JPH02211612A - Anticorrosive composite material for electronic part and capacitor - Google Patents

Abstract

PURPOSE:To prevent corrosion of aluminum in an electronic part by dispersing inorganic material, having adsorptivity for halide ions, in a solution or a dispersed liquid containing a surface-active agent, a dispersant, a vehicle for coating material, etc. CONSTITUTION:As an inorganic material for forming a hardly soluble compound or a stable compound by reacting on an inorganic ion exchanger, for adsorbing halide ions by ion exchanging reaction, and on halide ions, to be concrete, hydrotalcite or the like, lead phosphate hydroxide, tin phosphate hydroxide, hydrated tin oxide, tin phosphate, lead phosphate, and lead hydrogen phosphate are preferable because of their large anticorrosive effect for aluminum. Further, in case an inorganic ion exchanger for adsorbing halide ions is used as the inorganic material, an inorganic ion exchanger having cation exchanging ability such as hydrated antimony oxide is preferably used in combination.

Description

Detailed Description of the Invention (a) Purpose of the Invention [Field of Industrial Application] The present invention provides an anticorrosion composition effective for preventing corrosion of electronic components used in the electronic industry, particularly for preventing corrosion of aluminum in the components. and to provide a corrosion-protected capacitor using the composition. [Prior Art] Corrosion is said to be the primary cause of failures in electronic equipment. A particular problem with failures due to corrosion is the following:
Corrosion of wiring, lead wires, and electrodes in parts.

Aluminum is used as an electrode material for electronic components such as aluminum electrolytic capacitors, film capacitors, and paper capacitors; and as a wiring material for IC1 semiconductors and the like.

It is well known that corrosion of aluminum progresses rapidly in the presence of ionic impurities, and halide ions such as chlorine, bromine, and fluorine are particularly problematic.

These ionic impurities are derived from raw materials such as packaging material resins (resins intended for insulation protection: epoxy resins, phenol resins, silicone resins, polyphenyline sulfide resins, etc.) and inorganic fillers; Items that are contaminated from the air, such as capacitors, and halogen-based agents such as trichlorethane, trichloroethylene, and freon used for cleaning solder flux after soldering printed wiring boards, etc., can penetrate into the terminal parts (elements). There are various sources of contamination, such as those that remain and decompose into halide ions, and in order to remove this, methods are being considered such as methods of refining raw materials in advance and methods of creating a structure that prevents the infiltration of cleaning agents. .

For example, raw materials such as IC encapsulants are washed with hot water,
Efforts have been made to reduce residual halide ions by alkali treatment.

However, hot water washing and alkaline treatment methods are not perfect, and in the end, trace amounts of halide ions remain in the raw materials.

Among capacitors, aluminum electrolytic capacitors are composed of an oxide film formed on the surface of a high-purity aluminum foil for an anode as a dielectric, an aluminum foil for a cathode, an electrolytic solution, and capacitor paper (electrolytic paper). FIG. 1 shows a typical aluminum electrolytic capacitor element, showing an aluminum foil (hereinafter referred to as "anode foil") on which an aluminum oxide film 2 is formed, which will serve as an anode, and an aluminum foil (hereinafter referred to as "anode foil"), which will serve as a cathode. (hereinafter referred to as "cathode foil")3
An electrolytic paper 4 is sandwiched between the two foils (hereinafter referred to as "electrode foils"), and this is wound into a cylindrical shape to form the element 1, lead materials 5 and 6 are provided, and the structure is impregnated with an electrolytic solution. ing.

FIG. 2 shows a general aluminum electrolytic capacitor in which the above-mentioned elements are housed in an exterior case 8.
The case opening is sealed with a sealing material 7.

Electrolytic paper is an insulator, so when it is sandwiched between two foils, the dielectric (oxide film) between the anode foils and the electrolytic paper become a dielectric and become a capacitor, but if left as is, the capacitance will increase. is extremely small. However, when this element is impregnated with an electrolyte, the original capacitance is obtained on the anode foil.

In other words, the electrolyte essentially functions as a cathode. The electrolyte must not only have electrical conductivity but also the ability to repair the oxide film on the anode foil. That is, it must have the ability to form an oxide film by acting on the degraded portions of the oxide film.

This means that anodic oxidation occurs at the interface.

The electrolytic solution contains N,N-dimethylformamide, ethylene glycol, γ-butyl lactone, etc. as a main solvent, and organic acids, organic acid salts, boric acid, borates, phosphoric acid, phosphates, etc. as solutes. It is mainly used.

However, when halide ions such as C1- and Br- are present in the electrolyte, they react with aluminum and corrode it.

