abstract
A preparation method for forming a high thermal conductivity aluminum nitride ceramic substrate
- The surface mixing modification of aluminum nitride powder;
- Take a certain proportion of the modified aluminum nitride powder, dispersant, plasticizer, binder and mix
Uniform and full;
- Soak it in a vacuum;
- The preparation of raw billet adopts the combination process of automatic horizontal extension forming and cold isostatic pressure forming;
- Rubber and wax, in 200℃ ~470℃ for 2~3h;.1.1
- .1 Sintered 4~5.8h from 1700℃ to 1950℃ in a nitrogen-protected environment. The solvent used was pure water with low conductivity ampere
Full, green, environmental protection, 1.5~2 hours of slurry stability, the flow molding ceramic substrate with high thermal conductivity; simple process, and low production cost, can be used in high power density circuit, IGBT and other fields.
1. A method for preparing a highly thermal conductive aluminum nitride ceramic substrate, comprising the following steps:
1) Surface modification of aluminum nitride powder: select a certain proportion of raw materials aluminum nitride, alumina, aluminum dihydrogen phosphate, ball grinding for 10h, to obtain modified aluminum nitride and alumina powder;
2) Ingredients: weigh the modified aluminum nitride and alumina powder, sintering additives, dispersant, plasticizer, binder, ball grinding 10h~18h, to get the flow extension slurry;
3) Vacuum deoaming: add anoaming agent to the flow slurry for vacuum deoaming;
4) Preparation of raw billet: the combination of flow molding and cold isostatic pressing molding to obtain ceramic billet;
5) Rubber ining: the ceramic billet is 200℃ ~450℃ for 2~3h;
6) Sintered: sintering the raw ceramic billet at 1600℃ ~1750℃ for 4~6h under nitrogen atmosphere.
2. According to the requirements 1 of a preparation method of high thermal conductivity aluminum nitride ceramic substrate, which is characterized by: step 1) of alumina in 2 wt%, mass of dihydrogen phosphate 3.9 wt%, grinding medium amount of absolute ethanol, grinding ball for alumina, raw material powder: absolute ethanol: grinding ball mass ratio 1:1:4..1
3. A preparation method for forming a highly thermal conductive aluminum nitride ceramic substrate according to requirement 2, characterized in that the aluminum nitride powder described in step 1), the purity of the aluminum nitride powder is 95% to 99% and the particle size is 0.8 μ m to 1.2 μ m, iron, impurity content less than 78ppm, oxygen element content less than 1.5%..5.5
4. A method for preparing a high-conductivity aluminum nitride ceramic substrate according to requirement 1, characterized in that the step 2) is one or more of yttrium oxide, dysprosium oxide, lithium carbonate, the dispersant is citric amine, the plasticizer is propylene glycol, and the binder is polyvinyl alcohol.
5. A preparation method of high thermal conductivity aluminum nitride ceramic substrate according to requirement 1, characterized by: step 2): 62 ~68 parts of modified aluminum nitride powder, dispersant 1.5 ~4.5 parts, plasticizer 7 ~11 parts, binder 2 ~5 parts, 2 ~9 parts of sintering agent.
6. A method for preparing a high thermal conductive aluminum nitride ceramic substrate according to requirement 1, characterized in: step 3) The defoaming agent is n-butanol and the vacuum de-foaming condition is: the vacuum degree is-0.0039～-0 . At 11MPa, the mixing paddle speed was 22 r/min, the vacuum de-bubble time ranged from 12 to 21 min, and the viscosity ranged from 2100 to 6200 cps.
7. A method for preparing a high-thermal conductive aluminum nitride ceramic substrate according to requirement 1, characterized in the step 4) In the flow molding, the height of the flow machine scraper is 0. From 5 to 5 mm, the flow extension velocity is from 110 to 450 mm / min.
8. A method for preparing a high thermal conductive aluminum nitride ceramic substrate according to requirement 7, characterized in step 4) an isostatic pressure of 60 to 110 Mpa and a pressure retention time of 6 to 11 min.
9. A method for preparing a high thermal conductive aluminum nitride ceramic substrate according to requirement 1, characterized by step 5) the warming rate before 180℃ is 0.9℃ / min; 200℃ to 450℃ is 0.35℃ / min; 450℃ thermal insulation for 1.1h; 450℃ ~600℃ for 1℃ / min. Finally, at 600℃ for 4h.
