JPH0260189A - Manufacture of thin copper foil plated circuit board - Google Patents

Abstract

PURPOSE:To enable the manufacture of a thin copper plated substrate whose thickness is very accurate by a method wherein a copper foil plated circuit board, formed of the copper foil with specified average thickness and an electrical insulator, is etched at a prescribed speed using a hydrogen peroxide/sulfuric acid water solution. CONSTITUTION:Etching is performed onto the the whole face of copper foil of a copper foil plated circuit board, which is formed of copper foil whose average thickness is 12-16mum and variation in thickness with the average thickness is + or -1.0mum and an electric insulator, at a speed of 0.01-0.3mum/s using a hydrogen peroxide/sulferic acid water solution, and the etching is made to stop when the residual copper foil grows 3-12mum in average thickness. By this setup, the circuit substrate plated with thin copper foil whose average thickness is 3-12mum and variation in thickness is within + or -1.0mum can be easily manufactured.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a copper foil-clad laminate, a copper-clad film, and a copper foil-clad laminate manufactured from copper foil and an electrical insulator for manufacturing printed wiring boards on which electronic components are mounted. Copper foil-clad circuit boards such as copper-clad sheets or reinforced copper foil, with an average thickness of 3 μm = 12 gvn
This is a method for manufacturing a thin copper foil-clad circuit board in which the thickness variation with respect to the desired thickness is within ±1.0 μm.

[Conventional technology and its problems]

Copper foil-clad circuit boards are manufactured by laminating copper foil and insulators, usually by lamination molding, etc. The copper foil used is 105/111.70 mm thick, 35 μrn, made by electrolytic method,
184.12fm etc. are mass produced, and copper foils such as 55-19Ii formed on carriers such as Aluminum 12 foil are also produced. Further, there is copper foil made by rolling, but due to the manufacturing method, the thinner the foil becomes, the more expensive it becomes, and thinner foils have not been practically put into practical use.

When such a thin copper foil is used for lamination molding, the thin copper foil tends to wrinkle, making it extremely difficult to overlap the copper foil with the insulator. In addition, copper foil formed on a carrier such as aluminum foil improves this point, but it is expensive, and furthermore, the process of removing the carrier such as aluminum foil is required before forming printed wiring using copper foil. There was a question of necessity.

A known method is to pre-etch a copper foil-clad circuit board with an etching solution such as copper chloride or iron chloride in the printed wiring board processing process to remove a thin layer of copper foil, and then use it in the printed wiring board manufacturing process. , increase the amount of copper foil removed by preliminary etching to several microns or more, or
It has been recognized that when etching a large area of mm x 500 + nm nm, the variation in the thickness of the remaining copper foil becomes large, making it impossible to produce a thin copper foil-clad circuit board that can be commercialized.

For example, in Japanese Patent Application Laid-Open No. 62-200796, an average thickness of 1
It is disclosed that an ultra-thin copper foil-clad circuit board can be manufactured by mechanically polishing, electrochemically polishing, or chemically etching copper foil of eight or more units to a thickness of 12 mm or less.

However, in the case of the method shown in Example 1 of this patent application,
340mm x 340 + tm square copper foil average thickness 1
There is a description that a thin copper foil having an average thickness of 101 na was obtained by etching the entire surface of a copper foil of No. 8- with an etching solution consisting of cupric chloride/hydrochloric acid. In spray etching, the etching speed is 0.
, 5 t-/sec, and a difference in etching time of 1 second appears as a difference in average thickness of 0.51 nn, and the difference in effective contact time of the etching solution depending on location is added. . As a result, when etching only 5 copper-clad laminates by 6 μm, the average variation in 1q thickness is ±3.5-1 the variation in desired thickness ±
It is 4.8 Inn, which is so large that it corresponds to the amount of etching. Furthermore, this tendency becomes more pronounced as the amount of etching increases and as the volume of production increases, so it is impossible to manufacture ultra-thin copper foil-clad circuit boards with high precision that can be commercialized. there were. Further, the other methods described in this publication, such as mechanical polishing and electrolytic polishing, were also similar and could not be commercialized. Furthermore, if a thin copper-clad circuit board whose entire surface is etched with copper foil is immediately used for circuit formation using a normal etching solution as described in the example of this patent application, this problem does not arise. The surface of the remaining ffI foil on the thin copper-clad circuit board was extremely active and would rust in a short period of time if left in the air.

