JPH06256966A - Surface treated copper foil - Google Patents

Abstract

PURPOSE:To provide a surface treating method of a copper foil enabling to enhance adhesive strength between the copper foil and a substrate, in the case using a copper foil in a rigid copper clad lamination layer substrate in which a condensed polycyclic aromatic resin is an impregnated resin. CONSTITUTION:The copper foil is surface-treated with either an aromatic compound having at least two substituted groups selected from a hydroxymethyl group and a halomethyl group bonded to an aromatic ring or a chromate treating liquid.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a copper foil material mainly used for producing a copper clad laminated board, and more specifically to a copper foil material which has been surface-treated in order to improve adhesion with a resin.

[0002]

2. Description of the Related Art A printed wiring board used as a mounting substrate for electronic parts in various electric and electronic devices is a copper-clad substrate in which a copper foil is bonded to one or both sides of an insulating substrate, and imaging, etching, It is manufactured by giving a wiring function by subjecting it to metal plating. The copper-clad substrate is a rigid copper-clad substrate that is a rigid laminated substrate formed by laminating and molding a prepreg (reinforcing base material impregnated with resin), and a plastic film with a soft substrate. And a flexible copper-clad substrate made of, from which a rigid printed wiring board and a flexible printed wiring board are manufactured, respectively. The former can be a multilayer printed wiring board, and the latter has a feature that it can be particularly downsized.
It is used properly according to the application.

Thermosetting resins such as epoxy resins, phenolic resins and unsaturated polyester resins have been mainly used for manufacturing rigid laminated substrates, and polyester resins have been mainly used for manufacturing flexible substrates.

With the recent increase in wiring density, printed wiring board substrates are required to have heat resistance and low dielectric properties, and polyimide resins have emerged as a material satisfying these requirements. Polyimide resin has a long-term heat resistance of about 200
℃, dielectric constant (value at 1 MHz, same below) is 3.5
It has a relatively low value of ~ 3.7 and is extremely excellent as an insulating material for electronic parts. Taking advantage of this feature,
Polyimide resin is used in both forms of a flexible substrate and a rigid substrate impregnated with glass cloth. However, the dielectric constant of a rigid substrate using a polyimide resin varies depending on the glass fiber filling rate,
It is 4.5 to 4.7, which is higher than that of flexible boards.

Polyimide resin is suitable as an insulating material for electronic parts, but its use is sometimes restricted because it is an expensive resin. Further, the polyimide resin has a relatively high water absorption rate of about 3%. In order to further improve the performance of the printed wiring board, especially to increase the signal processing speed and increase the density,
There has been a demand for a printed wiring board substrate that uses a resin material that has heat resistance comparable to that of a polyimide resin, has a lower dielectric constant, particularly when a rigid substrate is used, and has a low water absorption.

As a substrate which meets this demand, the present inventor previously proposed in Japanese Patent Application No. 5-9455 a rigid and flexible substrate using a condensed polycyclic aromatic resin.
The condensed polycyclic aromatic resin is a raw material composed of a condensed polycyclic aromatic compound or a mixture of a condensed polycyclic aromatic compound and a monocyclic aromatic compound, and an aromatic compound having at least two hydroxymethyl groups or halomethyl groups. It is a resin obtained by reacting with a cross-linking agent composed of a group compound in the presence of an acid catalyst.

The condensed polycyclic aromatic resin has a long-term heat resistance temperature of about 260 ° C., which is higher than that of the polyimide resin.
At short-term (primary) heat resistance temperature, polyimide resin is 300 ℃
It has a very high heat resistance of over 200 ° C, but the long-term heat resistance required for printed wiring board substrates is about 200 ° C.
Very low with the degree. On the other hand, the condensed polycyclic aromatic resin has a short-term heat resistance temperature of about 260 ° C., but this heat resistance continues, and the long-term heat resistance shows a higher heat resistance temperature than the polyimide resin. Moreover, this resin has a low dielectric constant of 3.1, and when it is used as a rigid substrate, it has a dielectric constant of about 3.5.
It has properties that are very suitable for printed wiring board materials, such as a dielectric constant that does not increase and water absorption that is lower than that of polyimide resin.

Like the polyimide resin, the condensed polycyclic aromatic resin may be simply molded into a plate shape to form a flexible substrate, or a suitable reinforcing fiber (eg, glass cloth) may be formed. It is also possible to impregnate a resin to form a prepreg, and laminate and mold the prepreg to form a rigid laminated substrate. As a result, it is possible to obtain a high-quality printed wiring board substrate exhibiting performance equal to or higher than that of the polyimide-based substrate, which is currently the highest quality substrate. When a copper foil is joined to this substrate, a copper clad laminated substrate is obtained.

