HK1058216B - Copper foil surface treatment agent - Google Patents

Description

Copper foil surface treating agent

Technical Field

The present invention relates to a copper foil surface treatment agent for improving adhesion between a copper foil and an insulating resin. In particular, the present invention relates to a copper foil surface treatment agent which is used for a substrate suitable for high frequency and has a smooth surface and excellent adhesion between a copper foil and an insulating resin.

Background

In recent years, with the development of high performance and high functionality of computers and information communication devices and the development of networking thereof, the operation signal tends to be high frequency for high-speed transmission and processing of large-capacity information.

However, epoxy resins having excellent adhesive properties are generally widely used as insulating materials for printed wiring boards, but epoxy resins generally have high dielectric constants and dielectric loss tangents and insufficient high-frequency properties. Therefore, in order to cope with the signal frequency increase for information communication, it is necessary to use a resin having excellent dielectric properties, but a resin having a low dielectric constant and a low dielectric loss tangent tends to have a reduced adhesive property because of a small number of highly polar functional groups contributing to adhesion, and thus, improvement is strongly required.

In addition, it is desirable that the copper foil suitable for the high-frequency substrate is subjected to surface smoothing treatment, i.e., surface roughness reduction as much as possible. The reason why the surface of the copper foil is smoothed is that the surface roughness of the copper foil has a great influence on the transmission loss, considering that a current flows concentratedly in the surface portion of the copper foil as the transmission signal becomes a high frequency (this phenomenon is called a super-skin effect).

Therefore, in the case of a substrate suitable for high frequency applications, the adhesion strength between the copper foil and the insulating resin is reduced due to both resin conversion and smoothing of the surface of the copper foil, and improvement of the adhesion is strongly required.

As a method for improving the adhesion between the copper foil suitable for the high-frequency substrate and the insulating resin, a method of treating the surface of the copper foil with a silane coupling agent or adding the resin to the copper foil is generally used. The present inventors have disclosed a silane coupling agent containing a specific organosilicon compound represented by the general formulae (1) and (2) as an active ingredient in JP-A-8-295736. In addition, commercially available epoxy-based and amino-based silane coupling agents are also effective and have been used for years. However, in recent years, in order to meet the high frequency requirement, there are increasing cases where such characteristic requirements cannot be satisfied in reality.

Disclosure of the invention

Accordingly, an object of the present invention is to provide a copper foil surface treatment agent capable of firmly bonding a copper foil used for a printed wiring board or the like and an insulating resin. In particular, a copper foil surface treatment agent which is effective for insulating resins and copper foils having a smooth surface, which are suitable for use in high-frequency substrates.

The present inventors have conducted intensive studies in order to improve the adhesion between a copper foil and an insulating resin, and as a result, have found that the above-mentioned problems can be solved by combining a specific organosilicon compound and an olefinic silane coupling agent. In particular, it has been found that an aqueous solution containing an organosilicon compound represented by the general formula (1) and/or the general formula (2) below and an olefin silane coupling agent as active ingredients can be used as a surface treatment agent for copper foil suitable for high-frequency substrates, and the adhesion strength between an insulating substrate and copper foil can be greatly improved. That is, the present invention provides the following copper foil surface treatment agents [1] to [4] and copper foils.

[1] A copper foil surface treating agent comprising an olefin-based silane coupling agent and an organosilicon compound represented by the following general formula (1) and/or an organosilicon compound represented by the following general formula (2) as active ingredients,

(in the above general formulae (1) and (2), R¹Represents a hydroxyl group or an alkyl group having 1 to 5 carbon atoms, R²Represents an alkylene group having 1 to 10 carbon atoms which may contain oxygen, X is:

or

A former group having two hydroxyl groups generated by cleavage of an epoxy group, n represents an integer of 2 or more; m represents an integer of 1 or more).

[2] A copper foil surface treatment agent comprising a solution as an active ingredient, wherein the solution is obtained by stirring an organosilicon compound having an epoxy group represented by the following general formula (3) in an aqueous solution under heating, cooling the solution to room temperature, adding an olefinic silane coupling agent, and stirring the mixture.

