JPH03177385A - Circuit substrate having high thermal conductivity - Google Patents

Abstract

PURPOSE:To provide a circuit substrate having high heat conductivity, showing bond strength between AlN substrate and metallized layer, bond reliability, etc., by forming a metallized layer through a silicone layer on the surface of a sintered material consisting essentially of AlN. CONSTITUTION:A silicone resin layer is formed on an AIN substrate by a method of coating the AlN substrate with a solution containing silicone resin oligomer (e.g. trimethoxysilane oligomer) followed by curing, etc. Then, a metallized layer is formed on the silicone resin layer by thick film printing method, DBC method, thin film method, electroless plating, etc., to produce a circuit substrate having high heat conductivity. Consequently, since the silicone resin layer is formed before the metallized layer is formed on the AlN substrate, bond strength between the metallized layer and the AlN substrate can be improved and the prepared substrate having high heat conductivity is especially useful as IC insulating substrate.

Description

[Detailed Description of the Invention] [Industrial FLL Field] The present invention is directed to a nitrided substrate having a metallized layer that has excellent bonding strength and bonding reliability with the substrate and is useful as a highly thermally conductive substrate, particularly as an IC insulating substrate. The present invention relates to an aluminum (AβN) substrate.

[Prior Art] Conventionally, ceramic substrates mainly containing alumina have been used for semiconductor packaging substrates, etc., but as the power of semiconductors increases.

With higher integration and modularization, the amount of heat generated per circuit area is increasing.

For this reason, a ceramic substrate is needed, which has greater heat dissipation (that is, higher thermal conductivity) than an alumina substrate and has electrical characteristics comparable to alumina.

As a ceramic substrate that satisfies these characteristics, aluminum nitride substrates, which have excellent electrical properties such as high thermal conductivity, high insulation properties, high dielectric strength, low dielectric constant, and low dielectric loss, have attracted attention in recent years.

However, when a conductor paste or a resistor paste is printed and fired on an AβN substrate, there is a problem in that the glass in the paste and the AffN substrate do not wet well, and the bonding reliability between the paste and the surface of the AffN substrate is low. This is the DBC method (Direct Bond Copper method)
The same applies to metallized layer forming methods such as . Also, currently A4
Pastes specifically for 2N substrates are being developed, but one with high bonding reliability has not yet been obtained.

In order to improve the bondability between the paste and the AffN substrate surface, an alumina layer is formed on the substrate surface by heating the AβN substrate surface in the air or an oxygen atmosphere, and a metallized layer is formed on top of the alumina layer. Publication No. 46986/1986).

For the same purpose, a method is known in which an oxide film is formed on the surface of an A ff N substrate and a metallized layer is formed thereon. As a method for forming the oxide layer, ifi containing colloidal particles of acid and arsenate (Japanese Patent Application Laid-Open No. 63-248786) is used.
(Japanese Patent Application Laid-open No. 123087/1987), a wet method in which a liquid containing a metal alkoxide is applied and fired in the air (Japanese Patent Application Laid-open No. 123087/1987), or P V D (F'hysical
Vapor Deposition) and CVD (C
Heraical Vapor Deposition
) and the like (Japanese Unexamined Patent Publication No. 182183/1983).

However, in the direct oxidation method of the surface of the Al2N substrate, it is particularly difficult to form a dense alumina layer and to control the thickness of the alumina layer. Furthermore, there is knowledge that as the purity of the alumina in the alumina substrate increases, the adhesion strength actually decreases, and there remains a problem in the adhesion between the surface layer made of alumina alone and the thick film paste. This is the same as in 6 when an alumina film is formed on the substrate surface, and it is necessary to select another composition system in the oxide film forming method.

On the other hand, 1 g of liquid containing oxide colloidal particles was added to A
In the method of forming an oxide film in which I2N is coated on the surface of a substrate and fired in the atmosphere, it is difficult to form a dense oxide layer, so it is not easy to improve the adhesion strength.

Also, a disease that disperses colloidal particles? There is also the problem that it takes time and effort to adjust the night.

In addition, the clear liquid containing metal alkoxide is A ff N
In the method of coating the substrate surface and baking it in the atmosphere, 1. A
Q There is a problem with bonding with the N substrate. History) Containing metal alkoxides (8 liquids) are very difficult to maintain.

In addition, dry removal methods such as PVD and CVD require large-scale equipment, which poses problems in terms of cost and mass production.

[Problem to be Solved by the Invention 1] The present invention aims to solve the above-mentioned problems of the prior art and provide a highly thermally conductive circuit board in which the bonding strength and bonding reliability of the metallized layer to the Al2N substrate are improved. It is.

