JPH0325995A - Manufacture of thin copper foil-plated circuit board - Google Patents

Abstract

PURPOSE:To easily manufacture a thin copper-plated plate having an extremely high thickness accuracy by removing 25-90% of original thickness by etching the whole copper foil surface of a substrate at a very slow speed, and controlling an etching temperature in a specific range by using cupric chloride/aqueous hydrochloric acid solution of specific composition ratio as copper etchant. CONSTITUTION:A thin copper-plated circuit board is manufactured by using a glass cloth base material epoxy laminated plate in which copper foils are plated on both side faces. The board is etched on the whole surface at a speed of 0.01-0.3mum/sec with copper etchant by using a horizontal etching machine. The etchant contains 0.25-3mol/l of cupric chloride, aqueous solution of 1-4mol/l hydrochloric acid, is controlled within a predetermined concentration + or -0.3mol/l, and the etching temperature is controlled at a predetermined temperature + or -5 deg.C in a range of 25-55 deg.C. An irregularity in the thickness of remaining copper foil to a desired thickness falls within + or -1.0mum. Then, for example, it is sequentially dipped in aqueous solutions of HCl, H2SO4 and Na2CO3, then dipped in aqueous solution of benzotriazole, and then dried with hot blast.

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 and reinforced copper foil, with an average thickness of several Am to 20 kon, and a thickness variation of ±1.0 or less with respect to the desired thickness. This is a method for manufacturing circuit boards.

[Conventional technology and its problems]

Copper foil-clad circuit boards are manufactured by stacking copper foil and insulators, usually by laminating, etc., and the copper foil used has a thickness of ■05-, 7 (] uM, 35-1, 18 by electrolytic method).
Copper foils such as 5p1 9-, which are formed on carriers such as aluminum foils, are also produced.

In addition, there is copper foil made by rolling, but due to the manufacturing method, the thinner the foil, the more expensive it becomes, and foils with a thickness of less than 35 mm are currently in the trial production stage and have not been commercially common.

When such a copper foil is used in a laminated shape, if the thickness is thin, it tends to wrinkle, and the work of overlapping the copper foil with an insulator becomes extremely difficult, so it is hardly put to practical use. In addition, copper foil formed on a carrier such as aluminum foil improves this point, but is expensive, and furthermore, it is necessary to remove the carrier such as aluminum foil before forming printed wiring using copper foil. The problem was that it required a process.

Another 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, polish the copper foil, and then use it in the printed wiring board manufacturing process. However, if the amount of copper foil removed by preliminary etching is increased to several tens or more, or if 500x5
When manufacturing a thin copper-clad circuit board by etching a large area such as 0.00 mm square, the thickness of the remaining copper foil will vary greatly, making it impossible to manufacture a commercially viable thin copper-clad circuit board. There wasn't.

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 a copper foil having a thickness of 81 or more to a thickness of 121 or less.

However, in the case of the method shown in Example 1 of Kaisho,
Average thickness of 340+nm x 340 mm square copper foil 1
81 is cupric chloride (1.0mo!/12)
There is a description that a thin copper foil with an average thickness of 10 μm was obtained by etching the entire surface with an etching solution consisting of /hydrochloric acid (6.6 mol/C), but as described in Comparative Example 1 of the present invention, a commercially available spray method was used. In etching, the etching rate is approximately 0.
The conditions were high speeds of 5 instants/second, and a 1 second etching time difference resulted in an average thickness of 0.5 seconds. This appears as a difference of 5 times, and the difference in effective contact time of the etching solution depending on the location is added.

As a result, when etching only five copper-clad laminates, the variation in average thickness is ±3.5- and the variation in desired thickness is ±4.8-, 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 amount of production increases. Furthermore, the other methods described in Kaisho, 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 has been etched with copper foil using an ordinary etching solution is immediately used in a circuit form as described in the example of this Japanese Patent Application Laid-Open No. The surface of the remaining copper foil on this thin copper-clad circuit board was extremely active and would rust in a short period of time if left in the air.

