JP4228392B2 - Plating method and electronic component manufacturing method - Google Patents

Description

  The present invention relates to a plating method and an electronic component manufacturing method, and more specifically, a plating method for forming a metal film on the surface of an object to be plated, and an electronic component such as a multilayer ceramic capacitor obtained by using this plating method It relates to the manufacturing method.

  In electronic parts such as multilayer ceramic capacitors, Ni film is usually formed on the surface of external electrodes mainly composed of Ag, Cu, etc. to prevent solder erosion, and solder wettability is improved and Ni film is oxidized. In order to prevent this, a Sn film or a Sn-Pb film is formed on the surface of the Ni film.

  As this type of plating bath, Sn and Sn—Pb alloy plating solutions containing a stannous salt, a complexing agent such as gluconic acid, and a surfactant have been known (Patent Document 1). ).

In Patent Document 1, by adding a complexing agent to the Sn or Sn-Pb alloy plating solution, Sn ²⁺ forms a stable soluble complex with the complexing agent to improve the stability of the plating bath. .

  Further, when producing a ceramic electronic component such as a multilayer ceramic capacitor using the plating bath, the hydrogen ion exponent pH (hereinafter simply referred to as “pH”) is controlled to 2 to 10, preferably 3 to 7. Accordingly, it is possible to reduce the melting of the ceramic material and the glass component contained in the ceramic body, and it is possible to suppress the quality deterioration of the ceramic electronic component.

JP 57-63689 A

  However, in the above-mentioned Patent Document 1, a pH adjusting agent is added to the plating bath to directly adjust the pH of the plating bath to a desired value suitable for the plating treatment. , “Initial bath”) and plating bath after continuous use (hereinafter referred to as “continuous use bath”) have a drawback that the properties of the plating bath change. For this reason, when electrolytic barrel plating was performed on the object to be plated, the film thickness of the plating film varied between the initial bath and the continuous use bath.

  That is, in electrolytic barrel plating that is frequently used for plating of ceramic electronic parts, usually, an object to be plated and a conductive medium are immersed in a barrel container and energized between an anode and a cathode, thereby performing an electrolytic plating process. Since the conductive medium is generally made of a metal member such as a steel ball, the current density is high, and the current density is low around the object to be plated mainly composed of a ceramic material.

On the other hand, in the case of a plating bath containing a metal salt and a complexing agent, in the initial bath, an anion in the metal salt (for example, SO ₄ ^{2− in} the case of tin sulfate (SnSO ₄ ), tin chloride (SnCl ₂ )) . In this case, the influence of Cl ⁻ ) is large, and since these anions are present around Sn ²⁺ (metal ions) , Sn ²⁺ cannot form a stable complex with the complexing agent.

Thus, in the initial bath, Sn ²⁺ in the metal salt cannot form a stable complex with the complexing agent, so that Sn is likely to precipitate in a conductive medium having a high current density, and the current density is low. Sn becomes difficult to deposit on the plated product.

  That is, the conventional Sn plating bath as described in Patent Document 1 cannot form a stable complex in the initial bath, so that only a thin Sn film can be formed. In order to obtain an Sn film having the same film thickness as that described above, it is necessary to set the current density high or to increase the plating processing time.

On the other hand, in the continuous use bath, Sn ²⁺ eluted from the anode by electrolytic treatment is coordinated with the complexing agent to form a stable complex. As the complex stabilizes in this way, the plated metal easily deposits not only on the conductive medium having a high current density but also on the object to be plated having a low current density, thereby obtaining a thick Sn film. it can.

  However, when the current density is increased or the plating process time is increased in the continuous use bath, a thick Sn film exceeding the desired film thickness is formed.

  And when the Sn film having a thickness exceeding the desired film thickness is formed in this way, since the hardness of Sn is low, the objects to be plated adhere to each other through the Sn film having such a low hardness. Yield decreases.

  As described above, in the conventional Sn plating bath, the stability of the complex is different between the initial bath and the continuous use bath. Therefore, it is not possible to form a plating film having the same film thickness under the same plating conditions. In order to obtain a plating film, it is necessary to increase the current density or lengthen the plating time in the initial bath, while in the continuous use bath, the current density can be increased or the plating can be performed from the viewpoint of preventing adhesion between electronic components. It is necessary to avoid an increase in processing time.

