JP2006269706A - Laminate substrate and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a laminate substrate using conductive paste having a low melting point metal, which does not cause a void on an interface between copper foil and the conductive paste having the low melting point metal and is highly reliable in connection. <P>SOLUTION: The laminate substrate is composed of a laminate of roughened copper foil with a surface of copper or copper-alloy-based foil with surface roughness on at least one of faces having a roughness of 0.1-5 μm by etching to form a protrusions with a height of 0.3 μm or higher distributed approximately uniformly and a surface roughness Rz of 0.5-10 μm; and a substrate filled with the conductive paste having the low melting point metal in a through-hole formed at a resin substrate. A method of manufacturing the laminate substrate includes a step of laminating the roughened copper foil on the substrate filled with the conductive paste having the low melting point metal in the through-hole formed at the resin substrate. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a laminated circuit board (multilayer printed wiring board) that conducts wiring provided on the front and back surfaces with a conductive composition (conductive paste).

In conventional multilayer circuit boards, through-hole plating is performed by laminating multilayer wiring board base materials in multiple layers, opening through holes in the insulating layer, and providing interlayer conduction with a plating layer on the inner surface of the through holes. There is a law. The multilayer circuit board by the through-hole plating method has the advantage that the circuit of each layer can be connected with a low and stable connection resistance, but the process is complicated and the man-hours are high, so the cost is high and the use of the multilayer circuit board is limited. Is a factor.
In addition, the laminated circuit board by the through-hole plating method has a drawback in that a component cannot be mounted immediately above the through-hole and the degree of freedom of wiring is low.
In order to eliminate this drawback, a method of forming a through hole in an inclined manner with respect to the surface of the substrate in a laminated circuit board by a through hole plating method is adopted so as to avoid the placement position of the mounted components.

In recent years, as an interlayer connection method replacing the through-hole plating method, a laminated circuit board using IVH (Interstitial Via Hole) in which a through-hole is filled with a conductive paste has been put into practical use. The laminated circuit board using this conductive paste has a simplified manufacturing process and can be reduced in cost as compared with a through-hole plating method. As a multilayer wiring board using a conductive paste, an ALIVH (Any Layer Interstitial Via Hole) board of Matsushita Group is known.
However, in recent years, a method for manufacturing a laminated circuit board has also been developed by batch pressing due to demands such as further shortening of the process, and conductive paste is also used in this manufacturing method.
The conductive paste used for the interlayer connection of the multilayer circuit board is mainly composed of Ag paste and copper paste, and in order to improve the stability of the manufacturing process and shorten the time, a low-melting-point metal is contained in the main component to form a multilayer wiring board. It is softened at a temperature close to the press temperature to be formed, and is in a state where it is easy to press.
The low melting point metal added to the Ag paste and the copper paste determines the kind and amount of the low melting point metal in consideration of the electrical conductivity and the press temperature when forming the laminated circuit board.

Japanese Patent No. 2740768 Japanese Patent Laid-Open No. 10-96088

  However, when a laminated circuit board is formed by pressing using a conductive paste containing this low melting point metal, a diffusion layer of copper and a low melting point metal is formed on the surface of the copper foil, and the copper foil and the conductive paste In some cases, voids or cracks are generated at the interface, a defect occurs in the connection portion between the copper foil and the conductive paste, and the connection reliability is impaired.

  The present invention relates to a multilayer circuit board using a conductive paste containing a low melting point metal, in which no void is generated at the interface between the copper foil and the conductive paste containing the low melting point metal and the connection reliability is high. The purpose is to provide.

  In the laminated substrate of the present invention, projections having a height of 0.3 μm or more are distributed substantially uniformly by roughening treatment of the copper or copper alloy base foil having a surface roughness of at least one surface of 0.1 μm to 5 μm by etching. Then, a roughened copper foil having a surface roughness Rz of 0.5 to 10 μm and a substrate filled with a conductive paste containing a low melting point metal in a through hole formed in the resin substrate are laminated. .

