JPS5853720B2 - How to treat anodized film - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for treating an anodic oxide film having high thermal conductivity, heat resistance, and electrical insulation.

Anodic oxide films on aluminum and aluminum alloys are metal oxide films chemically formed on the surfaces of these metals.
It is an electrically insulating film with a uniform structure, good adhesion to the underlying metal, and high thermal conductivity.

Recently, using the characteristics of this anodic oxide film, metal plates on which an anodized film has been formed have been used as printed wiring boards for electronic devices, ICs, etc.
, its use as a heat sink for LSI is being considered.

When using anodic oxide films for these applications, the film is made thick to improve insulation, but anodic oxide films with a thickness of several micrometers or more inevitably have many micropores. Occur.

These micropores are several hundred in diameter and reach the barrier layer of the anodic oxide film.

For this reason, in a thick anodic oxide film, a small amount of current flows due to moisture in the air or residual electrolyte during anodization, making it impossible to obtain sufficiently high insulation.

In order to improve this drawback, the micropores are sealed with steam or boiling water. However, when the pores are sealed, the oxide film deteriorates due to hydration, and the anodic oxide film changes even after being heated to around 150°C. There is a problem that cracks (crank) occur in the metal, resulting in a decrease in electrical insulation.

Another method is to form a resin film on the surface of the anodic oxide film to close the micropores, but although this method improves electrical insulation, it lowers thermal conductivity and causes problems such as problems with printed wiring boards and heat sinks as mentioned above. It is unsuitable when used as a

Furthermore, there is a method (Japanese Patent Publication No. 49-4719) in which an organic metal compound such as an organic silicon compound is deposited in the fine pores and on the surface of the oxide film by electric discharge using the anodic oxide film as a pole in a gas. Since this method utilizes a discharge phenomenon, it is impossible to control the deposition site of the organometallic compound, which makes it difficult to sufficiently fill the micropores, and the organometallic compound is not deposited densely. , Furthermore, there remains a path through which the current flows during discharge,
It has the disadvantage that its insulation properties tend to deteriorate due to the influence of moisture.

In addition, if a wiring board with an anodic oxide film is heated by heat from electronic components or heated during soldering, the anodic oxide film, which is an insulating layer, will crack and the wiring conductor will break. There are also disadvantages in that the circuit may be broken due to cracks, and moisture in the air may enter through the cracks, reducing electrical insulation.

The cause of cracks in the anodic oxide film is the large difference in thermal expansion coefficient between the anodic oxide film and the base metal.

For example, the coefficient of thermal expansion of aluminum is approximately 25X10'
On the other hand, the coefficient of thermal expansion of aluminum oxide, which is the main component of the anodic oxide film, is approximately 6×10', which is significantly different, and cracks occur due to thermal stress when heated.

This invention was made in view of the above circumstances, and aims to provide a treatment method capable of forming an anodic oxide film having high thermal conductivity, heat resistance, and electrical insulation. An aluminum-silicon alloy containing 20% by weight or less is anodized in an electrolytic bath containing a specific ammonium salt or sodium salt, and then polymerizable organic It is characterized by attaching and depositing a metal compound and then polymerizing it.

The present invention will be described in detail below.

In this invention, an aluminum-silicon alloy is used.

This aluminum-silicon alloy is an aluminum alloy with a silicon content of 20% by weight or less, and contains only impurities or a small amount of additives in addition to silicon. It has a property that its thermal expansion coefficient decreases as the silicon content increases.For example, when the silicon content is 11% by weight, the thermal expansion coefficient is 19.7XIO-6.

Due to this property, the difference in coefficient of thermal expansion between the anodic oxide film of this alloy and the base alloy is alleviated, and heating cracks are less likely to occur compared to the anodic oxide film of pure aluminum.

In addition, in this alloy, Si particles are dispersed in the aluminum continuous phase. When this alloy is anodized, the Si particles remain in the oxide film, which has the effect of preventing cracks from occurring or reducing the size of cracks. be.

It should be noted that if the silicon content exceeds 20% by weight, the insulation properties of the oxide film will be drastically reduced, causing problems.

This aluminum-silicon alloy is then anodized.

This anodizing treatment is carried out in an electrolytic bath containing ammonium tartrate, ammonium hydroxide, ammonium carbonate, ammonium fluoride salt or sodium hydroxide, sodium salt of sodium pyrophosphate.

The ammonium ion concentration in the electrolytic bath is 5? /l~80?
/l, and the sodium ion concentration is 11/l ~ 30P
/7 is suitable.

The bath temperature ranges from 5℃ to 40℃, and the current density is 0.5A.
/dm to 2OA/dm.

The anodic oxide film obtained by anodizing in such an electrolytic bath and electrolytic conditions has a high crank generation temperature.
Improves heat resistance.