[Means for Solving the Problems J] In order to solve the above problems, the present invention provides a sintered body mainly composed of aluminum nitride, a silicone resin layer formed on the surface of the sintered body, and a silicone resin layer formed on the surface of the sintered body. The present invention provides a highly conductive circuit board comprising a metallized layer.

[Effect 1] According to experiments conducted by the present inventors, sufficient bonding strength was obtained when 187a containing Schiffcone resin was coated on an AffN substrate, heated and cured, and then a metallized surface was formed. was obtained from this knowledge.

The silicone resin layer on the , A I2 N substrate is generally formed by applying a molten acid (coating liquid) containing a Schifkorn resin oligomer onto the A R,N substrate and then curing it.

The silicone resin oligomers used in the present invention include alkoxysilane oligomers such as trimethoxysilane, trimethylethoxysilane, methyldimethoxysilane, and tetraethoxysilane, silazane oligomers such as hexamethyldisilane and octamethylcyclotetrasilazane, and reactive siloxanes. Examples include oligomers.

The l8 medium for the silicone resin oligomer may be any solvent as long as it can dissolve the silicone resin oligomer, but organic solvents are particularly preferred. Examples of the organic solvent include ethanol, isopropyl alcohol, methyl isobutyl ketone, and toluene.

There are no restrictions on the method of applying the coating liquid, and examples include dip coating, spin-coating, and spray-on.

Curing of the silicone resin is carried out using Karojuku, a catalyst, or the like. For example, in heat curing, the heating temperature varies depending on the type of silicone resin and cannot be generalized, but
600°C is preferred, and 130-300°C is more preferred.

The thickness of the silicone 1-31 fat layer after hardening is 0.01
If it is thinner than μm, there will be insufficient young fruit as a bonding layer, and the thickness of 50g
If it is thicker, it will have a negative effect on the thermal conductivity of the A 12 N substrate, so O,O1~50um is preferable, and O,1
~5 μm is more preferable.

Methods for forming the metallized layer include a thick film printing method, a DBC method, a thin film method, and an electroless plating method. For example, in the thick film printing method, gold (AuJ), gold-platinum (Au-Pt1.
), silver (Ag), silver-palladium fAg-Pd), etc. as a conductor is printed by screen printing, and then heated in the air, oxygen atmosphere, or nitrogen atmosphere at a temperature of about 850 to 950°C. Baking at a temperature within 100 mL to form a metallized layer.

It is known that an extremely thin alumina layer exists on the surface of an AQN substrate. The metal-AffN substrate bond is considered to be the bond between this alumina thin layer and the metal. However, this alumina layer is extremely thin and its adhesion is insufficient.

However, in the present invention, the silicone resin oligomer forms a very dense film by curing and shrinking, and is firmly bonded to the surface of the AβN substrate. especially.

In methods that apply heat during metallization, such as thick-film bonding, it is thought that the bond becomes even stronger by forming an interdiffusion layer at the interface layer, while the metal penetrates into the silicone resin layer. It is thought that this creates a strong bond.

[Example 1 Example I ACN substrate (1 inch x 1 inch x 0.63 mm1) was coated with an isopropyl alcohol solution (concentration 0.t m o Q/2) of an oligomer of methyltriethoxysilane by a dip method and exposed to air. After heat curing at 80 °C for 20 minutes, a 2 mm x 2 mm pattern was screen printed with Ag-Pd thick film paste (DuPont 9061) and baked at 850 °C for 20 minutes in air to form the metallized layer. A copper wire with a diameter of 0.6 mm was formed there.
g2-Pb4O-3r) 58 solder, 90
When the strength of the beer was measured, it was found to be 3.2 kg.

Comparative Example 1 The above beer strength test was conducted on an AβN substrate subjected to other surface treatments, and compared with the example.

Table 1 shows the measurement results of Examples and Comparative Examples.

Table 1 Substrate 2: Ai! N substrate single substrate 3: An ethanol solution (concentration 0, 1 m o β/β) in which alumina colloidal particles are dispersed is applied to an AβN substrate by a dip method,
It was baked at ℃ for 1 hour in the air.

Substrate 4: An ethanol solution of aluminum secondary butoxide (concentration: 0, 1 m 0 12 /Ni) was coated on an Al2N substrate by a dip method, and baked at 900° C. in the air for 1 hour.