[Means for Solving the Problems] The present invention has been made as a result of intensive studies on a method for manufacturing with high productivity a high-precision thin copper foil-clad circuit board that can be used as a large-sized circuit board.1. Using a copper-clad circuit board that can be mass-produced and uses as thin a copper foil as possible, it is etched using a hydrogen peroxide/sulfuric acid-based etching solution at a much slower rate than conventional etching. The entire surface of the foil is etched to an average thickness of 3 to 12 mm. The present invention was achieved by discovering that a thin copper-clad circuit board with high thickness accuracy and a thickness variation within ±1.0 haze can be obtained.

In other words, the present invention provides a copper foil-clad circuit board manufactured from a copper foil and an electrical insulator with an average thickness of 12 to 16 μm and a thickness variation of ±1.02 or less with respect to the average thickness, by heating the copper foil-clad circuit board with hydrogen peroxide. /0.01~ using copper etching solution with sulfuric acid aqueous solution
The entire surface of the copper foil is etched at a rate of 0.3 pm/sec, and etching is stopped when the average thickness of the remaining copper foil is 3 to 12 p,n, and the variation in the desired thickness of the remaining copper foil is ±1. Ot
- A method for producing a thin copper foil-clad circuit board, characterized in that the copper etching solution using hydrogen peroxide/sulfuric acid aqueous solution contains 0.1 to 5 w/v% of alcohol as an auxiliary agent. The hydrogen peroxide concentration should be 1.5 to 4%/ν% and the sulfuric acid concentration should be 3 to 7%/ν%. Also, after etching the entire surface of the copper foil, immediately clean the remaining copper foil surface with a water-soluble rust inhibitor. This is a method for manufacturing a thin copper foil-clad circuit board, which is characterized by processing.

The configuration of the present invention will be explained below.

The copper foil-clad circuit board manufactured from the copper foil and electrical insulator of the present invention uses a copper foil having an average thickness of 12 to 16 mm and a thickness variation of within ±1.0 IrTn with respect to the average thickness. There is no particular limitation as long as it is a suitable material, and various commercially available products used for electronic and electrical materials can be used.
Single-sided or double-sided copper-clad film, sheet, fiber reinforced 1 [
! ! These include green-green resin layered plates, metal core laminates, and multilayer shield plates with printed wiring networks formed on the inner layer. The electrical insulator layer is made of films or sheets made of polyimide resin, polyester resin, etc., thermosetting resin or heat-resistant thermoplastic resin, glass (E glass, D glass, S glass, quartz glass, etc.), ceramics. (Alumina, boron nitride,
Others), fibers made of one or more combinations of fully aromatic polyamides, polyimides, semi-carbons, fluorine resins, and other heat-resistant engineering pluses, porous films using Chico Nobu, etc. These include those manufactured using prepreg in combination with a sheet-like reinforcing base material, or those manufactured by coating an iron, aluminum plate, etc. with an insulating adhesive or adhesive film. In addition, in the case of ordinary copper-clad laminates, due to the pressure of lamination molding, the surface of the copper foil partially reflects the unevenness of the reinforcing base material.
Although it has some degree of waviness, it is also possible to use a material in which the waviness is mechanically replaced with minute irregularities or the like or removed. In addition, as a method for manufacturing copper-clad laminates or sheets using thin copper foil of 12 to 16 μm,
A preferred method is to insert a sheet of about 40 to 100 mm, such as aluminum foil, which has a higher coefficient of thermal expansion than the copper foil, between the copper foil and the mirror plate, and perform lamination molding.

