Resin composition for a metal substrate, and resin varnish and metal base copper-clad laminate comprising the same

Abstract

The present disclosure provides a resin composition for a metal substrate, and a resin varnish and a metal base copper-clad laminate comprising the same. The resin composition comprises 5-40% of a main resin and 60-95% of a thermally conductive filler when the total weight of the resin composition is calculated as 100%, wherein the main resin comprises 60-90% of a flexible epoxy resin having a structure as shown in Formula I and 10-40% of a phenoxy resin when the total weight of the main resin is calculated as 100%. The resin composition provided by the present disclosure has a low modulus, can alleviate the stress generated by thermal shocks and can withstand more than 1000 thermal cycles.

Claims

1. A resin composition for a metal substrate, comprising 20 weight parts of a resin mixture and 80 weight parts of a thermally conductive filler; wherein the resin mixture consists of 80% of a flexible epoxy resin having a structure as shown in Formula I, ##STR00005## 15% of a phenoxy resin with weight average molecular weight of 40,000-55,000, and 5% of a biphenyl epoxy resin having a structure as shown in Formula II or Formula III based on the total weight of the resin mixture being 100%, wherein R is selected from C2-C20 linear or branched alkylene groups; ##STR00006## n.sub.1 represents a mean repeating unit of 4-10; n represents a mean repeating unit of 1-10; wherein the thermally conductive filler comprises is selected from the group consisting of aluminum nitride, boron nitride, aluminum oxide, silicon carbide, zinc oxide and carbon nanotubes, and combinations thereof; wherein the resin composition further comprises 1 weight part of an amine curing agent selected from the group consisting of ethylenediamine, diethylenetriamine, triethylenetetramine, tetraethylenepentamine, isophoronediamine, m-phenylenediamine, m-aminomethylamine, diaminodiphenyl sulfone, dicyandiamide, diaminodicyclohexyl methane, methylcyclopentanediamine, diamine methylcyclohexanediamine, diaminodiphenylmethane, and combination thereof.

2. The resin composition for a metal substrate according to claim 1, wherein the thermally conductive filler comprises any one or a combination of at least two selected from the group consisting of boron nitride, aluminum oxide and silicon carbide.

3. The resin composition for a metal substrate according to claim 1, wherein the resin composition further comprises 0.1-2 weight parts of a curing accelerator.

4. A resin varnish obtained by dissolving or dispersing the resin composition for a metal substrate according to claim 1 into a solvent.

5. A film comprising the resin composition for a metal substrate according to claim 1.

6. A metal base copper-clad laminate comprising a metal substrate, a thermally, conductive insulating bonding layer prepared from the resin composition for a metal substrate according to claim 1 and a copper foil which are laminated together from bottom to top.

7. The metal base copper-clad laminate according to claim 6, wherein the metal substrate comprises any one selected from the group consisting of an aluminum substrate, a copper substrate, an iron substrate and a steel substrate.

8. The metal base copper-clad laminate according to claim 6, wherein the thermally conductive insulating bonding layer has a thickness of 0.04-0.20 mm.

9. The metal base copper-clad laminate according to claim 6, wherein the copper foil is an electrodeposited copper foil or a rolled copper foil; and the copper foil has a thickness of 0.012-0.210 mm.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a schematic cross-sectional view showing a metal base copper-clad laminate and a chip at a normal temperature.

(2) FIG. 2 is a schematic cross-sectional view showing a metal base copper-clad laminate and a chip in the prior art in a state of thermal expansion.

(3) FIG. 3 is a schematic cross-sectional view showing cracking of solder joints of a metal base copper-clad laminate and a chip in the prior art after thermal expansion and cooling.

(4) FIG. 4 is a schematic cross-sectional view showing a metal base copper-clad laminate and a chip in the present disclosure in a state of thermal expansion.

(5) Wherein, 1-chip; 2-solder joint; 3-copper foil circuit; 4-thermally conductive insulating bonding layer; 5-metal substrate.

DETAILED DESCRIPTION

(6) The technical solution of the present disclosure will be further described below by way of specific embodiments. It should be understood by those skilled in the art that the examples are only to help understanding the present disclosure, and shall not be construed as limiting the disclosure.