Substrate 5: An isopropyl alcohol solution (concentration 0.1 moβ/β) in which silica colloidal particles are dispersed is applied to the /IN substrate by a dip method,
It was baked at 970° C. in the air for 1 hour.

Substrate 6: An isopropyl alcohol solution of tetraethyl silicate (concentration 0.1 m o 9 /β) was coated on an Al2N substrate by a dip method,
It was baked at 970° C. in the air for 1 hour.

Example 2 Aj2N board (1 inch x 1 inch x 0.63 mm)
A methanol solution of hexamethyldisilazane oligomer (concentration 0.1 m o I!, /12) was coated on the surface using the dip method, and after heating and curing in the air at 180 °C for 20 minutes, a thickness of 0-5 was applied. A 99.99% copper plate of mm was fired in vacuum at 820° C. for 1 hour to form a metallized layer with a 2 mm×2 mm pattern. There is a diameter of 0.8 m
When we soldered 5m copper wire with 5n60-Pb40 solder and measured the beer strength at 90 degrees, it was 22.1k.
It was heavy.

Comparative Example 2 The beer strength test described above was conducted on an Al2N substrate subjected to other surface treatments, and compared with the example.

Table 2 shows the measurement results of Examples and Comparative Examples.

Table 2 Substrate 2: A flooded N substrate Single substrate 3: An isopropyl alcohol solution (a degree 0.1 m o Il!/12) in which alumina colloidal particles are dispersed is applied to an A12N substrate by the dip method, and heated at 900°C. It was baked in the air for 1 hour.

Substrate 4: An ethanol solution of aluminum ethoxide (concentration 0-1 moβ/β) was coated on an AβN substrate by a dip method, and baked at 900° C. in the air for 1 hour.

Substrate 5: A methanol solution (a degree 0.1 mo 12/42) in which silica colloid particles were dispersed was applied to the IN substrate by a dip method.

Bake at 970℃ for 1 hour in the air. Ta.

: An isopropanol solution of tetraisobrobyrsilicate on an A42N substrate (a degree 0.1 m o Q /β
) was applied using the dip method and baked at 970° C. in the air for 1 hour.

Substrate 6 Example 3 A βN substrate (1 inch x 1 inch x 0.63 mm) was coated with an isopropyl alcohol solution of diphenyldimethoxysilane oligomer (a degree 0.1 m o Q/12
) was coated using the dip method, heated and cured at 180°C for 20 minutes in the air, and then coated with a gold target for 2 m using the sputtering method.
A metallization layer with a m×2 mm pattern was formed. Insert a copper wire with a diameter of 0.6 mm therein.
When I soldered it with the same solder and measured the beer strength at 90 degrees, it weighed 4 kg.

Comparative Example 3 The beer strength test described above was conducted on an Al2N substrate subjected to other surface treatments, and compared with the example.

Table 3 shows the measurement results of Examples and Comparative Examples.

Table 3 Substrate 2: AβN substrate Single substrate 3: A Buchnol solution (concentration 0.1 moβ/I2) in which alumina colloidal particles were dispersed was applied to an AffN substrate by a dip method.

Bake in air at 900℃ for 1 hour. Ta.

Substrate 4: An ethanol solution of aluminum isopropoxide (concentration O9I mo Q/Q) was applied to an Al2N substrate by a dip method.

Bake in air at 900℃ for 1 hour. Ta.

Group #ii5: A methanol solution (concentration 0.1 mob/β) in which silica colloid particles were dispersed was applied to an AβN substrate by a dip method.

Bake at 970℃ for 1 hour in the air. Ta.

Substrate 6: An isopropanol solution of tetramethyl silicate (0.1 moβ/l at a degree of a degree) was applied by dip method to an AffN substrate.

Bake at 970℃ for 1 hour in the air. Ta.

[Effects of the Invention] The present invention has the advantage of forming a silicone resin layer before forming a metallized layer on an AβN substrate, so that the metallized layer and the Aff
It was possible to improve the bonding strength of the N substrate. For this reason, it has become possible to obtain AβN high thermal conductivity circuit boards with superior bonding strength and bonding reliability compared to conventional methods6.In addition, in the conventional oxide layer formation method, after applying the coating liquid to the substrate, it is possible to obtain an AβN high thermal conductivity circuit board. Although the above heat treatment was necessary, the present invention makes it possible to form the intermediate layer (silicone resin layer) at a low temperature of 180°C.

Claims (1)

[Claims] 1. A high-temperature device comprising a sintered body mainly composed of aluminum nitride, a silicone resin layer formed on the surface of the sintered body, and a metallized layer further formed thereon. Conductive circuit board.