CN107986810B - AlN ceramic copper-clad substrate for power electronic device and preparation method thereof - Google Patents

Abstract

The invention discloses an AlN ceramic copper-clad substrate for power electronic devices, which is characterized in that it includes an AlN substrate, Cu, Ti, Al film and Cu foil, and the Cu, Ti, and Al films are coated on the surface of the AlN, and the The Cu foil is applied on the Cu, Ti and Al films. The invention also discloses an AlN ceramic copper-clad substrate for power electronic devices and a preparation method thereof. The present invention prepares Cu, Ti, Al slurry without glass phase, brushes it on the surface of AlN by screen printing thick film method and sinters it in an atmosphere to obtain a copper-titanium-aluminum film, and then applies Cu foil near the temperature lower than the melting point of copper. . The invention has simple process and low cost, and the obtained AlN ceramic copper-clad substrate has the advantages of high thermal conductivity, high bonding strength, small surface resistance and the like.

Description

AlN ceramic copper-clad substrate for power electronic devices and preparation method thereof

technical field

The invention relates to a ceramic copper-clad substrate, in particular to an AlN ceramic copper-clad substrate for power electronic devices and a preparation method thereof.

Background technique

With the development of power electronics technology, the heating power density of large-scale integrated circuits has been greatly improved compared with the past. Because heat dissipation involves a series of issues such as force, light, electricity, and heat, it directly affects the operating temperature, electrical characteristics, and service life of power electronic devices. As the input power continues to increase, how to fundamentally solve the heat dissipation problem has become a hot spot of general concern. The packaging substrate plays a decisive role in the heat dissipation of the power electronic system. The high-performance ceramic copper-clad substrate is the key material in the power module packaging technology, and its performance determines the heat dissipation efficiency and reliability of the module.

Copper is a good conductor material, with low resistivity, good anti-electron migration ability, can withstand high current, and good thermal conductivity (398W/m K) can conduct the heat generated in the device in time to reduce the operating temperature of the device , Improve the performance of the device, very suitable for power circuits and high frequency circuits. Compared with other thick film metal materials, metal copper material is cheaper, which can greatly reduce the manufacturing cost of devices.

The high thermal conductivity ceramic substrates developed at this stage include BeO, SiC, Al ₂ O ₃ and AlN, among which BeO is toxic and not conducive to environmental protection; SiC has a high dielectric constant and is not suitable for substrates, and the insulating properties of Al ₂ O ₃ Good, good chemical stability, high strength, and low price, it is the preferred material for ceramic copper clad substrates, but the thermal conductivity of Al ₂ O ₃ is low, and the thermal expansion coefficient with Si (about 4.1×10 ^-6 /K) There is a certain thermal mismatch; AlN material is non-toxic, has a moderate dielectric constant, and its thermal conductivity is much higher than that of Al ₂ O ₃ , which is close to that of BeO. It is suitable for high-power semiconductor substrates and can play a decisive role in the heat dissipation process. . The thermal expansion coefficient of AlN is close to that of Si. Various Si chips and power electronic devices can be directly attached to the AlN substrate without the transition layer of other materials. At the same time, AlN also has high mechanical strength and excellent electrical properties, so AlN ceramics are selected It is the trend of the times to use the substrate as an insulating and heat-conducting substrate.

AlN is a compound with strong covalent bonds. As a non-oxidizing ceramic, it is difficult to react with other metal materials at high temperatures, and it is difficult to implement metallization. The most commonly used method in the industry is to pre-treat the aluminum nitride substrate to form an oxide-type transition layer on the surface of the aluminum nitride. Jurgen Schulz-Harder sputters/evaporates a layer of copper on the aluminum nitride substrate. The thickness of the copper must be strictly controlled. control, and thermal oxidation treatment, the prepared aluminum nitride DBC substrate peel strength ≥ 50N/cm, low porosity, patent number US006066219A. Patent CN101875569A forms a 4-10 μm metal pre-fired layer of copper, copper oxide or cuprous oxide on the surface of aluminum nitride, and performs thermal oxidation treatment at 1250-1350 °C, and then thermal reduction treatment at 550-650 °C for 3-5 hours, The performance of the prepared aluminum nitride substrate is better. Patents CN101445386A and CN103819214A relate to the method of forming a Cu-O eutectic layer by introducing Cu ₂ O between aluminum nitride and Cu layers, thereby forming a copper metallization layer on the surface of aluminum nitride ceramics. Patent CN102208371A relates to the process of obtaining a copper-clad aluminum nitride substrate by magnetron sputtering a Ti modified layer. From this point of view, the published aluminum nitride ceramic metallization method has complicated process, harsh conditions and high cost. However, how to simplify the process and reduce the cost to obtain a high-performance AlN ceramic copper-clad substrate is still a technical problem.

