JPH07286281A - Electroless copper plating solution - Google Patents

Abstract

PURPOSE:To lower the plating deposition stress and to improve the the plating deposition rate, plating appearance and stability of electroless copper plating soln. by adding alpha,alpha'-dipyridyl, mercaptosuccinic acid and a cyano complex compd. to the soln. CONSTITUTION:About 0.5-50mg/l alpha,alpha'-dipyridyl, about 0.1-20mg/l mercaptosuccinic acid and about 1-50mg/l cyano complex compd. are added to an electroless copper plating soln. consisting essentially of a cupric salt, copper complexing agent, reducing agent and pH regulator. The soln. is preferably controlled to about pH 11.80 to 13.00. Sodium ferrocyanide, sodium ferricyanide, etc., are used as the cyano complexing agent.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electroless copper plating solution used for manufacturing printed wiring boards.

[0002]

2. Description of the Related Art Conventionally, electroless copper plating solutions used for manufacturing printed wiring boards are divalent copper salts such as cupric sulfate and alkali-soluble complexing of divalent copper ions such as ethylenediaminetetraacetic acid. The main components are agents, reducing agents such as formaldehyde, and pH adjusting agents such as alkali hydroxide.

However, the plating film obtained from this electroless copper plating solution is generally brittle and has a problem that the stability of the solution is poor. In order to improve this, Japanese Patent Laid-Open No. 52-
1733 or JP-A-43-12966, an inorganic cyano compound such as sodium cyanide,
α, α'-dipyridyl, ethylaminoethanolamine,
It is described that various additives such as nitrogen-based organic compounds such as rhodanine, thiourea, benzothiazole, 2-mercaptobenzothiazole, and sulfur-based compounds such as potassium sulfide are used.

[0004]

However, the plating solution containing an inorganic cyano compound such as sodium cyanide has poor adhesion to the base material of the inner wall of the through hole and has a high plating precipitation stress. Spherical swelling often occurs. This swelling is easy to peel off during the manufacturing process of the printed wiring board, and is a major factor causing a through hole void.

When a nitrogen-based organic compound such as thiourea, rhodanine or potassium sulfide or a sulfur-based compound is added,
Although effective for improving the stability of the plating solution, there are problems that the deposition rate is suppressed and the appearance of the deposited copper is deteriorated.

An object of the present invention is to provide an electroless copper plating solution which has a low plating deposition stress and is excellent in plating deposition rate, plating appearance and solution stability.

[0007]

The electroless copper plating solution of the present invention is an electroless copper plating solution containing a cupric salt, a copper complexing agent, a reducing agent and a pH adjuster as the main components. It is characterized by adding'-dipyridyl, mercaptosuccinic acid and a cyano complex compound.

That is, the electroless copper plating solution having a basic composition is an aqueous solution containing a cupric salt, a copper complexing agent, a reducing agent and a pH adjusting agent such as an alkali hydroxide. Copper sulfate, pentahydrate, etc. can be used as the cupric salt as a copper word, ethylenediaminetetraacetic acid and its salt can be used as the copper complexing agent, and formaldehyde or its salt as the reducing agent. An aqueous solution can be used, an alkali hydroxide is used as the pH adjuster, and the pH of the plating solution is 11.80 to 13.
It is preferable to add and adjust the content to be in the range of 00.

In addition to the above basic composition, the present invention further comprises α, α'-
It is characterized by the addition of dipyridyl, mercaptosuccinic acid and a cyano complex compound. The concentration of α, α'-dipyridyl in the plating solution is 0.5 to 50 mg / l, more preferably 1 to 20 mg / l. When the concentration of α, α'-dipyridyl is less than 0.5 mg / l, the stability is low and 50
If it exceeds mg / l, the plating deposition rate will decrease.

The concentration of mercaptosuccinic acid in the plating solution is preferably 0.1 to 20 mg / l, more preferably 1 to
Used at 10 mg / l. The concentration of mercaptosuccinic acid is 0.
If it is less than 1 mg / l, the stability is low, and if it exceeds 20 mg / l, the plating deposition rate decreases.

As the cyano complex compound, sodium ferrocyanide, potassium ferrocyanide, sodium ferricyanide, potassium ferricyanide and the like can be used. The concentration of this cyano complex compound in the plating solution is preferably 1 to 50 mg / l, more preferably 5 to 30 mg / l. If the concentration of the cyano complex compound is less than 1 mg / l, the plating appearance becomes poor, and if it exceeds 50 mg / l, swelling occurs in the through holes.

