JP2010105356A - Non-adhesive type copper-clad laminate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a nonadhesive type copper-clad laminate by a laminating method, high in adhesiveness between a copper foil and a resin, excellent in etching performance, and suitable for forming a fine pitch. <P>SOLUTION: This copper-clad laminate has structure bonded with the copper foil and a resin film via a thermoplastic resin, the copper foil is provided with a copper foil base material, and a coating layer for coating at least one part of a copper foil base material face, the coating layer is constituted of an Ni layer and a Cr layer laminated sequentially from the copper foil base material face, the coating layer contains respective coating amounts of 15-210 μg/dm<SP>2</SP>of Cr and 15-440 μg/dm<SP>2</SP>of Ni, a cross section of the coating layer has the maximum thickness of 0.5-5 mm when observed by a transmission electron microscope, and has the minimum thickness of 80% or more of the maximum thickness, the coating layer contacts with the thermoplastic resin, and a polyimide film and the thermoplastic resin have one, two or more of through holes penetrated therethrough. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an adhesiveless copper clad laminate, and more particularly to an adhesiveless copper clad laminate having a flying lead portion.

  In recent years, with the increasing needs for miniaturization and higher performance of electronic devices, higher density mounting of components and higher frequency of signals have progressed, and conductor patterns have become finer (fine pitch) and higher frequency than printed circuit boards. Response is required.

  Generally, a printed wiring board is manufactured through a process in which an insulating substrate is bonded to a copper foil to form a copper-clad laminate, and then a conductor pattern is formed on the copper foil surface by etching. Therefore, the copper foil for printed wiring boards is required to have adhesiveness and etching properties with an insulating substrate.

  Moreover, in order to improve adhesiveness with an insulating substrate, surface treatment for forming irregularities on a copper foil surface called roughening treatment is generally performed. For example, by using a copper sulfate acidic plating bath on the M surface (rough surface) of the electrolytic copper foil, a large number of coppers are electrodeposited in a dendritic or small spherical shape to form fine irregularities, and the adhesion is improved by the anchoring effect. There is. After the roughening treatment, a chromate treatment, a treatment with a silane coupling agent, or the like is generally performed in order to further improve the adhesive properties.

  In JP 2007-207812 A, a Ni-Cr alloy layer is formed on the surface of a copper foil, and an oxide layer having a predetermined thickness is formed on the surface of the alloy layer, whereby the surface of the copper layer is smooth and has an anchor effect. It is described that the adhesiveness with the resin base material is greatly improved even in a state where the amount of the resin is small. Then, a Ni—Cr alloy layer having a thickness of 1 to 100 nm is formed by vapor deposition on the surface, a Cr oxide layer having a thickness of 0.5 to 6 nm is formed on the surface of the alloy layer, and the average surface roughness RzJIS of the outermost surface is A printed circuit board copper foil having a thickness of 2.0 μm or less is disclosed.

In JP-A-2006-222185, in a surface-treated copper foil for a polyimide-based flexible copper-clad laminate, (1) Ni layer or / and Ni alloy containing 0.03-3.0 mg / dm ² in terms of Ni amount. (2) Chromate layer containing 0.03 to 1.0 mg / dm ^{2 in} terms of Cr, (3) Cr layer or / Cr alloy layer containing 0.03 to 1.0 mg / dm ^{2 in} terms of Cr (4) A chromate layer containing 0.03 to 1.0 mg / dm ^{2 of} Cr on the Ni layer and / or Ni alloy layer containing 0.03 to 3.0 mg / dm ^{2 of} Ni , (5) Cr layer in the Cr content on the Ni layer and / or Ni alloy layer in the Ni amount 0.03~3.0mg / dm ² containing containing 0.03~1.0mg / dm ² or / And by providing a Cr alloy layer as a surface treatment layer, a polyimide resin layer It is described that a copper foil for a polyimide-based flexible copper-clad laminate having a high peel strength and excellent insulation reliability, etching characteristics when forming a wiring pattern, and bending characteristics can be obtained. The thickness of the surface treatment layer is estimated on the order of μm from the above-mentioned Ni amount and Cr amount. In the examples, it is described that a surface treatment layer is provided using electroplating.

On the other hand, in recent years, as a method of mounting various electronic components on a printed wiring board, a method of realizing electrical contact by forming connector portions on both sides of the printed wiring board and electronic components and mechanically contacting both connector portions. Has been proposed. According to such a method, since the circuit board and the electronic component can be freely detached, the component can be easily removed and repaired even if a defect occurs in the electronic component.
In the contact portion of such a printed wiring board, the insulating substrate side has a through hole, and the metal side to be contacted closes the through hole of the resin layer. The portion of the through hole of the insulating substrate is called a flying lead portion. A specific example of such a circuit board is disclosed in Japanese Patent Application Laid-Open No. 2007-281253.

