JP5479668B2 - Surface treated copper foil - Google Patents

Description

  The present invention relates to a surface-treated copper foil used for printed wiring boards, FPCs, COFs, and the like, and particularly relates to a surface-treated copper foil having excellent heat resistance and chemical resistance and excellent adhesion to a polyimide film.

  Recently, with the miniaturization and complexity of printed wiring incorporated in various home appliances, electronic products, computers, etc., printed wiring boards that can withstand harsh conditions have been demanded and used for such printed wiring boards. Even for copper foils that are produced, characteristics such as high adhesion strength between the copper foil part after wiring board creation and the substrate, excellent chemical resistance, excellent heat resistance during heating, etc. It has been demanded.

When a printed wiring board is produced using a copper clad laminate, the adhesive boundary layer between the copper foil and the substrate is exposed to a solution containing hydrochloric acid in various activation treatment processes such as a pickling process and a plating pretreatment. After applying the resist, the circuit is exposed to an etching solution when pattern etching is performed. At this time, in the copper foil having poor resistance to hydrochloric acid and etching solution, the so-called undercut phenomenon that the hydrochloric acid solution and the etching solution invade into the bonding surface between the copper foil of the circuit portion and the substrate below it and erodes the portion. Occur.
Also, as the use of printed wiring boards expands, printed wiring boards may be used at high temperatures. When the printed wiring board is heated for a long time, the copper in the circuit portion of the printed wiring board is less than the substrate resin. A phenomenon occurs in which the substrate resin is decomposed at the joint surface with the copper foil and the peel strength between the copper foil and the substrate is deteriorated by acting as a catalyst.

In order to solve these problems, a proposal has been made to provide a metal layer having chemical resistance and heat deterioration resistance on the surface of the copper foil. As an example of a metal layer having chemical resistance and heat deterioration resistance, a nickel layer For example, a technique of containing chromium in a glass has been proposed (see, for example, Patent Document 1). However, a metal layer containing nickel in chromium is excellent in improving acid resistance and heat resistance, but has not yet achieved sufficient adhesion to polyimide.
Japanese Patent Publication No. 6-54829

  The present invention is a printed wiring board, copper foil for COF and FPC, and the bonding surface between the copper foil and the resin substrate is excellent in heat resistance and chemical resistance, and improves the adhesion to the resin substrate, particularly the polyimide film. An object is to provide a surface-treated copper foil.

The first surface treatment copper foil of the present invention, on at least one surface of the copper foil, nickel - cobalt alloy or nickel - is a first layer consisting of phosphorus alloy formation, the molybdenum in the first layer on the Two layers are formed, and the content of cobalt or phosphorus contained in the nickel-cobalt alloy or nickel-phosphorus alloy is 0.1 to 40 % with respect to nickel.

The second surface treatment copper foil of the present invention, on at least one surface of the copper foil, nickel - cobalt alloy or nickel - is a first layer consisting of phosphorus alloy is formed, and molybdenum in the first layer on the - cobalt alloy Or a surface-treated copper foil on which a second layer made of a molybdenum-chromium alloy is formed, wherein the nickel-cobalt alloy or nickel-phosphorus alloy, and the cobalt-phosphorus contained in the molybdenum- cobalt alloy or molybdenum-chromium alloy The chromium content is 50% or less of the total amount of the nickel alloy and the molybdenum alloy .

Preferably, the molybdenum content of the second layer is a 0.002~0.5mg / dm ^2.

  Preferably, the amount of molybdenum contained in the molybdenum alloy forming the second layer is 3 to 75% of the surface metal adhesion amount.

  Preferably, the copper foil is an electrolytic copper foil, and the surface-treated copper foil in which the first layer and the second layer are formed on the M surface of the electrolytic copper foil (the surface that is not in contact with the drum during electrolytic film formation). The surface roughness of the M surface of the electrolytic copper foil is Rz: 1.5 μm or less, Ra: 0.3 μm or less, and the foil thickness is 5 to 35 μm.