  That is, in the conventional Sn plating bath, in order to obtain the same film thickness in the initial bath and the continuous use bath, the plating conditions have to be changed. Therefore, the productivity is poor and the high quality with high reliability. There was a problem that it was difficult to obtain electronic parts with high efficiency.

  The present invention has been made in view of such problems, and a plating method capable of easily obtaining a plating film having substantially the same film thickness even when continuously used, and an electronic component using this plating method It aims at providing the manufacturing method of.

The inventors of the present invention have made extensive studies to achieve the above object, and after preparing a plating bath using a specific complexing agent capable of forming a complex with a metal ion, an object to be plated The complex is stabilized even in the initial bath stage by performing electrolytic treatment in a state where the material is not yet immersed in the plating bath, and performing electrolytic plating by immersing the object to be plated in the electrolytic bath. I got the knowledge that I can.

The present invention has been made on the basis of such knowledge, and the plating method according to the present invention includes a metal ion of a plating metal forming a plating film and a complex capable of forming a complex between the metal ion. A plating method for performing electroplating using a plating bath containing an agent , wherein the complexing agent is a polycarboxylic acid, a polyoxymonocarboxylic acid, an aminocarboxylic acid, a lactone compound, or a salt thereof. together containing at least one selected from the anode to supply the metal ions of the plating metal was immersed and a cathode to the plating bath, the anode in a state of not being immersed object to be plated within the plating bath And a first electrolytic treatment step for conducting an electrolytic treatment by energizing between the cathodes, and after the first electrolytic treatment step, the object to be plated is immersed in the plating bath and passed between the anode and the cathode. It is characterized in that it comprises a second electrolytic treatment step of performing electrolytic treatment by.

  According to the plating method, since the electrolytic treatment is performed without immersing the object to be plated in the plating bath in the first electrolytic treatment step, the metal ions dissolved from the anode are coordinated to the complexing agent and complexed. Is stabilized.

  In the present invention, the “material to be plated” refers to an article to be plated, such as an electronic component, and is inevitably deposited with a plating film because it has been mixed in the plating bath for the convenience of plating treatment. Articles to be processed, for example, conductive media such as steel balls, are not included.

  Further, when the present inventors further advanced research, the complex is surely obtained by replacing 50% or more of metal ions in the plating bath with metal ions dissolved from the anode in the first electrolytic treatment step. It turns out that it becomes a stable state.

  That is, the plating method of the present invention is characterized in that, in the first electrolytic treatment step, 50% or more of metal ions contained in the plating bath are replaced with metal ions supplied from the anode. .

  In addition, when performing electrolytic barrel plating, it is preferable to mix a conductive medium with the object to be plated in order to ensure conduction between the cathode and the object to be plated.

  That is, in the plating method of the present invention, in the second electrolytic treatment step, a current is passed between the anode and the cathode while a conductive medium formed of a material different from the object to be plated is immersed in the plating bath. Thus, the electrolytic treatment is performed.

  Furthermore, when performing the said electrolytic barrel plating, it is preferable to mix and carry out a nonelectroconductive medium in a to-be-plated object from a viewpoint of avoiding the overlap of to-be-plated objects.

  That is, in the second electrolytic treatment step, the non-conductive medium formed of a material different from the object to be plated is immersed in the plating bath, and the electrolytic treatment is performed by energizing the anode and the cathode. It is characterized by that.

  Furthermore, the plating method of the present invention is characterized in that the plating metal contains tin as a main component, and the hydrogen ion exponent pH of the plating bath is adjusted to 3 to 10.

  The electronic component manufacturing method according to the present invention is an electronic component manufacturing method for manufacturing an electronic component by performing a plating process on an object to be plated on which a conductive portion is formed on the surface of the component element body, A metal film is formed on the surface of the conductive portion using a plating method.

According to the above plating method, the metal ions dissolved from the anode are subjected to the specific complexing agent (specifically, by performing the electrolytic treatment without immersing the object to be plated in the plating bath in the first electrolytic treatment step). , At least one selected from polycarboxylic acid, polyoxymonocarboxylic acid, aminocarboxylic acid, lactone compound, and salts thereof) to stabilize the complex. And then, since the object to be plated is plated in the second electrolytic treatment step, the electrolytic plating treatment is performed under stable complex formation from the initial bath stage, and therefore the plating conditions are changed. Accordingly, it is possible to easily obtain a plating film having substantially the same film thickness in both the initial bath and the continuous use bath.

