TW201903212A - Surface treated copper foil and copper clad laminate using the same - Google Patents

Abstract

Provided is a surface-treated copper foil which has fine line-to-line spaces or line widths, has excellent etching properties, laser processability, and thin foil handling properties, and has less pinholes and a higher tensile strength. This surface-treated copper foil has a tensile strength of 400-700 MPa, a tensile strength of 300 MPa or more after heating at 220 DEG C for 2 hours, a foil thickness of 7 [mu]m or less, a developed area ratio (Sdr) of one side thereof being 25-120%, and the number of pinholes with a diameter of at least 30 [mu]m being 20/m2 or less.

Description

Surface-treated copper foil and copper-clad laminated board using the same

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

The printed wiring board is placed on the surface of an electrically insulating substrate made of glass epoxy resin, polyimide resin, or the like, and a thin copper foil for forming a surface circuit is placed thereon, followed by heating and pressing to produce a copper-clad laminated board . Next, through-hole openings and through-hole plating are sequentially performed on the copper-clad laminated board, and then the copper foil of the copper-clad laminated board is etched to form a desired line width and a required distance between lines. Wiring pattern. Finally, the following processes are performed, that is, solder resist coating, exposure, through-hole plating, or removal of unhardened solder resist by caustic soda, etc. in order to expose the plating of the connection part of the electronic part, and other finishing deal with.

The copper foil used at this time is usually an electrolytic copper foil obtained by the following method, that is, the copper foil 101 is precipitated to a drum 102 using an electrolysis device shown in FIG. The copper foil 101 is peeled. The electro-decomposed starting surface (glossy surface, hereinafter referred to as the S surface) peeled from the drum 102 is relatively smooth, and the electro-decomposed end surface (rough surface, hereinafter referred to as M surface) as the opposite surface generally has unevenness. In general, the M surface is roughened to improve the adhesion to the substrate resin.

Recently, in the industry, a roughened surface of copper foil is previously bonded with an epoxy resin, such as an epoxy resin, so that the adhesive resin becomes a semi-hardened (B-stage) insulating resin layer, and a copper foil with resin is made. The resin-coated copper foil is used as a copper foil for forming a surface circuit, and a side of an insulating resin layer of the copper foil is thermocompression-bonded to a substrate (insulating substrate) to manufacture a printed wiring board, particularly an additional wiring board. For this additional wiring board, it is expected that various electronic components will be highly integrated. Correspondingly, high density is also required for wiring patterns. Therefore, wiring patterns that require fine line widths and space between lines have gradually become so-called Fine pattern printed wiring board. For example, as multilayer substrates used in servers, routers, communication base stations, and vehicle-mounted substrates, or multilayer substrates for smartphones, high-density ultra-fine wiring with a line width and a line spacing of about 15 µm are required. Printed wiring board.

With the increase in the density and miniaturization of such wiring substrates, it has become increasingly difficult to form fine circuits using the subtractive method, and instead, it has gradually changed to the modified semi-additive process (MSAP method). law)). In the MSAP method, an ultra-thin copper foil is formed on a resin layer as a power supply layer, and then pattern copper plating is performed on the ultra-thin copper foil. Next, the ultra-thin copper foil is removed by rapid etching, thereby forming a desired wiring.

In the MSAP method, a thin copper foil with a carrier is usually used. The thin copper foil with a carrier is used as follows: a peeling layer and a thin copper foil are sequentially formed on one side of a copper foil (carrier copper foil) as a carrier, and the surface of the thin copper foil becomes a roughened surface. Then, after the roughened surface is superposed on the resin substrate, the whole is subjected to thermocompression bonding, and then the carrier copper foil is peeled off and removed to expose the bonding side of the thin copper foil and the carrier copper foil, and the bonding side is exposed. A predetermined wiring pattern is formed.增 In order to increase the interlayer connection in the wiring substrate, a hole called a through hole is opened. In most cases, the opening is performed by irradiating laser light. In addition, in the MSAP method, a method called direct laser processing is adopted in which a copper foil is directly perforated with a resin by irradiating laser light directly to the copper foil.

The adhesive surface of the copper foil with a carrier used in the MSAP method to the resin substrate is usually M surface, the laser processed surface (S surface) is smooth and the laser absorptivity is not sufficient. Therefore, it is used as a pretreatment for laser processing. A brown treatment (etching roughening treatment) is necessary. Therefore, in Patent Document 1, a copper foil is proposed. In order to improve the laser processability of the S surface, a laser absorbing layer made of chromium, cobalt, nickel, iron, or the like is provided on the laser processed surface to perform laser processing. Sex is good. However, the thin copper foil of the copper foil with a carrier is manufactured using a common copper sulfate bath plating bath, and there is a problem that a large number of pinholes are generated.

