JPH0239594B2 - - Google Patents

Description

Claim 1: A composition in the form of an aqueous solution for activating a substrate for electroless metallization, the composition comprising a catalyst for chemically reducing dissolved salts of metals to be plated in an electroless plating bath. at least one chloride of a noble metal capable of forming a protective metal sol in water; from the chloride ion supplied by the noble metal chloride and the chloride for forming a protective metal sol; sodium chloride and/or hydrochloric acid as a chloride ion source that also supplies excess chloride ions, and aliphatic carboxylic acids,
at least one selected from the group consisting of aromatic carboxylic acids, amino acids, and combinations thereof;
~80 g/m of an organic acid substantially soluble in the plating bath. 2. The composition according to claim 1, wherein the noble metal is palladium. 3. The composition of claim 2, wherein the chloride capable of forming a protected metal sol consists of stannous chloride. 4 water, about 0.02 to 8 grams palladium per liter and about 1 to about 1 liter per liter
4. The composition of claim 3 comprising 300 grams of stannous ion. 5. The composition of claim 4 having a chloride concentration from about 0.1 normal to saturation. 6. The composition of claim 5, wherein the chloride concentration is within the range of about 3.4 to about 4.6 normal. 7. A composition according to claim 6, comprising from 0.0398 to 0.1194 grams palladium per liter and from 2 to 6 grams per liter stannous ion. 8. The composition of claim 5 or 7, wherein the acid is a component selected from the group consisting of citric acid, tartaric acid, and combinations thereof. 9. A method of plating non-conductive substrates having through-holes therein, comprising a protective metal sol in water containing at least one noble metal chloride capable of catalyzing the chemical reduction of the metal to be plated. at least one chloride that can be formed, sodium chloride and/or hydrochloric acid as a source of chloride ions providing an excess of chloride ions over the chloride ions provided by the chloride for the formation of a noble metal chloride and a protected metal sol; at least one 10~
an aqueous activation bath comprising 80 g/g of an organic acid soluble in the plating bath and selected from the group consisting of aliphatic carboxylic acids, aromatic carboxylic acids, amino acids, and combinations thereof; without subjecting the substrate to any accelerated treatment.
The above method comprises contacting the substrate with an electroless deposition plating bath containing reducible ions of the metal to be plated. Description This invention relates to electroless plating, and more particularly to an improved catalyst solution for activating non-conductive substrates and an improved electroless plating method. Methods for metallizing non-conducting substrates using precious metal baths as activators are well known. These methods are useful for applying decorative metals to items such as glass, and are particularly useful for metallizing printed circuit boards, especially those having punched or drilled holes therein. In some methods, a film of a group metal ion reducing agent, such as stannous ions, is first provided;
By subsequently applying a bath that deposits a film of a reduced noble metal, such as palladium, on the surface of the substrate,
A metal bath is used continuously. This method activates or sensitizes the substrate surface for subsequent electroless metal deposition. Various two-step activation systems and improvements are found in the art. These methods suffer from problems, particularly with regard to copper-clad laminates as substrates, such as poor metal-to-metal bonding in subsequent electroless metal plating, lack of uniformity of results, and unstable activator baths. be. These problems have been overcome to some extent by the use of a single or one-stage noble metal bath that catalyzes or activates the substrate by depositing a film of the noble metal. However, the need for an accelerating step following activation, the high cost of methods based on highly concentrated precious metal baths, the poor results with respect to pullaway at hole walls in printed circuit boards, and the use of large volumes of often dangerous chemicals. Problems remain, including problems involved in handling and disposal, long start-up times, and blistering of the metal from the substrate after deposition in the case of non-metallic substrates. BACKGROUND OF THE INVENTION Many prior art patents have discussed these and other problems and provided many solutions.
With regard to stability, sexing baths typically contain protective metals, a preferred embodiment being a tin-palladium sol, where the tin is, for example, a shipley
Protective metals, as disclosed by US Pat. No. 3,011,920. These single-metal activator baths are available in most prior art or Zeblisky U.S. patents.
