JP2008088523A - Reaction accelerator for electroless copper plating bath - Google Patents

Abstract

The present invention provides a reaction accelerator for an electroless copper plating bath that can easily provide an electroless copper plating bath having both a deposition rate and bath stability.
The following formula (I),
[Chemical 1]

(Wherein R and R ′ each independently represent hydrogen or an alkyl group having 1 to 4 carbon atoms, and X ⁻ represents a counter anion)
A reaction accelerator for an electroless copper plating bath, comprising a diallylamine-based polymer having a structural unit represented by:
[Selection] Figure 1

Description

  The present invention relates to a reaction accelerator for an electroless copper plating bath that can accelerate the reaction of the electroless copper plating bath.

  Electroless copper plating baths are a fairly mature technology, and many types of plating baths are sold by various plating chemical manufacturers. Some of them have features such as, for example, those that have zero stress and good adhesion on the resin, and those that are extremely thick and aimed at high speed at the expense of stability. However, the most common type is a bath having a specification that has a moderate deposition rate and bath stability when used near room temperature.

  In order to improve the deposition rate of the electroless copper plating bath, the concentration of formaldehyde as a reducing agent may be increased or the concentration of the stabilizer may be decreased, but this causes a problem that the bath stability is lowered. Further, in order to improve the bath stability, it is sufficient to increase the amount of the stabilizer or use a stabilizer having a strong sulfur-based inhibitory force, but this causes a problem that the deposition rate is lowered.

  As described above, in the conventional common sense, it was said that the deposition rate and stability could not be compatible, but the present invention is contrary to such common sense, electroless copper plating having both high deposition rate and bath stability. It was made into the subject to provide the reaction promoter for electroless copper plating baths which can provide a bath simply.

  As a result of intensive studies to solve the above problems, the present inventors have found that an electroless copper plating bath to which a specific diallylamine-based polymer is added has a high deposition rate and bath stability. The present invention has been completed.

That is, the present invention provides the following formula (I),
(Wherein R and R ′ each independently represent hydrogen or an alkyl group having 1 to 4 carbon atoms, and X ⁻ represents a counter anion)
A reaction accelerator for an electroless copper plating bath, comprising a diallylamine-based polymer having a structural unit represented by:

  Moreover, this invention is an electroless copper plating bath characterized by containing the said diallylamine type polymer, copper salt, a chelating agent, and a reducing agent.

  Furthermore, the present invention is an electroless copper plating method characterized by immersing an object to be plated in the electroless copper plating bath.

  The reaction accelerator for an electroless copper plating bath of the present invention is an excellent one that can have a high deposition rate and bath stability by adding it to the electroless copper plating bath.

  Therefore, when electroless copper plating is applied to an object to be plated using an electroless copper plating bath to which a reaction accelerator for electroless copper plating bath is added, electroless copper plating should be applied more stably in a shorter time than before. Can do.

The reaction accelerator for an electroless copper plating bath of the present invention (hereinafter simply referred to as “the accelerator of the present invention”) has the following formula (I),
(Wherein R and R ′ each independently represent hydrogen or an alkyl group having 1 to 4 carbon atoms, and X ⁻ represents a counter anion)
A diallylamine-based polymer having a structural unit represented by the formula: As the structural unit (I) constituting the diallylamine polymer, both R and R ′ are preferably hydrogen or a methyl group, particularly preferably both R and R ′ are a methyl group. The anion (X ⁻ ) is preferably selected from halogen ions such as fluorine ion, chlorine ion, bromine ion and iodine ion, particularly preferably chloride ion. Further, the molecular weight of the diallylamine-based polymer is not particularly limited, but is preferably 1,000 to 100,000, and particularly preferably 2,000 to 10,000. Commercially available products of such diallylamine-based polymers include PAS-A-1 (molecular weight 5,000), PAS-A-5 (molecular weight 4,000), PASA-120L (molecular weight 100,000), PAS-A. -120S (molecular weight 100,000), PAS-92 (molecular weight 5,000) (all manufactured by Nittobo Co., Ltd.). Among these commercially available products, PAS-A-1 is preferable.