The copper etching solution using a hydrogen peroxide/sulfuric acid aqueous solution of the present invention has hydrogen peroxide, sulfuric acid, and stable hydrogen peroxide as essential components, and serves as a copper dissolution promoter and to control the state of the etched copper foil surface. It is an aqueous solution containing auxiliary agents and the like.

Here, the concentration of hydrogen peroxide (I+20□) is usually 0.7
~14 w/v% (approximately 0.2 to 4.1 mol/2), sulfuric acid (
The concentration of 11□So,) can usually be used in the range of 1 w/ν% (approximately 0.1 mol/1) to 25 w/v% depending on the control conditions (particularly by using low temperatures), but it is not practical. In order to perform highly accurate whole surface etching within a certain range, hydrogen peroxide should be 1.5 to 4 w/v% and sulfuric acid should be 3 to 4%. For example, 0.1 to 5 w/v% of alcohol was blended as an auxiliary agent. Examples of alcohols used as auxiliaries include monohydric alcohols such as methanol, ethanol, propatool, and butanol; dihydric alcohols such as ethylene glycol, propylene glycol, butanediol, and bentanediol; and trihydric or higher alcohols such as glycerin and pentaerythritol. Examples of other additives include glycol ethers such as polyethylene glycol; nitrogen-containing organic cyclic compounds such as aminobenzoic acid, aminotetrazole, and phenylurea.

Further, copper dissolves during the night due to etching, but it is preferable to adjust the concentration of this copper within a range of 5 to 60 g/ffi.

Etching is performed using the above hydrogen peroxide/sulfuric acid aqueous solution, but in the present invention, the etching rate is reduced compared to hard etching performed in normal pattern formation, and the etching rate is reduced to 0. Etching rates in the range O1 to 0.3 trm/sec, more preferably in the range 0.03 to 0.20/-/sec are used. If the etching speed is faster than 0.3 haze/second, there will be slight differences in the amount of etching due to differences in etching time, temperature, component concentration, dissolved copper concentration, etc., which are below the controllable range of etching liquid conditions. This is manifested as variations depending on the location of the copper clad sheets, and variations in the average thickness when a large number of sheets are processed, and the thickness range relative to the desired copper foil thickness is ±1. This is not preferable because it becomes difficult to manufacture thin copper-clad circuit boards with high precision within Otnn, the extra burden of quality control etc. increases, and the number of defective products increases. Furthermore, if the etching rate is slower than 0.01 μm/sec, etching takes a long time and is not practical.

In the above, methods for slowing down the etching speed include reducing the concentration, temperature, or amount of contact of the etching solution on the copper foil surface (spray pressure or number of spray nozzles in the case of a spray method). It is preferable to lower the chemical concentration of the etching solution, to lower the chemical concentration of the etching solution, or to a combination thereof. In the case of the preferred etching solution composition described above, the temperature is preferably 25 to 50°C.

As the etching method in the manufacturing method of the present invention, spray etching is usually suitable and is carried out horizontally or vertically. In order to obtain a copper foil of a predetermined thickness by etching, a method is used in which the etching rate is measured under predetermined etching conditions using an etching solution and the etching time is set. For example, if you use a double-sided copper-clad board with copper foil of the same thickness on both sides, and you want to make both sides horizontally the same thickness at the same time, control the spray pressure etc. so that the etching speed on both the top and bottom is the same. The etching process is performed by adjusting the etching speed and etching for a predetermined period of time. In addition, conventional etching machines usually use a method in which the spray direction of the nozzle is set as perpendicular to the copper foil surface of the laminate, which moves at a constant speed of several meters or less, but the present invention In this case, the spray nozzle may be sprayed uniformly onto the surface of the copper foil of the copper clad plate, and the spray nozzle may be tilted at an angle of about 30° to 50°.

