JP2018076570A - Barrel plating or high-speed rotary plating method that employs neutral stannum plating liquid - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a barrel plating or high-speed rotary plating method capable of preventing electronic components from adhering to each other while carrying out barrel plating or high-speed rotary plating and of improving the coatability of the plating layer over the electronic components, and a neutral stannum plating liquid for use therein.SOLUTION: The neutral stannum plating liquid comprises (A) a stannous ion, (B) an acid or a salt thereof, (C) a complexing agent and (D) a diamine comprising a polyoxyalkylene chain with its pH in a range of from 4 to 8. There is provided a method of plating an electronic component according to barrel plating or high-speed rotary plating of an electronic component employing the neutral stannum plating liquid. There is provided a method of carrying out barrel plating at an electric current density of from 0.05 to 0.5 mA/dm. The neutral stannum plating liquid comprises a diamine comprising a polyoxyalkylene chain with the molecular weight of the diamine preferably being from 200 to 1100.SELECTED DRAWING: None

Description

  The present invention relates to a barrel plating or high-speed rotary plating method for an electronic component using a neutral tin plating solution, and a neutral tin plating solution used therefor. More specifically, a barrel plating or high-speed rotation plating method capable of suppressing adhesion between electronic components during barrel plating or high-speed rotation plating and improving the coating property of the plating on the electronic components, and The present invention relates to a neutral tin plating solution to be used.

  Tin plating is widely performed for the purpose of improving the soldering performance of electronic components. The method of tin plating on the electronic component is selected from various methods such as barrel plating and rack plating according to the shape and structure of the plated portion. Barrel plating is generally used as a plating method for small electronic components such as chip resistors and chip capacitors. In recent years, high-speed rotational plating such as a flow-through loop has also been performed as a plating method for small electronic components.

  Usually, when barrel plating is performed, an electronic component that is an object to be plated and a conductive metal ball (dummy ball) for improving conductivity during plating are placed in a bowl-shaped container called a barrel. In the state immersed in the liquid, electricity is applied while rotating or vibrating the barrel, and the electronic parts are plated. However, in recent years, as electronic components have become smaller in size, electronic components, dummy balls, or sticking between them tend to occur during barrel plating, and the productivity of electronic components by barrel plating deteriorates. There was a problem. Further, depending on the type of the plating solution, foaming may occur on the surface of the solution, and deterioration of the plating work has been a problem. In high-speed rotation plating, an electronic component that is an object to be plated is placed in a disk-shaped cell, and plating is performed while rotating the cell at a high speed. However, the same problem as barrel plating may occur.

  Japanese Patent Application Laid-Open No. 2009-299123 discloses an electrotin plating solution for chip parts having a pH of 1 or less, which contains stannous ions, acid, dipolyoxyalkylene alkylamine or amine oxide, and an anti-sticking agent. However, when an electronic component ceramic member that is an object to be plated is contained, using a plating solution having a pH of 1 or less is not preferable because the ceramic member is damaged.

  Japanese Patent Application Laid-Open No. 2003-293186 discloses a neutral tin plating bath containing a soluble stannous salt, an acid or a salt thereof, a complexing agent selected from oxycarboxylic acid and the like, and a quaternary amine polymer. . However, in the study by the present inventors, the neutral tin plating solution using a quaternary amine polymer has not been sufficiently effective in preventing adhesion between objects to be plated, and further improvement has been demanded.

JP 2009-299123 A JP 2003-293186 A

  Therefore, the object of the present invention is to suppress the adhesion between electronic components even in the case of barrel plating or high-speed rotation plating of electronic components that have been downsized in recent years. An object of the present invention is to provide an electronic component plating method and a neutral tin plating solution used therefor which are few.

  As a result of intensive studies, the inventors of the present invention added a diamine having a polyoxyalkylene chain to a neutral tin plating solution, thereby suppressing foaming of the plating solution and suppressing adhesion between objects to be plated. The present inventors have found that productivity of high-speed rotary plating can be improved.