It is also known to provide a spiral contact formed in a spiral shape in the through hole of the insulating substrate. When the spherical contactor is brought into contact with the spiral contactor, the spiral contactor comes into contact with the outer surface of the spherical contactor so as to be spirally wound, so that the electrical connection is surely performed (for example, Japanese Patent Application Laid-Open No. 2005-260260). 2002-175859, Japanese Patent No. 3837434).
JP 2007-207812 A JP 2006-222185 A JP 2007-281253 A JP 2002-175859 A Japanese Patent No. 3837434

  In order to manufacture a printed wiring board having a flying lead portion as described above, a copper-clad laminate with a through hole in the insulating substrate must be manufactured, but a conventional acrylic or epoxy adhesive is used. When the insulating substrate and the copper foil are bonded together, the adhesive layer is exposed on the wall surface of the through hole. When the copper foil side is etched or the conductor pattern formed by etching is plated, the adhesive component is exposed to the etching solution or plating solution from the adhesive layer exposed on the wall, and the etching solution or plating solution is removed. There is a possibility of deteriorating. In addition, the adhesive layer may deteriorate, so that the adhesion between the substrate and the resin layer may be lost.

  Therefore, it is considered that an adhesiveless copper-clad laminate is promising. Non-adhesive type copper-clad laminates are known for producing by a casting method, a sputtering / plating method, and a laminating method. The casting method is a method in which a liquid polyimide precursor is applied to a copper foil, dried and then thermally cured. The sputtering / plating method is a method of laminating copper on the base film surface by sputtering or plating. The laminating method is a method of thermally laminating a copper foil on the surface of a composite film in which a thermoplastic polyimide resin is applied on a base polyimide film.

  However, in the casting method and sputtering / plating method, it is difficult to provide a through-hole before being bonded to the copper foil due to the manufacturing method, and in order to manufacture a printed wiring board having a flying lead portion, it was bonded to the copper foil. It is necessary to provide a through hole later. When forming a through-hole after manufacturing a copper clad laminated board, damage to copper foil is inevitable and there exists a possibility that the reliability of an electrical contact may be impaired. Thus, although it is considered that an adhesive-free copper-clad laminate by a laminating method is suitable, it cannot be said that the compatibility between the copper foil and the polyimide resin and the etching properties are still satisfactory.

  First, it is difficult to use the method of improving the adhesiveness by roughening treatment because it is disadvantageous for fine line formation. If the conductor spacing is narrowed by fine pitch, the roughened portion may remain on the insulating substrate after the circuit is formed by etching, which may cause insulation deterioration. In order to prevent this, if an attempt is made to etch the entire roughened surface, a long etching time is required, and a predetermined wiring width cannot be maintained.

  In the method of providing a Ni layer or a Ni—Cr alloy layer on the surface of the copper foil, there is much room for improvement in the basic characteristic of adhesion to an insulating substrate. Japanese Patent Application Laid-Open No. H10-228707 has a description that the adhesiveness to the resin base material can be improved even if the surface of the copper foil is smoothed by providing the Ni—Cr alloy layer, but there is still room for improvement.

  In the method of providing a Cr layer on the copper foil surface, relatively high adhesion can be obtained. However, the Cr layer has room for improvement in etchability. That is, the Cr layer has higher adhesiveness than the Ni layer, but Cr is inferior in etching property, so that after the etching process for forming the conductor pattern, the “etching residue”, in which Cr remains on the insulating substrate surface, is likely to occur. . In addition, the heat resistance is not sufficient, and there is a problem that the adhesion to the insulating substrate is significantly lowered after being placed in a high temperature environment. For this reason, it is hard to say that it is a promising technique under the circumstances where fine pitch of printed wiring boards is progressing. On the other hand, the chromate layer has room for improvement in adhesion.

Described in Patent Document 3, in the amount of Cr 0.03~1.0mg / dm ² contained over the 0.03~3.0mg / dm ² Ni layer containing and / or Ni alloy layer in the Ni amount Although the method of providing a Cr layer or / and a Cr alloy layer as a surface treatment layer can provide relatively high adhesion and etching properties, there is still room for improvement in characteristics.

  Therefore, an object of the present invention is to provide a non-adhesive type copper-clad laminate by a laminating method that has high adhesion between a copper foil and a polyimide resin, is excellent in etching properties, and is suitable for fine pitch formation. Moreover, this invention makes it another subject to provide the manufacturing method of such a copper clad laminated board.