(7) It can be seen from FIGS. 1-3 that in a case where a metal base copper-clad laminate in the prior art is used (for example, an LED lighting lamp), the chip, solder joint, copper foil circuit, thermally conductive insulating bonding layer, and metal substrate are all at normal positions at a normal temperature. Once subjected to thermal expansion, the metal substrate, thermally conductive insulating bonding layer and copper foil circuit will be deformed, thereby readily rendering cracks in the solder joint or copper foil circuit after thermal expansion and cooling. However, in a case where the resin composition for use in a metal substrate of the present disclosure is used as a thermally conductive insulating bonding layer, due to the low modulus thereof, only the metal substrate and the thermally conductive insulating bonding layer are deformed, but the copper foil layer is substantially not deformed when subjected to thermal expansion, as shown in FIG. 4.

(8) Therefore, no cracking occurs in the solder joint or copper foil circuit after thermal expansion and cooling.

(9) The materials referred to in the following Examples and Comparative Examples, and brand information thereof are as follows:

(10) (A) Flexible Epoxy Resin

(11) A-1: Product model EXA-4850-150, weight per epoxy equivalent 450 g/eq, manufactured by Dainippon Ink and Chemicals Inc.;

(12) A-2: Product model EXA-4850-1000, weight per epoxy equivalent 350 g/eq, manufactured by Dainippon Ink and Chemicals Inc.;

(13) A-3: Product model EXA-4816, weight per epoxy equivalent 403 g/eq, manufactured by Dainippon Ink and Chemicals Inc., having the structure as follows:

(14) ##STR00003##

(15) wherein R is an aliphatic segment and m is 0.5-3;

(16) A-4: Product model DX7160, weight per epoxy equivalent 430 g/eq, manufactured by Jiashengde Material Technology Inc., Hunan, China, having the structure as follows:

(17) ##STR00004##

(18) wherein R is an aliphatic segment and m is 0.5-3;

(19) A-5: An ordinary bisphenol-A epoxy resin, product model NPES-901, weight per epoxy equivalent 475 g/eq, manufactured by Nanya Electronic Materials Inc.;

(20) (B) Phenoxy Resin

(21) B-1: Product model EPONOL Resin53-BH-35, weight average molecular weight 55,000, manufactured by Momenti ye;

(22) B-2: Product model PKHH, weight average molecular weight 50,000, manufactured by Inchem;

(23) B-3: Product model ERF-001, weight average molecular weight 40,000, manufactured by Nippon Steel Chemical;

(24) B-4: Product model YP-50SB, weight average molecular weight 25,000, manufactured by Tohto Kasei;

(25) B-5: Product model YP-50, weight average molecular weight 70,000, manufactured by Tohto Kasei;

(26) (C) Biphenyl Epoxy Resin

(27) C-1: Product model NC-3000H, weight per epoxy equivalent 285 g/eq, manufactured by Nippon Kayaku Inc.;

(28) C-2: Product model YX-4000, weight per epoxy equivalent 185 g/eq, manufactured by Mitsubishi Chemical Inc.;

(29) (D) Curing Agent

(30) D-1: Triethylenetetramine;

(31) D-2: Diaminodiphenyl sulfone;

(32) D-3: An active ester, product model HPC-8000-651, manufactured by Dainippon Ink and Chemicals Inc.;

(33) (E) Thermally Conductive Filler

(34) E-1: Alumina, Sumitomo, Japan;

(35) E-2: Boron nitride, Momentive, American;

(36) (F) Curing Accelerator

(37) F-1: 2-Methylimidazole

EXAMPLES 1-15

(38) Resin compositions were prepared in accordance with the components shown in Tables 1-2, and metal base copper-clad laminate samples were prepared in accordance with the preparation method below.

(39) The components in the formula amount were uniformly mixed in a solvent, and the solid content of the varnish was controlled to be 75%. The varnish was applied to a copper foil having a thickness of 35 μm, and dried at 155° C. for 5 minutes to obtain a copper foil (having a thickness of 35 μm) with a semi-cured thermally conductive insulating bonding layer (having a thickness of 100 μm), which was then laminated with a surface-treated aluminum plate (having a thickness of 1.0 mm) to obtain an aluminum-based copper-clad laminate.

