JP4471795B2 - Electrolytic copper foil manufacturing method and printed wiring board - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for producing an electrolytic copper foil, and in particular, an electrolytic copper that can provide an etching roughened electrolytic copper foil with stable adhesion to a printed circuit board by roughening the surface of the copper foil by chemical etching. The present invention relates to a method for manufacturing a foil.
Moreover, this invention relates to the printed wiring board which bonded the electrolytic copper foil manufactured with the said manufacturing method to the printed wiring board.

  Electrodeposited copper foil is usually made by performing electrodeposition and peeling while rotating a drum in a copper plating bath such as a copper sulfate bath using a drum made of Ti or the like as a cathode. The surface in contact with the copper foil drum is a shiny surface (hereinafter referred to as S surface), and the opposite surface is a mat surface (hereinafter referred to as M surface). The S surface is a so-called replica of the drum surface, and the shape of the drum surface is copied, but the M surface is manufactured in various sizes from smooth to uneven, depending on the type of copper plating bath and the electrolysis conditions. The produced electrolytic copper foil (untreated copper foil) is subjected to a roughening treatment such as copper on one side (usually the M side) mainly by a user's request, and a resin substrate (hereinafter sometimes referred to as a resin). Increases adhesive strength. Furthermore, for the purpose of preventing corrosion resistance and adhesion with the resin after roughening treatment, and preventing deterioration of contact resistance with metal paste in multilayer substrates, etc., plating with Ni, Cr, Zn, chromate treatment, organic rust prevention treatment, Silane treatment or the like is performed.

  Copper foils used for printed wiring boards are classified into two types according to their use. One is a copper foil as a so-called outer layer substrate that is used in a state where a circuit made of copper foil is exposed, and the copper foil for such use is subjected to surface treatment (roughening treatment) only on one side. . Two are copper foils that are sandwiched (embedded) between two substrates and are used as a so-called inner layer substrate. Both surfaces of the copper foil are in close contact with a resin or the like, so both surfaces are roughened. Has been.

  In recent years, the line / space width of a wiring circuit is becoming smaller due to high integration on a printed wiring board, and the stability of a circuit pattern during circuit formation by etching is becoming more important.

In addition to the thickness of the copper foil, the size, form, orientation, etc. of the copper foil crystal grains influence the stability of circuit formation by this etching. When large crystal grain interfaces are selectively etched, Since fine pattern formation becomes difficult, fine granular crystals are desired.
In addition, in the roughening treatment of the copper foil surface, the conventional electrodeposition roughening method deposits bump-like or beard-like precipitates on the surface in order to maintain the peel strength. There are problems such as copper bumps remaining in the insulating region) and it becomes difficult to form fine patterns.

In addition, since the width of the wiring circuit is narrowed, the contact area with the resin is also reduced, so there is a demand for improved adhesion strength. Adhesion strength is increased by increasing the amount of electrodeposition roughening and controlling the roughening shape. Is raised.
However, if the roughness is increased too much, the roughened film becomes powdery and falls off during the processing of the copper foil, which causes poor appearance and deterioration of electrical characteristics.
Also, from the viewpoint of high frequency characteristics, increasing the roughness results in a surface with a large amount of fine roughened particles adhering to it, and due to the skin effect, current concentrates on the roughened layer on the surface, and resistance at the grain boundary is reduced. It becomes larger and the impact is at a level that cannot be ignored.

Another method for improving the adhesion of copper foil to resin is called blackening treatment in which the surface of the copper foil is treated with a high-temperature strong alkaline solution to form fine acicular copper oxide on the surface of the copper foil. Processing is also performed.
However, the acicular copper oxide formed on the surface of the copper foil generates a so-called haloing phenomenon in which copper oxide is dissolved in an acidic plating solution when through-hole plating is performed in a subsequent process. Further, the blackening process has a problem that workability is poor and takes time. As a method for improving the haloing phenomenon, a method for reducing the dissolution while maintaining the shape after the blackening treatment has been proposed, but it is not desirable because the number of steps is further increased.