In addition, Patent Document 2 proposes a copper foil in which pinholes are suppressed by uniformly forming a nickel and zinc chromate layer as an intermediate layer. However, since the intermediate layer (release layer) is formed on the glossy surface of the carrier foil, the intermediate layer irradiated with laser light after peeling the carrier foil is smooth and difficult to absorb laser light, and the laser processability is poor. In addition, since it is a copper foil with a carrier, there is a problem that labor and time are required to peel off the copper foil with a carrier, and operability is poor.

Patent Document 3 proposes a copper foil with a carrier, which has improved laser processability and etchability by suppressing variations in the roughness of the intermediate layer side of the thin copper foil. However, the thin copper foil of the copper foil with a carrier is manufactured using a common copper sulfate bath plating bath, and there is a problem that a large number of pinholes are generated. [Prior Art Literature] (Patent Literature)

Patent Document 1: Japanese Patent Application Publication No. 2013-75443 443 Patent Document 2: International Publication No. 2015/030256 Patent Document 3: Japanese Patent Application Publication No. 2014-208480

[Problems to be Solved by the Invention] The copper foil with a carrier is used in the MSAP method, but the copper foil with a carrier has the following problems.多 There are many pinholes, which reduces the manufacturing yield.中间 After peeling off the carrier foil, the intermediate layer exposed to laser light is smooth and difficult to absorb laser light, and the laser processability is poor. Therefore, as a pretreatment for laser processing, a brown oxidation treatment (etching roughening treatment) is necessary.剥离 The peeling step of the carrier foil takes labor and time to increase the manufacturing cost. Because of this problem, a new material is desired to replace the copper foil with a carrier. In view of these problems to be solved, the object of the present invention is to provide a surface-treated copper foil, which has a high tensile strength in normal state and after heating. Even a thin foil without a carrier foil does not cause wrinkles, and can be applied to The MSAP method is excellent in laser processability (direct laser processing), etching properties, and thin foil operability, and has fewer pinholes, making it suitable for high-density wiring circuits. [Technical means to solve the problem]

The present inventors have made diligent research repeatedly, and in the process, found that the roughened surface with "Sdr of 25% to 120%" is suitable for direct laser processing. In addition, it was found that the surface-treated copper foil of the present invention has a tensile strength of 400 MPa to 700 MPa under normal conditions, and after being heated at 220 ° C for 2 hours, the tensile strength measured at normal temperature is 300 MPa or more, and the foil thickness is Surface-treated copper foil below 7 µm, and the spread area ratio (Sdr) of at least one side is 25% to 120%, and the number of pinholes with a diameter of 30 µm or more is 20 / m ² or less. Etching, laser The present invention has been completed on the basis of this knowledge that it is excellent in workability (direct laser processing) and thin foil operability, and has few pinholes, and is suitable for high-density wiring circuits.

In the present invention, the normal state refers to a state where the surface-treated copper foil has not been subjected to a thermal history such as heat treatment, and is left at room temperature (= about 25 ° C). The tensile strength under normal conditions can be measured by IPC-TM-650 at room temperature. In addition, the tensile strength after heating can be measured after the surface-treated copper foil is heated to 220 ° C. for 2 hours, and then naturally cooled to room temperature.

If the tensile strength in the normal state is 400 MPa to 700 MPa, the operability and etching properties are good. If the tensile strength in the normal state is less than 400 MPa, wrinkles may be generated during the transportation of thin foil products. Therefore, the handleability is poor. If the tensile strength is more than 700 MPa, it is easy to cause the foil to break during the production by the precipitation of the roller, which is not suitable for manufacturing. When the tensile strength measured at room temperature after heating is 300 MPa or more, the crystal grains are also fine and the etchability is good after heating in the substrate lamination step. If the tensile strength after the same heating is 300 MPa or less, crystal grains become large, and it is difficult to dissolve by etching, so the etching properties are deteriorated.

The thickness of the surface-treated copper foil is 7 µm or less, or 6 µm or less. If the thickness of the surface-treated copper foil exceeds 7 µm, the opening degree of a laser using a low energy tends to deteriorate. If the surface-treated copper foil has a foil thickness of 7 µm or less, especially 6 µm or less, there is a tendency that the laser processability, particularly the processability in low-energy laser irradiation of about 8 W, becomes high.

In the present invention, the foil thickness refers to the formation of a laser absorbing layer, a roughening treatment layer, a nickel layer, a zinc layer, and chromic acid, as needed, for a copper foil manufactured by electrolysis as described later. The film thickness in the first stage after laser processing after surface treatment such as salt treatment and formation of silane coupling layer. The foil thickness can be measured in the form of mass thickness by an electronic balance.

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

The so-called spreading area ratio (Sdr) refers to the ratio of the surface area that is increased according to the surface property state based on the ideal surface having the size of the measurement area as a reference, and is defined by the following formula.