Table 1 shows the results of anodic oxidation using an aluminum-silicon alloy with a silicon content of 4.5% by weight, using an aqueous ammonium tartrate solution as an electrolytic bath, and varying the current density and bath temperature. Indicates the temperature at which cracks occur in the film.

As is clear from Table 1, the anodic oxide film obtained by anodic oxidation in an electrolytic bath with the above composition has no cracks up to 400°C over a wide range of bath temperatures and current densities, and is extremely heat resistant. It turns out that it is excellent.

The aluminum-silicon alloy on which the anodic oxide film has been formed is then treated with a polymerizable organometallic compound.

The polymerizable organometallic compound used here is a polymerizable compound in which an organic group that can be hydrolyzed into a metal atom, a rogene group, and an organic functional group are bonded.

And the general formula % formula % X: Biyl group, amino group, mercapto group, epoxy group,
Organic functional group R such as a methyl group or phenyl group: an organic metal compound represented by a hydrolyzable organic group such as an alkoxy group or an acetoxy group and a halogen group n+m=3.4.5 or 6, such as phenyltriethoxy Silane, methyltriethoxysilane, hinyltris(β-methoxyethoxy)silane, β-(3.4
-Organosilicon compounds such as -epoxy-cyclohexyl)ethyltrimethoxysilane, γ-glycidoxypropyltrimethoxysilane, tetraisopropyl bis(dioctylphosphite) titanate, tetraoctylbis(ditridecylphosphite) titanate, titanium acetylacetate Organotitanium compounds such as ester, titanium octylene glycolate, dihydroxybis(lactato)titanium, and tetrastearoxytitanium, organoaluminum compounds such as aluminum tri-n-butoxide, methylaluminum sesquichloride, and aluminum triisopropoxide, zirconium tetra-n -butoxide,
Organometallic compounds such as organic zirconium compounds such as zirconium tetrane propoxide, derivatives of these compounds, and low polymers (oligomers) can be used, but those having methyl groups and/or phenyl groups in the organic functional groups can be used. , is preferable because the improvement in heat resistance is greater.

Furthermore, it is better if hydrolysis occurs gradually.

These polymerizable organometallic compounds are used after being dissolved in an organic solvent such as methanol, ethanol, acetone, ethyl acetate, or methyl ethyl ketone, water, or a mixture of water and a water-soluble organic solvent.

As the solvent for this water-soluble cloth, methanol, ethanol, impropatol, acetone, dioxane, ethylene glycol, methyl acetate, methyl ethyl ketone, diacetone alcohol, ethyl formate, dimethyl formamide, etc. are used, and if necessary, Additives such as surfactants can be added.

Then, the anodic oxide film is immersed in such a polymerizable organometallic compound solution to diffuse and permeate the polymerizable organometallic compound into the micropores, or the solution is applied to the oxide film surface. This is carried out by forming a polymerizable organometallic compound layer or by using a vacuum impregnation method.

Alternatively, the oxide film is immersed in a solution in which a polymerizable organometallic compound is dissolved in water or a mixture of water and a water-soluble organic solvent, and a direct current is applied using the oxide film as an anode and a suitable inert conductor as a cathode. By applying electricity, the polymerizable organometallic compound can be sufficiently impregnated from the bottom to the opening of the micropores of the oxide film by migration, penetration, etc.

When the resulting anodic oxide film requires higher thermal conductivity, the polymerizable organometallic compound solution adhering to the oxide film surface is completely wiped off, and when higher electrical insulation is required, the oxide film The polymerizable organometallic compound solution adhering to the surface is left as it is without being wiped off.

Once the polymerizable organometallic compound has been sufficiently attached and deposited on the surface or micropores of the anodic oxide film, the oxide film is dried and excess water and organic solvent are removed.

The polymerizable organometallic compound attached to or deposited on the surface of the anodic oxide film or in the micropores as described above is polymerized by a polymerization means such as heating.

Through this polymerization, the polymerizable organometallic compound becomes a dense organometallic compound polymer, and since these organometallic compounds have a high affinity with the oxide film, the surface of the oxide film,
It firmly adheres to the inside of the pore, filling the inside of the fine pore tightly or covering the surface.

In the anodic oxide film treated with the polymerizable organometallic compound as described above, the micropores are virtually filled with the organometallic compound polymer, or the film surface is also coated with the polymer, resulting in extremely high electrical insulation. You can get sex.

Furthermore, since only the micropores can be filled with the polymer, electrical insulation is improved while maintaining high thermal conductivity.

Furthermore, electrical insulation properties at high temperatures (approximately 150° C.) are also improved.

Furthermore, since the filled and coated polymer is metallic, the polymer itself has excellent thermal conductivity, and the anodic oxide film whose surface is coated with this polymer also has high thermal conductivity.

Hereinafter, this invention will be specifically explained based on Examples.