The corrosion process of aluminum when CI- is present as a halide ion is shown in (Equation 1) and (Equation 2).

When CI- is present in the electrolyte, it reacts with aluminum (Formula 1). Further, AlCl+ generated in this reaction is hydrolyzed to become aluminum hydroxide, and CI- is liberated again (Formula 2).

The liberated C1- acts on aluminum again (Formula 1)
. In this way, corrosion of aluminum is repeated.

28l+6Hc1 →2 AlCl3+ 3 I+□
... (Formula 1) AlCl3 + 30) 1-→A
t (OH) 3 +3 CI-... (Formula 2) CI-
There are two possible sources of this. One is when aluminum foil is subjected to electrochemical etching to increase its surface area, but CI-, an etching solution consisting of an aqueous chloride solution such as hydrochloric acid or sodium chloride, remains.

Second, when cleaning with a chlorinated solvent after soldering the capacitor and printed circuit board, etc., the chlorinated solvent may seep into the gap between the sealing material and the lead material or by diffusion within the sealing material.
For example, when CI- is released by a reaction such as (Formula 3).

cctzp-cc1pz→CCIF=CF2+ 2C
I-... (Formula 3) The latter is actually more problematic.

In order to solve this problem, methods of using solvents other than chlorine-based solvents are being considered, but they have problems such as flammability and high cost. No solvent.

In addition, using a sealing material that is difficult for solvents to penetrate or making the sealing material have a double structure are also ways to prevent the penetration of chlorinated solvents, but these are not adopted due to high costs and other reasons.

[Problem to be solved by the invention]

As mentioned above, each of the conventional methods for preventing corrosion of aluminum has drawbacks and is not usable.

Therefore, there is a strong need for a means to effectively and easily prevent the corrosion of aluminum without removing ionic impurities, especially halide ions, in advance (even if such impurities are present in electronic components). It's here.

(B) Structure of the Invention [Means for Solving the Problems] As a result of studying ways to effectively prevent corrosion of aluminum in aluminum electrolytic capacitors, the present inventors discovered that An anticorrosive composition is prepared by dispersing an inorganic substance (hereinafter simply referred to as "inorganic substance") that functions in a solution or dispersion containing one or more selected from a surfactant, a dispersant, and a paint vehicle. In addition, aluminum electrolytic capacitors using electrolytic paper coated with this anticorrosive composition on both sides or one side, and aluminum electrolytic capacitors coated with this anticorrosive composition on electrode foil, etc. It was also found that corrosion of aluminum is significantly prevented in a capacitor containing an anticorrosive composition, and the present invention was completed.

Inorganic substances used in the present invention include inorganic ion exchangers that adsorb halide ions through ion exchange reactions, and inorganic substances that react with halide ions to form poorly soluble compounds and stable compounds. , hydrotalcites, lead hydroxide phosphate represented by lead hydroxyapatite, tin hydroxide phosphate represented by tin hydroxyapatite, cadmium hydroxyapatite, zinc hydroxyapatite, hydrated bismuth oxide, hydrated lead oxide, hydrated oxide Examples include inorganic ion exchangers such as titanium, hydrated zirconium oxide, and hydrated tin oxide; and tin phosphate, lead phosphate, lead hydrogen phosphate, and the like.

Among the above, hydrotalcites, lead hydroxide phosphate,
Tin hydroxide phosphate, hydrated tin oxide, tin phosphate, lead phosphate, and lead hydrogen phosphate are preferred because they have a great effect of preventing corrosion of aluminum.

Furthermore, when an inorganic ion exchanger that adsorbs halide ions is used as the inorganic substance, it is more desirable to use an inorganic ion exchanger having cation exchange properties such as hydrous antimony oxide in combination.

That is, in general, adsorption of halide ions occurs more easily when the liquid is acidic. On the other hand, when the halide ion is present as a neutral salt, for example, NaCl, the sodium ion undergoes ion exchange with the cation exchanger and hydrogen ions are released, as shown in (Formula 4). As a result, the liquid properties shift to the acidic side, making it easier for halide ions to be adsorbed.

R-OH+NaC1-+R-ONa+HC1- (Formula 4
) (Formula 4), R-OH represents an inorganic ion exchanger having hydrogen in the exchange group and having cation exchange properties, and R-ONa
shows the inorganic ion exchanger after hydrogen has been replaced by sodium.

The inorganic substance in the present invention is dispersed in a solution or dispersion containing one or more selected from surfactants, dispersants, and paint vehicles.

