JP5360527B2 - Pretreatment method for electroless plating on magnetic materials - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pretreatment method for a magnetic material, which imparts a stronger adhesion to a plated film which has been formed than a conventional pretreatment method such as a treatment of activating the surface with palladium, which is conducted for enhancing the adhesiveness of the plated film, when subjecting the magnetic material to electroless plating treatment. <P>SOLUTION: The pretreatment method prior to the electroless plating treatment for the magnetic material includes previously treating the magnetic material in an aqueous solution which contains a boron hydride compound and/or a derivative thereof and is adjusted to alkalinity of a pH of 9 or higher. This method is preferably employed when the magnetic material is ferrite. <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

Description

  The present invention relates to a pretreatment method for electroless plating on a magnetic material.

  Ferrite is a representative of magnetic materials and is a general term for ceramics mainly composed of iron oxide.

  In the case of electroless plating on a magnetic material such as ferrite, there is a problem that the adhesion of the plating film is low. In order to improve the adhesion of the plating film to the ferrite, a special pretreatment is required, and either a dry plating method or a palladium surface activation treatment method is generally used. For example, in Patent Document 1, dry plating is performed as a pretreatment for wet electrolytic plating. In Patent Document 2, electroless plating is performed after the palladium surface activation treatment.

  An electroless plating method using a dry plating method as a pretreatment is a method in which electroless plating is performed on a film having a thickness of about 1000 to 3000 mm formed by sputtering or the like. That is, it is a method that is performed in three steps: a film forming step for forming a film of about 1000 to 3000 mm, an activation treatment step for activating the formed film surface, and an electroless plating step.

  On the other hand, the palladium surface activation treatment method is a method of aiming at adhesion improvement, performing a catalyst treatment of palladium after etching with an acid, and forming an electroless plating film starting from this palladium catalyst. That is, first, an etching process for etching the surface of the magnetic material, a catalyst application process for applying palladium as a catalyst to the surface of the magnetic material, a catalyst activation process for activating the applied catalyst, and an electroless plating process. It is a method carried out in a process.

  Further, in Patent Document 3, after pretreatment of ferrite with a solution containing palladium halide, the ferrite is brought into contact with a plating solution made of an alkaline aqueous solution containing a conductive metal salt, a reducing agent and a boron hydroxide compound, so that the conductivity is provided on the ferrite. A method for producing a ferrite with a conductive metal film forming a metal film is disclosed.

JP-A-60-24382 JP 2005-194542 A JP-A 64-57799

  Both methods have complicated and multi-stage processes, and it is difficult to ensure sufficient plating adhesion after film formation.

  Further, in Patent Document 3, although a boron hydroxide compound is used, the boron hydroxide compound is not used for pretreatment, but only as a component of the plating solution. Although the effect of using a boron hydroxide compound as one component of the plating solution is described from the comparison between the example and the comparative example, nothing is disclosed about the function and mechanism of the boron hydroxide compound.

  In view of the situation as described above, the present invention provides a pretreatment method for a magnetic material capable of obtaining strong plating adhesion after film formation as compared with conventional pretreatment methods such as palladium surface activation treatment. is there.

That is, the pretreatment method of electroless plating on a magnetic material according to the present invention is characterized in that the magnetic material is treated with an aqueous solution comprising a borohydride compound and / or a derivative thereof, and a pH adjuster.
Furthermore, the present invention includes a method for electroless plating of a magnetic material. This electroless plating method includes the steps of (a) treating a magnetic material with an aqueous solution comprising a borohydride compound and / or derivative thereof , and a pH adjuster; and (b) treating the magnetic material treated in step (a). And a step of electroless plating in an undried state after washing with water.

  According to the pretreatment method of electroless plating of the present invention, since a direct plating reaction occurs with the magnetic material, adhesion is good and there is no reduction in the strength of the substrate due to etching. Further, since an expensive noble metal-based catalyst is not used, the cost of the direct material for the plating pretreatment can be reduced. In addition, according to the present invention, since the electroless plating can be performed in two steps of the borohydride compound or its derivative in an aqueous solution and the electroless plating step, the number of steps can be reduced.

  In the present invention, as a pretreatment for electroless plating, a magnetic material is treated with an aqueous solution of a borohydride compound and / or a derivative thereof.

  Examples of the borohydride compounds include sodium borohydride, potassium borohydride, lithium borohydride, and the like. Derivatives of the borohydride compounds include alkylamine boranes such as dimethylamine borane and trimethylamine borane. Can be mentioned. The borohydride compound or derivative thereof may be a single compound or a mixture of a plurality of compounds.

