JP6529684B2 - Surface-treated copper foil and copper-clad laminate using the same - Google Patents

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.

  In the printed wiring board, a thin copper foil for forming a surface circuit is placed on the surface of an electrically insulating substrate made of glass epoxy resin, polyimide resin or the like, and then heated and pressed to manufacture a copper-clad laminate. Then, after forming through holes and plating through holes in the copper-clad laminate sequentially, the copper foil of the copper-clad laminate is etched to provide a desired line width and a desired inter-line pitch. Form a wiring pattern. Finally, in order to expose solder resist application, exposure, through-hole plating or plating of the connection portion of the electronic component, removal of the uncured solder resist or other finishing treatment is performed by caustic soda or the like.

As the copper foil used at this time, 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. 1 is used. 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 fact, it has unevenness. Usually by a roughening treatment on the M plane, thereby improving the adhesion to the substrate resin.

  Recently, adhesive resin such as epoxy resin is attached in advance to the roughened surface of copper foil, and resin-coated copper foil is used as the insulating resin layer in semi-cured state (B stage) to form a surface circuit. It has been practiced to use a copper foil for the purpose of forming a printed wiring board, especially a build-up wiring board, by thermocompression bonding the insulating resin layer side to a substrate (insulating substrate). In the build-up wiring board, there is a demand for high integration of various electronic components, and correspondingly, the wiring pattern is also required to have a high density, and a wiring pattern with a fine line width and a line pitch, A printed wiring board of a pattern has come to be required. For example, multilayer boards used for servers, routers, communication base stations, in-vehicle mounting boards, etc. and multilayer boards for smart phones require printed wiring boards with high-density fine wiring with line widths and pitches of around 15 μm. ing.

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

Usually, thin copper foil with a carrier is used for the MSAP method. In the carrier-attached thin copper foil, 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, the roughened surface is placed on the resin substrate, the whole is thermocompression-bonded, and then the carrier copper foil is peeled off and removed to expose the side of the thin copper foil to be bonded to the carrier copper foil. It is used in the aspect of forming a predetermined | prescribed wiring pattern.
Although holes called vias are opened for interlayer connection in the buildup wiring board, the holes are often made by laser light irradiation. Then, in the MSAP method, a direct laser processing method is used in which holes are cut at once in copper foil and resin by irradiating the copper foil with laser light directly.

  The copper foil with carrier used in the MSAP method usually has M surface attached to the resin substrate, and the laser processed surface (S surface) is smooth and the laser absorptivity is not sufficient, so pretreatment for laser processing As browning process (etching roughening process) is required. Therefore, in Patent Document 1, in order to enhance the laser processability of the S surface, a copper foil having good laser processability is proposed by having a laser absorption layer made of chromium, cobalt, nickel, iron or the like on the laser processed surface. It is done. However, the thin copper foil in the copper foil with carrier is manufactured by a common copper sulfate bath plating bath, and there is a problem that pinholes occur frequently.

Moreover, in patent document 2, the copper foil which suppressed the pinhole is proposed by forming a nickel layer, a zinc layer, and a chromate layer uniformly as an intermediate | middle 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 is applied after peeling the carrier foil is smooth and hardly absorbs laser light, and the laser processability is poor. Moreover, since it is copper foil with a carrier, it takes time and effort to peel the copper foil with a carrier, and there exists a problem that handling property is bad.

  In patent document 3, the copper foil with a carrier which improved laser processability and etching property is proposed by suppressing the dispersion | variation in the roughness by the side of the intermediate | middle layer of thin copper foil. However, the thin copper foil in the copper foil with carrier is manufactured by a common copper sulfate bath plating bath, and there is a problem that pinholes occur frequently.