Here, x and y in the formula are plane coordinates, and z is a coordinate in the height direction. z (x, y) represents the coordinate of a point, and the coordinate is differentiated to thereby become the slope of the coordinate point. In addition, A is the planar area of the measurement area. The developed area ratio (Sdr) can be determined by measuring and evaluating the unevenness on the surface of the copper foil using a three-dimensional white interference microscope, a scanning electron microscope (SEM), an electron beam three-dimensional roughness analyzer, and the like. Generally, Sdr has nothing to do with the change in surface roughness Sa, but it tends to increase if the spatial complexity of the surface property state increases.

Here, the principle of direct laser processing will be described. If the reflectance on the surface of the copper foil is r, the absorptivity is µ, and the transmittance is τ, the following formula is established. r + µ + τ = 1 In direct laser processing, for copper foils, such as laser light that becomes τ = 0, usually a CO ₂ gas laser, etc., the above formula becomes r + µ = 1. In addition, when the intensity of the laser light is absorbed in a uniform distribution, if the beam radius is set to a, the temperature distribution on the central axis (Z axis) of the beam is expressed by the following formula.

Here, x and y in the formula are plane coordinates, and z is a coordinate in the height direction. In addition, the laser power absorbed by P is [J / s], the thermal diffusivity of x is K / ρ ･ C [cm ² / S], the thermal conductivity of K is [J / cm ･ s ･ K], and ρ is Density [g / cm ³ ], C specific heat [J / g ･ K], t series laser irradiation time [s], a series beam radius [cm]｡ temperature rises with time, but within a certain time Saturated, the temperature at this time is shown by the following formula.

It can be known from the above formula that the greater the energy of the laser light absorbed by the surface of the copper foil, the higher the temperature. The reason is that the energy of the laser light absorbed causes the atomic vibration to be amplified and converted into heat. In direct laser processing, the thermal energy is used to melt the copper foil at the laser irradiation site and perform hole processing. In order to improve the accuracy and efficiency of direct laser processing, as can be seen from the above formula, it is necessary to reduce the reflectance on the copper foil surface or increase the absorption rate.

In the previous MSAP method, the absorptivity of the copper surface after the carrier foil was peeled was low. Therefore, the surface was roughened by the brown oxidation treatment to increase the absorptivity, which corresponds to the direct laser processing, but because the brown oxidation treatment step cost Labor is problematic from the viewpoint of manufacturing costs. Therefore, after repeated efforts, it was found that by setting the spread area ratio (Sdr) of at least one side of the copper foil to 25% to 120%, the direct laser processing can be improved when the surface is set as the laser irradiation surface. Sex. If it is set that the surface of Sdr is 25% to 120%, a highly complicated uneven shape is formed at 1 µm or less. When a copper foil having such a shape is irradiated with a laser, the diffuse reflection increases, whereby the absorption rate of the laser light increases. In addition, it is considered that an oxide film is formed by activating the outermost layer of the copper foil by a highly complicated surface uneven shape, thereby reducing the reflectance and reducing the thermoelectric conductivity by increasing the surface area of the oxide film layer. Compared with the temperature rise of a laser light irradiation part, direct laser processability improves by this. When the Sdr of the laser-machined surface is less than 25%, the reflectance is high and the absorption rate of the laser light is poor. Therefore, the laser absorptivity tends to deteriorate. In addition, if Sdr is greater than 120%, a defect that the molten copper fills the hole again is likely to occur, and laser processability is deteriorated.

In addition, it is known that when a copper foil is used as a thin foil, if pinholes occur, the performance of a circuit board is reduced. However, in the present invention, a copper foil having a pinhole having a diameter of 30 µm or more and 20 pinholes / m ² or less can be obtained. , Can suppress the performance of the circuit substrate from being reduced.

The number of pinholes is a copper foil cut to a suitable size, for example, 200 mm × 200 mm. For example, after pinholes are marked with the light penetration method, the diameter is confirmed with an optical microscope, and holes with a diameter of 30 µm or more are calculated. The number of pinholes per unit area (m ² ) can be calculated based on the number of pinholes obtained (number / m ² ). [efficacy]

According to the present invention, it is possible to provide a copper foil having excellent etching properties, laser processability, thin foil operability, and pinhole resistance. In addition, it is possible to provide a surface-treated copper foil that has high tensile strength in normal state and after heating, so that it can be applied to the MSAP method even without a carrier copper foil.

The spread area ratio (Sdr) of the surface-treated copper foil of the present invention is 25% to 120%, but if the spread area ratio (Sdr) is 30% to 80%, there is a tendency that the laser processability is further improved. In addition, when the thickness of the surface-treated copper foil is 7 µm or less, especially 6 µm or less, the spread area ratio (Sdr) is preferably 30% to 80%, and the number of pinholes with a diameter of 30 µm or more is 10 holes / m. ² or less. When the number of pinholes with a diameter of 30 µm or more exceeds 10 holes / m ² , the performance tends to decrease when applied to a circuit board.

