JP2003147173A - Resin composition, resin-coated metal foil, and multilayer printed circuit board - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a resin composition excellent in dielectric characteristics and cracking resistance, to provide a resin-coated metal foil, and a printed wiring board. SOLUTION: The resin composition is one which forms the insulating layer of a resin-coated metal foil and comprises a benzocyclobutene resin and an acicular inorganic filler. The resin-coated metal foil is one prepared by coating a metal foil with the resin composition. The multilayer printed circuit board is one prepared by laying the resin-coated metal foil on at least either surface of an inner layer circuit board and applying heat and pressure to the assemblage.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a resin composition, a resin-coated metal foil, and a multilayer printed circuit board.

[0002]

2. Description of the Related Art In recent years, portable electronic devices such as notebook personal computers and mobile phones are required to be lighter and more compact. Therefore, a printed circuit board on which a CPU, an LSI, or the like inside an electronic device is mounted is naturally required to be small and lightweight. In order to realize the reduction in size and weight, it is necessary to reduce the thickness of the insulating resin layer, the width of the printed wiring and the distance between the wirings, and to reduce the diameter of the through hole and thin the through hole. Here, if the plating thickness is reduced, cracks may occur in the plated metal during thermal shock, and the insulating resin is required to have heat resistance and crack resistance. At the same time, there is a demand for higher speed of these information processing devices, and the clock frequency of CPUs is increasing. Therefore, it is required to increase the signal propagation speed, and in order to realize this, a printed circuit board having a low dielectric constant and a low dielectric loss tangent is required.

A benzocyclobutene resin is used as a resin having excellent heat resistance and excellent dielectric properties (for example, Japanese Patent Laid-Open No. 2000-21872). A benzocyclobutene resin does not generate a functional group having a large polarizability such as a hydroxyl group due to a curing reaction, and therefore has excellent dielectric properties.

However, the benzocyclobutene resin is fragile in mechanical properties due to its skeletal structure, and when the benzocyclobutene resin is used for a resin-coated metal foil, there arises a problem in crack resistance against thermal shock.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to provide a resin composition excellent in dielectric properties and crack resistance, a metal foil with resin and a printed wiring board.

[0006]

These objects can be achieved by the present invention described in (1) to (11) below. (1) A resin composition constituting an insulating layer of a resin-coated metal foil, comprising a benzocyclobutene resin and an acicular inorganic filler. (2) The resin composition according to (1), wherein the benzocyclobutene resin is represented by the following formula.

[Chemical 2] (3) The resin composition according to (1) or (2) above, wherein the content of the benzocyclobutene resin is 40 to 95% by weight of the entire resin composition. (4) The inorganic filler has an average fiber diameter of 0.3 to 2.0.
The resin composition according to any one of (1) to (3) above, which has a thickness of μm. (5) The inorganic filler has an average fiber length of 0.5 to 50 μm.
The resin composition according to any one of (1) to (4) above, wherein m is m. (6) The inorganic filler is one or more needle-like inorganic fillers selected from aluminum borate, magnesia, alumina, and silicon nitride. (1) to (5) Resin composition. (7) The maximum fiber length of the inorganic filler is 10 to 50 μm.
The resin composition according to any one of (1) to (6) above, wherein (8) The content of the inorganic filler is 5 based on the whole resin composition.
The resin composition according to any one of the above (1) to (7), which is -60% by weight. (9) A resin-coated metal foil, which is obtained by applying the resin composition according to any one of (1) to (8) to a metal foil. (10) A metal foil with resin, which is formed by laminating two or more layers of the resin composition according to any one of (1) to (8). (11) The resin-coated metal foil according to (9) or (10) above is overlaid on one side or both sides of the inner layer circuit board and heated,
Multi-layer printed circuit board made by applying pressure.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION The resin composition, metal foil with resin and multilayer printed circuit board of the present invention will be described in detail below. The resin composition of the present invention is a resin composition that constitutes an insulating layer of a resin-coated metal foil, and is characterized by containing a benzocyclobutene resin and an acicular inorganic filler. The resin-coated metal foil of the present invention is characterized in that the resin composition is applied to the metal foil. Further, the multilayer printed circuit board of the present invention is obtained by superposing the above-mentioned resin-coated metal foil on one side or both sides of the inner layer circuit board and applying heat and pressure.