  Preferably, the copper foil has a granular crystal in cross section.

  The present invention is a printed wiring board, a copper foil for COF and FPC, and has excellent heat resistance and chemical resistance at the joint surface between the copper foil and the resin substrate, and improved adhesion to the resin substrate, particularly a polyimide film. The surface-treated copper foil can be provided.

  Hereinafter, embodiments of the present invention will be described in detail.

The present invention is a surface-treated copper foil in which a surface treatment layer is provided on the surface of the copper foil. As the copper foil before the surface treatment (hereinafter simply referred to as copper foil or untreated copper foil), an electrolytic copper foil and a rolled foil used for printed wiring boards, COF and FPC are used.
Considering the fine patterning of the circuit formed on the substrate, the thickness of the copper foil is better, and in order to flow a large amount of information in a short time, the thicker one with better high-frequency characteristics is preferred. The foil thickness changes accordingly.
As for the copper foil thickness of this invention, 5-35 micrometers is desirable. Further, the surface roughness of the side of the untreated copper foil that is in close contact with the resin is preferably Rz: 0.1 to 1.5 μm. This is because a foil having a roughness Rz larger than 1.5 μm is unsuitable for fine patterning, and the surface of the attached resin is roughened, so that the visibility is deteriorated.
Regarding the roughness of the copper foil surface, it is necessary to consider surface undulations, and the value of Ra is preferably 0.3 μm or less. This is because even if Rz is 1.5 μm, if Ra is 0.3 μm or more, the same problem as described above may be caused.
The Rz and Ra are numerical values measured by a measurement method based on JIS.

In the surface treatment of the copper foil, first, nickel or a nickel alloy is formed as a first layer on the surface of the copper foil from the viewpoint of heat resistance and chemical resistance. The adhesion amount of nickel or nickel alloy as metallic nickel is preferably 0.05 mg / dm ² or more. Considering the etching property in particular, it is preferably 0.05 mg / dm ² or more and 1.0 mg / dm ² or less.
As the metal other than nickel constituting the nickel alloy, phosphorus and cobalt are preferable, and the content thereof is preferably 0.1% to 40% with respect to nickel. When the amount of metal contained in nickel is large, the etching property is improved. However, in order to deteriorate the heat resistance and chemical resistance which are the objects of the present invention, it is suitable to form an alloy in the above range. As will be described later (see Comparative Example 1), a surface-treated copper foil in which a first layer made of nickel or a nickel alloy is formed on the surface of the copper foil is used as a sample, and a polyimide film is pasted on the surface. The degradation rate of the peel strength of the time-heated sample is reduced by 40% compared to the initial peel.

A second layer made of molybdenum or a molybdenum alloy is formed on the first layer made of nickel or a nickel alloy. The second layer uses molybdenum alone or a molybdenum alloy bath, and is formed by plating so that molybdenum metal adheres in the range of 0.5 mg / dm ² or less. It is not preferable to deposit molybdenum metal in an amount of 0.5 mg / dm ² or more because there is a limit to the effect of increasing the peel strength, and since it is a metal that is difficult to plate, uneven thickness will occur on the surface.
The molybdenum alloy as the second layer to be deposited on the nickel or nickel alloy of the first layer preferably has a molybdenum metal content of 3 to 75%, more preferably 20 to 60%.

Considering the etching property, trapezoidal etching, and heat resistance, the combination of the metal forming the first layer and the second layer and the amount of adhesion thereof will be considered.
The first layer is nickel, when the second layer formed thereon is molybdenum, deposited amount of nickel is preferably from 0.05~0.3mg / dm ^2.
When the first layer is a nickel alloy and the second layer is molybdenum, the nickel adhesion amount is preferably 0.1 to 1.0 mg / dm ² , and further suppresses trapezoidal formation during etching or etching damage. Therefore, the amount of metal other than nickel and molybdenum metal is preferably 40% or less of the total amount of nickel and molybdenum.
When the first layer is a nickel alloy and the second layer is a molybdenum alloy, the nickel adhesion amount is preferably 0.1 to 1.0 mg / dm ² as described above. In order to suppress, the amount of metal other than nickel and molybdenum metal is preferably 50% or less of the total amount of nickel and molybdenum.

