JPS63206476A - Pretreating liquid for electroless copper plating - Google Patents

Abstract

PURPOSE:To produce a pretreating liquid for electroless copper plating adequately used for production of printed circuit boards, etc., by preparing an aq. soln. into which borohydrofluoric acid, hydrochloric acid and imidazole are incorporated respectively at specific ratios. CONSTITUTION:The aq. soln. contg. 39-52g/l borohydrofluoric acid, 5-15ml/l hydrochloric acid in terms of aq. 37wt.% hydrochloric acid soln. and 0.05-0.3g/l imidazole is prepd. The pretreating liquid prepd. in such a manner is used for the circuit board, etc., to be subjected to the electroless copper plating at about 5-40 deg.C, more preferably 15-20 deg.C treating temp. and for about 1-15min, more preferably about 5-8min treatment time. The excellent electroless copper plating which prevents generation of scabbing and pattern drop-out is thereby formed.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to an electroless copper plating pretreatment liquid, and more particularly to an electroless copper plating pretreatment liquid that can be suitably used for manufacturing printed circuit boards, etc. It is.

[Conventional technology]

In order to perform electroless copper plating, first, the object to be plated is immersed in an aqueous solution containing a palladium compound and its reducing agent as an initiator for the plating reaction, and then the palladium compound is transferred to the object as metal palladium (Pd'). The plate is immersed in a treatment solution (pretreatment solution) to ensure smooth and effective plating, and is then plated with the plating solution. Conventionally, as the treatment liquid, an aqueous solution containing hydrochloric acid, an aqueous solution containing hydrochloric acid and oxalic acid, or an aqueous solution containing borohydrofluoric acid has been used (see, for example, Japanese Patent Publication No. 59-49305).

[Problem that the invention seeks to solve]

However, when such conventional processing liquids are used, problems such as insufficient removal of residual reducing agent and insufficient adsorption and retention of Pd' may occur, especially when printing In the manufacturing process of circuit boards, the process of drilling holes in double-sided copper-clad laminates, electroless copper plating process, electrolytic copper plating process, solder resist process, solder plating process,
When performing the resist stripping process and the etching process in this order, an aqueous solution containing hydrochloric acid or an aqueous solution containing hydrochloric acid and oxalic acid is used as a treatment solution to promote reduction and adsorption to Pd' in the pretreatment of the electroless copper plating process. If used, there are problems such as a so-called roughening phenomenon in which countless small protrusions are formed on the surface in the next step of electrolytic copper plating. Further, when an aqueous borofluoric acid solution is used, there is a problem that during the etching process, etching of only the electroless copper-plated portion of the cross section of the pattern is accelerated, so-called pattern erosion.

The present invention has been made in view of the above circumstances, and its purpose is to solve the above-mentioned problems, to prevent etching damage and roughness of the substrate surface, and to form a palladium compound Pd'. The purpose of the present invention is to provide an electroless copper plating pretreatment liquid that has excellent basic properties as a plating pretreatment liquid, such as reduction of Pd', promotion of Pd' adsorption, and retention properties.

[Means for solving problems]

As a result of extensive studies to solve the above problems, the present inventors have found that a treatment liquid containing borofluoric acid, hydrochloric acid, and a specific organic compound at specific concentrations has achieved the above objective. The discovery of scales led to the completion of the present invention.

That is, in the present invention, borohydrofluoric acid is added in an amount of 39 to 52 g/
l, 5 to 15 m when converting hydrochloric acid to 37% by weight aqueous hydrochloric acid solution
1/l, imidazole 0.05-0.3 g/l
The present invention relates to an electroless copper plating pretreatment liquid characterized by being composed of an aqueous solution containing l.

The method for producing the pretreatment liquid of the present invention is not particularly limited as long as it contains each of the above-mentioned components at the above-mentioned concentrations.
It can be obtained by uniformly mixing BF, ) or a hydrate or aqueous solution thereof, hydrochloric acid, imidazole, and, if necessary, water to obtain an aqueous solution having the above composition. These raw material compounds or raw material aqueous solutions may be pure products, commercially available industrial products, or newly produced by known methods.

