Preparation method and application of ceramic slurry for high-temperature bonding of aluminum nitride ceramic

Abstract

The invention provides a preparation method and application of ceramic slurry for high-temperature bonding of aluminum nitride ceramics, and relates to the technical field of high-temperature ceramic materials.The preparation method comprises the following steps that firstly, an organic carrier is prepared, a polymer binder, an organic solvent, a plasticizer and a dispersing agent are weighed according to the weight ratio and stirred at the temperature of 60-70 DEG C till complete dissolution and clarification are achieved for use; 2, an inorganic functional phase is prepared, aluminum nitride powder, yttrium oxide powder and alkaline earth metal oxide powder are weighed according to the weight proportion and placed in a ball milling tank to be evenly mixed, the obtained ceramic slurry serves as a bonding layer, the tolerable temperature can reach 1000 DEG C or above and is far higher than that of metal brazing filler metal, and the ceramic slurry is suitable for severe environments such as aerospace and high-temperature sensors. The main components of the bonding layer are consistent with the base material, and the thermal expansion coefficient is highly matched, so that the thermal stress can be greatly relieved, and the failure of the device caused by thermal fatigue in the temperature cycle is avoided.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of high-temperature ceramic materials, in particular to a ceramic slurry preparation method for high-temperature bonding of aluminum nitride ceramics and application thereof. BACKGROUND

[0002] Aluminum nitride ceramics are widely used in electronic packaging due to their excellent thermal conductivity and electrical insulation. In the manufacture of complex devices, it is often necessary to reliably bond multiple aluminum nitride components. The existing technology mainly relies on metal-based filler metals, such as silver-copper-titanium (Ag-Cu-Ti) alloy. This type of filler metal achieves connection by melting and penetrating and undergoing limited chemical reaction with the ceramic. However, metal-based filler metals have inherent defects: 1. Insufficient temperature resistance: the maximum use temperature is usually not more than 600℃, and it cannot work stably for a long time in harsh environments at higher temperatures (such as above 800℃).

[0003] 2. Thermal expansion mismatch: the difference in thermal expansion coefficients between metal and ceramic is large, and in severe temperature cycling, the connection interface will produce a large thermal stress, causing deformation, cracking or connection failure of the components.

[0004] 3. Insulation problem: the metal-based connection body itself is conductive, and cannot be applied to occasions that require insulating bonding, such as embedding sensitive elements such as resistance wires near the bonding layer. SUMMARY

[0005] (I) Technical problems solved In view of the deficiencies of the prior art, the present application provides a ceramic slurry preparation method for high-temperature bonding of aluminum nitride ceramics and application thereof, which solves the problems of insufficient temperature resistance, thermal expansion mismatch and insulation of metal-based filler metals in the prior art.

[0006] (II) Technical solutions To achieve the above purpose, the present application is implemented by the following technical solutions: a ceramic slurry preparation method for high-temperature bonding of aluminum nitride ceramics, comprising the following steps: Step 1, preparation of organic carrier Polymer binder, organic solvent, plasticizer and dispersant are weighed according to the proportion by weight, stirred at 60-70℃ until completely dissolved and clarified, and reserved; Step 2, preparation of inorganic functional phase Aluminum nitride powder, yttrium oxide powder and alkaline earth metal oxide powder are weighed according to the proportion by weight, mixed uniformly in a ball mill pot; Step 3, preparation of slurry The inorganic functional phase and the organic carrier obtained above are mixed according to the weight ratio of 75-90:10-25, dispersed by a three-roll mill to obtain a ceramic slurry.

[0007] Preferably, the inorganic functional phase is composed of the following components by weight percentage: aluminum nitride powder 80%-90%, yttrium oxide powder 5%-15%, alkaline earth metal oxide powder 5%-8%.

[0008] Preferably, the alkaline earth metal oxide powder is calcium oxide and / or magnesium oxide, and the aluminum nitride powder is spherical or near-spherical powder with a particle size in the range of 1.0-3.0 μm.

[0009] Preferably, the organic carrier is composed of the following components by weight percentage: polymeric binder 8%-15%, organic solvent 80%-88%, plasticizer 3%-8%, dispersant 0.5%-2%.

