JPWO2018181061A1 - Surface-treated copper foil and copper-clad laminate using the same - Google Patents

Abstract

  Provided is a surface-treated copper foil having fine line spacing and line width, excellent etching properties, laser processability and thin foil handling properties, few pinholes and high tensile strength. Tensile strength is 400 to 700 MPa, tensile strength after heating at 220 ° C. for 2 hours is 300 MPa or more, foil thickness is 7 μm or less, single-sided development area ratio (Sdr) is 25 to 120%, and Surface-treated copper foil with 20 or less pinholes with a diameter of 30 μm or more.

Description

  The present invention relates to a surface-treated copper foil excellent in laser processability suitable for a printed wiring board having a high-density wiring circuit (fine pattern), and a copper-clad laminate using the same.

  A printed wiring board is manufactured by placing a thin copper foil for forming a surface circuit on the surface of an electrically insulating substrate made of glass epoxy resin or polyimide resin, and then heating and pressing to produce a copper-clad laminate. Next, through-hole drilling and through-hole plating are sequentially performed on the copper-clad laminate, and then the copper foil of the copper-clad laminate is etched to provide a desired line width and a desired line pitch. A wiring pattern is formed. Finally, in order to expose the solder resist coating, exposure, through-hole plating, or plating of the connection part of the electronic component, removal of the uncured solder resist or other finishing treatment is performed with caustic soda.

  The copper foil used at this time is generally an electrolytic copper foil obtained by peeling the copper foil 101 deposited on the drum 102 using the electrolytic deposition apparatus shown in FIG. The field deposition start surface (shiny surface, hereinafter referred to as “S surface”) peeled off from the drum 102 is relatively smooth, and the opposite surface of the electrolytic deposition end surface (matt surface; hereinafter referred to as “M surface”) is general. Has irregularities. Usually, the adhesion to the substrate resin is improved by roughening the roughening treatment on the M surface.

  Recently, an adhesive resin such as an epoxy resin is pasted on the roughened surface of the copper foil in advance, and a resin-coated copper foil is formed by using the adhesive resin as an insulating resin layer in a semi-cured state (B stage). A printed wiring board, particularly a build-up wiring board, is manufactured by thermocompression bonding the insulating resin layer side to a substrate (insulating substrate). In the build-up wiring board, there is a demand for highly integrated various electronic components. Correspondingly, the wiring pattern is also required to have a high density, and a wiring pattern having a fine line width and a pitch between lines, so-called fine wiring. A printed wiring board having a pattern has been demanded. For example, multilayer boards used for servers, routers, communication base stations, in-vehicle boards, etc. and smartphone multilayer boards require printed wiring boards with high-density ultrafine wiring with a line width and line spacing of around 15 μm. ing.

  With the increase in density and miniaturization of such wiring boards, it is becoming difficult to form a fine circuit by a subtractive method, and a semi-additive method (MSAP method) is being used instead. In the MSAP method, an ultrathin copper foil is formed as a power feeding layer on a resin layer, and then pattern copper plating is applied on the ultrathin copper foil. Next, the ultrathin copper foil is removed by flash etching to form a desired wiring.

Usually, a thin copper foil with a carrier is used in the MSAP method. In the thin copper foil with a carrier, a release layer and a thin copper foil are formed in this order on one side of a copper foil (carrier copper foil) as a carrier, and the surface of the thin copper foil is a roughened surface. Then, after superposing the roughened surface on the resin substrate, the whole is thermocompression bonded, then the carrier copper foil is peeled and removed, and the bonding side of the thin copper foil with the carrier copper foil is exposed, and there It is used in the form of forming a predetermined wiring pattern.
A hole called a via is opened for interlayer connection in the build-up wiring board, and this hole is often formed by laser light irradiation. In the MSAP method, a method called direct laser processing is used in which holes are formed in the copper foil and the resin at a stretch by directly irradiating the copper foil with laser light.

  The copper foil with carrier used in the MSAP method is usually M-sided on the resin base, and the laser-treated surface (S-surface) is smooth and not sufficiently laser-absorbing. As described above, browning (etching roughening) is required. Therefore, Patent Document 1 proposes a copper foil having good laser processability by having a laser absorption layer made of chromium, cobalt, nickel, iron or the like on the laser processed surface in order to improve the laser processability of the S surface. Has been. However, the thin copper foil in the carrier-attached copper foil is produced by an ordinary copper sulfate bath plating bath, and there is a problem that pinholes frequently occur.

  Patent Document 2 proposes a copper foil in which pinholes are suppressed by uniformly forming nickel and zinc chromate layers as intermediate layers. However, since the intermediate layer (peeling layer) is formed on the glossy surface of the carrier foil, the intermediate layer to which the laser hits after peeling the carrier foil is smooth and hardly absorbs laser light, and the laser processability is poor. Moreover, since it is a copper foil with a carrier, there is a problem that it takes time to peel off the copper foil with a carrier and the handling property is poor.

  In patent document 3, the copper foil with a carrier which improved the laser workability and the etching property by suppressing the variation in the roughness of the intermediate layer side of the thin copper foil is proposed. However, the thin copper foil in the carrier-attached copper foil is produced by an ordinary copper sulfate bath plating bath, and there is a problem that pinholes frequently occur.

JP 2013-75443 A International Publication No. 2015/030256 JP 2014-208480 A

The MSAP method uses a copper foil with a carrier, but this copper foil with a carrier has the following problems.
・ Many pinholes are decreasing the manufacturing yield.
-The intermediate layer that the laser hits after peeling the carrier foil is smooth and difficult to absorb the laser beam, and the laser processability is poor. Therefore, a browning process (etching roughening process) is required as a pre-process for laser processing.
・ The manufacturing process has been increased due to the labor of the carrier foil peeling process.
Because of these problems, new materials that can replace the copper foil with carrier have been demanded. For these problems, the present invention has a high tensile strength after normal heating and heating, and it can be applied to the MSAP method without occurrence of wrinkles even with a thin foil without a carrier foil. Laser workability (direct laser processing) Another object of the present invention is to provide a surface-treated copper foil that is excellent in etching property and thin foil handling property and suitable for high-density wiring circuits with few pinholes.

The inventors of the present invention have intensively studied and found that a roughened surface having “Sdr of 25 to 120%” is suitable for direct laser processing. Further, the surface-treated copper foil of the present invention is a surface-treated copper foil having a tensile strength of 400 MPa to 700 MPa in a normal state, a tensile strength measured at room temperature after heating at 220 ° C. for 2 hours, and a foil thickness of 7 μm or less. In addition, the development area ratio (Sdr) of at least one surface is 25 to 120%, and the number of pinholes having a diameter of 30 μm or more is 20 pieces / m ² or less. It has been found that it is excellent in direct laser processing) and thin foil handling properties, and has few pinholes and is suitable for high-density wiring circuits. Based on this finding, the present invention has been completed.

  In the present invention, the normal state means that the surface-treated copper foil is kept at room temperature (= about 25 ° C.) without receiving a thermal history such as heat treatment. The tensile strength in the normal state can be measured by IPC-TM-650 at room temperature. The tensile strength after heating can be measured in the same manner as the normal tensile strength at room temperature after heating the surface-treated copper foil to 220 ° C. and holding it for 2 hours, followed by natural cooling to room temperature.

  When the tensile strength in a normal state is 400 to 700 MPa, the hand rigging property and the etching property are good. When the tensile strength in a normal state is less than 400 MPa, wrinkles are generated when a thin foil sheet product is conveyed, resulting in poor handling, and when it is more than 700 MPa, the foil is likely to break during precipitation production with a drum and is unsuitable for production. When the tensile strength measured at room temperature after heating is 300 MPa or more, the crystal grains are fine and the etching property is good even after heating in the substrate lamination step. Similarly, when the tensile strength after heating is 300 MPa or less, the crystal grains become large and are difficult to dissolve by etching.

  The foil thickness of the surface-treated copper foil is 7 μm or less, and may be 6 μm or less. When the foil thickness of the surface-treated copper foil exceeds 7 μm, the degree of opening by a low energy laser tends to be deteriorated. When the foil thickness of the surface-treated copper foil is 7 μm or less, particularly 6 μm or less, laser workability, particularly workability in laser irradiation with a low energy of about 8 W tends to be improved.

  In the present invention, the foil thickness is a copper foil produced by electrolytic deposition, if necessary, formation of a laser absorption layer, formation of a roughening treatment layer, formation of a Ni layer, formation of a zinc layer, chromate treatment, It means the film thickness before the laser processing after the surface treatment such as the formation of the silane coupling device. The foil thickness can be measured as a mass thickness by an electronic balance.

  In the present invention, by setting the development area ratio (Sdr) of at least one surface to 25 to 120%, direct laser workability when this surface and the laser irradiation surface are used can be improved.

  The developed area ratio (Sdr) means the ratio of the surface area added by the surface properties based on the ideal surface having the size of the measurement region, and is defined by the following equation.

Here, x and y in the formula are plane coordinates, and z is a coordinate in the height direction. z (x, y) indicates the coordinates of a certain point, and by differentiating this, the slope at that coordinate point is obtained. A is the plane area of the measurement region.
The development area ratio (Sdr) can be obtained by measuring and evaluating the unevenness of the copper foil surface with a three-dimensional white interference microscope, scanning electron microscope (SEM), electron beam three-dimensional roughness analyzer, etc. it can. In general, Sdr tends to increase as the spatial complexity of the surface texture increases, regardless of changes in the surface roughness Sa.