  Further, in the first electrolytic treatment step, by replacing 50% or more of the metal ions contained in the plating bath with metal ions supplied from the anode, the complex is reliably stabilized, and the initial bath It is possible to easily obtain a plating film having substantially the same film thickness in both the continuous use bath and the continuous use bath.

  Further, by conducting electroplating by immersing a conductive medium and a non-conductive medium in a plating bath, it is possible to ensure conduction between the cathode and the object to be plated while preventing the objects to be plated from overlapping each other. This makes it possible to easily form a desired plating film on the surface of the object to be plated.

  Further, by setting the pH of the plating bath to 3 to 10, the plating bath can maintain weak acidity to weak alkalinity, and even if the object to be plated is mainly composed of a ceramic material or a glass agent, It is possible to avoid the dissolution of the plated product component as much as possible.

  Furthermore, according to the manufacturing method of the electronic component, since the metal film is formed on the surface of the conductive part using the plating method, the plating conditions are substantially the same without changing the plating conditions in the initial bath and the continuous use bath. A metal film having a film thickness can be formed on the conductive portion, and a high-quality electronic component having excellent reliability can be manufactured with high efficiency.

  Next, a tin plating method as the best mode of the plating method of the present invention will be described in detail.

  First, a tin plating bath containing a stannous salt as a metal salt and a complexing agent is prepared.

  Here, as the stannous salt, stannous sulfate, stannous chloride, stannous sulfamate, or the like can be used.

  As the complexing agent, an organic acid that forms a stable soluble complex in the Sn plating bath can be used. Specifically, polycarboxylic acid, polyoxymonocarboxylic acid, aminocarboxylic acid, lactone compound, and At least one selected from these salts can be used.

  Here, examples of the polycarboxylic acid include citric acid, malonic acid, maleic acid, succinic acid, tricarballylic acid, lactic acid, malic acid, tartaric acid, phthalic acid, isophthalic acid, 2-sulfoethylamino-N, N-di-acid. Acetic acid, iminodiacetic acid, nitrilotriacetic acid, ethylenediaminetetraacetic acid, triethylenediaminetetraacetic acid can be used, and as polyoxymonocarboxylic acid, for example, gluconic acid, glucoheptonic acid, and glyceric acid can be used.

  Examples of aminocarboxylic acids that can be used include glycine, glutamic acid, aspartic acid, β-alanine-N, N-diacetic acid, and examples of lactone compounds include glucono-δ-lactone and glucoheptonolactone. Can be used.

  Further, it is also preferable to add a brightener, an antioxidant, and further a conductive agent to the plating bath as necessary.

  Here, as the brightener, an anionic, cationic, nonionic or amphoteric surfactant can be used as appropriate.

In addition, an appropriate amount of an antioxidant is appropriately added for the purpose of preventing Sn ²⁺ from being oxidized to Sn ⁴⁺ , and hydroquinone, pyrocatechol, resorcin, ascorbic acid, hydrazine or the like may be used as an antioxidant. it can.

  As the conductive agent, ammonium sulfate or the like can be used.

  In addition, a tin plating bath having a pH adjusted to 3 to 10 is used. That is, when the object to be plated is mainly composed of a ceramic material or a glass material, if the pH becomes a strong acidity of less than 3 or a strong alkalinity of more than 10, the ceramic material or the glass material may be dissolved to cause quality deterioration. .

  Therefore, in the present embodiment, an alkaline reagent such as sodium hydroxide, potassium hydroxide, or ammonia water, or an acidic reagent such as hydrochloric acid, sulfuric acid, nitric acid, sulfamic acid, or the like is appropriately added as a pH adjuster to adjust the pH of the tin plating bath. Is adjusted to be 3-10.

  Next, a plating method using the tin plating bath will be described in detail.

  In this plating method, electrolytic treatment is performed in a state where the object to be plated is not immersed in the Sn plating bath (first electrolytic treatment step), and then the object to be plated is immersed in the Sn plating bath to perform electrolytic plating. (Second electrolytic treatment step).

  FIG. 1 is a diagram showing an outline of a plating apparatus in the first electrolytic treatment process.

  That is, in the plating apparatus, the Sn plating bath 2 is filled in the plating tank 1, and the Sn anode 3, the cathode 4, and the barrel container 5 are immersed in the Sn plating bath 2. Further, the cathode 4 has a cathode body 4a with insulation coating and an electrode portion 4b made of aluminum or the like provided at the tip of the cathode body 4a. The electrode portion 4b is disposed inside the barrel container 5. Yes.

