JPH04187777A - Electroless plating method - Google Patents

Abstract

PURPOSE:To unnecessitate treatment with a solvent and etching and to increase plating speed by treating synthetic fibers with a dil. acid and a dil. alkali at a high temp. and carrying out activation at a prescribed temp. CONSTITUTION:Synthetic fibers or a plastic product is treated with a dil. acid or a dil. alkali in arbitrary order at such a high temp. as the softening point of the material to be plated or below. A sensitizing soln. contg. 0.1-20g/l stannous chloride dihydrate and an activating soln. contg. 0.01-0.4g/l palladium chloride dihydrate are prepd. After treatment with the solns. at 60 deg.C to the softening point, electroless plating is carried out.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention achieves process simplification and stability by performing sensitization treatment and activation treatment at high temperatures when performing electroless plating on synthetic fibers or plastics. This invention relates to a new electroless plating method for obtaining excellent plating.

[Prior Art] Electroless plating is a method of plating by simply immersing an object to be plated in a plating bath.

The characteristics of electroless plating are (1) It is possible to plate non-conductive materials such as plastics and ceramics other than metals by performing sensitization treatment and activation treatment;
(2) Even objects with complex shapes can be plated to a uniform thickness; (3) a plated film with fewer pinholes can be obtained, resulting in a film with better corrosion resistance than electroplating; (4)
) It is possible to produce plating films with unique functionality (magnetism, amorphous, etc.); (5) Although it has advantages such as easy equipment and operation, the fil plating speed is slow; (2)
) There are problems such as short life of the plating bath and (3) higher cost than electroplating.

In conventional electroless plating methods, the composition of the pretreatment process varies depending on the material to be plated, but when plating plastic etc., an alkaline solution (NaO820-30
g/f2. Na2CO320-30g/ff, Na3P
O420~30g/ρ, surfactant) or degreasing step by immersion in organic solvent, xylene, dioxane, toluene,
Solvent treatment process using tetralin, dimethinoformamide, dimethyl sulfoxide, CrO3-H2S04-H20 solution (CrO, 1
00~500g/12) or an etching process of immersing it in a solution containing 83PO4 at high temperature, then S
nC1.・2H202 0 ~ 40 g / 12,
A sensitization step in which Sn" is adsorbed by immersion in a sensitization treatment solution of HCI"c 10 to 20 mj2/I2, and this Sn"
As a result, the pretreatment process for the electroless plating process is completed through an activation process in which Pd0 is precipitated on the surface of the material to be plated by the reaction of Pd''.

In this case, the sensitization process and activation process are immersed in the sensitization treatment solution and activation treatment solution for 1 to 2 minutes at a low temperature of room temperature (around 20℃), but after each treatment is completed, before moving on to the next process. Washing with plenty of water is required. Furthermore, since these treatments completely destroy the plating, they are rarely done just once, but are usually repeated multiple times.

The material to be plated that has undergone such pretreatment is then plated, usually by dipping, in a plating bath consisting of a metal salt containing the metal to be plated, a complexing agent, and a reducing agent. The metals used for plating are mainly nickel, copper, cobalt, and noble metals such as gold, silver, and indium.

Below, nickel will be taken as a representative example and explained.

Many bath compositions have been announced as practical nickel plating baths, including acidic baths, neutral baths, and alkaline baths.

Several reducing agents have been announced for use in this process, but sodium hypophosphite and boron compounds are often used. It is widely used because it has excellent mechanical properties such as elasticity.

However, as mentioned above, the electroless plating method itself has slow plating speed, high cost, short plating bath life, and contains many impurities such as reducing agents and complexing agents, making it difficult to recycle. However, there are several problems, such as the high concentration of effective metal salts contained in plating wastewater, which makes wastewater treatment difficult.

[Problems to be Solved by the Invention] The present invention has been achieved through studies aimed at reducing costs, simplifying wastewater treatment, and simplifying processes, which are unresolved problems of conventional electroless plating methods. did. .

[Means for Solving the Problems] The present invention provides, in the pretreatment of the electroless plating method for synthetic mta or plus deck products, at least the degreasing step with a dilute acid and then with a dilute alkali to a temperature below the softening point of the material to be plated. 5 relating to an electroless plating method characterized in that treatment is carried out at a high temperature, followed by sensitization treatment and activation treatment at a temperature between 40° C. and the softening point.Synthetic fibers or plastic products that are the subject of the present invention include: Synthetic fibers such as polyamide (nylon), polyester, and acrylic fibers, polyethylene, polypropylene,
Acrylonitrile-butadiene-styrene resin (ABS
), styrene, vinyl chloride, and so-called engineering plastics such as polycarbonate, polyamide, polybutyl terreclate, and polyacetal.