  That is, in one aspect, the present invention contains (A) a stannous ion, (B) an acid or a salt thereof, (C) a complexing agent and (D) a diamine having a polyoxyalkylene chain, and has a pH of 4 to 8. An electronic component barrel plating or high-speed rotary plating method is provided, which includes a step of barrel-plating or high-speed rotary plating on an electronic component using a tin plating solution in the range described above.

  Moreover, this invention contains the diamine which has (A) stannous ion, (B) acid or its salt, (C) complexing agent, and (D) polyoxyalkylene chain in one aspect | mode, and pH is 4-8. A neutral tin plating solution for barrel plating or high-speed rotation plating is provided.

Abbreviations used throughout this specification have the following meanings unless otherwise indicated. g = gram; mg = milligram; C = degrees Celsius; min = minute, m = meter; cm = centimeter; L = liter; mL = milliliter; A = ampere; dm ² = square decimeter. All numerical ranges include boundary values and can be combined in any order. Throughout this specification, the terms “plating solution” and “plating bath” have the same meaning and are used interchangeably. Percentage (%) means% by weight unless otherwise specified herein.

  The barrel plating or high speed rotary plating method of the electronic component of the present invention contains (A) stannous ion, (B) an acid or a salt thereof, (C) a complexing agent and (D) a diamine having a polyoxyalkylene chain. A plating solution having a pH in the range of 4 to 8 is used. Hereinafter, this plating solution will be described in order.

(A) Stannous ion The plating solution used in the present invention contains stannous ion as an essential constituent. The stannous ion is a divalent tin ion. Any compound that can supply stannous ions in the plating solution can be used. In general, a tin salt of an inorganic acid or an organic acid used in the plating solution is preferable. For example, the tin salt of inorganic acid includes sulfuric acid and stannous salt of hydrochloric acid, and the tin salt of organic acid includes substituted or unsubstituted alkane sulfonic acid or alkanol sulfonic acid such as methane sulfonic acid. Stannous salts such as ethanesulfonic acid, propanesulfonic acid, 2-hydroxyethane-1-sulfonic acid, 2-hydroxypropane-1-sulfonic acid or 1-hydroxypropane-2-sulfonic acid. A particularly preferred stannous ion source is a stannous sulfate salt for an inorganic acid salt and a stannous methanesulfonate salt for an organic acid salt. These compounds capable of supplying ions can be used alone or as a mixture of two or more.

  The content of stannous ions in the plating solution is, for example, from 5 g / L to 30 g / L, preferably from 8 g / L to 25 g / L, more preferably from 10 g / L to 20 g / L as tin ions. It is.

(B) Acid or its salt The plating solution used for this invention contains an acid or its salt. Any acid or salt thereof can be used as long as it has a role of providing conductivity to the plating solution. Both organic and inorganic acids and their salts can be used. Examples of the organic acid include substituted or unsubstituted alkane sulfonic acid or alkanol sulfonic acid. For example, methane sulfonic acid, ethane sulfonic acid, propane sulfonic acid, 2-hydroxyethane-1-sulfonic acid, 2-hydroxy Examples include propane-1-sulfonic acid or 1-hydroxypropane-2-sulfonic acid. Methanesulfonic acid is preferred. As the inorganic acid, for example, sulfuric acid or hydrochloric acid can be used, and sulfuric acid is preferable. These salts may be any salts such as alkali metal salts, alkaline earth metal salts, ammonium salts and amine salts. The acid or a salt thereof can be used alone or as a mixture of two or more. As described above, it is preferable to use the inorganic acid or organic acid used in the stannous ion salt and salts thereof, but the present invention is not limited to this.

  However, since the plating solution used in the present invention is a neutral plating solution, when using the above-mentioned organic acid or inorganic acid as a conductive substance, various bases are added to the plating solution as a pH adjuster to adjust the pH. Can be adjusted in the range of 4-8.