JP, 2013-75443, A International Publication 2015/030256 JP, 2014-208480, A

Although a copper foil with a carrier is used in the MSAP method, this copper foil with a carrier has the following problems.
・ There are many pinholes and the manufacturing yield is reduced.
The intermediate layer to which the laser is applied after peeling the carrier foil is smooth, hardly absorbs the laser light, and the laser processability is poor. Therefore, a browning process (etching roughening process) is required as a pretreatment for laser processing.
The process of peeling off the carrier foil takes time and increases the manufacturing cost.
Because of these problems, new materials have been required to replace copper foils with carriers. To solve these problems, the present invention has high tensile strength in normal state and after heating, and can be applied to MSAP method without generation of wrinkles even in thin foil without carrier foil, and laser processability (direct laser processing) It is an object of the present invention to provide a surface-treated copper foil which is excellent in etching properties and thin foil handling properties and is suitable for high density wiring circuits with few pinholes.

The present inventors have intensively researched and found that the roughened surface having “Sdr of 25 to 120%” is suitable for direct laser processing. The surface-treated copper foil of the present invention is a surface-treated copper foil having a tensile strength of 400 to 700 MPa in a normal state and a tensile strength of 300 MPa or more measured at normal temperature after heating for 2 hours at 220 ° C. and a foil thickness of 7 μm or less. Etchability and laser processability by setting the development area ratio (Sdr) of at least one surface to 25 to 120% and setting the number of pinholes having a diameter of 30 μm or more to 20 / m ² or less It has been found that it is excellent in direct laser processing) and thin foil handling, and has few pinholes and is suitable for high density wiring circuits, and the present invention has been completed based on this finding.

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

  When the tensile strength in the normal state is 400 to 700 MPa, the hand rigging property and the etching property are good. If the tensile strength in the normal state is less than 400 MPa, the thin foil sheet product is wrinkled during transport, resulting in poor handleability. When the tensile strength measured at normal 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 laminating step. If the tensile strength after heating is 300 MPa or less, the crystal grains become large and it becomes difficult to melt by etching, so the etching property is deteriorated.

  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 deteriorate. When the foil thickness of the surface-treated copper foil is 7 μm or less, particularly 6 μm or less, the laser processability tends to be high, particularly the processability in laser irradiation with a low energy of about 8 W or so.

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

In the present invention, by setting the spread area ratio (Sdr) of at least one surface to 25 to 120%, it is possible to improve direct laser processability when this surface is a laser irradiation surface.

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

Here, x and y in the equation 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. Further, A is a plane area of the measurement area.
The developed area ratio (Sdr) can be determined by measuring and evaluating the difference in unevenness of the copper foil surface with a three-dimensional white light interference microscope, a scanning electron microscope (SEM), an electron beam three-dimensional roughness analyzer, etc. it can. In general, Sdr tends to increase as the spatial complexity of the surface property increases, regardless of the change in the surface roughness Sa.

Here, the principle of direct laser processing will be described. Assuming that the reflectance on the copper foil surface is r, the absorptivity is μ, and the transmittance is τ, the following equation holds.
r + μ + τ = 1
In direct laser processing, a laser beam is selected such that τ = 0 for copper foil, a CO 2 gas laser is generally used, and the above equation is r + μ = 1. When the intensity of the laser beam is absorbed with a uniform distribution, the temperature distribution on the central axis of the beam (Z axis) is represented by the following equation, where a is a beam radius.

Here, x and y in the equation are plane coordinates, and z is a coordinate in the height direction. Also, 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 / cm 3], C is the specific heat [J / g · K], t is the laser irradiation time [s], a is the beam radius It is [cm].
The temperature rises with time, but saturates for a fixed time, and the temperature at that time is as follows.

  It can be seen that the temperature increases as the energy of the laser beam absorbed on the copper foil surface increases, as in the above equation. This is because the energy of the absorbed laser light amplifies atomic vibrations and converts them into heat. In the direct laser processing, the heat energy is used to melt the copper foil at the laser-irradiated portion and perform drilling processing. In order to increase the accuracy and efficiency of direct laser processing, it is necessary to lower the reflectance on the copper foil surface or to increase the absorptivity as understood from the above equation.

