JP2005219379A - Composite material for substrates and circuit board using it - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a composite material for a substrate which is low in hygroscopicity and high in peel strength in a laminate between a liquid crystal polymer film having enough heat resistance to soldering and copper foil and can be converted into a fine pattern and a circuit board using the composite material. <P>SOLUTION: In the composite material for the substrate, the surface-treated copper foil having a roughened surface 2.5-4.0 μm in surface roughness Rz and 25 or below in brightness by bonding roughening particles to at least one side of the copper foil and the insulating substrate containing at least 50% of a thermoplastic liquid crystal polymer are laminated. Projections by the roughening particles are preferably distributed approximately uniformly so that 6-35 projections 1-5 μm high are distributed in a range of an observation cross section of 25 μm. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a flexible substrate / high-density mounting formed of a film mainly composed of a thermoplastic liquid crystal polymer (hereinafter sometimes referred to as a liquid crystal polymer film) and a surface-treated copper foil having improved adhesion to the liquid crystal polymer film. The present invention relates to a composite material for a substrate for manufacturing a multi-layer substrate, a high-frequency substrate, and the like, and further relates to a circuit board formed using the composite material for a substrate.

As electronic devices become smaller and lighter, various recent electronic components are highly integrated.
The composite material for boards that manufactures flexible boards, multilayer boards for high-density mounting, high-frequency boards, etc. (hereinafter also collectively referred to as printed wiring boards) used in these is a conductor (copper foil) and it The insulating substrate is supported, and the insulating substrate has a predetermined strength in order to ensure insulation between conductors and to support components.
In addition, when the signal speed of an insulating substrate increases, the material of the insulating substrate plays an important role in the characteristic impedance, signal propagation speed, etc., so that improvement in the characteristics such as dielectric constant and dielectric loss of the material is required. The Various materials have been proposed to satisfy these requirements. For example, for high-speed signal propagation, an insulating substrate having a low dielectric constant and low dielectric loss, a single-sided plate is often made of a phenol resin material, and a plated through hole is made of an epoxy resin material. Insulating substrates that require heat resistance use heat-resistant epoxy resin, polyimide, or the like. In addition, materials with good dimensional stability, materials with less warping and twisting, and materials with less heat shrinkage have been developed.

  When a flexible composite material for a substrate requires heat resistance and soldering is performed, a polyimide film is used for the insulating substrate. On the other hand, polyester film is used in places where solder is not used for printing with carbon ink or the like. In recent years, flexible substrates and the like have become complicated, and in many cases, polyimide films have been adopted. However, polyimide has a drawback in that dielectric properties greatly change due to water absorption, and high-frequency properties greatly decrease in a water absorption environment. On the other hand, since it has high heat resistance, there is no heat meltability, so to compound with copper foil as a conductor, after casting polyamic acid as a precursor on copper foil, imidization or on polyimide film It is necessary to take a method such as laminating with a copper foil after providing an adhesive layer, and there is a problem that the process becomes complicated.

Therefore, liquid crystal polymer films have attracted attention as thermoplastic materials having extremely low hygroscopicity as compared with polyimide, and hence little change in dielectric properties, and heat resistance that can withstand soldering. However, this liquid crystal polymer film has low adhesion to copper foil, and the peel strength with copper foil tends to be weak compared to polyimide.
The copper foil bonded to these insulating substrates and used as a conductor is mainly an electrolytic copper foil. The electrolytic copper foil is usually a copper foil produced by an electrolytic foil making apparatus as shown in FIG. 1, or a roughening treatment or rust prevention treatment for improving adhesion by a surface treatment apparatus as shown in FIG. 2. It is manufactured by applying. The electrolytic foil making apparatus is an apparatus comprising a rotating drum-like cathode 2 (the surface is made of SUS or titanium) and an anode 1 (lead or noble metal oxide-coated titanium electrode) arranged concentrically with the cathode. An electric current is passed between both electrodes while the electrolytic solution 3 is circulated to deposit copper to a predetermined thickness on the cathode surface, and then the copper is peeled off from the cathode surface in a foil shape. The copper foil at this stage is the untreated copper foil 4, the surface of the untreated copper foil in contact with the electrolyte is the matte surface, and the surface in contact with the rotating drum-shaped cathode 2 is the glossy surface (shiny surface). It is.