The copper foil surface of the laminate treated with the above-mentioned hydrogen peroxide/sulfuric acid aqueous etching agent is cleaned, dried appropriately, and a rust preventive agent is applied to protect the copper foil surface.

Here, cleaning may be any known impurity removal method such as neutralization, acid washing, water washing, hot water washing, etc., taking into account the stabilizer and other components of the copper etching solution using hydrogen peroxide/sulfuric acid aqueous solution. Select as appropriate, but after washing with water or hot water, add 1 part of soda
After neutralization treatment at 20 to 50°C with an aqueous solution of ~5 wt%, a known copper rust inhibitor, for example, an azole compound such as benzotriazole, was added to the solution at 0.01=l i
It is preferable to carry out the immersion treatment at 20 to 50''C in an aqueous solution containing Vt% and appropriately combined with a surfactant or the like.

In addition, after anti-rust treatment, resins that can be peeled off, such as polyethylene, polypropylene, ethylene-pyrene resin, ethylene-vinyl acetate resin, vinylidene chloride, polyacrylate copolymer, 1,2-polybutadiene resin, polyester resin, etc. Thermoplastic resin films and photoresist films; general-purpose solvent-soluble resins such as paraffin wax, polyethylene wax, rosin, and low-molecular-weight polystyrene; photoresist resin liquid, etc., coated on the copper foil surface by pressure bonding, etc. It is also preferable to do so.

〔Example〕

Hereinafter, the present invention will be specifically explained with reference to Examples and Comparative Examples. The thickness of the etched copper foil was measured using an eddy current method.

Example 1 Using 100 sheets of glass cloth base epoxy resin laminates, 700 x 1020 mm, plate thickness 1.6 mm, copper foil with an average thickness of 15 mm treated on one side and low profile treated on both sides, the average copper foil thickness was A thin copper-clad circuit board of No. 9 was manufactured.

The copper foil thickness range of the double-sided copper clad board used was 15°0p' on average.
The maximum s is 15.5 trm, the minimum is 14.5 trm, and the variation is 0.5 trm, and the surface unevenness of the copper foil is 3.6 to 4.3 depending on the degree of surface unevenness. It was Im.

Etching was performed using a horizontal etching machine under the following conditions.

Then, after immersing in a 5% Na2CO3 aqueous solution at room temperature for 30 seconds, it was immersed in a benzotriazole aqueous solution with a concentration of 0.3%.
It was immersed at 0°C for 30 seconds and dried with hot air at 100°C for 30 seconds.

For all 100 thin copper clad plates obtained, the copper foil thickness was measured at any point within 18 rectangles obtained by dividing the thickness of the copper foil into three equal parts vertically and horizontally, and the average thickness was 8.
．． 9-1 Maximum 9.5-1 Minimum 8.6 μm, the variation with respect to the average thickness is ±0.6 tnn, the variation with respect to the desired thickness is ±0.5 tim, and 95% of the measurement points are 8.6 μm. It was in the range of ~9.4pm.

Moreover, the surface unevenness was 2.0 to 3.0-.

Furthermore, the obtained thin copper clad plate was heated at 25°C and 160%RH for 3
Although it was held for 0 hours, no rust was observed.

Comparative Example 1 Using the following ordinary cupric chloride etching solution, the same copper-clad laminate as in Example 1 was etched to produce nine thin copper-clad circuit boards.

First, using this etching solution, the etching rate was measured using a 70-copper foil clad plate under the following conditions.

As a result, it was confirmed that the etching rate was 0.5 μWl/sec. Using 15- copper foil clad plate, 6, OF
The etching time required to etch to an average thickness of 9.0 is 12 seconds.

Therefore, in the etching machine used in Example 1, it is necessary to set the conveyor speed to 10 m/min.
Since this etching machine could not achieve this speed, the following methods are possible with this etching machine:
The spray nozzles for 1.5 m of the effective etching chamber length of 2.0 m were blocked, and the conveyor speed was reduced to 2.5 m.
/min, and the same five double-sided copper-clad laminates as in Example 1 were used for testing.

