Composite LCP high-frequency high-speed double-sided copper foil substrate and preparation method thereof

Abstract

The invention discloses a composite LCP high-frequency high-speed double-sided copper foil substrate, which includes at least one LCP core layer, at least one extremely low dielectric adhesive layer, and two copper foil layers. The LCP core layer and the extremely low dielectric adhesive layer are located between the two copper foil layers. The invention has not only good electrical performance but also low roughness, stable dk/df performance in high temperature and humid environment, ultra-low water absorption, good UV laser drilling ability, low spring force suitable for high density assembly, and excellent mechanical properties. Besides, in current technology, only a thickness limited to a maximum of about 50 μm can be obtained in the coating method. In the preparation method of the invention, a substrate having a thickness of 100 μm or more can be easily obtained.

Claims

1. A composite liquid crystalline polymer (LCP) high-frequency high-speed double-sided copper foil substrate, comprising layers in the following order: a first copper foil layer; a liquid crystalline polymer (LCP) core layer; a low dielectric adhesive layer; a second copper foil layer; and wherein a thickness of the LCP core layer is 22.5-50 μm, a thickness of the low dielectric adhesive layer is 12.5-50 μm, a thickness of each of the first and second copper foil layers is 1-35 μm, a Dk value of the low dielectric adhesive layer is between 2.8 to 3.0 (10 GHz) and a Df value of the low dielectric adhesive layer is 0.01 (10 GHz).

2. The composite LCP high-frequency high-speed double-sided copper foil substrate according to claim 1, wherein a total thickness of the LCP core layer, the low dielectric adhesive layer, the first copper foil layer, and the second copper foil layer is 37-170 μm.

3. The composite LCP high-frequency high-speed double-sided copper foil substrate according to claim 1, wherein the double-sided copper foil substrate further comprises: a second LCP core layer located between the low dielectric adhesive layer and the second copper foil layer; wherein a total thickness of the LCP core layer, the low dielectric adhesive layer, the second LCP core layer, the first copper foil layer, and the second copper foil layer is 42-220 μm.

4. The composite LCP high-frequency high-speed double-sided copper foil substrate according to claim 1, wherein each copper foil layer is a low-profile copper foil layer having an Rz value of 0.4 to 1.0 μm, and an Rz value of a surface of the copper foil layer that is attached to the LCP core layer is 0.4 to 1.0 μm, and an Rz value of an outer surface of the copper foil layer is 0.4 to 0.7 μm; and each copper foil layer is a rolled copper foil layer or an electro deposited copper layer.

5. The composite LCP high-frequency high-speed double-sided copper foil substrate according to claim 1, wherein a water absorption of the LCP core layer is 0.01-0.1%; a water absorption of the low dielectric adhesive layer is 0.01-0.1%; an overall water absorption of the double-sided copper foil substrate is 0.01-0.5%, and a bonding strength of the low dielectric adhesive layer is more than 0.7 kgf/cm.sup.2.

6. The composite LCP high-frequency high-speed double-sided copper foil substrate according to claim 1, wherein a resin material of the low dielectric adhesive layer is at least one selected from the group consisting of fluorine-based resin, epoxy resin, acrylic resin, amine-based formate-based resin, silicone rubber-based resin, poly-p-xylene based resin, bismaleimide-based resin, and polyimide resin.

7. The composite LCP high-frequency high-speed double-sided copper foil substrate according to claim 1, wherein the low dielectric adhesive layer comprises fused silicon dioxide, Teflon, fluorine-based resin, phosphorus-based heat-resistant agent and polyimide resin; and all of the fused silicon dioxide, the Teflon, the fluorine-based resin, and the phosphorus-based heat-resistant agent is 8% to 50% of total solid content by weight; a proportion of the polyimide resin is 40 to 90% by weight.

8. The composite LCP high-frequency high-speed double-sided copper foil substrate according to claim 7, wherein the fused silicon dioxide is 2 to 15% of the total solid content by weight, the Teflon is 2 to 10% of the total solid content by weight, the fluorine-based resin is 2 to 10% of the total solid content by weight, the phosphorus-based heat-resistant agent is 2 to 15% of the total solid content by weight.

9. The composite LCP high-frequency high-speed double-sided copper foil substrate according to claim 5, wherein the water absorption of the LCP core layer is 0.01-0.04%; the water absorption of the low dielectric adhesive layer is 0.01-0.08%; the overall water absorption of the double-sided copper foil substrate is 0.01-0.1%.

