CN102291928A - Heat-conducting insulating aluminum nitride metal base plate and manufacturing method thereof - Google Patents

Abstract

The invention discloses a heat-conducting aluminum nitride insulating metal substrate and a preparation method thereof. The metal substrate uses an aluminum nitride ceramic plate as a heat-conducting insulating layer, the upper and lower sides of the insulating layer are coated with a buffer layer, and the outer surfaces of the two buffer layers are coated with Putting on the first conductive layer; wherein, the surface of the lower first conductive layer is plated with a metal base layer, the surface of the upper first conductive layer is plated with a second conductive layer, and the second conductive layer is coated with a protective layer. The preparation method uses an aluminum nitride ceramic plate as a thermally conductive insulating layer, and a buffer layer and a first conductive layer are plated by a physical deposition method. One side of the first conductive layer is coated with a metal base layer by electrochemical deposition, and the other side of the conductive layer is coated with a high-conductivity electrochemical plating layer. The second conductive layer and protective layer. The aluminum nitride insulated metal substrate with high thermal conductivity of the present invention has the advantages of high heat dissipation efficiency, long service life, etc., high reliability, and can meet the packaging requirements of various components.

Description

A heat-conducting aluminum nitride insulating metal substrate and its preparation method

technical field

The invention relates to a method for preparing a thermally conductive metal printed circuit substrate, in particular to a high thermally conductive metal substrate material prepared through a multi-step process with a high thermally conductive aluminum nitride ceramic plate as a substrate.

Background technique

With the development of light, thin, small, high-density and multi-functional electronic products, the assembly density and integration of components on the circuit board are getting higher and higher, the power consumption is increasing, and the heat dissipation performance requirements of the substrate are also increasing. high. If the heat dissipation of the substrate is not good, it will cause the components on the circuit board to overheat and greatly reduce the overall reliability. In this case, it is imminent to study reliable high thermal conductivity metal substrates.

A metal substrate generally consists of a three-layer structure, namely a conductive layer (used as a circuit), an insulating layer and a metal base layer (used for heat conduction). Among them, the insulating layer is a layer of thermally conductive insulating material with low thermal resistance and high dielectric constant, which mainly plays the role of connection, insulation and heat conduction, and is the core technology of the metal substrate.

At present, the metal substrate with better thermal conductivity is generally prepared by anodizing the valve metal to prepare an insulating layer, such as preparing an aluminum oxide insulating layer by anodizing on an aluminum surface, and then making a conductive layer on it by conductive metallization. However, the thermal conductivity of the alumina insulating layer is only 30W/m·K, which is still the bottleneck of the heat dissipation of the heat-conducting metal substrate, and the insulating and heat-conducting metal substrate made of it is still difficult to meet the increasingly high heat dissipation requirements in the future. For aluminum nitride, the thermal conductivity of a single crystal is about 270 W/m·K, and the thermal conductivity of a general aluminum nitride ceramic sheet is also 180-200 W/m·K, which is an insulating material with ultra-high thermal conductivity. However, the preparation method of the aluminum nitride insulating film is complicated and the manufacturing cost is high, which greatly limits the application range of using aluminum nitride as the insulating layer to prepare the heat-conducting metal substrate.

Chinese patent application 200710019440.1 (publication number 101232774, published on July 30, 2008) discloses a high thermal conductivity ceramic-based printed circuit board and its manufacturing method. The circuit board includes an aluminum nitride ceramic layer bottom layer, epoxy glass fiber The intermediate insulating layer and the surface conductive layer formed by cloth bonding sheet or high thermal conductivity epoxy polymer. Choose a clean and flat epoxy resin copper-clad thin insulating layer, use vapor deposition method to process the surface of the insulating layer to make a heat-dissipating ceramic layer, further cover the outer surface of the insulating layer with a conductive layer, and then etch on the conductive layer. Conductive lines.

Contents of the invention

The purpose of the present invention is to provide a high thermal conductivity aluminum nitride insulating metal substrate with a thermal conductivity greater than 20 W/m·K in view of the deficiencies in the prior art.

Another object of the present invention is to provide a method for preparing the above metal substrate.