It has been called colloidal or semi-colloidal in solution as in 3672938. Regardless of the physical explanation, they are all single noble metal sol activators as opposed to two-stage activator systems and are referred to herein as single or one-stage activator sols or baths. However, the presence of protective metals creates other problems in the electroless metal deposition step,
For example, long initiation times of metal deposition and blistering of metal from the substrate after metal deposition when using non-metallic substrates. When copper-clad substrates are used, poor copper-to-copper adhesion may occur after copper deposition. Hole wall pull-aways or separation of the board composite from the hole walls of thru-holes in printed circuit boards is also a problem. Pull-away can occur during melting of the tin-lead coating in operations subsequent to electrodeposition or during soldering onto the finished printed circuit board structure. What we have learned from our research is that removing facilitation results in an increase in the amount of pull-away. Although the promotion step has been said to be optional, the preferential use of a protective metal necessitates the use of a promotion step as disclosed, for example, in US Pat. No. 3,011,920 to Shipley. This applies to tin-palladium 1 for copper-clad laminates as substrates.
It is particularly desirable when using stage activator sols, but is also useful with other systems. Promoting other patents, e.g. D′Ottavio
It is also stated that this is desirable rather than necessary, such as in US Pat. No. 3,650,913. There are prior art examples where promotion has been removed. In US Pat. No. 4,073,981 to Baron, which primarily deals with coating methods for selective metal deposition, an "inert wash, preferably water," is used after acceleration. The method of this patent disclosure uses a typical one-stage activator bath known in the art consisting of a tin-palladium sol as described in this disclosure. However, no effort is made in the Baron disclosure with the removal of promotion for this activator system, presenting known problems. As will be shown later in this disclosure, these prior art problems can be properly solved and palladium-
It is a primary object of this invention to provide an unenhanced plating process that retains the advantages of a single-stage tin activator bath. The acceleration step, in addition to increasing the length of the plating process, can create its own problems. Inadequate metal coverage or void formation during the electroless deposition step may result from over-promotion. It is hypothesized that over-promotion removes some of the catalytic metal from the substrate while removing the protective metal, thereby making the substrate less active for metal deposition. Conversely, lack of promotion can result in poor adhesion or blistering of the metal to the substrate during the electroless plating process. In an attempt to overcome this control problem, new activators have been developed, such as in US Pat. No. 4,204,013 to Arcilesi et al., the accelerator bath contains an alkylamine containing certain amino acids. Some modifications of the promotion step have been found in the prior art, such as the post-activation step in Fadgen et al. US Pat. No. 3,767,583. In US Pat. No. 3,562,038 to Shipley et al., stripping for selective plating provides a modified acceleration stage. In Cohen et al., US Pat. No. 4,008,343, an acid wash is activated and used after a water wash. Considerable effort has been directed toward improving single-stage activator baths. In the disclosure of Schulze-Berge, US Pat. No. 4,001,470, tin is replaced with gum arabic and/or gelatin as the protective metal in the activator bath. The activator bath also contains at least one carboxylic acid and the acceleration step is eliminated. Other efforts have been made to address retaining and converting tin as a protective metal for the catalytic metal or the addition of the remainder of the activator bath. In US Pat. No. 4,182,784 to Krulik, a tin-palladium sol is used and no halides are present in the bath other than the tin-palladium salt. Here, a hydroxy-substituted organic acid is used in place of the excess halide to stabilize the bath. Acceleration in acids or bases is included in the cycle. In US Pat. No. 3,767,583 to Fadgen et al., the tin-palladium salt activator bath contains a "1-4C alkanol."
A post-activation or promotion step is included to ensure exposure of the catalytic precious metal on the surface or surfaces. U.S. Patent 3961109 to Kremer et al.
In this method, phenol or aromatic alcohol type compounds are used as additives to the activator bath. Includes promotion in fluoroboric acid.