The surface treatment layer may be formed by any method such as an electroplating method, an electroless plating method, a vacuum deposition method, or a sputtering method. However, in consideration of mass productivity, the method by electroplating is most suitable in practice.
When the surface treatment layer (first layer, second layer) is formed by plating, that is, when nickel simple substance or nickel alloy, molybdenum simple substance or molybdenum alloy is plated on copper foil, a normal bath (commercial bath) is used. Can be used.

After performing the said surface treatment to untreated copper foil, it is preferable to give a rust prevention process on a surface treatment layer. For rust prevention treatment, chromate treatment or zinc film formation and chromate treatment are used in combination. These treatments serve to increase the corrosion resistance of the copper foil surface. Chromium may have an effect on peel strength. In the case of chromate treatment, there is an effect of increasing the hydrochloric acid resistance of the copper foil surface. The chromate treatment can be performed by cathodic electrolysis in a chromic acid treatment solution, and chromium oxide or chromium hydrated oxide is deposited on the surface to be treated. The chromic acid treatment liquid used here is an aqueous solution of an alkali metal salt or ammonium salt of chromic acid or dichromic acid in addition to an aqueous solution of chromic acid alone.
In the case of the zinc film and the chromate treatment, it is mainly performed for the purpose of preventing heat discoloration of the surface not bonded to the copper foil substrate when the resin substrate and the copper foil are pressed. On the other hand, it also serves to prevent a reduction in beer strength during heating between the copper foil and the resin substrate. However, care should be taken because the hydrochloric acid resistance deteriorates if the zinc film is made thicker than necessary.

  The silane coupling agent treatment aims to improve peel strength. Examples of the silane coupling agent include epoxy, amino, and vinyl. The most effective silane coupling agent is selected depending on the resin material to be applied or pasted, and is applied on the surface treatment layer or the rust prevention treatment layer.

  Next, an example of a plating bath and plating conditions for treating the surface treatment layer will be described.

<Ni and Ni alloy plating bath conditions>
(Condition 1) Nickel plating conditions
_{NiSO 4 · 6H 2 O 10~500g /} l
H ₃ BO ₃ 1-50 g / l
Current density 1-50A / dm ²
Bath temperature 10-70 ° C

(Condition 2) Nickel-cobalt plating conditions
_{NiSO 4 · 6H 2 O 10~500g /} l
CoSO ₄ · 7H ₂ O 5-100 g / l
Temperature 10-60 ° C
Current density 1-20A / dm ²
Time 1-60 seconds

(Condition 3) Nickel-phosphorus plating conditions
_{NiSO 4 · 6H 2 O 10~500g /} l
_{NaPH 2 O 2 · H 2 O} 0.1~30g / l
Temperature 10-60 ° C
Current density 1-20A / dm ²
Time 1-60 seconds

<Mo or Mo alloy plating>
(Condition 4) Molybdenum plating conditions
_{Na 2 MoO 4 · 2H 2 O} 1~50g / l
H ₃ PO ₄ 5-40 g / l
PH 1-3
60 ° C
Time 0-120 seconds
Current density 0.05-2A / dm ²

(Condition 5) Molybdenum-cobalt plating conditions
Na ₂ MoO ₄ · 2H ₂ O 1 to 200 g / l
CoSO ₄ · 7H ₂ O 1-100 g / l
3 sodium citrate dihydrate 30-300 g / l
Current density 1-50A / dm ²
Bath temperature 10-70 ° C