Contents of the invention

In order to overcome the deficiencies in the prior art, the object of the present invention is to provide an AlN ceramic copper-clad substrate for power electronic devices and a preparation method thereof, and obtain AlN ceramics for power electronic devices through screen printing thick film and copper foil bonding processes. copper clad substrate.

In order to solve the above problems, the technical scheme adopted in the present invention is as follows:

AlN ceramic copper-clad substrate for power electronic devices, including AlN substrate, Cu, Ti, Al film and Cu foil, the Cu, Ti, Al film is coated on the surface of AlN, and the Cu foil is bonded to Cu, Ti, Al film and Cu foil. on the Al film. The present invention prepares Cu, Ti, Al slurry without glass phase, brushes and paints on the surface of AlN by screen printing thick film method and sinters in atmosphere to obtain copper titanium aluminum film, and then applies Cu foil near the temperature lower than the melting point of copper .

Preferably, the thickness of the Cu, Ti and Al films is 20-30 μm, and the thickness of the Cu foil is 300-400 μm.

A method for preparing an AlN ceramic copper-clad substrate for power electronic devices, including

Step 1. The process of synthesizing the organic carrier: mix ethyl cellulose, terpineol, and lecithin in a beaker according to a certain ratio, stir and dissolve continuously in a water bath at 95°C to obtain the organic carrier.

Step 2. Preparation process of glass-free Cu, Ti, Al slurry: Weigh the functional phase Cu, Ti, Al powders in proportion and mix them evenly with corresponding proportion of organic carrier to prepare Cu, Ti, Al slurry.

Step 3, cleaning of the AlN substrate: the AlN substrate is ultrasonically cleaned with acetone, alcohol, and deionized water in sequence.

Step 4. Brush the slurry obtained in step 2) on both sides of the AlN substrate in step 3) by a manual screen printing machine.

Step 5. Pre-fire the double-sided printed AlN sheet in a muffle furnace and sinter it in a tube furnace atmosphere to obtain Cu, Ti, and Al films, and then apply it in a nitrogen atmosphere tube furnace near the temperature below the melting point of copper. Connect the Cu foil to obtain the AlN ceramic copper-clad substrate for the power electronic device.

Preferably, the organic carrier is 94.5% of terpineol, 5% of ethyl cellulose, 0.5% of lecithin, and the ratio of the copper, titanium and aluminum metal powder is 65%Cu+5%Ti+30%Al, and the slurry The material is 76% of functional phase metal powder and 24% of organic vehicle mixed evenly.

Preferably, the pre-firing process in step 5 is: raising the temperature in a muffle furnace at 3°C/min to 240°C-350°C for 1-3h.

Preferably, the process conditions for the atmosphere sintering of Cu, Ti and Al films in step 5 are as follows: nitrogen gas is introduced into an air atmosphere tube furnace, the gas flow rate is 100-300 sccm, the ventilation time is 1-3 hours, and at the same time, the temperature is 3°C. /min The heating rate is raised to 1050°C~1070°C and kept for 0.5h~2h, and then the temperature is controlled at a cooling rate of 3°C/min to cool down to 500°C.

Preferably, the process conditions for attaching copper foil in step 5 are as follows: heat up to 1070°C~1080°C for 10~60min at a heating rate of 3°C/min in a tube furnace with a nitrogen atmosphere purity ≥ 99.99%, and control Cool down at a rate of 3°C/min to 500°C and then cool down naturally.

Compared with the prior art, the beneficial effects of the present invention are as follows: 1. The AlN ceramic copper-clad substrate for power electronic devices prepared by the present invention has good adhesion, low surface resistance, and better heat dissipation capability without introducing a glass phase into the intermediate layer. 2. The present invention simplifies the process, does not directly introduce Cu ₂ O and does not require reduction, is low in cost, unique and easy to implement, and is convenient for large-scale production.

Description of drawings

FIG. 1 is a schematic structural view of an AlN ceramic copper-clad substrate for a power electronic device of the present invention.

Detailed ways

The present invention will be further described below in conjunction with accompanying drawing and specific embodiment:

As shown in Figure 1, it is AlN ceramic copper-clad substrate for medium power electronic device of the present invention, comprises AlN substrate, Cu, Ti, Al film and Cu foil, and described Cu, Ti, Al film are printed by screen printing It is formed by coating the slurry on the surface of AlN and then sintering in the atmosphere, and the Cu foil is attached on the Cu, Ti and Al films.

In the preferred version, the ratio of the copper-titanium-aluminum metal powder is 65%Cu+5%Ti+30%Al, the organic vehicle is 94.5% terpineol, 5% ethyl cellulose, 0.5% lecithin, the The slurry is uniformly mixed with 76% functional phase metal powder and 24% organic vehicle, the AlN substrate is 0.5mm, the Cu, Ti, Al film thickness is 20-30μm, and the Cu foil thickness is 300-400μm.