  Conventionally, it was generally understood that the adhesive strength decreases when the coating layer is thinned. However, as a result of intensive studies, the present inventors have found that when a Ni layer and a Cr layer are sequentially provided on the surface of the copper foil base material with an ultrathin thickness of nanometer order, excellent adhesion to the insulating substrate It was found that sex can be obtained. By making the thickness extremely thin, the amount of Cr having low etching property is reduced, and the coating layer is uniform, which is advantageous for etching property.

The present invention completed on the basis of the above knowledge, in one aspect,
A copper clad laminate having a structure in which a copper foil and a resin film are bonded via a thermoplastic resin,
The copper foil comprises a copper foil base material and a coating layer covering at least a part of the surface of the copper foil base material;
The coating layer is composed of a Ni layer and a Cr layer laminated in order from the surface of the copper foil substrate;
The coating layer is present in a coverage of 15 to 210 μg / dm ² of Cr and 15 to 440 μg / dm ² of Ni;
-When the cross section of the coating layer is observed with a transmission electron microscope, the maximum thickness is 0.5 to 5 nm, the minimum thickness is 80% or more of the maximum thickness,
The coating layer is in contact with a thermoplastic resin;
The resin film and the thermoplastic resin have one or more through holes penetrating them;
It is a copper clad laminate.

In one embodiment of the copper clad laminate according to the present invention, the Cr coating amount is 18 to 100 μg / dm ² , and the Ni coating amount is 20 to 195 μg / dm ² .

In another embodiment of the copper clad laminate according to the present invention, the Cr coating amount is 30 to 150 μg / dm ² , and the Ni coating amount is 40 to 180 μg / dm ² .

  In yet another embodiment of the copper clad laminate according to the present invention, the copper foil base material is a rolled copper foil.

In yet another embodiment of the copper clad laminate according to the present invention, the copper foil base material is a rolled copper having a spring limit specified by JIS H3130 of 350 N / mm ² or more and a stress relaxation rate of 30% or less. It is a foil.

In another aspect of the present invention,
1) Covering copper foil by coating at least part of the surface of the copper foil substrate with a Ni layer having a thickness of 0.2 to 5.0 nm and a Cr layer having a thickness of 0.2 to 3.0 nm in this order by sputtering. Manufacturing process,
2) A process of forming a composite film by applying a thermoplastic resin to one or both sides of a resin film,
3) a step of forming one or more through holes in the composite film;
4) A step of thermally laminating the coated copper foil on the thermoplastic resin surface of the composite film with the portion coated with the Ni layer and the Cr layer inside.
It is a manufacturing method of the copper clad laminated board containing this.

  In one Embodiment of the manufacturing method of the copper clad laminated board which concerns on this invention, the thickness of the thermoplastic resin apply | coated to the single side | surface or both surfaces of a resin film is 1-5 micrometers.

  In still another aspect, the present invention is a printed wiring board made of the copper clad laminate according to the present invention.

  ADVANTAGE OF THE INVENTION According to this invention, the adhesiveness between copper foil and resin is high, it is excellent in etching property, and the non-adhesive type copper clad laminated board which has a flying lead part suitable for fine pitch formation can be obtained.

1. In a copper clad laminate having a copper foil base material flying lead portion, when the copper foil portion that closes the through hole of the resin base material functions as a contact material, the metal portion has heat due to an electric current. If this heat loses the metal spring elasticity, this part will not function as a contact material. Accordingly, in such a case, the copper foil used is required to have excellent spring elasticity and a low stress relaxation rate. Specifically, a copper foil base material having a spring limit specified by JIS H3130 of 350 N / mm ² or more and a stress relaxation rate of 30% or less is preferable. Examples of the copper foil base material satisfying such properties include copper foil base materials made of C2600, C7701, C7025, C5212, C1700, C18040, C64770, C19400, C64710, C42500, C64725, C64740, C44250, C19020, and C19025. Is mentioned. Of these copper alloys, a precipitation-type copper alloy and a copper alloy called a Corson alloy are excellent in strength, conductivity and spring property, and are preferable as a base material. In particular, C7025 is excellent because of its excellent stress relaxation property.

  There is no restriction | limiting in particular also about the thickness of the copper foil base material which can be used for this invention, What is necessary is just to adjust to the thickness suitable for printed wiring boards suitably. For example, it can be set to about 5 to 100 μm. However, for the purpose of forming a fine pattern, it is 30 μm or less, preferably 20 μm or less, and typically about 10 to 20 μm.

  The copper foil substrate used in the present invention is preferably not roughened. Conventionally, the surface roughening treatment is performed by applying irregularities of the order of μm on the surface by special plating, and the adhesion to the resin is given by the physical anchor effect. On the other hand, fine pitch and high frequency electrical characteristics are considered to be smooth foils, and roughened foils work in a disadvantageous direction. Further, since the roughening process is omitted, there is an effect of improving economy and productivity.