In the plating apparatus configured in this way, when an electric current is passed between the anode 3 and the cathode 4 in a state where the object to be plated is not immersed in the plating bath, an oxidation reaction occurs at the anode, and Sn is dissolved as Sn ^2+. Then, it combines with the complexing agent in the Sn plating bath 3 to form a stable Sn complex.

That is, when a stannous salt is added to the complexing agent, because of the presence of anions around the Sn ^2+, Sn ²⁺ is less likely to bind to the complexing agent, Sn ²⁺ is stable between the complexing agent It becomes difficult to form a complex.

However, when an electrolytic treatment is performed by applying current between the anode 3 and the cathode 2 before the electrolytic plating is applied to the object to be plated, an oxidation reaction occurs at the anode and Sn ²⁺ is dissolved, and such Sn ²⁺ becomes Sn. It combines with the complexing agent in the plating bath 2 to form a stable Sn complex. In other words, a stable Sn complex is formed by replacing Sn ²⁺ dissolved from the beginning in the plating bath 2 with Sn ²⁺ dissolved from the anode.

Then, the replacement ratio of the Sn ²⁺ from Sn ²⁺ and the anode in the plating bath 2 can be calculated from the laws of electrolysis Faraday.

  That is, according to Faraday's law of electrolysis, the deposition amount w (g) of Sn deposited on the cathode by the oxidation-reduction reaction between the electrodes is expressed by the formula (1).

w = (I × t × M) / (Z × F) (1)
Here, I is current (A), t is energization time (sec), M is the atomic weight of Sn (= 18.7), Z is the valence of Sn (= 2), and F is the Faraday constant (= 96500 coulomb). ), And (I × t) indicates the quantity of electricity Q.

Therefore, by determining the amount of electricity Q, that is, the current I and the energization time t, the precipitation amount w of Sn at the cathode is calculated, and the substitution rate is determined from this precipitation amount w and the Sn ²⁺ concentration in the stannous salt. Can be sought.

And, it is considered that Sn ²⁺ in the initial bath is preferentially precipitated. In that case, the substitution ratio is preferably 50% or more. That is, as described above, by replacing Sn ²⁺ dissolved in the stannous salt with Sn ²⁺ from the anode, it is possible to increase the film thickness of the Sn film even in the initial bath stage, but the substitution ratio is high. If it is less than 50%, it is thinner than the film thickness in the continuous use bath, and it is difficult to obtain a film thickness equivalent to that in the continuous use bath. Therefore, the substitution ratio is preferably 50% or more.

  The amount of electricity Q is determined by the product of the current I and time t as described above, but the current I needs to be determined to a value that does not generate hydrogen.

  That is, when a current is consumed for hydrogen generation, a current consumed for Sn deposition decreases, so that the amount of electricity Q for Sn deposition relatively decreases and the substitution rate decreases. In addition, “hydrogen is generated” means that the hydrogen deposition potential exceeds the hydrogen overvoltage and shifts to an electrochemically low potential, and Sn is stable in an ionic state in the plating bath. Become. Therefore, in order to deposit Sn, it is necessary to flow a large amount of electrons to the object to be plated and to apply a large amount of energy to the object to be plated. As a result, the oxide constituting the element body of the object to be plated causes an ionization reaction and melts, and there is a possibility that problems such as separation of the conductive portion at the plating target portion from the element body may occur.

  For this reason, it is necessary to set the current I to a value that does not generate hydrogen, and it is necessary to determine the energization time t from the current I and the amount of electricity Q.

  Next, the process proceeds to the second electrolytic treatment process.

  FIG. 2 is a diagram showing an outline of the plating apparatus in the second electrolytic treatment process.

  That is, the non-conductive conductor 20 formed of the object 6 to be plated, the steel ball conductive medium 7 and the resin can be brought into contact with the cathode 4 with respect to the plating apparatus subjected to the electrolytic treatment in the first electrolytic treatment step. In this way, the barrel container 5 is energized between the anode 3 and the cathode 4 while rotating, swinging, vibrating, etc., and electroplating is performed to form a Sn film on the surface of the object 6 to be plated. To do.