10. A method of preparing the composite LCP high-frequency high-speed double-sided copper foil substrate of claim 1, comprising the following steps: 1) coating a LCP varnish on one side of a first copper foil layer, and then removing a solvent at 60-100° C., and then conducting condensation reaction at 300° C. for 10 hours to generate a LCP core layer; 2) coating an extremely low dielectric adhesive on a surface of the LCP core layer, and conducting drying to obtain an extremely low dielectric adhesive layer; 3) pressing a second copper foil layer on a surface of the extremely low dielectric adhesive layer; and 4) conducting winding and curing to obtain a finished product.

11. A method of preparing the composite LCP high-frequency high-speed double-sided copper foil substrate of claim 1, comprising the following steps: 1) coating a LCP varnish on one side of a first copper foil layer, and then removing a solvent at 60-100° C., and then conducting condensation reaction at 300° C. for 10 hours to generate a first LCP core layer; 2) coating an extremely low dielectric adhesive on a surface of the first LCP core layer, and conducting drying to obtain an extremely low dielectric adhesive layer; 3) coating the LCP varnish in the step 1) on the extremely low dielectric adhesive layer, and then removing the solvent at 60-100° C., and then conducting condensation reaction at 300° C. for 10 hours to generate a second LCP core layer; 4) pressing the second copper foil layer on a surface of the second LCP core layer; and 5) conducting winding and curing to obtain a finished product.

12. The composite LCP high-frequency high-speed double-sided copper foil substrate according to claim 1, wherein the thickness of the low dielectric adhesive layer is 15-50 μm and the thickness of each of the first and second copper foil layers is 1-5 μm.

13. The composite LCP high-frequency high-speed double-sided copper foil substrate according to claim 1, wherein the thickness of the low dielectric adhesive layer is 15-50 μm and the thickness of each of the first and second copper foil layers is 20-35 μm.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a structural schematic diagram of the present invention where there is only one LCP core layer.

(2) FIG. 2 is another one of the structural schematic diagram of the present invention where there are two LCP core layer.

(3) The parts in the drawings are labeled as follows:

(4) 100—first copper foil layer, 200—LCP core layer, 201—first LCP core layer, 202—second LCP core layer, 300—extremely low dielectric adhesive layer, and 400—second copper foil layer.

DETAILED DESCRIPTION OF THE INVENTION

(5) The advantages and effects of the present invention will be readily apparent to those skilled in the art by illustrating the specific embodiments of the present invention. Further, the present invention can be implemented in other different ways. That is to say, modifications and variations can be made without departing from the scope of the present invention.

(6) Embodiment: A composite LCP high-frequency high-speed double-sided copper foil substrate, as shown in FIG. 1 and FIG. 2, includes at least one LCP core layer, at least one extremely low dielectric adhesive layer, and two copper foil layers.

(7) The LCP core layer and the extremely low dielectric adhesive layer are located between the two copper foil layers.

(8) The thickness of each LCP core layer is 5-50 μm. The thickness of each extremely low dielectric adhesive layer is 2-50 μm. The thickness of each copper foil layer is 1-35 μm.

(9) Preferably, the thickness of each LCP core layer is 12.5-50 μm, the thickness of each extremely low dielectric adhesive layer is 12.5-50 μm, and the thickness of each copper foil layer is 6-18 μm.

(10) The double-sided copper foil substrate has one of two structures as below.

(11) The first structure comprises a LCP core layer 200, an extremely low dielectric adhesive layer 300, a first copper foil layer 100, and a second copper foil layer 400. The LCP core layer is located between the first copper foil layer and the extremely low dielectric adhesive layer. The extremely low dielectric adhesive layer is located between the second copper foil layer and the LCP core layer. The total thickness of the LCP core layer, the extremely low dielectric adhesive layer, the first copper foil layer, and the second copper foil layer is 9-170 μm, as shown in FIG. 1.

(12) The second structure comprises a first LCP core layer 201, an extremely low dielectric adhesive layer 300, a second LCP core layer 202, a first copper foil layer 100, and a second copper foil layer 400. The first LCP core layer is located between the first copper foil layer and the extremely low dielectric adhesive layer. The extremely low dielectric adhesive layer is located between the first LCP core layer and the second LCP core layer, the second LCP core layer is located between the extremely low dielectric adhesive layer and the second copper foil layer. The total thickness of the first LCP core layer, the extremely low dielectric adhesive layer, the second LCP core layer, the first copper foil layer, and the second copper foil layer is 14-220 μm, as shown in FIG. 2.

(13) The extremely low dielectric adhesive layer 300 is an adhesive layer having a Dk (Dielectric constant) value of 2.0 to 3.0 (10 GHz) and a Df (Dielectric loss factor) value of 0.002 to 0.010 (10 GHz).

