JP2003181979A - Metal foil with resin and multilayer printed circuit board - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a metal foil with a resin and a printed wiring board which are excellent in dielectric properties and resistance to cracking. <P>SOLUTION: The metal foil with the resin has a resin layer containing a benzocyclobutene resin and a thermoplastic elastomer. As for the thermoplastic elastomer, a specified styrene-butadiene copolymer is used preferably particularly. The present multilayer printed circuit board is formed by laying the metal foil with the resin on one or both surfaces of an inner-layer circuit board and by applying heat and pressure thereto. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to 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-coated metal foil excellent in dielectric characteristics and crack resistance and a multilayer printed circuit board.

[0006]

These objects are achieved by the present invention described in (1) to (7) below. (1) A resin-coated metal foil having a resin layer containing a benzocyclobutene resin and a thermoplastic elastomer. (2) A resin layer having a first layer containing a benzocyclobutene resin and a second layer containing the benzocyclobutene resin, wherein at least one layer of the first layer and the second layer contains a thermoplastic elastomer. A resin-coated metal foil having a resin layer. (3) The resin-coated metal foil according to (1) or (2), wherein the benzocyclobutene resin is represented by the formula (I).

[Chemical 2] (4) The resin-coated metal foil according to any one of (1) to (3), wherein the thermoplastic elastomer is a styrene-polybutadiene copolymer. (5) The number average molecular weight of the thermoplastic elastomer is 1
The resin-coated metal foil according to any one of the above (1) to (4), which is 50,000 to 150,000. (6) The resin-coated metal foil according to any one of (1) to (5), wherein the content of the thermoplastic elastomer is 0.1 to 20 parts by weight with respect to 100 parts by weight of the benzocyclobutene resin. (7) A multilayer printed circuit board comprising the resin-coated metal foil according to any one of (1) to (6) above, which is superposed on one side or both sides of an inner layer circuit board and heated and pressed.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION The metal foil with resin and the multilayer printed circuit board of the present invention will be described in detail. The resin-coated metal foil of the present invention is characterized by having a resin layer containing a benzocyclobutene resin and a thermoplastic elastomer. The multilayer printed circuit board of the present invention is characterized in that the above-mentioned resin-coated metal foil is laminated on one side or both sides of the inner layer circuit board and heated and pressed.

First, the resin-coated metal foil of the present invention will be described. The metal foil with resin of the present invention has a resin layer containing a benzocyclobutene resin and a thermoplastic elastomer. As a result, the dielectric properties are excellent and the crack resistance can be improved. 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 the benzocyclobutene resin represented by the formula (I). 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.

The B-staged benzocyclobutene resin is also preferably used for adjusting the moldability and is included in the benzocyclobutene resin of the present invention. B stage conversion is performed by heating and melting. The B-staged benzocyclobutene resin has a number average molecular weight of 500 or more.

Further, a B-staged benzocyclobutene resin having the above formula (I) 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 1,000,000. The number average molecular weight can be measured using, for example, gel permeation chromatography (GPC).

In the present invention, the above-mentioned benzocyclobutene resin alone may be used as the resin component, and other resins may be blended. In this case, the content of the benzocyclobutene resin is not particularly limited, but is preferably 20 parts by weight to 95 parts by weight, and particularly preferably 30 to 8 parts by weight in 100 parts by weight of the resin component (benzocyclobutene resin and other resins).
0 parts by weight is preferred. If the content of the benzocyclobutene resin is less than the lower limit value, the effect of improving the dielectric properties may be reduced, and if it exceeds the upper limit value, the fluidity of the resin may be reduced.

The resin-coated metal foil of the present invention contains a thermoplastic elastomer. Thereby, the crack resistance of the benzocyclobutene resin can be improved. This is because the thermoplastic elastomer is excellent in rubber elasticity because it contains the diene site of the soft segment. Examples of the thermoplastic elastomer include polystyrene-based thermoplastic elastomers such as styrene-butadiene copolymers and styrene-isoprene copolymers, polyolefin-based thermoplastic elastomers, polyamide-based elastomers and polyester-based elastomers. Among these, a styrene-butadiene copolymer is preferable, and a thermoplastic elastomer represented by the formula (II) is particularly preferable.