2. At least a portion of the surface of the coating layer copper foil base material is coated sequentially with Ni layer and Cr layer. The Ni layer and the Cr layer constitute a coating layer. Although there is no restriction | limiting in particular in the location to coat | cover, It is common to set it as the location where adhesion | attachment with an insulated substrate is planned. Adhesion with the insulating substrate is improved by the presence of the coating layer. In general, the adhesive force between a copper foil and an insulating substrate tends to decrease when placed in a high temperature environment, which is considered to be caused by thermal diffusion of copper to the surface and reaction with the insulating substrate. In this invention, the thermal diffusion of copper can be prevented by previously providing the Ni layer excellent in copper diffusion prevention on the copper foil base material. Further, by providing a Cr layer on the Ni layer that has better adhesion to the insulating substrate than the Ni layer, the adhesion to the insulating substrate can be further improved. Since the thickness of the Cr layer can be reduced by virtue of the presence of the Ni layer, the adverse effect on the etching property can be reduced. In addition, the adhesiveness as used in the present invention refers to adhesiveness after being placed under high temperature (heat resistance) and adhesiveness after being placed under high humidity (humidity resistance) in addition to normal adhesiveness. Also refers to.

  In the present invention, a Cr single layer coating having excellent adhesion to the resin is formed on the Ni coating as the outermost surface, and a thermoplastic resin having an imide bond is interposed between the copper foil and the base film. This is presumed to be because the single-layer coating structure having high adhesiveness is maintained even after the high temperature heat history during lamination. Further, it is considered that the etching property is improved by making the coating layer extremely thin and reducing the amount of Cr used as a two-layer structure of Ni and Cr.

(Effect of Ni / Cr layer-support-)
Moreover, since the Ni / Cr layer of this invention is harder than a copper foil base material, it is thought that it has a function which reinforces a flying lead part. For example, if the diameter of the through-hole formed in the resin layer is as large as several hundred μm, when a copper foil having a thickness of several tens of μm without a Ni / Cr layer coating is processed into a flying lead, the flying due to stress load in the component assembly process Although the lead portion may be damaged, the copper foil having the Ni / Cr layer reduces such possibility.

(Effect of Ni / Cr layer-Suppression of adhesion interface damage by etching etc.)
Furthermore, the Ni / Cr layer of the present invention also plays a role of suppressing adhesion interface damage due to etching or the like.
In a copper clad laminate in which a through hole is formed in a resin as in the present invention, a copper foil in the through hole portion is etched to form a circuit, a flying lead portion, and the like. Etching causes the copper foil to become thinner and thinner, and eventually the etching solution penetrates the copper foil. At this time, the cross section of the copper-clad laminate is exposed to the etching solution, and as in the present invention In the case of a laminated board using a simple copper foil without a Cr layer, the etching solution penetrates between the resin layer and the metal layer, causing peeling. However, in the present invention, when a Cr layer having a relatively slow corrosion rate exists on the outermost layer on the metal side and adheres to the resin layer, peeling of the adhesion interface is suppressed by side etching (in the radial direction of the through hole). be able to. For this reason, when the Ni / Cr layer is present, peeling at the joint can be prevented during etching for circuit formation.
In addition, the presence of a Cr layer with a relatively slow corrosion rate minimizes the penetration of liquid into the resin layer, and the damage to the resin layer is minimized.

  Specifically, the coating layer according to the present invention has the following configuration.

(1) Identification of Cr, Ni coating layer In the present invention, at least a part of the surface of the copper foil base material is coated in the order of the Ni layer and the Cr layer. These coating layers can be identified by sputtering argon from the surface layer with a surface analyzer such as XPS or AES, performing chemical analysis in the depth direction, and identifying the Ni layer and the Cr layer by the presence of each detection peak. Moreover, the order of covering from the position of each detection peak can be confirmed.

(2) Adhering amount On the other hand, since these Ni layer and Cr layer are very thin, it is difficult to evaluate the thickness accurately with XPS and AES. For this reason, in the present invention, the thicknesses of the Ni layer and the Cr layer are evaluated by the weight of the coated metal per unit area as in the patent document [Japanese Patent Laid-Open No. 2006-222185]. The coating layer according to the present invention Cr is the 15~210μg / dm ^2, Ni is present at a coverage of 15~440μg / dm ^2. When Cr is less than 15 μg / dm ² , sufficient peel strength cannot be obtained, and when Cr exceeds 210 μg / dm ² , the etching property tends to be significantly lowered. When Ni is less than 15 μg / dm ² , sufficient peel strength cannot be obtained, and when Ni exceeds 440 μg / dm ² , the etching property tends to be significantly reduced. The coverage of Cr is preferably 30 to 150 μg / dm ² , more preferably 50 to 100 μg / dm ² , and the coverage of Ni is preferably 20 to 195 μg / dm ² , more preferably 40 to 180 μg / dm ² , Typically 40 to 100 μg / dm ² .