Here, the principle of direct laser processing will be described. When the reflectance on the copper foil surface is r, the absorptance is μ, and the transmittance is τ, the following equation holds.
r + μ + τ = 1
In direct laser processing, a laser beam such that τ = 0 is selected for copper foil, and CO2 gas laser is common, and the above equation is r + μ = 1. When the intensity of the laser beam is absorbed in a uniform distribution, the temperature distribution on the beam center axis (Z axis) is expressed by the following equation, where the beam radius is a.

Here, x and y in the formula are plane coordinates, and z is a coordinate in the height direction. P is the absorbed laser power [J / s], x is the thermal diffusivity = K / ρ · C [cm ² / S], and K is the thermal conductivity [J / cm · s · K], ρ is the density [g / cm3], C is the specific heat [J / g · K], t is the laser irradiation time [s], and a is the beam radius [cm].
The temperature rises with increasing time but saturates for a certain time. The temperature at that time is as follows.

  It can be seen that the temperature increases as the energy of the laser light absorbed on the copper foil surface increases as in the above equation. This is because atomic vibration is amplified and converted into heat by the energy of the absorbed laser beam. In direct laser processing, this thermal energy is used to melt and drill the copper foil at the laser irradiated location. In order to increase the accuracy and efficiency of direct laser processing, it is necessary to reduce the reflectance on the copper foil surface or increase the absorption rate, as can be seen from the above formula.

  In the conventional MSAP method, since the absorption rate of the copper surface after peeling the carrier foil is low, it is compatible with direct laser processing by roughening the surface by browning and increasing the absorption rate, but the browning process is laborious Therefore, it is a problem from the viewpoint of manufacturing cost. Therefore, as a result of intensive research, by setting the development area ratio (Sdr) of at least one surface of the copper foil to 25 to 120%, it is possible to improve the direct laser workability when this surface is used as the laser irradiation surface. I found out that I can do it. When the surface is such that the Sdr is 25 to 120%, a highly complex uneven shape is formed at 1 μm or less. When a copper foil having such a shape is irradiated with laser, diffused reflection increases and the absorption rate of laser light increases. In addition, the re-surface layer of the copper foil is activated and the oxide film is formed due to the highly complex surface irregularity shape, and the reflectivity decreases, and the thermal conductivity decreases due to the increase in the oxide film layer and the surface area. However, it is considered that direct laser processability has increased due to an increase in the temperature of the laser beam irradiation part. When the Sdr of the laser machined surface is less than 25%, the absorbency of the laser tends to be poor because the reflectivity is high and the laser light absorptivity is poor. On the other hand, when Sdr is larger than 120%, the problem that the melted copper easily fills the hole again tends to occur and the laser processability deteriorates.

In addition, when the copper foil is made thin, it is known that the performance of the circuit board is deteriorated when a pinhole is generated. In the present invention, the copper having a pinhole of 30 μm or more in diameter is 20 pieces / m ² or less. A foil is obtained, and the performance degradation of the circuit board can be suppressed.

The number of pinholes is determined by cutting the copper foil into an appropriate size, for example, 200 mm × 200 mm, marking the pinholes by, for example, a light transmission method, checking the diameter with an optical microscope, and counting holes of 30 μm or more. Unit area based on the number of the resulting pinhole (m ²⁾ Number of pinholes per an (pieces / m @ 2) can be calculated.

  ADVANTAGE OF THE INVENTION According to this invention, the copper foil which is excellent in etching property, laser workability, thin foil handling property, and pinhole resistance can be provided. In addition, since the tensile strength after normal and heating is high, it is possible to provide a surface-treated copper foil that can be applied to the MSAP method without using a carrier copper foil.

It is a figure which shows the precipitation apparatus of the conventional electrolytic copper foil. It is a figure which shows the deposition apparatus of the electrolytic copper foil which has a cathode reduction process. It is a figure which shows the relationship between the laser numerical aperture and pinhole number in an Example and a comparative example. It is a figure which shows the relationship between the tensile strength of the state in an Example and a comparative example, and the number of wrinkle defects.

The surface-treated copper foil of the present invention has a development area ratio (Sdr) of 25 to 120%, but if the development area ratio (Sdr) is 30 to 80%, the laser processability tends to be further improved. Further, even when the thickness of the surface-treated copper foil is 7 μm or less, particularly 6 μm or less, the development area ratio (Sdr) is 30 to 80%, and the number of pinholes having a diameter of 30 μm or more is 10 / m ² or less. It is preferable. When the number of pinholes having a diameter of 30 μm or more exceeds 10 / m ² , the performance when applied to a circuit board tends to be lowered.

  The surface-treated copper foil of the present invention preferably has a laser-processed surface of Yxy color system, Y of 25.0 to 65.5%, x of 0.30 to 0.48, and y of 0.28 to 0.41. After the laser-processed surface of the surface-treated copper foil satisfies the above development area ratio (Sdr), the processed surface is Yxy color system, Y is 25.0 to 65.5%, x is 0.30 to 0.48, and y is 0.28 to When it is in the range of 0.41, the laser absorptivity is further improved and the laser processability is very good.

  The Yxy color system can be measured using a device such as a color meter in accordance with JIS Z 8722, for example.

  As mentioned above, the copper foil used in the MSAP method has an M-surface that is affixed to the resin base, and the laser-processed surface is smooth and not sufficiently laser-absorbing. A process (etching roughening process) is performed. In the present invention, it is possible to improve laser processability without performing browning.

Below, the conditions and method for manufacturing the surface-treated copper foil of this invention are demonstrated.
(1) Manufacture of electrolytic copper foil The copper foil in the present invention is, for example, an insoluble anode made of titanium coated with a platinum group element or an oxide element thereof using a sulfuric acid-copper sulfate aqueous solution as an electrolytic solution, and opposed to the anode. The electrolytic solution is supplied between the titanium cathode drum and the cathode drum, and copper is deposited on the surface of the cathode drum by applying a direct current between both electrodes while rotating the cathode drum at a constant speed. The produced copper is peeled off from the surface of the cathode drum and is continuously wound up.

  In the present invention, it is preferable to make the electrolytic copper foil so that the deposition potential of copper in the cathode drum surface is uniform and uniform. For this purpose, for example, a method of forming a foil in a state where an oxide film does not exist on the surface of the titanium drum can be mentioned. As an example, a cathode reduction process may be employed. As shown in FIG. 1, in a conventional electrolytic copper foil manufacturing apparatus, an electrolytic drum 102 serving as a cathode is polished by a buff 103 to remove an oxide film generated on the drum surface. On the other hand, in the cathode reduction step, for example, instead of the buff 103 of the electrolytic copper foil deposition apparatus of FIG. 1, the electrolytic solution (dilute sulfuric acid) of the cathode reduction apparatus 105 is used as shown in FIG. ) 106 to remove the oxide film. By removing the oxide film by the drum 102 and the cathode reduction device 105, it is expected that initial precipitation of copper uniformly occurs on the surface of the titanium drum and pinholes are reduced. In the manufacture of copper foil using the conventional titanium drum shown in FIG. 1, the film thickness of the titanium oxide film on the titanium drum surface is uneven, so that the copper deposition potential varies within the drum surface. Hall was easy to occur. Pinholes can be reduced by employing a cathode reduction process and increasing the cathode reduction current density. This is because it is considered that the reduction of the titanium oxide further proceeds due to the increase in the cathode reduction current density, the distribution of the copper deposition potential on the surface of the titanium drum is eliminated, and pinholes can be suppressed.

  In the production of the electrolytic copper foil, ethylenethiourea, polyethylene glycol, tetramethylthiourea, polyacrylamide or the like may be added as an additive to the electrolytic solution. By increasing the addition amount of ethylenethiourea and tetramethylthiourea, the tensile strength in the normal state and the tensile strength after heating can be increased. When the tensile strength in the normal state is 400 to 700 MPa, the handling property and the etching property are good. When the tensile strength in the normal state is less than 400 MPa, the handleability is poor, and when it is more than 700 MPa, the foil is likely to break and is unsuitable for production. In addition, when the tensile strength measured at room temperature after heating at 220 ° C. for 2 hours is 300 MPa or more, the crystal grains are fine and the etching property is good even after heating by laminating the substrates. Similarly, when the tensile strength after heating is 300 MPa or less, the crystal grains become large and are difficult to dissolve by etching, so that the etching property is deteriorated.

(2) Copper foil surface treatment <Laser absorption layer forming treatment>
Next, surface treatment for forming a laser absorption layer is performed on the copper foil obtained above. In the present invention, an uneven plating layer is formed on one surface of the copper foil by a pulse current. This surface becomes a laser processed surface when a circuit is produced by the MSAP method using copper foil. The surface on which the laser absorption layer is formed may be the deposition start surface (S surface) or the deposition end surface (M surface) in the electrolytic copper foil manufacturing process. In general, the bonding surface (roughening surface) with the resin substrate is often the M surface and the laser processed surface is the S surface. However, in the present invention, the S surface is roughened with the resin substrate. The processed surface may be a M-plane. That is, the roughening process layer may be formed in the electrolytic deposition start surface (S surface) in the manufacture process of electrolytic copper foil.