  The amount of the above-described accelerator according to the present invention added to the electroless copper plating bath is preferably 5 to 200 mg / L, particularly 10 to 100 mg / L in the electroless copper plating bath. preferable. The method of adding the accelerator of the present invention to the electroless copper plating bath is not particularly limited. For example, the accelerator may be added to the electroless copper plating bath before plating, and mixed and stirred.

  Moreover, there is no restriction | limiting in particular as a composition of the electroless copper plating bath to which this invention promoter is added, For example, what contains a copper salt, a chelating agent, and a reducing agent is preferable. Examples of the copper salt contained in the electroless copper plating bath include cupric chloride and copper sulfate. Among these, cupric chloride is preferable. The concentration of the copper salt in the electroless copper plating bath is preferably 1.5 to 4 g / L, particularly preferably 2 to 3 g / L, as copper. Examples of the chelating agent include Rochelle salt or EDTA such as ethylenediaminetetraacetic acid (EDTA), EDTA disodium salt, EDTA tetrasodium salt, and the like. Among these, EDTA or a salt thereof is preferable. EDTA is preferred. The concentration of the chelating agent in the electroless copper plating bath is preferably 5 to 50 g / L, and particularly preferably 10 to 50 g / L. Furthermore, examples of the reducing agent include hypophosphite, formaldehyde, dimethylamine borane, etc. Among these, formaldehyde is preferable. The concentration of the reducing agent in the electroless copper plating bath is preferably 3 to 30 g / L, and particularly preferably 3 to 20 g / L. Furthermore, a stabilizer, a pH adjuster and the like may be added to the electroless copper plating bath as long as the effects of the present invention are not hindered. Examples of the stabilizer include one or more stabilizers selected from cyan compounds such as sodium cyanide, nitrogen compounds such as 2-2′dipyridyl, and sulfur compounds such as thiourea. Among these stabilizers, 2 It is preferable to use -2′dipyridyl from the viewpoint of environmental considerations. The concentration of these stabilizers in the electroless copper plating bath is, for example, 10 to 100 mg / L for a cyan compound, 0.1 to 100 mg / L for a nitrogen compound, and 0.01 to 10 mg for a sulfur compound. / L. Moreover, sodium hydroxide etc. are mentioned as a pH adjuster. The concentration of sodium hydroxide in the electroless copper plating bath is preferably 3 to 20 g / L. When sodium hydroxide is added to the electroless copper plating bath at this concentration, the pH becomes about 10.5 to 14.

A preferred embodiment of the electroless copper plating bath to which the accelerator of the present invention is added is as follows.
<Electroless copper plating bath composition>
Cupric chloride or copper sulfate: 2-3 g / L as copper
EDTA: 10-50 g / L
Formaldehyde: 3-20g / L
2-2′dipyridyl: 0.1 to 100 mg / L
Sodium hydroxide: 3 to 20 g / L

  As described above, electroless copper plating can be performed by immersing an object to be plated in an electroless copper plating bath to which the promoter of the present invention is added (hereinafter referred to as “the present plating bath”). The electroless copper plating conditions are not particularly limited. For example, the plating object is placed on the plating bath of the present invention at 20 to 40 ° C., preferably 25 to 40 ° C. for 10 to 20 minutes, preferably 15 to 20 minutes. The conditions to immerse are mentioned. In electroless copper plating, air bubbling is preferably performed with an air supply amount of 0.1 to 1 L per 1 L of the plating bath.

  It is preferable that pre-treatment such as degreasing, washing, etching, applying a catalyst, and activating a catalyst is performed on an object to be plated with electroless copper plating in the plating bath of the present invention. As such pretreatment, a part of an electroless copper plating system such as a risertron system (manufactured by Ebara Eugene Corporation) may be used.

  Examples of the object to be plated in the plating bath of the present invention include printed circuit boards and engineering plastics. Among these, printed circuit boards are preferable.

