JPH0426771A - Pretreating solution for electroless plating - Google Patents

Abstract

PURPOSE:To form a Cu plating film having superior uniformity and adhesion by electroless plating by using an alkaline aq. soln. contg. specified surfactants, a metal complexing agent and quat. ammonium alkyl ester of polymethacrylic acid as a pretreating soln. for electroless Cu plating. CONSTITUTION:When a body to be plated is electroless-plated with Cu, it is pretreated with an alkaline aq. soln. of pH>=10 contg. 0.1-50 g/l nonionic surfactant such as polyoxyethylene lauryl ether represented by a general formula RO(CH2CH2O)nH (where R is-CnH2n+1 or CnH2n+1-), 0.01-20.0g/l fluorine-contg. surfactant, 0.5-10 g/l metal complexing agent such as tartaric acid or tartrate and quat. ammonium alkyl ester of polymethacrylic acid represented by structural formula 1 (where R is alkyl and n<=50,000) to improve the wettability of the body to be plated and the adhesion after plating. The body is then immersed in an electroless Cu plating soln. and a uniform Cu plating film is formed with superior adhesive strength while nearly preventing the occurrence of blowholes due to bubbles.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a pretreatment liquid for electroless plating, and particularly to a pretreatment liquid for electroless copper plating of printed wiring boards.

[Conventional technology]

Conventionally, pretreatment steps for electroless copper plating include an alkaline degreasing step, a conditioning step, a soft etching step for the surface copper foil, an acid washing step, a sensitization step (catalyst application), and an adhesion promotion step.

As a pretreatment for electroless plating: 1. The function of conditioning is to make the lipophilic substrate hydrophilic, making it easier to wet, and promoting the adsorption effect of the catalyst in the subsequent sensitization process. be.

1986-52 Special Publication using a silane camping agent for use on objects to be plated that are difficult to plate, such as glass.
The technology disclosed in Publication No. 701? [Problems to be Solved by the Invention] However, when conventional pretreatment liquids are used, water wettability and defoaming properties during conditioning may not always be sufficient, and blowholes and through holes may occur during immersion in a solder bath. A problem arises in that the catalyst is not adsorbed due to air bubbles remaining within the plate, resulting in ring-shaped plating voids.

This tendency is remarkable in small through-holes (diameter of 0.4 mm or less). In addition, for composite insulating materials made of synthetic resin mixed with paper or glass fiber,
The glass fibers and the like may be exposed on the surface, and even if suitable conditions are selected, the phenomenon in which electroless plating is not deposited on this portion is considered a problem. The present invention has been made in view of these circumstances, and provides a pretreatment liquid for electroless plating that has excellent wettability and plating adhesion.

[Means to solve the problem]

The first claim of the present invention is a nonionic surfactant, a fluorine-containing ionic surfactant, a metal complexing agent, and a polymethacrylic acid quaternary ammonium alkyl ester.
+ (10 or more) This is a pretreatment liquid for electroless plating consisting of an aqueous alkali solution.

In addition, as the nonionic surfactant in the second claim, H, L, B (Hydrophile Lip
ophile Balance) is 11-16, which is suitable for degreasing due to its hydrophilicity.
It is also thought to improve the water wettability of the object to be plated.

These have the general formula RO(CHzCHzO) ,,H (where R: C,H2-,1,C,,Hzo-+
), specifically, polyoxyethylene lauryl ether, polyoxyethylene cedylconite, polyoxyethylene oleyl ether, polyoxyethylene stearyl ether, polyol; 1-ethylene octylphenyl ether, polyoxyethylene l/
nonylphenyl ether is used.

Further, the fluorine-containing surfactant in the first claim is a fluorine-containing surfactant having a perfluoroalkenyl group obtained by polymerization of tetrafluoroethylene, and a fluorine-containing surfactant obtained by copolymerizing hexafluoroprohene. Fluorine-containing surfactants having a perfluoroalkenyl group, those derived from linear perfluorocarboxylic acid fluorides by electrolytic fluorination, and perfluoroalkylethyl derived from perfluoro iodides obtained by telomerization. Alcohol derivatives are exemplified.