  The content of the acid or its salt in the plating solution is, for example, 30 g / L or more and 300 g / L or less, preferably 50 g / L or more and 200 g / L or less, more preferably 80 g / L or more and 150 g / L or less. .

(C) Complexing agent The plating solution used in the present invention contains a complexing agent as an essential constituent. In general, divalent tin ions in a tin plating solution are stable when strongly acidic, but become unstable near neutrality, and are easily deposited as tin metal, or the plating solution is easily decomposed. Since the tin plating solution of the present invention has a pH in the range of 4-8, it is necessary to contain a complexing agent. The complexing agent is not particularly limited as long as it has an effect of stabilizing the plating solution. Examples of the complexing agent include gluconic acid, citric acid, malonic acid, succinic acid, tartaric acid, and salts thereof. Among these, gluconic acid or a salt thereof is preferable, and sodium gluconate is most preferable.

  The content of the complexing agent in the plating solution is, for example, from 80 g / L to 250 g / L, preferably from 100 g / L to 200 / L, and more preferably from 125 g / L to 175 g / L.

(D) Diamine having a polyoxyalkylene chain The plating solution used in the present invention contains a diamine having a polyoxyalkylene chain as an essential constituent. By containing this compound, adherence between objects to be plated can be suppressed, and the productivity of barrel plating can be improved. The diamine having a polyoxyalkylene chain is preferably a compound represented by the following chemical formula.

Here, R ₁ in the above formula is a linear or branched alkylene group having 1 to 10 carbon atoms, preferably a linear or branched alkylene group having 1 to 6 carbon atoms, more preferably 1 to 4 carbon atoms. Or a linear or branched alkylene group. R _{2 to} R ₅ are each independently a linear or branched alkylene group having 1 to 10 carbon atoms, preferably a linear or branched alkylene group having 1 to 6 carbon atoms, more preferably 1 to 4 carbon atoms. A linear or branched alkylene group. n, m, o, and p are each independently an integer of 0 to 15. However, all of n, m, o, and p are not 0. n, m, o, and p are each preferably an integer of 1 to 12, and more preferably an integer of 1 to 8, respectively. The sum of n, m, o, and p is 1-60, preferably 2-30, more preferably 4-25.

  The present inventors have found that the plating solution containing the above compound reduces the adhesion of electronic components during barrel plating or high-speed rotation plating, and is less likely to cause bubbles that sometimes cause problems during plating. It has been found that a plating operation can be performed.

  The weight average molecular weight of the diamine having a polyoxyalkylene chain is preferably 200 to 1100, more preferably 300 to 600. Here, the weight average molecular weight is a value measured by the GPC method.

  A commercially available thing can be used for the diamine which has a polyoxyalkylene chain, for example, Adeka polyether EDP-450, Adeka polyether BM-54 (all are made by Adeka company), etc. can be used.

  The content of the diamine having a polyoxyalkylene chain in the plating solution is, for example, from 0.1 g / L to 30 g / L, preferably from 0.5 g / L to 20 g / L, more preferably 1 g / L. It is 5 g / L or less.

(E) pH adjuster The pH of the neutral tin plating solution used in the present invention is in the range of 4 to 8, preferably 5 to 7. In order to adjust the pH within this range, a base or an acid can be added to the plating solution. Examples of the acid that can be used include methanesulfonic acid, ethanesulfonic acid, propanesulfonic acid, hydrochloric acid and sulfuric acid. Examples of the base that can be used include sodium hydroxide, potassium hydroxide and aqueous ammonia.

  The neutral tin plating solution used in the present invention can contain other components that are generally added to the plating solution as optional components. For example, antioxidants, brighteners, smoothing agents, conductive salts, anodic dissolving agents, preservatives, wetting agents and the like can be contained.