(14) Preferably, the extremely low dielectric adhesive layer is an adhesive layer having a Dk value of 2.2 to 3.0 (10 GHz).

(15) Each copper foil layer is a low-profile copper foil layer having an Rz (surface roughness) value of 0.4 to 1.0 μm. The Rz value of a surface of the copper foil layer that is attached to the LCP core layer is 0.4 to 1.0 μm. The Rz value of an outer surface of the copper fail layer is 0.4 to 0.7 μm. Each copper foil layer is a rolled copper foil layer (RA/HA/HAV2) or an electro deposited copper layer (ED).

(16) The Rz value of the surface of the copper foil layer that is attached to the LCP core layer may be 0.4 μm, 0.5 μm, 0.6 μm, 0.7 μm, 0.8 μm, 0.9 μm or 1.0 μm, and the Rz value of the outer surface of the copper foil layer may be 0.4 μm, 0.5 μm, 0.6 μm or 0.7 μm.

(17) The water absorption of the LCP core layer is 0.01-0.1%. The water absorption of the extremely low dielectric adhesive layer is 0.01-0.1%. The overall water absorption of the double-sided copper foil substrate is 0.01-0.5%. The bonding strength of the extremely low dielectric adhesive layer is more than 0.7 kgf/cm.sup.2.

(18) Preferably, the water absorption of the LCP core layer is 0.01-0.04%. The water absorption of the extremely low dielectric adhesive layer is 0.01-0.08%. The overall water absorption of the double-sided copper foil substrate is 0.01-0.1%.

(19) The resin material of the extremely low dielectric adhesive layer is at least one selected from the group consisting of fluorine-based resin, epoxy resin, acrylic resin, amine-based formate-based resin, silicone rubber-based resin, poly-p-xylene based resin, bismaleimide-based resin, and polyimide resin.

(20) The extremely low dielectric adhesive layer 300 includes fused silicon dioxide, teflon, fluorine-based resin, phosphorus-based heat-resistant agent, and polyimide resin. The sum of the ratio of each of the fused silicon dioxide, the teflon, the fluorine-based resin, and the phosphorus-based heat-resistant agent to the total solid content is 8 to 50% by weight. The proportion of the polyimide resin is 40% to 90% by weight.

(21) The ratio of the fused silicon dioxide to the total solid content is 2 to 15% by weight. The ratio of the teflon to the total solid content is 2 to 10% by weight. The ratio of the fluorine-based resin to the total solid content is 2 to 10% by weight. The ration of the phosphorus-based heat-resistant agent to the total solid content is 2 to 15% by weight.

(22) A preparation method of the composite LCP high-frequency high-speed double-sided copper foil substrate is one of two methods listed as below.

(23) The first method includes the following steps.

(24) Step 1, a LCP varnish (e.g., Sumitomo Chemical. VR400) is coated on one side of the first copper foil layer, and a solvent is removed at 60-100° C. firstly, and then a condensation reaction is conducted at 300° C. for 10 hours, such that the LCP core layer is generated.

(25) Step 2, an extremely low dielectric adhesive is coated on a surface of the LCP core layer, and the LCP core layer is dried to obtain the extremely low dielectric adhesive layer.

(26) Step 3, pressing the second copper foil layer on a surface of the extremely low dielectric adhesive layer, and the pressing temperature is 50-130° C.

(27) Step 4, winding and curing are conducted to obtain a finished product.

(28) The second method includes the following steps.

(29) Step 1, the LCP varnish (e.g., Sumitomo Chemical. VR400) is coated on one side of the first copper foil layer, and the solvent is removed at 60-100° C., and then condensation reaction is conduct at 300° C. for 10 hours to generate the first LCP core layer.

(30) Step 2, the extremely low dielectric adhesive is coated on the surface of the first LCP core layer, and drying is conducted to obtain the extremely low dielectric adhesive layer.

(31) Step 3, the LCP varnish of the step 1 is coated on the extremely low dielectric adhesive layer, and the solvent is removed at 60-100° C. firstly, and then a condensation reaction is conducted at 300° C. for 10 hours, such that the second LCP core layer is generated.

(32) Step 4, the second copper foil layer is pressed on a surface of the second LCP core layer, and the pressing temperature is 50-130° C.

(33) Step 5, winding and curing are conducted to obtain a finished product.

(34) Embodiment 1 and embodiment 4 use the first method to prepare, and embodiment 2, embodiment 3, and embodiment 5 use the second method to prepare.

