JPH10190226A - Manufacture of multilayer board - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make it hard to reduce the current capable of being passed through a copper circuit, by controlling within a specified time for which a board for inner layer having the copper circuit on its surface is transported in the air when the board is dipped in cleaning liquid after the board is treated in treatment liquid containing hydrochloric acid and cupric chloride at a specified compounding ratio to subject the board to an acid-proof surface-roughening process. SOLUTION: A board for inner layer having a copper circuit on its surface is pretreated in pre-roughening treatment liquid containing hydrochloric acid and cupric chloride. The surface-roughening pre-treatment liquid is a solution containing 120-150g/L of hydrochloric acid and 10-20g/L of cupric chloride. If the compounding ration is cut of this range, it is difficult to uniformly perform the an acid-proof surface- roughening treatment. After the board for inner layer is taken out, the board is transported in the air, and then dipped in cleaning liquid. The time for which the board is transported in the air after the pre-pretreatment with the liquid before dipping in the cleaning liquid, is controlled to 70 seconds or below. If the time exceeds 70 seconds, the amount of current capable of being passed through the copper circuit formed on the surface of the board for inner layer is reduced, and degradation in electrical reliability may result.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a multilayer board used for electric and electronic equipment.

[0002]

2. Description of the Related Art Conventionally, a multilayer board used for electric equipment or the like is manufactured by oxidizing a copper circuit formed on the surface of an inner layer substrate to increase the bonding strength, and then applying the oxidized treatment to at least one of the inner layer substrates. It is manufactured by stacking prepregs, further arranging and laminating a metal foil on the outermost layer of the prepregs, and then heating and pressing. The oxidation treatment is a chemical oxidation treatment generally called a blackening treatment, which is performed on the glossy surface of the copper circuit to form fine irregularities on the surface of the copper circuit and to blacken the surface of the copper circuit, thereby forming copper. This is a process for improving the adhesion between the circuit and the prepreg.

[0003] With the recent increase in the density of multilayer boards, the oxidation treatment applied to the copper circuit when processing the multilayer board is melted by acid, causing a problem of discoloration called haloing. As a countermeasure against the occurrence of the haloing, it has been studied to perform an acid roughening treatment on the copper circuit formed on the inner layer substrate. As a method of the acid surface-roughening treatment, of the cuprous oxide and cupric oxide formed on the surface of the copper circuit by the oxidation treatment, cupric oxide, which is easily reduced, is eluted by reduction to reduce the surface. Treatment of copper oxide surface with a layer of roughened copper oxide with excellent acid resistance, or treatment of the copper circuit by treating the glossy surface of the copper circuit directly with an acidic aqueous solution containing formic acid, copper ions and a chelating agent of copper ions. And the like are performed to roughen the surface.

However, the color tone of the acid-surface-roughening treatment is thinner and closer to brown as compared with the above-mentioned oxidation treatment (blackening treatment), and the difference in the position of the surface of the substrate for the inner layer and the large color tone between the substrates for the inner layer. There is a problem that a difference may occur.

[0005] Therefore, before performing the acid-resistant surface-roughening treatment, the surface is pretreated with a surface-roughening pretreatment liquid that is an aqueous solution containing hydrochloric acid and cupric chloride so that the treatment is performed uniformly. Rinsing with water, and then performing an acid-resistant surface roughening treatment. Note that this pre-roughening solution was prepared by adding hydrochloric acid to 120
~ 150 grams / liter (hereinafter referred to as g / L),
When cupric chloride is contained in an amount of 10 to 20 g / L, the color tone after the acid-surface-roughening treatment is good, so that it is generally used.

As a method of the pre-treatment or the acid surface-roughening treatment, the inner layer substrate is taken out of the processing liquid and then the processing liquid is contained in order to prevent the liquid in that step from being carried into the subsequent steps. In general, a method of stopping in the air above a tank to drop the liquid on the surface of the inner layer substrate to some extent, then transporting the liquid in the air, and then transporting the liquid to the next step is generally performed.

With the recent increase in the density of multilayer boards, the width of the copper circuit formed on the surface of the inner layer substrate tends to be reduced.
After pretreating the inner layer substrate having the thin copper circuit with the roughening pretreatment liquid containing hydrochloric acid and cupric chloride, the substrate is transported in the air, then washed with water, and then subjected to an acid-resistant surface roughening treatment. When a multilayer board is manufactured in such a manner, there is a problem that the amount of current that can flow through the copper circuit formed in the inner layer is reduced, and the electrical reliability may be reduced. Therefore, there is a demand for a method of manufacturing a multilayer board in which the amount of current that can be passed through a copper circuit formed on the surface of the inner layer substrate is unlikely to decrease.