  In the method for producing a laminated circuit board of the present invention, at least one surface is a granular crystal, the surface roughness is 0.1 μm to 5 μm, and the average particle size in the region from the surface to at least the depth X is 0.3 μm or more. In the copper or copper alloy base foil, protrusions having a height of 0.3 μm or more are distributed substantially uniformly by etching within the region up to the depth X on the surface of the base foil, and the surface roughness Rz is 0.5 to This is a manufacturing method in which a roughening treatment of 10 μm is performed, and the roughened copper foil is laminated with a substrate filled with a conductive paste containing a low melting point metal in a through hole formed in a resin substrate.

  In the method for manufacturing a laminated circuit board according to the present invention, the copper or copper alloy base foil is subjected to a heat treatment, and at least the granular crystal surface to be etched is averaged in a region from the surface to at least the depth X. The thickness is preferably 3 μm or more.

  The copper or copper alloy base foil is preferably an electrolytic foil, and it is particularly preferable that at least the surface of the copper or copper alloy base foil to be etched is a granular crystal.

  The etching is preferably performed by chemical etching or electrolytic etching.

  The present invention relates to a multilayer circuit board using a conductive paste containing a low melting point metal, and has no connection voids or cracks at the interface between the copper foil and the conductive paste containing the low melting point metal, and has high connection reliability. A substrate can be provided.

  The present invention provides a through-hole in a roughened copper foil and a resin substrate obtained by etching and roughing the surface of a base foil (copper foil or copper alloy foil, which may be simply referred to as a base foil or a copper foil if not specifically limited), It is a laminated circuit board configured by laminating an insulating (resin) substrate in which the through holes are filled with a conductive paste containing a low melting point metal.

The roughened copper foil used in the present invention is a resin substrate such as an epoxy resin film, a polyimide film, a liquid crystal polymer film having a heat resistance that can withstand soldering with little change in dielectric properties due to its extremely low hygroscopicity, and polyether. Copper foil with high adhesion strength, fine patterning, and no voids or cracks at the interface between copper foil and low-melting-point metal-containing conductive paste when bonded to an etherketone resin film It is.
In particular, as the resin substrate, a film substrate made of a composition containing 50% or more of an epoxy resin, a polyimide film, and a liquid crystal polymer is suitable.

  The present inventors diligently studied the cause of void generation at the interface between the copper foil surface and the low melting point metal-containing conductive paste, and the voids diffused into the roughened layer of the roughened copper foil. Occasionally, it is clarified that it depends on the amount of low melting point metal diffused and the thickness (depth) diffused into the roughened layer, and the surface roughness of the original foil, the conductivity formed by the surface treatment by etching With regard to the surface roughness of the surface on which the paste is provided, the presence or absence of voids, the presence or absence of cracks, and the adhesiveness with the resin substrate were studied, and the present invention was achieved.

  In the present invention, at least one surface (the surface to be joined to the conductive paste) is etched on the surface of the original foil having a surface roughness of 0.1 μm to 5 μm, and the protrusion has a height of 0.3 μm on the etched surface. Roughly distributed, with a surface roughness Rz of 0.3 to 10 μm and no voids or cracks at the boundary between the roughened copper foil and the conductive paste even when a low melting point metal-containing conductive paste is used. It is a laminated circuit board using a chemical conversion treatment copper foil.

In the present invention, the base foil is a copper foil or a copper alloy foil produced by electrolysis or rolling. The thickness of the original foil is preferably 1 μm to 200 μm, and the surface roughness of at least one side is preferably Rz: 0.1 μm to 5 μm.
The thickness of the original foil is preferably 1 to 200 μm. Such a limitation is that it is very difficult to roughen the surface of the original foil having a thickness of 1 μm or less, and considering the practicality, for example, the original foil used for a high-frequency printed wiring board is used. This is because a foil of 200 μm or more is considered unrealistic.

  The surface roughness of the original foil is defined as Rz: 0.1 μm to 5 μm. A foil having an Rz of 0.1 μm or less is actually difficult to manufacture, and if it can be manufactured, the manufacturing cost is high. It is unsuitable for practical use. Further, an original foil having Rz of 5.0 μm or more may be used, but considering high frequency characteristics and fine patterning, 5.0 μm or less is preferable, and surface roughness is more preferably 2 μm or less.