For this reason, as a method having a small number of steps and excellent productivity, a method of improving the adhesion to a resin by performing an etching roughening treatment has been studied.
As this etching roughening liquid, many liquids containing an inorganic acid or organic acid, an oxidizing agent and an additive have been proposed.
For example, Patent Document 1 discloses a corrosion inhibitor such as an inorganic acid + hydrogen peroxide + triazole + a surfactant. Patent Document 2 discloses an etching solution containing inorganic acid + peroxide + azole + halide.
Japanese Patent No. 2740768 JP-A-10-96088

However, even in the method using the etching solution, the adhesion between the copper foil and the resin substrate is often insufficient, and further improvement has been demanded.
As a result of intensive studies in view of the above problems, the present invention has succeeded in solving this problem by controlling the crystal grains of the electrolytic copper foil by a method different from the improvement from the etching solution, that is, by controlling the crystal grains. That is, a method for producing an electrolytic copper foil that increases the adhesion with a resin by chemically etching the surface of the electrolytic copper foil having granular crystals is provided, and a print using the electrolytic copper foil produced by the production method is provided. A wiring board is provided.

  In the present invention, if the crystal grain size in the chemical etching region of the electrolytic copper foil is too fine, appropriate roughening cannot be performed, and sufficient peel strength cannot be obtained. This is a method for producing an electrolytic copper foil in which the average value of the diameter is 0.3 μm or more and the surface of the copper foil having a crystal grain size of 0.3 μm or more is chemically etched.

  That is, the method for producing the electrolytic copper foil of the present invention comprises subjecting the electrolytic drum to a heat treatment in an atmosphere of 50 ° C. or higher by using the electrolytic drum as a cathode and depositing the copper foil on the electrolytic drum. At least one surface of the copper foil is a granular crystal, and an untreated copper foil having an average particle size of 0.3 μm or more in a region from the surface to at least the depth X is the granular crystal surface of the untreated copper foil. Is manufactured from the surface of the granular crystal to the depth X by chemical etching.

  In the present invention, it is preferable that crystal grains having a grain size of 1 μm or more are present in an area ratio of 10% or more in a region from the grained crystal surface of the untreated copper foil to a depth X to be chemically etched.

Moreover, in this invention, it is preferable to perform the heat processing of the said electrolytic copper foil on the conditions from which the LMP value shown to Formula 1 will be 7000 or more at 50 degreeC or more.
Formula 1: LMP = (T + 273) × (20 + Logt)
Here, T is temperature (° C.), and t is time (Hr).

  In the printed wiring board of the present invention, an electrolytic copper foil obtained by electrodepositing a copper foil on the electrolytic drum and forming a copper foil on the electrolytic drum is heat-treated in an atmosphere of 50 ° C. or more, and at least the electrolytic copper foil One surface is a granular crystal, and an untreated copper foil having an average particle size of 0.3 μm or more in an area from the surface to at least depth X is formed, and the granular crystal surface of the untreated copper foil is subjected to chemical etching. The wiring board is formed by etching from the surface of the granular crystal to the depth X to obtain a roughened copper foil, and the roughened surface of the roughened copper foil is bonded to a printed wiring board substrate.

  In the present invention, the crystal grain of the surface of the electrolytic copper foil to be chemically etched is made into a granular crystal, and the surface of which the crystal grain size is controlled is chemically etched to increase the adhesive force with the resin substrate and to provide an excellent peel. An electrolytic copper foil having strength can be produced, and an excellent printed wiring board using the electrolytic copper foil produced by the production method can be provided.

In the present invention, the surface of the untreated copper foil whose surface is chemically etched (at least the surface to be bonded to the substrate) is a crystal grain, and at least the depth X at which chemical etching is performed (hereinafter referred to as an etching region). The average particle size is 0.3 μm or more.
In the present invention, the crystal grains on the surface of the copper foil to be bonded to the resin substrate are granular crystals, and the size of the crystal grains is 0.3 μm or more. This is to provide excellent adhesive strength (peel strength). That is, if the crystal grains on the surface of the copper foil are granular crystals and the size of the crystal grains is 0.3 μm or less, when the copper foil surface is chemically etched, the grain boundaries are easy to dissolve as the crystals of the granular crystals are small. This is because the surface roughness (Rz) and the uniformity of the surface, which itself falls off and becomes a stable peel strength, cannot be obtained.
For this reason, in order to stabilize the peel strength of the granular crystal surface, the average crystal grain size of the granular crystal surface of the untreated copper foil subjected to chemical etching needs to be 0.3 μm or more.

  Depending on the resin forming the substrate, sufficient peel strength may not be obtained even if the above conditions are satisfied. Such a resin is preferably heat-treated so that crystal grains having a grain size of 1 μm or more are present in an area of 10% or more in the etching region of the copper foil. If crystal grains having a grain size of 1 μm or more exist in the etching region in an area ratio of 10% or more, the crystal grains are stable and uniform roughening is achieved, and at the same time the crystals are large. It is possible to prevent the grains themselves from falling off and increase Rz, to improve the peel strength, to improve the adhesive strength with the substrate, and to provide a more preferable electrolytic copper foil.

