JPH0222887A - Manufacture of thin copper foil clad circuit board - Google Patents

Abstract

PURPOSE:To obtain a thin copper foil covered circuit board whose copper film has low thickness dispersion and high thickness accuracy by etching whole surface of a copper foil in a copper clad circuit board manufactured from the copper foil and an electric insulator at a predetermined slow speed by using a copper etchant to remove a predetermined proportion of the original thickness of the copper foil to obtain a residual thickness of desired value. CONSTITUTION:A film, a multilayer shielding plate, etc., whose one side or both sides are covered with a copper foil having a thickness of 18mum, are used as copper foil clad circuit boards. As a electric insulator layer, a film or a sheet of polyester resin, etc., is used. The main agents of a copper etchant are hydrogen peroxide/sulfuric acid, iron chloride, etc., and in case where hydrogen peroxide/sulfuric acid system is used, the respective concentrations are, 2-4w/v% of hydrogen peroxide, 3-7w/v% of sulfuric acid, and at temperature of 25-50 deg.C a copper concentration of 30-60g/l is preferable. The concentrations, the temperature, and contact quantity of the etchant onto the copper foil surface dependent of the spray pressure or the number of nozzles, are adjusted to make the etching spread slow. Thus, the etching speed is made to be 0.05-0.3mum, and the whole surface of the copper foil is etched to remove 25-90% of the original copper foil thickness so that the thickness variations of the frsidual copper foil are made to be within desired thickness + or -1.0mum and high density wiring is enabled in subsequent printed wiring manufacturing process.

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. A copper foil-clad circuit board such as a copper-clad sheet or a reinforced copper foil, the thickness of which is several -~2Q)a, and the thickness variation with respect to the desired thickness is ±1.0p or less. It is a manufacturing method.

[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 105cm thick, 770-135-118p1 by electrolytic method.
12JJ etc. are mass-produced, and copper foils such as 5uM and 97A formed on carriers such as aluminum foils are also made.Also, there are copper foils made by the rolling method, but due to the manufacturing method, the thinner the It is expensive, and foils with a thickness of 35 mm or less have not been put into practical use.

When such copper foil is used for laminated molding, its thickness is 1
If it is thinner than 8mm, it tends to wrinkle easily and the work of overlapping the copper foil with the insulator becomes extremely difficult, so it is rarely put into practical use. Copper foil formed on a carrier such as aluminum foil improves this point, but is expensive and requires a step to remove the carrier, such as aluminum foil, before forming printed wiring using copper foil. There was a problem.

In addition, in the printed wiring board processing process, there is a known method in which a copper foil-clad circuit board is pre-etched with an etching solution such as copper chloride or iron chloride, the copper foil is polished, and then used in the printed wiring board manufacturing process. However, it has not been possible to manufacture a thin copper-clad circuit board by increasing the amount of copper foil removed by preliminary etching or by etching a large area such as 1 m square.

[Means for solving problems]

As a result of intensive research into a method for manufacturing thin copper foil-clad circuit boards with high productivity that can be used as large-sized circuit boards, the present invention has developed a process for manufacturing copper foil on copper-clad circuit boards at a much slower speed than the conventional etching method. The inventors have discovered that a thin copper-clad circuit board with high thickness accuracy can be obtained by etching the entire surface and removing 25 to 90% of the original thickness of the copper foil, and have arrived at the present invention.

That is, in the present invention, a copper foil-clad circuit board manufactured from copper foil and an electrical insulator is etched using a copper etching solution of 0.01 to
The entire surface of the copper foil is etched at a rate of 0.3 mm/sec to remove 25-90% of the original copper foil thickness, and the thickness variation of the remaining copper foil is ±1. This is a method for manufacturing a thin copper foil-clad circuit board, characterized in that the thickness is within Op.

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 is not particularly limited, and various commercially available products used for electronic and electrical materials can be used, but the present invention When applying the manufacturing method, the nominal thickness is usually 18-
These include single-sided or double-sided copper-clad films and sheets using the above-described copper foil, fiber-reinforced insulating resin laminates, metal core laminates, and multilayer shield plates with a printed wiring network 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, etc.), fully aromatic polyamide, polyimide, semi-carbon, fluororesin, other heat-resistant engineering plastics, etc. Porous film using fibers, chopped, etc. Alternatively, it may be manufactured using a prepreg combined with a sheet-shaped reinforcing base material, or it may be manufactured by coating an iron, aluminum plate, etc. with an insulating adhesive or adhesive film. In addition, due to the pressure of lamination molding, the surface of the copper foil in ordinary copper-clad laminates partly reflects the unevenness of the reinforcing base material, and for example, in the case of a glass woven base material, it has a waviness of about 4 μM at about 40-pitch. However, it is also possible to use a material whose undulations have been precisely polished mechanically.