[Means to solve the problem]

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 thickness is reduced by etching the entire surface to remove 25 to 90% of the original thickness of the copper foil, and using a cupric chloride/hydrochloric acid aqueous solution with a specific composition ratio as the copper etching solution. The inventors have discovered that a thin copper-clad circuit board with high precision can be obtained, and have arrived at the present invention.

That is, the present invention etches a copper foil-clad circuit board made of copper foil and an electrical insulator using a copper etching solution of cupric chloride/hydrochloric acid aqueous solution at a speed of 0.01 to 0.3 1/sec. The entire surface of the copper foil is etched to a thickness of 25 to 9 mm, which is the thickness of the original copper foil.
A method for producing a thin copper foil-clad circuit board in which the thickness of the remaining copper foil has a variation within ±1.0 with respect to the desired thickness by removing 0% of copper chloride, the copper etching solution comprising cupric chloride 0%. .25~
3mol/j! , an aqueous solution containing 1 to 4 mol/β of hydrochloric acid, and the concentration of hydrochloric acid is at least ±0.0% of the predetermined concentration. 3mol/j
The etching temperature is controlled within 25 to 55℃.
This is a method for manufacturing a thin copper foil-clad circuit board characterized by controlling the temperature within a predetermined temperature range of ±5°C, and after etching the entire surface of the copper foil, immediately etching the copper foil with a water-soluble rust preventive. This is a method for manufacturing a thin copper foil-clad circuit board, which is characterized by treating the surface of the remaining copper foil.

First, regarding the Etsudinda liquid used in the production method of the present invention,
The explanation will be based on the attached drawings.

Figures 1 and 2 show copper-clad laminates being etched at 50°C and 30°C, respectively, using a spray etching device with a cupric chloride/hydrochloric acid aqueous solution at a spray density of 1/2 and a spray pressure of 1 k.
Etching was carried out at a rate of g/crA, and the etching rate was calculated from the weight loss, and this is shown as cupric chloride concentration vs. etching rate at a constant hydrochloric acid concentration.

From the figure, it can be seen that under conditions of normal hydrochloric acid concentration at both temperatures of 50°C and 30°C, that is, the hydrochloric acid concentration is 5 mol, which is higher than 4 mol, #2, the etching rate largely depends on the concentration of cupric chloride. Conversely, if the hydrochloric acid concentration is 4
mol#! Below, even if the concentration of cupric chloride changes greatly, the etching rate changes only slightly.
Special'rt3mol#! It is almost horizontal. Than this,
It is understood that when the hydrochloric acid concentration is 4 mol/j2 or less, the etching rate hardly changes with respect to a change in the cupric chloride concentration, and when it is 3 mol/l, it does not change substantially. Also, when the hydrochloric acid concentration is 4 mol # or less, ■: Hydrochloric acid It is understood that the change in etching rate with respect to concentration change is also small.
℃) and Figure 2 (30℃), it was found that the hydrochloric acid concentration was 4 mol#! In the following, ■: Do you understand that the change in etching rate with respect to temperature is also extremely small? .

In copper etching, cupric chloride (CuC1■) oxidizes the surface of the copper foil and changes to cuprous chloride (CuC1), and the surface of the oxidized copper foil reacts with hydrochloric acid (HCI) to form cuprous chloride. (C
This is an exothermic reaction in which uC1) is eluted into the etching solution and removed from the surface of the copper foil.

In order to achieve uniform etching over the entire surface, excessive progress of local etching must be avoided. However, the etching agent is consumed along with the etching reaction.