First, the resin composition will be described. The resin composition of the present invention constitutes the insulating layer of the resin-coated metal foil. The insulating layer of the metal foil with resin is required to have dielectric properties and impedance control. The resin composition of the present invention contains a benzocyclobutene resin. As a result, the dielectric characteristics of the insulating layer can be improved. Specifically, the relative dielectric constant of the insulating layer can be reduced. The benzocyclobutene resin is not particularly limited as long as it is a resin containing a cyclobutene skeleton. Among these, it is preferable to include a benzocyclobutene resin represented by the following formula. As a result, the glass transition temperature can be increased, and the resin characteristics (specifically, dielectric characteristics, heat resistance, etc.) after curing can be improved.

[Chemical 3] The benzocyclobutene resin does not generate a functional group having a large polarizability such as a hydroxyl group due to the curing reaction, and therefore has excellent dielectric properties and low water absorption. Moreover, it has excellent heat resistance because it has a rigid chemical structure. In addition, a B-staged benzocyclobutene resin having the above formula is also preferably used for adjusting moldability and fluidity, and is included in the present invention. B stage conversion is performed by heating and melting. The number average molecular weight of the B-staged benzocyclobutene resin is usually 3,000 to 1,0.
It is 0,000. The number average molecular weight can be measured using GPC, for example.

The content of the benzocyclobutene resin is
Although not particularly limited, it is preferably 40 to 95% by weight, and particularly preferably 50 to 90% by weight based on the entire resin composition. If the content is less than the lower limit, the effect of improving the dielectric properties such as relative dielectric constant and dielectric loss tangent may be insufficient, and if the content exceeds the upper limit, the resin flow may decrease. Examples of the resin used in combination with the benzocyclobutene resin include polybutadiene rubber, styrene-butadiene rubber, acrylonitrile-butadiene copolymer, acrylonitrile-butadiene-styrene copolymer and the like. By using these together, properties such as crack resistance of the insulating resin at the time of thermal shock are improved.

In the present invention, an acicular inorganic filler is included. Thereby, the crack resistance of the insulating resin layer can be improved. Inorganic fillers include fibrous inorganic fillers, plate-shaped inorganic fillers, spherical inorganic fillers, needle-shaped inorganic fillers, etc., but needle-shaped inorganic fillers are resistant to cracking in the insulating layer. It is excellent in giving. The needle-like inorganic filler is considered to have a linear expansion smaller and a crack resistance remarkably improved by the combination with the above-mentioned benzocyclobutene resin.

Examples of the acicular inorganic fillers include potassium titanate, wollastonite, zonolite, asbestos, aluminum borate, magnesia, alumina and silicon nitride. Among these, one or more needle-like inorganic fillers selected from aluminum borate, magnesia, alumina and silicon nitride are preferable. Thereby, the mechanical strength of the resin composition can be further improved. The inorganic filler is not particularly limited, but so-called whiskers are preferably used. Thereby, the mechanical strength of the resin composition can be further improved.

The average fiber diameter of the above-mentioned inorganic filler is not particularly limited, but is preferably 0.3 to 2.0 μm, and particularly preferably 0.
5 to 1.0 μm is preferable. If the average fiber diameter is less than the lower limit value, the mechanical strength of the resin composition may decrease, and if it exceeds the upper limit value, the insulation reliability of the insulating resin layer may decrease. The average fiber length of the inorganic filler is not particularly limited, but is preferably 0.5 to 50 μm, and particularly preferably 1 to 20 μm. If the average fiber length is less than the lower limit value, the effect of decreasing the linear expansion of the resin composition may be insufficient, and if it exceeds the upper limit value, the insulation reliability of the insulating resin layer may decrease. Most preferably, the inorganic filler has an average fiber diameter of 0.5 to 1.0 μm and an average fiber length of 1 to 20 μm. When the fiber diameter and the fiber length are within the above ranges, the mechanical strength can be improved without particularly lowering the insulation reliability.