In US Pat. No. 4,153,746 to Kilthau, EDTA is used as an additive at a specified low pH, although EDTA exhibits very little solubility at this low pH. Activation is followed by a stripping step. These additives have stability,
It is primarily directed toward either improving the efficiency and lifetime of the activator bath or providing better activation for electroless deposition. Also, in US Pat. No. 4,244,739 to Casnassi, the activator solution consists of an aliphatic sulfonic acid as at least a portion of the acid. However, the use of an acceleration step is also disclosed using fluoroboric acid. To the applicant's knowledge, no precious metal-protected metal activator bath of the palladium-tin type has been presented which can be used without acceleration in the plating process with consistently good results. Disclosure In accordance with the present invention, a composition is provided for activating a substrate for electroless metallization, comprising: a noble metal that catalyzes a chemical reduction plating process, the ability to form a protective metal sol in water; a salt forming a halide ion source and a protected metal sol in excess of that provided by the precious metal; and at least one organic acid substantially soluble in the plating bath and containing a fatty acid. carboxylic acids, aromatic carboxylic acids, amino acids, and combinations thereof. Although the present invention is preferably employed to electrolessly plate copper and nickel, most preferably copper, it can also be employed to activate substrates prior to plating gold, palladium, and cobalt. This invention also includes the use of the above-described activator sol in a comprehensive combination of steps to make up a complete chemical plating system, which combination not only requires fewer steps than conventional systems, but also is comparable or improved. It also gives results. Testing of the advanced invention has revealed many unexpected advantages, while presenting problems with the prior art, particularly when using copper-clad laminates as substrates. Some advantages of the present invention over the prior art have been found to be as follows: 1. The use of the activator of the present invention eliminates problems encountered in the prior art, such as blistering of metal on substrates and non-metallic substrates. Traditional accelerator steps and subsequent cleaning are eliminated, such as the slow start-up time in the electroless plating process and the poor copper-to-copper adhesion when using copper-clad laminates as substrates. There is no increase in hole wall pull-away in through-holes, which can be a major reason for rejected printed circuit boards. With the activator of this invention, several copper electroless plating baths were used without promotion and the results were good for all baths. Two steps are therefore eliminated from the prior art plating process, contributing to easier and cheaper operation. Another important advantage of eliminating the accelerating step is the elimination of accelerator baths and waste treatment steps for subsequent cleaning. This process is expensive, time consuming and harmful. For example, fluoroboric acid is typically used for promotion. The dissolved fluoride ions themselves are very corrosive and must be handled with great care. Protective clothing and eyewear must be worn during any handling of baths, including waste disposal. Waste treatment also includes slow and careful neutralization with a base to a pH of 7. This reaction is thermal and can be dangerous. Other accelerated baths may present similar waste disposal problems. 2. There is less copper build-up in the activator baths of this invention for copper-clad laminates as substrates than for prior art baths. The organic acid additive acts as a copper complexing agent for the copper removed from the laminate during activation. The baths of the present invention can therefore be used for longer periods of time between treatments due to the lower copper build-up, yet lend themselves to lower waste disposal and relatively inexpensive operation. 3. Lower precious metal concentrations are used in the practical activator baths of this invention compared to conventional baths, helping the baths to be less expensive to operate. 4 Although the preferred embodiment of this invention utilizes copper electroless plating baths commonly found in the manufacture of printed circuit boards and copper clad laminates as substrates, a variety of substrates and nickel electroless plating baths may be used in this manner. The activator bath of the invention was tested and good results were observed. 5 A common form of substrate used in the printed circuit industry is a combination of surfaces, generally plated copper, consisting of a composite of a copper clad laminate and a non-metallic part, such as a phenolic or epoxy. It is desirable for this type of board to electrolessly plate more copper on the non-metallic parts than on the copper cladding, as this is required primarily on the non-metallic through-holes. Using the activator baths and plating methods of the present invention, this is accomplished with superior results over prior art activator baths and plating methods. The activator baths used in the examples for comparison of the prior art are commonly used in electroless plating cycles that include various electroless metal baths following the promotion stage. These activator baths consist of palladium chloride, stannous chloride, sodium chloride, and/or hydrochloric acid without the organic acids of this invention. A variety of copper electroless plating baths were used to demonstrate the versatility of this invention. These baths are commercially available and include MacDermid Copper baths: Metex Electroless Copper
9048, Metex Copper
9027, MACuDep 20, and MACuDep 60, and has the following general technical uses: Metex Electroless Katsupa 9048 is a high speed bath that operates at approximately 130°C. Metex Katupa 9027 is a high speed room temperature bath. Mac Dep 60 is a medium temperature (approximately 100℃) high speed bath. Mac Dep 20 is a room temperature, slow bath. A high speed gives a thicker metal film than a low speed within the same amount of time. They are used depending on manufacturing requirements. These copper baths contain the main components of electroless copper baths: a solvent, usually water; a source of cupric ions; a source of hydroxide ions; a complexing or chelating agent to keep the copper dissolved; For example, EDTA;
and a reducing agent, such as formaldehyde.