[Chemical 4] This is because these thermoplastic elastomers have excellent compatibility with the benzocyclobutene resin. When the compatibility between the benzocyclobutene resin and the thermoplastic elastomer is excellent,
In addition to the effect of improving the crack resistance, the adhesion with the metal foil can be improved. The thermoplastic elastomer represented by the formula (II) has excellent rubber elasticity because it contains a diene site of a soft segment, and when it contains an epoxy group, it can have particularly high adhesion to a metal foil. Furthermore, since it has a chemical structure with few polar groups in the skeleton, it has a small dipole moment and does not deteriorate the dielectric properties. Therefore,
By using the thermoplastic elastomer represented by the formula (II) in combination with the benzocyclobutene resin, a resin composition having excellent properties such as dielectric properties, crack resistance, and adhesion to metal foil can be obtained.

The number average molecular weight of the thermoplastic elastomer is not particularly limited, but is 10,000 to 150,000.
0 is preferable, and 50,000 to 100,000 is particularly preferable. If the number average molecular weight is less than the lower limit, the effect of improving crack resistance may be reduced, and if it exceeds the upper limit, compatibility with the benzocyclobutene resin may be reduced. The number average molecular weight is, for example, G
It can be measured using a PC.

The content of the thermoplastic elastomer is 0.1 to 2 with respect to 100 parts by weight of the benzocyclobutene resin.
0 parts by weight is preferable, and 1 to 10 parts by weight is particularly preferable.
If the content is less than the lower limit, the effect of improving the crack resistance may be reduced, and if it exceeds the upper limit, the compatibility with the benzocyclobutene resin may be reduced.

The bending elastic modulus of the thermoplastic elastomer is not particularly limited, but is preferably 100 to 600 MPa, and particularly preferably 200 to 400 MPa. When the flexural modulus is within the above range, the metal foil with resin and the multilayer printed circuit board can have particularly excellent crack resistance.

The metal foil with resin of the present invention is not particularly limited, but is a resin layer having a first layer containing a benzocyclobutene resin and a second layer containing a benzocyclobutene resin, wherein the first layer Alternatively, at least one of the second layers preferably has a resin layer containing a thermoplastic elastomer. Thereby, in addition to the above-mentioned excellent dielectric properties and crack resistance, the moldability (in particular, the thickness of the resin layer can be made more uniform) can be improved. This is because if the thickness of the resin layer can be made more uniform, the dielectric characteristics can be further improved. The thermoplastic elastomer may be contained in at least one of the first layer and the second layer, but is preferably contained in both layers. Thereby, crack resistance can be further improved.

The first layer is preferably formed on the metal foil surface, and the second layer is preferably formed on the first layer. Different resin components may be used for the first layer and the second layer, but it is preferable to use the same resin component. Thereby, the characteristics of the product can be made more uniform. The reaction rate of the first layer is not particularly limited, but is preferably higher than the reaction rate of the second layer. Thereby, the moldability of the resin-coated metal foil can be particularly improved. The reaction rate can be determined by, for example, a differential scanning calorimeter (DSC).

The thickness of the first layer is not particularly limited, but is preferably 10 to 100 mm, particularly preferably 20 to 80 mm. When the thickness is within the above range, cracking of the resin layer can be prevented especially when the metal foil is coated and dried and wound on a roll. The thickness of the second layer is not particularly limited, but is preferably 10 to 100 mm, particularly 20 to 80 mm.
Is preferred. When the thickness is within the above range, cracking of the resin layer can be prevented especially when the metal foil is coated and dried and wound on a roll.

The layer containing the benzocyclobutene resin and the layer containing the benzocyclobutene resin and the thermoplastic elastomer of the present invention are, within a range not deviating from the object of the present invention, a curing accelerator, a coupling agent, a flame retardant and a filler. , Other ingredients may be added.