In the surface-treated copper foil of the present invention, it is preferable that the laser-processed surface in the Yxy color system is that Y becomes 25.0% to 65.5%, x becomes 0.30% to 0.48%, and y becomes 0.28% to 0.41%. The laser processed surface of the surface-treated copper foil satisfies the above-mentioned spreading area ratio (Sdr), and further, the processed surface in the Yxy color system Y is 25.0% to 65.5%, x is 0.30% to 0.48%, and y is 0.28%. In the range of 0.41%, laser absorptivity becomes better, and laser processability is very good.

The Yxy color measurement system can be measured using, for example, a colorimeter in accordance with JIS Z 8722.

As described above, the copper foil used in the MSAP method has an M-side adhered surface to the resin substrate, the laser-processed surface is smooth and the laser absorptivity is not sufficient. Therefore, brown oxidation is performed as a pre-treatment for laser processing. (Etching roughening treatment). In the present invention, the laser processability can be improved even if the brown oxidation treatment is not performed.

Hereinafter, conditions and methods for producing the surface-treated copper foil of the present invention will be described. (1) Production of electrolytic copper foil The copper foil in the present invention is produced, for example, by using a sulfuric acid-copper sulfate aqueous solution as an electrolytic solution and coating the copper foil with a platinum group element or an oxide element thereof. The electrolytic solution is supplied between an insoluble anode made of titanium and a titanium cathode drum arranged opposite to the anode. While rotating the cathode drum at a fixed speed, a DC current is applied between the two poles, so that copper is deposited on the surface of the cathode drum. The precipitated copper was torn off from the surface of the cathode drum and continuously wound.

In the present invention, it is preferable to produce the electrolytic copper foil in such a manner that the precipitation potential of copper in the surface of the cathode drum is uniform and unchanged. For this purpose, for example, a method of making a foil in a state where an oxide film does not exist on the surface of a titanium roller is mentioned. As an example, a cathodic reduction step may be used. As shown in FIG. 1, in the conventional manufacturing apparatus of electrolytic copper foil, the electrolytic drum 102 serving as a cathode is polished by a polishing wheel 103, thereby removing the oxide film generated on the surface of the drum. In contrast, the cathodic reduction step refers to, for example, the polishing wheel 103 instead of the precipitation device of the electrolytic copper foil of FIG. 1, as shown in the precipitation device of the electrolytic copper foil of FIG. 2. ) 106, the step of removing the oxide film. By removing the oxide film by the drum 102 and the cathode reduction device 105, it is expected that the initial precipitation of copper will occur uniformly on the surface of the titanium drum and reduce pinholes. In the previous manufacturing of copper foil using a titanium roller shown in FIG. 1, because the thickness of the titanium oxide film on the surface of the titanium roller is uneven, the precipitation of copper is located within the surface of the roller. If it is made into a thin foil, It is easy to produce pinholes. By using a cathodic reduction step, the cathodic reduction current density is increased, and pinholes can be reduced. The reason is that it can be considered that the reduction of the titanium oxide proceeds with the increase of the reduction current density of the cathode, and there is no unevenness in the distribution of the precipitation potential of copper on the surface of the titanium drum, so that pinholes can be suppressed.

When producing electrolytic copper foil, as an additive to the electrolytic solution, ethylene thiourea, polyethylene glycol, tetramethylthiourea, polypropylene amidamine, and the like can be added. By increasing the amount of ethythiourea and tetramethylthiourea, the tensile strength under normal conditions and the tensile strength after heating can be increased. If the tensile strength in the normal state is 400 MPa to 700 MPa, the operability and etching properties are good. If the tensile strength in the normal state is less than 400 MPa, the workability is poor, and if it is more than 700 MPa, it is easy to cause the foil to break and it is not suitable for manufacturing. In addition, after heating at 220 ° C for 2 hours, when the tensile strength measured at normal temperature was 300 MPa or more, the crystal grains were also fine and the etchability was good after heating in the substrate laminate. If the tensile strength after heating measured in the same manner is 300 MPa or less, the crystal grains become large, and it is difficult to dissolve by etching, so the etching properties are deteriorated.

(2) Surface treatment of copper foil <Laser absorbing layer forming treatment> (2) Next, the copper foil obtained above is subjected to a surface treatment to form a laser absorbing layer. In the present invention, a rugged plating layer is formed on one surface of the copper foil by a pulse current. This surface becomes a laser-machined surface when a copper foil is used to make a circuit by the MSAP method. The formation surface of the laser absorbing layer may be the precipitation start surface (S surface) or the precipitation end surface (M surface) in the electrolytic copper foil manufacturing step. Generally, the surface (roughened surface) to be bonded to the resin substrate is set to the M surface and the laser processed surface is set to the S surface. However, in the present invention, the surface to be bonded to the resin substrate may also be set to The roughened surface of the S surface was set as the M surface. That is, the roughened layer can be formed by electrolysis of the starting surface (S surface) during the manufacturing process of the electrolytic copper foil.

In the present invention, it has been found that direct laser processing can be achieved without performing a brown oxidation treatment by having a moderate surface area such that the development area ratio of the M-plane or S-plane that becomes the laser-machined surface becomes 25% to 120%. In addition, by forming the roughened layer by electrolysis of the starting surface during the electrolytic copper foil manufacturing process, the etching factor can also be improved.