[0008]

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and an object of the present invention is to provide a substrate for an inner layer having a copper circuit on its surface by using hydrochloric acid and secondary chloride. After pre-treatment with a surface roughening pretreatment liquid containing copper, an acid surface-roughening treatment is performed, and then a prepreg and a metal foil are laminated on at least one of the inner layer substrates, and then heated and pressed to form a multilayer. An object of the present invention is to provide a method for manufacturing a board, which is a method for manufacturing a multilayer board in which the amount of current that can be passed through a copper circuit formed on the surface of an inner layer substrate is less likely to decrease.

[0009]

According to a first aspect of the present invention, there is provided a method for manufacturing a multilayer board, comprising the steps of: preparing a substrate for an inner layer having a copper circuit on its surface with a roughening pretreatment liquid containing hydrochloric acid and cupric chloride; After pre-treatment, transported in the air, then immersed in the cleaning solution,
After performing acid-resistant surface-roughening treatment, and then laminating a prepreg on at least one surface of the inner layer substrate, further laminating a metal foil on the outermost layer of the laminate, and then heating and pressing to form a multilayer board. The method for producing a multilayer board, wherein the roughening pretreatment liquid contains hydrochloric acid at 120 to 150 g / L and cupric chloride at 10 to 20 g / L, It is characterized in that the time of transport in the air while immersing in the cleaning liquid after the pretreatment is 70 seconds or less.

According to a second aspect of the present invention, in the method for manufacturing a multilayer board according to the first aspect, the temperature of the air for transporting the inner layer substrate is 0 to 40 ° C. Features.

[0011] During the transfer of the inner layer substrate in the air,
The roughening pretreatment liquid attached to and taken out of the inner layer substrate surface flows on the inner layer substrate surface due to gravity or transport force. At this time, the roughening pretreatment liquid takes in oxygen in the air and is particularly activated, and the copper circuit in a portion where the roughening pretreatment liquid flows a lot is excessively etched, and the cross-sectional area partially decreases. It is considered that the amount of current that can flow through the copper circuit may decrease. However, according to the present invention, it is considered that this etching does not proceed so much, and the amount of current that can be passed through the copper circuit formed on the surface of the substrate does not easily decrease.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION The method for manufacturing a multilayer board according to the present invention is characterized in that a substrate for an inner layer having a copper circuit on its surface is pretreated with a roughening pretreatment liquid containing hydrochloric acid and cupric chloride and then air-treated. After being immersed in a cleaning solution, the surface is subjected to an acid surface-roughening treatment, then a prepreg is laminated on at least one of the inner layer substrates, and a metal foil is further laminated on the outermost layer of the laminate, and then heated. It is manufactured by pressing.

The substrate for the inner layer used in the present invention is not particularly limited as long as it has a copper circuit on its surface. For example, epoxy resin, phenol resin, polyimide resin, unsaturated polyester resin, Thermosetting resins such as polyphenylene ether resin, or a sheet in which a copper foil is stretched on one or both sides of a sheet obtained by blending an inorganic filler or the like with these thermosetting resins, or inorganic fibers or polyester such as glass A polyamide, a cloth of organic fibers such as cotton, a substrate such as paper, and the like are bonded with the above-mentioned thermosetting resin or the like, and the copper foil is etched using a plate or the like having a copper foil on one or both sides. And a copper circuit formed on the surface of the above-mentioned plate not covered with copper foil by copper plating. The substrate for the inner layer may have a copper circuit inside, and may have a through hole in which a metal layer is formed on the wall surface or a through hole in which a conductor such as silver paste is filled. Is also good.

The roughening pretreatment liquid is prepared by adding hydrochloric acid to 120-150.
It is important that the aqueous solution contains g / L and 10 to 20 g / L of cupric chloride. If the thickness is outside this range, it is difficult to uniformly perform the surface roughening treatment, and a difference in the position of the surface of the inner layer substrate or a large difference in color tone between the inner layer substrates may occur. The roughening pretreatment liquid may contain a dissolution promoter for hydrogen peroxide or copper.

The temperature and the time of the treatment using the above-mentioned roughening pretreatment liquid are appropriately determined according to the concentration of the roughening pretreatment liquid and the like, and the temperature is preferably 20 to 40 ° C. In addition, as the method of treatment, when the method is performed by immersing the inner layer substrate in the treatment liquid, the variation in the treatment such as the in-plane treatment of the inner layer substrate is reduced, and the color tone after the acid roughening treatment becomes uniform, which is preferable. .

Before the treatment using the pre-roughening solution, the surface of the copper circuit of the substrate for the inner layer may be mechanically polished and washed as necessary before the treatment.