  And in this Embodiment, since it electrolyzes without immersing a to-be-plated object in Sn plating bath before performing electroplating, a stable Sn complex can be formed at the time of electroplating, therefore, initial stage It is possible to form a thick plating film at the bath stage, thereby obtaining a plated product having a plating film with substantially the same film thickness without changing the plating conditions in both the initial bath and the continuous use bath. Is possible.

  Next, a method for producing a multilayer ceramic capacitor as an electronic component using the plating method will be described in detail.

  FIG. 3 is a cross-sectional view schematically showing an embodiment of the multilayer ceramic capacitor.

In the multilayer ceramic capacitor, internal electrodes 8 (8a to 8f) are embedded in a ceramic body (component body) 12 made of a dielectric ceramic material such as BaTiO ₃ , and both ends of the ceramic body 12 are embedded. External electrodes (conductive portions) 9a and 9b are formed, and Ni coatings 10a and 10b and Sn coatings 11a and 11b are formed on the surfaces of the external electrodes 9a and 9b.

  Specifically, the internal electrodes 8a to 8f are juxtaposed in the stacking direction, the internal electrodes 8a, 8c, and 8e are electrically connected to the external electrode 9a, and the internal electrodes 8b, 8d, and 8f are external electrodes 9b. And are electrically connected. And electrostatic capacitance is formed between the opposing surfaces of the internal electrodes 8a, 8c, 8e and the internal electrodes 8b, 8d, 8f.

  Hereinafter, a method for producing the multilayer ceramic capacitor will be described in detail.

First, a predetermined dielectric ceramic material such as BaCO ₃ , TiO ₂ , ZrO _2, etc. is mixed and subjected to processes such as pulverization, drying and calcination, and then a ceramic green sheet (hereinafter referred to as “ceramic sheet”) by a doctor blade method. Is made.

  Next, a conductive paste for internal electrodes in which an organic component such as glass particles or varnish is contained in a conductive material such as Ag, Cu, or Ni is prepared. Then, screen printing is performed on the surface of the ceramic sheet using the conductive paste to form a conductive pattern, and then the ceramic sheet on which the conductive pattern is formed is laminated, and the ceramic on which the conductive pattern is not formed A laminated body is formed by sandwiching and pressing with a sheet. Thereafter, the laminated body is fired at a predetermined temperature (for example, 900 to 1300 ° C.), barrel-polished, and deburred, whereby the ceramic body 12 is manufactured.

  Next, a conductive paste for external electrodes containing a conductive material such as Ag or Cu is prepared, and the conductive paste is applied to both ends of the ceramic body 12 by a dip method or the like, and then a temperature of 600 to 800 ° C. The baking process is performed with. As a result, organic components such as varnish burn and burn out, and external electrodes 9a and 9b are formed at both ends. After that, the ceramic body 12 on which the external electrodes 9a and 9b are formed is used as an object to be plated, and Ni plating and Sn plating are performed by an electrolytic barrel plating method to form the Ni films 10a and 10b and the Sn films 11a and 11b. .

  That is, when performing Ni plating, first, for example, the plating tank is filled with a Ni plating bath containing nickel sulfate, nickel chloride and boric acid.

  Next, the object to be plated, the conductive medium and the non-conductive medium are accommodated in a barrel container, the Ni anode, the cathode, and the barrel container are immersed in a plating tank, and the barrel container is rotated and swung. Then, a current is passed between the anode and the cathode at a predetermined current density for a predetermined time while the object to be plated is brought into contact with the cathode by vibration or the like, thereby performing electrolytic plating, and the Ni film 10a is applied to the surfaces of the external electrodes 9a and 9b. 10b.

In addition, when Sn plating is performed, first, after filling the plating bath with the Sn plating bath, the Sn anode, the cathode, and the barrel container are immersed, and Sn ²⁺ dissolved in the plating bath from the beginning is removed from the anode. The current value and energization time are set so as to replace 50% or more of Sn ²⁺ and energization is performed between the anode and the cathode, and electrolytic treatment is performed.

  Next, an object to be plated, a conductive medium, and a non-conductive medium are placed in the barrel container, and electroplating is performed for a predetermined time between the anode and the cathode while rotating, swinging, or vibrating the barrel container. The Sn coatings 11a and 11b are formed on the surfaces of the Ni coatings 10a and 10b, whereby a multilayer ceramic capacitor is manufactured.