In the conventional MSAP method, since the absorptivity of the surface of copper after carrier foil peeling is low, the surface is roughened by browning to cope with direct laser processing by increasing the absorptivity. Is a problem in terms of manufacturing cost. Then, as a result of repeating earnest research, the direct laser processability at the time of making this surface into a laser irradiation surface can be improved by making the developed area ratio (Sdr) of at least one surface of copper foil into 25 to 120%. I found out what I could do. When the surface has an Sdr of 25 to 120%, a highly complicated uneven shape of 1 μm or less is formed. When a copper foil having such a shape is irradiated with a laser, irregular reflection is increased to increase the absorptivity of the laser light. Further, the outermost surface layer of the copper foil is activated to form an oxide film due to the highly complicated surface asperity shape, whereby the reflectance decreases, and the surface area of the oxide film layer increases, so that the thermoelectric conductivity decreases. It is considered that the direct laser processability is enhanced by the temperature rise of the laser beam irradiated portion. If the Sdr of the laser-processed surface is less than 25%, the absorptivity of the laser tends to deteriorate because the reflectance is high and the absorptivity of the laser beam is poor. If Sdr is more than 120%, the problem of molten copper filling again tends to occur, and the laser processability is deteriorated.

Moreover, when making copper foil thin foil, when a pinhole generate | occur | produces is known to reduce the performance of a circuit board, but in this invention, the copper whose diameter is 30 micrometers or more is 20 pieces / m < ² > or less. A foil is obtained, and performance degradation of the circuit board can be suppressed.

As for the number of pinholes, a copper foil is cut into an appropriate size, for example, 200 mm × 200 mm, for example, after marking the pinholes by a light transmission method, the diameter is confirmed by an optical microscope and holes of 30 μm or more are counted. The number of pinholes per unit area (m ² ) can be calculated based on the number of pinholes obtained.

  ADVANTAGE OF THE INVENTION According to this invention, the copper foil which is excellent in etching property, laser processability, thin foil hand rig property, and pinhole resistance can be provided. In addition, since the tensile strength in normal conditions and after 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 deposition 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 of 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 spread area ratio (Sdr) of 25 to 120%, but if the spread area ratio (Sdr) is 30 to 80%, laser processability tends to be further enhanced. Moreover, even when the foil 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 of 30 μm or more in diameter is 10 pieces / m ² or less. Is preferred. If 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 decrease.

In the surface-treated copper foil of the present invention, it is desirable that the laser-worked surface has a 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%. After the laser-processed surface of the surface-treated copper foil satisfies the above-mentioned expanded area ratio (Sdr), the processed surface is Yxy color system and Y is 25.0% to 65.5%, x is 0.30 to 0.48 % , 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, for example, using a device such as a color meter in accordance with JIS Z 8722.

  As described above, the copper foil used in the MSAP method has an M-surface to be attached to a resin substrate, and the laser-processed surface is smooth and laser absorption is not sufficient. A process (etching roughening process) is performed. The present invention makes it possible to enhance laser processability without performing browning.

Below, the conditions for manufacturing the surface-treated copper foil of this invention and a method are demonstrated.
(1) Production of Electrolyzed Copper Foil The copper foil in the present invention is, for example, a sulfuric acid-copper sulfate aqueous solution as an electrolyte, and an insoluble anode made of titanium coated with a platinum group element or its oxide element, and the anode facing the anode. The electrolytic solution is supplied between the titanium cathode drum and the cathode drum provided, and while the cathode drum is rotated at a constant speed, copper is deposited on the surface of the cathode drum by applying a direct current between both electrodes. The copper is separated from the surface of the cathode drum and continuously wound.