As a composition of a plating bath for forming a laser absorption layer, copper sulfate pentahydrate, sulfuric acid, hydroxy ethyl cellulose (HEC), polyethylene glycol (PEG), and thiourea can be added. Wait. By applying a positive pulse current with a different current value in two stages, the acting additive changes according to the corresponding precipitation potential in the two stages, and a complex uneven shape can be formed. Thereby, a precipitation surface excellent in laser absorptivity can be obtained. Specifically, in the step-like pulse current of the current value (Ion1) at stage 1> 2 (Ion2), if the current value at stage 1 (Ion1) or the time at stage 1 (ton1) is increased, The tendency of Sdr to increase on the M side. By applying such two-stage pulse current at a fixed time interval (toff), a surface shape having an Sdr value with good laser processability can be obtained.

When the Sdr is in the range of 25% to 120%, the laser processability is improved. This 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 absorbency is increased. If Sdr is less than 25%, laser light absorption is poor, and laser processability is poor. If Sdr is greater than 120%, the absorption rate of light with a wavelength of CO ₂ laser is reduced, and laser processability is reduced. In addition, if the time interval (toff) of the pulse current is increased, Y decreases in the Yxy color system. If 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, the laser processability is good. If Y is less than 15% or more than 85%, there is a tendency that laser processability is reduced. When Sdr is increased, the number of laser openings tends to increase, and as the Y value decreases, the number of laser openings tends to increase. If the Sdr of the laser irradiation surface is 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%, then the laser is Workability is particularly good.

<Forming a roughening treatment layer> A roughening treatment layer having a fine uneven surface is formed by electrodeposition of fine copper particles on a surface of a copper foil opposite to the laser-machined surface. The roughened layer is formed by electroplating, and it is preferable to add a chelating agent to the plating bath, and the concentration of the chelating agent is preferably 0.1 g / L to 5 g / L. Examples of the chelating agent include DL-malic acid, EDTA (ethylene diamine tetraacetic acid) sodium solution, sodium gluconate, and diethylene triamine pentaacetic acid (DTPA) pentasodium And so on.

In the electrolytic bath, copper sulfate, sulfuric acid, and molybdenum can also be added. By adding molybdenum, etching properties can be improved. Generally, at a copper concentration of 13 g / L to 72 g / L, a sulfuric acid concentration of 26 g / L to 133 g / L, a liquid temperature of 18 ° C to 67 ° C, and a current density of 3 A / dm ² to 67 A / Electrodeposition was performed under conditions of dm ² and treatment time of 1 second to 1 minute and 55 seconds.

<Formation of a nickel layer, a zinc layer, and a chromate-treated layer> (1) In the present invention, it is preferable to form a nickel layer and a zinc layer sequentially on the roughened surface. The zinc layer functions to prevent deterioration of the substrate resin due to the reaction between the thin copper foil and the substrate resin and oxidation of the surface of the thin copper foil when the thin copper foil is thermally bonded to the resin substrate. Improve the bonding strength with the substrate. In addition, the nickel layer functions as a base layer of the zinc layer to prevent the zinc of the zinc layer from thermally diffusing to the side of the copper foil (electrolytic copper plating layer) during thermal compression bonding to the resin substrate, thereby making the zinc layer The above functions are effectively performed. Furthermore, these nickel layers and zinc layers can be formed by applying a known electrolytic plating method or an electroless plating method. The nickel layer may be formed of pure nickel or may be formed of a phosphorus-containing nickel alloy.

In addition, if the surface of the zinc layer is further subjected to a chromate treatment, an oxidation resistant layer is formed on the surface, which is preferable. As the chromate treatment to be applied, a known method may be used, and for example, the method disclosed in Japanese Patent Application Laid-Open No. 60-86894 may be mentioned. By attaching chromium oxides and hydrates thereof having a chromium content of about 0.01 mg / dm ² to about 0.3 mg / dm ² , it is possible to impart excellent rust preventive ability to copper foil.

<Silane treatment> In addition, if the chromate-treated surface is further treated with a silane coupling agent, the copper foil surface (the surface on the bonding side with the substrate) will be given a strong affinity to the adhesive. Functional group, so the bonding strength between the copper foil and the substrate is further improved, and the rust resistance and moisture absorption and heat resistance of the copper foil are further improved, which is preferable.