  In the present invention, by providing an appropriate surface area so that the developed area ratio Sdr of the M surface or S surface, which is the laser processing surface, is 25 to 120%, direct laser processing can be performed without browning. I found. Moreover, an etching factor can also be improved by forming a roughening process layer in the electrolytic deposition start surface in the manufacture process of electrolytic copper foil.

  As a plating bath composition for forming the laser absorption layer, copper sulfate pentahydrate, sulfuric acid, hydroxyethylene cellulose (HEC), polyethylene glycol (PEG), thiourea and the like can be added. By adding positive pulse currents having different current values in two stages, the additive acting in accordance with the corresponding two-stage deposition potential changes, and a complex uneven shape can be formed. As a result, a deposition surface with excellent laser absorption can be obtained. Specifically, in a stepped pulse current where one step current value (Ion1)> two step current value (Ion2), one step current value (Ion1) or one step time (ton1) is increased. As a result, the S-dr of the M-plane tends to increase. By applying such a two-stage pulse current at a constant time interval (toff), a surface shape having an Sdr value with good laser processability can be obtained.

  Laser workability is improved when Sdr is in the range of 25 to 120%. Such a foil has a fine uneven shape of about 2 μm or less on the surface of the surface-treated copper foil, and the laser light absorbability is increased. If the Sdr is less than 25%, the laser beam is not absorbed well and the laser processability is poor. If Sdr is greater than 120%, the absorption rate of light at the wavelength of the CO2 laser is lowered and laser processability is lowered. Further, when the time interval (toff) of the pulse current is increased, Y decreases in the Yxy color system. When Sdr is in the range of 25 to 120% and Y is in the range of 15.0 to 85.0% in the Yxy color system, laser processability is improved. If Y is less than 15% or greater than 85%, the laser processability tends to decrease. As Sdr increases, the laser numerical aperture tends to increase, and as the Y value decreases, the laser numerical aperture tends to increase. The laser-irradiated surface has Sdr in the range of 25 to 120%, and in the Yxy color system, Y is 25.0 to 65.5%, x is 0.30 to 0.48%, and y is 0.28 to 0.41%. .

<Formation of roughening treatment layer>
On the surface opposite to the laser processed surface of the copper foil, a roughened layer having a fine uneven surface is formed by electrodeposition of fine copper particles. The roughening layer is formed by electroplating, but it is preferable to add a chelating agent to the plating bath, and the concentration of the chelating agent is suitably 0.1 to 5 g / L. Examples of chelating agents include DL-malic acid, sodium EDTA solution, sodium gluconate, and diethylenetriaminepentaacetic acid pentasodium (DTPA).

Copper sulfate, sulfuric acid and molybdenum may be added to the electrolytic bath. Etching properties can be improved by adding molybdenum. Usually, the copper concentration is 13 to 72 g / L, the sulfuric acid concentration is 26 to 133 g / L, the liquid temperature is 18 to 67 ° C., the current density is 3 to 67 A / dm ² , and the treatment time is 1 second to 1 minute 55 seconds. Electrodeposition is performed at

<Formation of nickel layer, zinc layer, chromate treatment layer>
In the present invention, it is preferable to further form a nickel layer and a zinc layer in this order on the roughened surface. This zinc layer increases the bonding strength with the substrate by preventing deterioration of the substrate resin and surface oxidation of the thin copper foil due to the reaction with the thin copper foil substrate resin when the thin copper foil and the resin substrate are thermocompression bonded. Work. In addition, the nickel layer is zinc for preventing the zinc of the zinc layer from thermally diffusing to the copper foil (electrolytic copper plating layer) side at the time of thermocompression bonding to the resin substrate, so that the above functions of the zinc layer are effectively exhibited. Serves as an underlayer for the layer.
In addition, these nickel layers and zinc layers can be formed by applying a known electrolytic plating method or electroless plating method. The nickel layer may be formed of pure nickel or a phosphorus-containing nickel alloy.

Further, it is preferable to further perform chromate treatment on the surface of the zinc layer because an antioxidant layer is formed on the surface. As the chromate treatment to be applied, a known method may be used, and examples thereof include a method disclosed in JP-A-60-86894. By attaching a chromium oxide of about 0.01 to 0.3 mg / dm ² and its hydrate in terms of the amount of chromium, an excellent rust preventive ability can be imparted to the copper foil.

<Silane treatment>
Further, when a surface treatment using a silane coupling agent is further performed on the chromate-treated surface, a functional group having a strong affinity for the adhesive is imparted to the copper foil surface (the surface on the side bonded to the substrate). Therefore, the bonding strength between the copper foil and the substrate is further improved, and the rust prevention and moisture absorption heat resistance of the copper foil are further improved.

   Silane coupling agents include vinyl silane, epoxy silane, styryl silane, methacryloxy silane, acryloxy silane, amino silane, ureido silane, chloropropyl silane, mercapto silane, sulfide silane, isocyanate silane Examples include silane. These silane coupling agents are usually made into 0.001 to 5% aqueous solution, which is applied to the surface of the copper foil and then dried by heating as it is. In addition, it can replace with a silane coupling agent, and the same effect can be acquired even if it uses coupling agents, such as a titanate type | system | group and a zirconate type | system | group.

(3) Manufacture of copper-clad laminate First, a copper foil surface (roughening layer surface) of a thin copper foil is placed on the surface of an electrically insulating substrate made of glass epoxy resin or polyimide resin, and heated and heated. A copper-clad laminate with or without a carrier is produced by pressing. Since the surface-treated copper foil of the present invention has a high tensile strength after normal and heating, it can sufficiently cope even without a carrier. Next, the surface of the copper-clad laminate is irradiated with a CO2 gas laser to make a hole. That is, a CO2 gas laser is irradiated from the surface of the surface-treated copper foil on which the laser absorption layer is formed, to perform a drilling process that penetrates the surface-treated copper foil and the resin substrate.

Hereinafter, the present invention will be described in detail by way of examples.
(1) Production of Copper Foil and Formation of Laser Absorbing Layer Examples 1 to 21 and Examples 1 to 21 by the cathode reduction step of the electrolytic solution, current density, and bath temperature shown in Table 1 and the electrolytic deposition step under the electrolytic conditions shown in Table 2 The electrolytic copper foil of Comparative Examples 1-9 was manufactured. A laser absorption layer was formed by electrolytic plating treatment of these electrolytic copper foils in a plating bath having a composition shown in Table 3, a treatment surface, and electrolytic conditions (pulse width of pulse voltage, current density, time, bath temperature). In Example 22, a laser absorption layer was formed by alternating current, and in Example 23, a laser absorption layer was formed by MEC etch bond CZ-8000 treatment. In the electrolysis conditions in Table 3, Ion1 represents the first stage pulse current density, Ion2 represents the second stage pulse current density, and ton1 represents the first stage pulse current application time. ton2 represents the pulse current application time at the second stage, and toff represents the time when the current between the pulse current at the second stage and the pulse current at the first stage is zero. The surface where the laser absorbing layer is formed is the surface opposite to the roughened surface shown in Table 4. In Examples 1 to 19, 22 to 23 and Comparative Examples 4 and 6 to 8, the laser absorbing layer is formed on the M surface. Was formed (roughening treatment was performed on the S surface), and in Examples 20 and 21 and Comparative Example 9, a laser absorption layer was formed on the S surface (roughening treatment was performed on the M surface). Comparative Examples 1-3 and 5 did not form a laser absorption layer.

(2) Roughening treatment Next, a roughening treatment layer having a fine concavo-convex surface was formed on the surface opposite to the laser absorption layer (roughening treatment surface shown in Table 4) by electrodeposition of roughening particles. In all Examples and Comparative Examples, the roughening plating process was performed as described below to form a roughening treatment layer.
(Roughening plating treatment)
Copper sulfate: 13-72 g / L as copper concentration
Sulfuric acid concentration: 26-133 g / L
DL-malic acid: 0.1-5.0 g / L
Liquid temperature: 18-67 degreeC
Current density: 3 to 67 A / dm ²
Processing time: 1 second-1 minute 55 seconds

(3) Formation of Ni-containing foundation layer For all Examples 1 to 23 and Comparative Examples 1 to 9, after the formation of the roughening layer, electrolysis was performed on the roughening layer under the Ni plating conditions shown below. By plating, a base layer (Ni adhesion amount 0.06 mg / dm ² ) was formed.
<Ni plating conditions>
Nickel sulfate: 5.0 g / L as nickel metal
Ammonium persulfate 40.0 g / L
Boric acid 28.5g / L
Current density 1.5 A / dm ²
pH 3.8
Temperature 28.5 ° C
Time 1 second-2 minutes

(4) Formation of heat-resistant layer containing Zn For all of Examples 1 to 23 and Comparative Examples 1 to 9, after the formation of the underlayer, electrolytic plating is performed on the underlayer under the following Zn plating conditions. Thus, a heat-resistant treatment layer (Zn deposition amount: 0.05 mg / dm ² ) was formed.
<Zn plating conditions>
Zinc sulfate heptahydrate 1-30g / L
Sodium hydroxide 10-300g / L
Current density 0.1-10 A / dm ²
Temperature 5-60 ° C
Time 1 second-2 minutes

(5) Formation of anticorrosion treatment layer containing Cr For all Examples 1 to 23 and Comparative Examples 1 to 9, after the formation of the above heat treatment layer, on this heat treatment layer, the following chromium plating treatment conditions The antirust process layer (Cr adhesion amount: 0.02 mg / dm < ² >) was formed by processing by.
<Chrome plating conditions>
(Chromium plating bath)
Chromic anhydride CrO3 2.5g / L
pH 2.5
Current density 0.5 A / dm ²
Temperature 15-45 ° C
Time 1 second-2 minutes

(6) Formation of Silane Coupling Agent Layer For all Examples 1 to 23 and Comparative Examples 1 to 9, after the formation of the antirust treatment layer, methanol or ethanol was added to the silane coupling agent aqueous solution on the antirust treatment layer. And a treatment liquid adjusted to a predetermined pH was applied. Thereafter, the silane coupling agent layer was formed by holding for a predetermined time and drying with warm air.