(in the general formula (3), R³Represents an alkyl group having 1 to 5 carbon atoms, R⁴R represents any one of a hydroxyl group and an alkyl group having 1 to 5 carbon atoms⁵Represents a single bond or an alkylene group having 1 to 10 carbon atoms and containing oxygen, and L represents 2 or 3. )

[3] A copper foil surface-treated with the copper foil surface-treating agent according to [1] or [2 ].

[4] The copper foil according to [3], characterized in that the surface roughness (Rz) is 3.5 μm or less, and the surface is smooth.

The mechanism by which the surface treatment agent of the present invention can improve the adhesion between the copper foil and the insulating resin can be considered as follows. First, since the organosilicon compound represented by the general formula (1) and/or the general formula (2) is an oligomer component, it is easily adhered to a copper foil. Next, it is presumed that the olefinic silane coupling agent reacts with the insulating resin and also with the organosilicon compound represented by the general formula (1) and/or the general formula (2), and therefore, the adhesiveness between the copper foil and the insulating resin can be improved.

The use of the organosilicon compound represented by the general formula (1) and/or the general formula (2) alone or the use of the olefinic silane coupling agent alone does not sufficiently improve the adhesive strength between the copper foil and the insulating resin. According to the studies of the present inventors, it was confirmed that particularly good adhesive strength can be obtained by combining both (the general formula (1) and/or the general formula (2) with the olefinic silane coupling agent).

The structure of the present invention will be explained below.

The surface treatment agent of the present invention is a treatment agent containing an organosilicon compound represented by the general formula (1) and/or the general formula (2), and may contain an intermolecular condensation product of the compound, which is a condensation reaction between-Si-OH groups. In the general formulae (1) and (2), n is 2 or more, preferably 2 to 50, and m is 1 or more, preferably 1 to 50. In particular, when m is 2, the stability is the most stable.

The organosilicon compound represented by the general formula (1) or (2) can be obtained by heating and stirring the compound represented by the general formula (3), as described below. In the general formula (3), R³Represents an alkyl group having 1 to 5 carbon atoms, but an alkyl group having 1 or 2 carbon atoms is more preferable because it is easily decomposed by water. R⁴The carbon number is suitably 1 or 2 in view of solubility in water. When L is 2 or 3, the alkoxysilyl group is hydrolyzed and condensed, whereby the effects of the present invention can be sufficiently exhibited. However, since the larger the number of alkoxysilyl groups, the more hydrolysis and condensation occur and the reactivity with other silane coupling agents or copper foils can be improved, the larger the value of n in the general formula (1), the better, and L is particularly preferably 3. R⁵The effect of the present invention can be sufficiently exhibited when the carbon number is a single bond or an alkylene group having 1 to 10 carbon atoms, but the alkylene group having 1 to 5 carbon atoms is more preferable because the hydrophobicity becomes stronger as the carbon number increases and the solubility in water decreases. In addition, R⁵The alkylene group may contain an ether bond. Examples of the organosilicon compound having an epoxy group include the following organosilicon compounds.

The organosilicon compound represented by the general formula (1) and/or (2) can be obtained by stirring the organosilicon compound having an epoxy group represented by the general formula (3) in an aqueous solution under heating. In this case, the organosilicon compound having an epoxy group used in the present invention and represented by the general formula (3) is stirred in an aqueous solution at 40 to 90 ℃. Then, according to the results of NMR measurement, it was confirmed that epoxy groups shown in the following reaction formula (4) were partially cleaved to generate hydroxyl groups.

Further, from the results of the liquid chromatography measurement, it was confirmed that a trialkoxysilyl group was hydrolyzed and then condensed to form a siloxane oligomer as shown in the following reaction formula (5). That is, it is found that the organosilicon compound represented by the general formula (1) and the compound represented by the general formula (2) are produced as a mixture thereof.

When the surface treatment agent of the present invention is used for a copper foil, it is considered that the hydroxyl groups generated as described above are hydrogen-bonded to the resin or the copper foil, and further, evaporation due to heat treatment after the surface treatment is suppressed by the siloxane oligomer, so that the amount of coating on the copper foil is increased, and the adhesion between the copper foil and the resin can be improved. The organosilicon compound represented by the general formula (1) and the organosilicon compound represented by the general formula (2) are heated and stirred to form a mixture, and the mixture is used as it is as an active ingredient of the surface treatment agent of the present invention without particular separation and purification.