The maximum fiber length of the inorganic filler is not particularly limited, but is preferably 10 to 50 μm, particularly 15 to 3
0 μm is preferable. If the maximum fiber length is less than the lower limit, the effect of improving the crack resistance may be insufficient, and if the maximum fiber length exceeds the upper limit, the insulation reliability of the insulating resin layer may deteriorate and the laser via processability may be poor. It may be sufficient.
The aspect ratio of the inorganic filler is not particularly limited, but 1.1 or more is preferable, and 1.5 to 60 is particularly preferable. When the aspect ratio is less than the lower limit, the effect of improving crack resistance may be reduced, and when the aspect ratio is more than the upper limit, the insulation reliability of the insulating resin layer may be deteriorated or the laser via processability may be insufficient. There is.

The content of the inorganic filler is not particularly limited, but is preferably 5 to 60% by weight of the total resin composition,
Particularly, 10 to 50% by weight is preferable. When the content of the inorganic filler is less than the lower limit, the effect of improving the crack resistance of the insulating layer may be reduced, and when the content exceeds the upper limit, the insulation reliability of the insulating resin layer is reduced and the laser via is applied. Workability may be insufficient.

Next, the resin-coated metal foil will be described.
The resin-coated metal foil of the present invention is a resin-coated metal foil obtained by applying the resin composition to a metal foil. When the resin composition is applied to the metal foil, it may be applied in one layer, but it is preferable to apply it in two or more layers. When coating two or more layers, the first layer may contain 10 to 50 parts by weight of an acicular inorganic filler and 1 to 5 parts by weight of a curing catalyst with respect to 100 parts by weight of a benzocyclobutene resin. Preferably, the second layer contains 10 to 50 parts by weight of an acicular inorganic filler and 0.1 to 50 parts by weight of a curing catalyst with respect to 100 parts by weight of a benzocyclobutene resin.
It is preferable to add 1 part by weight. As a result, it is possible to control the variation in the thickness of the insulating resin layer after forming the multilayer printed wiring. When the above-mentioned resin composition is applied to the metal foil, it is usually performed in the form of varnish. This allows
The coatability can be improved. The solvent used for preparing the varnish preferably has good solubility in the resin composition, but a poor solvent may be used as long as it does not adversely affect the resin composition. As a good solvent, toluene,
Examples thereof include xylene, mesitylene, cyclohexanone and the like. When preparing a varnish, the solid content of the resin composition is not particularly limited, but is preferably 20 to 90% by weight,
In particular, 30 to 70% by weight is preferable. Examples of the metal forming the metal foil include copper or a copper-based alloy, aluminum or an aluminum-based alloy, and the like.

Further, the above-mentioned varnish is coated on a metal foil and
A resin-coated metal foil can be obtained by drying at 0 ° C. or higher and 200 ° C. or lower. Resin thickness after coating and drying is 1
0 to 100 μm is preferable, and 20 to 80 μm is particularly preferable. As a result, the resin layer is not cracked, and the powder drop during cutting can be reduced.

Next, the multilayer printed wiring board will be described. The multilayer printed circuit board of the present invention is a multilayer printed circuit board obtained by superposing the above-mentioned metal foil with resin on one side or both sides of the inner layer circuit board and heating and pressing. The above-mentioned metal foil with resin is laminated on one side or both sides of the inner layer circuit board and heated and pressed to obtain a laminated board. The heating temperature is not particularly limited, but 140 to 240 ° C. is preferable. The pressure to be applied is not particularly limited, but is preferably 10 to 40 kg / cm ² . Further, the inner layer circuit board may be, for example, one in which circuits are formed on both surfaces of a copper clad laminate and blackened.

[0018]

EXAMPLES The present invention will be described in detail below with reference to Examples and Comparative Examples, but the present invention is not limited thereto.