The copper etching solution of the present invention is an aqueous solution containing hydrogen peroxide/sulfuric acid, persulfate, copper chloride, iron chloride, etc. as a main ingredient, and has a lower concentration of etching components than etching solutions used for ordinary etching. The etching speed can be lowered by keeping the etching temperature low, by keeping the temperature low, by reducing the contact amount of the supplied etching liquid on the copper foil surface (spray pressure in the case of a spray method), or by appropriately combining these methods. Etching rates are used in the range of 1 to 0.3 p/sec, more preferably in the range of 0.03 to 0.20 p/sec. Etching speed is 0.
If the etching speed is faster than 3 un/sec, etching progresses due to a slight difference in etching processing time, which not only increases the tolerance from the desired thickness, but also tends to increase the variation in thickness depending on the location. The variation width is ±1. This is not preferable because it becomes difficult to keep it within Op. Also, the etching speed is 0.01J! XA/
If it is slower than seconds, etching takes a long time and is not practical.

In the above, methods for slowing down the etching speed include lowering 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, or to use a combination thereof.

A specific example of satisfying these conditions is when a hydrogen peroxide/sulfuric acid system is used as the etching solution, the concentration of hydrogen peroxide is 2 to 4 w/v%, and the concentration of sulfuric acid is 3 to 7 w/v.
%, a temperature of 25 to 50°C and a copper concentration of 30 to 60 g/l are suitable. This hydrogen peroxide/sulfuric acid based etching agent has
A method of adding additives such as a hydrogen peroxide stabilizer and a copper dissolution promoter is preferred. Such additives include monohydric alcohols such as methanol, ethanol, propatool, and butanol; dihydric alcohols such as ethylene glycol, propylene glycol, phthanediol, and pencundiol; and trihydric or higher alcohols such as glycerin and pentaerythritol. ; Glycol ethers such as polyethylene glycol; Nitrogen-containing organic cyclic compounds such as aminobenzoic acid, aminotetrazole, and phenylurea, and the like, and the amount is usually appropriately selected from the range of 0.1 to 5%.

In the case of a cupric chloride etching solution based on CuCl2, for example, CuCI2.2t1201.42! b and II
cI (20°8e゛) Q, 5gal dissolved to make 1gal aqueous solution (CuCI.・2820170g
#! , an aqueous solution containing HCI 19 w/v %) (7) An example is a method in which the temperature is 30 to 40° C. using an aqueous solution with a temperature of 1 degree or less.

Nf140H, NH4Cl, Cu, NaClO2,
In the case of a so-called "alkaline etching solution" which is an aqueous solution containing NH4NO3, etc., for example, N)1. OH3mol/j!
, NaCl0□10mol#! , NH4Cl 1
mol/l, NH4HCO31 mol/l,
N) 14NO31mol/I! The concentration of Cu in the aqueous solution is 10 lb/gal (74
, 89 g or less and a temperature of 30 to 45 DEG C., or a method of keeping the etching temperature at about 20 to 30 DEG C. as a normal solution concentration.

In the case of a persulfate etching solution based on (NH4)2S20+1, for example, (NH4)zstO@21t
An example is a method using an aqueous solution having a concentration of about 1/gal (240 g/(1) or less) at a temperature of 20 to 35°C.

In the case of etching liquid based on ferric chloride, 40°B
e' ferric chloride solution, 35% MCI 20-1vo
Using a 1% solution or a solution diluted with water, 20~
An example is a method performed at 35°C.

In the case of chromic acid/sulfuric acid etching solution, for example Cr0a
240g/j2, Na2SO440,5g/L+2
so4 (96%) 180g#! An example is a method using an aqueous solution with a concentration below a certain level.

However, for example, alkaline etching solutions have the disadvantage of poor stability, persulfate etching solutions have the disadvantage that etched copper tends to precipitate from the aqueous solution, and ferric chloride etching solutions have the disadvantage of varying dissolved copper concentration. In the present invention, hydrogen peroxide/sulfuric acid etching solution has the disadvantage that the etching rate changes greatly, and in the case of chromic acid/sulfuric acid etching solution, it corrodes the resin of the laminate.
A sulfuric acid-based etching solution is most preferred from the viewpoint of solution management and pollution.

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, methods such as the so-called alkaline etching mentioned above cannot be carried out vertically because they cause problems in the working environment, but in the case of hydrogen peroxide/sulfuric acid, both sides can be etched at the same time with the same spray pressure. This is one of the preferred methods because etching can be performed at the same speed and there is no need to correct the difference in etching speed between the upper and lower surfaces, unlike when the substrate is placed horizontally. Furthermore, in conventional etching machines, the jetting direction of the nozzle is normally set as perpendicular to the surface of the laminate plate that moves at a constant speed, but in the case of the present invention, the etching direction is perpendicular to the surface of the laminate plate, which moves at a constant speed. It is sufficient if the spray is uniformly applied, and it can also be used at an angle of about 30° to 50°.

The etching rate was reduced to 0.0 by the method detailed above.
The entire surface of the copper foil is etched at a rate of 0.05~0.3p to reduce the thickness variation of the remaining copper foil to ±1 of the predetermined thickness.

This enables the formation of high-density wiring in the subsequent printed wiring manufacturing process. For example, thickness 9AEm~3
The nominal thickness of thin copper clad plate of about P is ±18-(1/202)
By etching a copper-clad laminate using copper foil, it can be easily manufactured with high thickness accuracy, and the adhesive strength of the original copper-clad laminate can be utilized as is. Further, a copper clad board having a thickness of approximately 12 ρ to 20 m is similarly manufactured by etching a copper clad laminate using copper foil having a nominal thickness of ±35E11 (10Z).