In this way, the present multilayer ceramic capacitor is subjected to electrolytic plating treatment after replacing Sn ²⁺ dissolved in the plating bath from Sn ²⁺ from the anode by 50% or more, so that the current density is increased or the plating is performed. Even if the processing time is not lengthened, the Sn plating films 11a and 11b having substantially the same film thickness as that of the continuous use bath can be formed from the initial bath. Moreover, excessively thick Sn coatings 11a and 11b are not formed in the continuous use bath, so that the product can be prevented from sticking in the Sn plating bath, and the high quality with excellent reliability. A multilayer ceramic capacitor can be manufactured with high efficiency.

  The present invention is not limited to the above embodiment.

  In the first electrolytic treatment step (FIG. 1), the electrolytic treatment is performed in a state where the object to be plated and the conductive medium are not immersed in the plating bath 2. That is, it may be immersed in the barrel container 5.

  Further, the first electrolytic treatment step may be performed in a state in which a barrel container or a conductive medium is immersed in the plating bath 2, and only the anode and the cathode are plated without immersing the barrel container in the plating bath 2. It may be performed by immersing in the bath 2.

  In the above embodiment, the Sn plating bath has been described. However, the Sn—Pb plating bath, the Sn—Ag plating bath, the Sn—Zn plating bath, the Sn—Cu plating bath, the Sn—Bi plating bath, and the Sn—In plating are used. The same applies to Sn alloy plating baths such as baths.

  Also applicable to plating baths other than Sn plating bath and Sn alloy bath, such as Au plating bath, Ag plating bath, Pd plating bath, Pt plating bath, Cu plating bath, Ni plating bath, and these metal species. The present invention can be similarly applied to an alloy plating bath having a main component.

  Moreover, although rotating barrel plating was demonstrated to the example as a plating method, the effect similar to this invention can be show | played also about other plating, such as vibration barrel plating and rocking barrel plating.

  Also, the electronic component is not limited to the multilayer ceramic capacitor, and can be applied to an electronic component such as a thermistor or a resistor.

  Next, examples of the present invention will be specifically described.

次に、縦１．０ｍｍ、横０．５ｍｍ、厚み０．５ｍｍの被めっき物を用意した。尚、この被めっき物は、内部電極の埋設されたセラミック素体の両端部にガラス成分を含有したＣｕからなる厚膜電極（外部電極）を形成したものである。 [Preparation of Sn plating bath (including Sn alloy plating bath)]
First, the plating baths of sample numbers 1 to 4 having the plating composition shown in Table 1 were prepared.

Next, an object to be plated having a length of 1.0 mm, a width of 0.5 mm, and a thickness of 0.5 mm was prepared. In addition, this to-be-plated thing forms the thick film electrode (external electrode) which consists of Cu containing a glass component in the both ends of the ceramic element | base body with which the internal electrode was embed | buried.

  Next, this object to be plated was subjected to electrolytic barrel plating by using an Ni plating bath having the following plating composition and applying a current of 8 A for 120 minutes to form a Ni film having a thickness of about 3 μm.

次いで、Ｎｉ皮膜が形成されたセラミック素体を被めっき物とし、上記電解処理済めっき液を使用し、所定個数の被めっき物を１バッチとして各バッチ毎に８Ａの電流を２時間通電して電解めっき処理を施し、被めっき物の表面にＳｎ皮膜を形成した。 [Composition of Ni plating bath]
Nickel sulfate 1000 mol / m ³
Nickel chloride 200mol / m ³
Boric acid (pH buffer) 70 mol / m ³
pH: 4.5
Bath temperature: 60 ° C
Next, an amount of electricity as shown in Table 2 is applied to the plating baths of Sample Nos. 1 to 4, and an electrolytically treated plating solution having substitution ratios of 0%, 40%, 50%, 60%, and 100% is obtained. Produced.

Next, the ceramic body on which the Ni film is formed is used as an object to be plated, the above-mentioned electrolytically treated plating solution is used, and a predetermined number of objects to be plated are used as one batch, and a current of 8 A is applied to each batch for 2 hours. Electrolytic plating treatment was performed to form a Sn film on the surface of the object to be plated.

Subsequently, 20 samples were sampled from the samples in the initial bath and the continuous use bath, and the film thickness of the Sn film was measured with a fluorescent X-ray film thickness meter. Here, the initial bath is the Sn plating bath subjected to the first batch treatment, and the continuous use bath is after all Sn ²⁺ in the metal salt contained in the plating bath is replaced with Sn ²⁺ from the anode. It was judged whether it was a bath for continuous use with an electric quantity Q per 1 m ³ .