(3) Observation by transmission electron microscope (TEM) When the cross section of the coating layer according to the present invention is observed by a transmission electron microscope, the maximum thickness is 0.5 nm to 5 nm, preferably 1 to 4 nm, and the minimum thickness. The coating layer has a thickness of 80% or more of the maximum thickness, preferably 85% or more, and very little variation. This is because when the coating layer thickness is less than 0.5 nm, the peel strength is greatly deteriorated in the heat resistance test and the moisture resistance test, and when the thickness exceeds 5 nm, the etching property decreases. When the minimum value of the thickness is 80% or more of the maximum value, the thickness of the coating layer is very stable and hardly changes after the heat test. Observation by TEM makes it difficult to find a clear boundary between the Ni layer and the Cr layer in the coating layer, and it looks like a single layer (see FIG. 3). According to the examination result of the present inventors, the coating layer found by TEM observation is considered to be a layer mainly composed of Cr, and the Ni layer is considered to exist on the copper foil base material side. Therefore, in the present invention, the thickness of the coating layer when observed by TEM is defined as the thickness of the coating layer that looks like a single layer. However, there may be a place where the boundary of the coating layer is unclear depending on the observation location, but such a location is excluded from the thickness measurement location. Since the structure of the present invention suppresses the diffusion of Cu, it is considered to have a stable thickness. The copper foil of the present invention adheres to the resin film, and even after the resin is peeled off after undergoing a heat resistance test (standing at 168 hours in a high temperature environment at 150 ° C. in an air atmosphere), the thickness of the coating layer is almost the same. Without change, the maximum thickness is 0.5 to 5.0 nm, and even at the minimum thickness, 70% or more, preferably 80% of the maximum thickness can be maintained.

3. Manufacturing method of coated copper foil The coated copper foil used in the present invention can be formed by sputtering. That is, at least a part of the surface of the copper foil base material by a sputtering method has a thickness of 0.2 to 5.0 nm, preferably 0.25 to 2.5 nm, more preferably 0.5 to 2.0 μm Ni layer and It can be produced by coating with a Cr layer having a thickness of 0.2 to 3.0 nm, preferably 0.25 to 2.0 nm, more preferably 0.5 to 1.5 μm. When such an extremely thin film is laminated by electroplating, the thickness varies, and the peel strength tends to decrease after the heat and humidity resistance test.
The thickness here is not the thickness determined by the XPS or TEM described above, but the thickness derived from the film formation rate of sputtering. The deposition rate under a certain sputtering condition can be measured from the relationship between the sputtering time and the sputtering thickness by performing sputtering of 1 μm (1000 nm) or more. Once the deposition rate under the sputtering conditions can be measured, the sputtering time is set according to the desired thickness. Sputtering may be performed continuously or batchwise, and the coating layer can be uniformly laminated with a thickness as defined in the present invention. Examples of the sputtering method include a direct current magnetron sputtering method.

4). Production Method of Composite Film In the present invention, a composite film used as an insulating substrate can be produced by applying a thermoplastic resin to one side or both sides of a resin film that is a base film. The resin used as a base film for the composite film is not particularly limited, but a suitable resin film is a polyimide film, for example, DuPont's Kapton EN series (trade name) or Ube Industries' Upilex R series. , S series (trade name). The thermoplastic resin is not particularly limited, but a thermoplastic polyimide is typical. Suitable thermoplastic polyimides include, for example, AURUM (trade name) manufactured by Mitsui Chemicals, AVIMID (trade name) manufactured by DuPont, and VESPEL (product). Name).

  If the thickness of the thermoplastic resin applied to the base film is too thick, the influence of the thermoplastic resin on various properties of the composite film becomes large, and the characteristics of the base film are not sufficiently exhibited. On the other hand, if the thickness of the thermoplastic resin is too thin, smears may occur and the adhesive force may not be uniform. Therefore, the thickness of the thermoplastic resin is preferably 1 to 5 μm, and more preferably 1 to 3 μm.

5. Manufacturing method of copper-clad laminate The copper-clad laminate according to the present invention is manufactured by thermally laminating the above-mentioned coated copper foil on the thermoplastic resin surface of the composite film with the portion coated with the Ni layer and the Cr layer inside. can do. The heating temperature when laminating is higher than the glass transition temperature of the thermoplastic resin constituting the composite film. However, if the temperature is too high, the thermoplastic resin will deteriorate and good adhesion will not be obtained. do not have to. For example, a temperature 20 to 200 ° C. higher than the glass transition temperature is sufficient.