Generally, a flexible substrate and a copper foil are joined by an adhesive, but a rigid substrate (laminated substrate)
In this case, without using an adhesive, the copper foil is also laminated and hot pressed at the time of laminating and forming the prepreg, so that the copper foil and the substrate are joined by the impregnating resin of the prepreg simultaneously with the laminating. Therefore, the resin used is also required to have adhesiveness with copper foil, and in order to enhance the adhesive strength (peeling strength) of copper foil, various surface treatments have been performed on the adhesive surface of copper foil. .

[0010]

In the production of a rigid copper clad laminate using a prepreg impregnated with the above-mentioned condensed polycyclic aromatic resin, it is suitable to increase the adhesion between the copper foil and the resin. No means for surface treatment of copper foil has been found, and at present, untreated electrolytic copper foil is used as it is. Therefore, the adhesive strength between the laminated substrate and the copper foil was not sufficient, and the peel strength of the copper foil remained at a low level of about 0.3 kgf / cm.

The object of the present invention is particularly useful for producing a copper-clad laminated substrate containing the above condensed polycyclic aromatic resin as an impregnating resin,
It is intended to provide a surface-treated copper foil having an improved adhesive strength with a resin.

[0012]

The present inventors have found that the aromatic compound having at least two hydroxymethyl groups or halomethyl groups, which is a raw material used as a cross-linking agent in the production of the above condensed polycyclic aromatic resin. However, we found that it is the most suitable as a surface treatment agent for copper foil to enhance the adhesiveness to a laminated substrate, and that similar improvement in adhesiveness can also be obtained by surface treatment of a copper foil with a chromate treatment liquid. Completed the invention.

Here, the gist of the present invention is to produce a copper clad laminated substrate which has been surface-treated with an aromatic compound having at least two substituents selected from a hydroxymethyl group and a halomethyl group or a chromate treatment liquid. It is on copper foil.

The copper foil surface-treated with the above aromatic compound according to the present invention is particularly suitable for producing a copper clad laminate using the above condensed polycyclic aromatic resin, but a polyimide resin, a phenol resin, It can also be used to manufacture a copper clad laminate using an epoxy resin or the like as an impregnating resin, and in such a case, the adhesive strength of the copper foil can be increased. Also,
The copper foil surface-treated with the chromate treatment liquid can be used for manufacturing the above various copper clad laminated substrates.

[0015]

The condensed polycyclic aromatic resin is a raw material composed of a condensed polycyclic aromatic compound or a mixture of a condensed polycyclic aromatic compound and a monocyclic aromatic compound (eg, naphthalene, or a mixture of naphthalene and phenol). ) And a crosslinking agent composed of an aromatic compound having at least two hydroxymethyl groups or halomethyl groups [eg, dihydroxymethylbenzene (also known as xylylene glycol)], and an acid catalyst (eg,
It is a thermosetting resin obtained by reacting a raw material or a crosslinking agent in the presence of a reactive or water-insoluble sulfonic acid compound). This reaction can be carried out in the molten state, or in the form of a solution or dispersion.

In order to manufacture a rigid type laminated substrate, a reinforcing fiber is impregnated with the thermosetting resin (B stage resin) produced by the above reaction to manufacture a prepreg. The prepreg can be manufactured by either a solvent method or a hot melt method. The solvent method is a method of impregnating a reinforcing fiber with a resin solution (varnish) in which a resin is dissolved in an appropriate organic solvent, and removing the solvent by heating to obtain a prepreg. The hot melt method is a method of sandwiching a reinforcing fiber between two release papers coated with a resin which is heated and melted on at least one side, and passing the reinforcing fiber between heating rolls to melt the resin and impregnate the fiber. is there.

As the reinforcing fiber, any insulating fiber conventionally used for manufacturing a laminated substrate can be used, but it is usually glass fiber. Particularly, it is preferable to use glass fibers having a low dielectric constant. The form is cross,
Mats, tapes, etc. are possible, but most commonly glass cloth. The resin content in the prepreg is appropriately in the range of 20 to 60% by weight. The prepreg may contain, in addition to the condensed polycyclic aromatic resin and the reinforcing fiber, one or more kinds of various known additives such as a flame retardant and a coupling treatment agent.

By laminating about 5 to 20 sheets of the prepreg and thermocompressing the laminated body by a hot pressing method, and at the same time laminating and molding the resin to a desired degree, a rigid type laminated substrate is obtained. Suitable heat pressing conditions are a temperature of 120 to 230 ° C., a pressing force of 25 to 100 kgf / cm ² , and a holding time of 10 to 120 minutes. This hot pressing is usually performed after sandwiching the laminate between two copper foils. As a result, the rigid copper clad laminated board is directly manufactured. Thereafter, the surface of the copper foil is subjected to imaging, etching, and metal plating processing to manufacture a rigid printed wiring board. Even when the impregnating resin is another thermosetting resin such as a polyimide resin, the rigid copper-clad laminated substrate can be manufactured by the same method except that the resin is changed.