The surfactant used in the present invention includes oxyethylene,
Examples include, but are not limited to, oxypropylene block copolymer/sorbitan fatty acid ester and polyoxyethylene alkyl phosphate ester. Silane coupling agents also fall under the category of surfactants.

On the other hand, examples of dispersants include acrylic acid polymer salts, acrylic ester polymers, and copolymers containing acrylic acid and acrylic ester as monomer units, and may be appropriately selected depending on the inorganic substance used. .

The surfactant and dispersant have the effect of improving the dispersibility of the inorganic substance in the medium or increasing the affinity for electrolytic paper.

The form of the anticorrosive composition when using a surfactant and a dispersant includes an aqueous solution, an organic solvent solution, an aqueous dispersion, etc.
An electrolytic solution of an aluminum electrolytic capacitor can also be used as the medium.

The paint vehicle may be of any type as long as it has the ability to form a coating film, but acrylic resins, phenolic resins, vinyl chloride resins, epoxy resins, vinyl acetate resins, styrene resins, styrene-butadiene copolymers, Examples include styrene-acrylic copolymer, ethylene-vinyl acetate copolymer, vinyl acetate-acrylic copolymer, and the like.

The form of the anticorrosive composition when using a paint vehicle includes organic solvent solution, water-based latex, aqueous solution, etc. However, organic solvent solution is flammable and harmful to the human body, and aqueous solution requires addition of inorganic substances. This causes problems such as increased viscosity, difficulty in handling, and limited concentration, and the most preferred form is water-based latex.

The anticorrosion composition of the present invention is obtained by blending an inorganic substance into a solution or dispersion of one or more types selected from the above-mentioned surfactants, dispersants, and coating vehicles, and the inorganic substance is water or other solvent. Methods include adding it by dispersing it in water or adding it as a powder.

The blending ratio of the inorganic substance is 1 to 5 of the total composition including the solvent.
0% by weight is preferred.

If it is less than 1% by weight, the amount of inorganic material present in the electrolytic paper or electrode foil is small, and the effect of preventing aluminum is small.

On the other hand, if it exceeds 50% by weight, other properties of the electrolytic paper or electrode foil may be impaired. That is, it causes a large change in the water absorption and water immersion conductivity of the electrolytic paper, and in the resistance and dielectric constant of the electrode foil.

The blending ratio of the surfactant and dispersant to the inorganic substance varies depending on the type and particle size of the inorganic substance, the type of surfactant and dispersant, and the type of medium used, but it is necessary to keep the inorganic substance in the most dispersed state. You can adjust it accordingly.

The amount of the paint vehicle to be blended with the inorganic substance is preferably 1 to 10,000 parts by weight, more preferably 1 to 100 parts by weight, per 100 parts by weight of the inorganic substance.

If the amount is less than 1 part by weight, it will be difficult to form a coating composition and it will be difficult to uniformly coat the surface of electrolytic paper or electrode foil.

On the other hand, if the amount exceeds 10 parts by weight, the effect of improving corrosion resistance is low, and in order to exhibit the corrosion prevention effect of aluminum, the coating film must be thickened, and as a result, electrolytic paper and There is a possibility that the function of the electrode foil may be inhibited.

The surfactant, dispersant, and paint vehicle may be used alone or in combination.

The anticorrosion composition of the present invention is present on or near the surface of aluminum for the purpose of corrosion prevention. For example, in the case of a capacitor, when the purpose is to prevent corrosion of an electrode foil, the anticorrosion composition of the present invention is applied to the surface of the foil itself or electrolytic paper. It is preferable to have it present, and when the purpose is to prevent corrosion of the lead material, the surface of the lead material itself or the back side of the sealing material (element side) is preferable.

It can also be present on the inner surface of the outer case.

In the case of electrolytic paper, it can be applied to both sides, the side in contact with the anode foil, and the side in contact with the cathode foil, but since halide ions are anions and easily corrode the anode foil, apply at least to the side in contact with the anode foil. This is desirable. When applied to electrode foil, anode foil is more effective than cathode foil for the same reason as above.

The composition of the present invention may be present in a capacitor as follows.

After applying the composition to the surface of electrode foil or electrolytic paper, the medium is removed by evaporation or the like to form a film, and this is used to form a capacitor element, in particular the composition using a paint vehicle. This is an effective method for

Alternatively, there are methods such as injecting the required amount into an already assembled capacitor element from the tip through a thin tube, or applying the composition to the tip of a stick and applying it to the desired location.

A commonly used thickener, antifoaming agent, crosslinking agent, etc. can be added to the composition of the present invention, if necessary.