Example 1

A method for preparing an AlN ceramic copper-clad substrate for power electronic devices, comprising the following steps:

Step 1, the process of synthesizing the organic carrier: using ethyl cellulose as a thickener, terpineol as a solvent, and lecithin as an additive. The thickener, solvent, and additives are mixed in a beaker according to a certain ratio, and the organic vehicle is obtained after stirring and dissolving in a water bath at 95°C.

Step 2, Cu, Ti, Al slurry preparation process: Weigh the functional phase Cu, Ti, Al powders in proportion and mix them with the corresponding proportion of organic carrier in a sealed tank, grind and mix on a tank mill at 150r/min for 6h, Prepare Cu, Ti, Al slurry.

Step 3: The 0.5 mm AlN substrate is ultrasonically cleaned with acetone, alcohol, and deionized water for 15 minutes each, and dried for later use.

Step 4. Apply the copper-titanium-aluminum slurry obtained in step 2 evenly on the surface of the AlN obtained in step 3 by a manual screen printing machine, and then dry it in a blast drying oven at 60°C for 30 minutes. After drying, brush the AlN substrate in the same way Dry the other side for later use.

Step 5. Heat the double-sided printed AlN ceramic sheet obtained in step 4 to 240° C. for 2 hours in a muffle furnace at a rate of 3° C./min.

Step 6. Place the sample obtained in step 5 in an air atmosphere tube furnace, feed nitrogen gas at a rate of 100 sccm for 3 hours, and at the same time raise the temperature to 1050° C. at a heating rate of 3° C./min, keep it warm for 2 hours, and cool it down at a cooling rate of 3° C./min to Cool down naturally after 500°C. The obtained Cu, Ti, Al film thickness is 30 μm.

Step 7. After the Cu foil with a thickness of 350 μm is ultrasonically cleaned and dried with absolute ethanol, it is attached to both sides of the sample obtained in step 6, and both sides are clamped by quartz glass sheets and placed in a tube furnace with a nitrogen atmosphere purity ≥ 99.99%. The temperature was raised to 1080°C/min, held for 15 minutes, cooled to 500°C at a cooling rate of 3°C/min, and then cooled naturally to prepare AlN ceramic copper-clad substrates for power electronic devices.

The finally obtained AlN ceramic copper-clad substrate for power electronic devices has a peel strength of ≥9.5N/mm, a surface square resistance of ≤2.4mΩ/□, and a thermal conductivity of >180W/m·k.

Example 2

A method for preparing an AlN ceramic copper-clad substrate for power electronic devices, comprising the following steps:

Step 1, the process of synthesizing the organic carrier: using ethyl cellulose as a thickener, terpineol as a solvent, and lecithin as an additive. The thickener, solvent, and additives are mixed in a beaker according to a certain ratio, and the organic vehicle is obtained after stirring and dissolving in a water bath at 95°C.

Step 2, Cu, Ti, Al slurry preparation process: Weigh the functional phase Cu, Ti, Al powders in proportion and mix them with the corresponding proportion of organic carrier in a sealed tank, grind and mix on a tank mill at 150r/min for 6h, Prepare Cu, Ti, Al slurry.

Step 3: The 0.5 mm AlN substrate is ultrasonically cleaned with acetone, alcohol, and deionized water for 15 minutes each, and dried for later use.

Step 4. Apply the copper-titanium-aluminum slurry obtained in step 2 evenly on the surface of AlN obtained in step 3 through a manual screen printing machine, and then dry it in a 60°C blast drying oven for 30 minutes. After drying, brush the AlN substrate in the same way Dry the other side for later use.

Step 5. Heat the double-sided printed AlN ceramic sheet obtained in step 4 to 300° C. for 1.5 hours in a muffle furnace at a rate of 3° C./min.

Step 6. Place the sample obtained in step 5 in an air atmosphere tube furnace, feed nitrogen gas at a rate of 200 sccm for 2 hours, and at the same time raise the temperature to 1060° C. at a heating rate of 3° C./min, keep it warm for 1 hour, and cool it down at a cooling rate of 3° C./min to Cool down naturally after 500°C. The obtained Cu, Ti, Al film thickness is 24 μm.

Step 7. After the Cu foil with a thickness of 350 μm is ultrasonically cleaned and dried with absolute ethanol, it is attached to both sides of the sample obtained in step 6, and both sides are clamped by quartz glass sheets and placed in a tube furnace with a nitrogen atmosphere purity ≥ 99.99%. The temperature was raised to 1075°C/min, held for 30 minutes, cooled to 500°C at a cooling rate of 3°C/min, and then cooled naturally to prepare AlN ceramic copper-clad substrates for power electronic devices.