The present invention realizes above-mentioned object through following technical scheme:

An aluminum nitride insulating metal substrate with high thermal conductivity uses an aluminum nitride ceramic plate as a thermally conductive insulating layer, the upper and lower sides of the insulating layer are coated with a buffer layer, and the outer surfaces of the two buffer layers are coated with a first conductive layer; wherein, the lower The surface of the first conductive layer is plated with a metal base layer, the surface of the upper first conductive layer is plated with a second conductive layer, and the second conductive layer is externally plated with a protective layer.

For the metal substrate, the thickness of the aluminum nitride ceramic plate is 0.1-2.0 mm, the thickness of the buffer layer is 300-800 Å, the thickness of the first conductive layer is 300-800 Å, the thickness of the metal base layer is 0.05-2.00 mm, and the thickness of the second conductive layer is 0.01~1.00 mm, and the thickness of the protective layer is 4~20 μm.

The metal of the buffer layer is tungsten, molybdenum or titanium, or an alloy of any two metals; the buffer layer can effectively prevent peeling between the insulating layer and the conductive layer.

The first conductive layer is copper, nickel, iron, silver, gold, palladium or an alloy of any two metals therein.

The metal of the metal base layer is copper, silver, aluminum, nickel or an alloy of any two metals, which mainly play the role of support and heat conduction.

The second conductive layer is copper, aluminum, silver, gold or an alloy of any two metals, and the conductive layer is mainly thickened to improve the conductivity of the circuit.

The protective layer is electroless nickel/immersion gold (ENIG), electroless/electrosilver plating (ie, chemical silver plating or electroplating silver), or electroless/electrolytic tin plating (ie, electroless tin plating or electrolytic tin plating).

The preparation method of the above-mentioned metal substrate, the steps are as follows:

(1) Process the thermal stress buffer layer on the upper and lower sides of the aluminum nitride insulating ceramic plate, and use the physical deposition method to coat the buffer layer metal. The thermal expansion coefficient of the buffer layer is consistent with that of the aluminum nitride ceramic;

(2) The first conductive layer is plated on the outer surfaces of the two buffer layers by physical deposition method;

(3) Electrochemical deposition is used on the surface of the first conductive layer below it, and the metal base layer is plated;

(4) Electrochemical deposition is applied to the surface of the first conductive layer above, and the second conductive layer is plated, which is a highly conductive metal;

(5) Electrochemical deposition is used on the surface of the second conductive layer to plate a protective layer.

The physical deposition method is ion plating, sputtering or evaporation; the electrochemical deposition method is electroplating or electroless plating, all of which are conventional preparation methods in the field.

In the above preparation method, the buffer layer is firstly processed on both surfaces of the aluminum nitride insulating layer to form a buffer layer matching the thermal expansion coefficient of aluminum nitride, and then it is made conductive by a certain method, and then one side is passed through the electric The chemical deposition method is to plate a thicker metal layer to support the metal substrate. On the other side, the conductive layer is thickened by the electrochemical deposition method, and finally a protective layer with good corrosion resistance and solderability is plated on the surface of the conductive layer.

Compared with the prior art, the present invention has the following excellent properties:

(1) The preparation method of the metal substrate with high thermal conductivity provided by the present invention does not contain heavy metals as raw materials, is environmentally friendly, and the raw materials are simple and easy to obtain, and the production process is stable and easy to operate;

(2) The high thermal conductivity metal substrate obtained by the method provided by the present invention has extremely high heat dissipation efficiency and long service life; after baking at 300°C for 10 minutes, there is no peeling phenomenon between the multi-layer metal layers, and the performance reliability is extremely high. Fully meet the packaging requirements of various components.

Description of drawings

Figure 1. Schematic diagram of the structure of the high thermal conductivity aluminum nitride insulated metal substrate, 1 is the insulating layer of the aluminum nitride ceramic plate, 2 is the buffer layer, 3 is the first conductive layer, 4 is the metal base layer, 5 is the second conductive layer, and 6 is the The protective layer.

Detailed ways

Example 1

On both surfaces of a 0.2mm thick aluminum nitride ceramic plate, a buffer layer - 300Å of molybdenum and titanium alloy is evaporated, and then 800Å of metallic silver is magnetron sputtered to realize its electrical conductivity; and then electroplated on the surface of metallic silver The copper is 1mm, and the silver-copper alloy on the other side is electroplated with 10μm of silver-copper alloy, and the conductive layer is thickened. The thermal conductivity of the test is 136W/m·K. Then stick a film on the surface of the metal gold plating layer, etch to obtain the required circuit; finally perform electroless silver plating of 15 μm to obtain an aluminum nitride insulating metal substrate with high thermal conductivity.