  In the present invention, it is preferable to form the electrodeposited copper foil so that the deposition potential of copper in the surface of the cathode drum does not vary and becomes uniform. For that purpose, for example, there is a method of forming a foil in the absence of an oxide film on the surface of a titanium drum. As an example, a cathode reduction step may be employed. As shown in FIG. 1, in the conventional electrolytic copper foil manufacturing apparatus, the electrolytic drum 102 to be a cathode is polished with a buff 103 to remove the oxide film formed 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 of the cathode reduction apparatus 105 (dilute sulfuric acid as shown in FIG. Step 106) to remove the oxide film. Since the oxide film is removed by the drum 102 and the cathode reduction device 105, it is expected that initial deposition of copper will be uniformly generated on the surface of the titanium drum, and the number of pinholes will be reduced. In the manufacture of copper foil by the conventional titanium drum shown in FIG. 1, the deposition potential of copper is dispersed within the drum surface due to unevenness in the film thickness of the titanium oxide film on the surface of the titanium drum. It was easy for a hole to occur. A cathode reduction step can be employed to reduce pinholes by increasing the cathode reduction current density. It is thought that reduction of the titanium oxide proceeds more as the cathode reduction current density increases, and the distribution of the deposition potential of copper on the surface of the titanium drum disappears, and pinholes can be suppressed.

  In the production of the electrodeposited copper foil, ethylenethiourea, polyethylene glycol, tetramethylthiourea, polyacrylamide or the like may be added as an additive to the electrolytic solution. The tensile strength in the normal state and the tensile strength after heating can be increased by increasing the addition amounts of ethylenethiourea and tetramethylthiourea. When the tensile strength in the normal state is 400 to 700 MPa, the handling property and the etching property are good. If the tensile strength in the normal state is less than 400 MPa, the handling property is poor, and if it is more than 700 MPa, foil breakage is likely to occur, which is unsuitable for production. In addition, when the tensile strength measured at normal temperature after heating at 220 ° C. for 2 hours is 300 MPa or more, crystal grains are fine and the etching property is good even after heating with lamination of substrates. Similarly, if the tensile strength after heating measured in the same manner is 300 MPa or less, the crystal grains become large and it becomes difficult to melt by etching, so the etching property is deteriorated.

(2) Surface treatment of copper foil <laser absorption layer formation treatment>
Next, surface treatment for forming a laser absorption layer is performed on the copper foil obtained above. In the present invention, the uneven plating layer is formed on one surface of the copper foil by a pulse current. This surface becomes a laser processing surface when producing a circuit by MSAP method using copper foil. The surface on which the laser absorption layer is formed may be a deposition start surface (S surface) or a deposition end surface (M surface) in the electrolytic copper foil manufacturing process. Generally, the adhesion surface (roughened surface) with the resin substrate is M surface and the laser processing surface is S surface in many cases, but in the present invention, the S surface with the resin substrate is rough The laser processing surface may be an M surface. That is, the roughening treatment layer may be formed on the electrolytic deposition start surface (S surface) in the process of manufacturing the electrolytic copper foil.

  In the present invention, by providing an appropriate surface area such that the spread area ratio Sdr of the M surface or the S surface to be a laser-processed surface is 25 to 120%, direct laser processing without browning becomes possible. Found out. In addition, the etching factor can be improved by forming the roughened layer on the electrolytic deposition initiation surface in the process of manufacturing the electrodeposited 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 applying positive pulse currents having different current values in two steps, the additives acting in response to the corresponding two steps of the deposition potential can be changed to form a complicated uneven shape. This provides a deposition surface with excellent laser absorptivity. Specifically, one step current value (Ion1) or one step time (ton1) is increased in the step-like pulse current in which one step current value (Ion1)> two step current value (Ion2) And, there is a tendency for Sdr of M surface to increase. By applying such a two-step pulse current at a constant time interval (toff), it is possible to obtain a surface shape having a good laser processability Sdr value.