[Brief explanation of drawings]

BRIEF DESCRIPTION OF THE DRAWINGS The invention will be better understood and its advantages will become apparent from the following detailed description, particularly when read from the examples and accompanying drawings. The figure is example 33
Figure 2 shows a graphical representation of the data obtained following the comparison.
Figure 2 shows the accumulation of copper in the activation bath as a function of time according to the present invention using organic acids and the prior art without organic acids. BEST MODE FOR CARRYING OUT THE INVENTION The activator bath prepared by D'ottavio in US Pat. No. 3,532,518 is a sol consisting of water, hydrochloric acid, stannous chloride, sodium stannate, and palladium. The preferred activator bath of this invention dilutes the sol with water before use and incorporates an organic acid selected from the group consisting of aliphatic carboxylic acids, aromatic carboxylic acids, amino acids, and combinations thereof. It is prepared by Preferred concentration range is about 0.0398 to about 0.1194g
m. /． of palladium and about 2 to about 6 g
m. /． contains stannous ions. However, feasibility is not limited to this range, but approximately 0.02 gm. /． Approximately 8 gm. /． of palladium and about 1 gm. /． Approximately 300g from
m. /． of stannous ions. Additional chloride salt and/or chloride acid is added. The preferred chloride normality of the activator baths of the present invention ranges from about 3.4 to about 4.6 normal. The chloride normality for feasibility ranges from 0.1N to saturation. The activator baths of this invention may contain one or more organic acids, such as tartaric acid, citric acid, maleic acid, malonic acid, glycolic acid, as shown in the examples.
and gluconic acid, with the preferred acids being tartaric acid and/or citric acid. Also effective are glutaric acid, glycine, and salicylic acid. The upper range of organic acids or acids is limited only by the saturation in the bath. It is clear that at saturation the results cannot be improved by additional organic acids. Any amount of organic acid added to the bath should be approximately 1 gm. /． From to saturation, improve results, but best results from about 10 to about 80g
m. /． Obtained with organic acids. If the amount of the specific organic acid used is less than 10 g, a satisfactory improvement effect cannot be obtained. In particular, if the promotion step is omitted, the activity against the substrate required to obtain sufficient plating cannot be obtained. On the other hand, when the amount exceeds 80 g/l, it does not bring about any particularly large disadvantages, but it does not increase the improvement effect, so it is not preferable from a cost standpoint. An advantageous embodiment of this invention is 10% by volume in water.
of hydrochloric acid, 7.5 gm/. of tartaric acid, and 3.0 g
m. /． Consists of citric acid. The bath is also about
0.0597gm. /． of palladium and approx.