Example 2

Magnetron sputtering a buffer layer on both surfaces of the 0.3mm thick aluminum nitride ceramic plate - 500Å of tungsten and titanium alloy, and then ion-plated metal copper 500Å to achieve its conductivity; and then on one of the metal copper surfaces Nickel-copper alloy is electroplated 0.8mm, and the copper surface of the other side is chemically silver-plated 10μm, the conductive layer is thickened, and the measured thermal conductivity is 121W/m·K. Then, stick a film on the surface of the metal silver plating, etch to obtain the required circuit; finally, perform electroless nickel plating/immersion gold 10μm to obtain a high thermal conductivity aluminum nitride insulating metal substrate.

Example 3

A layer of 500Å metal tungsten buffer layer is ion-plated on both surfaces of a 0.2mm thick aluminum nitride ceramic plate, and then 300Å of iron-nickel alloy is evaporated to realize its conductivity; then silver is electroplated on one side of the metal gold surface for 0.5mm, On the other side, the metal gold surface is electroplated with 30 μm copper, and the conductive layer is thickened. The thermal conductivity of the test is 167W/m·K. Then, stick a film on the surface of the metal copper plating layer and perform etching treatment to obtain the required circuit; finally, electroplate tin 20 μm to obtain an aluminum nitride insulating metal substrate with high thermal conductivity.

The high thermal conductivity aluminum nitride insulating metal substrates prepared in the three examples were baked at 300°C for 10 minutes, and there was no peeling phenomenon between the multilayer metal layers, and the performance reliability was extremely high.

Claims (9)

1. A heat-conducting aluminum nitride insulating metal substrate, characterized in that an aluminum nitride ceramic plate is used as a heat-conducting insulating layer, the upper and lower sides of the insulating layer are coated with buffer layers, and the outer surfaces of the two buffer layers are coated with the first conductive layer; Wherein, the surface of the lower first conductive layer is plated with a metal base layer, the surface of the upper first conductive layer is plated with a second conductive layer, and the second conductive layer is coated with a protective layer. 2. The metal substrate according to claim 1, characterized in that the thickness of the aluminum nitride ceramic plate is 0.1-2.0 mm, the thickness of the buffer layer is 300-800 Å, the thickness of the first conductive layer is 300-800 Å, and the thickness of the metal base layer 0.05~2.00 mm, the thickness of the second conductive layer is 0.01~1.00 mm, and the thickness of the protective layer is 4~20 μm. 3 . The metal substrate according to claim 1 , wherein the metal of the buffer layer is tungsten, molybdenum, titanium or an alloy of any two metals therein. 4. The metal substrate according to claim 1, wherein the metal of the first conductive layer is copper, nickel, iron, silver, gold, palladium or an alloy of any two metals therein. 5. The metal substrate according to claim 1, characterized in that the metal of the metal base layer is copper, silver, aluminum, nickel or an alloy of any two metals therein. 6. The metal substrate according to claim 1, wherein the metal of the second conductive layer is copper, aluminum, silver, gold or an alloy of any two metals therein. 7. The metal substrate according to claim 1, characterized in that the protective layer is electroless nickel/immersion gold, electroless/electrosilver or electroless/electrotin. 8. The preparation method of the metal substrate according to claim 1, characterized in that the steps are as follows: (1) Process the thermal stress buffer layer on the upper and lower sides of the aluminum nitride insulating ceramic plate, and use the physical deposition method to coat the buffer layer metal. The thermal expansion coefficient of the buffer layer is consistent with that of the aluminum nitride ceramic; (2) The first conductive layer is plated on the outer surfaces of the two buffer layers by physical deposition method; (3) Electrochemical deposition is used on the surface of the first conductive layer below it, and the metal base layer is plated; (4) Electrochemical deposition is applied to the surface of the first conductive layer above, and the second conductive layer is plated; (5) Electrochemical deposition is used on the surface of the second conductive layer to plate a protective layer. 9. The preparation method according to claim 8, characterized in that the physical deposition method is ion plating, sputtering or evaporation; the electrochemical deposition method is electroplating or electroless plating.

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