  In order to increase the adhesive strength (peel strength) required for producing a copper-clad laminate by laminating an untreated copper foil 4 made of a foil, a surface treatment apparatus as shown in FIG. 2 is used. The untreated copper foil 4 is continuously subjected to electrochemical or chemical surface treatment. FIG. 2 shows an apparatus for continuously performing electrochemical surface treatment. An untreated copper foil 4 is continuously passed through an electrolytic layer filled with an electrolytic solution 5 and an electrolytic layer filled with an electrolytic solution 6. Then, surface treatment is performed using the electrode 7 as an anode and the copper foil itself as a cathode, and granular copper is deposited on the surface of the untreated copper foil 4 in order to improve adhesion when adhered to an insulating (resin) substrate. . This step is a roughening treatment step, and the roughening treatment is usually applied to the mat surface or shiny surface of the untreated copper foil 4. The copper foil after the surface treatment is the surface-treated copper foil 8, which is laminated with an insulating substrate and used as a composite material for a substrate.

  However, the liquid crystal polymer film is known as an insulating substrate that is particularly difficult to have peel strength. In general, peel strength is specified in 5.1 (definition of ten-point average roughness) of copper foil surface roughness Rz (surface roughness: Rz) (JISB 0601-1994 “Definition and Display of Surface Roughness”). When considering the surface roughness of the copper foil, the surface roughness Rz of the untreated copper foil or the irregularities formed by the granular copper of the surface-treated copper foil. The surface roughness Rz of a smooth unprocessed copper foil, particularly when peel strength is obtained on an insulating substrate that is difficult to produce peel strength, increases the current that flows during the roughening treatment. In order to increase the surface roughness Rz, the amount of adhered copper has been increased, and this method is suitable for the purpose of increasing the peel strength. The surface roughness Rz is large or rough due to the skin effect. Increasing the amount of particles is not preferable, and depending on the type of liquid crystal polymer film, there is a type of film that does not correlate with peel strength, even if the surface roughness Rz value is increased. It has been found that such films are closely related to the shape of the protrusions formed in the roughened particles.

Further, the circuit pattern on the printed wiring board is also required to have a high density, and a so-called fine pattern printed wiring board on which a circuit pattern composed of wiring with a fine line width and wiring pitch is formed is required. . Recently, for example, a printed wiring board having high-density ultrafine wiring with a wiring pitch of about 50 μm to 100 μm and a line width of about 30 μm is required. Increasing the surface roughness Rz of the roughened particles for increasing the peel strength and increasing the amount of adhesion are also inappropriate for producing these fine patterns.
Therefore, it is possible to increase the peel strength by roughening the surface of the untreated copper foil and reducing the amount of roughened particles, but it is not suitable for creating high-frequency characteristics / fine patterns.

As a copper foil having improved adhesion to a liquid crystal polymer film, a copper alloy foil containing a specific element and provided with a surface oxide layer and a rust preventive layer having a specific thickness has been proposed (see Patent Document 1). However, when the liquid crystal polymer is made into a film, the rod-shaped molecules are oriented in the plane direction, so the strength in the thickness direction is extremely reduced. As a result, a sufficient peel strength is not obtained.
Moreover, in order to improve the adhesiveness of the liquid crystal polymer, methods for surface treatment such as plasma (see Patent Document 2), UV treatment (see Patent Document 3) have been proposed. The copper foil with low surface roughness does not have sufficient adhesion.
Therefore, it is required to develop copper foils that have good high-frequency characteristics, to be able to produce fine patterns, to increase peel strength, and to emerge as a heat-resistant and flexible substrate composite material that uses these copper foils. Has been.