m. /． of stannous ions. A chloride normality of approximately 3.6N is obtained by adding sodium chloride. The plating method of this invention comprises cleaning the non-conductive substrate with a suitable cleaning agent well known in the art followed by a suitable rinse solution. The substrate is then typically etched with a chemical etchant, some of which are commercially available for this purpose, to prepare the surface to accept the activated metal. If applicable, pickling solutions, neutralizers, and water rinses may be included before and after etching. The etched substrate is then contacted with the activator of the present invention for about 2 to about 5 minutes and an additional water rinse of about 3 minutes, although these times may vary somewhat. Activation may include a pre-soaking in a solution containing halide ions. The substrate is then chemically plated, although any number of electroless metal compositions and methods known in the art can be used. This can then be electrodeposited with copper or any other desired metal in a conventional manner, if desired. The method of this invention differs substantially from traditional prior art plating methods which typically require an acceleration step, usually in acid, after the activation step. A water rinse is also usually included after acceleration prior to electroless metallization. The organic acid-free prior art precious metal-protected metal (usually palladium-tin) activator bath of this invention is used in the prior art plating process in the comparison below. The following non-limiting examples illustrate the compositions and methods of this invention and some of the key advantages thereof: In the following examples, Metex 9267 is a surfactant-type, film-forming cleaning-conditioning agent. . Metex PTH Etch G-5 is a hydrogen peroxide/sulfuric acid type etchant. MACu Dep 60 is an electroless copper plating bath containing copper sulfate, formaldehyde, caustic soda and EDTA. Metex PTH Accelerator 9071 is essentially fluoroboric acid. Metex PTH Process Although not a composition, it is an electroless plating method that has become popular for through hole plating. This is essentially the same method as described in Example 1, except that the type of activator is different and that it includes an acceleration step. PTH activator (PTH)
Activator) 9070 is a sol consisting of water, hydrochloric acid, tin chloride, sodium stannate, and palladium, and is a sol consisting of water, hydrochloric acid, tin chloride, sodium stannate, and palladium, and is a
This is in accordance with No. 3532518. Metex Copper 9027 is an electroless copper bath containing the same key ingredients as Mak Dev 60. MACuplex 9340 Electroless Nickel is an electroless nickel bath containing nickel chloride, sodium hypophosphite, ammonium citrate, and ammonia. MacDermid L-56 is a chromic acid solution. Metex 9337 Neutralizer is hydrochloric acid and hydrazine. Further, the activator composition of the present invention was prepared as follows. 1 HCl and Sn ₂ Cl are heated and stirred in tank 1. 2. Mix and stir HCl and Pd ₂ Cl in tank 2. 3 Immediately add the mixture prepared in Tank 2 to Tank 1 and stir for 1 hour. 4. Cool the resulting solution. 5 0.75% by volume of the solution was added to 200% of the solution containing NaCl and an organic acid (e.g. citric acid, tartaric acid, etc.).
Mix with a solution of g/g. EXAMPLE 1 A special embodiment of the plating method of the invention consists of the following process cycle: 1 Penetration cleaning in MacDamide Metex 9267 detergent at 150° for 4 minutes. 2 and 3 Countercurrent rinse, 2 minutes each tank. 4. Pickling, sulfuric acid, 10% by volume, 70%, 2 minutes. 5 Rinse with water. 6 MacDamide Metex PTH Etch (PTH Etch) Etching with G-5,
110〓． 2 minutes. 7 Rinse with water. 8 Acid soak, sulfuric acid, 10% by volume, 70〓. , 2 minutes. 9 Rinse with water. 10 Activation with the activator of the invention in an advantageous embodiment thereof, 80〓. , 3 minutes. 11 Rinse with water for 2 minutes. 12 Electroless copper plating in MacDamid Mac Dep 60 copper bath. In its preferred embodiment, the activator bath of this invention has a dosage of 0.0597 gm. /． palladium, 3g
m. /． of stannous ion, 7.5 gm. /．
of tartaric acid, and 3.0 gm. /． of citric acid and was prepared for use in a 30-gallon tank. The chloride normality of the bath was kept at 3.5-4.5N.
