JPH01173688A - Manufacture of board for integrated circuit - Google Patents

Abstract

PURPOSE:To improve electrical insulating performance by a method wherein an adhesive varnish composed of a solid resin composition, an inorganic filler and a solvent is applied to the surface of a metal foil sheet and is dried, this process is repeated and a face coated with the adhesive varnish is then pasted onto a metal sheet. CONSTITUTION:An adhesive varnish composed of a solid resin composition, an inorganic filler and a solvent is applied to the surface of a metal foil sheet and is dried. Then, after this coating and drying operation has been repeated at least once, a pinhole does not exist substantially in an adhesive varnish layer formed on the surface of the metal foil sheet. Then, a face coated with the adhesive varnish of the metal foil sheet is pasted onto a metal sheet; after that, the adhesive varnish is hardened; a metal base board is obtained. By this setup, the reliability of insulating performance can be improved.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a method for manufacturing a metal base substrate used for hybrid integrated circuits and printed circuits with high heat generation density. In particular, the present invention relates to a method for manufacturing a metal base substrate having an insulating layer that has electrical insulation, thermal conductivity, and adhesive properties and contains a large amount of a highly heat conductive and highly insulating inorganic filler such as alumina.

[Prior art]

Substrates for hybrid integrated circuits generally consist of a metal substrate made of aluminum, iron, iron-silicon alloy, etc., with an adhesive layer several tens of microns thick made of an organic polymer compound such as epoxy resin, and then! A conductive metal foil such as M foil is attached.

Various metal-based substrates have been proposed in the past (for example, Japanese Utility Model Publication No. 46-25756, Japanese Unexamined Patent Publication No. 5
6-62388, JP-A-58-15290), however, there are problems such as insufficient adhesiveness of the adhesive layer (and unsatisfactory electrical insulation and thermal conductivity). Ta.

[Purpose of the invention]

The present invention provides a method for manufacturing an integrated circuit substrate that has good electrical insulation, thermal conductivity, and adhesion, and is particularly excellent in electrical insulation, that is, has a uniformly high withstand voltage over a wide range. With the goal.

[Structure of the invention]

For this reason, in the present invention, an adhesive varnish consisting of a solid resin composition, an inorganic filler, and a solvent is applied to the surface of the metal foil, dried, and then this application and drying are repeated once (both once). The gist of the present invention is a method for manufacturing an integrated circuit board, characterized in that the surface of the metal foil coated with an adhesive varnish is adhered to a metal plate.

Hereinafter, the configuration of the present invention will be explained in detail.

(1) Adhesive varnish.

It consists of a solid resin composition, an inorganic filler, and a solvent. These blending ratios are not particularly limited. Other additives may be included as necessary.

■Resin composition.

It is solid. Solid refers to a solid having a softening point of 40°C or higher, preferably 60°C or higher. It is essential that it is solid so that it does not become sticky after the solvent dries. As a result of being solid, it is easy to handle the adhesive-coated metal foil after the solvent dries (for example, it can be rolled up as is), and there is no adhesion of foreign substances such as dust. In addition, in the recoating process, the same effect can be achieved without using the B-stage process of conventional technology, such as by simply repeating the coating and drying processes, so it is practical to use a solid resin composition. It is an essential element in invention.

Although the resin constituting the resin composition is not particularly limited, it is preferable to use a non-condensable thermosetting resin. A non-condensing thermosetting resin means a thermosetting resin that does not generate a creation gas, such as an epoxy resin or an acrylic resin. Phenol resins, imide resins, etc. are undesirable because they emit gases such as water and alcohol during boat fishing. However, even in these cases, this does not apply if the preliminary reaction is carried out so that by-product gases are not generated and the amount generated is very small.

The resin composition herein refers to the components of the adhesive varnish used, excluding the solvent and inorganic filler, and includes all organic materials remaining on the coating film.

Taking the case of compounding an epoxy resin as an example, in addition to the epoxy resin and curing agent, various additives commonly used in epoxy resin compositions (polymer, oligomer, coupling agent, diluent, This includes mixtures of all additives (flame retardants, rheology modifiers, curing aids), etc.

■ Inorganic filler.

It is an inorganic powder with high insulation (volume resistivity) and high thermal conductivity, such as Be01A1z03,
BN etc. are particularly excellent in performance. However, in today's Japan, considering toxicity, price, and supply,
Only Alz(h is practical.

Even if we focus on Al2O3, the particle morphology under a microscope, the pH1 purity when made into a water slurry, the particle size distribution, and the surface physical properties (whether it is a cleavage plane or a particle surface by Bayer method) greatly differ. ) etc., and the current situation is that even one A1□03 manufacturer has hundreds of brands available. For this purpose, a material with high purity, appropriate particle size distribution, surface physical properties, and price may be selected. In short, the Ah03 brand and content can be determined by comparing the cost of A11bi with the required performance and price, and the present invention provides a large degree of freedom in this selection.