Therefore, in order to avoid excessive progress of local etching, it is necessary that the etching rate does not decrease significantly even if the chemical is consumed. On the other hand, the above conditions (1) and (2) satisfy this condition. In addition, ■ indicates that in order to control the etching rate, it is essentially only necessary to control the hydrochloric acid concentration; measuring the cupric chloride concentration is complicated and time-consuming, and it is not practical to use this as a control factor. Since it is technically difficult, it has extremely important significance for industrial implementation.

Furthermore, etching is an exothermic reaction, and changes in etching temperature naturally occur, so new control equipment is required to keep the etching temperature more strictly constant. On the other hand, from the above point (2), it can be understood that this control is also extremely simple and easy, and it is of great practical significance.

Next, the structure of the present invention will be explained.

The copper foil-clad circuit board manufactured from the copper foil and electrical insulator of the present invention has an average thickness of 12 μm or more and a thickness variation of ±1. There is no particular limitation as long as it uses copper foil within our range, and any of various commercially available products used for electronic and electrical materials can be used. In particular, in the case of thin copper foil-clad laminates with a thickness of 12-1 or less, the nominal thickness is l.
It is preferable to use a copper foil laminate of 2 to 18 inches. Examples of copper-clad laminates include single-sided or double-sided copper-clad films, sheets, 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,
Porous films or sheets made of fibers, chops, etc. made of one or more types of heat-resistant engineering plastics, such as boron nitride, etc.), fully aromatic polyamides, polyimides, semi-carbons, fluororesins, and other heat-resistant engineering plastics. These include those manufactured using a prepreg formed by combining a reinforcing base material, or those manufactured by coating an iron, aluminum plate, etc. with an insulating adhesive or adhesive film. In addition, with ordinary copper-clad laminates, due to the pressure of lamination, the surface of the copper foil partially reflects the unevenness of the reinforcing base material.
For example, in the case of a glass woven fabric base material, the pitch is about 0.4 mm, and the
Although it has undulations of about 41 degrees, it is also possible to use a material in which the undulations are mechanically replaced with fine irregularities or the like or removed. In addition, as a method for producing copper-clad laminates or sheets using thin copper foil with a thickness of 12 to 16, a layer of aluminum foil with a coefficient of thermal expansion of 40 to 100 A method of laminating or shaping sheets by inserting sheets of approximately 100 mm is preferable.

The copper etching solution using cupric chloride/hydrochloric acid aqueous solution of the present invention is as explained in the drawings above, and contains cupric chloride and hydrochloric acid as essential components, and optionally etches the etched copper foil surface. It is an aqueous solution containing auxiliary agents for controlling the condition, and the concentration of cupric chloride (CIC12 2H20) is usually 0.25 to 3 mol/l, preferably 0.
25-2 mol/R, the concentration of hydrochloric acid (HCI) is 1.
0-4mo 1/(1, preferably 1-3.6mo
A range of I/ (1) is used to perform highly accurate whole surface etching within a practical range. Alcohols as auxiliary agents include monohydric alcohols such as methanol, ethanol, propanol, and butanol; ethylene glycol, propylene glycol, and butane; Examples include dihydric alcohols such as diol and pentanediol; trihydric or higher alcohols such as glycerin and pentaerythritol; and other additives such as glycol ethers such as polyethylene glycol; aminobenzoic acid, aminotetrazole, Examples include nitrogen-containing organic cyclic compounds such as phenylurea.

In addition, copper dissolves into the etching solution during etching, but the concentration of this dissolved copper is 5 to 65 g.
(0.08 to 1.O mold), preferably 50
It is preferable to adjust it within the range of g/l or less.