[0010] Preferably, the polymeric binder is one or a mixture of both of polyvinyl butyral and ethyl cellulose, the organic solvent is a mixture of terpineol, butyl carbitol and ethanol, the plasticizer is dibutyl phthalate or polyethylene glycol, and the dispersant is fish oil, castor oil or phosphate ester dispersant.

[0011] The application of a ceramic slurry prepared by a preparation method of a ceramic slurry for high-temperature bonding of aluminum nitride ceramics, which is applied to the surface of aluminum nitride ceramic parts to be bonded by means of screen printing or dot coating, the parts are aligned and attached, and degassing and high-temperature sintering are performed via temperature rise under the pressure of a clamp to achieve ceramic-ceramic bonding.

[0012] (Three) beneficial effects The application provides a preparation method of a ceramic slurry for high-temperature bonding of aluminum nitride ceramics and application thereof. 1. Excellent high-temperature resistance: the bonding layer is of ceramic structure, and can resist a temperature of 1000°C or above, which is much higher than that of metal solder, and is suitable for use in harsh environments such as aerospace and high-temperature sensors.

[0013] 2. Good thermal matching: the main components of the bonding layer are consistent with the base material, and the thermal expansion coefficients are highly matched, which can greatly relieve thermal stress and avoid failure of the device due to thermal fatigue in temperature cycling.

[0014] 3. High insulation reliability: the entire connecting body is a ceramic medium, and has excellent insulation performance, and is particularly suitable for use in precise circuit or component embedding scenarios requiring electrical insulation.

[0015] 4. High bonding strength: liquid phase sintering formed by yttrium oxide and other additives realizes firm chemical bonding, and has high bonding strength and good air tightness. DETAILED DESCRIPTION

[0016] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments of the present application, all other embodiments obtained by a person of ordinary skill in the art without creative effort belong to the scope of the present application.

[0017] The embodiment of the present application provides a ceramic slurry preparation method for high-temperature bonding of aluminum nitride ceramics, comprising the following steps: Step one, preparing an organic carrier The polymer binder, organic solvent, plasticizer and dispersant are weighed according to the weight ratio, stirred at 60-70 DEG C until completely dissolved and clarified, and prepared for use; Step two, preparing an inorganic functional phase The aluminum nitride powder, yttrium oxide powder and alkaline earth metal oxide powder are weighed according to the weight ratio, mixed uniformly in a ball mill tank, and prepared for use; Step three, preparing a slurry The inorganic functional phase and the organic carrier obtained above are mixed according to the weight ratio of 75-90:10-25, dispersed by a three-roll mill, and a ceramic slurry is obtained.

[0018] The inorganic functional phase is composed of the following components by weight percentage: aluminum nitride powder 80%-90%, yttrium oxide powder 5%-15%, and alkaline earth metal oxide powder 5%-8%. The alkaline earth metal oxide powder is calcium oxide and / or magnesium oxide. The aluminum nitride powder in the above is the main matrix, which ensures the consistency of the bonding layer and the aluminum nitride ceramic substrate in physical and chemical properties. It is a spherical or near-spherical powder with a particle size of 1.0-3.0 μm, which ensures the flow leveling and densification of the slurry. The yttrium oxide powder is a sintering aid, which can react with aluminum oxide on the surface of aluminum nitride particles at high temperature to form yttrium aluminate liquid phase, promote the sintering and densification between particles, and is the key to realize high-strength ceramic-ceramic bonding. The particle size D50 should be no larger than the particle size of the aluminum nitride powder, preferably 0.5-1.5 μm, to ensure sufficient dispersion and reaction. The alkaline earth metal oxide powder acts as an auxiliary sintering agent, which cooperates with yttrium oxide to further reduce the eutectic sintering temperature of the system and improve the sintering efficiency.