In the present invention, in order to produce an electrolytic copper foil having at least a surface composed of granular crystals and an average particle size of an etching region of 0.3 μm or more, electrolytic copper produced in an atmosphere having a heat treatment temperature of 50 ° C. or more Hold the foil. In particular, an excellent untreated electrolytic copper foil can be obtained by performing heat treatment at 50 ° C. or higher so that the LMP value shown in Formula 1 is 7000 or higher.
Formula 1: LMP = (T + 273) × (20 + Logt)
T is temperature (° C.), t is time (Hr)
Here, the heat treatment temperature is set to 50 ° C. or more in consideration of productivity, particularly heat treatment time, and an average crystal grain size of 0.3 μm or more is generated with granular crystals within a time suitable for industrial production. For this reason, it is necessary to set the temperature to 50 ° C. or higher.
Further, the LMP value is set to 7000 or more at a heating temperature and heat treatment time more industrially suitable, and at least an etching region (up to a depth X from the surface of the copper foil) is a granular crystal with an average crystal grain size of 0.00. It is for forming in copper foil of 3 micrometers or more.

  In the present invention, the average particle size of the granular crystals in the etching region on the bonding surface side with the substrate is preferably 0.3 μm or more in order to perform chemical etching roughening, and the average particle size is 0.3 μm. In the range of 3 μm or less, an appropriate roughened surface having a very uniform property can be obtained. If the particle size is 0.3 μm or less, the roughened film is liable to fail such as falling off into a powdery state, and cannot satisfy the Rz value where the uniformity and peel strength are stable. This is because each one becomes too large to be suitable for fine patterning.

  The copper foil before etching roughening (untreated copper foil) obtained in this way is subjected to chemical etching roughening at the time of bonding to the substrate, and if necessary, Ni, Zn, chromate, silane treatment, organic system Surface treatment such as rust prevention treatment is appropriately performed and bonded to the substrate to form a printed wiring board.

The electrolytic copper foil produced by the production method of the present invention can be provided for the outer layer or for the inner layer.
As the electrolytic copper foil for the outer layer, the copper foil is heat-treated to produce a granular crystal surface in the etching region with an average crystal grain size of 0.3 μm or more, and only one side is chemically etched to provide for the outer layer.
For the inner layer, the copper foil is heat-treated to produce a granular crystal surface in the etching region with an average crystal grain size of 0.3 μm or more, and both surfaces thereof are chemically etched and provided for the inner layer.
In order to manufacture an outer layer type wiring substrate, a printed wiring board can be manufactured by pasting the chemical etching treated surface of the outer layer electrolytic copper foil to the substrate and forming a predetermined wiring on the bonded copper foil.

On the other hand, in order to manufacture an inner layer type wiring substrate, an inner layer electrolytic copper foil is used, the electrolytic copper foil is bonded to the substrate, and a predetermined wiring is formed on the adhered copper foil. Next, another substrate is bonded to the exposed copper foil constituting the circuit to form an inner layer type printed wiring board.
In addition, as another method of manufacturing the inner layer type wiring board, an electrolytic copper foil for the outer layer is used, the one side chemical etching treatment surface is bonded to the substrate, the circuit is constituted, and the exposed surface is chemically etched to perform the etching. A substrate is further bonded to the surface to form an inner layer type wiring board.
As a further method of manufacturing inner layer type wiring boards, in applications where degradation of high frequency characteristics etc. is allowed to some extent, electrolytic copper foil for outer layers is used, and the surface that has been roughened by chemical etching is bonded to the substrate, and a predetermined circuit is formed. Constitute. A circuit structure with a fine pattern can be formed by first bonding the chemically etched surface to the substrate. Next, the exposed copper foil surface is subjected to electrodeposition roughening, and another substrate is bonded to the electrodeposition roughened surface to form an inner layer type wiring substrate. In this way, a fine pattern can be formed, and the second substrate can be firmly bonded by an electrodeposition process that produces a stronger peel strength than the chemical etching process.

  The crystal grain size was measured by EBSD (Electron Back Scattering Diffraction). The EBSD is an apparatus that can easily measure the distribution of crystal grains in the depth direction from the copper foil surface.