The Metski cycle of this invention as described above was used. The control cycle for the prior art comparison was a commercially available prior art Metski cycle known as the MacDamide Metex PT. The control cycle included a commercially available activator bath, MacDamide Metex PT Activator 9070 (D'ottavio US Pat. Nos. 3,532,518 and 3,650,913). The board used was a copper-clad laminate production printed circuit board with through holes. Half of the boards were run through the inventive cycle and the other half were run through the control cycle that was used in production during this testing process. The times and temperatures were the same for both cycles, and the bath compositions were the same except for the activator and accelerator baths for the control cycle. Both sets of substrates were electrolessly plated in a commercially available copper bath, MacDamid MacDep 60. The copper coverage and copper-to-copper adhesion was found to be substantially the same for both sets of substrates. After electroless copper plating, the substrate was electroplated with copper and then electroplated with tin-lead. After melting the tin-lead coating by infrared methods, the through-holes were subjected to a solder impact test consisting of immersion in 550 solder for 10 seconds. Sections were taken and examined. The degree of pull-away of the hole walls was the same for both sets of substrates. No voiding was observed on either set of substrates. The number of rejected finished substrates was also substantially the same for both sets of substrates. The cycles and activator baths of this invention have shown comparable results to commercially available prior art activator baths and cycles, yet have the advantage of omitting the acceleration step and subsequent rinse. Example 2 (Prior Art Activator Bath - No Promotion) For comparison, an activator bath was prepared using the preferred concentrations of palladium, stannous ion, and chloride without the organic acid of this invention. The inventive plating process described in Example 1 was used in the prior art bath described above. A copper-clad board was used. Blistering of copper from the copper-clad substrate was observed after electroless deposition on all samples. Prior art activator baths that do not contain the organic acids of this invention give unsatisfactory results when used in the plating process of this invention. Examples 3-5 The activator baths of this invention were prepared in preferred embodiments with chloride normality of 3.4, 3.6, and 4.6. The inventive plating method described in Example 1 was used on copper-clad substrates. It was found that the copper-to-copper adhesion after copper deposition was good in all samples. Examples 6 to 13 The plating method of the present invention described in Example 1 is
was used for All boards were electrolessly plated in Metex Katsupa 9027. Macdamid Metex P.T.H.
Accelerator 907 was used for prior art comparisons (Examples 12 and 13). The Metsuki cycle used in Examples 12 and 13 is Macdamid Metex.
It was a P.T.H. Process. The amount of copper deposited on the substrate was measured in average microinches of copper coverage after electroless plating. For activator baths with preferred concentration ranges of palladium, stannous ions, and tartaric acid and the plating method of this invention, 16 to 18 Data show that microinches of copper are deposited. Data (Examples 12 and 13) show that using prior art activator baths and plating methods, 9 microinches more copper is deposited on epoxy than on copper-clad substrates for the same deposition time. When a printed circuit board with a composite of copper cladding and epoxy or non-metallic surfaces is used as a board, a relatively large difference is advantageous, since it is the epoxy that is important to be plated and the copper This is because it is not made of tension.

[Table] Example 14-18 0.0597gm. /． of palladium, 3 gm. /
．． An activator bath of the present invention was prepared consisting of stannous ions of 3.4N and a chloride normality of 3.4N.
The inventive plating method described in Example 1 was used.
An epoxy panel was used as the substrate. Various concentrations of tartaric acid were used in the activator bath. Metex Katupa 9027 was used for electroless deposition.
All substrates were held in the copper plating bath for 3 minutes.

Table: Examples 15-18 (invention) showed more copper deposited than example 14 (prior art), which did not have tartaric acid in the activator bath. No acceleration was used in the Metski cycle for all samples. At short plating times (3 minutes), more copper was deposited on the epoxy substrate when the activator bath of the present invention was used than when the prior art activator bath was used. Example 19-30 0.1194gm. /． of palladium and 6g
m. /． The following acids: tartaric acid, citric acid, maleic acid, malonic acid,
10gm of one of glycolic acid and gluconic acid. /
．． The activator baths of the present invention were prepared with a chloride normality of 3.6N for each bath containing: A copper clad substrate was subjected to the plating process of this invention as described in Example 1 using the activator bath described above. Two commercially available electroless copper baths, Metex Katupa
9027 and Matsuku Deb 20 were used. The board was tested for copper-to-copper adhesion after electroless plating. Good adhesion was found for all samples.