JP 2003-64431 A JP 2001-49002 A JP 2000-233448 A

  The present invention has been made to solve such problems of the prior art, and since it has extremely low hygroscopicity, it has little change in dielectric properties, has heat resistance that can withstand soldering, and is heated by copper. Using a liquid crystal polymer film that can be laminated with a foil, and a surface-treated copper foil that has a high peel strength and can be made into a fine pattern with respect to the liquid crystal polymer film, The object is to provide a circuit board using the same.

In the present invention, at least one surface of a copper foil is attached with roughened particles, the surface roughness is Rz: 2.5 to 4.0 μm, and the brightness value is 25 or less, and 50% The above is a composite material for a substrate formed from an insulating substrate made of a thermoplastic liquid crystal polymer.
Further, in the surface-treated copper foil of the present invention, protrusions are formed from the roughened particles, and the protrusions are 6 to 35 protrusions having a height of 1 μm to 5 μm and an observation cross section of 25 μm. It is preferable that the copper foil is distributed evenly in terms of the number, and the maximum width of each protrusion in the protrusions of the surface-treated copper foil is 0.01 μm or more and the number of protrusions existing in a range of 25 μm ( The length is preferably not more than twice the length obtained by dividing 25 μm by n).
Further, according to the present invention, in the protrusions of the surface-treated copper foil, the maximum width of each protrusion is 0.01 μm or more and twice the length obtained by dividing 25 μm by the number (n) of protrusions existing in the 25 μm range. The following is preferable.
Furthermore, in the present invention, it is preferable to use an electrolytic copper foil as the copper foil before the roughening treatment of the surface-treated copper foil.
Furthermore, in the present invention, a copper foil having a surface roughness Rz of 2 μm or less is preferred for at least the surface of the untreated copper foil used for the surface-treated copper foil.
Furthermore, in the present invention, it is preferable that the roughened surface of the surface-treated copper foil has a matte surface having a surface roughness Rz of 2 μm or less.
Furthermore, in the present invention, the insulating substrate is preferably a film made of a resin containing 50% or more of a thermoplastic liquid crystal polymer.
Furthermore, the present invention is a circuit board characterized by being made of the substrate composite material.

  The present invention has a remarkably low hygroscopic property, so that there is little change in dielectric properties and heat resistance that can withstand soldering, and the liquid crystal polymer film has a high peel strength and can be made into a fine pattern. By using the surface-treated copper foil, it is possible to provide a composite material for a substrate that is particularly fine and excellent in high-frequency characteristics and a circuit board using the same.

  In the present invention, the copper foil before surface treatment (untreated copper foil) is a copper foil produced by electrolysis or rolling. The thickness of the copper foil is 1 μm to 200 μm, and at least one surface is preferably a copper or copper alloy foil having a surface roughness of Rz: 0.01 μm to 2 μm. Regarding the thickness of the foil, it is very difficult to roughen the surface of the copper foil having a thickness of 1 μm or less, and the copper foil used for a high-frequency printed wiring board is 200 μm or more. This is because the foil is not realistic.

  Regarding the surface roughness of the untreated copper foil, a foil with Rz: 0.01 μm or less is practically difficult to manufacture, and even if it can be manufactured, it is costly and expensive, so it is not practically suitable. In addition, although an untreated copper foil of Rz: 2 μm or more may be used, the surface roughness of the untreated copper foil is more preferably Rz: 2 μm or less in consideration of high frequency characteristics and fine patterning. .

In the present invention, surface roughening treatment is performed on the above-described untreated copper foil.
In the surface roughening treatment of the surface of the untreated copper foil, roughened particles are attached to the surface of the untreated copper foil, and the surface roughness is a roughened surface of Rz: 2.5 to 4.0 μm. If the Rz is less than 2.5 μm, the peel strength is low, so it is not satisfactory as a surface-treated copper foil that fulfills its purpose. If the Rz is greater than 4.0 μm, the high-frequency characteristics are deteriorated and unsuitable for fine patterning. It is because it becomes.