Examples of the silane coupling agent include vinyl-based silane, epoxy-based silane, styryl-based silane, methacryl-based silane, acryl-based silane, amine-based silane, urea-based silane, chlorine Propyl-based silanes, mercapto-based silanes, thioether-based silanes, isocyanate-based silanes, and the like. These silane coupling agents are usually made into an aqueous solution of 0.001% to 5%, and the aqueous solution can be applied to the surface of copper foil and then directly heated and dried. Furthermore, instead of a silane coupling agent, the manufacture of a copper-clad laminate using titanium (3)

(3) At the beginning of the manufacture of copper clad laminates, a copper foil surface (roughened surface) of a thin copper foil is placed on the surface of an electrically insulating substrate made of glass epoxy resin, polyimide resin, or the like, It is heated and pressed to produce a copper-clad laminated board with or without a carrier. Since the surface-treated copper foil of the present invention has high tensile strength in normal state and after heating, it can cope with it even without a carrier. Next, the surface of the copper-clad laminated sheet was irradiated with a CO ₂ gas laser to open a hole. In other words, a CO ₂ gas laser is irradiated from the surface of the surface-treated copper foil on which the laser-absorbing layer is formed, and a hole-cutting process is performed through the surface-treated copper foil and the resin substrate. [Example]

Hereinafter, the present invention will be described in detail by examples. (1) Manufacture of copper foil and formation of laser absorbing layer According to the cathode reduction steps of electrolytic solution, current density, and bath temperature shown in Table 1, and the steps of electrolysis based on the electrolytic conditions shown in Table 2, The electrolytic copper foils of Examples 1 to 21 and Comparative Examples 1 to 9. For these electrolytic copper foils, they were formed by electrolytic plating treatment under a plating bath having a composition shown in Table 3, a treatment surface, and electrolytic conditions (pulse width, current density, time, and bath temperature). Laser absorbing layer. In addition, in Example 22, a laser absorbing layer was formed by an alternating current, and in Example 23, a MECetchBOND CZ-8000 process was used to form a laser absorbing layer. Furthermore, under the electrolytic conditions in Table 3, Ion1 represents the pulse current density in the first stage, Ion2 represents the pulse current density in the second stage, ton1 represents the pulse current application time in the first stage, and ton2 represents the pulse in the second stage. Current application time, toff represents the time when the current between the pulse current in the second stage and the pulse current in the first stage is set to 0. In addition, the formation surface of the laser absorbing layer is the surface opposite to the roughened surface shown in Table 4, and was formed on the M surface in Examples 1 to 19, 22 to 23, and Comparative Examples 4, 6 to 8. The laser absorbing layer (roughening the S surface). In Examples 20 and 21 and Comparative Example 9, a laser absorbing layer was formed on the S surface (roughening the M surface). Comparative Examples 1 to 3 and 5 did not form a laser absorbing layer.

[Table 1]

[Table 2]

[table 3]

(2) Roughening treatment Secondly, on the surface on the opposite side of the laser absorbing layer (the roughening treatment surface shown in Table 4), a roughening treatment layer having a fine uneven surface is formed by electrodeposition of roughened particles. In all the examples and comparative examples, the roughened surface plating process was performed in the order shown below to form a roughened layer. (Rough surface plating) Copper sulfate: 13 g / L to 72 g / L based on Cu concentration Sulfuric acid concentration: 26 g / L to 133 g / L DL-malic acid: 0.1 g / L to 5.0 g / L Liquid temperature: 18 ° C to 67 ° C Current density: 3 A / dm ² to 67 A / dm ² Processing time: 1 second to 1 minute 55 seconds

(3) Formation of nickel-containing base layer For all of Examples 1 to 23 and Comparative Examples 1 to 9, after forming the roughened layer described above, electrolysis was performed on the roughened layer under the nickel plating conditions shown below. Plating was performed to form a base layer (the adhesion amount of nickel was 0.06 mg / dm ² ). <Nickel plating conditions> Nickel sulfate: 5.0 g / L ammonium persulfate 40.0 g / L boric acid 28.5 g / L converted to nickel metal Current density 1.5 A / dm ² pH3.8 Temperature 28.5 ℃ Time 1 second to 2 minutes

(4) Formation of zinc-containing heat-resistant treatment layer For all of Examples 1 to 23 and Comparative Examples 1 to 9, after the above-mentioned base layer was formed, electrolytic plating was performed on the base layer under the zinc plating conditions shown below. Thus, a heat-resistant treatment layer was formed (zinc adhesion amount: 0.05 mg / dm ² ). <Galvanizing conditions> Zinc sulfate heptahydrate 1 g / L to 30 g / L Sodium hydroxide 10 g / L to 300 g / L Current density 0.1 A / dm2 to 10 A / dm ² Temperature 5 ° C to 60 ° C Time 1 second to 2 minutes

(5) Formation of a chromium-containing rust-preventive treatment layer For all of Examples 1 to 23 and Comparative Examples 1 to 9, after forming the heat-resistant treatment layer, the heat-resistant treatment layer was subjected to the chrome-plating treatment conditions shown below. This process forms an anti-rust treatment layer (the amount of chromium attached: 0.02 mg / dm ² ). <Chrome plating conditions> (Chromium plating bath) Anhydrous CrO ₃ 2.5 g / L pH2.5 Current density 0.5 A / dm ² Temperature 15 ° C to 45 ° C Time 1 second to 2 minutes

(6) Formation of Silane Coupling Agent Layer For all of Examples 1 to 23 and Comparative Examples 1 to 9, after forming a rust-preventive treatment layer, apply a treatment solution on the rust-prevention treatment layer, and the treatment solution is based on silane The coupling agent aqueous solution is added with methanol or ethanol and adjusted to a predetermined pH. Thereafter, after keeping it for a predetermined time, it is dried with hot air to form a silane coupling agent layer.