  Ferrite is preferably used as the magnetic material to be electrolessly plated, and the pretreatment method of the present invention is suitable when ferrite is used as the magnetic material.

  In the present invention, the pretreatment method for the magnetic material is immersion in the aqueous solution in which the concentration and temperature are set. This aqueous solution may be an aqueous solution of the above-described borohydride compound, an aqueous solution of a derivative of a borohydride compound, or an aqueous solution of a mixture of both. When a magnetic material such as ferrite is immersed in an aqueous solution of a borohydride compound and / or derivative thereof, a reduction reaction proceeds on the surface of the magnetic material by the borohydride compound and / or derivative thereof, and one surface of iron oxide is obtained. Part is reduced to metallic iron or converted to boride. In this reaction process, hydrogen gas is generated.

  This metallic iron or boride is the reaction starting point for electroless plating.

  The concentration of the aqueous solution used for the pretreatment is not particularly limited as long as it causes a reduction reaction, and the minimum concentration is the lowest concentration at which a reduction reaction is possible, and is adjusted by temperature, time, and throughput. . The upper limit of the concentration is an upper limit where the borohydride compound and / or derivative is soluble in water as a solvent.

  The pretreatment temperature can be used from room temperature to the boiling point, but is preferably in the temperature range of 50 to 80 ° C.

  The aqueous solution is preferably used by adjusting the pH to 9 or higher. When PH is less than 9, self-decomposition becomes extremely large, resulting in poor reaction activity. For the adjustment of this aqueous solution, an alkali metal hydroxide such as sodium hydroxide is preferably used.

  The immersion time varies depending on the chemicals used, the temperature, and the concentration, but is generally preferably in the range of 1 to 180 minutes.

  After immersion, after washing with water, it may be brought into an electroless plating bath in an undried state. By bringing it into the electroless plating bath, the electroless plating reaction starts from the reduced metallic iron or boride, and a predetermined plating film can be formed.

  Any metal compound, reducing agent, plating conditions, etc. for forming a film by electroless plating can be used as long as they are used in normal electroless plating.

  The present invention will be further described below using examples.

<Example 1>
A magnetic material made of ferrite was immersed in an aqueous solution of sodium borohydride at pH = 10, a concentration of 40 g / L, and a temperature of 60 ° C. for 2 hours, and then subjected to electroless Cu plating. The adhesion after film formation was measured by a 2 mm width peel test. The results are shown in Table 1.

<Example 2>
A magnetic material made of ferrite was immersed in an aqueous dimethylamine borane solution having a pH of 11, a concentration of 30 g / L, and a temperature of 70 ° C. for 2 hours, and then subjected to electroless Cu plating. The adhesion after film formation was measured by a 2 mm width peel test. The results are shown in Table 1.

<Comparative Example 1>
A Cr film was formed on the surface of the magnetic material made of ferrite by sputtering for 2.5 hours to form a 3000 mm film. Next, after immersing in a 10% sulfuric acid aqueous solution for 0.5 hours to perform activation treatment on the surface, electroless Cu plating was performed. The adhesion after film formation was measured by a 2 mm width peel test. The results are shown in Table 1. The total pretreatment time required for the Cr film formation and activation treatment is 3 hours.

<Comparative Examples 2-5>
After the etching treatment for providing irregularities on the surface of the magnetic material made of ferrite, the electroless Cu plating was performed after the application of the palladium catalyst as the starting point of the plating reaction and the activation treatment of the catalyst. Etching was performed using about 5% hydrofluoric acid aqueous solution. Etching is an important process to ensure adhesion, and the adhesion force varies depending on the processing time. Therefore, Comparative Example 2 is 14 hours, Comparative Example 3 is 23 hours, Comparative Example 4 is 72 hours, and Comparative Example 5 is 105 hours. Etching was performed over time. In any of the comparative examples, it took 0.5 hour for the application of the palladium catalyst after the etching treatment and 0.5 hour for the catalyst activation treatment. The adhesion after film formation by electroless Cu plating was measured by a 2 mm width peel test. The results are shown in Table 1.

  As is apparent from Table 1, the dry plating pretreatment method shown in Comparative Example 1 takes 3 hours for the pretreatment, and the pretreatment methods for etching and palladium activation shown in Comparative Examples 2 to 5 take 15 hours or more. Moreover, the adhesion of the film formed by electroless Cu plating was 0.037 N (3.8 gf) after 14 hours of hydrofluoric acid etching, and 0.314 N (32.0 gf) after 105 hours of hydrofluoric acid etching. 2 is inferior to the adhesion of the electroless Cu plating film obtained in 2.