  In the present invention, the roughened copper foil subjected to the surface roughening treatment needs to have a brightness value of 25 or less. The lightness in the present invention is usually the lightness used as an index for viewing the roughness of the surface, and the measuring method is a method of measuring the amount of reflected light by applying light to the surface of the measurement sample and expressing it as a lightness value. is there. When the brightness of the treated surface of the surface-treated copper foil is measured by this method, when the surface roughness Rz is large or the depth of the groove between the roughened particles is deep, the lightness value is reduced because the amount of reflected light is reduced. If it is low and smooth, the amount of reflected light tends to increase and the brightness tends to increase.

  In order to improve the peel strength with the insulating substrate (liquid crystal polymer film), the brightness is preferably 25 or less. On the other hand, when the brightness is 26 or more, even if the roughened surface has a large Rz, the unevenness becomes gentle, so that the bite between the surface-treated copper foil and the insulating substrate (liquid crystal polymer film) is poor and the peel strength is not improved.

The brightness is measured on the copper foil to be measured.
Ni: 0.01 to 0.5 mg / dm ²
Zn: 0.01 to 0.5 mg / dm ²
Cr: 0.01 to 0.3 mg / dm ²
Then, the brightness was measured using a lightness meter (manufactured by Suga Test Instruments Co., Ltd., model name: SM color computer, model number: SM-4).
The surface-treated copper foil of the present invention having both surface roughness (Rz) and brightness value as described above is laminated and combined with a liquid crystal polymer film to compensate for the drawbacks of the liquid crystal polymer film having a difficulty in adhesion, As will be apparent from Examples and Comparative Examples described later, it is possible to provide a composite material for substrates having excellent peel strength and fine pattern characteristics.

  In the present invention, as described above, the surface of the untreated copper foil is roughened, but in order to obtain further excellent peel strength and fine pattern characteristics, the protrusions formed from the roughened particles described below Are preferably present (distributed) substantially evenly. The height of the protrusion is preferably 1.0 μm to 5.0 μm. If the height of the protrusions formed on the surface of the untreated copper foil is 1.0 μm or less, the height is low, so the effect of increasing the peel strength cannot be obtained. If the height is 5.0 μm or more, the distribution of the protrusions is uniform. This is because the surface roughness Rz of the surface-treated foil varies widely from range to range, so that a stable peel strength cannot be maintained, high-frequency characteristics are deteriorated, and it is not suitable for fine patterning. . Here, the height refers to the distance between the surface of the untreated copper foil and the top of the protrusion.

  Also, if the number of protrusions is small, peel strength cannot be obtained, and if the number is large, the adhesion between the copper foil surface and the protrusions is weak and the effect decreases even if the number is large. In the observation cross section of 25 μm, 6 to 35 are preferable, and 10 to 20 are particularly preferable.

  Here, the concept of the protrusion in the present invention will be described. The distance between the bottom of the groove formed between adjacent protrusions and the apex of the protrusion (hereinafter sometimes referred to as groove depth) is 0. When the depth is less than 3 μm, the adjacent protrusions are recognized as one protrusion, and when the groove depth is 0.3 μm or more, the adjacent protrusions are recognized as two protrusions. . This groove depth refers to the distance between the surface of the untreated copper foil and the top of the protrusion, while the height of the protrusion described above is the distance between the bottom of the groove and the protrusion after the surface roughening treatment. It differs in the point of the distance from the vertex.

  As a method of counting the number of protrusions, a method of counting the number of protrusions as defined above with a length of 25 μm by observing a cross-sectional SEM after embedding a surface-treated copper foil in a resin, polishing, and performing observation Is mentioned. The present invention lists the numbers measured using this method in the table of examples. In addition, schematic views of cross-sectional observation are shown in FIGS.