One of the important points in the present invention is that the concentration of each component in the pretreatment liquid of the present invention is set within the above-mentioned value ranges. The pre-treatment liquid of the present invention is used as a pre-treatment liquid in electroless copper plating, and is particularly used in the manufacturing process of printed circuit boards, in the drilling process of substrates, in the electroless plating process, in the electrolytic copper plating process, and in the soldering process. It is used as a pre-treatment liquid in the electroless copper plating process when the resist process, solder plating process, resist stripping process, and etching process are performed in this order. If the concentration of any one of the components of hydrogen acid, hydrochloric acid, and imidazole is not within the above concentration range, the plating promotion effect during electroless copper plating may not be sufficient or the plating properties may deteriorate. In particular, problems such as roughness occurring during the electrolytic copper plating process and pattern erosion occurring during the etching process are undesirable.

The electroless copper plating pretreatment liquid of the present invention is an excellent pretreatment liquid that does not cause the above-mentioned problems, and can be suitably used as a pretreatment liquid for general electroless copper plating. In particular, it can be suitably used as a pretreatment solution for electroless copper plating in the production of printed circuit boards as described above.
It is.

The pretreatment liquid of the present invention can be used to treat inorganic materials such as ceramics, glasses, and minerals as a pretreatment liquid for electroless copper plating.
Plastics such as epoxy resins, phenolic resins, and polycarbonate resins; synthetic organic materials such as synthetic fibers and synthetic rubbers; natural materials such as natural rubber, natural fibers, vegetable materials such as wood, and animal materials; In principle, it can be applied to almost any insulating material, semiconductor material, conductive material, etc., such as composite materials, metallic materials, metal clad materials, metal plating materials, etc., and the shape of the material. It can also be used without any limitation, but in particular, ceramic boards used as substrates for printed circuit boards, resin laminates such as epoxy laminates, phenolic laminates, or boards with metal cladding such as copper cladding. It can be suitably used for.

When using the pretreatment liquid of the present invention, the following procedure may generally be used, for example.

That is, the surface of a material such as a substrate to which electroless copper plating is applied is degreased as necessary, washed with hot water, washed with water, treated with a dilute acid such as dilute sulfuric acid, and then treated with a catalyst precursor such as a palladium compound and dichloromethane.
Before the present invention, a catalyst such as palladium or a plating initiator is deposited on the surface by dipping, coating, spraying, etc. with a reducing agent such as soot and a catalyst solution such as an aqueous solution containing hydrochloric acid, and then washing with water. Treat with processing solution. This treatment can be done by simply dipping or painting. The treated surface can be transferred to the conventional electroless copper plating process by simply rinsing with water.

The treatment temperature and treatment time when performing the above pretreatment cannot be uniformly specified because they vary depending on various other conditions such as the type of material, but for example, the treatment temperature is usually 5 to 40 °C, preferably 15 to 20 °C, A method in which the treatment time is usually set in the range of 1 to 15 minutes, preferably 5 to 8 minutes can be suitably used.

[Effect]

When the pretreatment liquid of the present invention is used, the basic properties during the electroless copper plating process are maintained or improved, and the roughness phenomenon and pattern erosion are prevented, especially in the production of printed circuit boards as described above. You can get excellent effects such as This effect is caused by the pretreatment liquid of the present invention having a specific composition, but there are many points about its mechanism of action that are unclear at this stage and cannot be stated conclusively. The present inventors' estimates or ideas regarding the mechanism of action are shown.

If the pretreatment solution contains more hydrochloric acid than necessary, a large amount of hydrochloric acid will remain on the surface of the treated substrate, and when this substrate remains while going to the next process, Copper (Cu') is hydrochloric acid or its decomposition products (C1, etc.)
It is presumed that this causes the so-called roughness phenomenon to occur. This etching phenomenon becomes more pronounced as the number of substrates to be processed increases.

Further, as an effect of adding imidazole, for example, imidazole forms a complex with copper, which is thought to suppress or prevent etching.

For the reasons mentioned above, it is thought that etching of copper on the surface of the substrate, which causes roughness, could be prevented by selecting a hydrochloric acid concentration that does not involve copper in etching and adding imidazole at a specific concentration.