Next, after taking out the inner layer substrate from the roughening pretreatment liquid, it is transported in the air and then immersed in the cleaning liquid. It is important that the time of transport in the air during immersion in the cleaning liquid after pre-treatment with this surface roughening pre-treatment liquid is 70 seconds or less. If the time exceeds 70 seconds, the amount of current that can flow through the copper circuit formed on the surface of the inner layer substrate decreases, and the electrical reliability may decrease.

This is because, when the roughening pretreatment liquid adhered to the surface of the inner layer substrate and taken out of the inner layer substrate flows down or flows on the inner layer substrate surface by the force of transportation, it takes in oxygen in the air and is particularly activated. The copper circuit in the portion where the roughening pretreatment liquid has flowed a lot may be excessively etched, and the cross-sectional area is partially reduced, so that the amount of current that can be passed through the copper circuit is considered to decrease. However, if the time for carrying in air during immersion in the cleaning liquid after pre-treatment with the roughening pre-treatment liquid is 70 seconds or less, this etching does not proceed so much, and the copper circuit formed on the surface of the substrate does not proceed. It is considered that the amount of current that can be supplied to the power supply hardly decreases.

It should be noted that the "time for transporting in the air" of the present invention.
Means, from the moment the inner layer substrate comes out of the roughening pretreatment liquid,
Represents the entire time until the moment when the inner layer substrate comes into contact with the next liquid, for example, after removing the inner layer substrate from the tank containing the roughening pretreatment liquid, stop in the air above that tank In the case of a method in which the liquid on the surface of the substrate is dropped to some extent and then conveyed while being exposed to the air, the substrate is dipped in the liquid in the next step.

The temperature of the air (atmosphere) in the portion where the substrate for the inner layer is transferred is preferably 0 to 40 ° C. 4
If the temperature exceeds 0 ° C., the amount of current that can flow through the copper circuit formed on the surface of the inner layer substrate decreases, and the electrical reliability may decrease. If the temperature is lower than 0 ° C., the aqueous solution to be used may freeze, which is not practical.

The conditions for immersion in the cleaning liquid are not particularly limited, and are appropriately set to such an extent that the pretreatment liquid for roughening can be cleaned. The washing liquid is not particularly limited, but water is economically preferable.

Next, an acid roughening treatment is performed. As the method of this oxidation treatment, a general method can be applied.For example, the surface of a copper circuit is treated with a liquid containing an oxidizing agent such as sodium chlorite and potassium persulfate and an alkali such as sodium hydroxide to form a copper oxide. After that, for example, a method of dipping in an aqueous solution of an organic reducing agent such as dimethylamine borane, a method of dipping in a solution containing a chelating agent of a weak acid and copper, or a method of coating zinc powder and dipping in sulfuric acid A method of forming an acid-resistant treatment film by reducing copper oxide by a method of generating and treating hydrogen, or treating a glossy surface of a copper circuit directly with an acidic aqueous solution containing formic acid, copper ions and a chelating agent of copper ions. Thus, a method of forming an acid-resistant film can be given.

Next, the substrate is washed with water to wash the treatment liquid for the acid-resistant surface roughening treatment. Note that, before the acid-resistant surface-roughening treatment, the surface may be washed with an acid such as hydrochloric acid, washed with water, and then subjected to the acid-resistant surface-roughening treatment. After the acid surface-roughening treatment, the substrate may be immersed in a solution of a silane coupling agent or the like, or may be heated and dried to remove moisture absorbed by the acid surface-roughening treatment or the like.

[0024] A prepreg is laminated on at least one surface of the inner layer substrate subjected to the acid roughening treatment by the above method,
Furthermore, after laminating a metal foil on the outermost layer of the laminate, the laminate is manufactured by heating and pressing. The heating and pressurizing is performed under the condition that the thermosetting resin of the used prepreg is cured as appropriate.

The prepreg used in the present invention is obtained by impregnating a base material with a thermosetting resin and, if necessary, drying it.
As the base material used for the prepreg, inorganic fibers such as glass, organic fibers such as polyester, polyamide, polyacryl, and polyimide, and natural fiber cloth and paper such as cotton can be used. In addition, inorganic fibers such as glass fibers are preferable because they have excellent heat resistance and moisture resistance.

As the thermosetting resin used for the prepreg, epoxy resin, phenol resin,
Polyimide resin type, unsaturated polyester resin type, polyphenylene ether resin type alone, modified products, like mixtures, thermosetting resins can be used in general, silica, calcium carbonate, aluminum hydroxide, if necessary, An inorganic powder filler such as talc, and a fibrous filler such as glass fiber, pulp fiber, synthetic fiber, and ceramic fiber can be contained. The resin used for the inner layer substrate and the resin used for the prepreg may be the same or different.