  Further, the number of protrusions having a height of 1.0 μm to 5.0 μm is 6 to 35 within 25 μm, and a groove having a depth of 0.3 μm or more is present between the protrusions. Distributing evenly prevents the protrusions from being partially concentrated within 25 μm, and can stabilize the peel strength in the width direction and the longitudinal direction of the copper foil.

As described in the present invention, “almost uniformly distributed”
“The height between the top of the protrusion and the copper foil surface is 1.0 μm to 5.0 μm, and the number of protrusions is n (pieces), and the observation width when the protrusion is observed in cross section is 25 (μm ), At least a part of the protrusion is present in the region having a width of 25 / n (μm) ”.

  Further, in order to stabilize the peel strength, it is desirable that the width of the protrusions to be formed is uniform, and the protrusions whose maximum width is within the range of 0.01 μm or more and 25 μm. The width is preferably not more than twice the length divided by 25 μm. In addition, the maximum width here means the maximum value of the distance in the direction perpendicular to the height direction of the projection in the SEM observation of the cross section.

Further, regarding the groove depth between the protrusions, the average groove depth between the protrusions is more preferably 0.5 μm or more.
For the average groove depth between protrusions, for n protrusions with a groove depth of 0.3 μm or more, measure the groove depth on both sides of each protrusion, and the value at that time is A1 (μm) B1 (μm)... An (μm) When Bn (μm), the value obtained by the following equation.
((A1 + B1) + ... + (An + Bn)) / 2 / n

FIG. 3 is a view showing an observation cross section of the surface-treated copper foil suitable for the embodiment of the present invention. The number of protrusions is 6 or more within 25 μm, the height is in the range of 1 to 5 μm, the groove depth is 0.3 μm or more, and the maximum width of the protrusion is 0.01 μm or more, The width is not more than twice the length obtained by dividing 25 μm by the number of protrusions existing in the range of 25 μm.
In FIG. 4, there are some protrusions having a width that is twice or more the length obtained by dividing 25 μm by the number of protrusions having a maximum width of 0.01 μm or more and 25 μm. FIG. 5 shows a cross section in which the protrusions are not evenly distributed.
As described above, the surface-treated copper foil having a cross-sectional shape shown in FIG. 3 has good adhesion to the liquid crystal polymer film, and a fine pattern circuit configuration is possible. The surface-treated copper foil having a cross-sectional shape shown in FIG. 4 has a wide protrusion in part, and there is a part that does not have good adhesion to the liquid crystal polymer film, so that there is a problem in the fine pattern circuit. However, it does not interfere with other general purposes. As shown in FIG. 5, when the projections are not evenly distributed, the adhesion with the liquid crystal polymer film is hindered, and there is a possibility that the circuit configuration of the fine pattern cannot be made.

The roughening particles forming the protrusions of the surface-treated foil constituting the substrate composite material of the present invention are selected from the group consisting of Cu or alloy particles of Cu and Mo or Cu and Ni, Co, Fe, Cr, V and W. It is a copper alloy containing at least one element.
The desired projections can be obtained with Cu particles or alloy particles of Cu and Mo, but at least one element selected from the group of Ni, Co, Fe, Cr, V and W can be used as the Cu particles or alloy particles of Cu and Mo. Projections formed of two or more types of alloy roughening particles containing, are effective because they can form more uniform projections. The roughened particles forming these protrusions are thought to increase the peel strength because chemical bonding is performed with the liquid crystal polymer film (insulating substrate). Depending on the type of resin constituting the insulating substrate, Cu-Mo alloy, Cu-Ni alloy, Cu-Co alloy, Cu-Fe alloy, Cu-Cr alloy, Cu- A Mo-Ni alloy, a Cu-Mo-Cr alloy, a Cu-Mo-Co alloy, a Cu-Mo-Fe alloy, etc. can be mentioned.