[0012]

[Function] α, α'- added to the electroless copper plating solution of the present invention
By using dipyridyl, mercaptosuccinic acid and a cyano complex compound, an electroless copper plating solution having a low plating deposition stress and excellent plating deposition rate, plating appearance and solution stability can be obtained.

[0013]

【Example】

Example 1 MCL-E67 which is a double-sided copper-clad glass epoxy laminate
(Hitachi Chemical Co., Ltd., trade name) was drilled with a 1.0 mm diameter drill, surface-polished, and subjected to high-pressure water washing to obtain a sample. As a pretreatment for plating, the sample was immersed in CLC-401 (trade name, manufactured by Hitachi Chemical Co., Ltd.), which is a cleaner conditioner, to clean and condition the surface, and then soft etching and holes on the copper foil surface. Immerse in the inner wall sensitizing solution HS-202B (Hitachi Chemical Co., Ltd., trade name) and the adhesion promoting treatment solution ADP-501 (Hitachi Chemical Co., Ltd., trade name). went. The sample that has been subjected to such pretreatment is treated with a plating solution having the following composition at a plating temperature of 40.
The plating was performed at 10 ° C for 10 minutes. (Main component of electroless copper plating solution) Copper sulphate pentahydrate ... 10g / l Ethylenediaminetetraacetic acid ...・ ・ ・ ・ ・ ・ ・ ・ 30g / l Formaldehyde (37%) ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ 10ml / l Alkali hydroxide ・ ・ ・ pH together with the above composition Amount to make 12.50 (additive) α, α'-dipyridyl ・ ・ ・ ・ ・ ・ 1mg / l Mercaptosuccinic acid ・ ・ ・ ・・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ 1 mg / l Cyano-complex compound Potassium ferrocyanide ・ ・ ・ 5 mg / l

Example 2 Plating was performed under the same plating conditions and plating pretreatment as in Example 1, using an electroless copper plating solution containing the same main components as in Example 1 with the additives having the following compositions. (Additive) α, α'-dipyridyl ・ ・ ・ ・ ・ ・ ・ ・ 20mg / l Mercaptosuccinic acid ・ ・ ・ ・ ・ ・ ・ ・・ ・ ・ ・ 10mg / l Potassium ferrocyanide ・ ・ ・ ・ 30mg / l

Comparative Example 1 An electroless copper plating solution containing the same main components as in Example 1 was used, and an additive having the following composition was used, and plating was performed under the same plating conditions and plating pretreatment as in Example 1. α, α'-dipyridyl ・ ・ ・ ・ ・ ・ 10mg / l Sodium cyanide ・ ・ ・ ・..10 mg / l

Comparative Example 2 An electroless copper plating solution having the same main components as in Example 1 was prepared using the additives having the following compositions, under the same plating conditions and plating pretreatment as in Example 1. α, α'-dipyridyl ・ ・ ・ ・ ・ ・ ・ ・ 10mg / l Potassium sulfide ・ ・ ・ ・ ・ ・..... 1 mg / l

The appearance of the plating is visually evaluated, and the evaluation result shows the color visually. Blisters are holes 1 in each sample
Sample No. 00 was evaluated by cutting the sample at the center of the through hole using a precision low speed cutting machine and then counting the number of holes in which blistering occurred with a stereoscopic microscope. The stability of the liquid is low if copper oxide (Cu ₂ O) is added at 5 mg / l and plated for 5 hours, and if decomposed copper deposited on the bottom of the beaker occurs,
It was evaluated by the presence or absence of generation of the decomposed copper. The plating deposition amount was calculated from the difference in weight before and after plating after performing the same plating pretreatment on the SUS plate as described above. The evaluation results are shown in Table 1.

[0018]

[Table 1]

[0019]

As described above, according to the present invention,
It is possible to provide an electroless copper plating solution which has a low plating deposition stress and is excellent in plating deposition rate, plating appearance and solution stability.

Claims (1)

[Claims] 1. An electroless copper plating solution containing a cupric salt, a copper complexing agent, a reducing agent, and a pH adjusting agent as main components, to which α, α'-dipyridyl, mercaptosuccinic acid and a cyano complex compound were added. An electroless copper plating solution characterized in that