  In addition, since this original foil uses a conductive paste to form a laminated circuit board, since there is a pressing process at a high temperature, if the copper foil is not flexible, it may break during pressing. Flexibility is required. In order to impart flexibility to the copper foil, a copper foil composed of granular crystals is preferable. In particular, the average size of the granular crystals is preferably 0.3 μm or more, and those having a crystal size of 1 μm or more occupy 10% or more of the copper foil cross section are particularly preferable.

  In the present invention, the above-described base foil is subjected to surface treatment. The surface roughening treatment on the surface of the original foil is performed by electrolytic etching or chemical etching so that the surface roughness Rz on at least one surface is 0.5 to 10 μm on the surface of the original foil. The reason for specifying in this way is that when the surface roughness Rz by the roughening treatment is less than 0.5 μm, the peel strength is low, so it is not satisfactory as a surface roughened copper foil that fulfills its purpose, and Rz: from 10 μm If it is large, the high frequency characteristics are deteriorated and it is not suitable for fine patterning. In view of high frequency characteristics and fine patterning, the surface roughness is preferably 3 μm or less.

In the present invention, the base foil is produced by electrolysis or rolling, and the thickness thereof is preferably 1 μm to 200 μm, and at least one surface is preferably a copper or copper alloy foil having a surface roughness Rz: 0.1 μm to 5 μm. .
The original foil can be either a rolled copper foil or an electrolytic copper foil, but the electrolytic copper foil is more preferable in consideration of the manufacturing cost and the crystal size.
The crystal state of the copper foil includes a granular crystal and a columnar crystal. In the present invention, it is possible to use either crystal state foil, but at least etching roughening is performed in consideration of the uniformity of etching roughening. In the surface layer, the crystal grains are preferably granular crystals. In consideration of etching property and flexibility, it is more preferable that the entire copper foil is composed of a crystal structure of granular crystals.

In addition, when the etching depth is X, the original foil has an average particle diameter of 0.3 μm or more and 25 μm or less from the surface of the original foil to the depth X or at least the depth X. It is preferable. When the average particle size is 0.3 μm or less, it is impossible to obtain a surface roughness that provides satisfactory peel strength, and it is impossible to perform a substantially uniform roughening treatment.
In this specification, “substantially uniformly distributed” and “substantially uniformly roughen” means at least four protrusions having a height of 0.3 μm or more in a visual field of at least 25 μm × 25 μm on the roughened surface. The processing surface which exists above is said.
Further, if the crystal grain size is 25 μm or more, the pitch of the unevenness on the surface becomes too large, which is not suitable for fine patterning.
In the present invention, from the surface to the depth X, X is preferably 4 μm or less. In the case of etching roughening, considering the crystal grain size, there is almost no melting (etching) of 4 μm or more. Therefore, what is important for etching roughening is the crystal grain size within a depth of 4 μm. .

In order to obtain the crystal grain size and uniformity of the original foil, when the original foil is subjected to a heat treatment, a foil capable of performing a stable etching process can be obtained.
The heat treatment of the original foil is to produce a copper foil having uniform crystal grains suitable for etching roughening, in which the average grain size in the etching region is 0.3 μm or more. The heat treatment condition of the original foil is to hold the original foil that has been formed in an atmosphere having a temperature of 50 ° C. or higher. In particular, an excellent copper foil (original 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)
Here, T is temperature (° C.), and 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 within a time suitable for industrial production, the crystal grain size is set to an average crystal grain size of 0.3 μm or more. It is for generating.

Electrolytic copper foil or rolled copper foil, and the original foil obtained by heat-treating these copper foils are roughened by chemical etching or electrolytic etching.
As for chemical etching, etching roughening can be performed using etching solutions such as hydrochloric acid, sulfuric acid, and organic acids. Various commercially available etching solutions may also be used. As an example, Patent Document 1 (Japanese Patent No. 2740768) discloses a corrosion inhibitor such as an inorganic acid + hydrogen peroxide + triazole + a surfactant. Patent Document 2 (Japanese Patent Laid-Open No. 10-96088) discloses an etching solution containing inorganic acid + peroxide + azole + halide.