(7) Evaluation method <foil thickness>
The thickness of the surface-treated copper foils of all Examples 1 to 23 and Comparative Examples 1 to 9 obtained by the above treatments (1) to (5) was measured as a mass thickness using an electronic balance. The results are shown in Table 1.

<Tensile strength>
All the surface-treated copper foils of Examples 1 to 23 and Comparative Examples 1 to 9 obtained by the above treatments (1) to (5) were cut into a size of 12.7 × 130 mm mm, and Instron's 1122 at room temperature. The tensile strength of the copper foil in a normal state was measured with a mold tensile tester testing apparatus. Moreover, after heating the copper foil cut out to 12.7 * 130 mmmm at 220 degreeC for 2 hours, and naturally cooling to normal temperature, the tensile strength after a heating was measured similarly. The measurement was based on IPC-TM-650. The results are shown in Table 4.

<Development area ratio>
About all the surface-treated copper foils of Examples 1 to 23 and Comparative Examples 1 to 9 obtained by the above treatments (1) to (5), the surface shape was measured using WykoContourGT-K of BRUKER, and the shape analysis was performed. And the development area ratio (Sdr) was determined. The shape analysis uses a high resolution CCD camera with a VSI measurement method, the light source is white light, the measurement magnification is 10 times, the measurement range is 477 μm × 357.8 μm, the lateral sampling is 0.38 μm, the speed is 1, the backscan is 5 μm, and the length is The processing was performed under the conditions of 5 μm and Threshold of 5%, and the data processing was performed after the filtering of TermsRemoval. The results are shown in Table 4.

<Yxy color system>
In the Yxy color system of the copper foils of Examples 1 to 23 and Comparative Examples 1 to 9 obtained by the above treatments (1) to (5), Y, x, and z are color meters SM-T45 (Suga Test Machine) Co., Ltd.), 45 ° illumination 0 ° light reception, light source C light 2 degree field of view (halogen lamp) can be measured. The results are shown in Table 4.

<Pinhole>
All surface treated copper foils of Examples 1 to 23 and Comparative Examples 1 to 9 obtained by the above treatments (1) to (5) are cut into a size of 200 mm × 200 mm, and pinholes are marked by a light transmission method. did. About five 200mm × 200mm size surface-treated copper foils (total 0.2m ² ), the diameter was confirmed with an optical microscope, and holes of 30 μm or more were counted as pinholes. Pinholes observed with an optical microscope can be either round or irregular, but the major diameter of each pinhole (the distance between the two most distant points on the outer periphery of the pinhole) was measured as the diameter. Table 4 shows the results of calculating the number of pinholes per unit area (m ² ) (pieces / m ² ) based on the number of pinholes obtained.

<Etching factor>
Next, a dry resist film was used for the surface-treated copper foils of Examples 1 to 23 and Comparative Examples 1 to 9 obtained by the above treatments (1) to (6), and L & S = 100 μm / 200 μm by dry etching. A resist pattern having a line / interval was formed. After etching the wiring pattern using copper chloride and hydrochloric acid as the etching solution, the etching factor was measured. The etching factor (Ef) is a value expressed by the following equation, where H is the thickness of the surface-treated copper foil, B is the bottom width of the formed wiring pattern, and T is the top width of the formed wiring pattern. Say.
Ef = 2H / (BT)

  If the etching factor is small, the verticality of the sidewalls in the wiring pattern is lost, and there is a risk that the wiring pattern may be disconnected in the case of a fine wiring pattern having a narrow line width. In this example, the bottom width and the top width were measured with a microscope and the etching factor was calculated with respect to the pattern when the just etch (resist end portion and bottom of the copper foil pattern were aligned) position. The results are shown in Table 4.

<Laser numerical aperture>
All the surface treated copper foils of Examples 1 to 23 and Comparative Examples 1 to 9 obtained by the above treatment were heated and pressure bonded to both sides of the substrate FR4 to produce CCL (copper clad laminate). Next, 100 holes were drilled with a CO2 laser drilling machine, and the number of openings was counted. Table 4 shows the number of apertures formed by irradiation for 10 msec for each irradiation time of 50 W and 8 W. Even in the case of 8 W where the irradiation energy is low, those having a small decrease in numerical aperture can be evaluated as having high laser processability.

<Handling: Wrinkle defect count>
All the surface treated copper foils of Examples 1 to 23 and Comparative Examples 1 to 9 obtained by the above treatments (1) to (5) were cut into a size of 200 mm × 200 mm, and the surface treated copper foil and the substrate FR4 were Heating and pressure bonding at 170 ° C and 1.5 MPa (pressure) for 1 hour to produce 30 substrates, visually check for wrinkles, and count the wrinkled substrate as one wrinkle defect Table 4 shows the number of wrinkle defects. This evaluated the handleability of the surface-treated copper foil.

  As can be seen from Table 4, Examples 1 to 23 all have a tensile strength of 400 to 700 MPa, a tensile strength after heating for 2 hours at 220 ° C. of 300 MPa or more, a foil thickness of 7 μm or less, and a laser irradiated surface. Development area ratio (Sdr) of 25 to 120%, as shown in the evaluation results, the number of pinholes is 20 or less, Ef is 2.0 or more, laser numerical aperture at 8 W is 90 or more, wrinkles It can be seen that the number of defects is 3 or less, there are few pinholes, laser workability is excellent, and handling properties are also excellent.

  In contrast, Comparative Examples 1 to 9 have a tensile strength of 400 to 700 MPa and a tensile strength after heating at 220 ° C. for 2 hours of 300 MPa or more, but Comparative Examples 2, 3, 5 to 7, and 9 Since the development area ratio (Sdr) of the laser irradiation surface does not satisfy 25 to 120%, the laser numerical aperture at 8 W is less than 90, indicating that the laser apertureability is not good. Further, in Comparative Examples 1 and 4, the occurrence of pinholes exceeds 20 depending on the manufacturing conditions of the surface-treated copper foil, and it can be seen that Comparative Example 8 has poor foil opening because the foil thickness is 9 μm.

  Based on the above evaluation results, for the surface treated copper foils of Examples 1 to 21 and Comparative Examples 1 to 9, the relationship between the numerical aperture and the number of pinholes when the irradiation energy is 8 W is shown in the graph of FIG. It was. As can be clearly seen from FIG. 3, the surface-treated copper foil of the example has a large number of apertures and less pinholes and is excellent in laser processability, whereas the surface-treated copper foil of the comparative example has an opening. It can be seen that the number is small or the number of pinholes is large and the laser processability is poor.

  Moreover, based on said evaluation result, about the surface treatment copper foil of Examples 1-21 and Comparative Examples 1-9, the relationship between the tensile strength in a normal state and the generation | occurrence | production number of pinholes was shown on the graph of FIG. As can be clearly seen from FIG. 3, the surface-treated copper foil of the example has a large number of apertures and less pinholes and is excellent in laser processability, whereas the surface-treated copper foil of the comparative example has an opening. It can be seen that the number is small or the number of pinholes is large and the laser processability is poor.

  According to the present invention, it is possible to provide a high surface-treated copper foil having high tensile strength, fine line spacing and line width, excellent etching properties, laser processability and thin foil handling properties, and few pinholes. Yes, it has high industrial applicability.

101 Deposited Copper Foil 102 Drum 103 Buffing Device 105 Cathode Reduction Device 106 Electrolyte

  The present invention relates to a surface-treated copper foil excellent in laser processability suitable for a printed wiring board having a high-density wiring circuit (fine pattern), and a copper-clad laminate using the same.

  A printed wiring board is manufactured by placing a thin copper foil for forming a surface circuit on the surface of an electrically insulating substrate made of glass epoxy resin or polyimide resin, and then heating and pressing to produce a copper-clad laminate. Next, through-hole drilling and through-hole plating are sequentially performed on the copper-clad laminate, and then the copper foil of the copper-clad laminate is etched to provide a desired line width and a desired line pitch. A wiring pattern is formed. Finally, in order to expose the solder resist coating, exposure, through-hole plating, or plating of the connection part of the electronic component, removal of the uncured solder resist or other finishing treatment is performed with caustic soda.