The metal complexing agent in the third claim includes tartaric acid or a salt thereof, ethylenediaminetetraacetic acid or a salt thereof, ethylenediaminetetra-2-propanol, triethanolamine, monoethanolamine, sodium gluconate, citric acid, or Mixtures thereof may be mentioned.

As for the quaternary ammonium alkyl co-stellate polymethacrylate in the fourth claim, the concentrations of the components having the structural formula may generally be set within the following ranges. That is, the nonionic surfactant is 0.1 to 50 g#, and the fluorine-containing surfactant is 0.01 to 20.0 g#. g
/1, as a metal complexing agent, 0.5~]Og/e is preferable.

If the concentration of each component is not within the above range, when used as a pretreatment for electroless plating, water wettability in the holes of the substrate may not be sufficient, blowholes may occur, or there may be problems in the through-holes. Air bubbles may remain, resulting in ring-shaped plating voids.

When using the pretreatment liquid of the present invention, the following procedure may be used. When a substrate is used as the base material, holes are formed in the substrate as necessary, and then the substrate is treated with the pretreatment liquid of the present invention. For this pretreatment, simply immersing the substrate in a pretreatment liquid is sufficient. The treatment temperature when using this pretreatment liquid is 40℃~
The temperature may be 80° C., and the processing time may be about 2 to 8 minutes.

After a simple water wash, the substrate treated in this way is subjected to a soft etching process, a pickling process, a pre-dipping process, and a sensitizing process (applying a plating initiator such as palladium).
After passing through a general pretreatment process such as an adhesion promoter process, it can be transferred to an electroless copper plating process. In manufacturing printed wiring boards, the substrate subjected to the above electroless plating is further subjected to treatments such as electrolytic plating process, solder resist process, solder plating process, resist #I release process, etching process, etc. to obtain the product. be able to.

[Effect]

When the pretreatment liquid of the present invention is used, in addition to cleaning the substrate surface, it is possible to significantly improve the water wettability of a base material such as a substrate, and prevent the generation of blow poles and the remaining of air bubbles in through holes.

As a result, the deposition properties and uniformity of electroless plating are significantly improved.
Therefore, excellent printed wiring board products can be manufactured stably and efficiently.

Regarding the mechanism of action of each component or its liquid composition, there are many points that are unclear at this stage and cannot be clearly stated, but the following points can be surmised.

It can be inferred that the nonionic surfactant in this treatment liquid has an effect of improving water wettability by adjusting hydrophilicity and hydrophobicity. Fluorine-containing surfactants are
In addition to exhibiting the effect of lowering surface tension, it also has permeability, and is considered to be effective in improving the defoaming properties in through-holes of base materials such as substrates.

By treating the base material of polymethacrylic acid quaternary ammonium alkyl ester with an alkaline aqueous solution with a pH of 10 or higher, polymethacrylic acid quaternary ammonium alkyl ester, which has an active functional group that easily forms a chelate with Pd6 in the molecule, is produced. It is presumed that the treatment in the sensitization step makes it easier to adsorb the Pd° catalyst, and in particular has an effect of uniformly adsorbing it on the glass portion. As a result, the coverage of the plating inside the through-holes is significantly improved, leading to suppression of blowholes.

It is believed that the above-mentioned excellent effects are produced by the cooperative action of these components.

〔Example〕

Example 1 Three types of double-sided copper-clad laminates with different standards, plate thickness 3゜0mm
(NEMA standard FR-4, OEM-1, and OEM-3 materials) were made into test samples by drilling holes with a drill having a diameter of 0.3 mm. Number of holes: This substrate with 600 holes was immersed in Example 1, Example invention solution, 200 g/I ammonium persulfate (soft etching), 10% Hz SO4 (pickling solution)
, 270g/IPD-201 (Bridimp Hitachi Chemical H3201B (exacerbant, Hitachi Chemical), AD
Perform electroless plating pretreatment with P401 (adhesion promoter, manufactured by Hitachi Chemical), perform plating with CUST-201 (electroless copper plating solution, manufactured by Hitachi Chemical) for 20 minutes, and then proceed to step 3 of copper pyrophosphate plating. /dm'' for 64 minutes, and after forming the circuit, a through hole void generation and blow pole generation test was performed.