COMPARATIVE EXAMPLES 1-11

(40) Resin compositions were prepared in accordance with the components shown in Tables 3 and 4, and metal base copper-clad laminate samples were prepared in accordance with the preparation method described in the examples.

(41) TABLE-US-00001 TABLE 1 Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 Example 7 Example 8 A-1 16 16 16 16 16 16 16 A-2 16 A-3 A-4 A-5 B-1 3 3 3 3 B-2 3 B-3 3 B-4 3 B-5 3 C-1 1 1 1 1 1 1 1 C-2 1 D-1 0.2 0.2 0.2 0.2 0.2 0.2 0.2 1 D-2 0.8 0.8 0.8 0.8 0.8 0.8 0.8 D-3 E-1 80 80 80 80 80 80 80 60 E-2 20 F-1 0.1 0.1 0.1 0.1 0.1 0.1 0.1 0.1

(42) TABLE-US-00002 TABLE 2 Example 9 Example 10 Example 11 Example 12 Example 13 Example 14 Example 15 A-1 16.8 12 18 12 32 4 16 A-2 A-3 A-4 A-5 B-1 3.2 8 2 4 4 0.5 3 B-2 B-3 B-4 B-5 C-1 4 1 C-2 4 0.5 D-1 0.2 0.2 0.2 0.2 0.4 0.2 D-2 0.8 0.8 0.8 0.8 1.6 0.8 D-3 1 E-1 80 80 80 80 60 95 80 E-2 F-1 0.1 0.1 0.1 0.1 0.1 0.1 0.1

(43) TABLE-US-00003 TABLE 3 Comp. Comp. Comp. Comp. Comp. Example 1 Example 2 Example 3 Example 4 Example 5 A-1 20 A-2 A-3 16 A-4 16 A-5 16 B-1 3 3 3 20 B-2 B-3 B-4 B-5 C-1 1 1 1 C-2 D-1 0.2 0.2 0.2 0.2 0.2 D-2 0.8 0.8 0.8 0.8 0.8 D-3 E-1 80 80 80 80 80 E-2 F-1 0.1 0.1 0.1 0.1 0.1

(44) TABLE-US-00004 TABLE 4 Comp. Comp. Comp. Comp. Comp. Comp. Example 6 Example 7 Example 8 Example 9 Example 10 Example 11 A-1 3.2 40 10 18 11 18.5 A-2 A-3 A-4 A-5 B-1 0.6 7.5 9 1 8 0.5 B-2 B-3 B-4 B-5 C-1 0.2 2.5 1 1 1 1 C-2 D-1 0.05 0.2 0.2 0.2 0.2 0.2 D-2 0.2 0.8 0.8 0.8 0.8 0.8 D-3 E-1 96 50 80 80 80 80 E-2 F-1 0.1 0.1 0.1 0.1 0.1 0.1

(45) Performance Test 1

(46) The metal base copper-clad laminates provided in Examples 1-15 and Comparative Examples 1-11 were tested for performance as follows:

(47) (1) Thermal conductivity/thermal impedance: The metal substrates were made into samples of 25.4 mm×25.4 mm to test the thermal conductivity/thermal impedance of the laminates by referring to the ASTM D5470 test method;

(48) (2) Thermal resistance (288° C.): The thermal resistance of the laminates was tested by referring to the experimental conditions in the IPC-TM-650 2.4.13 method;

(49) (3) Modulus: The modulus of the insulating bonding layers was tested by referring to the experimental conditions in the IPC-TM-650 2.4.24.4 method;

(50) (4) Number of thermal cycles: After several thermal cycles between −50° C. and 150° C., the laminates were sliced and analyzed for the binding of each layer to determine whether delamination occurred;

(51) (5) Operationality: The evaluation was carried out based on convenience in actual use: no stickiness was evaluated as “excellent”, a little stickiness was evaluated as “good”, and stickiness was evaluated as “poor”;

(52) (6) Voltage resistance test: The voltage resistance of the thermally conductive insulating layers was tested according to the method in T/CPCA 4105-2016. The average value of 5 points was calculated;

(53) (7) Weight average molecular weight: Performed using the test method specified in GB/T 21863-2008 gel permeation chromatography (GPC) using tetrahydrofuran as the eluent. (The molecular weight of the phenoxy resin was determined by the weight average molecular weight test).