(Condition 6) Molybdenum-chromium plating conditions
_{Na 2 MoO 4 · 2H 2 O} 1~50g / l
Chromic anhydride 1-50g / l
3 sodium citrate dihydrate 30-200 g / l
Current density 1-50A / dm ²
Bath temperature 10-70 ° C

The following copper foil was subjected to surface treatment under the conditions described in each example and each comparative example.
<Electrolytic copper foil>
Copper foil: Electrolytic copper foil (crystal; granular crystal)
Foil thickness: 12μm
Surface to which surface treatment is applied: M surface ((the surface opposite to the surface (S surface) that is in close contact with the drum during the production of electrolytic copper foil))
Roughness of the surface to be surface-treated: Rz is 0.7 μm, and Ra is 0.18 μm.

Example 1
On the M surface of the electrolytic copper foil, plating was performed for 8 seconds within the condition range of condition 1, nickel was formed (first layer), and plating was performed for 10 seconds within the condition range of condition 4 thereon, and molybdenum was coated. It was made to adhere (2nd layer), the rust prevention metal Zn * Cr was made to adhere after that, and the silane process was performed.
Table 1 shows the amount of each metal deposited on the surface of the copper foil.

Example 2
On the M surface of the electrolytic copper foil, a nickel-cobalt layer is formed by plating for 15 seconds within the condition range of condition 2, and then plated for 8 seconds within the condition range of condition 5, and then a molybdenum-cobalt alloy. Then, a rust preventive metal Zn · Cr was attached, and silane treatment was performed.
Table 1 shows the amount of each metal deposited on the surface of the copper foil. Cobalt was 41% of the total amount of nickel-cobalt and molybdenum-cobalt at this time.

Example 3
On the M surface of the electrolytic copper foil, a nickel layer containing phosphorus is formed by plating for 12 seconds within the condition range of condition 3, and then plated for 14 seconds within the condition range of condition 4 thereon. A molybdenum layer was formed, and a rust preventive metal Zn · Cr was adhered thereon, and silane treatment was performed.
Table 1 shows the amount of each metal deposited on the surface of the copper foil. At this time, phosphorus was 8.1% based on the total amount of nickel metal and molybdenum metal containing phosphorus.

Example 4
On the M surface of the electrolytic copper foil, a nickel layer containing phosphorus was formed for 15 seconds within the condition range of condition 3, and then a molybdenum layer was plated thereon for 20 seconds within the condition range of condition 5. -A cobalt layer was formed, and a rust preventive metal Zn · Cr was adhered thereon, and silane treatment was performed.
Table 1 shows the amount of each metal deposited on the surface of the copper foil. At this time, the total amount of phosphorus and cobalt with respect to the total amount of nickel-phosphorus and molybdenum-cobalt metal was 30.5% .

Example 5
On the M surface of the electrolytic copper foil, a nickel layer was formed by plating for 10 seconds within the condition range of Condition 1, and then a molybdenum-chromium layer was formed thereon by plating for 8 seconds within the condition range of Condition 6. A film was formed, and a rust preventive metal Zn · Cr was adhered thereon, and silane treatment was performed.
Table 1 shows the amount of each metal deposited on the surface of the copper foil. At this time, chromium was 19.5% with respect to the total metal amount of nickel metal and molybdenum-chromium.

Comparative Example 1
Nickel plating conditions
_{NiSO 4 · 6H 2 O 60~180g /} l
NaCI 15g / l
Temperature 20 ° C
Current density 1-5A / dm ²
A nickel layer was formed on the M surface of the electrolytic copper foil under conditions of time 1 to 15 seconds, and surface treatment was performed in this order of zinc / chromium and silane. Table 1 shows the amount of metal deposited on the copper foil surface.

Comparative Example 2
Nickel-P plating condition Nickel plating condition containing phosphorus
_{NiSO 4 · 6H 2 O 10~500g /} l
H ₃ BO ₃ 1-50 g / l
_{NaPH 2 O 2 · H 2 O} 0.1~30g / l
Current density 3A / dm ²
Bath temperature 30 ° C
A nickel-phosphorus alloy layer was formed on the M surface of the electrolytic copper foil under the condition of time 4 seconds, and surface treatment was performed in that order in the order of zinc / chromium and silane. Table 1 shows the amount of each metal deposited on the copper foil surface.