Although it is possible to use a filler that has been treated with a silane coupling agent, it is preferable to use the integral blend method, which is cheaper than the filler, as it can provide the same performance.

■? Compatibility The solvent evaporates during the drying process and does not remain in the product.

Further, the solvent is essential for bringing the object to be coated into a coatable state (that is, in a liquid state). A mixture of a resin composition and a solvent has a viscosity as low as several tens of cps even when the solids content is around 70%, and a filler can be easily mixed therein using an ordinary propeller stirrer, and a coupling agent can be mixed therein. If it is included as a component of the resin composition, wet treatment, which is expected to be the most effective surface treatment method, becomes possible without any special effort.

Note that the adhesive varnish can be filtered if necessary, but this is only because the varnish has been reduced to an appropriate viscosity by the solvent.

(2) In the present invention, the adhesive varnish thus prepared is applied to the surface of a metal foil such as copper foil and dried. In this case, for example, if the adhesive is continuously applied onto an electrolytic copper foil and then wound up as it is through a drying oven, an adhesive-coated copper foil with a stable coating thickness and stable performance with few pinholes can be obtained.

The types of coaters that can be used include a doctor blade, comma coater, reverse coater, and gravure coater. Which coater is best?
Depending on the rheology of the varnish, it can be adapted to best suit existing coaters by adjusting the amount of solvent accordingly.

Next, in the present invention, this application and drying are repeated at least once. It is preferable to repeat once or twice. This substantially eliminates the presence of pinholes in the adhesive varnish layer formed on the surface of the metal foil.

Next, the adhesive varnished surface of the metal foil is adhered to a metal plate made of aluminum, iron, or the like.

Thereafter, by curing the adhesive varnish, a metal base substrate can be obtained.

Examples and comparative examples are shown below.

Examples, comparative examples (1) Example.

The adhesive varnish was manufactured according to the following recipe.

Aromatic diamine 12 parts by weight Silane coupling agent 1 part by weight AbOs
565 parts by weight solid epoxy resin is 1
Bisphenol A type epoxy resin containing 4% polybutadiene acrylonitrile skeleton, softened at 70℃,
The epoxy equivalent is about 500 g/eq, but 70% 2-
Since a butanone solution is used, 100 parts by weight is the solid epoxy resin and the remaining 43 parts by weight is the solvent (2-butanone).

Aromatic diamine is a curing agent for epoxy resin, and is used in a stoichiometric amount according to conventional methods.

The silane coupling agent is A11 (h is used here because it is particularly effective.Ah03 has an average particle size of 4.5
It is micron-sized Mader alumina. Rearranging this recipe, the resin composition corresponds to a total of 113 parts by weight of solid epoxy resin (100 parts by weight), aromatic diamine (12 parts by weight), and silane coupling agent (1 part by weight). . The amount of Al2O3 was 565 parts by weight, which was exactly 5 times the amount of the resin composition. The remaining 63 parts by weight is 2-butanone, ie, solvent. From this, the component of the insulating layer is Al2
This means that O3 is 83% by weight and the remaining 17% by weight is the organic matter of the resin composition. This makes each specific gravity 4.0
When converted by 1.2, AIJ3 has a capacity of 59%. These raw materials are placed in an ordinary stirring pot as shown in Figure 1 and stirred. When the powder and other ingredients are mixed well, the varnish is removed from the pot. At this time, if you pass it through a strainer of about 200 to 300 mesh,
Even if Ah03 is clumped, it can be removed. In this way, a varnish of 40,000 to 50,000 cps is obtained. In addition, in Fig. 1, 1 is a motor, 2
3 represents the pot, 3 represents the raw material, 4 represents the propeller, and 5 represents the extraction port.

Once the varnish is prepared, it is then applied to a 35 μm thick copper foil and the solvent is dried. FIG. 2 shows a device for this purpose. Application is performed using a doctor blade, and the application thickness is controlled by the blade cap.

In FIG. 2, 11 represents a copper foil unwinding part, 12 a doctor blade, 13 a drying oven, and 14 a winding part of the steel foil coated with adhesive varnish.

Two coating layers of 100 μm in total, 50 μm after the solvent dries in the first coating and an additional 50 μm in the second coat after the solvent dries.
Obtained in one application. The thus obtained adhesive-coated foils were temporarily pasted together with a heat roll to a thickness of 1.0 fl, and heated in an autoclave at a maximum temperature of 180°C in an isotropic pressure field of 10 kg/cJO for about 2 hours. It was cured using a cure cycle to obtain an aluminum-based copper-clad laminate.

The manufacturing process of the metal base substrate thus obtained is shown in Table 1, and its performance is shown in Table 2.

(2) Comparative example 1゜ An adhesive varnish was manufactured according to the following formulation.