  At least one element selected from the group of Mo, Ni, Co, Fe, Cr, V and W contained in the alloy particles forming the protrusions occupies 0.01 ppm to 20% with respect to the amount of Cu present. It is preferable. This is because an alloy composition having an abundance exceeding 20% is difficult to dissolve when the circuit pattern is etched. Furthermore, in order to obtain uniform protrusions, it is desirable to optimize the composition, current density, solution temperature, and treatment time of various treatment solutions. One example is shown in the Examples.

In addition, at least one metal selected from the group consisting of Ni, Ni alloy, Zn, Zn alloy, and Ag is provided on the surface provided with the protrusions for the purpose of improving powder fall resistance, hydrochloric acid resistance, heat resistance, and conductivity. A plating layer may be provided.
Furthermore, at least one metal plating layer of Ni, Ni alloy, Zn, Zn alloy, or Ag is attached to the surface on which the protrusion is not provided for the purpose of improving hydrochloric acid resistance, heat resistance, and conductivity. And good. In order to achieve these purposes, the amount of deposited metal is preferably 0.05 mg / dm ² or more and 10 mg / dm ² or less.
In particular, Ni metal or Ni alloy is effective in improving the peel strength when combined with a liquid crystal polymer film or the like.
A Cr and / or chromate film is formed on the plating layer having the above-described structure, and a rust prevention treatment is performed, or a silane coupling treatment or a rust prevention treatment + silane coupling is performed as necessary.

  As the insulating substrate, a film or an injection-molded plate made of a composition containing 50% or more of a liquid crystal polymer is used. This composition includes thermoplastic resins such as inorganic filler, polyethersulfone, polyamideimide, polyetherimide, polyetheretherketone, and thermoplastic polyimide for the purpose of controlling the linear expansion coefficient, improving adhesiveness, and improving physical properties. However, if the content of the liquid crystal polymer is less than 50%, the properties of the liquid crystal polymer are lost in terms of low water absorption, heat resistance, dielectric properties and the like, which is not preferable.

  The liquid crystal polymer used here refers to a thermoplastic liquid crystal polymer that exhibits liquid crystallinity in a heated and melted state, and exhibits liquid crystallinity in a solution, but a lyotropic liquid crystal polymer such as an aromatic polyamide that does not cause heat melting. Not used. A typical example of such a liquid crystal polymer is a wholly aromatic polyester obtained by homopolymerizing or copolymerizing aromatic hydroxycarboxylic acid, aromatic dicarboxylic acid, aromatic diol or the like as a monomer.

  As a method of laminating the liquid crystal polymer film as the insulating substrate and the surface-treated copper foil, a hot press method, a continuous roll laminating method, a continuous belt press method, or the like can be used, and thermocompression bonding is performed without using an adhesive or the like. be able to.

Hereinafter, the present invention will be described in more detail based on examples, but the present invention is not limited thereto.
In the present Example, what was described below was used as copper foil, the plating solution for roughening processes, and the film for insulating substrates.

(I) Copper foil:
(i) Raw foil 1
An untreated electrolytic copper foil and an untreated rolled copper foil having a thickness of 12 μm, a mat surface roughness of Rz = 1.26 μm, and a glossy surface roughness of Rz = 1.82 μm were prepared.
(ii) Raw foil 2
An untreated electrolytic copper foil having a thickness of 12 μm, a mat surface roughness: Rz = 1.52 μm, and a glossy surface roughness: Rz = 1.46 μm was prepared.
(iii) Raw foil 3
An untreated electrolytic copper foil having a thickness of 12 μm, a mat surface roughness: Rz = 1.86 μm, and a gloss surface roughness: Rz = 1.2 μm was prepared.