For the above-mentioned reaction of forming the hydroxyl group and the siloxane oligomer, the heating temperature is preferably 40 to 90 ℃ as described above. If the temperature is less than 40 ℃, the reaction is retarded, and if the temperature exceeds 90 ℃, the hydrolysis and condensation reactions of trialkoxysilyl groups excessively proceed, leading to gelation. In view of these circumstances, a more preferable stirring temperature is 60 to 85 ℃. In order to control the amount of hydroxyl groups and siloxane oligomers produced, an acid such as acetic acid or hydrochloric acid, or an alkali solution such as ammonia may be added. The aqueous solution is stirred for a long time to react, thereby improving the binding property, but the effect of the present invention can be sufficiently exhibited if the aqueous solution is stirred for two hours or more.

The olefinic silane coupling agent used in the present invention includes vinyl silane, acrylic silane, and methacrylic silane.

Among the vinyl silanes, there are vinyltrichlorosilane, vinyltrialkoxysilane, vinyldialkoxyalkylsilane, and the like, for example: vinyltrimethoxysilane, vinyltriethoxysilane, vinyltris (. beta. -methoxyethoxy) silane, vinyldimethoxymethylsilane, vinyldiethoxymethylsilane, etc. Examples of the acrylic silane include gamma-acryloxypropyltrimethoxysilane. Examples of methacrylic silanes include: gamma-methacryloxypropyltrimethoxysilane, gamma-methacryloxypropylmethyldimethoxysilane, gamma-methacryloxypropylmethyldiethoxysilane, gamma-methacryloxypropyltriethoxysilane, and the like. Among them, vinyl silanes, particularly vinyltrimethoxysilane and vinyltriethoxysilane, are more preferable.

In the surface treatment agent of the present invention, the mixing ratio (weight ratio) of the organosilicon compound represented by the general formula (1) and/or (2) and the olefinic silane coupling agent may be in the range of 99: 1 to 1: 99, but is more preferably 5: 95 to 70: 30.

The surface treatment agent of the present invention is used by diluting the total amount of the active ingredients, that is, the organosilicon compound represented by the general formula (1) and/or the general formula (2) and the olefinic silane coupling agent, with water or an aqueous solution containing acetic acid or the like for weak acidity, in an amount of 0.01 to 10% by weight, preferably 0.01 to 6% by weight. When the surface treatment is performed on the copper foil, a method of immersing the copper foil in the solution, a method of spraying the solution on the surface of the copper foil, and the like can be employed, and a method of coating the surface of the copper foil is convenient and preferred. After coating on the copper foil, the effect of the present invention can be sufficiently exhibited if water is evaporated, and the reaction between the silane coupling agent and the copper foil can be suitably promoted if the coating is dried at 50 to 180 ℃.

The surface treatment agent of the present invention may be appropriately added with other additives such as a silane coupling agent, a pH adjuster, and a buffer, as needed.

The copper foil applicable to the surface treatment agent of the present invention is not particularly limited, and any of electrolytic foil and rolled foil can be used. Further, depending on the application, roughening treatment and rust prevention treatment may be performed. The roughening treatment is a step of precipitating fine copper particles. However, for a high-frequency substrate, a copper foil having as small a surface roughness as possible is preferable, and therefore, roughening treatment may not be performed. The substrate suitable for high frequency signals may be a copper foil having a surface roughness (Rz) of 3.5 μm or less, more preferably 3 μm or less. Therefore, it is important to maintain the balance between waviness and coarsened particles on the surface of the copper foil. The surface roughness in the present specification means a surface roughness Rz specified in JIS B0601. For the rust-proofing treatment of the copper foil, inorganic rust-proofing treatment such as zinc, zinc alloy, chromate, or the like can be used. The zinc alloy is preferably an alloy of zinc and a metal such as nickel, cobalt, copper or chromium, or a mixed system of these metals.