Furthermore, when performing electroless copper plating, it is usually necessary to attach palladium (Pd') as an initiator for the plating reaction to the surface of the object to be plated prior to plating. A hydrochloric acid solution containing palladium chloride and soot chloride as main components is usually used as a treatment solution for depositing Pdo before electroless copper plating. From this mixed solution attached to the substrate surface, a reaction promoted by subsequent water washing, etc.
``+Sn2'' = Pd' + Sn4+, palladium gold i (Pd'''), stannous 7 (Sn''°)
These soots, which produce unreacted stannous ions (Sn'°), etc., can be removed using conventional aqueous borofluoric acid solutions, for example, borofluoric acid at a concentration of about 52 g/12 borofluoric acid. Even when treated with an aqueous solution, it remains without being completely removed, and this residual tin is used to remove copper from areas that are not covered with solder after electroless copper plating, electrolytic plating, baking, development, and solder plating. During the alkaline etching process, residual tin is removed by the alkali such as ammonia contained in the alkaline etching solution.
It is thought that so-called pattern erosion occurs, but since the pretreatment liquid of the present invention has an appropriate amount of hydrochloric acid added to borofluoric acid at an appropriate concentration, it maintains the adsorption of palladium and In the pre-treatment process of electroless copper plating, it is now possible to effectively remove residual tin components.
As a result, pattern erosion can be considered to have been prevented.

As described above, electroless copper plating is effective because the pretreatment liquid of the present invention contains appropriate concentrations of borofluoric acid, hydrochloric acid, and imidazole for the above-mentioned improvement effects, etc. It can be assumed that the process was carried out quickly and smoothly, and furthermore, it was possible to prevent roughness and pattern erosion.

〔Example〕

Hereinafter, the present invention will be explained in detail based on Examples, but the present invention is not limited thereto.

Example 1 Copper-clad glass-epoxy laminates (trade name MCL-E-67, manufactured by Hitachi Chemical Co., Ltd.) were prepared with Nos. to N shown in Table 1.
It was processed continuously according to the processing steps up to o1B, and electroless copper plating was applied. In Table 1, ClO201 is a degreasing and hydrophilic treatment agent (trade name C manufactured by Hitachi Chemical Co., Ltd.).
1O201), H3-202B represents treatment with a catalyst solution consisting of palladium chloride, stannous chloride, and hydrochloric acid (trade name H3-202B, manufactured by Hitachi Chemical Co., Ltd.), and CUST-201 represents electroless treatment. Copper plating solution (manufactured by Hitachi Chemical Co., Ltd., product name CUST-20)
1) represents the processing according to 1).

In this Example 1, the concentration of cyclic hydrofluoric acid was 52 g/it, and the concentration of hydrochloric acid was 1j? as the treatment liquid for the pretreatment of the present invention. 10 per 37% hydrochloric acid
Concentration equivalent to ml, imidazole concentration is 0.1g
/β was used.

The samples treated in Table 1 were immersed in a normal copper birophosphate electroplating bath and electrolytically plated at 55°C. After this electrolytic copper plating was applied, the presence or absence of roughness on the substrate surface was visually observed. Further, the electrolytic copper-plated substrate was further subjected to baking, development, and solder plating, and then alkali etching was performed to etch the portions not covered with solder plating. The etching state was observed using a microscope (magnification: 50).
Each of the above methods was carried out 20 times, and the occurrence rates of roughness and pattern erosion are shown in Table 2.

ur-all white Table 1 However, the flight time between each treatment was 27 seconds.

11~'''i The internal disputes are shown in the text.

Comparative Example 1 Comparative Example 1 was carried out in the same manner as in Example 1, except that an aqueous borohydrofluoric acid solution (?52 g/It) was used in place of the pretreatment liquid used in Example 1. The results are shown in Table 2 according to the same method of presenting the results of Example 1.

Comparative Example 2 In place of the pretreatment liquid used in Example 1, the concentration of boric acid/hydrocranic acid was 39 gzl, and the concentration of hydrochloric acid was 1! Hit 37%
The same procedure as in Example 1 was carried out except that an aqueous solution having a concentration equivalent to 82 ml of hydrochloric acid was used. The results are shown in Table 2 in a manner similar to that of Example 1.

Table 2 with blank space below “1.” Meikaell 1, Hill JCIII 1 and 2
The number of occurrences when 20 giant chicks were pounded in the same manner for each is shown below. It is possible to provide an excellent pretreatment solution for electroless copper plating that can prevent the occurrence of roughness, pattern erosion, etc. in the printed circuit manufacturing process.

Claims (1)

[Claims] 1. It consists of an aqueous solution containing 39 to 52 g/l of borofluoric acid, 5 to 15 ml/l of hydrochloric acid converted to a 37% by weight aqueous hydrochloric acid solution, and 0.05 to 0.3 g/l of imidazole. Electroless copper plating pre-treatment solution.