  When manufacturing a copper clad laminate having a flying lead portion, one or more through holes may be formed in the composite film before the composite film is heat laminated to the copper foil. As a method of forming the through hole, there are laser processing and press processing. Laser processing is expensive when the number of through holes per unit area is large. Press working is preferable because punching can be performed in a large amount in a short time.

  Moreover, when the copper foil part which closes the through-hole of a resin base material functions as a contact material, you may make this part into a spiral form or a circuit form depending on necessity.

  A printed wiring board (PWB) can be produced according to a conventional method using the above copper-clad laminate as a material. The process for producing a printed wiring board from a copper clad laminate may be performed by a method well known to those skilled in the art. For example, an etching resist is applied only to a necessary portion as a conductor pattern on the copper foil surface of the copper clad laminate, and an etching solution By spraying on the copper foil surface, the unnecessary copper foil can be removed to form a conductor pattern, and then the etching resist can be peeled and removed to expose the conductor pattern. In the copper clad laminate according to the present invention, no acrylic or epoxy adhesive is used, and contamination of the etchant during etching is prevented.

  EXAMPLES Examples of the present invention will be described below, but these are provided for better understanding of the present invention and are not intended to limit the present invention.

[I. Evaluation of adhesiveness and etching property of coated copper foil]
Example 1
As a copper foil base material, a rolled copper foil having a thickness of 18 μm (Nikko Metal C70251100) was prepared. The rolled copper foil, a spring limit value defined by JIS H3130 is 610N / mm ^2, the stress relaxation rate was 75%.
As stress relaxation characteristics at high temperatures, the stress relaxation rate (Technical Standard of Japan Copper and Brass Association (JCBA): JCBA T309) was measured. In this test, a strip test piece having a width of 10 mm is attached to a cantilever beam, the deflection displacement (displacement at a predetermined position at the free end) after being held for a predetermined time in a high-temperature bending state is compared with the initial state, and a sag due to temperature is observed. It is a method to evaluate. When the deflection after the test and the initial state does not change, the value of the stress relaxation rate is 0%, and as the deflection after the test becomes larger than the initial state, the value of the stress relaxation rate increases (stress decreases).
The stress relaxation rate is:
Stress relaxation rate = (y−y1) / y0 × 100 (%)
(Where, y = deflection displacement (mm) after elapse of a predetermined time, y1 = initial deflection (mm), y0 = set height (mm)).
The set height is the following formula:
y0 = (2/3) × l × l × σ0 / (E × t)
(Where, l = target distance (mm), σ0 = load stress (kg / mm ² ); 80% of 0.2% proof stress or any stress below 0.2% proof stress, E = Young's modulus (kg / mm ² ), t = plate thickness (mm)).
The stress relaxation was measured until the sample was 150 ° C. and showed a certain relaxation rate. Specifically, the stress relaxation rate was measured for 25, 50, 100, and 200 hours, and a substantially constant stress relaxation rate was shown in about 1000 hours. This value was taken as the stress relaxation rate.

A Ni layer and a Cr layer were sequentially formed on one side of the copper foil under the following conditions. The thickness of the coating layer was changed by adjusting the film formation time (Examples 1 to 3, Comparative Examples 1 and 2). In Comparative Example 3, a Ni—Cr alloy layer was formed.
-Equipment: Batch type sputtering equipment (ULVAC, Model MNS-6000)
・ Achieving vacuum: 1.0 × 10 ⁻⁵ Pa
・ Sputtering pressure: 0.2 Pa
·target:
For Ni layer = Ni (purity 3N)
For Cr layer = Cr (purity 3N)
For Ni—Cr alloy layer = Ni: 80 mass%, Cr 20 mass% Ni—Cr alloy ・ Sputtering power: 50 W
Film formation rate: About 2 μm of film was formed for each target for a certain time, the thickness was measured with a three-dimensional measuring device, and the sputtering rate per unit time was calculated. (Ni: 2.73 nm / min, Cr: 2.82 nm / min)

A polyimide film was bonded to the copper foil provided with the coating layer by the following procedure.
(1) Applying AURUM PL450C made by Mitsui Chemicals Co., Ltd. to 1 μm with a dry body using a 7 cm × 7 cm Toray DuPont Kapton 80EN (thickness 20 μm).
(2) The composite film obtained in (1) is dried at 130 ° C. for 30 minutes in an air dryer.
(3) Hot pressing (pressure 0.75 MPa, temperature 350 ° C.) so that the composite film obtained in (2) and the copper foil are brought into contact with the Cr coating layer of the copper foil on the surface coated with the thermoplastic polyimide. For 15 seconds).