  When Sdr is in the range of 25 to 120%, laser processability is improved. Such a foil has a fine uneven shape of about 2 μm or less on the surface-treated copper foil surface, and the absorbability of laser light is increased. If the Sdr is less than 25%, the absorption of laser light is poor and the laser processability is poor. When the Sdr is greater than 120%, the absorptivity of the light of the wavelength of the CO 2 laser is reduced and the laser processability is reduced. In addition, when the time interval (toff) of the pulse current is increased, Y decreases in the Yxy color system. When the Sdr is in the range of 25 to 120% and the Y in the Yxy color system is in the range of 15.0 to 85.0%, the laser processability is good. If Y is less than 15% or more than 85%, laser processability tends to be reduced. 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 irradiation surface has an Sdr in the range of 25 to 120%, and in the Yxy color system, the laser processability is particularly good when Y is 25.0 to 65.5%, x is 0.30 to 0.48%, and y is 0.28 to 0.41%. .

<Formation of roughened layer>
On the surface of the copper foil opposite to the laser-processed surface, a roughened layer having a fine uneven surface is formed by electrodeposition of fine copper particles. The roughened 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 preferably 0.1 to 5 g / L. The chelating agent may, for example, be a chelating agent such as DL-malic acid, sodium EDTA solution, sodium gluconate or disodiumtriaminepentaacetic acid pentasodium (DTPA).

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

<Formation of nickel layer, zinc layer, chromate treated 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. When the thin copper foil and the resin substrate are thermocompression-bonded, this zinc layer prevents the deterioration of the substrate resin due to the reaction with the thin copper foil substrate resin and the surface oxidation of the thin copper foil, thereby enhancing the bonding strength with the substrate. To work. In addition, the nickel layer prevents the zinc of the zinc layer from being thermally diffused to the copper foil (electrolytic copper plating layer) side at the time of thermocompression bonding to a resin substrate, thereby effectively exhibiting the above function of the zinc layer. Acts as a base layer for the layer.
The nickel layer and the zinc layer can be formed by applying a known electrolytic plating method or electroless plating method. In addition, the nickel layer may be formed of pure nickel or may be formed of a phosphorus-containing nickel alloy.

Further, if the surface of the zinc layer is further subjected to chromate treatment, an antioxidant layer is preferably formed on the surface. The chromate treatment to be applied may be according to a known method, for example, the method disclosed in Japanese Patent Application Laid-Open No. 60-86894. By attaching about 0.01 to 0.3 mg / dm ² of chromium oxide and its hydrate or the like in terms of chromium amount, it is possible to impart an excellent antirust ability to the copper foil.

<Silane treatment>
In addition, when the surface treated with a silane coupling agent is further applied to the above-mentioned chromate-treated surface, a functional group having a strong affinity with the adhesive is given to the copper foil surface (surface on the bonding side with the substrate). Therefore, the bonding strength between the copper foil and the substrate is further improved, and the corrosion resistance and moisture absorption heat resistance of the copper foil are further improved, which is preferable.

   As a silane coupling agent, vinyl based silane, epoxy based silane, styryl based silane, methacryloxy based silane, acryloxy based silane, amino based silane, ureido based silane, chloropropyl based silane, mercapto based silane, sulfide based silane, isocyanate based Silane etc. can be mentioned. These silane coupling agents are usually made into an aqueous solution of 0.001 to 5%, which may be coated on the surface of a copper foil and then dried by heating as it is. The same effect can be obtained by using a titanate-based or zirconate-based coupling agent instead of the silane coupling agent.

(3) Production of copper-clad laminate First, the copper foil surface (roughened layer surface) of thin copper foil is superimposed on the surface of an electrically insulating substrate made of glass epoxy resin, polyimide resin, etc., and heated and heated. The carrier is pressed to produce a copper clad laminate with or without carrier. The surface-treated copper foil of the present invention has a high tensile strength in the normal state and after heating and can sufficiently cope with no carrier. Next, the surface treated copper foil surface of the copper clad laminate is irradiated with CO 2 gas laser to make holes. That is, CO2 gas laser is irradiated from the surface in which the laser absorption layer of surface-treated copper foil is formed, and the drilling process which penetrates surface-treated copper foil and a resin substrate is performed.