The copper foil used at this time is generally an electrolytic copper foil obtained by peeling the copper foil 101 deposited on the drum 102 using the electrolytic deposition apparatus shown in FIG. Exfoliated electrolytic deposition starting surface from the drum 102 (shiny surface. Hereinafter, the S surface) is relatively smooth, electrolytic deposition termination surface which is opposite the surface (matte surface. Hereinafter referred to M-plane) is generally In particular, it has irregularities. Usually by a roughening treatment on the M plane, thereby improving the adhesion to the substrate resin.

  Recently, an adhesive resin such as an epoxy resin is pasted on the roughened surface of the copper foil in advance, and a resin-coated copper foil is formed by using the adhesive resin as an insulating resin layer in a semi-cured state (B stage). A printed wiring board, particularly a build-up wiring board, is manufactured by thermocompression bonding the insulating resin layer side to a substrate (insulating substrate). In the build-up wiring board, there is a demand for highly integrated various electronic components. Correspondingly, the wiring pattern is also required to have a high density, and a wiring pattern having a fine line width and a pitch between lines, so-called fine wiring. A printed wiring board having a pattern has been demanded. For example, multilayer boards used for servers, routers, communication base stations, in-vehicle boards, etc. and smartphone multilayer boards require printed wiring boards with high-density ultrafine wiring with a line width and line spacing of around 15 μm. ing.

  With the increase in density and miniaturization of such wiring boards, it is becoming difficult to form a fine circuit by a subtractive method, and a semi-additive method (MSAP method) is being used instead. In the MSAP method, an ultrathin copper foil is formed as a power feeding layer on a resin layer, and then pattern copper plating is applied on the ultrathin copper foil. Next, the ultrathin copper foil is removed by flash etching to form a desired wiring.

Usually, a thin copper foil with a carrier is used in the MSAP method. In the thin copper foil with a carrier, a release layer and a thin copper foil are formed in this order on one side of a copper foil (carrier copper foil) as a carrier, and the surface of the thin copper foil is a roughened surface. Then, after superposing the roughened surface on the resin substrate, the whole is thermocompression bonded, then the carrier copper foil is peeled and removed, and the bonding side of the thin copper foil with the carrier copper foil is exposed, and there It is used in the form of forming a predetermined wiring pattern.
A hole called a via is opened for interlayer connection in the build-up wiring board, and this hole is often formed by laser light irradiation. In the MSAP method, a method called direct laser processing is used in which holes are formed in the copper foil and the resin at a stretch by directly irradiating the copper foil with laser light.

  The copper foil with carrier used in the MSAP method is usually M-sided on the resin base, and the laser-treated surface (S-surface) is smooth and not sufficiently laser-absorbing. As described above, browning (etching roughening) is required. Therefore, Patent Document 1 proposes a copper foil having good laser processability by having a laser absorption layer made of chromium, cobalt, nickel, iron or the like on the laser processed surface in order to improve the laser processability of the S surface. Has been. However, the thin copper foil in the carrier-attached copper foil is produced by an ordinary copper sulfate bath plating bath, and there is a problem that pinholes frequently occur.

Patent Document 2 proposes a copper foil in which pinholes are suppressed by uniformly forming a nickel layer, a zinc layer, and a chromate layer as an intermediate layer. However, since the intermediate layer (peeling layer) is formed on the glossy surface of the carrier foil, the intermediate layer to which the laser hits after peeling the carrier foil is smooth and hardly absorbs laser light, and the laser processability is poor. Moreover, since it is a copper foil with a carrier, there is a problem that it takes time to peel off the copper foil with a carrier and the handling property is poor.

  In patent document 3, the copper foil with a carrier which improved the laser workability and the etching property by suppressing the variation in the roughness of the intermediate layer side of the thin copper foil is proposed. However, the thin copper foil in the carrier-attached copper foil is produced by an ordinary copper sulfate bath plating bath, and there is a problem that pinholes frequently occur.

JP 2013-75443 A International Publication No. 2015/030256 JP 2014-208480 A

The MSAP method uses a copper foil with a carrier, but this copper foil with a carrier has the following problems.
・ Many pinholes are decreasing the manufacturing yield.
-The intermediate layer that the laser hits after peeling the carrier foil is smooth and difficult to absorb the laser beam, and the laser processability is poor. Therefore, a browning process (etching roughening process) is required as a pre-process for laser processing.
・ The manufacturing process has been increased due to the labor of the carrier foil peeling process.
Because of these problems, new materials that can replace the copper foil with carrier have been demanded. For these problems, the present invention has a high tensile strength after normal heating and heating, and it can be applied to the MSAP method without occurrence of wrinkles even with a thin foil without a carrier foil. Laser workability (direct laser processing) Another object of the present invention is to provide a surface-treated copper foil that is excellent in etching property and thin foil handling property and suitable for high-density wiring circuits with few pinholes.

The inventors of the present invention have intensively studied and found that a roughened surface having “Sdr of 25 to 120%” is suitable for direct laser processing. Further, the surface-treated copper foil of the present invention is a surface-treated copper foil having a tensile strength of 400 MPa to 700 MPa in a normal state, a tensile strength measured at room temperature after heating at 220 ° C. for 2 hours, and a foil thickness of 7 μm or less. In addition, the development area ratio (Sdr) of at least one surface is 25 to 120%, and the number of pinholes having a diameter of 30 μm or more is 20 pieces / m ² or less. It has been found that it is excellent in direct laser processing) and thin foil handling properties, and has few pinholes and is suitable for high-density wiring circuits. Based on this finding, the present invention has been completed.

  In the present invention, the normal state means that the surface-treated copper foil is kept at room temperature (= about 25 ° C.) without receiving a thermal history such as heat treatment. The tensile strength in the normal state can be measured by IPC-TM-650 at room temperature. The tensile strength after heating can be measured in the same manner as the normal tensile strength at room temperature after heating the surface-treated copper foil to 220 ° C. and holding it for 2 hours, followed by natural cooling to room temperature.

  When the tensile strength in a normal state is 400 to 700 MPa, the hand rigging property and the etching property are good. When the tensile strength in a normal state is less than 400 MPa, wrinkles are generated when a thin foil sheet product is conveyed, resulting in poor handling, and when it is more than 700 MPa, the foil is likely to break during precipitation production with a drum and is unsuitable for production. When the tensile strength measured at room temperature after heating is 300 MPa or more, the crystal grains are fine and the etching property is good even after heating in the substrate lamination step. Similarly, when the tensile strength after heating is 300 MPa or less, the crystal grains become large and are difficult to dissolve by etching.

  The foil thickness of the surface-treated copper foil is 7 μm or less, and may be 6 μm or less. When the foil thickness of the surface-treated copper foil exceeds 7 μm, the degree of opening by a low energy laser tends to be deteriorated. When the foil thickness of the surface-treated copper foil is 7 μm or less, particularly 6 μm or less, laser workability, particularly workability in laser irradiation with a low energy of about 8 W tends to be improved.

In the present invention, the foil thickness is a copper foil produced by electrolytic deposition, if necessary, formation of a laser absorption layer, formation of a roughening treatment layer, formation of a Ni layer, formation of a zinc layer, chromate treatment, It means the film thickness at the stage before laser processing after surface treatment such as formation of a silane coupling layer . The foil thickness can be measured as a mass thickness by an electronic balance.

In the present invention, by setting the development area ratio (Sdr) of at least one surface to 25 to 120%, direct laser workability when this surface is used as a laser irradiation surface can be enhanced.

  The developed area ratio (Sdr) means the ratio of the surface area added by the surface properties based on the ideal surface having the size of the measurement region, and is defined by the following equation.

Here, x and y in the formula are plane coordinates, and z is a coordinate in the height direction. z (x, y) indicates the coordinates of a certain point, and by differentiating this, the slope at that coordinate point is obtained. A is the plane area of the measurement region.
The development area ratio (Sdr) can be obtained by measuring and evaluating the unevenness of the copper foil surface with a three-dimensional white interference microscope, scanning electron microscope (SEM), electron beam three-dimensional roughness analyzer, etc. it can. In general, Sdr tends to increase as the spatial complexity of the surface texture increases, regardless of changes in the surface roughness Sa.

Here, the principle of direct laser processing will be described. When the reflectance on the copper foil surface is r, the absorptance is μ, and the transmittance is τ, the following equation holds.
r + μ + τ = 1
In direct laser processing, a laser beam such that τ = 0 is selected for copper foil, and CO2 gas laser is common, and the above equation is r + μ = 1. When the intensity of the laser beam is absorbed in a uniform distribution, the temperature distribution on the beam center axis (Z axis) is expressed by the following equation, where the beam radius is a.

Here, x and y in the formula are plane coordinates, and z is a coordinate in the height direction. P is the absorbed laser power [J / s], x is the thermal diffusivity = K / ρ · C [cm ² / S], and K is the thermal conductivity [J / cm · s · K], ρ is the density [g / cm3], C is the specific heat [J / g · K], t is the laser irradiation time [s], and a is the beam radius [cm].
The temperature rises with increasing time but saturates for a certain time. The temperature at that time is as follows.