Example 1 Preparation of Varnish A As a benzocyclobutene resin, divinylsiloxane-
80 parts by weight of bisbenzocyclobutene (B-staged, number average molecular weight 140000, cycloten XUR manufactured by Dow Chemical Co., Ltd.), as an acicular inorganic filler, Arbolex (product number Y manufactured by Shikoku Chemicals, fiber diameter 0) .5-
1.0 μm, fiber length 10 to 30 μm, maximum fiber length 50 μ
m) 20 parts by weight, and 3 parts by weight of 1,2-bis (azidobenzyl) ethylene as a curing agent were dissolved in mesitylene and adjusted to a nonvolatile concentration of 50% by weight to obtain a varnish A.

Preparation of Varnish B As a benzocyclobutene resin, divinylsiloxane-
80 parts by weight of bisbenzocyclobutene (B-staged, number average molecular weight 140000, cycloten XUR manufactured by Dow Chemical Co., Ltd.), as an acicular inorganic filler, Arbolex (product number Y manufactured by Shikoku Chemicals, fiber diameter 0) .5-
1.0 μm, fiber length 10 to 30 μm, maximum fiber length 50 μ
m) 20 parts by weight, and 0.5 parts by weight of 1,2-bis (azidobenzyl) ethylene as a curing agent were dissolved in mesitylene to adjust the nonvolatile concentration to 50% by weight to obtain a varnish B.

Coating on Copper Foil As the first insulating layer, the above-mentioned varnish A was copper foil (thickness 0.018 mm, manufactured by Furukawa Circuit Foil Co., Ltd.).
Then, it was applied with a thickness of 0.14 mm and dried in a dryer oven at 150 ° C. for 10 minutes and in a dryer oven at 170 ° C. for 10 minutes. Next, as the second insulating layer, the above-mentioned varnish B was applied on the above-mentioned varnish-coated surface with a thickness of 0.14 mm, followed by 10 minutes in a dryer oven at 150 ° C and 10 minutes in a dryer oven at 170 ° C. Dried.

Manufacture of Multilayer Printed Wiring Board A copper foil surface of a double-sided copper-clad laminate is blackened (forms copper oxide) and then reduced, and the reduced resin is used as a core. A multi-layer printed wiring board was manufactured by heating and pressure bonding at 200 ° C. for 2 hours.

(Example 2) The blending amount of the benzocyclobutene resin and the needle-shaped inorganic filler was set to 70% by weight of the benzocyclobutene resin.
The same procedure as in Example 1 was performed except that the amount of the inorganic filler was 30 parts by weight.

(Example 3) The blending amount of the benzocyclobutene resin and the acicular inorganic filler was 60% by weight of the benzocyclobutene resin 60.
The same procedure as in Example 1 was performed except that the amount of the inorganic filler was 40 parts by weight.

Example 4 Example 1 was repeated except that aluminum borate whiskers A (fiber diameter: about 0.3 μm, fiber length: about 0.5 μm) were used as the acicular inorganic filler.
Same as.

Example 5 Example 1 was repeated except that aluminum borate whiskers B (fiber diameter of about 0.5 μm, fiber length of about 2.0 μm) were used as the acicular inorganic filler.
Same as.

Example 6 The same as Example 1 except that aluminum borate whiskers C (fiber diameter 0.5 μm, fiber length 0.5 to 1.0 μm) were used as the needle-shaped inorganic filler. I chose

Example 7 As a needle-shaped inorganic filler, aluminum borate whiskers D (fiber diameter 0.5 to 1.0)
.mu.m, fiber length of about 50 .mu.m)
Same as.

(Comparative Example 1) Alumina, which is a spherical inorganic filler instead of the needle-shaped inorganic filler (Product No. UE, manufactured by Showa Denko KK)
Same as Example 1 except that -3083) was used.

Comparative Example 2 An epoxy resin (manufactured by Dainippon Ink and Co., product number N-69) was used instead of the benzocyclobutene resin.
Same as Example 1 except that 0) was used.

The dielectric properties, crack resistance and moldability of the resulting multilayer printed wiring board were measured. The results obtained are shown in Table 1. Each property was measured by the following method. The dielectric constant was measured in the A state by the void measurement method.