The present invention will be explained in detail by the following examples.
(1) Production of copper foil and formation of laser absorption layer Examples 1-21 were carried out according to the electrolytic solution shown in Table 1, the current density, the cathode reduction process of the bath temperature and the electrolytic deposition process under the electrolytic conditions shown in Table 2. The electrolytic copper foils of Comparative Examples 1 to 9 were produced. A laser absorption layer was formed by electrolytic plating in a plating bath, a treated surface and electrolytic conditions (pulse width of pulse voltage, current density, time, bath temperature) having the composition shown in Table 3 for each of these electrolytic copper foils. 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. Under the electrolysis conditions in Table 3, Ion1 represents the pulse current density in the first stage, Ion2 represents the pulse current density in the second stage, and ton1 represents the pulse current application time in the first stage, ton2 denotes the second stage of the pulse current application time, toff is the current between the second stage of the pulse current and the first stage of the pulse current represents the time to zero. The surface on which the laser absorption layer is formed is the surface opposite to the roughened surface shown in Table 4, and in Examples 1 to 19 and 22 to 23 and Comparative Examples 4 and 6 to the laser absorption layer on the M surface (S surface is roughened), and in Examples 20 and 21 and Comparative Example 9, a laser absorbing layer is formed on S surface (M surface is roughened). Comparative Examples 1 to 3 and 5 did not form a laser absorption layer.

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

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

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

(5) Formation of Anticorrosion Treatment Layer Containing Cr For all the Examples 1 to 23 and Comparative Examples 1 to 9, after the formation of the heat resistance treatment layer, the chromium plating treatment conditions shown below on this heat resistance treatment layer The rustproofing treatment layer (Cr adhesion amount: 0.02 mg / dm ² ) was formed by treatment with
<Chromium plating conditions>
(Chrome plating bath)
Chromic anhydride CrO3 2.5 g / L
pH 2.5
Current density 0.5A / dm ²
Temperature 15-45 ° C
1 second to 2 minutes

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

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

<Tensile strength>
The surface-treated copper foils of all 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 12.7 × 130 mm and The tensile strength of the copper foil in the normal state was measured by an 1122 tensile tester. Moreover, after heating the copper foil cut out to 12.7x130 mm at 220 degreeC for 2 hours and naturally cooling to normal temperature, the tensile strength after heating was similarly measured. The measurement conformed to IPC-TM-650. The results are shown in Table 4.

<Expansion area ratio>
The surface shape of each of the surface-treated copper foils of Examples 1 to 23 and Comparative Examples 1 to 9 obtained by the above treatments (1) to (5) was measured using WykoContour GT-K manufactured by BRUKER, and shape analysis was performed. And the developed area ratio (Sdr) was determined. Shape analysis uses a high resolution CCD camera with VSI measurement method, the light source is white light, measurement magnification is 10 times, measurement range is 477 μm × 357.8 μm, Lateral Sampling is 0.38 μm, speed is 1, Backscan is 5 μm, Length is It was performed under the conditions of 5 μm and Threshold of 5%, and data processing was performed after filtering processing of TermsRemoval. The results are shown in Table 4.

<Yxy color system>
In the Yxy color system of the copper foils of all of Examples 1 to 23 and Comparative Examples 1 to 9 obtained by the above treatments (1) to (5), Y, x, y were measured using a color meter SM-T 45 (Suga Test Instruments Can be measured using a 45.degree. Illumination 0.degree. Light reception, a light source C light double field of view (halogen lamp). The results are shown in Table 4.