Examples of the electrolytic etching bath include acidic baths such as sulfuric acid, hydrochloric acid, and sulfamic acid, and alkaline baths such as pyrophosphoric acid, sodium hydroxide, potassium hydroxide, and cyan bath.
If necessary, additives are added to these acid or alkaline solutions. As the additive, those similar to those used for chemical etching, commercially available additives usually used for bright plating solutions, and the like can be used.
As the electrolytic etching method, the surface of the original foil is roughened by etching (dissolving) the surface of the copper foil using the copper foil to be roughened as the anode and the cathode of the counter electrode (side on which copper is deposited) as the cathode.

The amount of current and bath temperature that flow depending on the bath type and bath concentration cannot be generally specified, but the current amount is 3 A / dm ^{2 to} 70 A / dm ² in consideration of the uniformity of roughening and productivity. It is preferable to process in the range. This is because if the current density is 3 A / dm ² or less, the productivity is poor and uniform roughening cannot be performed. Moreover, it is because it will melt | dissolve too much that it is 70 A / dm < ² > or more, or an overcurrent will flow over the copper foil surface, an excessive gas generation | occurrence | production will be produced, and it cannot etch satisfactorily.

If roughened particles are further adhered to the surface subjected to etching roughening, the peel strength is preferably increased. In this case, the adhesion amount of the roughened particles is preferably 150 mg / dm ² or less in consideration of voids. If it is made to adhere 150 mg / dm ² or more, voids and cracks may be generated due to diffusion of the low melting point metal when a conductive paste containing a low melting point metal is provided. The roughening particles adhering to the etched surface-treated foil include Cu or alloy particles of Cu and Mo, or Cu and at least one element selected from the group consisting of Ni, Co, Fe, Cr, V and W. It is preferable that

  The low melting point metal added to the conductive paste is a metal having a melting point of a single metal of 460 ° C. or lower, and specifically includes Zn, Sn, Pb, Bi, In or alloys containing these metals.

Ni, Zn, Cr and / or chromate film may be provided on the etched surface or the surface to which roughened particles are attached after etching for the purpose of heat resistance and rust prevention. If necessary, silane coupling treatment or rust prevention treatment + silane It is preferable to perform coupling. In particular, a liquid crystal polymer resin film or the like is effective because it chemically bonds with Ni metal or Ni alloy to increase the peel strength.
The surface-roughened foil subjected to the above surface treatment was provided with a through hole in a resin substrate such as a liquid crystal polymer film or a polyether ether ketone film, and the through hole was filled with a conductive paste containing a low melting point metal. A substrate is attached to form a laminated substrate, and a plurality of the laminated substrates are laminated to form a laminated circuit substrate.

  Hereinafter, the present invention will be described in more detail based on embodiments, but the present invention is not limited to these embodiments.

Using a titanium drum having a Rz = 1.5 μm as a cathode by buffing a Ti plate, a 12 μm electrolytic copper foil was produced in each plating bath and conditions.
Thereafter, roughening treatment was performed by chemical etching or electrolytic etching.

[Electrolytic copper foil]
Granular crystal copper foil: original foil 1
Copper sulfate pentahydrate 280 g / L, sulfuric acid 80 g / L, sulfuric acid acidic copper sulfate electrolyte containing 35 ppm chloride ion, low molecular weight gelatin 15 ppm with an average molecular weight of 3000, hydroxyethyl cellulose 3 ppm, 3-mercapto-1-propane Electrolysis with the addition of 1 ppm sodium sulfonate, electrolyte temperature of 40 ° C., flow rate of 0.2 m / min, current density of 50 A / dm ² , thickness: 12 μm, surface roughness Rz of etching surface: 1.24 μm Copper foil was made. The obtained copper foil had granular crystals, and the average crystal grain size in the range (etching region) from the etching surface to 2 μm was 0.5 μm, and the crystal grain size in this range was 1 μm or more was 12%. .