Etching is performed using the above-mentioned cupric chloride/hydrochloric acid aqueous solution, but this etching solution significantly reduces the etching speed compared to hard etching performed in normal pattern forming, and also has a high etching agent concentration. It has reduced dependence on temperature. The etching rate is in the range of 0.01-0.31/sec, more preferably 0.01/sec.
A range of 0.03 to 0.2 hv+/sec is used. When the etching rate is faster than 0.3 cm/sec, the difference in etching amount becomes large due to differences in etching processing time, concentration, temperature, etc., which are smaller than the controllable range of etching conditions. This appears as variations depending on the location of a single copper clad plate, and variations in the average thickness when a large number of plates are processed, and the thickness range is ±1. D.I. It is undesirable because it becomes difficult to manufacture a thin copper-clad circuit board with high precision within lTa, which creates an extra burden on quality control, etc., and increases the number of defective products. Also, the etching rate is 0. Obo
If the etching speed is slower than n/second, etching takes a long time and is not practical.

As the etching method in the manufacturing method of the present invention, spray etching is usually suitable, and is performed horizontally or vertically. In particular, when etching both sides of a large-area copper clad board at the same time, it is preferable to set it vertically. Further, it is preferable that the etching solution adhering to the surface of the copper-clad laminate is quickly removed after etching is completed.

In order to obtain a copper foil with a predetermined thickness by etching, a method is used in which the etching rate under predetermined etching conditions is measured and the etching time is set. for example,
Using a double-sided copper clad board with copper foil of the same thickness on both sides, in order to make both sides horizontally the same thickness at the same time, spray pressure and spray if necessary so that the etching speed on both the top and bottom sides is the same. This method is based on a method of controlling the number, etc., making the etching speed uniform, and etching for a predetermined period of time. In addition, conventional horizontal etching machines
A method is used in which the jetting direction of the nozzle is made as perpendicular as possible to the copper foil surface of the laminate, which moves at a constant speed of less than 1 minute. The spray nozzle should be sprayed at an angle of 30°.
It can also be used at an angle of about 50 degrees.

The copper foil surface of the laminate treated with the cupric chloride/hydrochloric acid aqueous solution etching agent described above 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., and considers the use of stabilizers and other additives in the copper etching solution using the cupric chloride/hydrochloric acid aqueous solution. After pickling, water washing, or hot water washing, neutralization treatment at 20 to 50°C with an aqueous solution of 1 to 5 wt% of sodium carbonate, the rust preventive agent may be a known copper rust preventive agent, For example, an azole compound such as benzo} IJ azole at 0.01
It is suitable to carry out the immersion treatment at 20 to 50° C. in an aqueous solution containing 1 wt % and appropriately combined with a surfactant or the like.

In addition, after the rust prevention treatment, heat-removable resin such as polyethylene, polypropylene, ethylene-brobylene resin, ethylene-vinyl acetate resin, vinylidene chloride, polyacrylate copolymer, 1,2-polybutadiene resin, polyester resin, etc. Plastic resin films and photoresist films; general-purpose solvent-soluble resins such as paraffin wax, polyethylene wax, rosin, and low molecular weight polystyrene; and photoresist resin liquids are bonded to copper. It is also preferable to coat the foil surface.

As described above, the cupric chloride/hydrochloric acid aqueous solution of the present invention is characterized by significantly lowering the hydrochloric acid concentration compared to conventional solutions, and mainly controlling the hydrochloric acid concentration.

This point will be explained with reference to the attached drawings.

〔Example〕

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

Example 1 700 x 1020 mm, board thickness 1.6 mm, average copper foil thickness 9μ using 10 glass cloth base epoxy resin laminates with copper foil on both sides coated with low profile treated copper foil of average thickness 15mm. A thin copper-clad circuit board was manufactured.

The copper foil thickness range of the double-sided copper clad board used was 15.0μ on average,
Maximum 15.5-, minimum 14.5-, variation ±0.
! 5 tcm, and the surface unevenness of the copper foil measured by a surface unevenness meter was 3.6 to 4.3.

A horizontal etching machine was used, and the following cupric chloride etching solution and etching conditions were used as a copper etching solution.