Table 1 shows the results of Example ■, Example 2, Comparative Example 1, and Comparative Example 2.
Shown below.

Composition of Example 1 1) Nonio 7MS-210, which is polyoxyethylene octylphenyl ether; 2 g/6 (NOF Corporation 5 trade name) 2) Unisafe HFA-5820; Ig/j! (NOF Corporation, trade name) 3) Ethylenediaminetetraacetic acid (EDTA) i1g/ρ 4) Neofix R3, a polymethacrylic acid quaternary ammonium alkyl ester (NICCA Chemical Co., Ltd., trade name); 2g/ρ1) ~
Composition of Pretreatment Solution Example 2 of aqueous alkaline solution with pH 10 containing 4) 1) Nonio 7NS-212, which is polyoxine ethylene nonylphenyl ether; 251 (Joined Neo.Product name);I
g/j! 3) Triethanolamine; 2g/7!4)
Composition of Comparative Example 1 of pre-treatment liquid of alkaline aqueous solution at pH 12 containing Neofix R5, which is polymeccryl #quaternary ammonium alkyl ester; 2 g# l) to 4) 1) Nonion H3, which is polyoxyethylene ocdylphenyl ether -210i2g/l (Nippon Oil & Fats Co., Ltd., trade name) 2) Catinal DC-80, behenyltrimethylammonium chloride: 2g/l (Toho Chemical Co., Ltd., tradename) Composition of Comparative Example 2 l) Polyoxyethylene nonyl Phenol ether nonion H5-210; 4g/j! (Hiki Yushi Co., Ltd.,
(Product name) γ-Aminopropyltriethoxysilane; 2g/6 (Product name of Nippon Unicar Co., Ltd.) No flow treatment.

Le test; Humidity 95 according to MIL standard p-5110
The number of blow balls generated when the sample was left in a 7211r at a temperature of 65°C to sufficiently absorb moisture and then immersed in a solder bath heated to 260°C was counted.

As the results of Examples 1 to 2 and Comparative Examples 1 and 2 are shown in Table 1, the pretreatment liquids of Examples 1 and 2 were clearly superior to Comparative Examples 1 and 2.

〔Effect of the invention〕

As explained in Section 2 below, the present invention has excellent water wettability for substrates such as substrates for printed wiring boards, reduces the occurrence of blowholes in perforated substrates, and improves air release properties in through holes. It is possible to provide a pretreatment liquid for electroless plating that has excellent properties, can significantly improve the deposition properties and uniformity of electroless plating, and can prevent the occurrence of plating voids.

Claims (4)

[Claims] 1. A pretreatment solution for electroless plating comprising an alkaline aqueous solution with a pH of 10 or more containing a nonionic surfactant, a fluorine-containing surfactant, a metal complexing agent, and a quaternary ammonium alkyl ester of polymethacrylate. 2. Nonionic surfactants have the general formula RO(CH_2CH_
2O)_nH (However, R: -C_nH_2_n_+_1
, C_nH_2_n_+_1-). 3. The metal complexing agent is tartaric acid or its salt, ethylenediaminetetraacetic acid or its salt, ethylenediaminetetra-2-propanol, triethanolamine, monoethanolamine, gluconic acid or its salt, citric acid or its salt, or a mixture thereof. A pretreatment liquid for electroless plating according to claim 1. 4. The pretreatment liquid for electroless plating according to claim 1, wherein the quaternary ammonium alkyl ester of polymethacrylic acid has the following general formula. ▲There are mathematical formulas, chemical formulas, tables, etc.▼ R: Alkyl group, n = 50,000 or less