  It can be seen that the temperature increases as the energy of the laser light absorbed on the copper foil surface increases as in the above equation. This is because atomic vibration is amplified and converted into heat by the energy of the absorbed laser beam. In direct laser processing, this thermal energy is used to melt and drill the copper foil at the laser irradiated location. In order to increase the accuracy and efficiency of direct laser processing, it is necessary to reduce the reflectance on the copper foil surface or increase the absorption rate, as can be seen from the above formula.

In the conventional MSAP method, since the absorption rate of the copper surface after peeling the carrier foil is low, it is compatible with direct laser processing by roughening the surface by browning and increasing the absorption rate, but the browning process is laborious Therefore, it is a problem from the viewpoint of manufacturing cost. Therefore, as a result of intensive research, the development area ratio (Sdr) of at least one surface of the copper foil is set to 25 to 120%, thereby improving the direct laser workability when this surface is used as the laser irradiation surface. I found out that I can do it. When the surface is such that the Sdr is 25 to 120%, a highly complex uneven shape is formed at 1 μm or less. When a copper foil having such a shape is irradiated with laser, diffused reflection increases and the absorption rate of laser light increases. Moreover, the outermost surface layer of the copper foil is activated and the oxide film is formed due to the highly complex surface irregularity shape, and the reflectivity decreases, and the increase in the surface area of the oxide film layer decreases the thermoelectric conductivity. However, it is considered that direct laser processability has increased due to an increase in the temperature of the laser beam irradiation part. When the Sdr of the laser machined surface is less than 25%, the absorbency of the laser tends to be poor because the reflectivity is high and the laser light absorptivity is poor. On the other hand, when Sdr is larger than 120%, the problem that the melted copper easily fills the hole again tends to occur and the laser processability deteriorates.

In addition, when the copper foil is made thin, it is known that the performance of the circuit board is deteriorated when a pinhole is generated. In the present invention, the copper having a pinhole of 30 μm or more in diameter is 20 pieces / m ² or less A foil is obtained, and the performance degradation of the circuit board can be suppressed.

The number of pinholes is determined by cutting the copper foil into an appropriate size, for example, 200 mm × 200 mm, marking the pinholes by, for example, a light transmission method, checking the diameter with an optical microscope, and counting holes of 30 μm or more. Unit area based on the number of the resulting pinhole (m ²⁾ Number of pinholes per an (pieces / m @ 2) can be calculated.

  ADVANTAGE OF THE INVENTION According to this invention, the copper foil which is excellent in etching property, laser workability, thin foil handling property, and pinhole resistance can be provided. In addition, since the tensile strength after normal and heating is high, it is possible to provide a surface-treated copper foil that can be applied to the MSAP method without using a carrier copper foil.

It is a figure which shows the precipitation apparatus of the conventional electrolytic copper foil. It is a figure which shows the deposition apparatus of the electrolytic copper foil which has a cathode reduction process. It is a figure which shows the relationship between the laser numerical aperture and pinhole number in an Example and a comparative example. Is a diagram showing the tensile strength and wrinkling defects relationship between the number of normal condition in Examples and Comparative Examples.

The surface-treated copper foil of the present invention has a development area ratio (Sdr) of 25 to 120%, but if the development area ratio (Sdr) is 30 to 80%, the laser processability tends to be further improved. Further, even when the thickness of the surface-treated copper foil is 7 μm or less, particularly 6 μm or less, the development area ratio (Sdr) is 30 to 80%, and the number of pinholes having a diameter of 30 μm or more is 10 / m ² or less. It is preferable. When the number of pinholes having a diameter of 30 μm or more exceeds 10 / m ² , the performance when applied to a circuit board tends to be lowered.

The surface-treated copper foil of the present invention preferably has a laser-processed surface of Yxy color system, Y of 25.0 to 65.5%, x of 0.30 to 0.48 % , and y of 0.28 to 0.41%. After the laser-processed surface of the surface-treated copper foil satisfies the above-mentioned development area ratio (Sdr), the processed surface is Yxy color system, Y is 25.0 to 65.5%, x is 0.30 to 0.48 % , and y is 0.28. When it is in the range of ˜0.41 %, the laser absorptivity is further improved and the laser processability is very good.

  The Yxy color system can be measured using a device such as a color meter in accordance with JIS Z 8722, for example.

  As mentioned above, the copper foil used in the MSAP method has an M-surface that is affixed to the resin base, and the laser-processed surface is smooth and not sufficiently laser-absorbing. A process (etching roughening process) is performed. In the present invention, it is possible to improve laser processability without performing browning.

Below, the conditions and method for manufacturing the surface-treated copper foil of this invention are demonstrated.
(1) Manufacture of electrolytic copper foil The copper foil in the present invention is, for example, an insoluble anode made of titanium coated with a platinum group element or an oxide element thereof using a sulfuric acid-copper sulfate aqueous solution as an electrolytic solution, and opposed to the anode. The electrolytic solution is supplied between the titanium cathode drum and the cathode drum, and copper is deposited on the surface of the cathode drum by applying a direct current between both electrodes while rotating the cathode drum at a constant speed. The produced copper is peeled off from the surface of the cathode drum and is continuously wound up.

  In the present invention, it is preferable to make the electrolytic copper foil so that the deposition potential of copper in the cathode drum surface is uniform and uniform. For this purpose, for example, a method of forming a foil in a state where an oxide film does not exist on the surface of the titanium drum can be mentioned. As an example, a cathode reduction process may be employed. As shown in FIG. 1, in a conventional electrolytic copper foil manufacturing apparatus, an electrolytic drum 102 serving as a cathode is polished by a buff 103 to remove an oxide film generated on the drum surface. On the other hand, in the cathode reduction step, for example, instead of the buff 103 of the electrolytic copper foil deposition apparatus of FIG. 1, the electrolytic solution (dilute sulfuric acid) of the cathode reduction apparatus 105 is used as shown in FIG. ) 106 to remove the oxide film. By removing the oxide film by the drum 102 and the cathode reduction device 105, it is expected that initial precipitation of copper uniformly occurs on the surface of the titanium drum and pinholes are reduced. In the manufacture of copper foil using the conventional titanium drum shown in FIG. 1, the film thickness of the titanium oxide film on the titanium drum surface is uneven, so that the copper deposition potential varies within the drum surface. Hall was easy to occur. Pinholes can be reduced by employing a cathode reduction process and increasing the cathode reduction current density. This is because it is considered that the reduction of the titanium oxide further proceeds due to the increase in the cathode reduction current density, the distribution of the copper deposition potential on the surface of the titanium drum is eliminated, and pinholes can be suppressed.

  In the production of the electrolytic copper foil, ethylenethiourea, polyethylene glycol, tetramethylthiourea, polyacrylamide or the like may be added as an additive to the electrolytic solution. By increasing the addition amount of ethylenethiourea and tetramethylthiourea, the tensile strength in the normal state and the tensile strength after heating can be increased. When the tensile strength in the normal state is 400 to 700 MPa, the handling property and the etching property are good. When the tensile strength in the normal state is less than 400 MPa, the handleability is poor, and when it is more than 700 MPa, the foil is likely to break and is unsuitable for production. In addition, when the tensile strength measured at room temperature after heating at 220 ° C. for 2 hours is 300 MPa or more, the crystal grains are fine and the etching property is good even after heating by laminating the substrates. Similarly, when the tensile strength after heating is 300 MPa or less, the crystal grains become large and are difficult to dissolve by etching, so that the etching property is deteriorated.

(2) Copper foil surface treatment <Laser absorption layer forming treatment>
Next, surface treatment for forming a laser absorption layer is performed on the copper foil obtained above. In the present invention, an uneven plating layer is formed on one surface of the copper foil by a pulse current. This surface becomes a laser processed surface when a circuit is produced by the MSAP method using copper foil. The surface on which the laser absorption layer is formed may be the deposition start surface (S surface) or the deposition end surface (M surface) in the electrolytic copper foil manufacturing process. In general, the bonding surface (roughening surface) with the resin substrate is often the M surface and the laser processed surface is the S surface. However, in the present invention, the S surface is roughened with the resin substrate. The processed surface may be a M-plane. That is, the roughening process layer may be formed in the electrolytic deposition start surface (S surface) in the manufacture process of electrolytic copper foil.

  In the present invention, by providing an appropriate surface area so that the developed area ratio Sdr of the M surface or S surface, which is the laser processing surface, is 25 to 120%, direct laser processing can be performed without browning. I found. Moreover, an etching factor can also be improved by forming a roughening process layer in the electrolytic deposition start surface in the manufacture process of electrolytic copper foil.

The plating bath composition for laser absorption layer formation, may be added copper sulfate pentahydrate, sulfuric acid, hydroxyethyl Le cellulose (HEC), polyethylene glycol (PEG), such as thiourea. By adding positive pulse currents having different current values in two stages, the additive acting in accordance with the corresponding two-stage deposition potential changes, and a complex uneven shape can be formed. As a result, a deposition surface with excellent laser absorption can be obtained. Specifically, in a stepped pulse current where one step current value (Ion1)> two step current value (Ion2), one step current value (Ion1) or one step time (ton1) is increased. As a result, the S-dr of the M surface tends to increase. By applying such a two-stage pulse current at a constant time interval (toff), a surface shape having an Sdr value with good laser processability can be obtained.