(B) Surface roughening plating solution and plating conditions:
(i) Electroplating A
・Plating bath 1
Copper sulfate (as Cu metal) 5-10g / dm ³
Sulfuric acid 30-120 g / dm ³
Ammonium molybdate (as Mo metal) 0.1-5.0 g / dm ³
Current density 10-60A / dm ²
Energizing time 1 second-2 minutes Bath temperature 20-60 ° C
・Plating bath 2
Copper sulfate (as Cu metal) 20-70 g / dm ^{3
30 to} 120 g / dm ^{3 of} sulfuric acid,
Current density 5-60A / dm ²
Energizing time 1 second to 2 minutes Bath temperature 20 ° C to 65 ° C

(ii) Electroplating B
・Plating bath 1
Copper sulfate (as Cu metal) 1-50g / dm ³
Nickel sulfate (as Ni metal) 2-25g / dm ³
Ammonium metapanadate (as V metal) 0.1-15 g / dm ³
pH 1.0-4.5
Current density 1-60A / dm ²
Energizing time 1 second to 2 minutes Bath temperature 20 ° C to 60 ° C
・Plating bath 2
Copper sulfate (as Cu metal) 10-70 g / dm ³
Sulfuric acid 30-120 g / dm ³
Current density 5~60A / dm ^2,
Energizing time 1 second to 2 minutes Bath temperature 20 ° C to 65 ° C

(iii) Electroplating C
・Plating bath 1
Copper sulfate (as Cu metal) 1-50 / dm ³ ,
Cobalt sulfate (as Co metal) 1-50 g / dm ³
Ammonium molybdate (as Mo metal) 0.1-10 g / dm ³
pH 0.5-4.0
Current density 1-60A / dm ²
Energizing time 1 second to 2 minutes Bath temperature 20 ° C to 60 ° C
・Plating bath 2
Copper sulfate (as Cu metal) 10-70 g / dm ³
Sulfuric acid 30-120 g / dm ³
Current density 5-60A / dm ²
Energizing time 1 second to 2 minutes Bath temperature 20 ° C to 65 ° C

(iv) Electroplating A'B '(comparative example)
・Plating bath 3
Copper sulfate (as Cu metal) 20-70 g / dm ³
Sulfuric acid 30-120 g / dm ³
Current density 3A / dm ²
Energizing time 2 minutes or more (change time in surface roughness)
Bath temperature 15 ℃

(C) Film for insulating substrate:
(i) Liquid crystal polymer film (insulating substrate) 1 (hereinafter referred to as “film 1”)
Japan Gore-Tex Co., Ltd. type I liquid crystal polymer film, BIAC BA050F-NT
Was used.
(ii) Liquid crystal polymer film 2 (insulating substrate) (hereinafter referred to as “film 2”)
Japan Gore-Tex Co., Ltd. type II liquid crystal polymer film, BIAC BC050F-NT
Was used.

In the surface treatment apparatus shown in FIG. 2 using the above-mentioned original foil 1 to original foil 3 as the copper foil, any one of the plating solution composition, bath temperature, and current condition ranges shown in the above electroplating solutions A to C The plating was performed at least once in the order of plating bath 1 → plating bath 2. Furthermore, Ni plating (0.3 mg / dm ² ) zinc plating (0.1 mg / dm ² ) was applied to these roughened surfaces, and chromate treatment was performed thereon. In the case of the electroplating solutions A ′ and B ′, the solution composition and conditions of the plating bath 3 were used instead of the plating bath 2.
Table 1 shows the measurement results such as the surface roughness of the surface-roughened copper foil thus obtained, together with the surface treatment selection conditions.

Next, the surface-treated copper foil thus obtained was laminated with a liquid crystal polymer film (insulating substrate) as follows.
That is, the surface-treated copper foil obtained as described above and either the film 1 or 2 are laminated, and the film 1 is used by using a multistage vacuum press (Hitakawa Co., Ltd. hot and cold press VH3-1377). In this case, the film was held at 335 ° C. and 4 MPa, and in the case of the film 2 at 310 ° C. and 4 MPa, held for 5 minutes, then cooled and laminated to obtain a composite material for a substrate. The temperature was raised from room temperature at a rate of 7 ° C./min.

  The peel strength of the substrate composite material (copper-clad laminate) with the liquid crystal polymer film using the surface-treated foil thus obtained was measured. The peel strength was measured in accordance with JIS C6471 by peeling in the 180 degree direction.