According to the present invention, there is provided a copper foil useful for manufacturing such a rigid copper clad laminated board. As described above, this copper foil has a surface treatment agent of at least 2 selected from hydroxymethyl group and halomethyl group.
The surface treatment is performed using either an aromatic compound having one substituent or a chromate treatment liquid. The copper foil used may be either an electrolytic copper foil or a rolled copper foil, but is usually an electrolytic copper foil.

The specific treatment method of this surface treatment is not particularly limited, but in the case of, a solution is prepared by dissolving the above aromatic compound in a suitable solvent (eg, lower alcohol such as methanol, cyclohexanone, etc.). It can be carried out by applying this solution to a copper foil by means such as spraying or dipping, and removing the solvent. Examples of aromatic compounds that can be used are o-, m- or p-dihydroxymethylbenzene (also known as o-, m- or p-xylylene glycol), dihydroxymethylxylenes, trihydroxymethylbenzenes, o -, M- or p-dichloromethylbenzene. Of these, preferred is o-, m- or p-dihydroxymethylbenzene.

After coating, the copper foil is heated to remove the solvent and simultaneously form a bond between the copper foil and the aromatic compound. This heating is performed, for example, in the air at 80 to 100 ° C.
The temperature may be about 0.5 to 2 hours. Amount of aromatic compounds deposited during this treatment (ie solution concentration and treatment time)
Is not particularly limited, and may be appropriately selected by experiments so that the above-mentioned object is achieved.

On the other hand, the treatment with the chromate treatment liquid can also be carried out by spraying or dipping the chromate treatment liquid on the copper foil and then heating to remove water as a solvent, as in the above. The chromate treatment liquid to be used is not particularly limited and may be either a coating type or a reaction type chromate treatment liquid. The chromate treatment liquid is a treatment liquid containing Cr ⁶⁺ (usually chromic anhydride) and a reducing agent, but the chromate treatment liquid used in the present invention is a coating type chromate treatment liquid containing at least colloidal silica. Is preferably used. The treatment liquid may further contain other additives.

Chromium adhesion amount by this chromate treatment
(That is, the chromate treatment condition) may be selected by experiment so that the purpose of improving the adhesion between the laminated substrate and the copper foil can be achieved, but it is possible to form an anticorrosion film on the surface of the metal material to be treated. Compared to the intended ordinary chromate treatment, the chromium deposition amount in the chromate treatment of the present invention may be relatively small. Therefore, for example, it is possible to use a lower concentration chromate treatment liquid or to reduce the spray amount of the chromate treatment liquid. Also in the case of chromate treatment, the copper foil is heated after coating, but unlike the usual chromate treatment, it is not necessary to completely reduce Cr ⁶⁺ to Cr ³⁺ , and only to evaporate the solvent. Preferably. This heating is suitable at, for example, 50 to 80 ° C. for about 2 to 30 minutes.

The reason why the adhesiveness (peeling strength) of the copper foil is increased when a rigid copper clad laminate is manufactured using the surface-treated copper foil of the present invention is not completely understood.
It can be considered as follows.

Generally, a copper foil has a thin film of copper oxide, basic copper oxide, or the like formed on the surface thereof by the reaction of oxygen with the air, and therefore, a hydroxyl group or an oxygen atom exists on the surface of the copper foil. is doing.

In the case of the copper foil surface-treated with the aromatic compound, the hydroxymethyl or halomethyl functional group of the aromatic compound is converted into a hydroxyl group or an oxygen atom on the surface of the copper foil by the heating during the surface treatment or the heating during the laminating and molding. A strong bond is generated between the copper foil and the aromatic compound by a dehydration reaction with or by forming a hydrogen bond. On the other hand, even during lamination molding in which a laminate of prepreg is sandwiched between surface-treated copper foils and hot pressed, the aromatic compound of the surface treatment agent is a component originally used as a crosslinking agent in the resin, The hydroxymethyl group or halomethyl group remaining in the surface treatment agent can undergo a condensation reaction (dehydration or dehydrohalogenation reaction) with a hydroxyl group or an aromatic hydrogen atom contained in the raw material in the resin. As a result, the aromatic compound, which is the surface treatment agent for the copper foil, is firmly bonded to both the copper foil and the cured resin of the laminated substrate, and a strong adhesive force is exhibited by crosslinking between the two.