The finally obtained AlN ceramic copper-clad substrate for power electronic devices has a peel strength of ≥11N/mm, a surface square resistance of ≤2.6mΩ/□, and a thermal conductivity of >200W/m·k.

Example 3

A method for preparing an AlN ceramic copper-clad substrate for power electronic devices, comprising the following steps:

Step 1, the process of synthesizing the organic carrier: using ethyl cellulose as a thickener, terpineol as a solvent, and lecithin as an additive. The thickener, solvent, and additives are mixed in a beaker according to a certain ratio, and the organic vehicle is obtained after stirring and dissolving in a water bath at 95°C.

Step 2, Cu, Ti, Al slurry preparation process: Weigh the functional phase Cu, Ti, Al powders in proportion and mix them with the corresponding proportion of organic carrier in a sealed tank, grind and mix on a tank mill at 150r/min for 6h, Prepare Cu, Ti, Al slurry.

Step 3: The 0.5 mm AlN substrate is ultrasonically cleaned with acetone, alcohol, and deionized water for 15 minutes each, and dried for later use.

Step 4. Apply the copper-titanium-aluminum slurry obtained in step 2 evenly on the surface of the AlN obtained in step 3 by a manual screen printing machine, and then dry it in a blast drying oven at 60°C for 30 minutes. After drying, brush the AlN substrate in the same way Dry the other side for later use.

Step 5. Heat the double-sided printed AlN ceramic sheet obtained in step 4 to 350° C. for 1 hour in a muffle furnace at a rate of 3° C./min.

Step 6. Place the sample obtained in step 5 in an air atmosphere tube furnace, pass nitrogen gas at a rate of 300 sccm for 1 hour, and at the same time raise the temperature to 1070°C at a heating rate of 3°C/min, keep it warm for 0.5h, and cool down at a cooling rate of 3°C/min Cool down naturally after reaching 500°C. The obtained Cu, Ti, Al film thickness is 26 μm.

Step 7. After the Cu foil with a thickness of 350 μm is ultrasonically cleaned and dried with absolute ethanol, it is attached to both sides of the sample obtained in step 6, and both sides are clamped by quartz glass sheets and placed in a tube furnace with a nitrogen atmosphere purity ≥ 99.99%. The temperature was raised to 1073°C/min, held for 45 minutes, cooled to 500°C at a cooling rate of 3°C/min, and then cooled naturally to prepare AlN ceramic copper-clad substrates for power electronic devices.

The finally obtained AlN ceramic copper-clad substrate for power electronic devices has a peel strength of ≥13N/mm, a surface square resistance of ≤1.8mΩ/□, and a thermal conductivity of >200W/m·k.

Claims (3)

1. The AlN ceramic copper-clad base plate for the power electronic device is characterized by comprising an AlN substrate, cu, ti, al films and Cu foils, wherein the Cu, ti and Al films are coated on the surface of AlN, and the Cu foils are coated on the Cu, ti and Al films;

the Cu, ti and Al film is prepared by uniformly mixing micron-sized 60-80% of Cu, 1-10% of Ti and 10-30% of Al metal powder with an organic carrier to obtain copper-titanium-aluminum slurry without a glass phase, coating the copper-titanium-aluminum slurry on the surface of AlN ceramic by a screen printing mode, and sintering in an atmosphere, wherein the organic carrier is prepared by uniformly mixing terpineol, ethyl cellulose and lecithin, and the proportion of the copper-titanium-aluminum slurry is 60-80% of metal powder functional phase and 20-40% of organic carrier.

2. The AlN ceramic copper-clad substrate for the power electronic device as claimed in claim 1, wherein the atmosphere sintering is to sinter an AlN ceramic sheet with Cu, ti and Al films screen-printed on both sides in a muffle furnace in an air atmosphere at 240-350 ℃ for 1-3 h, then introduce nitrogen into an air atmosphere tube furnace at a gas flow rate of 100-300sccm for 1-3 h, heat the AlN ceramic sheet to 1050-1070 ℃ at a heating rate of 3 ℃/min for 0.5-2h, naturally cool the AlN ceramic sheet to 500 ℃ at a cooling rate of 3 ℃/min to obtain the Cu, ti and Al films, and the thickness of the Cu, ti and Al films is 20-30 μm.

3. The AlN ceramic copper-clad substrate for the power electronic device as claimed in claim 1, wherein the Cu foil is coated by heating to 1070-1080 ℃ at a heating rate of 3 ℃/min in a tube furnace with a nitrogen atmosphere purity of more than or equal to 99.99%, preserving the temperature for 10-60min, controlling the cooling rate to be 3 ℃/min, cooling to 500 ℃ and then naturally cooling, wherein the thickness of the Cu foil is 300-400 μm.

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