[0019] The organic carrier is composed of the following components by weight percentage: polymer binder 8%-15%, organic solvent 80%-88%, plasticizer 3%-8%, dispersant 0.5%-2%. The polymer binder is one or a mixture of both of polyvinyl butyral or ethyl cellulose, used to provide green strength after the slurry is dried; the organic solvent is terpineol, butyl carbitol or their mixed solvent with ethanol, used to dissolve the polymer and adjust the viscosity of the slurry; the plasticizer is dibutyl phthalate or polyethylene glycol, used to increase the flexibility of the film after the slurry is dried; the dispersant is fish oil, castor oil or phosphate ester dispersant, used to prevent the agglomeration of inorganic powder and ensure the uniformity and stability of the slurry.

[0020] The application of a ceramic slurry prepared by a preparation method of a ceramic slurry for high-temperature bonding of aluminum nitride ceramics, the ceramic slurry is applied to the surface of the aluminum nitride ceramic parts to be bonded by screen printing or spot coating, the parts are aligned and attached, and the ceramic-ceramic bonding is achieved through degassing and high-temperature sintering under the pressure of the clamp through temperature rising.

[0021] An inorganic functional phase (85% aluminum nitride powder, 10% yttrium oxide powder, 5% calcium oxide powder) and an organic carrier (10% ethyl cellulose, 85% terpineol, 4% dibutyl phthalate, 1% fish oil dispersant) are prepared in a weight ratio of 90:10, and the organic carrier is prepared by stirring ethyl cellulose, terpineol, plasticizer and dispersant at 65°C until completely dissolved.

[0022] Inorganic functional phase mixing: AlN, Y2O3, CaO are mixed in proportion by ball milling for 2 hours to ensure uniformity.

[0023] Slurry preparation: mix the inorganic phase with the organic carrier in a ratio of 90:10, disperse 3 times with a three-roll mill to obtain a stable slurry.

[0024] Coating and bonding: screen printing is used to coat the ceramic slurry on the surface of the AlN ceramic sheet, and 0.5 MPa pressure is applied after alignment and attachment.

[0025] Sintering process: Rising rate: 2°C / min to 600°C, degassing stage for 2 hours; Continue to rise to 1700°C, keep for 1 hour under nitrogen atmosphere; Cool naturally to room temperature.

[0026] High-temperature performance test: Purpose of the experiment: to verify the structural stability of the bonding layer in an environment above 1000°C.

[0027] Experimental method: The bonding sample was placed in a high temperature furnace, and was kept at 1000℃, 1100℃ and 1200℃ respectively for 24 hours. The evaluation results showed that the mass loss was less than 1%, there was no crack or delamination, and the shear strength retention rate was greater than or equal to 90%. Thermal expansion matching test: Purpose of the experiment: verify the thermal expansion consistency between the bonding layer and the AlN substrate; Experimental method: The thermal expansion coefficient (CTE) of the AlN substrate and the bonding layer was tested using a thermal mechanical analyzer (TMA); Temperature range: room temperature to 800℃, compare the CTE difference: CTE difference ≤ 0.5×10 -6 / ℃, no interface cracking after thermal cycle test (-55℃-200℃, 100 times).

[0028] Insulation performance test: Purpose of the experiment: verify the insulation reliability of the bonding layer under high voltage.

[0029] Experimental method: Prepare a sandwich structure (AlN / bonding layer / AlN); use a high resistance meter to test the volume resistivity; test continuously at 300℃, 500V direct current voltage for 1 hour.

[0030] Evaluation index: volume resistivity ≥ 10 14 Ω·cm; no breakdown, no leakage.

[0031] Bonding strength test Purpose of the experiment: evaluate the mechanical strength of the bonding layer.

[0032] Experimental method: shear test (ASTM D905) was used, sample size was 10×10×2mm, test speed was 1mm / min, 5 samples were tested for each group, and the average value was taken.

[0033] Evaluation index: shear strength ≥ 30MPa; fracture analysis: interface fracture rate <20%.

[0034] HTCC packaged device simulation experiment: Purpose of the experiment: verify the applicability of the slurry in HTCC multilayer ceramic packaging.

[0035] Experimental design: prepare an AlN multilayer structure (3 layers), embed resistance wire (Pt) in the middle layer, use the slurry for interlayer bonding, and test the resistance change, insulation, and thermal cycle performance after sintering.

[0036] Evaluation index: resistance change rate <5%, insulation resistance ≥ 10 13 Ω, no interlayer peeling after thermal cycle (-40℃-150℃, 500 times).