(7) Evaluation method <Foil thickness> 测定 The surface treatments of all the Examples 1 to 23 and Comparative Examples 1 to 9 obtained by the above-mentioned treatments (1) to (5) were measured in the form of mass thickness by an electronic balance. The thickness of copper foil. The results are shown in Table 1.

<Tensile strength> 切 Cut all the surface-treated copper foils of Examples 1 to 23 and Comparative Examples 1 to 9 obtained by the above processes (1) to (5) into a size of 12.7 mm × 130 mm. The tensile strength of the copper foil under normal conditions was measured using a 1122 tensile tester test device of Instron. In addition, the copper foil cut into 12.7 mm × 130 mm was heated at 220 ° C. for 2 hours, and then naturally cooled to normal temperature. Thereafter, the tensile strength after heating was measured in the same manner. The measurement is based on IPC-TM-650. The results are shown in Table 4.

<Developed area ratio> For the surface-treated copper foils of Examples 1 to 23 and Comparative Examples 1 to 9 obtained by the above processes (1) to (5), the surface shape was measured using WykoContourGT-K from BRUKER Corporation. The shape analysis was performed to determine the developed area ratio (Sdr). The shape analysis is based on a VSI (vertical scanning interferometry) measurement method. A high-resolution CCD (charge coupled device) camera is used. The light source is white light, the measurement magnification is 10 times, and the measurement range is 477. µm × 357.8 µm, lateral sampling (LateralSampling) 0.38 µm, speed (speed) 1, backscan (backscan) 5 µm, length (length) 5 µm, threshold (Threshold) 5%, After the filtering process of the items removal (TermsRemoval), the data processing is performed. The results are shown in Table 4.

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

<Pinholes> The surface-treated copper foils of all of Examples 1 to 23 and Comparative Examples 1 to 9 obtained by the above processes (1) to (5) were cut to a size of 200 mm × 200 mm, and light was used. Penetration marks the pinhole. For 200 pieces of 200 mm × 200 mm surface-treated copper foil (0.2 m ² ), confirm the diameter with an optical microscope, and calculate a hole with a diameter of 30 μm or more as a pinhole. The pinholes observed with an optical microscope include circular pinholes and irregular pinholes, but the long diameter of the pinholes (the distance between the two points that are farthest apart on the outer periphery of the pinholes) are measured as the diameter. Based on the number of obtained pinholes, the number of pinholes per unit area (m ² ) (number / m ² ) was calculated. The results are shown in Table 4.

[Table 4]

<Etching factor> Next, on the surface-treated copper foils of Examples 1 to 23 and Comparative Examples 1 to 9 obtained by the above processes (1) to (6), a dry resist film was used, and Etch to form a resist pattern with a line / space of L & S = 100 µm / 200 µm. After etching the wiring pattern using copper chloride and hydrochloric acid as an etching solution, the etching factor was measured. The so-called etching factor (Ef) means that when the thickness of the surface-treated copper foil is set to H, the bottom width of the formed wiring pattern is set to B, and the top width of the formed wiring pattern is set to T, the following formula The value represented. Ef = 2H / (B-T)

If the etching factor is small, the verticality of the sidewalls in the wiring pattern collapses, and in the case of a fine wiring pattern with a narrow line width, there is a risk of disconnection. In this example, the bottom width and top width of the pattern at the appropriate etching (resist end aligned with the bottom of the copper foil pattern) position were measured with a microscope to calculate the etching factor. The results are shown in Table 4.

<Number of Laser Openings> Two pieces of the surface-treated copper foils of all the Examples 1 to 23 and Comparative Examples 1 to 9 obtained by the above processes were heated and pressure-bonded to both sides of the substrate FR4 to produce CCL (copper-clad Laminate). Next, a CO ₂ laser hole processing machine was used to perform 100 times of laser hole processing to calculate the number of openings. For the case where the irradiation energy is 50 W and the case where 8 W, the irradiation is performed for a fixed irradiation time of 10 msec, respectively. When the irradiation energy is low at 8 W, a sample with a small decrease in the number of openings can also be evaluated as a sample with high laser processability.

<Operability: Number of Wrinkle Defects> Cut all the surface-treated copper foils of Examples 1 to 23 and Comparative Examples 1 to 9 obtained by the above processes (1) to (5) into 200 mm × 200 mm Size, the surface-treated copper foil and the substrate FR4 were heated at 170 ° C and 1.5 MPa (pressure) for 1 hour, and pressure bonding was performed to produce 30 substrates. Wrinkles were visually confirmed, and the number of wrinkled substrates was calculated as the number of defective wrinkles. 1 Table 4 shows the number of occurrence of wrinkle defects. With this, the operability of the surface-treated copper foil was evaluated.