[Effect]

Among the inorganic substances used in the present invention, the action of capturing halide ions by the inorganic anion exchanger is as follows.

When the inorganic anion exchanger is represented by R″O1+− and the halide ion is represented by the acid form of 11+X−, the formula is as shown in (Formula 5), and as a result, water is generated.

R"011-1-11"X-→R+X-+H20...
(Formula 5) The reaction that captures the above ions is an ion exchange reaction, but as a characteristic of inorganic ion exchangers, reverse reactions are difficult to occur. Special conditions are often required, and once ions are captured, they are generally not released.

This is the RX after the bond of R”OI+- becomes R”X-
This seems to be due to the strong covalent nature of the bond between them.

〔Example〕

Hereinafter, the present invention will be explained in more detail with reference to Examples and Comparative Examples. Note that "parts" on each side represent "parts by weight."

Examples 1 to 5 and Comparative Example 1 Dispersant (T-4 manufactured by Toagosei Kagaku Kogyo ■) in 100 parts of distilled water
0) 0.5 part was added, followed by the addition of 100 parts of lead hydroxyapatite as an inorganic substance while stirring.

Further, 21 parts of styrene-butadiene latex JSRO 668 (manufactured by Japan Synthetic Rubber Company) was added and mixed as a paint vehicle to obtain an anticorrosive composition.

In this composition, the ratio of vehicle was 10 parts (solids equivalent) to 10 parts of lead hydroxyapatite.

As shown in Table 1, the anticorrosive composition was applied to electrolytic paper or electrode foil using a barcoder.

An aluminum electrolytic capacitor was produced in a conventional manner using the electrolytic paper or electrode foil described in Example 1.

This capacitor was dissolved in 1.1.1-trichloroethane with 6
After immersion for 0 minutes, a life test was conducted by applying a voltage of 63 cm at 121°C.

After a predetermined period of time, the capacitors were disassembled and the corrosion incidence was examined (Examples 1 to 5).

An aluminum electrolytic capacitor was produced without using a separate anti-corrosion composition, and a life test was conducted under the same conditions (Comparative Example 1).

These results are shown in Table 2.

It should be noted that the corrosion incidence rate is the number of cases in which corrosion occurred among 20 capacitors tested in each example.

Examples 6 to 9 5 parts of dispersant T-400 was added to 142 parts of distilled water, and 100 parts of the inorganic substances listed in Table 3 were subsequently added while stirring.

Additionally, acrylic latex A1 is used as a paint vehicle.
An anticorrosion composition was obtained by adding and mixing 43 parts of 06 (manufactured by Toagosei Kagaku Kogyo ■).

In this composition, the ratio of vehicle was 20 parts (calculated as solid content) to 100 parts of inorganic material.

This composition was applied to both sides of electrolytic paper using a barcoder.

Thereafter, an aluminum electrolytic capacitor was produced in the same manner as in Example 1, and a life test was conducted.

These results are shown in Table 4.

In addition, among the inorganic substances listed in Table 3, hydrated antimony oxide is
It is a cation exchanger and has the ability to adsorb halogenide ions.

Table 3 Examples 10 to 11 To 100 parts of distilled water, 1.9 parts of the dispersant or surfactant shown in Table 5 was added, and while stirring, 5 parts of lead hydroxy abatide was added as an inorganic substance. By mixing, an anticorrosive composition was obtained.

This composition was applied to both sides of electrolytic paper using a barcoder.

Thereafter, an aluminum electrolytic capacitor was produced in the same manner as in Example 1, and a life test was conducted.

These results are shown in Table 6.

Table 6 (C) Effects of the Invention The anticorrosion composition of the present invention is excellent in preventing corrosion of aluminum in electronic components, and aluminum electrolytic capacitors using the composition have extremely high reliability as corrosion is prevented. .

[Brief explanation of the drawing]

FIG. 1 is a schematic explanatory diagram of an aluminum electrolytic capacitor element, and FIG. 2 is a schematic diagram of an aluminum electrolytic capacitor using this element. 1...Element body 2...Cathode foil 3...Anode foil 4...Electrolytic paper 5.6...Lead material

Claims (2)

[Claims] 1. Inorganic substances that have the ability to adsorb halide ions,
An anticorrosive composition for electronic parts, which is prepared by dispersing the composition in a solution or dispersion containing one or more selected from a surfactant, a dispersant, and a paint vehicle. 2. A capacitor comprising aluminum as a constituent element, wherein the anticorrosive composition according to claim 1 is present at one or more locations selected from electrolytic paper, aluminum foil serving as an electrode, a lead material, a sealing material, and an inner surface of an outer case.