The etching roughening solution for chemically etching the etching roughening copper foil of the present invention is not particularly limited, and any known etching solution (bath) may be used. Usually, it is a liquid in which an additive such as a chelating agent is added to an acid and an oxidizing agent, and those that preferentially dissolve copper crystal grain boundaries are preferred. For example, in addition to the etching roughening solution disclosed in Patent Documents 1 and 2, commercially available products such as CZ-8100 and 8101 of MEC Co., Ltd. and CPE-900 of Mitsubishi Gas Chemical Co., Ltd. can be used. .
The chemical etching roughening depth X of the present invention is selected depending on the type of resin to be bonded to the copper foil surface, and the depth X is preferably an etching amount that reaches a depth of about 0.5 to 3 μm from the surface. . If the depth of dissolution is less than 0.5 μm, a sufficiently rough surface cannot be obtained. On the other hand, if it exceeds 3 μm, no improvement in adhesion to the resin can be expected. This leads to an increase.

  The roughened chemical etching surface of the electrolytic copper foil produced according to the present invention has deep irregularities formed uniformly, and has a surface excellent in adhesion to the resin. For example, when a multilayer printed circuit board is manufactured by adopting the method for manufacturing an electrolytic copper foil of the present invention, a copper foil (untreated copper foil) that has been heat-treated and made into a granular crystal of a predetermined size is electrolytically degreased and washed with water. Then, a chemical etching roughening solution is sprayed to roughen the surface by chemical etching with a depth of dissolution of about 0.5 to 3 μm, for example, a depth X from the untreated copper foil surface of about 2 μm. Next, it is washed with water and dried. The surface-roughened electrolytic copper foil is laminated and pressed with a substrate (prepreg). The bonded wiring board is physically and firmly joined by the anchor effect due to the unevenness of the copper foil surface, and even if the printed wiring board is subjected to thermal stress during subsequent processes, for example, reflow soldering, No peeling at the interface with the substrate occurs.

As the substrate, any of epoxy resin, polyester, polyimide, polyamideimide and a glass cloth composite material thereof, a laminated plate of phenol resin-paper and epoxy resin-paper, or the like may be used. Further, a laminate, sheet or film of the above-mentioned various resins in which aluminum or an iron plate is bonded can be used as a heat sink.
Also, inorganic materials such as ceramic plates and glass plates using resin or rubber as the adhesive layer can be used.

  Hereinafter, the present invention will be described more specifically with reference to examples.

Electrolytic copper foil of 12 μm was prepared in each plating bath and conditions using a Ti plate buffed as Rz = 1.5 μm as a cathode.
Then, etching roughening was performed, and the FR-4 base material was hot-pressed and joined to measure the peel strength.

Invention Example 1
Copper sulfate pentahydrate 280 g / l, sulfuric acid 100 g / l, sulfuric acid acidic copper sulfate electrolyte containing 35 ppm of chlorine ions, low molecular weight gelatin with an average molecular weight of 3000 ppm, hydroxyethyl cellulose 3 ppm, 3-mercapto-1-propane 1 ppm of sodium sulfonate was added, and an electrolytic copper foil was formed under conditions of an electrolyte temperature of 55 ° C., a flow rate of 0.3 m / min, and a current density of 50 A / dm ² , and kept in an atmosphere of 50 ° C. for 3 days. As a result of confirming the crystal state of the copper foil, the crystal state of the copper foil is a granular crystal, and the average crystal grain in the range from the M plane to 2 μm (depth X) is 0.5 μm. The crystal grains of 1 μm or more in the etching region) were 12%.
This foil was subjected to chemical etching with a MZ CZ8101 to a depth of 2 μm at maximum, and a sample for measuring peel strength and the like was obtained.

Invention Example 2
Copper sulfate pentahydrate 280 g / l, sulfuric acid 130 g / l, sulfuric acid acidic copper sulfate electrolyte containing 50 ppm of chlorine ions, hydroxyethyl cellulose 10 ppm, sodium 3-mercapto-1-propanesulfonate 1 ppm An electrolytic copper foil was made under conditions of a liquid temperature of 60 ° C., a flow rate of 0.8 m / min, and a current density of 45 A / dm ² , and kept in an atmosphere of 70 ° C. for 3 days to obtain an untreated copper foil. As a result of confirming the crystal state of the body-treated copper foil, the copper foil has a granular crystal, and the average crystal grain in the range from the M plane to 2 μm is 0.8 μm, and the crystal grain in this range is 1 μm or more. Was 17%.
This foil was subjected to chemical etching treatment by spraying using MZ CZ8101 to a depth of 2 μm at maximum, to obtain a measurement sample for measuring peel strength and the like.