The metal foil used in the present invention is not particularly limited, and a single, alloy, or composite metal foil of copper, aluminum, brass, nickel, or the like can be used.
Instead of the metal foil, a single-sided metal-clad laminate or a double-sided metal-clad laminate obtained by laminating a metal foil can also be used.

[0028]

【Example】

(Example 1) Copper foil of a glass substrate epoxy resin double-sided copper-clad laminate [manufactured by Matsushita Electric Works Co., Ltd., trade name: R-1766] having a size of 51 × 34 cm and a thickness of 0.2 mm excluding the copper foil (thickness: 35 µm) Is etched and the surface is 0.15 m wide
Thus, a substrate for an inner layer having a copper circuit of m was obtained. Then, after pre-treating the inner layer substrate with a roughening pretreatment liquid under the following conditions,
After pre-treating with a roughening pre-treatment liquid, the sheet is conveyed in air at 30 ° C., and then immersed in water and washed, under the condition that the time for conveyance in air is 30 seconds during immersion in the cleaning liquid after immersion in the cleaning liquid. Using an aqueous hydrochloric acid solution containing 120 g / L of hydrochloric acid at 30 ° C., 90
After a second treatment and then washing with water, an acid-resistant surface-roughening treatment under the following conditions was carried out, followed by water washing to obtain an acid-resistant surface-roughened inner layer substrate.

In the pretreatment method, the inner layer substrate was immersed for 90 seconds in a pretreatment solution for surface roughening at 34 ° C., which was composed of an aqueous solution containing 130 g / L of hydrochloric acid and 15 g / L of cupric chloride.

The acid roughening treatment is carried out by adding 100 g / L of sodium chlorite, 43 g / L of sodium hydroxide,
After being immersed in an oxidation treatment solution at 75 ° C. consisting of an aqueous solution containing 15 g / L of sodium phosphate for 5 minutes, washed with water,
It dried at 30 degreeC for 30 minutes, and formed copper oxide on the copper circuit surface. Next, copper oxide was reduced and treated with a pH 3.7 treatment solution containing ethylenediaminetetraacetic acid, dilute sulfuric acid, boric acid, and carboxylic acid.

(Example 2) An acid-resistant rough surface was prepared in the same manner as in Example 1 except that the time required for carrying in the air during the pretreatment with the pretreatment solution for roughening was 60 seconds during immersion in the cleaning solution. Thus, an inner layer substrate subjected to the chemical treatment was obtained.

(Comparative Example 1) An acid-resistant rough surface was prepared in the same manner as in Example 1 except that the time required for carrying in the air during immersion in the cleaning solution after pretreatment with the roughening pretreatment solution was 90 seconds. Thus, an inner layer substrate subjected to the chemical treatment was obtained.

(Comparative Example 2) After pretreatment with a roughening pretreatment liquid, the time for transporting in the air during immersion in the cleaning liquid is 120.
An inner layer substrate subjected to an acid-resistant surface-roughening treatment was obtained in the same manner as in Example 1 except that the time was seconds.

(Evaluation and Results) The allowable currents of the inner layer substrates obtained in Examples 1 and 2 and Comparative Examples 1 and 2 were measured. The method is to apply a current to a copper circuit and to raise the temperature of the copper circuit to 10 ° C.
The value of the rising current was determined.

The results are shown in Table 1. As shown in Table 1, each of the examples has a higher allowable current than each of the comparative examples, and the amount of current that can be passed through the copper circuit formed on the surface of the inner layer substrate is not easily reduced. Was confirmed.

[0036]

[Table 1]

[0037]

According to the method for producing a multilayer board of the present invention, the time required for transporting in the air during pre-treatment with a roughening pre-treatment liquid and immersion in a cleaning liquid is 70 seconds or less. A multilayer board is obtained in which the amount of current that can be passed through the copper circuit formed on the substrate surface is unlikely to decrease.

Claims (2)

[Claims] 1. An inner layer substrate having a copper circuit on its surface is pretreated with a roughening pretreatment solution containing hydrochloric acid and cupric chloride, transported in the air, then immersed in a cleaning solution, and then acid-resistant. Performing a surface roughening process, then laminating a prepreg on at least one surface of the inner layer substrate, laminating a metal foil on the outermost layer of the laminate, and then heating and press molding to produce a multilayer board. The method for producing a multilayer board, wherein the roughening pretreatment liquid contains hydrochloric acid at 120 to 150 g / l and cupric chloride at 10 to 20 g / l, the pretreatment with the roughening pretreatment liquid A method for producing a multilayer board, wherein the time of transport in the air during immersion in a cleaning solution after the treatment is 70 seconds or less. 2. The method for producing a multilayer board according to claim 1, wherein the temperature of the air in the portion for transporting the inner layer substrate is 0 to 40 ° C.