CN115151047A

CN115151047A - Method for forming circuit pattern on aluminum-based silicon carbide substrate

Info

Publication number: CN115151047A
Application number: CN202210312233.XA
Authority: CN
Inventors: 施鸿贵; 廖忠仪; 廖九岳
Original assignee: Individual
Current assignee: Individual
Priority date: 2021-03-31
Filing date: 2022-03-28
Publication date: 2022-10-04
Also published as: TWI790585B; TW202240782A

Abstract

The invention relates to a method for forming a circuit pattern on an aluminum-based silicon carbide substrate, which comprises the following steps: a) Heating the ceramic material to a full-melting or semi-melting state; b) Spraying the full-melting or semi-melting ceramic material on the surface of an aluminum-based silicon carbide substrate to form an insulation deposition layer; c) Cooling and annealing the insulation deposition layer to form an insulation layer; d) Disposing a mask having a plurality of holes on the insulating layer; e) Spraying metal powder on the mask to make the metal powder adhere to the mask and the insulating layer in the hole; and f) removing the mask to form a circuit layer.

Description

Method for forming circuit pattern on aluminum-based silicon carbide substrate

Technical Field

The present invention relates to aluminium-based silicon carbide materials, and in particular to surface treatment of aluminium-based silicon carbide.

Background

High power or high performance semiconductor devices require an insulating substrate having high thermal conductivity for a circuit pattern to be disposed thereon, and conventional insulating substrates are composed of a metal base and an insulating layer, but have a limitation in current capacity, generally below 50A, by using a metal material as a base. In addition, the ceramic substrate can make the circuit current attached to it exceed 50A, but the bonding process between the ceramic substrate and the circuit layer is very difficult and costly.

Aluminum-based silicon carbide (AlSiC) is a metal-based composite material composed of aluminum and silicon carbide particles. It has high thermal conductivity and its coefficient of thermal expansion can be adjusted to match other materials such as silicon, silicon carbide, gallium arsenide, wafers, and various ceramics. Aluminum-based silicon carbide is mainly used as a substrate for power semiconductor devices and high power modules, helps heat dissipation due to its high thermal conductivity, and is very suitable for being used as an insulating substrate.

Since aluminum-based silicon carbide has conductivity, in order to provide an insulating effect on the surface, a surface modification (surface modification) process is required to form an insulating layer on the surface of the aluminum-based silicon carbide. In the prior art, a brazing process is adopted, in which dry solder (such as copper powder or tin powder) or wet solder (such as copper paste or silver paste) is coated on the surface of an aluminum-based silicon carbide substrate, a ceramic material is disposed above the solder, and the ceramic material is fixed by a fixture and then heated, so that the ceramic material is attached to the surface of the aluminum-based silicon carbide. The principle of the attachment is that the ambient temperature is heated to be close to the melting point of the solder, the solder is converted from a solid state to a liquid state or a quasi-liquid state to permeate into micro holes on the surfaces of the aluminum-based silicon carbide and the ceramic material, and the ceramic material can be adhered to the surface of the aluminum-based silicon carbide substrate by the solder after the temperature is returned.

However, such a brazing process is complicated in process, and requires heating and cooling processes in addition to applying solder, which takes a long time, and a layer of solder is still present between the aluminum-based silicon carbide and the ceramic material, and although the thermal expansion coefficient of the aluminum-based silicon carbide may be consistent with that of the ceramic material, the solder is not so strong that the adhesion strength of the ceramic material is insufficient, thereby resulting in a decrease in reliability. Furthermore, the brazing process is prone to have uneven thickness distribution, which affects the heat conduction efficiency between the aluminum-based silicon carbide and the ceramic material.

Generally, a copper foil circuit is formed on a ceramic board and then soldered on an insulating substrate, but when the two-stage process is applied to a high power semiconductor device, the circuit layer is easily peeled off from the insulating substrate due to local high heat, and the manufacturing cost is high.

Disclosure of Invention

The present invention is directed to a method for forming a circuit pattern on an aluminum-based silicon carbide substrate, which can eliminate the use of solder in the portion where an insulating substrate is formed, and can directly attach a ceramic material to the surface of the aluminum-based silicon carbide substrate, thereby avoiding the problems of thermal expansion coefficient inconsistency and thermal conductivity obstruction caused by the use of solder, and further achieving the effects of simplifying the process and shortening the working hours.

Another object of the present invention is to provide a method for forming a circuit pattern on an al-based sic substrate, which can directly form a circuit layer on an insulating substrate at a portion where the circuit layer is formed, does not require a soldering process, can greatly improve current capacity, and can simplify processes and reduce manufacturing costs.

To achieve the above object, a method of forming a circuit pattern on an al-based sic substrate according to the present invention includes the steps of: (a) heating the ceramic material to a fully or semi-molten state; (b) Spraying the full-melting or semi-melting ceramic material on the surface of an aluminum-based silicon carbide substrate to form an insulation deposition layer; (c) Cooling and annealing the insulation deposition layer to form an insulation layer; (d) Disposing a mask having a plurality of holes on the insulating layer; (e) Heating the metallic material to between 2000 ℃ and 5000 ℃ to form a semi-molten metallic powder; (f) Spraying the semi-molten metal powder on the mask to make the metal powder adhere to the mask and the insulating layer in the hole; (g) Removing the mask to form a metal deposition layer on the insulating layer; and (h) cooling and annealing the metal deposition layer to form a circuit layer.