  Laser workability is improved when Sdr is in the range of 25 to 120%. Such a foil has a fine uneven shape of about 2 μm or less on the surface of the surface-treated copper foil, and the laser light absorbability is increased. If the Sdr is less than 25%, the laser beam is not absorbed well and the laser processability is poor. If Sdr is greater than 120%, the absorption rate of light at the wavelength of the CO2 laser is lowered and laser processability is lowered. Further, when the time interval (toff) of the pulse current is increased, Y decreases in the Yxy color system. When Sdr is in the range of 25 to 120% and Y is in the range of 15.0 to 85.0% in the Yxy color system, laser processability is improved. If Y is less than 15% or greater than 85%, the laser processability tends to decrease. As Sdr increases, the laser numerical aperture tends to increase, and as the Y value decreases, the laser numerical aperture tends to increase. The laser-irradiated surface has Sdr in the range of 25 to 120%, and in the Yxy color system, Y is 25.0 to 65.5%, x is 0.30 to 0.48%, and y is 0.28 to 0.41%. .

<Formation of roughening treatment layer>
On the surface opposite to the laser processed surface of the copper foil, a roughened layer having a fine uneven surface is formed by electrodeposition of fine copper particles. The roughening layer is formed by electroplating, but it is preferable to add a chelating agent to the plating bath, and the concentration of the chelating agent is suitably 0.1 to 5 g / L. Examples of chelating agents include DL-malic acid, sodium EDTA solution, sodium gluconate, and diethylenetriaminepentaacetic acid pentasodium (DTPA).

Copper sulfate, sulfuric acid and molybdenum may be added to the electrolytic bath. Etching properties can be improved by adding molybdenum. Usually, the copper concentration is 13 to 72 g / L, the sulfuric acid concentration is 26 to 133 g / L, the liquid temperature is 18 to 67 ° C., the current density is 3 to 67 A / dm ² , and the treatment time is 1 second to 1 minute 55 seconds. Electrodeposition is performed at

<Formation of nickel layer, zinc layer, chromate treatment layer>
In the present invention, it is preferable to further form a nickel layer and a zinc layer in this order on the roughened surface. This zinc layer increases the bonding strength with the substrate by preventing deterioration of the substrate resin and surface oxidation of the thin copper foil due to the reaction with the thin copper foil substrate resin when the thin copper foil and the resin substrate are thermocompression bonded. Work. In addition, the nickel layer is zinc for preventing the zinc of the zinc layer from thermally diffusing to the copper foil (electrolytic copper plating layer) side at the time of thermocompression bonding to the resin substrate, so that the above functions of the zinc layer are effectively exhibited. Serves as an underlayer for the layer.
In addition, these nickel layers and zinc layers can be formed by applying a known electrolytic plating method or electroless plating method. The nickel layer may be formed of pure nickel or a phosphorus-containing nickel alloy.

Further, it is preferable to further perform chromate treatment on the surface of the zinc layer because an antioxidant layer is formed on the surface. As the chromate treatment to be applied, a known method may be used, and examples thereof include a method disclosed in JP-A-60-86894. By attaching a chromium oxide of about 0.01 to 0.3 mg / dm ² and its hydrate in terms of the amount of chromium, an excellent rust preventive ability can be imparted to the copper foil.

<Silane treatment>
Further, when a surface treatment using a silane coupling agent is further performed on the chromate-treated surface, a functional group having a strong affinity for the adhesive is imparted to the copper foil surface (the surface on the side bonded to the substrate). Therefore, the bonding strength between the copper foil and the substrate is further improved, and the rust prevention and moisture absorption heat resistance of the copper foil are further improved.

   Silane coupling agents include vinyl silane, epoxy silane, styryl silane, methacryloxy silane, acryloxy silane, amino silane, ureido silane, chloropropyl silane, mercapto silane, sulfide silane, isocyanate silane Examples include silane. These silane coupling agents are usually made into 0.001 to 5% aqueous solution, which is applied to the surface of the copper foil and then dried by heating as it is. In addition, it can replace with a silane coupling agent, and the same effect can be acquired even if it uses coupling agents, such as a titanate type | system | group and a zirconate type | system | group.

(3) Manufacture of copper-clad laminate First, a copper foil surface (roughening layer surface) of a thin copper foil is placed on the surface of an electrically insulating substrate made of glass epoxy resin or polyimide resin, and heated and heated. A copper-clad laminate with or without a carrier is produced by pressing. Since the surface-treated copper foil of the present invention has a high tensile strength after normal and heating, it can sufficiently cope even without a carrier. Next, the surface of the copper-clad laminate is irradiated with a CO2 gas laser to make a hole. That is, a CO2 gas laser is irradiated from the surface of the surface-treated copper foil on which the laser absorption layer is formed, to perform a drilling process that penetrates the surface-treated copper foil and the resin substrate.

Hereinafter, the present invention will be described in detail by way of examples.
(1) Production of Copper Foil and Formation of Laser Absorbing Layer Examples 1 to 21 and Examples 1 to 21 by the cathode reduction step of the electrolytic solution, current density, and bath temperature shown in Table 1 and the electrolytic deposition step under the electrolytic conditions shown in Table 2 The electrolytic copper foil of Comparative Examples 1-9 was manufactured. A laser absorption layer was formed by electrolytic plating treatment of these electrolytic copper foils in a plating bath having a composition shown in Table 3, a treatment surface, and electrolytic conditions (pulse width of pulse voltage, current density, time, bath temperature). In Example 22, a laser absorption layer was formed by alternating current, and in Example 23, a laser absorption layer was formed by MEC etch bond CZ-8000 treatment. In the electrolysis conditions in Table 3, Ion1 represents the first stage pulse current density, Ion2 represents the second stage pulse current density, and ton1 represents the first stage pulse current application time. ton2 represents the pulse current application time of the second stage, and toff represents the time when the current between the pulse current of the second stage and the pulse current of the first stage is zero. The surface where the laser absorbing layer is formed is the surface opposite to the roughened surface shown in Table 4. In Examples 1 to 19, 22 to 23 and Comparative Examples 4 and 6 to 8, the laser absorbing layer is formed on the M surface. Was formed (roughening treatment was performed on the S surface), and in Examples 20 and 21 and Comparative Example 9, a laser absorption layer was formed on the S surface (roughening treatment was performed on the M surface). Comparative Examples 1-3 and 5 did not form a laser absorption layer.

(2) Roughening treatment Next, a roughening treatment layer having a fine concavo-convex surface was formed on the surface opposite to the laser absorption layer (roughening treatment surface shown in Table 4) by electrodeposition of roughening particles. In all Examples and Comparative Examples, the roughening plating process was performed as described below to form a roughening treatment layer.
(Roughening plating treatment)
Copper sulfate: 13-72 g / L as copper concentration
Sulfuric acid concentration: 26-133 g / L
DL-malic acid: 0.1-5.0 g / L
Liquid temperature: 18-67 degreeC
Current density: 3 to 67 A / dm ²
Processing time: 1 second-1 minute 55 seconds

(3) Formation of Ni-containing foundation layer For all Examples 1 to 23 and Comparative Examples 1 to 9, after the formation of the roughening layer, electrolysis was performed on the roughening layer under the Ni plating conditions shown below. By plating, a base layer (Ni adhesion amount 0.06 mg / dm ² ) was formed.
<Ni plating conditions>
Nickel sulfate: 5.0 g / L as nickel metal
Ammonium persulfate 40.0 g / L
Boric acid 28.5g / L
Current density 1.5A / dm ²
pH 3.8
Temperature 28.5 ° C
Time 1 second-2 minutes

(4) Formation of heat-resistant layer containing Zn For all of Examples 1 to 23 and Comparative Examples 1 to 9, after the formation of the underlayer, electrolytic plating is performed on the underlayer under the following Zn plating conditions. Thus, a heat-resistant treatment layer (Zn adhesion amount: 0.05 mg / dm ² ) was formed.
<Zn plating conditions>
Zinc sulfate heptahydrate 1-30g / L
Sodium hydroxide 10-300g / L
Current density 0.1-10 A / dm ²
Temperature 5-60 ° C
Time 1 second-2 minutes

(5) Formation of anticorrosion treatment layer containing Cr For all Examples 1 to 23 and Comparative Examples 1 to 9, after the formation of the above heat treatment layer, on this heat treatment layer, the following chromium plating treatment conditions The antirust process layer (Cr adhesion amount: 0.02 mg / dm < ² >) was formed by processing by.
<Chrome plating conditions>
(Chromium plating bath)
Chromic anhydride CrO3 2.5g / L
pH 2.5
Current density 0.5A / dm ²
Temperature 15-45 ° C
Time 1 second-2 minutes

(6) Formation of Silane Coupling Agent Layer For all Examples 1 to 23 and Comparative Examples 1 to 9, after the formation of the antirust treatment layer, methanol or ethanol was added to the silane coupling agent aqueous solution on the antirust treatment layer. And a treatment liquid adjusted to a predetermined pH was applied. Thereafter, the silane coupling agent layer was formed by holding for a predetermined time and drying with warm air.