A preparation method for forming a high thermal conductivity aluminum nitride ceramic substrate
technical field
A preparation method for flow forming high thermal conductivity aluminum nitride ceramic substrate belongs to the field of flow forming technology.
Background technology
Aluminum nitride (AlN) ceramics with high thermal conductivity (close to silicon carbide and beryllium oxide, 5-10 times of alumina), low dielectric constant and dielectric loss, good electric insulation characteristics and thermal expansion coefficient matched with silicon, gallium arsenide, is a very popular material in the electronic industry in recent years. Compared with beryllium oxide ceramics, aluminum nitride ceramics are not toxic and have a lower production cost, making them an ideal packaging material in the field of high power density circuit and IGBT.
At present, aluminum nitride ceramic sheet is mainly prepared by flow forming method, whose production cost is low and high production efficiency. Extension forming is mainly divided into traditional non-flow forming and flow forming. Because aluminum nitride powder is easy to hydrolysis when encountering water, the development of flow forming is seriously hindered. However, the non-flow molding process than the flow molding, the cost is higher, and the volatile organic matter will cause environmental pollution. In addition, most of the organic matter is flammable, and there will be some safety risks in the process of use. Therefore, it is a good choice to use flow extension instead of non-flow extension. The biggest characteristic of flow extension is to use water as a solvent to avoid the use of toxic organic solvent. However, due to the large surface tension of water solvent, the infiltration of powder is poor, and it is easy to produce bubbles. In addition, the blank body is easy to crack in the process of glue. A waterborne fluid slurry includes water, mixed powder, sodium alginate, dispersant and waterborne epoxy resin. The solvent of the prepared fluid slurry is water, which is safe and environmentally friendly, has no bubbles, and the delayed fluid film has good strength and toughness. However, the thermal conductivity of the aluminum nitride ceramic substrate is not ideal.
content
The main problem is to provide a preparation method of high thermal conductivity aluminum nitride ceramic substrate, the aluminum nitride ceramic substrate is prepared by flow molding method, reducing the use of organic solvents, safe, green and environmentally friendly. At the same time, the process is simple, and the production cost is low, the slurry stability is good, the ceramic substrate thermal conductivity is high (185W / m ˙ K~220W / m ˙ K).
To solve the above technical problems, the following technical solution is adopted:
A method for preparing a highly thermal conductive aluminum nitride ceramic substrate comprising the following steps:
1) Surface modification of aluminum nitride powder: weighing the raw materials aluminum nitride, alumina, aluminum dihydrogen phosphate, ball grinding for 11~12h, to obtain the modified aluminum nitride powder;
2) Ingredients: weigh the modified aluminum nitride powder, sintering agent, dispersant, plasticizer, binder, ball grinding 12h~ 20h, to get the flow slurry;
3) Vacuum deoaming: add anoaming agent to the flow slurry for vacuum deoaming;
4) Preparation of raw billet: the combination of flow molding and cold isostatic pressing molding to obtain ceramic billet;
5) Rubber ining: the ceramic billet is 200℃ ~450℃ for 2~3h;
6) Sintered: sintering the raw ceramic billet at 1600℃ ~1750℃ for 4~6h under nitrogen atmosphere.
In step 1), the mass fraction of alumina is 2 wt%, and the mass fraction of aluminum dihydrogen phosphate is 4 wt%, grinding
The medium is anhydrous ethanol, grinding ball is alumina, raw material powder: absolute ethanol: grinding ball mass ratio =1:1:4..1.1.2
The purity of the aluminum nitride powder is 96% to 99%, and the particle size is 0.8 μ m to 1.0 μ m, Fe impurity content less than 81ppm, O content less than 1.0%.
Step 2) The sintering agent is one or several of yttrium oxide, dysprosium oxide or lithium carbonate, the dispersant is citrate amine, the plasticizer is propylene alcohol, and the binder is polyvinyl alcohol. Step 2) In the material according to the mass fraction ratio: 60 ~70 parts of modified aluminum nitride powder, 0.5 ~3.5 parts of dispersant, 6 ~12 parts of plasticizer, 3 ~6 parts of binder, 1 ~10 parts of sintering agent.
