JPS5922396B2 - Printed wiring board manufacturing method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a printed wiring board having high heat dissipation, heat resistance, and electrical insulation.

In recent years, as electronic components such as ICs, LSIs, and printed wiring boards have become more dense, power consumption has increased and a large amount of heat has been generated.

Such a temperature rise causes a reduction in the reliability and lifespan of circuit components. Various heat dissipation methods have been devised to solve this problem, but among them, a method that uses a highly thermally conductive metal such as aluminum as a substrate and uses the anodic oxide film of this metal as an insulator is a method that increases the substrate strength. V) It is attracting attention as an extremely effective method. In this method, for example, after sealing the alumite film, a wiring conductor such as copper foil is attached to the surface of the alumite film using an adhesive several tens of micrometers thick. Therefore, the biggest advantage of metal substrates, heat dissipation and heat resistance, was not fully utilized. By the way, in order to quickly conduct heat from electronic components and the like to the substrate metal for heat dissipation, it is desirable to form an organic layer on the anodic oxide film as little as possible.

However, since a large number of micropores exist in the anodic oxide film in the thickness direction of the film, sufficient electrical insulation cannot be obtained even if a wiring conductor is directly formed therein. This is because when a wiring conductor is formed on an oxide film by wet chemical plating, the plating solution enters into the micropores and becomes electrically conductive with the base metal. Therefore, in order to simultaneously satisfy the heat dissipation and insulation properties of the substrate, it is conceivable to close the micropores in the oxide film. This method first includes pore sealing treatment. The pore sealing process uses high-pressure steam or boiling water to hydrate and alter the oxide film, causing it to expand in volume and close the micropores. Since the deep part is difficult to be blocked and volumetric expansion occurs from the periphery of the hole, a minute void remains at the center of the fine hole, making it impossible to completely prevent the plating solution from entering. Furthermore, when this pore sealing treatment is carried out, the anodic oxide film has a serious drawback in that it is susceptible to cracking due to slight heating. The next method could be to impregnate the micropores with resin, but since the micropores are extremely small, a few hundred amps in diameter, and several tens of microns deep, it is difficult to completely fill the pores due to problems such as the viscosity of the resin. It is virtually impossible to impregnate the deepest part.
This invention was made in view of the above circumstances, and has heat dissipation,
The purpose is to provide a method for manufacturing printed wiring boards with excellent heat resistance and electrical insulation, and the gist is to anodize the surface of a metal plate that can be anodized, with holes for mounting parts, through holes, etc. drilled in advance. A film is formed, and then a polymerizable organometallic compound is attached and impregnated on the surface of this anodic oxide film, in the micropores, through holes, etc., and after polymerization, a wiring conductor is formed directly on the surface of this anodic oxide film. It is characterized by:

This invention will be explained in detail below.

The metal plate used in this invention is anodized with metals that can be anodized such as aluminum, titanium, tantalum, magnesium, etc. or alloys of these metals, and an anodized film made of oxides of these metals is formed on the surface of the metal plate. can be formed.

This metal plate is pre-drilled with holes such as component mounting holes for attaching electronic and electrical components and through holes for forming electronic circuits. These metal plates are then anodized. The anodic oxidation treatment is generally performed using an ordinary electrolytic bath such as oxalic acid or sulfuric acid, and an anodic oxide film having a thickness of 5 to 200 μm is formed. The metal plate on which the anodic oxide film has been formed is then treated with a polymerizable organometallic compound. Furthermore, if necessary, the above-mentioned treatment can be performed after a sealing treatment using high-pressure steam, boiling water, etc. is performed. This polymerizable organometallic compound is one in which a hydrolyzable group, a halogen group, or an organic functional group is bonded to a metal atom.
It has polymerizability. Such a general formula XnMR
m M: SixTixAl, , ZrsGe, . B.. P.
Metal atoms such as Sn.

X: Organic functional group such as vinyl group, amino group, mercapto group, epoxy group, etc.

R: Hydrolyzable organic group such as an alkoxy group or an acetoxy group.