The layer containing the benzocyclobutene resin and the thermoplastic elastomer can be obtained by various methods. Usually, it is preferable to use each resin and additives in the form of a varnish having a film-forming property. It is preferable in terms. It is desirable that the solvent used has good solubility in the composition, but a poor solvent may be used as long as it does not adversely affect the composition. Examples of the good solvent include toluene, xylene, mesitylene, cyclohexanone and the like. In addition, when the varnish is prepared, the solid content of the resin composition is not particularly limited, but is preferably 20 to 90% by weight, and particularly preferably 30 to 70% by weight. Examples of the metal forming the metal foil include copper or a copper-based alloy, aluminum or an aluminum-based alloy, and the like. In addition, when it has the said 1st layer and a 2nd layer,
Each of the first layer and the second layer can be obtained by the same method as described above.

In the present invention, a resin varnish obtained by dissolving the above-mentioned resin or the like in a solvent is coated on a metal foil, and for example 80
A metal foil with a resin can be obtained by drying at ~ 200 ° C. Further, the first layer and the second layer can be formed by repeating the above-mentioned operations a plurality of times. The resin thickness after coating and drying is preferably 10 to 100 μm, and particularly preferably 20 to 80 μm. As a result, the resin layer is not cracked, and the powder drop during cutting can be reduced.

Next, the multilayer printed circuit 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.

[0023]

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 resin varnish As a benzocyclobutene resin, divinylsiloxane-
100 parts by weight of bisbenzocyclobutene (prepolymerized, number average molecular weight 140,000, cycloten XUR manufactured by Dow Chemical Co., Ltd.), epoxidized SBR resin (number average molecular weight 100000, manufactured by Daicel Chemical Industries, Ltd.) as a thermoplastic elastomer. Friend A1005) 10
Part by weight is dissolved in mesitylene to have a nonvolatile content of 50% by weight
A resin varnish was prepared so that

Production of Metal Foil with Resin Using a varnish prepared by dissolving 3 parts by weight of 1,2-bis (azidobenzyl) ethylene as a partial crosslinking agent in the above resin varnish, a copper foil (thickness 0.018 mm, Furukawa Circuit Foil Co., Ltd.) resin varnish thickness of 0.07m
m, and dried in a dryer oven at 150 ° C. for 10 minutes and in a dryer oven at 170 ° C. for 10 minutes to form a first resin layer,
Subsequently, using a varnish prepared by dissolving 0.5 part by weight of 1,2-bis (azidobenzyl) ethylene in the above resin varnish, copper foil (thickness 0.018 mm, manufactured by Furukawa Circuit Foil Co., Ltd.) was prepared. Resin varnish thickness 0.07mm
And the resin thickness is 0.07mm by drying in a dryer oven at 150 ° C for 10 minutes and then in a dryer oven at 170 ° C for 10 minutes.
A metal foil with resin was prepared.

Manufacture of multilayer printed circuit board The copper foil surface of a double-sided copper-clad laminate having copper foil stretched on both sides is blackened (forms copper oxide) and then reduced to form a core, which is coated with the above-mentioned resin on both sides. Metal foil at 170 ℃ for 1 hour, 2
A multilayer printed circuit board was manufactured by bonding under heat and pressure at 00 ° C. for 2 hours, thermosetting and etching the surface copper foil.

Example 2 The procedure of Example 1 was repeated, except that the amount of the thermoplastic elastomer added was 5 parts by weight.

Example 3 The same as Example 1 except that the addition amount of the thermoplastic elastomer was 12 parts by weight.

Example 4 The procedure of Example 1 was repeated except that the amount of thermoplastic elastomer added was 0.5 parts by weight.

Example 5 Polybutadiene (product number B-300 manufactured by Nippon Petrochemical Co., Ltd. as a thermoplastic elastomer
Same as Example 1 except that 0) was used.

(Example 6) In the manufacture of a metal foil with a resin, the same procedure as in Example 1 was carried out except that the resin layer was applied as a single layer as follows. Using a resin varnish prepared by dissolving 3 parts by weight of 1,2-bis (azidobenzyl) ethylene as a partial cross-linking agent in the resin varnish of the first layer, a copper foil (thickness 0.018 mm, Furukawa circuit foil ( stock)
Resin varnish with a thickness of 0.140 mm.
It was dried in a dryer oven at 0 ° C. for 10 minutes and in a dryer oven at 170 ° C. for 10 minutes to prepare a resin-coated metal foil having a resin thickness of 0.070 mm.