Comparative Example 3
Nickel-cobalt plating conditions
_{NiSO 4 · 6H 2 O 60~180g /} l
CoSO ₄ · 7H ₂ O 5 to 35 g / l
NaCL 15g / l
Temperature 20 ° C
Current density 1-5A / dm ²
A nickel-cobalt alloy layer was formed on the M surface of the electrolytic copper foil under conditions of time 1 to 15 seconds, and surface treatment was performed in this order in the order of zinc / chromium and silane. Table 1 shows the amount of each metal deposited on the copper foil surface.

Reference example 1
A nickel layer containing phosphorus is formed on the M surface of the electrolytic copper foil within the condition range of condition 3 for 10 seconds to form a nickel layer, and then plated for 40 seconds within the condition range of condition 5 to form molybdenum. -A cobalt layer was formed, and a rust preventive metal Zn · Cr was adhered thereon, and silane treatment was performed.
Table 1 shows the amount of each metal deposited on the copper foil surface. At this time, molybdenum was 93% or more based on the total amount of nickel-phosphorus and molybdenum-cobalt metal.

<Creation of sample for evaluation>
A polyimide resin is applied to the surface-treated copper foil prepared in each example, each comparative example, and reference example (thickness 50 μm), cured at a temperature of 300 ° C. in a nitrogen atmosphere, and a copper film for evaluation is prepared to give an evaluation sample. It was.

<Measurement of initial peel>
In accordance with the method specified in JISC6511 for each evaluation sample, the peel strength with a measurement sample width of 10 mm was measured. The measurement results are shown in Table 2.

<Heat resistance degradation test>
Each sample for evaluation was allowed to stand in the atmosphere at a temperature of 150 ° C. for 168 hours, and then the peel strength with a measurement sample width of 10 mm was measured according to the method specified in JISC6511. The measurement results are shown in Table 2.

<Etching evaluation>
Copper salt was used for the etching solution, copper was dissolved from each sample for evaluation, and the time required to visually confirm that no metal or the like was on the film was measured. The measurement results are shown in Table 2.

<Confirmation of acid resistance>
1mm wide tape is applied to the sample for evaluation to form a 1mm circuit, and then immersed in 50g / l sulfuric acid for 5 minutes to observe whether or not erosion has occurred at the joint between the film and the copper layer using a microscope. did.
In addition, the cross-sectional shape was confirmed by obtaining the cross-sectional observation result at a ratio when the theoretical area before etching was 100.

注１） 表内の金属組成（金属付着量）は、Zn Ｃｒ防錆処理以外の量である。








[Table 1] Metal composition in surface treatment layer of each example and comparative example

Note 1) The metal composition (metal adhesion amount) in the table is an amount other than the Zn Cr rust prevention treatment.

＜劣化率＞
劣化率（％）＝（（常態ピール）−（耐熱ピール））×１００／（常態ピール）
[Table 2] Evaluation results

<Deterioration rate>
Deterioration rate (%) = ((normal peel) − (heat-resistant peel)) × 100 / (normal peel)

As is clear from Table 2, in each example, the peel strength is 1 to 1.4, the deterioration rate of peel strength by heating is 7.5% or less, and the etching time is longer than that of the comparative example. In addition, the acid resistance was sufficient, and the area ratio after etching was 90% or more.
Compared to this example, in Comparative Example 1, which is only the first layer made of nickel, the deterioration rate was as large as 40%, and the acid resistance was not sufficient.
In Comparative Example 2 having only the first layer made of nickel-phosphorus, the deterioration rate was as large as 37%, the acid resistance was not sufficient, and the area ratio after etching was 90% or less.
In Comparative Example 3 having only the first layer made of nickel-cobalt, the deterioration rate was as large as 40%, there was no acid resistance, and the area ratio after etching was 90% or less.