Columnar crystal copper foil: original foil 2
As an electrolytic solution, an electrolytic solution containing 90 g / L of copper, 100 g / L of sulfuric acid, 20 ppm of chlorine ions and 300 ppm of hydrolyzed glue was further added with 2 ppm of glue before hydrolysis, and the liquid temperature was 55 ° C. and the current density. Columnar electrolytic copper foil having a thickness of 12 μm and a surface roughness Rz of 2.1 μm under the condition of 55 A / dm ² .

[Example 1]
The original foil 1 was used and chemical etching was performed.
The chemical etching was performed by a spray method using CZ8101 manufactured by MEC as an etchant. Treatment time: 1 minute, and then Ni: 0.1 mg / dm ² , Zn: 0.1 mg / dm ² , Cr: 0.1 mg / dm ² were adhered, and a silane coupling agent was adhered to the outermost layer.
The surface-roughened copper foil obtained above was pressed and pasted on a liquid crystal polymer film and a polyether ether ketone resin film, and the peel strength was confirmed.
In addition, the void is confirmed by performing tin plating (corresponding to 100% of the low melting point metal of the low melting point metal-containing conductive paste diffusing into the roughened surface) on the surface of the surface roughened copper foil. This was heated at 320 ° C. to observe the cross section.

[Example 2]
The original foil 2 was used and chemical etching was performed.
The chemical etching was performed by a spray method using CZ8101 manufactured by MEC as an etchant. Treatment time: 2 minutes Thereafter, Ni 0.1 mg / dm ² , Zn 0.1 mg / dm ² and Cr 0.1 mg / dm ² were adhered, and a silane coupling agent was adhered to the outermost layer. The roughened copper foil obtained above was attached to a liquid crystal polymer film and a polyether ether ketone resin film with a press to confirm the peel strength.
In addition, the void is confirmed by performing tin plating (corresponding to 100% of the low melting point metal of the low melting point metal-containing conductive paste diffusing into the roughened surface) on the surface of the surface roughened copper foil. This was heated at 320 ° C. to observe the cross section.

Example 3
The original foil 1 was used and electrolytic etching was performed.
Etching solution 100 g / L of sulfuric acid, 15 ppm of low molecular weight gelatin having an average molecular weight of 3000, 5 ppm of hydroxyethyl cellulose, 1 ppm of sodium 3-mercapto-1-propanesulfonate, current density 50 A / dm ² , treatment time: 15 seconds Thereafter, Ni: 0.1 mg / dm ² , Zn: 0.1 mg / dm ² , and Cr: 0.1 mg / dm ² were attached, and a silane coupling agent was attached to the outermost layer. The roughened copper foil obtained above was attached to a liquid crystal polymer film and a polyether ether ketone resin film with a press to confirm the peel strength.
In addition, the void is confirmed by performing tin plating (corresponding to 100% of the low melting point metal of the low melting point metal-containing conductive paste diffusing into the roughened surface) on the surface of the surface roughened copper foil. This was heated at 320 ° C. to observe the cross section.

Example 4
The original foil 1 was heat-treated at 150 ° C. for 5 hours. The average crystal grain size in the range (etching region) from the etching surface of the foil after heating to 2 μm was 0.6 μm, and the crystal grain size of 1 μm or more in this range was 28%. This heat-treated foil was subjected to chemical etching. The etching was performed by using a spray type CZ8101 manufactured by MEC. Processing time is 1 minute. Thereafter, Ni: 0.1 mg / dm ² Zn: 0.1 mg / dm ² and Cr: 0.1 mg / dm ² were adhered, and a silane coupling agent was adhered to the outermost layer. The surface-roughened copper foil obtained above was attached to a liquid crystal polymer film and a polyether ether ketone resin film with a press to confirm the peel strength.
In addition, the void is confirmed by performing tin plating (corresponding to 100% of the low melting point metal of the low melting point metal-containing conductive paste diffusing into the roughened surface) on the surface of the surface roughened copper foil. This was heated at 320 ° C. to observe the cross section.

