtained polyimide resin film and the copper foil with a thickness of 12 μm at 380° C. to laminate them, a metal laminate was prepared.

Experimental Example

1. Experimental Example 1: Observation of the Cross-Section of the Flexible Metal Laminate

(21) The cross-section of the copper foil laminate obtained in Example 1 was confirmed through SEM photography. As shown in FIG. 1, it was confirmed that micropores having a diameter of 0.05 μm to 20 μm were distributed in the polyimide resin layer obtained in Example 1.

2. Experimental Example 2: Measurement of the Physical Properties of the Flexible Metal Laminate

(22) For the copper foil laminates obtained in the examples and comparative examples, the dielectric constant, CTE, and absorptivity were measured as follows, and the results are shown in the following Table 1.

(23) (1) Measurement Method of Dielectric Constant

(24) The polyimide resin films obtained in the examples and comparative examples were dried at 150° C. for 30 min, and the dielectric constant of each polyimide resin film was measured using a resonator, Agilent E5071 B ENA, under conditions of 25° C. and 50% RH, by a split post dielectric resonance (SPDR) method.

(25) (2) Measurement Method of Coefficient of Linear Thermal Expansion (CTE)

(26) The coefficients of linear thermal expansion of the polyimide resin films obtained in the examples and comparative examples were measured using a TMA/SDTA 840 apparatus (Mettler Company) under a measurement condition of 100° C. to 200° C., according to the standard of IPC TM-650 2.4.24.3.

(27) (3) Measurement Method of Absorptivity

(28) According to the standard of IPC TM-650 2.6.2C, the polyimide resin films obtained in the examples and comparative examples were immersed in distilled water at 23° C. for 24 h, and the masses before and after the immersion were measured to calculate absorptivities.

(29) TABLE-US-00001 TABLE 1 Measurement results of Experimental Example 2 Measurement results Porous polyimide of Experimental resin layer Example 2 Diameter Dielectric of constant absorp- micropores Density (Dk) CTE tivity (μm) (g/cm.sup.2) @ 5 GHz (ppm) (%) Example 1 about 0.5 to 2 1.30 2.6 12 1.5 Example 2 about 0.5 to 2 1.40 2.4 22 1.1 Comparative — 1.27 2.9 9 1.7 Example 1 Comparative — 1.5 2.6 23 1.1 Example 2

(30) As shown in Table 1, it was confirmed that micropores having a diameter of 0.5 μm to 2 μm were distributed in the porous polyimide resin layers obtained in Examples 1 and 2, and that the densities of the polyimide resin layers were 1.30 cm.sup.2 to 1.40 g/cm.sup.2. It was also confirmed that the porous polyimide resin layers prepared in Examples 1 and 2 have low dielectric constants of 2.6 or less and low absorptivities of 1.5% or less, and yet have coefficients of linear expansion of 12 to 22 ppm.

(31) To the contrary, it was confirmed that micropores were not formed in the polyimide resin layers of Comparative Examples 1 and 2, where Comparative Example 1 exhibited a relatively high dielectric constant (2.9), a low coefficient of linear expansion, and high absorptivity, and Comparative Example 2 had relatively high density and a relatively high dielectric constant compared to Example 2 having an identical PTFE content.