(Comparative Example 1) The procedure of Example 1 was repeated except that the thermoplastic elastomer was not added.

The multilayer printed circuit boards obtained in the examples and comparative examples were evaluated as follows. The method of each evaluation is also shown. The results obtained are shown in Table 1. Dielectric constant Dielectric constant was measured in the A state by the void measurement method.

Crack resistance The crack resistance was evaluated by a liquid phase cold heat test (treatment at -65 ° C. and 125 ° C. for 30 minutes / 300 cycles). The measurement is
Tabai Espec liquid bath thermal shock device TSB-2 type, Fluorinert liquid was used. The presence or absence of cracks was visually determined. Each symbol indicates the following items. A: No cracks occurred at all. ◯: Some cracks occur, but there is no practical problem. Δ: Some cracks are generated and cannot be practically used. X: A crack is generated.

Moldability The moldability was evaluated by the presence or absence of voids after the multilayer printed circuit board was prepared. The presence or absence of voids was visually determined. Each symbol represents the following items. A: No void is generated. ◯: Some voids are generated, but there is no practical problem. Δ: Some voids are generated and cannot be used practically. X: Void is generated.

Thickness accuracy The thickness accuracy was determined by observing the cross section of the multilayer printed circuit board with an optical microscope. Each symbol indicates the following items. ⊚: Thickness variation is less than 15 μm. ◯: There is some thickness variation of 15 to 20 μm, but there is no practical problem. Δ: Some variation in thickness is 20 to 25 μm, and practically unusable. X: The variation in thickness is 25 μm or more.

Adhesion Adhesion was evaluated by copper foil peel strength. The copper foil peel strength was measured according to JIS C 6481.

Mechanical Properties Mechanical properties were measured by measuring the elastic modulus, tensile strength, and elongation of the copper foil of the multilayer printed circuit board removed by etching. Elastic modulus, tensile strength, and elongation are 20kgf full scale and 5mm / mi speed in tensile mode.
n. It was measured at.

[0038]

[Table 1]

As is apparent from the table, Examples 1 to 6 were excellent in dielectric constant and crack resistance. Further, when a resin-coated metal foil having a specific layer structure was formed, it was particularly excellent in moldability and thickness accuracy.

[0040]

According to the present invention, it is possible to obtain a resin-coated metal foil and a printed wiring board having excellent dielectric properties and excellent crack resistance. Further, when the resin-coated metal foil having a specific resin layer is used, a resin-coated metal foil and a printed wiring board having particularly excellent moldability can be obtained.

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) H05K 3/46 H05K 3/46 GT term (reference) 4F100 AB01B AB17 AK02A AK02C AK73A AK73C AL05C AL06 AL09A AL09C BA02 BA03 BA10A BA10B GB43 JA07A JA07C JB16A JB16C JG05 JK14 JL01 YY00A YY00C 4J002 BB002 BC052 CE001 CF002 CL002 4J032 CA12 CB01 CC01 CE03 CE18 CE20 CG01 CG01 CG06 CG06 5E346 AA05 AA06 AA08 DD0801

Claims (7)

[Claims] 1. A metal foil with a resin, comprising a resin layer containing a benzocyclobutene resin and a thermoplastic elastomer. 2. A resin layer having a first layer containing a benzocyclobutene resin and a second layer containing the benzocyclobutene resin, wherein at least one layer of the first layer and the second layer is a thermoplastic elastomer. A resin-containing metal foil having a resin layer containing: 3. The resin-coated metal foil according to claim 1, wherein the benzocyclobutene resin is represented by the formula (I). [Chemical 1] 4. The resin-coated metal foil according to claim 1, wherein the thermoplastic elastomer is a styrene-polybutadiene copolymer. 5. The resin-coated metal foil according to claim 1, wherein the thermoplastic elastomer has a number average molecular weight of 10,000 to 150,000. 6. The content of the thermoplastic elastomer is
0.1 to 100 parts by weight of benzocyclobutene resin
The metal foil with resin according to claim 1, which is 20 parts by weight. 7. A multilayer printed circuit board, comprising the resin-coated metal foil according to claim 1 superposed on one side or both sides of an inner layer circuit board and heated and pressed.