Example 5
The original foil 1 was heat-treated at 150 ° C. for 5 hours. The average crystal grain size in the range (etching region) from the etching surface of the foil after heating to 2 μm was 0.6 μm, and the crystal grain size of 1 μm or more in this range was 28%. This heat-treated foil was subjected to electrolytic etching. The etching solution is 100 g / L sulfuric acid, 15 ppm low molecular weight gelatin with an average molecular weight of 3000, 5 ppm hydroxyethyl cellulose, 1 ppm sodium 3-mercapto-1-propanesulfonate, current density: 50 A / dm ² , treatment time: After 15 seconds, Ni: 0.1 mg / dm ² , Zn: 0.1 mg / dm ² , Cr: 0.1 mg / dm ² were adhered, and a silane coupling agent was adhered to the outermost layer. The surface-roughened copper foil obtained above was attached to a liquid crystal polymer film and a polyether ether ketone resin film with a press to confirm the peel strength.
In addition, the void is confirmed by performing tin plating (corresponding to 100% of the low melting point metal of the low melting point metal-containing conductive paste diffusing into the roughened surface) on the surface of the surface roughened copper foil. This was heated at 320 ° C. to observe the cross section.

Example 6
The original foil 1 was heat-treated at 180 ° C. for 5 hours. The average crystal grain size in the range (etching region) from the etching surface of the foil after heating to 2 μm was 0.75 μm, and the crystal grain size of 1 μm or more in this range was 35%. The heated foil was subjected to electrolytic etching. The etching solution is 100 g / L of sulfuric acid, 15 ppm of low molecular weight gelatin having an average molecular weight of 3000, 5 ppm of hydroxyethyl cellulose, 1 ppm of sodium 3-mercapto-1-propanesulfonate, current density 50 A / dm ² , treatment time: 17 Furthermore, the roughening process was further performed by the following plating conditions 1 and 2 so that the roughening amount was 75 mg / dm ² .
Plating condition 1
Copper sulfate (as Cu metal) 1-10 g / dm ³
Sulfuric acid 30-100 g / dm ³
Ammonium molybdate (as Mo metal) 0.1-5.0 g / dm ³
Current density 10-60A / dm ²
Energizing time 1 to 45 seconds Bath temperature 20 to 60 ° C
・Plating condition 2
Copper sulfate (as Cu metal) 20-70 g / dm ³
Sulfuric acid 30-100 g / dm ³
Current density 5 to 45 A / dm ²
Energizing time 1 second to 1 minute Bath temperature 20 ° C to 60 ° C

After the roughening treatment, Ni: 0.1 mg / dm ² , Zn: 0.1 mg / dm ² , Cr: 0.1 mg / dm ² were attached, and a silane coupling agent was attached to the outermost layer. The surface-roughened copper foil obtained above was attached to a liquid crystal polymer film and a polyether ether ketone resin film with a press to confirm the peel strength.
In addition, the void is confirmed by performing tin plating (corresponding to 100% of the low melting point metal of the low melting point metal-containing conductive paste diffusing into the roughened surface) on the surface of the surface roughened copper foil. This was heated at 320 ° C. to observe the cross section.

[Comparative Example 1]
Ni: 0.1 mg / dm ² , Zn: 0.1 mg / dm ² , and Cr: 0.1 mg / dm ² were attached on the original foil 1, and a silane coupling agent was attached to the outermost layer. The obtained roughened copper foil was affixed to a liquid crystal polymer film and a polyether ether ketone resin film with a press to confirm the peel strength.
In addition, the void is confirmed by performing tin plating (corresponding to 100% of the low melting point metal of the low melting point metal-containing conductive paste diffusing into the roughened surface) on the surface of the surface roughened copper foil. This was heated at 320 ° C. to observe the cross section.