Examples of organometallic compounds represented by n+m=3,4,5 or 6 include phenyltriethoxysilane, methyltriethoxysilane, vinyltris(β-methoxyethoxy)silane, β-(3,
Organosilicon compounds such as 4-epoxy-cyclohexyl)ethyltrimethoxysilane, r-glycidoxypropyltrimethoxysilane, tetraisopropyl bis(dioctyl phosphite) titanate, tetraoctyl bis(ditridecyl phosphite) titanate, titanium acetylacetate Organic titanium compounds such as aluminum tri-n-butoxide, methylaluminum sesquichloride, aluminum tripropoxide, tetra(n-butoxy ) Organic zirconium compounds such as zirconium and zirconium tetraisopropoxide, organic phosphorus compounds such as tri-n-butyl phosphate and diethyl phosphite, tri-(n-butyl) borate, triisopropyl borate, etc. Organic boron compounds, organic germanium compounds such as dimethyloxydimethylgermanium and methylgermanium trimethoxide, and organometallic compounds such as dimethyloxyethyltin, derivatives of these compounds, and low polymers (oligomers) can be used. However, those having a methyl group and/or phenyl group in the organic functional group are preferable because they have a greater improvement in heat resistance.

Further, it is more preferable that hydrolysis occurs gradually.
These polymerizable organometallic compounds are 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. Examples of this water-soluble organic solvent include methanol, ethanol, isopropanol, acetone,
Dioxane, ethylene glycol, methyl acetate, methyl ethyl ketone, ethyl formate, diacetone alcohol, dimethyl formamide, etc. are used, and additives such as surfactants can be added thereto as necessary. Subsequently, the anodic oxide film is treated with this polymerizable organometallic compound solution.

In this treatment, the anodic oxide film is immersed in the solution to diffuse and infiltrate the polymerizable organometallic compound into the micropores, etc.
This is carried out by applying the solution to the surface of the oxide film to form a polymerizable organometallic compound layer on the surface of the oxide film, 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 into the surface of the oxide film from the bottom of the fine pores to the pore openings, the surface of the oxide film, and the through-holes by electrophoresis, permeation, etc. When higher thermal conductivity is required for the resulting printed wiring board, the polymerizable organometallic compound solution adhering to the surface of the oxide film is completely wiped off, and when higher electrical insulation is required, the oxide film is removed. The polymerizable organometallic compound solution adhering to the surface is left as it is without being wiped off. Once the polymerizable organometallic compound is sufficiently attached and deposited on the surface of the anodic oxide film, micropores, through holes, etc.,
Drying removes excess water and organic solvents. The polymerizable organometallic compound adhered to and deposited on the surface of the anodic oxide film, micropores, through holes, etc. 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 these organometallic compounds have a high affinity with the oxide film, so they firmly adhere to the surface pores of the oxide film and form fine particles. Fill holes etc. thoroughly. According to this method, insulation of the inner walls of parts mounting holes etc. can be performed without any problem.

Since the anodic oxidation treatment has good throwing power, an oxide film is evenly formed on the inner surface of the hole. This is because in the case of anodic oxidation, the resistance increases in areas where the oxide film has grown thicker, so current tends to flow to areas where the film is thinner and has less resistance. As a result, the uniformity of the film tends to increase. In addition, when impregnating an organometallic compound by applying electricity, as the impregnation progresses, the resistance gradually increases and it becomes difficult for the current to flow, so that the current flows through the parts where the impregnation is relatively slow. Therefore, the impregnation is performed uniformly, so that the inner surface of the component mounting hole is also sufficiently impregnated. Subsequently, a wiring conductor is formed on the surface of the anodic oxide film to which the organometallic compound polymer is attached and impregnated.

This can be done by directly forming a circuit by electroless plating, vapor deposition, ion sputtering, ion plating, etc., or by first forming a thin metal layer and then forming a thin layer with a thickness of several 1.
A wiring conductor of 0 μm copper, nickel, etc. is formed, and the desired printed wiring board is obtained. As an example of the printed wiring board thus obtained, FIGS. 1 and 2 show one in which an aluminum plate is used as the anodizable metal plate.

FIG. 1 shows that only the micropores 3 of the alumite film 2 on the surface of the aluminum plate 1 are filled with an organometallic compound polymer 4.
A wiring conductor 5 is formed on the surface of an alumite film 2. In FIG. 2, an organometallic compound polymer film 6 is formed on the surface of the alumite film 2, and a wiring conductor 5 is formed on the surface of this polymer film 6. This is what I did. In the anodic oxide film treated with the polymerizable organometallic compound in the manner described above, the micropores, etc. are completely filled with the organometallic compound polymer, the film surface is also covered with the polymer, and the through holes etc. are also covered. Since it is treated in the same way, extremely high electrical insulation properties can be obtained.