The insulating resin used together with the copper foil treated with the surface treatment agent of the present invention can sufficiently exhibit the effects of the present invention as long as it is a high-frequency-applicable insulating resin capable of double-bond curing or a double-bond-curable insulating resin, but particularly, an insulating resin which is required to be improved in peel strength as much as high-frequency application is desired is preferable.

Examples of the insulating resin having double bonds as a curing action include thermosetting polyphenylene ether resins, thermosetting polyphenylene ether resins containing a polystyrene-based polymer, and resin compositions containing triallyl cyanurate polymer or copolymer. Methacrylic acid or acrylic acid modified epoxy resin composition, butadiene polymer added with phenol, diallyl phthalate resin, divinylbenzene resin, polyfunctional methacryl resin, unsaturated polyester resin, polybutadiene resin, styrene-butadiene. Crosslinked polymers of styrene-butadiene and the like. The resin is not limited to a single compound, and various other substances may be added and denatured to obtain desired properties. The thermosetting resin may be blended with a thermoplastic resin. Further, a filler or an additive may be added to the thermosetting resin.

Best mode for carrying out the invention

The present invention will be described in detail with reference to examples and comparative examples. However, the present invention is not limited to these examples. The following% all mean weight%.

Synthesis of epoxy silane by high-temperature stirring

First, a method for producing an epoxysilane by stirring at a high temperature will be described as the organosilicon compound represented by the general formula (1) and/or the general formula (2) of the present invention. In the examples below, this high temperature was used to stir the epoxy silane. First, gamma-glycidoxypropyltrimethoxysilane was added at 4% to pure water adjusted to pH 5 with acetic acid. The solution was stirred for 24 hours while maintaining the solution at 85 ℃. By passing¹³C-NMR、²⁹Si-NMR and aqueous GPC measurements confirmed that the epoxy ring was completely opened and that the trimethoxysilyl group of gamma-glycidoxypropyltrimethoxysilane was hydrolyzed and condensed to form a siloxane oligomer. That is, from these analysis results, the fact that: the reaction product obtained by stirring the aqueous solution of gamma-glycidoxypropyltrimethoxysilane with heating is an organosilicon compound represented by the general formula (1) or an organosilicon compound represented by the general formula (2) which is itself condensed and cyclized.

Surface treatment of copper foil

An electrolytic copper foil having a thickness of 18 μm was prepared, and the rough surface thereof was roughened to form a brass layer. The copper foil is then electroplated with a zinc-chromium-based mixture of zinc or zinc oxide and chromium oxide coating. The surface roughness (Rz) of the plating-coated surface is 3.0 to 3.5 μm. The copper foil coated by plating was subjected to the following surface treatment using the surface treatment agents (i) to (iv) used in the following examples 1 to 2 and comparative examples 1 to 2, respectively. The surface treatment method was carried out by dropping a small amount of the surface treatment agent on a copper foil, and applying the surface treatment agent on the copper foil by rotating a SUS roll. After coating, the copper foil was dried at 100 ℃ for 5 minutes.

Example 1

In example 1, the copper foil was subjected to surface treatment using the following surface treatment agent (i) in accordance with the above-described "surface treatment of copper foil".

First, a solution prepared by adding acetic acid to pure water to adjust the pH to 5, diluting 4% of the high-temperature-stirring epoxysilane synthesized in the above-mentioned "synthesis of high-temperature-stirring epoxysilane" by 40 times, adding 0.3% of vinyltriethoxysilane, and stirring for 12 hours was used. (0.1% high temperature stirring epoxy silane/0.3% vinyl triethoxysilane)

Adhesion test

The copper-clad laminate is produced by heating and pressing the copper foil subjected to the surface treatment and the glass fiber substrate impregnated with polyphenylene ether as a main component. The peel strength in normal state of the copper-clad laminate was measured according to the method prescribed in JIS C6481. The results are shown in table 1 below.

Example 2

In example 2, a copper foil was surface-treated in the same manner as in example 1 except that the following surface treating agent (c) was used. Then, the same adhesion test as in example 1 was performed using this copper foil. The evaluation results are shown in table 1 below.