After cleaning the copper foil surface of the laminate treated with the etching agent described above, it is dried as appropriate, and a rust preventive agent or a peelable resin coating 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., and is selected appropriately taking into consideration the stabilizer and other components of the copper etching solution used, but usually It is preferable to carry out neutralization - acid cleaning -> (corrosion prevention or protective film coating).

After drying appropriately, the copper foil surface is protected with the rust preventive agent or peelable resin of the present invention. Examples of the rust preventive include known copper rust preventives, azole compounds such as benzotriazole, and those in which a surfactant or the like is appropriately used in combination. Also, examples of removable resins include polyethylene, polypropylene, ethylene-propylene resin,
Ethylene-vinyl acetate resin, vinylidene chloride, polyacrylate copolymer, 1,2-polybutadiene resin, polyester resin, other thermoplastic resin films and photoresist films; paraffin wax, polyethylene wax, rosin, low molecular weight polystyrene general-purpose solvent-soluble resins such as; examples include photoresist resin liquid, etc., and may be directly pressure-bonded to the cleaned copper foil surface, or further pressure-bonded to the rust-preventing surface as described above. Cover the surface.

〔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 A glass cloth-based epoxy resin laminate measuring 1020 x 1020 mm and having a thickness of 1.6 mm and coated with nominal IBp copper foil (Nikko Gould Co., Ltd., TC foil) on both sides was etched with hydrogen peroxide using a horizontal spray etching machine. / Sulfuric acid etching solution (manufactured by Mitsubishi Gas Chemical ■, FES-6000, LOz□7.78
Etching was carried out under the following conditions using a 3-fold dilution of H2SO1.11.7w/v%).

After applying one layer at a time, neutralize, wash with acid, and wash with water, apply a water-soluble rust preventive agent (
For example, use C, B, Bright (manufactured by Mitsubishi Gas Chemical ■), Colomin CB (manufactured by Kao Atlas 0 Kiku, etc.) to prevent rust, and apply an eddy current film thickness meter (manufactured by Densoku Kogyo ■, Goomes). By measuring the thickness of the copper foil with an eddy current film thickness meter, model O3-1), one continuous thin copper clad plate listed in Table 1 was measured.
0 sheets were manufactured.

Comparative Example 1 In Example 1, FES-600 was used as the etching solution.
The etching conditions were the same except that a stock solution of No. 0 was used and the etching conditions were as follows. The results are shown in Table 1.

Comparative Example 2 Ten double-sided boards similar to those in the example were fabricated using single-sided adhesive treated electrolytic copper foil with a nominal thickness of 9 mm, 40 kg/cnf, 170°C2
Manufactured under laminated molding conditions for hours. It was extremely difficult to handle 9p copper foil without wrinkles, and wrinkles occurred in 30% of the laminated molded products. The measurement results of the obtained double-sided board are shown in Table 2.

Comparative Example 3 A double-sided board was manufactured in the same manner as in Comparative Example 2 using a 40-thick aluminum foil plated with copper of a nominal thickness of 9 Atm and a foil whose plated surface was roughened, and then the aluminum foil was removed by etching. . The measurement results of the double-sided board obtained are
Shown in the table.

・Etching AN Ll, t), 3/SeC 2nd
Table Example 2 A 400 x 300 mm double-sided copper-clad laminate similar to Example 1 was etched using a horizontal spray etching machine and etched with ferric chloride enochinda solution (FeC135,8 (1,3b% HCI).
1.211 water 3. Temperature: 25℃, etching rate: 0.25/SeC, spray pressure (upper surface 1
．． 0kg/cnf, bottom surface 0.8 kg/ctd
, ) in the same manner except that the average thickness of the copper foil was 9.0 At.
B. A thin copper clad plate having a thickness range of 8.1 to 9.9 mm was obtained.

[Operation and effects of the invention]

As is clear from the detailed description of the invention, Examples, and Comparative Examples, the manufacturing method of the present invention enables thin copper clad copper foils to have thickness accuracy equivalent to or higher than that using conventional aluminum clad copper foils. It is understood that the laminate is easily manufactured and has excellent peel strength of copper foil.

As a result, thin copper-clad laminates, which could conventionally only be manufactured using methods using copper foils such as 5ρ and 9μ formed on carriers such as expensive aluminum foils, can be manufactured accurately, inexpensively, and easily. It is understood that this makes it possible, and its industrial significance is extremely large.

Patent applicant: Mitsubishi Gas Chemical Co., Ltd.

Claims (1)

[Claims] A copper foil-clad circuit board made of copper foil and an electrical insulator is etched over the entire surface of the copper foil at a rate of 0.01 to 0.3 μm/sec using a copper etching solution to restore the original thickness of the copper foil. Sano 2
A method for manufacturing a thin copper foil-clad circuit board, characterized in that 5 to 90% of the copper foil is removed and the variation in thickness of the remaining copper foil is within ±1.0 μm with respect to a desired thickness.