To achieve the above object, a method of forming a circuit pattern on an al-based sic substrate according to the present invention includes the steps of: (a) heating the ceramic material to a fully or semi-molten state; (b) Spraying the full-melting or semi-melting ceramic material on the surface of an aluminum-based silicon carbide substrate to form an insulation deposition layer; (c) Cooling and annealing the insulation deposition layer to form an insulation layer; (d) Disposing a mask having a plurality of holes on the insulating layer; (e) heating the working gas to between 450 ℃ and 850 ℃; (f) Feeding metal powder into the heated working gas; (g) Spraying the working gas and the metal powder to a mask by a supersonic nozzle to make the metal powder adhere to the mask and the insulating layer positioned in the hole; (h) The mask is removed to form a circuit layer on the insulating layer.

Drawings

FIG. 1 is a flow chart of a method of the present invention;

FIG. 2 is a schematic view of the formation of the insulating deposition layer of the present invention;

FIG. 3 is an enlarged view of circle A of FIG. 2;

FIGS. 4A to 4C are schematic views illustrating circuit layer formation according to the present invention;

FIG. 5 is a thermal spray process flow diagram of the present invention;

FIG. 6 is a cold spray drawing of the present invention.

Description of the figure numbers:

s1 step (a)

S2 step (b)

S3 step (c)

S4 step (d)

S5 step (e)

S6 step (f)

S7 step (g)

S8 step (h)

1 spray gun

2 aluminum-based silicon carbide substrate

3 insulating deposition layer

3' insulating layer

4 ceramic material powder

5 shade

51 holes

6 circuit layers.

Detailed Description

The method for forming a circuit pattern on an aluminum-based silicon carbide substrate of the present invention can be roughly divided into two stages, wherein the first stage is to form an insulating substrate by using aluminum-based silicon carbide as a base material, and the adopted technical means is called thermal spray (thermal spray), and the second stage is to form a circuit layer on the insulating substrate, and the adopted technical means is divided into two types, namely hot spray (hot spray) and cold spray (cold spray). Referring to fig. 1, the method for forming an insulating substrate with aluminum-based silicon carbide according to the present invention includes the following steps:

in step S1, the ceramic material is heated to a fully molten or semi-molten state, and the ceramic material is instantaneously heated by a plasma flame (plasma torch), wherein the melting point of the ceramic material is about 2000 ℃, and the plasma flame temperature of the atmospheric melting device adopted in the present invention is about 12000 ℃, so that the ceramic material theoretically becomes a fully-molten state after being fed into the plasma flame for heating, but if the ceramic material is fed into the plasma flame at a relatively high feeding speed, the ceramic material may be only semi-molten (semi-molten) or partially semi-molten (partially-molten), but even if the ceramic material only reaches the semi-molten state, the melting process of the present invention can be completed.

In step S2, the fully or semi-melted ceramic material is sprayed onto the surface of an Al-based SiC substrate to form an insulation deposition layer. Referring to fig. 2, the ceramic material in the fully molten or semi-molten state formed in step (a) is ejected by the ejection gun 1 with a high-speed airflow to impact the surface of the al-based silicon carbide substrate 2 at a high speed, the ejection speed of the high-pressure airflow is greater than 280m/sec, and the ceramic material powder 4 ejected by the ejection gun 1 is attached to the surface of the al-based silicon carbide substrate 2 to form an insulation deposition layer 3 with a porosity of less than 1.5%, as shown in fig. 3, after impacting the surface of the al-based silicon carbide substrate 2, the ceramic material powder 4 is formed into flat particles and attached to the surface of the al-based silicon carbide substrate 2, and the ceramic material powder 4 can be stacked on the surface of the al-based silicon carbide substrate 2 by the transverse movement of the al-based silicon carbide substrate 2 relative to the ejection gun 1, so that the insulation deposition layer 3 has a desired uniform thickness.

In step S3, the insulation deposition layer 3 is cooled and annealed to form a firm and compact flat insulation layer 3' on the insulation deposition layer 3, the subsequent circuit pattern process can be performed, and the cooling and annealing speed is optimized to-3 deg.C/min. Step S3 is to complete the fabrication of the insulating substrate, i.e. as shown in fig. 4A, the insulating substrate is composed of an insulating layer 3' and an al-based sic substrate 2.

Referring to fig. 5, which is a flow chart of the thermal spraying method according to the present invention, after the insulating substrate is manufactured, in step S4, a mask 5 is attached to the insulating layer 3', the mask 5 is provided with a plurality of holes 51 corresponding to the desired circuit pattern, and the holes 51 penetrate through the mask 5, so that part of the surface of the insulating layer 3' is exposed in the holes 51.

In step S5, the metal powder for forming the circuit pattern is heated to 2000 ℃ to 5000 ℃ to form semi-molten metal powder.