  According to the plating method using the plating bath of the present invention described above, the plating time can be shortened because the deposition rate of the plating bath of the present invention is high.

  EXAMPLES Hereinafter, although an Example is given and this invention is demonstrated, this invention is not restrict | limited to these at all.

Example 1
Preparation of electroless copper plating bath (1):
A diallylamine polymer (PAS-A-1) having a molecular weight of 5,000, which is a polymer having a structural unit represented by the following formula (II) in an electroless copper plating bath having the following composition: Nittobo Co., Ltd.) was added and mixed at 10 mg / L to prepare an electroless copper plating bath.

<Electroless copper plating bath composition>
Cupric chloride: 2.5 g / L as copper
EDTA: 20g / L
Sodium hydroxide: 10 g / L
Formaldehyde: 6g / L
2-2′dipyridyl: 30 mg / L

Example 2
Preparation of electroless copper plating bath (2):
Instead of adding PAS-A-1 having a molecular weight of 5,000 in Example 1 and adding and mixing 10 mg / L of a diallylamine polymer having a molecular weight of 4,000 (PAS-A-5; manufactured by Nittobo Co., Ltd.). An electroless copper plating bath was prepared in the same manner as in Example 1.

Example 3
Examination of deposition rate (1):
The electroless copper plating bath prepared in Example 1 or Example 2 was adjusted to 35 ° C. In this electroless plating bath, an epoxy plate (made by Matsushita Electric Works Co., Ltd.) treated with a risertron system (made by Ebara Eugleite Co., Ltd.) until catalyst activation (accelerator) was immersed. The film thickness per each immersion time was calculated from the weight of the epoxy plate. Moreover, the same measurement was performed also about what changed the electroless copper plating bath (PB-503F: EBARA Eugleite Co., Ltd.) to 25 degreeC as a comparison. The relationship between the film thickness and the immersion time is shown in FIG.

  The electroless copper plating baths of Example 1 and Example 2 were able to achieve the same film thickness with a shorter immersion time than PB-503F.

Example 4
Examination of through hole coverage:
The electroless copper plating bath of Example 1 was adjusted to 35 ° C. On the other hand, a printed circuit board (FR-4: manufactured by Matsushita Electric Works Co., Ltd.) having a through hole of 1.0 mmφ × 1.6 mmt was activated in the riser system as in Example 3 (accelerator). After the treatment, it was immersed in the electroless copper plating bath. The copper plating coverage in the through hole at each immersion time was evaluated by the following backlight test and criteria. Moreover, the same measurement was performed also about what changed the electroless copper plating bath (PB-503F: EBARA Eugleite Co., Ltd.) to 25 degreeC as a comparison.

<Backlight test>
After each immersion time, the through hole was cut open to expose the inner wall of the through hole, and a light was applied to the through hole from below, and the light blocking condition was evaluated according to the following evaluation criteria. Moreover, an example of the result of the backlight test after 5 minutes, 10 minutes and 15 minutes after immersion is shown in FIG.

<Evaluation criteria>
(Evaluation) (Content)
Rating No. 0: The through hole is not covered with copper plating at all. Rating No. 10: The through hole is completely covered with copper plating and shielded from light. It was.

  The electroless copper plating bath of Example 1 could completely cover the through hole in a shorter time than PB-503F.

Example 5
Examination of bath stability (1):
The electroless copper plating bath of Example 1 was placed in a glass bottle with a capacity of 100 ml, sealed with a lid. Subsequently, this was heated with a 50 degreeC warm bath, and the time until copper began to precipitate was measured. For comparison, the same measurement was performed for an electroless copper plating bath (PB-503F: manufactured by Sugawara Eugleite Co., Ltd.).

  The electroless copper plating bath of Example 1 was more stable than PB-503F.

Example 6
Examination of bath stability (2):
The electroless copper plating bath of Example 1 was placed in a glass bottle with a capacity of 100 ml, sealed with a lid. Next, this was allowed to stand at room temperature (daytime, about 25 ° C .: nighttime, about 15 ° C.), and the number of days until copper began to precipitate was measured. For comparison, the same measurement was performed for an electroless copper plating bath (PB-503F: manufactured by Sugawara Eugleite Co., Ltd.).