<Pinhole>
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) are cut into a size of 200 mm × 200 mm, and pinholes are marked by a light transmission method. did. The diameter of five surface-treated copper foils (total 0.2 m ² ) of 200 mm × 200 mm size was confirmed with an optical microscope, and holes of 30 μm or more were counted as pinholes. The pinholes observed by an optical microscope are either circular or irregular, and in each case, the major diameter of the pinhole (the distance between two points farthest apart on the outer periphery of the pinhole) was measured as the diameter. The result of calculating the number (pieces / m ²⁾ of pinholes per unit area (m ²⁾ based on the number of the resulting pinhole shown in Table 4.

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

  If the etching factor is small, the verticality of the side walls in the wiring pattern is broken, and in the case of a fine wiring pattern having a narrow line width, there is a risk of disconnection. In this example, the bottom width and the top width were measured with a microscope to calculate the etching factor with respect to the pattern at the just-etched position (the resist end and the bottom of the copper foil pattern are aligned). 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 shots of laser drilling were performed with a CO 2 laser drilling machine, and the number of holes opened was counted. Table 4 shows the number of openings for irradiation with a constant irradiation time of 10 msec for the cases of the irradiation energy of 50 W and 8 W. Even in the case of 8 W where the irradiation energy is low, those with a small decrease in the numerical aperture can be evaluated as having high laser processability.

<Handling property: number of wrinkles defects>
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) are cut into a size of 200 mm × 200 mm, and the surface-treated copper foil and the substrate FR4 Heat and pressure bond at 170 ° C and 1.5MPa (pressure) for 1 hour, prepare 30 substrates, check the wrinkles visually and count the wrinkled substrates as 1 wrinkle defect Table 4 shows the number of wrinkle defects that occurred. This evaluated the handling property of surface-treated copper foil.

  As can be seen from Table 4, all Examples 1 to 23 have a tensile strength of 400 to 700 MPa, a tensile strength of 300 MPa or more after heating at 220 ° C. for 2 hours, a foil thickness of 7 μm or less, and a laser irradiated surface The development area ratio (Sdr) of the glass satisfies 25 to 120%, and 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 is understood that the number of defects is 3 or less, the number of pinholes is small, the laser processability is excellent, and the handleability is also excellent.

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

  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 generated when the irradiation energy is 8 W is shown in the graph of FIG. The As clearly shown in FIG. 3, the surface-treated copper foil of the example has a large numerical aperture, is less likely to generate 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 occurrence of pinholes is large and the laser processability is inferior.

  Moreover, based on said evaluation result, the graph of FIG. 3 showed the relationship between the tensile strength in the normal state, and the generation number of a pinhole about the surface-treated copper foil of Examples 1-21 and Comparative Examples 1-9. As clearly shown in FIG. 3, the surface-treated copper foil of the example has a large numerical aperture, is less likely to generate 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 occurrence of pinholes is large and the laser processability is inferior.

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 The potential for industrial use is high.

101 Deposited copper foil 102 drum 103 buff apparatus 105 cathode reduction apparatus 106 electrolyte

Claims (4)

  A surface-treated copper foil for circuits processed by direct laser processing, which has a tensile strength of 400 to 700 MPa in a normal state, a tensile strength of 300 MPa or more measured at normal temperature after heating at 220 ° C. for 2 hours, and a foil thickness 7 μm or less, developed area ratio (Sdr) of at least one surface is 25 to 120%, and Y is 25.0 to 65.5%, x is 0.30 to 0.48% in the Yxy color system for the laser irradiated surface Surface treated copper foil for circuits having 0.28 to 0.41%. The surface-treated copper foil for a circuit according to claim 1 , wherein the number of pinholes having a diameter of 30 μm or more is 20 or less per m ² . The surface-treated copper foil for a circuit according to claim 1 , wherein the number of pinholes having a diameter of 30 μm or more is 10 / m ² or less. The copper clad laminated board which has a surface-treated copper foil for circuits of any one of Claims 1-3 , and has an insulating substrate in the surface at the side of the roughening process layer of this surface-treated copper foil.

Images