The crack resistance is evaluated by the liquid phase cold heat test (-65
C. and 125.degree. C./100 cycles). The presence or absence of cracks was visually determined. Each symbol indicates the following items. ⊚ does not generate any cracks. ○: Some cracks are generated, but there is no problem in practical use. Δ indicates that some cracks have occurred and is practically unusable. × indicates cracking.

The formability was evaluated by the presence or absence of voids after the multilayer printed wiring board was prepared. The presence or absence of voids was visually determined. Each symbol represents the following items.
◎ indicates that no void was generated. ○: Some voids are generated, but there is no practical problem. △ indicates that voids are partially generated and cannot be practically used. × indicates the occurrence of voids.

Regarding the thickness accuracy, the cross section of the multilayer printed wiring board was observed with an optical microscope. Each symbol indicates the following items.
◎ means that there is no variation in thickness. × indicates that thickness variation occurred.

For insulation reliability, the presence or absence of disconnection was evaluated after 1000 hours of treatment in an atmosphere of 85 ° C./85% RH. Each symbol indicates the following items. ∘ means no continuity occurs.
○ indicates that there is some conduction, but there is no practical problem. △ indicates that some conduction occurs and is not practically usable. X indicates continuity has occurred.

[0036]

[Table 1]

As is apparent from the table, Examples 1 to 7 are
It was excellent in dielectric constant, crack resistance and moldability. In addition, Examples 1 and 2 are particularly excellent in dielectric constant, crack resistance,
It had an excellent balance of thickness accuracy, formability, and insulation reliability.

According to the present invention, it is possible to provide a resin composition, a metal foil with a resin and a multilayer printed wiring board which are excellent in dielectric properties and crack resistance. When the benzocyclobutene resin has a specific content, crack resistance and moldability can be particularly improved. Also,
When a needle-shaped inorganic filler having a specific shape is used, the linear expansion of the resin composition can be particularly reduced.

Continued front page    F term (reference) 4F100 AA00B AA00C AA01B AA01C                       AA12B AA12C AA18B AA18C                       AA19B AA19C AB01A AB17                       AB33A AD05B AD05C AK02B                       AK02C BA02 BA03 BA04                       BA05 BA07 BA10A BA10C                       BA13 CA02 CA23B CA23C                       DE03B DE03C DG01B DG01C                       EH46B EH46C GB43 JG04                       JG04B JG04C JG05 JK14                       YY00B YY00C                 4J002 CE001 DE076 DE146 DJ006                       DK006 FA076 FD016 GF00                       GQ00 GQ01                 5E346 AA05 AA06 AA12 AA15 AA32                       BB01 CC08 CC16 CC31 DD02                       DD03 DD32 EE02 EE06 EE07                       GG27 GG28 HH11

Claims (11)

[Claims] 1. A resin composition constituting an insulating layer of a resin-coated metal foil, comprising a benzocyclobutene resin and an acicular inorganic filler. 2. The resin composition according to claim 1, wherein the benzocyclobutene resin is represented by the following formula. [Chemical 1] 3. The content of the benzocyclobutene resin is 40 to 95% by weight of the total resin composition.
Or the resin composition according to 2. 4. The inorganic filler has an average fiber diameter of 0.3.
The resin composition according to any one of claims 1 to 3, wherein the resin composition has a thickness of ˜2.0 μm. 5. The average fiber length of the inorganic filler is 0.5.
The resin composition according to any one of claims 1 to 4, which has a thickness of -50 μm. 6. The inorganic filler is one or more needle-like inorganic fillers selected from aluminum borate, magnesia, alumina, and silicon nitride.
The resin composition according to any one of 1. 7. The maximum fiber length of the inorganic filler is 10 to 10.
The resin composition according to claim 1, which has a thickness of 50 μm. 8. The resin composition according to claim 1, wherein the content of the inorganic filler is 5 to 60% by weight of the whole resin composition. 9. A resin-coated metal foil, which is obtained by applying the resin composition according to claim 1 to a metal foil. 10. A metal foil with a resin, which is obtained by laminating two or more layers of the resin composition according to any one of claims 1 to 8. 11. A multilayer printed circuit board, comprising the resin-coated metal foil according to claim 9 or 10 superposed on one side or both sides of an inner layer circuit board and heated and pressed.