? and 0.01-0.5% aqueous solution of I-ICI, 3
After sequentially immersing in a 11% S04 aqueous solution and a 5% Na2COa aqueous solution for 30 seconds each at room temperature, immersing it in a 0.3% concentration penzotriazole aqueous solution at 40 ° C. for 30 seconds,
It was dried with hot air at 100°C for 30 seconds.

For all of the obtained thin copper clad boards, 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.

As a result, the copper foil thickness averaged 8.9-, maximum 9.4-, minimum 8.6-, and the variation with respect to the average thickness was ±0.5 bar.
The variation with respect to the desired thickness was ±0.41.

Note that when the thin copper clad plate was maintained at 25° C. and 60% RH, spotty rust appeared after 24 hours, and the shelf life was somewhat unsatisfactory.

Comparative Example 1 A 91-thin copper-clad circuit board was prepared by etching the same copper-clad laminate as in Example 1 using the following ordinary cupric chloride etching solution.

First, using this etching solution, the etching rate was measured using a 701 copper foil clad plate under the following conditions.

As a result, it was confirmed that the etching rate was 0.5-/sec. 15- Using a copper foil clad plate, 6. The etching time required for OJi etching 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 were possible with this etching machine:
The spray nozzles for 1.5 m of the effective etching chamber length of 2.0 m are blocked, and the conveyor speed is 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.
When measured in the same manner as above, the average was 8.7μ, the maximum was ]. 0.
6-, minimum 5.2- and variation in average thickness is ±3
．． 5-, the variation with respect to the desired thickness was ±4.8 μs, and 48% of the measurement points were in the range of 8.5 to 9.5 mm thick of the copper foil. Moreover, the surface unevenness was 3.8 to 4.5 μs.

Furthermore, when the thin copper clad plate was held at 25° C. and 60% Rl+, spotty rust appeared after 3 hours.

[Operation and effects of the invention]

As is clear from the detailed description of the invention, examples, and comparative examples. With conventional cupric chloride/hydrochloric acid aqueous solutions, etc., the variation in copper foil thickness is so large that it is comparable to the amount of etching, whereas the method of the present invention has extremely high thickness accuracy and It is understood that a thin copper clad plate comparable to the ultra-thin copper foil of 2008 can be easily manufactured.

As a result, thin copper-clad laminates, which could previously only be fabricated using methods such as using 5μ or 91 copper foil formed on carriers such as expensive aluminum foil, electroless plating or vapor deposition, have now been made. It can be easily manufactured with high precision and at low cost, and its industrial significance is extremely large.

[Brief explanation of drawings]

Figures 1 and 2 show the chloride content when a copper clad laminate was etched using a cupric chloride/hydrochloric acid aqueous solution using a spray etching device at 50°C and 30°C, respectively, and the hydrochloric acid concentration was kept constant. It shows the relationship between cupric concentration vs. etching rate.

Claims (1)

[Claims] 1. A copper foil-clad circuit board made of copper foil and an electrical insulator is etched at a speed of 0.01 to 0.3 μm/sec using a copper etching solution of cupric chloride/hydrochloric acid aqueous solution. Etching the entire surface of the copper foil to remove 25-90% of the original copper foil thickness,
The variation in the thickness of the remaining copper foil is ±1.0 with respect to the desired thickness.
A method for manufacturing a thin copper foil-clad circuit board with a thickness within μm, wherein the copper etching solution contains cupric chloride 0.25 to 3 mol/l,
An aqueous solution of hydrochloric acid of 1 to 4 mol/l, at least the hydrochloric acid concentration is controlled within ±0.3 mol/l of the predetermined concentration, and the etching temperature is within the range of 25 to 55°C at the predetermined temperature ±5°C.
A method for producing a thin copper foil-clad circuit board, characterized in that the production of a thin copper foil-clad circuit board is controlled within 2. The method for manufacturing a thin copper foil-clad circuit board according to claim 1, wherein the surface of the remaining copper foil is treated with a water-soluble rust preventive agent immediately after etching the entire surface of the copper foil.