Example 1 100mm x 50mm x 2mm silicon content 4.5
% AI-Si alloy plate, ammonium tartrate (NH4)2C4H4o, o, IM/l, ammonium hydroxide NH,OH2,3M#', ammonium carbonate (NH4)2CO30, IM/l, fluoride Four types of electrolytic baths consisting of an aqueous solution of ammonium chloride NH4F0.3M/A were used, each with a bath temperature of 15°C and a current density of 2.
Anodic oxidation was performed under conditions of 12 μm in thickness to form an anodic oxide film with a thickness of 12 μm.

These four types of anodic oxide films are used as anodes, and H8C2H45
1 (OC2H5)3 50%, ethanol 49%, water 1
% mixed solution for 30 minutes at a constant DC 500μ,
A polymerizable organometallic compound was impregnated into the anodic oxide film, and after thoroughly wiping off the solution adhering to the sample surface, it was dried with hot air and heated at 130° C. for 2 hours to polymerize.

When a mercury droplet with a diameter of 57n7IL was placed on the obtained anodic oxide film and the dielectric strength voltage between it and the base aluminum plate was measured, a dielectric strength voltage of 200 V or more was obtained in all cases.

These samples were heated at 300° C. for 30 minutes, but no cracks were observed in the films, and there was no deterioration in insulation properties.

Further, these samples were left indoors for one week, and then the dielectric strength was measured, and no deterioration in electrical insulation properties due to the influence of humidity was observed.

Example 2 100 mm x 50 mm x 2 mm silicon content 11% AI
-8i series alloy plate, hydroxide) IJumN
aOH0.2M/l, sodium pyrophosphate Na4
Using two types of electrolytic baths consisting of aqueous solutions of P2O70 and 75M/7, anodization was carried out at a bath temperature of 15° C. and a current density of 2 A/dm'' to obtain an anodic oxide film with a thickness of 10 μm.

These two anodic oxide films were vacuum impregnated in a mixed solution of 250% (C3H70)2Ti(C5H003) and 50% isopropanol to impregnate the polymerizable organometallic compound into the micropores.

Thereafter, the film was treated in the same manner as in Example 1, and the dielectric strength voltage of the film was measured, and a withstand voltage of 150V was obtained in each case.

Furthermore, no cracks were observed in the film even after heating at 300°C for 30 minutes.

Example 3 Al with silicon content of 11%, 100 mm x 50 mm x 2 mm
-8i alloy plate was anodized in the same manner as in Example 1,
It was treated in the same manner as in Example 2 in a mixed solution of 260% CH3A1 (C4H90) and 40% Improper Tool.

When the dielectric breakdown voltage of the film was measured in the same manner as in Example 1, a breakdown voltage of 150V was obtained in all cases.

Further, even when this sample was heated at 300° C. for 30 minutes, no cracks were observed in any of the anodic oxide films.

Example 4 A 12 μm thick anodic oxide film obtained in the same manner as in Example 1 was impregnated with zirconium tetraisopropoxide into the fine pores of the oxide film by vacuum impregnation, and left in the air for 24 hours to add water. After decomposition, polymerization was carried out by heating at 130° C. for 2 hours.

When the AC dielectric strength voltage of these samples was measured in the same manner as in Example 1, it was found to be 500V or more.

Furthermore, no cracks were observed in these samples even after heating at 300° C. for 30 minutes.

As explained above, the method for treating an anodic oxide film of the present invention includes anodizing an aluminum-silicon alloy plate having a silicon content of 20% by weight or less in an electrolytic bath containing a specific ammonium salt or sodium salt. Next, a polymerizable organometallic compound is attached and deposited on the micropores and surface of the obtained anodic oxide film, and then polymerized, so the temperature at which cracks occur in the anodic oxide film increases, and the occurrence of cracks almost disappears. It has extremely high heat resistance, and the insulation properties of the anodic oxide film at high temperatures are also greatly improved.

Furthermore, since the fine pores of the anodic oxide film are densely filled with the organometallic compound polymer, high electrical insulation properties can be obtained.

Therefore, the anodized film treated according to the present invention can be used for printed wiring boards, insulating heat sinks, heat-resistant insulated wires, etc.

Claims (1)

[Claims] 1. An aluminum-silicon alloy having a silicon content of 20% by weight or less, ammonium tartrate, ammonium hydroxide,
Anodized in an electrolytic bath containing at least one of ammonium carbonate and ammonium fluoride or one or more of sodium hydroxide and sodium pyrophosphate.
General formula (wherein M: Si, AI, Ti, Zr X: vinyl group, amino group, mercapto group, epoxy group,
Organic functional group R such as methyl group and phenyl group: Hydrolyzable organic group such as alkoxy group and acetoxy group and halogen group n+m=3.4.5 or 6. ) A method for treating an anodic oxide film, characterized by impregnating and adhering a polymerizable organometallic compound represented by the following formula, followed by polymerization.