<Measurement of adhesion amount>
A film on the surface of a copper foil of 50 mm × 50 mm is dissolved in a mixed solution of HNO ₃ (2% by weight) and HCl (5% by weight), and the metal concentration in the solution is measured by an ICP emission spectrometer (SII Nanotechnology). The amount of metal per unit area (μg / dm ² ) was calculated by quantitative determination using SFC-3100).
<Measurement by XPS>
The operating conditions of XPS when creating the depth profile of the coating layer are shown below.
・ Device: XPS measuring device (ULVAC-PHI, Model 5600MC)
・ Achieving vacuum: 3.8 × 10 ⁻⁷ Pa
X-ray: Monochromatic AlKα, X-ray output 300 W, detection area 800 μmφ, angle between sample and detector 45 °
Ion beam: ion species Ar ⁺ , acceleration voltage 3 kV, sweep area 3 mm × 3 mm, sputtering rate 2.3 nm / min (SiO ₂ conversion)
<Measurement by TEM>
The measurement conditions of TEM when the coating layer is observed by TEM are shown below. The thickness shown in the table is the thickness of the entire coating layer reflected in the observation visual field, and the maximum and minimum values of the thickness between 50 nm are measured for one visual field. The maximum value and the ratio of the minimum value to the maximum value were determined as percentages. Also, in the table, the TEM observation result after “heat resistance test” means that after the polyimide film is adhered on the coating layer of the test piece by the above procedure, the test piece is placed in the following high-temperature environment and obtained. It is a TEM image after peeling a polyimide film from a piece according to 180 degree peeling method (JIS C 6471 8.1). In FIG. 1, the observation photograph immediately after sputtering by TEM is shown exemplarily for the copper foil of Example 3.
-Equipment: TEM (Hitachi, Ltd., model H9000NAR)
・ Acceleration voltage: 300 kV
-Magnification: 300,000 times-Observation field: 60 nm x 60 nm

<Adhesion evaluation>
For the copper foil laminated with polyimide as described above, the peel strength was immediately after lamination (normal state), after being left in a high-temperature environment at a temperature of 150 ° C. in an air atmosphere for 168 hours (heat resistance), and at a temperature of 40 ° C. relative The measurement was performed under three conditions: after being allowed to stand for 96 hours in a high humidity environment with a humidity of 95% air (humidity resistance). The peel strength was measured according to the 180 ° peeling method (JIS C 6471 8.1).

<Etching evaluation>
For the copper foil laminated with polyimide as described above, a circuit pattern of line and space 20 μm / 20 μm is formed using a predetermined resist, and then an etching solution (ammonia water, cupric chloride dihydrate, temperature (40 ° C.). The resin surface between the treated circuits was measured with EPMA, the remaining Cr and Ni were analyzed, and evaluated according to the following criteria.
×: Cr or Ni was observed on the entire surface between the circuits Δ: Cr or Ni was partially observed between the circuits ○: Cr or Ni was not observed between the circuits

  The measurement results are shown in Table 1. For reference, the depth profile by XPS is shown in FIG. 2 for the copper foil of Example 3 of Example 1.

Example 2 (comparison)
In Comparative Examples 4 and 5, Ni electroplating and chromate treatment were sequentially performed under the following conditions. This comparative example is for comparison with the method taught in Japanese Patent Application Laid-Open No. 2006-222185.
(1) Ni plating / plating bath: nickel sulfamate (110 g / L as Ni ²⁺ ), H ₃ BO ₃ (40 g / L)
・ Current density: 1.0 A / dm ²
・ Bath temperature: 55 ℃
Ni content: 95 μg / dm ² (thickness approximately 1.1 nm)
(2) Chromate treatment / plating bath: CrO ₃ (1 g / L), Zn (powder 0.4 g), Na ₃ SO ₄ (10 g / L)
Current density: 2.0 A / dm ²
・ Bath temperature: 55 ℃
Cr amount: 37 μg / dm ² (thickness about 0.5 nm)

  The composite film was bonded to the copper foil provided with the coating layer by the same procedure as in Example 1. The evaluation results are shown in Table 1.

[II. Evaluation of the degree of contamination of the plating solution and damage to the adhesive interface caused by the etching solution]
Example 3
Example 4
A two-layer copper clad laminate was produced in the same manner as in Example 3 except that 19600 (7 cm × 7 cm) through-holes were formed in the composite film by press working and copper foil was laminated.

(Comparative Example 6)
A composite film obtained by applying Kapton 80EN as a base film and applying an epoxy adhesive thereon was provided with 19600 through holes (7 cm × 7 cm) by pressing. This composite film and the copper foil of Example 3 were bonded so that the adhesive layer and the coating layer on the copper foil were inside, to prepare a three-layer copper-clad laminate.