Regarding the shape of the product, it is possible to plate objects with a uniform thickness even on objects with complex shapes, which is a feature of electroless plating.
Since there is no need to connect the material to be plated to the electrode,
It can also be used for fibers, powders, and other products in various shapes. In particular, it is preferable to apply it to fibrous products because it has a large surface area per weight, so it can enjoy the advantage of omitting processes that require the use of large amounts of washing water in processes such as solvent treatment and etching treatment. .

The pretreatment for electroless plating in the method of the present invention requires at least three steps: a degreasing step, a sensitization step, and an activation step, and the solvent treatment required for electroless plating of plastic products in the conventional method. It has the feature that the etching process can be omitted.

Although the solvent treatment process requires the use of large amounts of organic solvents that can cause environmental pollution, ignition, and explosions, omitting this process not only reduces costs but also means that the above problems can be avoided. .

In addition, the etching process is recognized as a pretreatment process for plastic materials to roughen the surface to be plated and improve the adhesion of the plating film.
An SOa-based etching bath is used. However, this Raku contains highly toxic hexavalent chromium ions, and if it is washed with water after this treatment, a large amount of dilute hexavalent chromium wastewater will be generated, which will increase the cost of this post-treatment and reduce the overall cost. Therefore, omitting this step has great effects such as simplifying wastewater treatment and shortening the process.

Of course, even if these solvent treatment steps and etching steps are added, the method of the present invention can be implemented without losing the advantage of omitting the above steps.

The degreasing step as the first pre-treatment step of the present invention may be a conventional process such as immersion in an alkaline solution at room temperature alone or immersion in an organic hot medium, but it may also be carried out using a dilute aqueous solution of a strong acid, such as hydrochloric acid,
Treat with a 05-10% solution of sulfuric acid, nitric acid, sulfonic acid, etc. at a temperature of at least 50°C or higher, close to the temperature at which the material to be plated softens, for about 3-10 minutes, and then treat with a dilute alkali solution. A strong alkaline aqueous solution such as (concentration is 0.
5% to 5%) solution under almost the same conditions as the strong acid aqueous solution treatment.

Note that the order of acidic treatment and alkaline treatment may be arbitrary.

This treated product is thoroughly washed with water and subjected to sensitization treatment.

As a sensitization treatment solution, 0 as 5nC1□・2H20
．． 1-20 g / 12 hydrochloric acid acidic aqueous solution (HCl
1-20m as conc! ! , /2).

When the concentration of SnCl□・2H,O is extremely diluted,
Although it is possible to perform plating by using a sufficient amount of liquid and taking a sufficient amount of time, it is economically unfavorable because it requires a large amount of solution and a long time.

Moreover, even if it exceeds 20 g/l, the effect is saturated and there is no merit. The treatment temperature is 40° C. or higher and the temperature is lower than the softening point of the material to be plated for about 3 to 10 minutes. It goes without saying that this time is required for a long time when the processing temperature is low, and this time should be seen as a rough guide.

The activation treatment liquid was PdC1□-2H20 with 0.
Hydrochloric acid acidic aqueous solution (HCl ”c
1 to 20+nI2/, 9). pac
Even if the concentration of tz.2H20 is extremely dilute, it is possible to perform plating by taking a sufficient amount of liquid and time, but economically, the above concentration range is preferable. Even if the concentration is 0.4 g/i or more, many Pd ions remain in the activated liquid, which increases the concentration in the final waste liquid that has lost its life due to circulation use (and only adds load to the waste water treatment). There's not much benefit.

At this time, the treatment temperature is 40° C. or higher, and the treatment is performed at a temperature lower than the softening point of the material to be plated for about 3 to 10 minutes.

Sufficient water washing is required when transferring between these steps, and it is necessary to strictly avoid transferring the treatment liquid from the previous step to the next step.

The material to be plated that has undergone the pretreatment process in this way is thoroughly washed with water and sent to an electroless plating process to coat various metals such as Au, Ag, Pd, and Cu.

Plate with metal such as Ni, Co, Fe, Ir, etc.

Products pretreated by the electroless plating method of the present invention can be subjected to electroless plating in the same manner as products pretreated by conventional methods.

[Function] The pretreatment process of the electroless plating method in the present invention includes a degreasing process, a sensitization process, and an activation process, all of which are performed at a considerably higher temperature than the treatment temperature in the conventional pretreatment process.
It is required to carry out the process at a temperature of 40°C to the softening point.

For this reason, the surface of the product to be plated is made rougher than in the pretreatment process of the conventional method, and therefore good results may be obtained without the need for solvent treatment or etching treatment.

In addition, when the pretreatment of the present invention is performed, one sensitization treatment and activation treatment is sufficient, perhaps because of the high temperature treatment, but this step may be performed multiple times depending on the case. This method is far superior to conventional methods that may be required.

Although the reason was not clear, the pretreatment of the present invention can increase the plating speed, which is the biggest drawback of electroless plating methods, and also increases the adhesion strength of the plating film. product is obtained.