Step 3) The defoaming agent is n-butanol, the vacuum de-foaming conditions are: the vacuum degree is-0.03~-0.1MPa, the mixing paddle speed is 22 r/min, the vacuum defoaming time is 10~20min, and the viscosity is 2000 ~ 6000 cps.
Step 4) The height of the control extension scraper is 0.4~5mm, the extension speed is 100~500mm / min, get 0.2~ 1mm blank, and then the pressure of 50 ~ 120 Mpa, pressure for 5~10min.
Step 5) Heating rate is 1℃ / min before 210℃; 210℃ ~480℃ is 0.35℃/min；.1
.5450℃ insulation for 1h; 450℃ ~600℃ for 1℃ / min. Finally, at 650℃ for 4h.
Compared with the existing art, it basically has the following advantages:
1) This method is prepared by flow extension method, which is simple and uses water instead of organic solvent, which is safe, green and environmentally friendly;
2) Using aluminum oxide and dihydrogen phosphate to surface modify aluminum nitride powder, by forming a film on the surface of aluminum nitride powder to prevent the hydrolysis of aluminum nitride, the obtained aluminum nitride powder has good dispersion and excellent hydrolysis resistance;
3) Propanalcohol is used as the plasticizer of the flow slurry, which can make the flow slurry have good wetting property, and the obtained flow 4) The aluminum nitride ceramic substrate is 185W / m ˙ K~225W / m ˙ K.
(Note: The above preparation method is for reference only, due to environmental changes and process deviation)
The following is the flow chart of the preparation method of aluminum nitride ceramic substrate:
├─ [Step 1] Surface modification of aluminum nitride powder
│ ├─ [Raw material] Take the raw material aluminum nitride, alumina, aluminum dihydrogen phosphate
│ ├─ [Ball grinding] Ball grinding for 11~12h to obtain modified aluminum nitride powder
│ └─ [Aluminum oxide mass fraction] 2 wt%
│ └─ [Mass fraction of aluminum dihydrogen phosphate] 4 wt%
├─ [Step 2] Ingredients
│ ├─ [Weigh] modified aluminum nitride powder, sintering agent, dispersant, plasticizer, binder
│ ├─ [Ball grinding] Ball grinding for 12h~ 20h to obtain the flow extension slurry
│ ├─ [Sintering agent] yttrium oxide, dysprosium oxide, or lithium carbonate
│ ├─ [Dispersant] citric amine
│ ├─ [Plasticizer] propylene glycol
│ ├─ [Binder] polyvinyl alcohol
│ └─ [Mass fraction ratio of each material]
│ ├─ Of ~ 60 parts and ~70 parts of the modified aluminum nitride powder
│ ├─. From 0.5 to 3.5 copies
│ ├─ Plasplasticizer 6 ~12 copies
│ ├─ Binder in 3 parts and ~6 copies
│ └─ Sintering auxiliary agent in 1 part and ~10 copies
└─ [Step 3] Vacuum de-aming
├─ [Add] Add anoaming agent to the slurry for vacuum debaming
└─ [Defowolding agent] n-butanol
└─ [Vacuum defoaming conditions]
├─ Vacuum degree: -0.03~-0.1MPa
├─ Driving paddle speed: 22r / min
├─ Vacuum defoaming time: 10~20min
└─ [Viscosity] 2000 to 6000 cps
[Step 4], the preparation of raw blanks
├─ [Process] Using flow molding and cold isostatic molding combined to obtain ceramic billet
├─ [Control flow machine scraper height] 0.4~5mm
├─ [Flow extension velocity] 100~500mm / min
└─ [Body size] 0.2~ 1mm
[Step 5] for glue release
├─ [Process conditions] Heating rate is 1.1℃ / min before 210℃; 210℃ ~480℃ is 0.35℃ / min; 450℃ thermal insulation for 1.5h; 450℃ ~600℃ for 1℃ / min. Finally, at 650℃ for 4h.
└─ [Temperature range] from 200℃ to 450℃
[Step 6] Sintering
├─ [Atmosphere] for sintering under a nitrogen atmosphere
└─ [Temperature range] 1600℃ ~1750℃
└─ [Time from] 4 to 6 h.