That is, the deposition amount w on the cathode is calculated by substituting the electric quantity Q (current I, energization time t) into the mathematical formula (1) described in the section of [Best Mode for Carrying Out the Invention]. Can do. And it can be considered that when this precipitation amount w completely replaces the Sn ²⁺ concentration (g / L) in the metal salt, the bath was continuously used. Therefore, the Sn ²⁺ concentration is calculated from the metal salt content of the Sn plating bath, the amount of electricity Q per 1 m ³ corresponding to this Sn ²⁺ concentration is obtained, and the amount of electricity Q is loaded on the Sn plating bath (electrolyzer). When it becomes a continuous use bath. In this example and the comparative example, the continuous use bath was set after the time when the amount of electricity reached 300 [A · min / m ³ ].

この表３から明らかなように連続使用浴では４．０〜４．２μｍの膜厚を有するＳｎ皮膜を得ているが、置換割合が「０」の場合は、初期浴の膜厚は２．４〜２．６μｍと薄いＳｎ皮膜しか得られないことが分った。 Table 3 shows the measurement results of the film thickness of the initial bath and the film of the continuous use bath for each of the sample numbers 1 to 4 at each replacement ratio.

As is apparent from Table 3, a Sn film having a film thickness of 4.0 to 4.2 μm was obtained in the continuous use bath. When the substitution ratio was “0”, the film thickness of the initial bath was 2. It was found that only a thin Sn film of 4 to 2.6 μm can be obtained.

On the other hand, when Sn ²⁺ dissolved in the plating bath from the beginning is partially or completely replaced with Sn ²⁺ from the anode, a thick Sn film can be formed at the initial bath stage. In particular, it was confirmed that when the substitution ratio is 50% or more, a Sn film having a film thickness substantially equivalent to that of the continuous use bath can be obtained.

It is the schematic which showed typically the plating apparatus provided to a 1st electrolytic treatment process. It is the schematic which showed typically the plating apparatus provided to a 2nd electrolytic treatment process. It is sectional drawing which showed typically the multilayer ceramic capacitor as a ceramic electronic component manufactured using the plating bath of this invention.

Explanation of symbols

2 Sn plating bath (plating bath)
3 Anode 4 Cathode 6 Plated object 7 Conductive medium 9a, 9b External electrode (conductive part)
11a, 11b Sn coating (metal coating)

Claims (7)

A plating method for performing electrolytic plating using a plating bath containing a metal ion of a plating metal forming a plating film and a complexing agent capable of forming a complex with the metal ion,
The complexing agent contains at least one selected from polycarboxylic acids, polyoxymonocarboxylic acids, aminocarboxylic acids, lactone compounds, and salts thereof,
An anode for supplying metal ions of the plating metal and a cathode are immersed in the plating bath, and an electrolytic treatment is performed by energizing the anode and the cathode while the object to be plated is not immersed in the plating bath. A first electrolytic treatment step, and a second electrolytic treatment in which the object to be plated is immersed in the plating bath after the first electrolytic treatment step is completed, and the electrolytic treatment is performed by energizing the anode and the cathode. A plating method comprising the steps of:   2. The plating method according to claim 1, wherein in the first electrolytic treatment step, 50% or more of metal ions contained in the plating bath are replaced with metal ions supplied from the anode. In the second electrolytic treatment step, an electrolytic treatment is performed by energizing between the anode and the cathode in a state where a conductive medium formed of a material different from the object to be plated is immersed in the plating bath. The plating method according to claim 1 or 2. In the second electrolytic treatment step, the non-conductive medium formed of a material different from the object to be plated is immersed in the plating bath and energized between the anode and the cathode to perform the electrolytic treatment. The plating method according to any one of claims 1 to 3, wherein the plating method is characterized. The plating method according to claim 1 , wherein the plating metal contains tin as a main component . The plating method according to any one of claims 1 to 5, wherein a hydrogen ion exponent pH of the plating bath is adjusted to 3 to 10 . An electronic component manufacturing method for manufacturing an electronic component by performing a plating process on an object to be plated in which a conductive portion is formed on the surface of the component element body,
A method for manufacturing an electronic component, comprising forming a metal film on the surface of the conductive portion using the plating method according to claim 1.

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