[Comparative Example 2]
Ni: 0.1 mg / dm ² , Zn: 0.1 mg / dm ² , and Cr: 0.1 mg / dm ² were attached on the original foil 2, and a silane coupling agent was attached to the outermost layer. The obtained roughened copper foil was affixed to a liquid crystal polymer film and a polyether ether ketone resin film with a press to confirm the peel strength.
In addition, the void is confirmed by performing tin plating (corresponding to 100% of the low melting point metal of the low melting point metal-containing conductive paste diffusing into the roughened surface) on the surface of the surface roughened copper foil. This was heated at 320 ° C. to observe the cross section.

[Comparative Example 3]
Copper sulfate sulfate pentahydrate 350g / L, sulfuric acid 80g / L, sulfuric acid copper sulfate electrolyte containing 35ppm of chlorine ion, low molecular weight gelatin 15ppm of average molecular weight 3000, hydroxyethyl cellulose 3ppm, 3-mercapto-1-propane Electrolysis with the addition of 1 ppm of sodium sulfonate, electrolyte temperature of 50 ° C., flow rate of 0.2 m / min, current density of 20 A / dm ² , thickness: 12 μm, surface roughness Rz of etching surface: 1.24 μm Copper foil was made. The obtained copper foil had granular crystals, and the average crystal grain size in the range (etching region) from the etching surface to 2 μm was 0.2 μm, and the crystal grain size of 1 μm or more in this range was 5%.
The chemical etching was performed by a spray method using CZ8101 manufactured by MEC as an etchant. Processing time: 2 minutes. Thereafter, Ni: 0.1 mg / dm ² , Zn: 0.1 mg / dm ² , and Cr: 0.1 mg / dm ² were attached, and a silane coupling agent was attached to the outermost layer. The obtained roughened copper foil was affixed to a liquid crystal polymer film and a polyether ether ketone resin film with a press to confirm the peel strength.
In addition, the void is confirmed by performing tin plating (corresponding to 100% of the low melting point metal of the low melting point metal-containing conductive paste diffusing into the roughened surface) on the surface of the surface roughened copper foil. This was heated at 320 ° C. to observe the cross section.

[Comparative Example 4]
Copper sulfate sulfate pentahydrate 350g / L, sulfuric acid 80g / L, sulfuric acid copper sulfate electrolyte containing 35ppm of chlorine ion, low molecular weight gelatin 15ppm of average molecular weight 3000, hydroxyethyl cellulose 3ppm, 3-mercapto-1-propane Electrolytic copper with addition of 1 ppm of sodium sulfonate, electrolyte temperature of 50 ° C., flow rate of 0.2 m / min, current density of 20 A / dm ² , thickness: 12 μm, surface roughness Rz of etching surface: 1.24 μm The foil was made. The obtained copper foil had granular crystals, and the average crystal grain size in the range (etching region) from the etching surface to 2 μm was 0.2 μm, and the crystal grain size of 1 μm or more in this range was 5%.
In the electrolytic etching, sulfuric acid 100 g / L, low molecular weight gelatin 15 ppm having an average molecular weight of 3000, hydroxyethyl cellulose 5 ppm, sodium 3-mercapto-1-propanesulfonate 1 ppm are added as an etching solution, and current density is 50 A / dm ^2. Treatment time: 15 seconds, Ni: 0.1 mg / dm ² , Zn: 0.1 mg / dm ² , Cr: 0.1 mg / dm ² were then deposited, and a silane coupling agent was deposited on the outermost layer. The obtained roughened copper foil was affixed to a liquid crystal polymer film and a polyether ether ketone resin film with a press to confirm the peel strength.
In addition, the void is confirmed by performing tin plating (corresponding to 100% of the low melting point metal of the low melting point metal-containing conductive paste diffusing into the roughened surface) on the surface of the surface roughened copper foil. This was heated at 320 ° C. to observe the cross section.

[Comparative Example 5]
To Motohaku 1 performs roughening treatment to the roughening particles 189 mg / dm ² deposited, after the surface roughness Rz2.3Myuemu, ^{then, Ni: 0.1mg / dm 2,} Zn: 0.1mg / dm 2 Cr: 0.1 mg / dm ² was adhered, and a silane coupling agent was adhered to the outermost layer. The obtained roughened copper foil was affixed to a liquid crystal polymer film and a polyether ether ketone resin film with a press to confirm the peel strength.
In addition, the void is confirmed by performing tin plating (corresponding to 100% of the low melting point metal of the low melting point metal-containing conductive paste diffusing into the roughened surface) on the surface of the surface roughened copper foil. This was heated at 320 ° C. to observe the cross section.