Further, the fine pattern characteristics of the prepared substrate composite were evaluated by the following methods.
That is, the prepared copper foil was attached to FR4 resin, and the copper foil resisted with line width: L and space width: S on the copper foil was etched with an iron chloride bath as shown in the schematic sectional view of FIG. The etching time when the top width of the line width L is the same as the resist width is determined, and each of the substrates resisted with each line width L and each space width S (10 lines formed on one substrate) is registered. n = 10 and etching is performed in the iron chloride bath for the above-determined time, and in each substrate, there is no bridge between the lines, or there is no root residue, or the top width of the line is equal to the resist. Observing that they were the same, the minimum L and S values were obtained among those substrates in which n = 10 were not observed.
Table 1 shows the results of peel strength and fine pattern characteristics evaluation performed under the conditions of the above Examples and Comparative Examples.

  As the results shown in Table 1, it can be seen that the peel strength is clearly improved by the number of protrusions formed from the roughened particles and the numerical value of the brightness even if the surface roughness is equal. In Comparative Example 7, the peel strength is improved by the amount of roughness, but there is a defect that the fine pattern cannot be cut.

  As described above, the present invention has a good peel strength while using a liquid crystal polymer film on an insulating substrate by forming protrusions having the specific shape and distribution described above formed of roughened particles on the surface of the copper foil. Since a fine wiring pattern can be created, it can be used for a substrate composite material excellent in high-frequency characteristics, a circuit board using the same, and used in various fields of electronic circuit parts industry. Is possible.

It is sectional drawing which shows the structure of an electrolytic foil manufacturing apparatus. It is explanatory drawing which shows the structure of a surface treatment apparatus. It is a section observation schematic diagram of one embodiment of the surface treatment copper foil of the present invention. It is the cross-sectional observation schematic of other embodiment of the surface treatment copper foil of this invention. In surface treatment foil, it is a section observation schematic diagram showing the state where a projection is not distributed uniformly. It is explanatory drawing which shows the cross section after an etching.

Explanation of symbols

1 Electrolytic Foil Device Anode 2 Electrolytic Foil Device Cathode 3 Electrolytic Foil Device Electrolyte 4 Untreated Copper Foil
5 Electrolytic solution 6 of surface treatment device Electrolyte solution 7 of surface treatment device Anode 8 of surface treatment device Electrolytic copper foil (surface treatment copper foil)

Claims (8)

Surface-treated copper foil having roughened particles attached to at least one surface of the copper foil and having a surface roughness Rz of 2.5 to 4.0 μm and a lightness value of 25 or less, and a surface-treated copper foil of 50 A composite material for a substrate, characterized in that it is laminated with an insulating substrate made of a thermoplastic liquid crystal polymer. The surface-treated copper foil has protrusions formed from the roughened particles, and the protrusions have a number of protrusions having a height of 1 μm to 5 μm and a number of 6 to 35 in the observation cross section of 25 μm. The composite material for a substrate according to claim 1, wherein the composite material is distributed substantially evenly. In the protrusions of the surface-treated copper foil, the maximum width of each protrusion is 0.01 μm or more and not more than twice the length of 25 μm divided by the number of protrusions existing in the 25 μm range. The composite material for substrates according to claim 1 or 2. The board | substrate composite material in any one of Claim 1 thru | or 3 whose copper foil before the roughening process of the said surface treatment copper foil is an electrolytic copper foil. The composite material for a substrate according to any one of claims 1 to 4, wherein a roughness Rz of at least a surface of the untreated copper foil used for the surface-treated copper foil is 2.0 µm or less. . 6. The substrate composite according to claim 5, wherein the surface of the untreated copper foil subjected to the roughening treatment is a matte surface having a surface roughness of 2.0 [mu] m or less. 7. The composite material for a substrate according to claim 1, wherein the insulating substrate is composed of a film containing 50% or more of a thermoplastic liquid crystal polymer. A circuit board produced using the substrate composite material according to claim 1.

Images