On the other hand, in the case of the copper foil surface-treated with the chromate treatment liquid, Cr ⁶⁺ is reduced to Cr ³⁺ by heating during this treatment and heating during lamination molding, and Cr in the formed chromate film. An ether bond of —O—Cr is formed. The ether group and the hydroxyl group on the copper surface are hydrogen-bonded to firmly bond the copper foil and the surface treatment agent. Also, when heating during lamination molding, the Cr ⁶⁺ remaining in the chromate film is
^While being reduced to ³⁺ , exerts an oxidizing effect on the resin,
A carbonyl bond (> C = O) is formed in the resin skeleton, and van der Waals is formed between the carbon atom of the carbonyl bond in the resin and the ether group (oxygen atom of Cr-O-Cr) in the chromate film. A bond is formed and the surface treatment agent also bonds with the resin. Thereby, a strong adhesive force is developed between the resin and the copper foil.

The above-mentioned adhesive action with the resin is particularly remarkable when the resin is the above-mentioned condensed polycyclic aromatic resin, but also in the case of other resins (eg phenol resin, epoxy resin). The development of the adhesive force between the resin and the surface treatment agent can occur by a similar mechanism.

[0029]

EXAMPLES The present invention will be described in more detail below with reference to examples. In the examples, parts and% are parts by weight and% by weight, unless otherwise specified.

Example 1 An ethanol solution of p-xylylene glycol (10 mol% concentration) was prepared, and this solution was used as an electrolytic copper foil (thickness 35 μm, weight).
305 g / m ² ) (spray amount 100 g / m ² ), and then heated to 80 ° C. for 1 hour to complete the surface treatment. The surface appearance of the copper foil after this surface treatment was a pale red copper color.

On the other hand, a prepreg was manufactured by the following method. Naphthalene 100 parts, p-xylylene glycol 173
Part and a mixture of 8.3 parts of β-naphthalenesulfonic acid as a catalyst were subjected to an addition condensation reaction by heating and stirring at 110 ° C. for 3 hours to obtain a condensed polycyclic aromatic resin in a B stage state. This resin has a brown transparent appearance and is 70
Melt viscosity at ℃ 16,500 cps, number average molecular weight 580
Met. Dissolve this resin in tetrahydrofuran,
A resin varnish having a resin solid content of 50% and a room temperature viscosity of 50 cps was prepared. T-glass cloth (plain weave, thickness
0.1 mm, bulk density 104.5 g / m ² )
The glass fiber was impregnated with resin. Then, the glass cloth was dried at 60 ° C for 1 hour to remove the solvent, and the resin content of about 30
% Glass cloth prepreg was prepared.

The glass cloth prepregs were superposed on each other in such a number that a molded product having a thickness of 1.6 mm was obtained, and sandwiched between the two surface-treated copper foils as described above to obtain 100 kgf / cm.
^By heat pressing at 230 ° C. for 60 minutes under the pressure of ² to perform lamination molding, a rigid copper clad laminate having a thickness of about 1.6 mm was obtained.

In order to investigate the adhesive strength of the copper foil of the obtained copper-clad laminated substrate, the peel strength of the copper foil was measured according to JIS C6481 and found to be 1.0 kgf / cm. On the other hand, the peel strength of the copper foil in the case of a rigid copper-clad laminated substrate (conventional material) produced in the same manner using a copper foil that was not surface-treated was 0.3 kgf / cm, so the surface treatment of the present invention was performed. The use of copper foil increased the adhesive force more than 3 times.

Example 2 The electrolytic copper foil used in Example 1 was coated with a coating type chromate treatment liquid.
(Kansai Paint Co., Ltd., Cosmer 100) was sprayed with a 10-fold diluted solution with water (spray amount 100 g / m ² ), and then the solvent was evaporated by heating to 80 ° C. for 1 hour.

A rigid copper clad laminate was prepared in the same manner as in Example 1, using the copper foil surface-treated with the chromate treatment solution in this manner. The peel strength of the copper foil of this copper-clad substrate was still 1.0 kgf / cm, and the adhesive strength was remarkably increased as compared with the conventional material.

[0036]

As shown in the examples, the copper foil surface-treated with the above-mentioned aromatic compound or chromate treatment liquid according to the present invention can be used with any kind of treatment liquid to prepare rigid copper. The adhesive force between the copper foil and the laminated substrate can be significantly increased when the stretched laminated substrate is manufactured. As a result, the performance of printed wiring boards manufactured from this board,
Especially, the reliability is improved. INDUSTRIAL APPLICABILITY The present invention is particularly useful for copper-clad rigid laminated substrates containing condensed polycyclic aromatic resin as an impregnating resin, and the surface of a copper foil for this laminated substrate for which a suitable surface treatment method has not been established until now. This is the optimum processing.

Claims (2)

[Claims] 1. A copper foil for producing a copper-clad laminate, which is surface-treated with an aromatic compound having at least two substituents selected from a hydroxymethyl group and a halomethyl group. 2. A copper foil for producing a copper-clad laminated substrate, the surface of which is treated with a chromate treatment liquid.