  The electroless copper plating bath of Example 1 had the same degree of stability as PB-503F, and there was no practical problem.

Example 7
Examination of bath stability (3):
A printed circuit board (FR-4: manufactured by Matsushita Electric Works Co., Ltd.) on which a 1.0 mmφ × 1.6 mmt through hole was formed was processed up to an accelerator with a risertron system in the same manner as in Test Example 1, and this was maintained at 35 ° C. It was immersed in the adjusted electroless copper plating bath of Example 1. After dipping, the printed circuit board was taken out and allowed to stand with the bath temperature maintained, and the number of days until copper began to precipitate was measured. Moreover, the same measurement was performed also about what changed the electroless copper plating bath (PB-503F: EBARA Eugleite Co., Ltd.) to 25 degreeC as a comparison.

  The electroless copper plating bath of Example 1 has stability superior to PB-503F even in actual operation.

Example 8
Examination of deposition rate (2):
An electroless copper plating bath in which the content of PAS-A-1 in the electroless copper plating bath of Example 1 was replaced with 20 mg / L or 30 mg / L was prepared. In this electroless copper plating bath, the copper deposition rate was measured by the following method when a resin substrate (FR-4 (manufactured by Matsushita Electric Works) was stripped of copper) was immersed for 15 minutes. In addition, the copper deposition rate was measured in the same manner as described above for the electroless copper plating bath in which the content of PAS-A-5 in the electroless copper plating bath of Example 2 was replaced with 20 mg / L or 30 mg / L. . These results are shown in FIG.

<Measurement of deposition rate>
First, the weight of the resin substrate was measured. Next, the resin substrate was processed up to the accelerator with the risertron system in the same manner as in Test Example 1, and immersed in an electroless copper plating bath adjusted to 35 ° C. for 15 minutes. Thereafter, the weight of the resin substrate after copper plating was measured, and the film thickness and deposition rate of the copper plating applied on the resin substrate were calculated from the change in weight and the like.

  When using the electroless copper plating bath of the present invention, the copper deposition rate increased depending on the concentrations of PAS-A-1 and PAS-A-5 to be added.

  The reaction accelerator for an electroless copper plating bath of the present invention can have both a high deposition rate and bath stability only by adding it to a conventional electroless copper plating bath.

  Therefore, the reaction accelerator for electroless copper plating bath can be suitably used for shortening the time of electroless copper plating process.

FIG. 1 is a drawing showing the relationship between film thickness and immersion time when electroless copper plating is applied in electroless copper plating baths of Example 1, Example 2 and PB-503F. FIG. 2 is a drawing showing an example of a result of a backlight test on a printed circuit board when electroless copper plating is performed in Example 1 and an electroless copper plating bath of PB-503F. FIG. 3 is a drawing showing deposition rates at various concentrations of PAS-A-1 and PAS-A-5 in an electroless copper plating bath.

Claims (5)

The following formula (I),
(Wherein R and R ′ each independently represent hydrogen or an alkyl group having 1 to 4 carbon atoms, and X ⁻ represents a counter anion)
A reaction accelerator for an electroless copper plating bath, comprising a diallylamine-based polymer having a structural unit represented by: The following formula (I),
(Wherein R and R ′ each independently represent hydrogen or an alkyl group having 1 to 4 carbon atoms, and X ⁻ represents a counter anion)
An electroless copper plating bath comprising a diallylamine-based polymer having a structural unit represented by the formula: a copper salt, a chelating agent and a reducing agent.   The electroless copper plating bath according to claim 2, wherein the chelating agent is EDTA or a salt thereof.   An electroless copper plating method comprising immersing an object to be plated in the electroless copper plating bath according to claim 2. The electroless copper plating method according to claim 4, wherein the temperature of the electroless copper plating bath is 20 to 40 ° C.