Liquid epoxy resin 100 parts by weight Aromatic diamine 24 parts by weight Silane coupling agent 1 part by weight Al103625 parts by weight The liquid epoxy resin is a bisphenol A type epoxy resin containing 14% polybutadiene acrylonitrile skeleton, and has a viscosity of approximately 1. .20,000 cps (25°C), epoxy equivalent approximately 250 g/eq. As in the examples, the aromatic diamine is used in a stoichiometric amount.

Note that, since the aromatic diamine is solid, a portion of the liquid epoxy resin was heated to about 90° C. and dissolved therein to homogenize it. The same silane coupling agent was used in the same amount as in the example. ^1203 has an average particle size of 16μ
m and an average particle size of 32 μm were used in a weight ratio of 1:1, and prior to kneading, the above-mentioned treatment with a silane coupling agent was performed.

For mixing, an all-ceramic three-roll mill was used to prevent metal powder from being mixed into the varnish. By passing the mixture through the rolls twice, no particles larger than 40 μm were observed with a grind gauge, and it was confirmed that the mixture was sufficiently kneaded.

In this formulation, the content of Ah03 is 83% by weight, which is the same as in the example. In this way, a solvent-free adhesive of about 300,000 cps was obtained. Put this on an AI board with a thickness of 1.0+n.
Coat it to a thickness of μm and leave it in a clean oven for 1
B-stage was performed at 20° C. for 10 minutes.

This was repeated again to obtain an insulating layer with a total thickness of 100 μm on the AI board. The same 35 μm copper foil as used in the examples was attached to this using a hot roll, and curing was performed in an autoclave under the same conditions as in the examples.

The manufacturing process of the metal base substrate thus obtained is shown in Table 1, and its performance is shown in Table 2.

(3) Comparative Example 2゜ In Comparative Example 2, the same varnish used in the example was applied to a thickness of 1.
When 70 μm of the coating was applied on an Os*^l board and dried for 5 minutes in a clean open at 120°C, the coating thickness was 50 μm, and the surface had holes of about 0.1 fl in diameter here and there that could be confirmed with a looper. was recognized. This was repeated to perform two coatings, and the same procedure as in Comparative Example 1 was followed to obtain a copper-clad laminate with an insulating layer of 100 μm.

The manufacturing process of the metal base substrate thus obtained is shown in Table 1, and its performance is shown in Table 2.

Note that the withstand voltage was measured in oil using a 50 Hz AC power source. Leave 100fiφ copper foil by etching, JIS-
Looking at each item in Table 1, the surface treatment of Al2O2 is complicated in Comparative Example 1 because it is a separate treatment, but it is simple in the Example. Mixing the varnish is not preferable since the three rolls made of all ceramics in Comparative Example 1 are not preferable in terms of processing capacity, labor, and large variations among workers. In this respect, the embodiment allows simple and stable operation. Since the varnish can be easily filtered in the embodiment, redundancy can be provided in terms of quality assurance, which is advantageous. The coating was carried out continuously on the copper foil, which was then passed through a drying oven (the example is better). The drying or B-stage is completed more quickly in the embodiment than only in terms of time.

There is no particular difference in lamination and curing in both the Examples and Comparative Examples. As described above, the present invention is significantly superior to conventional methods in terms of the time and equipment required for the process itself.

In Table 2, the performance etc. of the laminates manufactured by the present invention and the conventional method were checked. The fact that the thermal conductivity was low in Comparative Example 2 even though the filler content was exactly the same, even when combined with the fact that small holes were confirmed with the looper.
This seems to be evidence that a void has formed. In Comparative Example 2, the solder heat resistance after deterioration due to moist heat is also significantly inferior, but above all, the problem is that the withstand voltage is low, there is a large amount of variation, and the insulating property is already lost after deterioration due to heat. On the other hand, in the example in which the same varnish was applied to the copper foil and dried, this problem did not occur, and the performance was extremely excellent. This also shows that the idea that varnishes using solvents are a problem is wrong, and that if the manufacturing method disclosed by the present invention is followed, it will be possible to achieve better performance than Comparative Example 1, which is the conventional method.

〔Effect of the invention〕

As explained above, according to the present invention, the process is easy and it is possible to produce a product with high quality, especially reliable insulation.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram showing an example of a stirring pot, and FIG. 2 is an explanatory diagram showing an example of a coating drying device. 1...Motor, 2...Kettle, 3...Raw materials, 4...
- Propeller, 5... Extraction port, 11... Copper foil unwinding part, 12... Doctor blade, 13... Drying oven, 14... Copper foil winding part with adhesive varnish. Agent Patent Attorney Nobuo Ogawa −

Claims (1)

[Claims] An adhesive varnish consisting of a solid resin composition, an inorganic filler, and a solvent is applied to the surface of the metal foil and dried, and after repeating this application and drying at least once, the adhesive varnish is applied to the metal foil. A method for manufacturing an integrated circuit board, which comprises bonding a surface to a metal plate.