(F) Antioxidant In the plating solution of the present invention, an antioxidant can be arbitrarily used. Antioxidants are used to prevent the oxidation of tin ions from divalent to tetravalent, and for example, hydroquinone, catechol, resorcin, phloroglucin, pyrogallol, hydroquinonesulfonic acid and salts thereof can be used.

  The antioxidant is used in the plating bath at a concentration of, for example, 100 mg / L to 50 g / L, preferably 200 mg / L to 20 g / L, more preferably 0.5 g / L to 5 g / L. Is preferred.

  The order of addition of each component when constructing a plating bath is not particularly limited, but from the viewpoint of safety, after adding water, add acid or its salt, mix thoroughly, and then add tin salt Then, after fully dissolving, add necessary chemicals sequentially.

  The electronic component that is the object to be plated in the present invention is not particularly limited. For example, a resistor (resistor), a capacitor (capacitor), an inductor (inductor transformer), a thermistor, a varistor, a variable resistor, a variable condenser, etc. Passive parts, functional parts such as crystal resonators, LC filters, ceramic filters, delay lines, and SAW filters, and connection parts such as switches, connectors, relay fuses, and optical connection parts. In particular, capacitors, inductors, thermistors and varistors have a ceramic part in their parts and cannot use a strongly acidic plating solution. Therefore, plating using the neutral plating bath of the present invention is preferable.

Plating Method A method for performing barrel plating using the plating solution of the present invention will be described. As described above, in normal barrel plating, an electronic component and a dummy ball, which are objects to be plated, are placed in a barrel and energized while rotating the barrel while immersed in a plating solution. The plating method includes a case where only the object to be plated is put in a barrel without inserting a dummy ball. As the barrel plating method, any apparatus such as a horizontal or inclined rotating barrel type, a swinging barrel type, or a vibrating barrel type can be used. The temperature of the plating solution during barrel plating can be, for example, 10 to 50 ° C., preferably 20 to 40 ° C. The cathode current density is appropriately selected within the range of, for example, 0.01 to 10 A / dm ² , preferably 0.05 to 5 A / dm ² , and more preferably 0.1 to 0.5 A / dm ^2. . During the plating process, the plating bath may be unstirred, and it is also possible to select a method such as stirring with a stirrer or the like, or liquid flow with a pump.

In addition, when performing high-speed rotation plating using the plating solution of the present invention, for example, using a flow looper or the like, the conditions are 10 to 50 ° C., cathode current density 0.01 to 10 A / dm ^{2 and the} like. Plating can be performed while rotating a small electronic component, which is an object, at high speed.

Example 1
A tin plating solution was erected with the following composition.
(A) stannous methanesulfonate: 39 g / L (as tin ion: 15 g / L)
(B) Sodium methanesulfonate: 100 g / L
(C) Sodium gluconate: 145 g / L
(D) Adeka polyether EDP-450 (molecular weight: 450): 2 g / L
(E) Sodium hydroxide: Amount that the pH of the plating solution is 6 (F) Sodium erythorbate: 2 g / L
(G) Water: remaining

Structure of Adeka Polyether EDP-450

  Barrel tin plating was performed on a chip resistor plated with nickel under the following conditions using 2 L of a tin plating solution that had been built, and various evaluations were performed. The results are shown in Table 1.

Barrel plating condition 1
Barrel: Yamamoto mini-barrel (capacity: about 140mL)
Plating object: Chip resistor 5g
Dummy ball: Steel ball, diameter 0.71-0.85mm, 60g
Current density: 0.2 A / dm ²
Plating time: 50 minutes Plating solution temperature: 35 ° C
Rotation speed: 6rpm

(Solder wettability test)
2 L each of the plating solutions of Examples and Comparative Examples were prepared, electrotin-plated for 50 minutes at a bath temperature of 35 ° C. and 0.2 A / dm ² , and a 5 μm tin-plated film on the nickel-plated chip resistor external electrode Deposited. A moisture resistance test treatment (PCT treatment (temperature: 105 ° C., humidity: 100%, 4 hours)) is performed on each of the tin plating films obtained, and the solderability of the plating film before and after the moisture resistance test is determined by Multi Solderability Tester manufactured by Tarutin. The zero cross time (“ZC.T”) was measured and evaluated by the solder paste equilibrium method using SWET-2100. The measurement conditions are as follows.