(54) The test results are shown in Tables 5-8.

(55) TABLE-US-00005 TABLE 5 Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 Example 7 Example 8 Thermal 2.0 2.0 2.0 2.0 2.0 2.0 2.0 3.0 conductivity (W/m .Math. K) 288° C. 10 8 10 10 10 10 10 10 Thermal resistance (min) 50° C. 420 800 440 450 800 350 430 600 Modulus (MPa) Number of 1500 1300 1500 1500 1300 1500 1500 1500 thermal cycles (times) Operability Excellent Excellent Excellent Excellent Excellent Good Excellent Excellent Voltage 5000 5000 5000 5000 5000 5000 5000 5000 resistance (V)

(56) TABLE-US-00006 TABLE 6 Example 9 Example 10 Example 11 Example 12 Example 13 Example 14 Example 15 Thermal 2.0 2.0 2.0 2.0 1.5 5.0 2.0 conductivity (W/m .Math. K) 288° C. 9 9 9 10 6 6 6 Thermal resistance (min) 50° C. 400 600 300 800 300 1500 1500 Modulus (MPa) Number of 1500 1500 1500 1300 1500 1300 1200 thermal cycles (times) Operability Excellent Excellent Excellent Excellent Excellent Excellent Excellent Voltage 5000 5000 5000 5000 5000 3500 4000 resistance (V)

(57) TABLE-US-00007 TABLE 7 Comp. Comp. Comp. Comp. Comp. Example 1 Example 2 Example 3 Example 4 Example 5 Thermal 2.0 2.0 2.0 2.0 2.0 conductivity (W/m .Math. K) 288° C. 5 5 5 5 5 Thermal resistance (min) 50° C. 900 850 10500 250 2100 Modulus (MPa) Number of 900 850 500 1000 800 thermal cycles (times) Operability Excellent Excellent Excellent poor Excellent Voltage 4000 4000 5000 4000 5000 resistance (V)

(58) TABLE-US-00008 TABLE 8 Comp. Comp. Comp. Comp. Comp. Comp. Example 6 Example 7 Example 8 Example 9 Example 10 Example 11 Thermal 7.0 0.8 2.0 2.0 2.0 2.0 conductivity (W/m .Math. K) 288° C. 2 5 8 8 8 8 thermal resistance (min) 50° C. 3000 200 1000 280 900 270 Modulus (MPa) Number of 800 1300 900 1300 900 1300 thermal cycles (times) Operability Excellent Good Excellent Poor Excellent Poor Voltage 2000 5000 5000 5000 5000 5000 resistance (V)

(59) It can be seen from the Examples and the Performance Test that the metal base laminates prepared by the disclosure have better comprehensive performance, wherein the 288° C. thermal resistance is 6 min or more; the number of thermal cycles is 1200 or more; and the operability is excellent. All laminates can satisfy the application requirements.

(60) As can be seen from the comparison between Example 1 and Examples 3-6, when the weight average molecular weight of the phenoxy resin is not within the range of 30,000 to 65,000, for example, when the weight average molecular weight of the phenoxy resin of Example 5 is less than 30,000, the laminate sample has a number of thermal cycles of 1300; and for another example, when the weight average molecular weight of the phenoxy resin of Example 6 is higher than 65,000, there are some certain influence on operability. As can be seen from the comparison between Example 1 and Examples 9-11, when no biphenyl epoxy resin is added, the laminate sample has a poor 288° C. thermal resistance, which is 9 min. As can be seen from the comparison between Example 1 and Examples 13-14, when the main resin accounts for 40% of the total weight of the resin composition, the laminate sample has a low modulus at 50° C., but has a thermal conductivity of 1.5 W/m.Math.K, and a 288° C. thermal resistance of 6 min. While when the thermally conductive filler accounts for 95% of the total weight of the resin composition, the thermal conductivity of the laminate sample is significantly increased; but the modulus at 50° C. achieves 1500 MPa; and the 288° C. thermal resistance is 6 min.

(61) As can be seen from the comparison between Example 1 and Example 15, the use of the active ester curing agent greatly increases the modulus of the laminate sample; and its 288° C. thermal resistance is 6 min, and the voltage resistance value is as low as 4000 V.