(35) In the embodiment of the present invention, weight percentage content of each of fused silicon dioxide, teflon, fluorine-based resin, phosphorus-based heat-resistant agent, and polyimide resin in the extremely low dielectric adhesive layer are shown in the table 1.

(36) TABLE-US-00001 TABLE 1 fused fluorine- phosphorus- silicon based based polyimide dioxide teflon resin heat-resistant resin (%) (%) (%) agent (%) (%) Embodiment 1 2 2 2 2 90 Embodiment 2 8 10 6 10 60 Embodiment 3 15 10 10 15 40 Embodiment 4 2 7 3 3 80 Embodiment 5 6 8 7 10 65 The fundamental performance of the embodiments of the present invention compared with the existing LCP substrate and PI substrate are shown in the table 2 and the table 3.

(37) TABLE-US-00002 TABLE 2 Rz (μm) Film thickness (μm) The water LCP first absorption extremely The The The and at Loss of high Spring Spring first low first second second second room speed force force copper dielectric LCP LCP copper copper temperature transmission Bonding before after foil adhesive core core foil foil for signals dB strength coating coating items layer layer layer layer layer layer 24 hr (10 GHz) (kgf/cm2) film (g) film (g) Embodiment 1 1 2 5 1 0.4 0.05 5.28 0.7 5.8 15.6 Embodiment 2 6 10 5 5 6 0.5 0.07 5.06 0.82 6.3 16.7 Embodiment 3 12 12.5 12.5 12.5 12 0.6 0.06 5.79 0.83 6.5 17.1 Embodiment 4 18 25 25 18 0.7 0.06 5.82 1.11 10.6 18.2 Embodiment 5 35 50 50 50 35 1 0.06 5.9 1.75 14.7 20.5 Comparative Normal PI substrate 1.3 9.45 0.83 18.6 35.8 example 1 Comparative Normal PI substrate 1.8 11.46 0.85 19.4 37.3 example 2 Comparative Normal LCP substrate 0.04 6.14 0.65 18.3 35.4 example 3 Comparative Normal LCP substrate 0.06 6.44 0.71 19.9 38.6 example 4

(38) TABLE-US-00003 TABLE 3 Dk (10 GHz) Df (10 GHz) After After immersion immersion Before in water at Before in water at immersion room immersion room in water at temperature Change in water at temperature change room for 24 Rate room for 24 rate solder items temperature hours (%) temperature hours (%) resistance Embodiment 1 2.31 2.30 −0.43 0.0027 0.0030 11.11 300° C.*10 S pass Embodiment 2 2.26 2.23 −1.3 0.0032 0.0036 12.50 300° C.*10 S pass Embodiment 3 2.31 2.30 −0.43 0.0027 0.0030 11.11 300° C.*10 S pass Embodiment 4 2.34 2.32 −0.85 0.0028 0.0031 10.71 300° C.*10 S pass Embodiment 5 2.33 2.31 −0.86 0.0028 0.0031 10.71 300° C.*10 S pass Comparative 3.71 3.50 −5.67 0.0213 0.0300 40.85 300° C.*10 S pass Example 1 Comparative 3.97 3.66 −7.81 0.0245 0.0356 45.31 300° C.*10 S pass Example 2 Comparative 2.3 2.30 0.00 0.0025 0.0026 4.00 288° C.*10 S pass Example 3 Comparative 2.34 2.33 −0.43 0.0026 0.0028 7.69 288° C.*10 S pass Example 4 Notes: the test method of the performance of the table 2 and the table 3 complies with testing criterion of outline for flexible board assembly (TPCA-F-002).

(39) It can be known from the table 2 and the table 3, the present invention has a better performance in water absorption and high-speed transmission than that of the general PI substrate and is equivalent to LCP substrate. At the same time, the present invention can solve the deficiencies of the LCP, TPI, such as high requirement to equipment, high operating temperature limitation of process technology, expensive cost, strong spring force, poor workability.

(40) The composite LCP high-frequency high-speed double-sided copper foil substrate of the present invention has excellent high-speed transmission property, good solder resistance, stable dk/df performance in high temperature and humid environment, ultra-low water absorption, good UV laser drilling capacity, low spring force suitable for high density assembly, and excellent mechanical properties.

(41) The present invention is superior to LCP film and ordinary PI type bonding sheet, and is suitable for wearable equipment such as 5G smart phone and Apple watch (smart watch).

(42) The above are merely embodiments of the present invention and are not intended to limit the scope of the present invention. The equivalents based on the specification and drawings of the present invention, or using either directly or indirectly in other relevant technical field, are within the scope of the scope of the present invention.