For the five thin copper clad boards obtained, the thickness of the copper foil was determined in Example 1.
Measured in the same way as average 8.7-1 maximum 10.6
Irla, minimum 5.2-, variation for average thickness is ±3.5 haze, variation for desired thickness is ±4.8-
, and 48% of the measurement points had a copper foil thickness of 8.5 to 9.5μ.
It was in the range of m.

Moreover, the surface unevenness was 3.8 to 4.5 μm.

Further, when the obtained copper clad plate a was held at 25°C and 160% R11, spotty rust appeared after 3 hours.

Example 2 In Example 1, a double-sided copper clad board with an average thickness of 12 mm was manufactured under the following etching conditions.

When the thickness of the copper foil of the obtained thin copper clad plate was measured, the average thickness was 1.
2.1 haze, maximum 12.6 g-1 minimum 11.6-, the variation with respect to the average thickness was ±0.5 lfm, and the variation with respect to the desired thickness was ±0.6-.

Moreover, the surface unevenness was 3.1 to 3.6 μm.

Example 3 In Example 1, a double-sided copper-clad laminate having an average thickness of 12 haze copper foil with one side low profile treated was used as the double-sided copper-clad laminate, and the conveyor speed of the etching machine was set to 1.
Thin copper clad boards of five desired thicknesses were manufactured in exactly the same manner except that the speed was changed to 5 m/min.

The copper foil thickness range of the double-sided copper clad plate used was an average of 12° Opv.
a, maximum 12.41na, minimum 11.6uw, variation ±0, 411va, and the surface unevenness of the copper foil is 4.2 ~
There were 5.1 units.

When the thickness of the copper foil of the obtained thin copper clad plate was measured, the average thickness was 4.
．． 7-1 Maximum 5.4 trm, minimum 4.0 pm, variation with respect to average thickness is ±0.7 units, variation with respect to desired thickness is ±1. It was Otna.

Moreover, the surface unevenness was 2.3 to 3.3 fm.

[Operation and effects of the invention]

As is clear from the detailed description of the invention, examples, and comparative examples, conventional alkaline etching methods cause large variations in copper foil thickness that are comparable to the amount of etching. The method of the present invention has extremely high thickness accuracy and can be compared to conventional ultra-thin copper foil.
It is understood that veneers are easy to manufacture.

As a result, thin copper uneven laminates, which could previously only be manufactured using methods such as using copper foils such as 5- and 9-layers formed on carriers such as expensive aluminum foils, electroless plating or vapor deposition, have been made with high precision. It can be easily manufactured at low cost, and its industrial significance is extremely large.

Patent applicant: Mitsubishi Gas Chemical Co., Ltd.

Claims (1)

[Scope of Claims] 1. A copper foil-clad circuit board manufactured from a copper foil and an electrical insulator with an average thickness of 12 to 16 μm and a thickness variation of ±1.0 μm or less with respect to the average thickness is heated using hydrogen peroxide/sulfuric acid. Using an aqueous copper etching solution, the entire surface of the copper foil is etched at a rate of 0.01 to 0.3 μm/sec, and the etching is stopped when the average thickness of the remaining copper foil is 3 to 12 mm. A method for manufacturing a thin copper foil-clad circuit board, characterized in that the variation in thickness is within ±1.0 μm. 2 The hydrogen peroxide/sulfuric acid aqueous solution copper etching solution contains 0.1 to 5 w/v% alcohol as an auxiliary agent, and has a hydrogen peroxide concentration of 1.5 to 4 w/v% and a sulfuric acid concentration of 3 to 5 w/v%. The method for producing a thin copper foil-clad circuit board according to claim 1, wherein the content is 7 w/v%. 3. The method for manufacturing a thin copper foil-clad circuit board according to claim 1, wherein the remaining copper foil surface is treated with a water-soluble rust preventive agent immediately after etching the entire surface of the copper foil.