② a solution obtained by adding acetic acid to pure water to adjust the pH to 5, diluting 4% of the high-temperature stirring epoxysilane synthesized according to the above-mentioned "synthesis of high-temperature stirring epoxysilane" by 20 times, adding 0.2% of vinyltriethoxysilane, and stirring for 12 hours. (0.2% high temperature stirring epoxy silane/0.2% vinyl triethoxysilane)

Comparative example 1

In comparative example 1, a copper foil was surface-treated in the same manner as in example 1, except that the following surface treatment agent (c) was used. Then, the same adhesion test as in example 1 was performed using this copper foil. The evaluation results are shown in table 1 below.

③ adding acetic acid and liquid with pH value adjusted to 5 into pure water, and stirring the epoxy silane solution with the concentration of 4 percent at high temperature to dilute the epoxy silane solution by 10 times. (0.4% high temperature stirring epoxy silane)

Comparative example 2

In comparative example 2, a copper foil was surface-treated in the same manner as in example 1, except that the following surface treatment agent (r) was used. Then, the same adhesion test as in example 1 was performed using this copper foil. The evaluation results are shown in table 1 below.

And fourthly, adding 0.4 percent of vinyltriethoxysilane into the liquid which is added into the pure water and is adjusted to pH 5 by acetic acid, and then stirring the solution for 12 hours. (0.4% of vinyltriethoxysilane)

TABLE 1

	Surface treating agent	Normal peeling (Kg/cm)
			Example 1	0.1% high temperature stirring epoxy silane/0.3% vinyl triethoxysilane	0.73
Example 2	0.2% high temperature stirring epoxy silane/0.2% vinyl triethoxysilane	0.65
			Comparative example 1	0.4% high temperature stirring epoxy silane	0.21
Comparative example 2	0.4% vinyltriethoxysilane	0.50

From table 1, it was confirmed that examples 1 and 2 using the mixed surface treatment agent of epoxysilane and vinylsilane stirred at a high temperature exhibited significantly higher peel strength than comparative examples 1 and 2 using the silane-based surface treatment agent alone, respectively.

Industrial applicability

The surface treatment agent of the present invention can provide excellent adhesion between an insulating resin and a copper foil. In particular, when the surface treatment agent of the present invention is used for a copper foil having a smooth surface suitable for a high-frequency substrate, excellent adhesion to an insulating resin, which has not been obtained with the conventional treatment agent, can be achieved.

Claims (3)

1. A copper foil surface treating agent comprising a vinyl silane coupling agent and an organosilicon compound represented by the following general formula (1) and/or an organosilicon compound represented by the following general formula (2) as active ingredients,

wherein, in the above general formulae (1) and (2), R¹Represents a hydroxyl group or an alkyl group having 1 to 5 carbon atoms, R²Represents an alkylene group having 1 to 10 carbon atoms which may contain oxygen, X is:

or

A former group having two hydroxyl groups generated by cleavage of an epoxy group, n represents an integer of 2 or more; m represents an integer of 1 or more,

the copper foil surface treatment agent is used for a copper foil suitable for smoothing the surface of a high-frequency substrate, and the surface roughness Rz of the copper foil with a smoothed surface is 3.5 [ mu ] m or less.

2. A copper foil surface treatment agent comprising a solution obtained by stirring an organosilicon compound having an epoxy group represented by the following general formula (3) in an aqueous solution under heating, cooling the solution to room temperature, adding a vinyl silane coupling agent, and stirring the mixture,

in the general formula (3), R³Represents an alkyl group having 1 to 5 carbon atoms, R⁴Represents a hydroxyl group or an alkyl group having 1 to 5 carbon atoms, R⁵Represents a single bond or an alkylene group having 1 to 10 carbon atoms and containing oxygen, L represents 2 or 3,

the copper foil surface treatment agent is used for a copper foil suitable for smoothing the surface of a high-frequency substrate, and the surface roughness Rz of the copper foil with a smoothed surface is 3.5 [ mu ] m or less.

3. A copper foil which has been surface-treated with the copper foil surface-treating agent according to claim 1 or 2.