Zero cross time measurement conditions-Solder paste: Sn: Ag: Cu = 95.75: 3.5: 0.75
Test temperature: 245 ° C
・ Immersion depth: 0.15 mm
・ Test speed: 2 mm / second ・ Retention time: 8 seconds

  The solder wettability was measured before and after the PCT treatment and is shown in Table 1.

  Coupling ratio (weight ratio of fixed chip to total chip weight) and agglomeration ratio (weight ratio of fixed dummy ball to total dummy ball weight) were calculated and are also shown in Table 1.

Plating appearance and plating particle size (grain size)
A hull cell test was performed using the plating solution that had been erected, the appearance of the obtained plating film was observed with the naked eye, and the particle size of the plating was measured with SEM (2000 times).

Comparative Example 1
The composition was the same as in Example 1 except that 2 g / L of lauryldimethylaminoacetic acid betaine (Amphitol 20BS, manufactured by Kao Corporation) was used instead of (D) adecapolyether EDP-450 in Example 1. A tin plating solution was erected. The obtained plating solution had a high foaming property and was not suitable for barrel plating.

Comparative Example 2-4
Quaternary ammonium salt polymer (Papiogen P-113 (Comparative Example 2) and SenkaFix 401 (Comparative Example 3)) instead of (D) adecapolyether EDP-450 of Example 1 and A tin plating solution was erected with the same composition as in Example 1 except that 2 g / L each of quaternary ammonium salt (Eretat M-65 (Comparative Example 4)) was used. The plating solution obtained in Comparative Example 4 had a high foaming property and was not suitable for barrel plating. About the plating solution obtained by the comparative example 2 and the comparative example 3, operation similar to Example 1 was performed, respectively. In the plating solution obtained in Comparative Example 2, the appearance of the plating film obtained by the Hull Cell test was white and good, but in the barrel plating test, the coupling rate was as high as 81.3%. . In the plating solution obtained in Comparative Example 3, the appearance of the plating film obtained by the Hull Cell test was grayish black and was not preferable.

Example 2
The same test as in Example 1 was performed except that the barrel plating condition 1 was changed to the following barrel plating condition 2, and the coupling rate and the aggregation rate were measured. The results were a chip coupling rate of 0.1% and dummy ball agglomeration rate of 0%. Moreover, there was little foaming of a plating solution.
Barrel plating condition 2
Barrel: Yamamoto mini-barrel (capacity: about 140mL)
Plating object: Chip resistor 5g
Dummy ball: Steel ball, diameter 0.71-0.85mm, 60g
Current density: 0.2 A / dm ²
Plating time: 50 minutes Plating solution temperature: 35 ° C
Rotation speed: 12rpm

Claims (5)

  A tin plating solution containing (A) stannous ion, (B) acid or salt thereof, (C) complexing agent and (D) diamine having a polyoxyalkylene chain and having a pH in the range of 4 to 8 is used. A method of barrel plating or high-speed rotary plating of electronic parts, including a step of barrel plating or high-speed rotary plating of electronic parts. The method according to claim 1, wherein barrel plating is performed at a current density of 0.05 to 0.5 A / dm ² .   The method according to claim 1 or 2, wherein the electronic component is selected from a capacitor, an inductor, a thermistor and a varistor.   Barrel plating or high speed containing (A) stannous ion, (B) acid or salt thereof, (C) complexing agent and (D) diamine having polyoxyalkylene chain and having a pH in the range of 4-8. Neutral tin plating solution for rotary plating.   The neutral tin plating solution for barrel plating or high-speed rotation plating according to claim 4, wherein the diamine having a polyoxyalkylene chain has a molecular weight of 200 to 1100.