  That is, according to the pretreatment method of the present invention, it can be seen that firm adhesion can be obtained in a shorter time than the conventional pretreatment method.

<Comparative Example 1>
A pretreatment is performed in which a magnetic material made of ferrite is immersed in an aqueous solution of sodium borohydride at pH = 10, a concentration of 5 to 50 g / L, and a temperature of 20 to 70 ° C. for 0.5 to 3 hours, and then electroless Cu plating is applied. did. The adhesion of the plated film after film formation was measured by a 2 mm width peel test.

  FIG. 1 shows changes in the adhesion of the plating film when the immersion time is fixed at 2 hours and the concentration and temperature of the sodium borohydride aqueous solution are changed.

  Further, when the sodium borohydride concentration is 5 g / L and the temperature is 60 ° C., the sodium borohydride concentration is 20 g / L and the temperature is 20 ° C., and the sodium borohydride concentration is 40 g / L and the temperature is 50 ° C. FIG. 2 shows changes in the adhesion of the plating film when the processing time is changed.

  From FIG. 1, it is possible to ensure an adhesive strength equal to or higher than that of the dry plating pretreatment method shown in Comparative Example 1 in the immersion treatment at a sodium borohydride concentration of 30 to 50 g / L, a temperature of 60 to 70 ° C., and 2 hours. I understand. On the other hand, it can be seen that sufficient adhesion cannot be obtained at a low concentration of less than 30 g / L as shown in FIGS. 1 and 2 or at a treatment time of less than 2 hr as shown in FIG.

<Comparative Example 2>
A pretreatment of immersing a magnetic material made of ferrite in a dimethylamine borane aqueous solution having a pH = 11, a concentration of 10 to 30 g / L, and a temperature of 50 to 70 ° C. for 0.5 to 2 hours, followed by electroless Cu plating . The adhesion of the plated film after film formation was measured by a 2 mm width peel test.

  FIG. 3 shows changes in the adhesion of the plating film when the concentration of the aqueous dimethylamine borane solution is fixed at 10 g / L and the aqueous solution temperature and the immersion time are changed.

  FIG. 4 shows the change in adhesion of the plating film when the concentration of the aqueous dimethylamine borane solution is fixed at 20 g / L and the aqueous solution temperature and immersion time are changed. The concentration of the aqueous dimethylamine borane solution is 30 g / L. FIG. 5 shows the change in the adhesion of the plating film when the aqueous solution temperature and the immersion time are changed.

  As shown in FIGS. 3 to 5, dimethylamine borane also changed its adhesion with the magnetic material depending on the concentration, temperature, and treatment time, similar to sodium borohydride in Comparative Example 1.

  In order to obtain an adhesion strength of 0.294 N (30 gf) similar to that of conventional dry plating (sputtering), a concentration of 10 g / L is 70 ° C. or more and a treatment time is 1 hour or more, or 20 to 30 g / L is 60 It can be seen from FIGS.

It is a figure which shows the change of the adhesive force of a plating film when fixing immersion time to 2 hours and changing the density | concentration and temperature of sodium borohydride aqueous solution. Immersion treatment time for sodium borohydride concentration 5 g / L, temperature 60 ° C., sodium borohydride concentration 20 g / L, temperature 20 ° C., and sodium borohydride concentration 40 g / L, temperature 50 ° C. It is a figure which shows the change of the adhesive force of the plating film when changing this. It is a figure which shows the change of the adhesive force of a plating film when the density | concentration of dimethylamine borane aqueous solution is fixed to 10 g / L, and aqueous solution temperature and immersion time are changed. It is a figure which shows the change of the adhesive force of a plating film when the density | concentration of dimethylamine borane aqueous solution is fixed to 20 g / L, and aqueous solution temperature and immersion time are changed. It is a figure which shows the change of the adhesive force of a plating film when the density | concentration of dimethylamine borane aqueous solution is fixed to 30 g / L, and aqueous solution temperature and immersion time are changed.

Claims (4)

  A pretreatment method for electroless plating on a magnetic material, characterized by treating the magnetic material with an aqueous solution comprising a borohydride compound and / or a derivative thereof, and a pH adjuster.   2. The pretreatment method for electroless plating on a magnetic material according to claim 1, wherein the aqueous solution is prepared by adjusting the pH to an alkalinity of 9 or more.   The pretreatment method for electroless plating on a magnetic material according to claim 1 or 2, wherein the magnetic material is ferrite. (A) treating the magnetic material with an aqueous solution comprising a borohydride compound and / or derivative thereof , and a pH adjuster ;
(B) A method of electroless plating of a magnetic material, comprising the step of electroless plating the magnetic material treated in step (a) after washing with water and in an undried state.

Images