The organic acids selected for testing represented a range of aliphatic carboxylic acids, including hydroxy-substituted and non-hydroxy-substituted ones. The utility is not limited to the aims of this example, but clearly includes other aliphatic carboxylic acids. Example 31-32 0.1194gm. /． of palladium, 6 gm. /
．． of stannous ion, and 10 gm. /． An activator bath was prepared consisting of an aromatic carboxylic acid such as salicylic acid or an amino acid such as glycine. The normality of chloride was 3.6N. Example 19
The process involved these baths and the subsequent electroless deposition of copper. Example 33 (Copper Accumulation in Prior Art and Inventive Activator Baths) Two activator baths were prepared. Bath #1 (prior art) is a commercially available activator bath, 0.0597 gm. /
．． of palladium and 3.0 gm. /． Macactivate 10 is composed of stannous ions and has a chloride normality of 3.6N. Bath #2 (Invention) consists of the preferred embodiment of this invention and contains 0.0597g
m. /． of palladium and 3.0 gm. /．
consisting of stannous ions. The normality of chloride is
It is 3.6N. Bath #2 also contained 7.5 gm. /． of tartaric acid and 3.0 gm. /． of citric acid.
A series of copper-clad substrates were immersed in both baths for equal lengths of time. The accumulation of copper in ppm in the bath was determined by atomic absorption spectroscopy. Bath #2 (invention) showed much less copper accumulation than bath #1 (prior art). The accumulation of copper in the bath is shown in the accompanying figure. Example 34 (Prior Art - Palladium Concentration in Activator Bath) 7% MacDamide Metex PET Activator 9070 (D'ottavio U.S. Patents 3532518 and 3650913)
An activator bath was prepared consisting of: Analysis shows that the bath composition during use is 0.0597gm. /． of palladium and 3 gm. /． was shown to be a stannous ion. The normality of chloride was 4.6N. Copper-clad laminates are produced using the commercially available MacDamide Medtech Accelerator 9071, which differs from the plating method of the present invention by including an acceleration step in the Accelerator 9071. -Tietsuchi It was subjected to the metsuki process. Absorption data is 0.69 mg/cm2 on the substrate after activation. of palladium and 0.8
mg. / square cm. showed tin. After electroless copper plating, the substrate had a dark pink color and poor metal coverage, especially at the edges of the substrate. Example 35 (Invention - Palladium concentration in activator bath) This invention activator bath is an advantageous embodiment thereof,
0.0597gm. /． of palladium and 3g
m. /． tin, 3.6N chloride normality, 7.5g
m. /． of tartaric acid and 3.0 gm. /． of citric acid, prepared in A copper-clad laminate was subjected to the plating process of this invention. The bath is
0.0597gm. /． of palladium and 3g
m. /． Analysis has demonstrated that it contains stannous ions. Absorption data is 0.8 mg on the substrate after activation. / square cm. palladium and 2076
mg. / square cm. showed tin. Good copper coverage and no voids were found after electroless copper plating. Compared to the prior art activator baths used in prior art plating processes that include acceleration, the activator baths of the present invention can be used at relatively low practical concentrations of palladium using the plating process of the present invention without acceleration. Gives good results. EXAMPLE 36 A substrate consisting of an ABS plastic and epoxy panel was subjected to the activator bath and plating process of the present invention in its preferred embodiment. A commercially available nickel bath known as MACuplex 9340 Electroless Nickel was used for electroless plating.
The plating method used consisted of subjecting the substrate to the following steps: 1. Chrome etching with MacDamide L-56 at 155° for 5 minutes. 2. Rinse with cold water for 3 minutes. 3 Magdamid Metex 9337 Neutralizer, 2 minutes. 4 Rinse with cold water for 3 minutes. 5 Activate with the activator of the invention in its preferred embodiment at 80°C for 3 minutes. 6. Rinse with cold water for 3 minutes. 7 Electroless nickel, MACouples 9340 Electroless nickel, 80〓. , 5 minutes. Good nickel coverage and nickel adhesion to the substrate was observed after electroless deposition. The above description was provided to teach those skilled in the art how to practice the invention. It is not intended to describe in detail each and every obvious modification and modification thereto. however,
It is intended that all such modifications and changes be included within the scope of the invention as defined by the following claims.