As can be seen from Table 4, in Examples 1 to 23, all tensile strengths were 400 MPa to 700 MPa, and the tensile strength after heating at 220 ° C for 2 hours was 300 MPa or more, the foil thickness was 7 µm or less, and laser irradiation The spread area ratio (Sdr) of the surface satisfies 25% to 120%. As shown in the evaluation results, it can be seen that the number of pinholes is 20 or less, Ef is 2.0 or more, the number of laser openings of 8 W is 90 or more, and the number of defective wrinkles is 3 Hereinafter, the number of pinholes is small, the laser processability is excellent, and the workability is also excellent.

In contrast, in Comparative Examples 1 to 9, the tensile strength is 400 MPa to 700 MPa, and the tensile strength after heating at 220 ° C for 2 hours satisfies 300 MPa or more. However, Comparative Examples 2, 3, 5 to 7, 9 However, the spreading area ratio (Sdr) of the laser irradiation surface did not satisfy 25% to 120%. Therefore, the number of laser openings of all 8 W was less than 90, and the laser opening properties were poor. In addition, in Comparative Examples 1 and 4, it was found that pinholes exceeded 20 due to the manufacturing conditions of the surface-treated copper foil, and Comparative Example 8 had a poor laser aperture because the foil thickness was 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 number of openings and the number of pinholes when the irradiation energy was 8 W is shown in the graph of FIG. 3. As is clear from FIG. 3, the number of openings of the surface-treated copper foil of the example is large, the number of pinholes is small, and the laser processability is excellent. In contrast, the number of openings of the surface-treated copper foil of the comparative example is small, or pinholes There are many occurrences, and laser processability is poor.

In addition, based on the above-mentioned evaluation results, the relationship between the tensile strength in the normal state and the number of pinholes produced in the surface treated copper foils of Examples 1 to 21 and Comparative Examples 1 to 9 is shown in the graph of FIG. 3. As is clear from FIG. 3, the number of openings of the surface-treated copper foil of the example is large, the number of pinholes is small, and the laser processability is excellent. In contrast, the number of openings of the surface-treated copper foil of the comparative example is small, or pinholes There are many occurrences, and laser processability is poor. [Industrial availability]

According to the present invention, it is possible to provide a surface-treated copper foil which has high tensile strength, finer inter-line or line width, excellent etching properties, laser processability, and thin foil operability, and has fewer pinholes, which is industrially feasible. High usability.

101‧‧‧precipitated copper foil

102‧‧‧Roller

103‧‧‧Polishing wheel device

105‧‧‧cathode reduction device

106‧‧‧ Electrolyte

FIG. 1 is a diagram showing a conventional precipitation device for electrolytic copper foil. FIG. 2 is a view showing a precipitation device of an electrolytic copper foil having a cathode reduction step. FIG. 3 is a graph showing the relationship between the number of laser openings and the number of pinholes in Examples and Comparative Examples. FIG. 4 is a graph showing the relationship between the normal tensile strength and the number of wrinkle defects in Examples and Comparative Examples.

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Claims (10)

A surface-treated copper foil having a tensile strength of 400 MPa to 700 MPa under normal conditions, and after being heated at 220 ° C for 2 hours, the tensile strength measured at normal temperature is 300 MPa or more, and the foil thickness is 7 µm or less, at least one side The spread area ratio (Sdr) is 25% to 120%. The surface-treated copper foil according to claim 1, wherein the number of pinholes with a diameter of 30 µm or more is 20 holes / m ² or less. The surface-treated copper foil according to claim 1 or 2, wherein the thickness of the aforementioned foil 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 any one of claims 1 to 4, wherein the number of pinholes having a diameter of 30 µm or more is 10 holes / m ² or less. The surface-treated copper foil according to any one of claims 1 to 5, wherein a roughened layer is formed on the starting surface by electrolysis during the manufacturing process of the electrolytic copper foil. A surface-treated copper foil for a circuit, which is a surface-treated copper foil for a circuit processed by direct laser processing, and has a tensile strength of 400 MPa to 700 MPa under normal conditions, and is heated at 220 ° C for 2 hours and then at room temperature. The measured tensile strength is 300 MPa or more, the foil thickness is 7 μm or less, the spread area ratio (Sdr) of at least one side is 25% to 120%, and the laser irradiation surface is in the Yxy color system, Y has 25.0% to 65.5%, x has 0.30% to 0.48%, and y has 0.28% to 0.41%. The surface-treated copper foil for a 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 a circuit according to claim 7, wherein the number of pinholes having a diameter of 30 µm or more is 10 / m ² or less. A copper-clad laminated board comprising the surface-treated copper foil according to any one of claims 1 to 6 or the surface-treated copper foil according to any one of claims 7 to 9, and on the surface The surface on the side of the roughened layer of the processed copper foil has an insulating substrate.