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. In addition, since the filled and coated polymer is metal-based, the polymer itself has excellent heat conductivity, and the oxide film covering the surface has a higher heat conductivity than the conventional oxide film coated with resin. properties, and improves heat dissipation. Hereinafter, this invention will be specifically explained based on Examples.

Example 1 A hole with an inner diameter of 111φ and a semicircular edge in the cross section in the depth direction was drilled at a predetermined position in a 2SAI plate measuring 100m1 x 50Tn1L x 2111L, electrolyzed in a 15% sulfuric acid aqueous solution, and a hole with a thickness of 30μ was made. The alumite film was chemically converted.

After drying, CH2=CHSi(
A 20% ethanol solution of 0C2H40CH3)3 was applied, dried at room temperature, and then heated and polymerized at 130° C. for 2 hours to form an organometallic compound polymer film with a thickness of about 10 μm. This sample was immersed in a 0.5 V/l aqueous solution of palladium chloride for 10 minutes at room temperature while masking the parts other than the circuit part.
Activation treatment was performed, and then electroless nickel plating was performed to form a wiring conductor on the polymer film. Then, after washing with water and drying, the AC dielectric strength voltage between the base aluminum and the wiring conductor was measured, and a value of 1 KV or more was obtained. Further, when circuit components were soldered to this board and the dielectric strength was measured after leaving it indoors for a week, no deterioration in insulation properties due to soldering or humidity was observed. Example 2 Example 1
An alumite film with a thickness of 30 μm was formed on the 2SAI plate in the same manner as above, and after washing with water, CH2=CHSi (0C2H40C
H3) In a 4% aqueous solution of 3, this alumite film was used as an anode and the insoluble conductor was used as a cathode, and a DC current of 25 mA/Dm2 was applied.
After being energized for 2 hours at an initial voltage of 250 V, it was taken out from the aqueous solution, the aqueous solution adhering to the surface of the alumite film was thoroughly wiped off, and then dried with hot air, and then heated for 2 hours at 13"C to polymerize.

This sample was treated in the same manner as in Example 1 to form a wiring conductor on the surface of the alumite film, and when the AC dielectric strength voltage was measured, a withstand voltage of 800V was obtained. In addition, after soldering components to this board and leaving it indoors for a week, we measured the dielectric strength voltage between the base aluminum and the wiring conductor again, and no deterioration in insulation was observed due to the effects of soldering or humidity. Ta. Furthermore, when a cross section of this sample was analyzed using an X-ray microanalyzer, it was confirmed that the organometallic compound was impregnated to the deepest part of the micropores of the alumite film, as shown in Figure 3. . Example 3 A 30 μm thick alumite film was formed on a 2SA1 board in the same manner as in Example 1, and then phenyltriethoxysilane (C6H5Si(0C2H5) 350v01%,
In a solution of 49.6% isopropanol and 0.4v01% water, the alumite film was used as an anode and aluminum was used as a cathode, and current was applied at 500 V DC for 1 hour.

At this time, the current was initially about 10 mK/Dm2. The end was approximately 6 mA/Dm2. After energizing, take out the alumite film from the solution, thoroughly wipe off the solution adhering to the surface of the alumite film, dry it with hot air, and heat it to 130°C.
After heating and polymerizing for 2 hours, a wiring conductor was formed on the surface of the alumite film in the same manner as in Example 1, and the AC dielectric strength voltage was measured and found to be 1.1 KV or more. Also, the volume resistivity at room temperature is approximately 4X1012Ω? , 150℃
So about 6×1011Ω? It was hot. Furthermore, after parts were soldered to this board and left indoors for a week, no deterioration in board performance was observed. When ray analysis was performed using an X-ray microanalyzer in the same manner as in Example 2, it was confirmed that the organometallic compound was impregnated to the deepest part of the micropores of the alumite film. Example 4 Continuing with Example 1, titanium octylene glycolate (
Vacuum impregnation was performed using a 50% ethanol solution of C4H,O)2Ti (C8Hl6O2).