[0037] Aerospace electronic packaging simulation experiment: Purpose of the experiment: to verify the reliability of the paste in high altitude, high temperature, strong vibration environment.

[0038] Experimental design: place the bonding sample in a comprehensive environmental test chamber, simulate conditions: temperature -55℃-200℃, humidity 95%, vibration 10-2000Hz, continuous test for 72 hours.

[0039] Evaluation index: shear strength retention rate ≥85%; no cracks, no electrical performance degradation, no air holes and no delamination by X-ray detection.

[0040] High temperature sensor packaging experiment Purpose of the experiment: to verify the applicability of the paste in thermocouple / pressure sensor packaging.

[0041] Experimental design: prepare AlN packaging shell, package thermocouple inside, use paste to seal the cover, work continuously at 800℃ for 100 hours, record signal drift.

[0042] Evaluation index: signal drift <1%; leak tightness (helium mass spectrometry leak detection) ≤1×10 -9 Pa·m 3 / s; insulation resistance ≥10 12 Ω.

[0043]

[0044] This study verifies the performance indicators of aluminum nitride ceramic high temperature bonding paste through systematic experiments, proving that it has excellent high temperature resistance (≥1100℃), good thermal matching with AlN matrix, high insulation reliability, strong bonding ability, and wide adaptability in HTCC, aerospace, high temperature sensor and other fields. The paste can replace traditional metal solder and become one of the core technologies of the new generation of high temperature ceramic bonding materials Although embodiments of the present application have been shown and described, it is to be understood that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the present application, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for preparing a ceramic slurry for high-temperature bonding of aluminum nitride ceramics, characterized in that, Includes the following steps: Step 1: Preparation of organic carriers Weigh out the polymer binder, organic solvent, plasticizer and dispersant according to the weight ratio, stir at 60℃-70℃ until completely dissolved and clear, and set aside for later use; Step 2: Prepare inorganic functional phases Weigh out aluminum nitride powder, yttrium oxide powder and alkaline earth metal oxide powder according to the weight ratio, and mix them evenly in a ball mill jar; Step 3: Prepare the slurry The inorganic functional phase and the organic carrier obtained above are mixed at a weight ratio of 75-90:10-25 and dispersed through a three-roll mill to obtain a ceramic slurry.

2. The method for preparing a ceramic slurry for high-temperature bonding of aluminum nitride ceramics according to claim 1, characterized in that, The inorganic functional phase is composed of the following components by weight percentage: 80%-90% aluminum nitride powder, 5%-15% yttrium oxide powder, and 5%-8% alkaline earth metal oxide powder.

3. The method for preparing a ceramic slurry for high-temperature bonding of aluminum nitride ceramics according to claim 2, characterized in that: The alkaline earth metal oxide powder is calcium oxide and / or magnesium oxide, and the aluminum nitride powder is spherical or near-spherical powder with a particle size in the range of 1.0-3.0 μm.

4. The method for preparing a ceramic slurry for high-temperature bonding of aluminum nitride ceramics according to claim 3, characterized in that, The organic carrier is composed of the following components by weight percentage: 8%-15% polymer binder, 80%-88% organic solvent, 3%-8% plasticizer, and 0.5%-2% dispersant.

5. The method for preparing a ceramic slurry for high-temperature bonding of aluminum nitride ceramics according to claim 4, characterized in that: The polymer binder is one or a mixture of two of polyvinyl butyral or ethyl cellulose; the organic solvent is terpineol, butyl carbitol, or a mixture thereof with ethanol; the plasticizer is dibutyl phthalate or polyethylene glycol; and the dispersant is fish oil, castor oil, or a phosphate ester dispersant.

6. The application of the ceramic slurry prepared by the method for high-temperature bonding of aluminum nitride ceramics according to any one of claims 1-5, characterized in that: The ceramic slurry is applied to the surface of the aluminum nitride ceramic parts to be bonded by screen printing or dot coating. The parts are aligned and bonded together. Under the pressure of the clamp, the adhesive is removed and high-temperature sintering is carried out to achieve ceramic-ceramic bonding.

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