Invention Example 3
After confirming the crystal state after storing the copper foil of Example 1 at 80 ° C. for 1 day, the copper foil had granular crystals, and the average crystal grains in the range from the M plane to 2 μm were 1.2 μm. The crystal grain size of 1 μm or more in this range was 27%.
This foil was subjected to chemical etching treatment by spraying using MZ CZ8101 to a depth of 2 μm at maximum, to obtain a measurement sample for measuring peel strength and the like.

Invention Example 4
The copper foil of Example 1 was heated at 200 ° C. for 5 hours to confirm the crystal state. As a result, the copper foil had granular crystals, and the average number of crystal grains in the range from the M plane to 2 μm was 1. It was 4 μm, and the crystal grain size of 1 μm or more in this range was 45%. This foil was subjected to chemical etching treatment with a spray method using MZ CZ8101 at a maximum depth of 2 μm to obtain a sample for measuring peel strength and the like.

Comparative Example 1
Etching roughening was not performed in Example 1 of the present invention, and a sample for measuring peel strength and the like was used.

Comparative Example 2
Copper sulfate sulfate pentahydrate 280 g / l, sulfuric acid 80 g / l, sulfuric acid acidic copper sulfate electrolyte containing 35 ppm of chlorine ion, low molecular weight gelatin with average molecular weight of 3000 ppm, hydroxyethyl cellulose 3 ppm, 3-mercapto-1-propane 1 ppm of sodium sulfonate was added, and an electrolytic copper foil was produced under the conditions of an electrolyte temperature of 30 ° C., a flow rate of 0.2 m / min, and a current density of 30 A / dm ² . The average particle size from the M surface to the depth of 2 μm of this copper foil was 0.2 μm and was a granular crystal. This copper foil was used as a sample for measuring peel strength and the like.

Comparative Example 3
As an electrolytic solution, an electrolytic solution containing 90 g / l of copper, 100 g / l of sulfuric acid, 20 ppm of chlorine ions, 300 ppm of hydrolyzed glue, and 2 ppm of glue before hydrolysis.
A copper foil having a columnar crystal was produced under the conditions that the added liquid temperature was 55 ° C. and the current density was 55 A / dm ² . This copper foil was used as a sample for measuring peel strength and the like.

  The results are shown in Table 1 below.

  As apparent from Table 1, the peel strength was sufficient in the examples of the present invention, but weak in the comparative examples, and peeling occurred due to a slight bending work.

As described above, the present invention can provide and provide an electrolytic copper foil having high peel strength and stable adhesion to the substrate.

Claims (4)

  An electrolytic copper foil obtained by electrodepositing a copper foil on the electrolytic drum and making it into a cathode is heat-treated in an atmosphere of 50 ° C. or higher, and at least one surface of the electrolytic copper foil is a granular crystal An untreated copper foil having an average particle size of 0.3 μm or more in a region from the surface to at least the depth X, and the granular crystal surface of the untreated copper foil is subjected to chemical etching to the depth from the granular crystal surface. The manufacturing method of the electrolytic copper foil characterized by performing an etching process to thickness X.   2. The crystal grain having a grain size of 1 μm or more is present in an area ratio of 10% or more in a region from the grain surface of the untreated copper foil to a depth X to be etched. Manufacturing method of electrolytic copper foil. 3. The electrolytic copper foil is subjected to a heat treatment at 50 ° C. or more and an LMP value represented by Formula 1 is 7000 or more, and chemical etching treatment is performed on the heat-treated granular crystal surface. The manufacturing method of the electrolytic copper foil as described in any one of.
Formula 1: LMP = (T + 273) × (20 + Logt)
Here, T is temperature (° C.), and t is time (Hr). An electrolytic copper foil obtained by electrodepositing a copper foil on the electrolytic drum and making it into a cathode is heat-treated in an atmosphere of 50 ° C. or higher, and at least one surface of the electrolytic copper foil is a granular crystal An untreated copper foil having an average particle size of 0.3 μm or more in a region from the surface to at least the depth X, and the granular crystal surface of the untreated copper foil is subjected to chemical etching to the depth from the granular crystal surface. A printed wiring board comprising: a roughened copper foil etched to a thickness X, and a roughened surface of the roughened copper foil bonded to a printed wiring board substrate.