Evaluation of peel strength of roughened copper foil (liquid crystal polymer)
A liquid crystal polymer film was laminated on the surface-roughened copper foil prepared in Examples and Comparative Examples, a constant pressure was applied at 280 ° C., held for 10 minutes, then cooled and pasted, and peel strength was measured.

[Polyetheretherketone resin film]
A polyether ether ketone resin film was laminated on the roughened copper foil prepared in Examples and Comparative Examples, a constant pressure was applied at 205 ° C., held for 10 minutes, then cooled and pasted, and peel strength was measured.

[Measurement of peel strength]
The peel strength between the film and the surface roughened foil thus obtained was measured. The peel strength was measured in accordance with JIS C6471 by peeling in the 180 degree direction. The results are shown in Table 1.

[Void generation in low melting point metals]
The state of occurrence of voids was confirmed for each Example and Comparative Example 5 having a peel strength equivalent to that of the Example, and the results are shown in Table 1.

As can be seen from Table 1, the laminated circuit board of the present invention has sufficient peel strength, does not cause voids and cracks, and can produce and provide an excellent laminated circuit board. On the other hand, in the conventional copper foil having a large amount of roughened particles as in Comparative Example 5, the peel strength is sufficient, but voids and cracks are observed due to the diffusion of the low melting point metal.
In addition, a granular copper foil that maintains a certain value of crystal grain size or is uniformed by heat treatment has high peel strength and is excellent as a copper foil for laminated circuit boards that form fine patterns. By using such a copper foil, an excellent laminated circuit board can be provided.

ADVANTAGE OF THE INVENTION According to this invention, in the laminated circuit board using the electrically conductive paste containing a low melting metal, the high quality thing which does not produce a void and a crack between copper foil and an electrically conductive paste can be provided. There is a possibility of use in the manufacture of circuit boards for various electronic components.

Claims (9)

  Protrusions having a height of 0.3 μm or more are distributed substantially uniformly by roughening the surface of the copper or copper alloy base foil having a surface roughness of at least one surface of 0.1 μm to 5 μm by etching, and the surface roughness Rz is A laminated circuit board obtained by laminating a roughened copper foil of 0.5 to 10 μm and a board filled with a conductive paste containing a low melting point metal in a through hole formed in a resin board.   The laminated circuit board according to claim 1, wherein the copper or copper alloy base foil is an electrolytic foil.   2. The laminated circuit board according to claim 1, wherein at least the surface of the copper or copper alloy base foil to be etched is a granular crystal.   The multilayer circuit board according to claim 1, wherein the etching is chemical etching.   The multilayer circuit board according to claim 1, wherein the etching is electrolytic etching.   A copper or copper alloy base foil having at least one surface of a granular crystal, a surface roughness of 0.1 μm to 5 μm, and an average particle size of at least a depth X from the surface of 0.3 μm or more, Protrusions having a height of 0.3 μm or more are distributed approximately uniformly by etching within the region up to the depth X on the original foil surface, and a roughening treatment is performed so that the surface roughness Rz is 0.5 to 10 μm. A method for manufacturing a laminated circuit board, in which a copper foil and a substrate filled with a conductive paste containing a low melting point metal in a through hole formed in a resin substrate are laminated.   The copper or copper alloy base foil is subjected to heat treatment, and at least the granular crystal surface to be etched has an average particle size of 0.3 μm or more from the surface to at least the depth X, and the heat treatment base foil is roughened. The method for producing a laminated circuit board according to claim 6, wherein a roughening treatment copper foil is applied.   The method for manufacturing a laminated circuit board according to claim 6, wherein the etching is chemical etching. The method for manufacturing a laminated circuit board according to claim 6, wherein the etching is electrolytic etching.