(7) Evaluation method <foil thickness>
The thickness of the surface-treated copper foils of all Examples 1 to 23 and Comparative Examples 1 to 9 obtained by the above treatments (1) to (5) was measured as a mass thickness using an electronic balance. The results are shown in Table 1.

<Tensile strength>
The surface-treated copper foils of all Examples 1 to 23 and Comparative Examples 1 to 9 obtained by the above treatments (1) to (5) were cut into a size of 12.7 × 130 mm and manufactured by Instron at room temperature. The tensile strength of the copper foil in the normal state was measured with a 1122 type tensile tester testing device. Moreover, after heating the copper foil cut out to 12.7 * 130 mm at 220 degreeC for 2 hours, and naturally cooling to normal temperature, the tensile strength after a heating was measured similarly. The measurement was based on IPC-TM-650. The results are shown in Table 4.

<Development area ratio>
About all the surface-treated copper foils of Examples 1 to 23 and Comparative Examples 1 to 9 obtained by the above treatments (1) to (5), the surface shape was measured using WykoContourGT-K of BRUKER, and the shape analysis was performed. And the development area ratio (Sdr) was determined. The shape analysis uses a high resolution CCD camera with a VSI measurement method, the light source is white light, the measurement magnification is 10 times, the measurement range is 477 μm × 357.8 μm, the lateral sampling is 0.38 μm, the speed is 1, the backscan is 5 μm, and the length is The processing was performed under the conditions of 5 μm and Threshold of 5%, and the data processing was performed after the filtering of TermsRemoval. The results are shown in Table 4.

<Yxy color system>
In the Yxy color system of the copper foils of Examples 1 to 23 and Comparative Examples 1 to 9 obtained by the above treatments (1) to (5), Y, x, and y are color meters SM-T45 (Suga Test Machine) Co., Ltd.), 45 ° illumination 0 ° light reception, light source C light 2 degree field of view (halogen lamp) can be measured. The results are shown in Table 4.

<Pinhole>
All surface treated copper foils of Examples 1 to 23 and Comparative Examples 1 to 9 obtained by the above treatments (1) to (5) are cut into a size of 200 mm × 200 mm, and pinholes are marked by a light transmission method. did. About five 200mm × 200mm size surface-treated copper foils (total 0.2m ² ), the diameter was confirmed with an optical microscope, and holes of 30 μm or more were counted as pinholes. Pinholes observed with an optical microscope can be either round or irregular, but the major diameter of each pinhole (the distance between the two most distant points on the outer periphery of the pinhole) was measured as the diameter. Table 4 shows the results of calculating the number of pinholes per unit area (m ² ) (pieces / m ² ) based on the number of pinholes obtained.

<Etching factor>
Next, a dry resist film was used for the surface-treated copper foils of Examples 1 to 23 and Comparative Examples 1 to 9 obtained by the above treatments (1) to (6), and L & S = 100 μm / 200 μm by dry etching. A resist pattern having a line / interval was formed. After etching the wiring pattern using copper chloride and hydrochloric acid as the etching solution, the etching factor was measured. The etching factor (Ef) is a value expressed by the following equation, where H is the thickness of the surface-treated copper foil, B is the bottom width of the formed wiring pattern, and T is the top width of the formed wiring pattern. Say.
Ef = 2H / (BT)

  If the etching factor is small, the verticality of the sidewalls in the wiring pattern is lost, and there is a risk that the wiring pattern may be disconnected in the case of a fine wiring pattern having a narrow line width. In this example, the bottom width and the top width were measured with a microscope and the etching factor was calculated with respect to the pattern when the just etch (resist end portion and bottom of the copper foil pattern were aligned) position. The results are shown in Table 4.

<Laser numerical aperture>
Heating all of the surface-treated copper foil two Examples 1 to 23 and Comparative Examples 1-9 obtained by the above process on both sides of the substrate FR4, to prepare a CCL (copper clad laminate) by bonding under pressure. Next, 100 holes were drilled with a CO2 laser drilling machine, and the number of openings was counted. Table 4 shows the number of apertures formed by irradiation for 10 msec for each irradiation time of 50 W and 8 W. Even in the case of 8 W where the irradiation energy is low, those having a small decrease in numerical aperture can be evaluated as having high laser processability.

<Handling: Wrinkle defect count>
All the surface treated copper foils of Examples 1 to 23 and Comparative Examples 1 to 9 obtained by the above treatments (1) to (5) were cut into a size of 200 mm × 200 mm, and the surface treated copper foil and the substrate FR4 were Heating and pressure bonding at 170 ° C and 1.5 MPa (pressure) for 1 hour to produce 30 substrates, visually check for wrinkles, and count the wrinkled substrate as one wrinkle defect Table 4 shows the number of wrinkle defects. This evaluated the handleability of the surface-treated copper foil.

  As can be seen from Table 4, Examples 1 to 23 all have a tensile strength of 400 to 700 MPa, a tensile strength after heating for 2 hours at 220 ° C. of 300 MPa or more, a foil thickness of 7 μm or less, and a laser irradiated surface. Development area ratio (Sdr) of 25 to 120%, as shown in the evaluation results, the number of pinholes is 20 or less, Ef is 2.0 or more, laser numerical aperture at 8 W is 90 or more, wrinkles It can be seen that the number of defects is 3 or less, there are few pinholes, laser workability is excellent, and handling properties are also excellent.

  In contrast, Comparative Examples 1 to 9 have a tensile strength of 400 to 700 MPa and a tensile strength after heating at 220 ° C. for 2 hours of 300 MPa or more, but Comparative Examples 2, 3, 5 to 7, and 9 Since the development area ratio (Sdr) of the laser irradiation surface does not satisfy 25 to 120%, the laser numerical aperture at 8 W is less than 90, indicating that the laser apertureability is not good. Further, in Comparative Examples 1 and 4, the occurrence of pinholes exceeds 20 depending on the manufacturing conditions of the surface-treated copper foil, and it can be seen that Comparative Example 8 has poor foil opening because the foil thickness is 9 μm.

  Based on the above evaluation results, for the surface treated copper foils of Examples 1 to 21 and Comparative Examples 1 to 9, the relationship between the numerical aperture and the number of pinholes when the irradiation energy is 8 W is shown in the graph of FIG. It was. As can be clearly seen from FIG. 3, the surface-treated copper foil of the example has a large number of apertures and less pinholes and is excellent in laser processability, whereas the surface-treated copper foil of the comparative example has an opening. It can be seen that the number is small or the number of pinholes is large and the laser processability is poor.

  Moreover, based on said evaluation result, about the surface treatment copper foil of Examples 1-21 and Comparative Examples 1-9, the relationship between the tensile strength in a normal state and the generation | occurrence | production number of pinholes was shown on the graph of FIG. As can be clearly seen from FIG. 3, the surface-treated copper foil of the example has a large number of apertures and less pinholes and is excellent in laser processability, whereas the surface-treated copper foil of the comparative example has an opening. It can be seen that the number is small or the number of pinholes is large and the laser processability is poor.

According to the present invention, high tensile strength, the line and the line width is fine, etching resistance, excellent laser processability and Usuhaku handling properties, and to provide a small yet front surface treated copper foil of the pinhole Can be used and has high industrial applicability.

101 Deposited Copper Foil 102 Drum 103 Buffing Device 105 Cathode Reduction Device 106 Electrolyte

Claims (10)

  Tensile strength in the normal state is 400 to 700 MPa, tensile strength measured at room temperature after heating at 220 ° C. for 2 hours is 300 MPa or more, foil thickness is 7 μm or less, and the development area ratio (Sdr) of at least one surface is Surface-treated copper foil that is 25-120%. The surface-treated copper foil according to claim 1, wherein the number of pinholes having a diameter of 30 μm or more is 20 / m ² or less.   The surface-treated copper foil according to claim 1 or 2, wherein the foil thickness is 6 µm or less.   The surface-treated copper foil according to any one of claims 1 to 3, wherein the developed area ratio (Sdr) is 30 to 80%. The surface-treated copper foil according to claim 1, wherein the number of pinholes having a diameter of 30 μm or more is 10 / m ² or less.   6. The surface-treated copper foil according to any one of claims 1 to 5, wherein the roughened layer is formed on an electrolytic deposition starting surface in the production process of the electrolytic copper foil.   Surface-treated copper foil for circuit processed by direct laser processing, the tensile strength in the normal state is 400-700 MPa, the tensile strength measured at room temperature after heating at 220 ° C. for 2 hours is 300 MPa or more, and the foil thickness is 7 μm or less, the development area ratio (Sdr) of at least one surface is 25 to 120%, and the laser irradiation surface is Yxy color system, Y is 25.0 to 65.5%, x is 0.30 to 0.48%, and y is Surface-treated copper foil for circuits having 0.28 to 0.41%. The surface-treated copper foil for circuit according to claim 7, wherein the number of pinholes having a diameter of 30 μm or more is 20 / m ² or less. The surface-treated copper foil for circuit according to claim 7, wherein the number of pinholes having a diameter of 30 μm or more is 10 / m ² or less.   The surface-treated copper foil of any one of Claims 1-6 or the surface-treated copper foil for circuits of any one of Claims 7-9, The roughening process layer of this surface-treated copper foil A copper clad laminate having an insulating substrate on the side surface.

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