In Reference Example 1, the second layer of molybdenum-cobalt is provided in the first layer made of nickel-phosphorus, but the etching time becomes longer because the composition ratio of molybdenum to the molybdenum alloy is as large as 93%, and the etching time becomes longer. Since the length becomes longer, the area ratio after etching becomes worse.
Molybdenum is a metal that is difficult to etch. Therefore, it may be necessary to adjust the ease of etching by using molybdenum as an alloy. In Reference Example 1 shown in Table 2, the peel strength and the deterioration rate are satisfied. However, the etching characteristics are not satisfactory. Therefore, an alloy containing a large amount of molybdenum is used for applications that require negligible etching characteristics and only peel strength is required. For applications that place importance on etching characteristics, the amount of molybdenum is set to the lowest peel strength as shown in Example 1. The molybdenum content is adjusted so as to improve the etching characteristics while keeping the range to a limit satisfactory.
As described above, in the present invention, when a metal is deposited with molybdenum alone, as in Example 1, the minimum deposition amount that satisfies the peel strength and the deterioration rate is not adversely affected. On the other hand, when the etching characteristics can be ignored, the proportion of molybdenum is increased so that the peel strength and deterioration rate are emphasized. As described above, even when a molybdenum alloy is adhered, since it takes an etching time if the adhesion amount is large, the blending amount is appropriately adjusted, and a blending amount satisfying both peel strength and etching characteristics is selected. .

As described above in detail, in the surface-treated copper foil of the present invention, a first layer made of nickel (or nickel alloy) is formed on at least one surface of the copper foil, and molybdenum (or molybdenum alloy) is formed on the first layer. ) Is formed, the bonding surface between the copper foil and the resin substrate is excellent in heat resistance and chemical resistance, and the adhesion to the resin substrate, particularly the polyimide film is improved. It has the effect of.
Therefore, the surface-treated copper foil of the present invention can be suitably used as a printed wiring board, a copper foil for COF and FPC.

Claims (6)

On at least one surface of the copper foil, nickel - cobalt alloy, or nickel - first layer of phosphorus alloy is formed, the surface treated copper foil second layer of molybdenum on said first layer on are formed The surface-treated copper foil is characterized in that the content of cobalt or phosphorus contained in the nickel-cobalt alloy or nickel-phosphorus alloy is 0.1 to 40% with respect to nickel. On at least one surface of the copper foil, nickel - cobalt alloy, or nickel - first layer of phosphorus alloy is formed of molybdenum in the first layer on the - cobalt alloy or molybdenum - second layer of chrome formed a surface treated copper foil that is, the nickel - cobalt alloy or a nickel - phosphorus alloy, and molybdenum - cobalt alloys or molybdenum - cobalt contained in the chrome, phosphorus, the content of chromium, nickel alloys and molybdenum alloys The surface-treated copper foil characterized by being 50% or less of the total amount. The molybdenum content of the second layer, the surface-treated copper foil according to claim 1 or 2, characterized in that a 0.002~0.5mg / dm ^2.   The surface-treated copper foil according to claim 2 or 3, wherein an amount of molybdenum contained in the molybdenum alloy forming the second layer is 3 to 75% of a surface metal adhesion amount.   The copper foil is an electrolytic copper foil, and is a surface-treated copper foil in which the first layer and the second layer are formed on the M surface of the electrolytic copper foil (the surface not in contact with the drum during electrolytic film formation), 5. The surface roughness of the M surface of the electrolytic copper foil is Rz: 1.5 [mu] m or less, Ra: 0.3 [mu] m or less, and a foil thickness of 5 to 35 [mu] m. The surface-treated copper foil in any one of.   The surface-treated copper foil according to any one of claims 1 to 5, wherein a cross-sectional crystal of the copper foil is a granular crystal.