(Comparative Example 7)
A composite film having through-holes produced in the same procedure as in Comparative Example 6 and a copper foil not provided with a coating layer were bonded together by lamination to obtain a three-layer copper-clad laminate.

(Comparative Example 8)
Moreover, the resin composite which has the through-hole produced in the same procedure as Example 4 and the copper foil which does not provide the coating layer were adhere | attached by the lamination, and the 2 layer copper clad laminated board was obtained.

About said copper clad laminated board, it immersed for 5 minutes in the electroless-plating liquid of the following composition described in Unexamined-Japanese-Patent No. 2006-228743.
<Plating solution composition>
NiSO ₄ · H ₂ O 0.1 mol / L
NaH ₂ PO ₂ .6H ₂ O 0.2 mol / L
Citric acid 0.5 mol / L
(NH ₄ ) ₂ SO ₄ 0.5 mol / L
The results are shown in Table 2. The case where dirt was visually confirmed on the plating solution surface was rated as x, and the case where it was not confirmed was marked as ◯.

In addition, for a copper-clad laminate similar to the above, using a predetermined resist, a circuit pattern with a line and space of 30 μm is prepared from the flying lead portion from the copper foil side, and then an etching solution (ferric chloride, 40 Baume, The flying lead part (copper foil part on the resin layer through-hole) of the copper clad laminate was etched using a liquid temperature of 40 ° C. The etching solution was sprayed from the copper foil side by a spray method (pressure 0.15 MPa). Thereafter, the sample was buried in a resin and polished appropriately, and the adhesion interface of the through-hole wall surface of each copper-clad laminate was observed with an SEM.
In the two-layer laminate having the coating layer of the present invention, it was not observed that the resin and the metal layer were corroded by the liquid, and the resin and the metal layer were sufficiently in contact with the wall surface of the through hole (Example 4, Comparative Example 6). In Comparative Examples 6 and 7 using an epoxy adhesive, the plating solution was soiled. In the three-layer laminate (Comparative Example 7) and the two-layer laminate (Comparative Example 8) having no coating layer of the present invention, corrosion of the adhesive interface on the wall surface of the through hole was observed.

4 is a TEM photograph of the copper foil of Example 3 of Example 1. FIG. It is a depth profile by XPS about the copper foil of Example 3 of Example 1. FIG.

Explanation of symbols

1 Thickness of coating layer during TEM observation

Claims (8)

A copper clad laminate having a structure in which a copper foil and a resin film are bonded via a thermoplastic resin,
The copper foil comprises a copper foil base material and a coating layer covering at least a part of the surface of the copper foil base material;
The coating layer is composed of a Ni layer and a Cr layer laminated in order from the surface of the copper foil substrate;
The coating layer is present in a coverage of 15 to 210 μg / dm ² of Cr and 15 to 440 μg / dm ² of Ni;
-When the cross section of the coating layer is observed with a transmission electron microscope, the maximum thickness is 0.5 to 5 nm, the minimum thickness is 80% or more of the maximum thickness,
The coating layer is in contact with a thermoplastic resin;
The resin film and the thermoplastic resin have one or more through holes penetrating them;
Copper-clad laminate. The copper clad laminate according to claim 1, wherein the Cr coating amount is 18 to 100 µg / dm ² and the Ni coating amount is 20 to 195 µg / dm ² . The copper clad laminate according to claim 1, wherein the Cr coating amount is 30 to 150 μg / dm ² and the Ni coating amount is 40 to 180 μg / dm ² .   The copper-clad laminate according to any one of claims 1 to 3, wherein the copper foil base material is a rolled copper foil. The copper-clad laminate according to any one of claims 1 to 4, wherein the copper foil base material is a rolled copper foil having a spring limit specified by JIS H3130 of 350 N / mm ² or more and a stress relaxation rate of 30% or less. . 1) Covering copper foil by coating at least part of the surface of the copper foil substrate with a Ni layer having a thickness of 0.2 to 5.0 nm and a Cr layer having a thickness of 0.2 to 3.0 nm in this order by sputtering. Manufacturing process,
2) A process of forming a composite film by applying a thermoplastic resin to one or both sides of a resin film,
3) a step of forming one or more through holes in the composite film;
4) A step of thermally laminating the coated copper foil on the thermoplastic resin surface of the composite film with the portion coated with the Ni layer and the Cr layer inside.
The manufacturing method of the copper clad laminated board containing this.   The manufacturing method according to claim 6, wherein the thickness of the thermoplastic resin applied to one or both sides of the resin film is 1 to 5 μm.   A printed wiring board made of the copper-clad laminate according to any one of claims 1 to 5.

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