Hereinafter, the present invention will be specifically explained with reference to Examples.

[Example] Acrylic fibers having a fineness of 2 denier and cut into a length of 10 mm were used as the material to be plated.

The water used was tap water.

The degreasing process uses a 1% HCI aqueous solution as the first step,
After being treated at 80°C for 5 minutes, it was washed with water. In the second stage, a 1% aqueous solution of sodium hydroxide was used, and after being treated at 80°C for 5 minutes, it was thoroughly washed with water.

Sensitization treatment is with reagent grade SnC1□2H.

O was diluted with water to 10 g/E and concentrated hydrochloric acid 1 mρ/ρ to obtain a sensitized solution. This treatment liquid 3.000m
Add 50g of pretreated acrylic fiber (weight before degreasing) to
80° C.) for 5 minutes, thoroughly washed with water, and sent to the activation treatment step.

Activation treatment is performed using reagent grade PdCl□・2H200, 1g
/I2 and concentrated hydrochloric acid were diluted with water to 1 m 9 /9 to obtain an activation treatment solution. This treatment solution 3゜000mI
2, 50 g (weight before degreasing) of sensitized acrylic fiber was added, treated at a predetermined temperature (same temperature as the sensitization) for 5 minutes, and thoroughly washed with water.

The steps of sensitization treatment, water washing, activation treatment, and water washing were defined as one cycle, and 1 to 3 cycles were performed to form a pretreatment step.

<Test of stability of plating film> The above pretreated material to be plated (acrylic fiber) is Nickel sulfate 30g/l Sodium acetate 10g/j2 Potassium hypophosphite lOg/l2 An electroless plating bath with pH 6 was prepared.

To 3000 cc of the above plating bath, 50 g of acrylic fiber (weight before degreasing) as the material to be plated was added at 95°C.
, soak for 5 minutes, perform electroless plating, rinse thoroughly with water,
It was dried to obtain a plated product.

This plated product was heated to 80°C for 6 hours, then to -20°C for 1 hour.
After repeating heating and cooling for 5 cycles (one cycle is holding for 8 hours), this product is stirred and suspended in water.
The peeling status of the plating was observed.

The results are shown in Table 1.

Table 1 X: A large amount of precipitate was observed, and the fibers were also observed to be discolored.

Δ: Slight precipitation was observed. The color of the fibers does not change.

○: No precipitate observed.

(Plating speed) The plating bath is initially opaque at a nickel concentration of 15 g/l, but after sufficient plating, the bath becomes transparent with a nickel concentration of 0.4 g/P. Table 2 shows the relationship between the time required to achieve transparency in this case and the sensitization and activation cycles of the pretreatment and the treatment temperature. The plating conditions were the same as those for the stability test of the plating film.

As shown in Table 2, by increasing the sensitization and activation treatment temperature, the plating speed is low, which is one of the biggest drawbacks of electroless plating, even if the plating conditions are the same. It was confirmed that the process could be significantly accelerated by changing the . This effect is particularly significant when processing at a high temperature of 60° C. or higher.

[Effects of the Invention] When the method of the present invention is adopted as a pretreatment for electroless plating, the solvent treatment and etching steps can be omitted, and in particular, the use of hexavalent chromium used in the etching process can be avoided, making it easier to treat plating wastewater. The load can be greatly reduced.

In the method of the present invention, the processing liquid used is different from that in the conventional method.
In general, the fact that the concentration is low also leads to less washing water and wastewater treatment. In addition to omitting steps, this greatly contributes to cost reduction.

Furthermore, perhaps due to the high temperature treatment, a sufficient pretreatment effect can be obtained with just one sensitization treatment and activation treatment, leading to a reduction in the amount of wastewater and the number of steps.

Furthermore, for reasons that are unclear, high-temperature pretreatment can significantly increase the plating speed and shorten the required time, which is a disadvantage of electroless plating. It was also found that the adhesion strength was excellent in the test, and that a good plating film could be obtained.

As described above, it has been revealed that by performing the pretreatment according to the method of the present invention, the process is simplified, the amount of waste water is reduced, and costs can be reduced, and the resulting plating film also exhibits good adhesion strength.

Claims (3)

[Claims] (1) In the pretreatment of the electroless plating method for synthetic fibers or plastic products, at least the degreasing step is performed using dilute acid.
Next, it is treated with dilute alkali at a high temperature below the softening point of the material to be plated, and then sensitized and activated for 40 minutes.
An electroless plating method characterized by being carried out at a temperature between °C and the softening point. (2) Add 0.1 stannous chloride dihydrate as the sensitization treatment solution.
20 g/l, and the electroless plating method according to claim 1, wherein a solution containing palladium chloride dihydrate in the range of 0.01 to 0.4 g/l is used as the activation treatment liquid. (3) The electroless plating method according to claim 1, in which solvent treatment and etching steps are omitted as pretreatment.