Subsequently, the adhering liquid was removed from the surface, and after drying at room temperature, heating polymerization was performed at 130° C. for 2 hours. When the AC dielectric strength voltage of this board was measured, it was approximately 800V. Example 5 CH3 in place of the polymerizable organometallic compound in Example 4
A substrate was obtained by performing similar treatment using Al(C4H,O)2.

When similar tests were conducted on this board, Example 4
obtained similar results. Example 6 An aluminum plate with a thickness of 301 t was prepared in the same manner as in Example 1.
An anodic oxide film of CH2=CHSi(0
It was immersed in a 20v01% ethanol solution of C2H40CH3)3 and left for 1 hour, and this solution was diffused into the micropores.
Infiltrated.

The anodic oxide film was taken out from the solution, the solution adhering to the surface was thoroughly wiped off, and then heated at 150° C. for 2 hours to polymerize. A wiring conductor was formed in the same manner as in Example 1, and when the AC dielectric strength voltage of this wiring board was measured, a value of 500 V or more was obtained. Example 7 100x50x111 magnesium alloy plate (JISl
seeds), acidic ammonium fluoride 300t/11 sodium dichromate 100r/11 phosphoric acid (85%) 90T
! Ll! Anodic oxidation treatment was carried out for 50 minutes at a bath temperature of 75°C and a current density of 5A/Dm2 in an aqueous solution containing 3.0% of
A 0 μm anodic oxide film was obtained.

Next, this film was coated with methyltriethoxysilane 85v0.
In a solution of 1% ethanol, 5v01% ethanol, and 10v01% water, the film was energized for 1 hour at 1KV DC and 15mA using the film as an anode, and then heated at 150°C for 2 hours. A wiring conductor was formed on this treated magnesium alloy plate in the same manner as in Example 1. The AC insulation voltage of this wiring board is 70
It was 0V or more. Example 8 Five 100 x 50 x 1 mm 2S aluminum plates were each anodized in a 17 wt % oxalic acid aqueous solution at a bath temperature of 20° C. and a current density of 2 A/Dm 2 to form an anodic oxide film with a thickness of 30 μm.

Next, for each film, zirconium tetraisopropoxide, tri-n-butyl phosphate, tri-n-butyl borate, methylgermanium trimethoxide, and dimethyloxyethyltin were applied to the micropores of the film under vacuum. Impregnated. Next, the mixture was left in the air for 24 hours to perform hydrolysis, and then heated at 130° C. for 2 hours to polymerize. Then, a wiring conductor was formed on this treated aluminum plate in the same manner as in Example 1. The AC dielectric strength voltage of this wiring board was 500V or more. As explained above, the method for manufacturing a printed wiring board of the present invention involves forming an anodized film on the surface of an anodizable metal plate in which component mounting holes and through-holes have been drilled in advance; A polymerizable organometallic compound is attached to and impregnated on the surface, in micropores, and through holes, etc., and then polymerized, and then a wiring conductor is formed directly on the surface of this anodic oxide film. Since the fine pores are also filled with a sufficient amount of the organometallic compound polymer, high insulation properties and prevention of heating cracks can be obtained, making it possible to form wiring conductors directly on the oxide film or polymer film. However, it has the advantage of greatly improved heat dissipation.

[Brief explanation of the drawing]

Figures 1 and 2 show examples of printed wiring boards obtained by the present invention. Figure 1 shows one in which only the micropores of the alumite film are filled with organometallic compound polymer;
Figure 2 is a schematic cross-sectional view showing an organometallic compound polymer film formed only on the surface of the alumite film, and Figure 3 is an X-ray micrograph showing that the organometallic compound polymer is filled in the micropores of the alumite film. This is a measurement chart showing the results of line analysis by an analyzer.
The I line shows the distribution of Si. 1... Aluminum plate 2... Alumite film, 3
... Micropore, 4... Organometallic compound polymer, 5.
- Wiring conductor, 6... Organometallic compound polymer film.

Claims (1)

[Claims] 1. An anodic oxide film is formed on the surface of a metal plate that can be anodized with holes such as component mounting holes and through holes, and then a polymerizable film is formed on the surface of this anodic oxide film and/or in the micropores as well as in the holes. A method for manufacturing a printed wiring board, which comprises depositing, impregnating and polymerizing an organic metal compound, and then forming a wiring conductor, etc.