In step S6, the semi-molten metal powder is sprayed onto the mask 5, and the semi-molten metal powder is attached to the surface of the mask 5 and is attached to a portion of the surface of the insulating layer 3' through the hole 51 to form a metal deposition layer, as shown in fig. 4B.

In step S7, the mask 5 is removed from the insulating layer 3 'to remove the metal powder attached to the mask 5 and leave the metal deposition layer attached to the surface of the insulating layer 3'.

In step S8, the metal deposition layer is cooled and annealed to form a stable circuit layer 6, as shown in FIG. 4C.

Referring to fig. 6, which is a flow chart of the cold spraying method of the present invention, after the insulating substrate is manufactured, in step S9, a mask 5 is attached to the insulating layer 3', the mask 5 is provided with a plurality of holes 51 corresponding to the required circuit patterns, and the holes 51 penetrate through the mask 5, so that part of the surface of the insulating layer 3' is exposed in the holes 51.

In step S10, the working gas is heated to 450 ℃ to 850 ℃. The working gas includes nitrogen, helium, and the like, depending on the material.

In step S11, a metal powder for forming a circuit pattern having a particle size of less than 50 μm is fed into the heated working gas.

In step S12, the working gas and the metal powder are sprayed toward the mask 5 through the supersonic nozzle and attached to a portion of the surface of the insulating layer 3' through the holes 51 of the mask 5 to form a metal deposition layer, i.e., the spraying speed of the working gas and the metal powder is about 700m/S, as shown in FIG. 4B.

In step S13, the mask 5 is removed from the insulating layer 3 'to remove the metal powder attached to the mask 5 and leave the metal deposition layer attached to the surface of the insulating layer 3' to form a circuit layer 6, as shown in fig. 4C.

Through the cold spraying or hot spraying method, the circuit layer can be directly formed on the aluminum-based silicon carbide insulating substrate, a two-stage welding method is not needed, the current capacity can be greatly improved, the process can be simplified, and the manufacturing cost can be reduced.

Claims

1. A method of forming a circuit pattern in an aluminum-based silicon carbide substrate, comprising:

(a) Heating the ceramic material to a full-melting or semi-melting state;

(b) Spraying the full-melting or semi-melting ceramic material on the surface of an aluminum-based silicon carbide substrate to form an insulation deposition layer;

(c) Cooling and annealing the insulation deposition layer to form an insulation layer;

(d) Arranging a mask with a plurality of holes on the insulating layer;

(e) Heating the metallic material to between 2000 ℃ and 5000 ℃ to form a semi-molten metallic powder;

(f) Spraying the semi-molten metal powder on the mask to make the metal powder adhere to the mask and the insulating layer in the hole;

(g) Removing the mask to form a metal deposition layer on the insulating layer; and

(h) Cooling and annealing the metal deposition layer to form a circuit layer.

2. The method of forming a circuit pattern in an aluminum-based silicon carbide substrate of claim 1, wherein step (a) is performed with a plasma torch.

3. The method of forming a circuit pattern on an AlSiC substrate of claim 1 wherein step (b) is performed with a spray gun.

4. The method of forming a circuit pattern in an al-based silicon carbide substrate of claim 3, wherein the torch ejects the heated ceramic material with a high velocity gas stream.

5. The method of forming a circuit pattern on an aluminum-based silicon carbide substrate of claim 4, wherein the high velocity gas stream has a jet velocity of greater than 280m/sec.

6. The method for forming a circuit pattern on an al-based silicon carbide substrate according to claim 1, wherein the cooling tempering speed in step (c) is-3 ℃/min.

7. A method of forming a circuit pattern in an aluminum-based silicon carbide substrate, comprising:

(a) Heating the ceramic material to a full-melting or semi-melting state;

(d) Disposing a mask having a plurality of holes on the insulating layer;

(e) Heating the working gas to a temperature between 450 ℃ and 850 ℃;

(f) Feeding metal powder into the heated working gas;

(g) Spraying the working gas and the metal powder to a mask by a supersonic nozzle so that the metal powder is attached to the mask and the insulating layer positioned in the hole;

(h) The mask is removed to form a circuit layer on the insulating layer.

8. The method of forming a circuit pattern in an al-based silicon carbide substrate of claim 7, wherein step (b) is performed with a spray gun.

9. The method of forming a circuit pattern on an AlSiC substrate of claim 8 wherein the torch ejects the heated ceramic material with a high velocity gas stream.

10. The method of forming a circuit pattern in an al-based silicon carbide substrate of claim 9, wherein the high velocity gas stream has a jet velocity greater than 280m/sec.

11. The method of forming a circuit pattern on an aluminum-based silicon carbide substrate of claim 7, wherein the cooling tempering rate in step (c) is-3 ℃/min.

12. The method of claim 7, wherein the working gas comprises nitrogen and helium.

13. The method of forming a circuit pattern on an al-based silicon carbide substrate of claim 7, wherein the metal powder has a particle size of less than 50 μm.

14. The method of forming a circuit pattern on an al-based sic substrate of claim 7 wherein the injection velocity of the working gas and the metal powder in step (g) is 700m/s.