(62) As can be seen from the comparison between Example 1 and Comparative Examples 1-3, although the laminate samples in Comparative Examples 1-2 can also obtain a low modulus, but they have a poor 288° C. thermal resistance and poor thermal cycle property, which is because the flexible epoxy used in Comparative Examples 1-2 contains a hydroxyl structure. Since Comparative Example 3 used an ordinary bisphenol-A epoxy resin, its modulus at 50° C. is as high as 10,500 MPa, and its 288° C. thermal resistance and thermal cycle property are also poor. As can be seen from the comparison between Example 1 and Comparative Example 4, when only a flexible epoxy resin is used in the main resin, the resulting laminate sample has a poor thermal resistance and operability.

(63) As can be seen from the comparison between Example 1 and Comparative Example 5, when only a phenoxy resin is used in the main resin, the resulting laminate sample has a poor 288° C. thermal resistance and poor thermal cycle property, and has a modulus up to 2,100 MPa. As can be seen from the comparison between Example 1 and Comparative Examples 6 and 7, when the addition amount of the main resin is not within the range of 5 to 40%, for example when the addition amount is too small, the laminate has a high modulus and a poor thermal resistance and thermal cycle property; when the addition amount is too high, the thermal conductivity is reduced, the thermal resistance is poor, and the operability is affected to some extent. As can be seen from the comparison between Example 1 and Comparative Examples 8 and 11, when the amount of the flexible oxygen resin added to the main resin is too small, and the amount of the phenoxy resin added to the main resin is too high, the laminate has a high modulus, a slightly poor thermal resistance and poor thermal cycle property; when the amount of the flexible oxygen resin added to the main resin is too high, and the amount of the phenoxy resin added to the main resin is too small, the laminate has a poor thermal resistance and poor operability. As can be seen from the comparison between Example 1 and Comparative Examples 9-10, when the amount of the phenoxy resin added to the main resin is too small, the laminate has a poor thermal resistance and poor operability; when the amount of the flexible epoxy resin to the main resin is too small, the laminate has high modulus, and poor thermal resistance and thermal cycle property.

EXAMPLES 16-19

(64) The difference from Example 1 was that the resin composition provided in Example 1 was kept unchanged, but the thickness of the thermally conductive insulating bonding layer was changed. The thicknesses of the thermally conductive insulating bonding layers in resulting aluminum-based copper-clad laminates were 40 μm (Example 16), 200 μm (Example 17), 30 μm (Example 18) and 220 μm (Example 19).

(65) Performance Test 2

(66) The metal base copper-clad laminates provided in Examples 16-19 were tested for performance by referring to Performance Test 1. The test results are shown in Table 9.

(67) TABLE-US-00009 TABLE 9 Example 16 Example 17 Example 18 Example 19 Thermal 0.2 1.0 0.15 1.1 impedance (° C. .Math. cm.sup.2/W) 288° C. 10 10 10 10 Thermal resistance (min) 50° C. 420 420 420 420 Modulus (MPa) Number of 1200 1500 1000 1500 thermal cycles (times) Operability Excellent Excellent Excellent Excellent Voltage 3000 8000 2000 8000 resistance (V)

(68) As can be seen from the comparison between Example 1, Examples 16-17 and Examples 18-19, the preferable thickness of the thermally conductive insulating bonding layer of the present disclosure is 0.04-0.20 mm. The metal base copper-clad laminate having such thickness prepared by the present disclosure has better comprehensive performance. If the thermally conductive insulating bonding layer has a too small thickness, the stress generated by thermal shocks cannot be sufficiently alleviated, and the voltage resistance is low. If the thermally conductive insulating bonding layer has a too high thickness, although the stress generated by thermal shocks can be sufficiently alleviated, the thermal impedance becomes high, which is not conducive to the rapid heat dissipation of the metal substrate.

(69) The applicant has stated that the resin composition for use in a metal substrate of the present disclosure, the resin varnish and the metal base copper-clad laminate comprising the same are described by the above embodiments, but the present disclosure is not limited to the above process steps. That is, it does not mean that the present disclosure must rely on the above process steps to implement. Those skilled in the art shall know that any modifications to the present disclosure, equivalent replacements of the materials selected in the present disclosure, the addition of the auxiliary ingredients, and the selection of specific manner all fall within the scope of protection and disclosure of the present disclosure.