A PTC ceramic sintering sagger and use method thereof

Abstract

The present invention belongs to the technical field of electronic components, and specifically provides a PTC ceramic sintering sagger and a method for using the same. The graphite strips playing a supporting role between the upper cover plate and the bowl body of the sintering sagger are used to ensure the air permeability of the sintering sagger in the debinding stage, so that the organic matter added in the granulation process can be fully discharged after thermal decomposition. During use, the temperature is increased in stages to ensure the discharge of organic additives in the debinding stage, and then the temperature is increased to gradually oxidize and consume the graphite strips. The upper cover plate falls and forms a sealing structure with the bowl body. After entering the sintering high temperature zone, the sealed sintering sagger ensures the consistency of the internal temperature. After the sintered block experiences a higher sintering temperature, it is kept warm at a lower temperature, which suppresses the rapid movement of the grain boundary, and can obtain a sintered block with fine and uniform grains, and finally obtain a PTC ceramic with a dense structure, uniform grain size, uniform resistance distribution, and low edge color abnormality rate.

Description

Technical Field

[0001] The invention belongs to the technical field of electronic components, and in particular relates to a PTC ceramic sintering sagger and a use method thereof. Background Art

[0002] Positive temperature coefficient ceramics, referred to as PTC ceramics, are widely used in various fields. During the granulation process of PTC powder, a certain proportion of PVA is added to increase the fluidity of the powder during the molding process to ensure the strength of the molded green sheet. In order to avoid the added organic matter affecting the product performance, debinding is generally performed before sintering or during the sintering process. The existing sintering sagger is usually non-sealed to ensure that the organic matter can be fully discharged during the debinding process. This non-sealed design will cause occasional abnormal color of the edge of the ceramic sheet due to uneven heat during the sintering process, and the sintering resistance of different parts is dispersed. To this end, the present invention designs a PTC ceramic sintering sagger, reserves holes on the bowl body and the upper cover plate, supports the cover plate with graphite columns, and realizes full ventilation of the sintering container during the debinding stage through a staged heating process, ensuring that the organic matter is fully discharged. After passing the debinding temperature zone, the temperature continues to rise, so that the graphite reacts with oxygen and is gradually consumed, ensuring that the cover plate seals the bowl body during the sintering stage, avoiding abnormal color of the ceramic edge caused by uneven temperature, and increasing the concentration of the sintering resistance. Summary of the invention

[0003] The purpose of the present invention is to overcome the problems in the prior art of uneven sintering heat, abnormal color of the edge of the ceramic sheet, and dispersed sintering resistance values ​​at different parts.

[0004] To this end, the present invention provides a PTC ceramic sintering sagger, comprising: a sagger body, an upper cover plate and a plurality of graphite strips; wherein the top opening edge of the sagger body and the bottom of the upper cover plate are respectively provided with a plurality of corresponding reserved holes; and the plurality of graphite strips are respectively inserted between the corresponding reserved holes.

[0005] Specifically, a protruding component that matches the opening of the bowl body is provided at the bottom of the upper cover plate. When the graphite strip is pulled out, the upper cover plate falls down and forms a sealing structure with the bowl body.

[0006] The present invention also provides a method for using the above-mentioned PTC ceramic sintering sagger, comprising the following steps:

[0007] S1. Using refractory materials to make the upper cover plate and the bowl body of the PTC ceramic sintering sagger;

[0008] S2. Place a zirconium oxide plate on the bottom of the bowl;

[0009] S3, insert the formed PTC blanks into the bowl body, sprinkle zirconium powder in the gaps between the blanks, use zirconium oxide plates to block the contact surface between the blanks and the bowl body, install graphite strips of corresponding specifications into the reserved holes on the top of the bowl body, and close the upper cover according to the positions of the corresponding reserved holes;

[0010] S4, debinding and sintering process: put the PTC ceramic sintering sagger into the sintering furnace, raise the temperature to the thermal decomposition zone at a uniform speed, and keep it warm for a period of time to allow the organic additives to be fully decomposed by heat; then raise the temperature to the debinding temperature zone at a uniform speed, and keep it warm for a period of time to carry out debinding; after the debinding is completed, raise the temperature to the graphite oxidation temperature zone at a uniform speed, and keep it warm for a period of time to allow the graphite strips to be completely oxidized and consumed, and the upper cover plate falls down to form a sealing structure with the sagger; raise the temperature to the sintering high temperature zone at a uniform speed, and keep it warm for a period of time to complete the sintering of the PTC ceramics, and obtain the finished product after natural cooling.

[0011] Specifically, in the above step S4, the temperature of the debinding temperature zone is 595-605° C., the heating rate is 3-5° C. / min, and the heat preservation time is 115-125 min.

[0012] Specifically, in the above step S4, the graphite oxidation temperature range is 1090-1110° C., the heating rate is 3-5° C. / min, and the temperature is kept for 40-50 min.

[0013] Specifically, in the above step S4, the sintering high temperature zone is 1200-1400° C., the heating rate is 8-10° C. / min, and the heat preservation time is 10-120 min.

[0014] Specifically, the segmented heating process of the above step S4 is to place the PTC ceramic sintering sagger into the sintering furnace, uniformly heat it to 350±10℃ at a speed of 3-5℃ / min, and keep it warm for 32±5min; uniformly heat it to 600±5℃ at a speed of 3-5℃ / min, and keep it warm for 120±5min; uniformly heat it to 850±5℃ at a speed of 3-5℃ / min, and keep it warm for 45±5min; uniformly heat it to 1100±5℃ at a speed of 3-5℃ / min, and keep it warm for 45±5min; uniformly heat it to 1265-1270±2℃ at a speed of 8-10℃ / min, and keep it warm for 64±10min; uniformly cool it to 1240±5℃ at a speed of 2-3℃ / min, and keep it warm for 45±5min; uniformly cool it to 1140±5℃ at a speed of 3-5℃ / min, and keep it warm for 45±5min, and obtain the finished product after natural cooling.

[0015] Specifically, the refractory material used in the above step S1 is mullite or alumina.

[0016] Specifically, in the above step S2, the thickness of the zirconium oxide plate is ≥ 6 mm.

[0017] Specifically, in the above step S3, 50-80 mesh zirconium powder and 2-3 mm thick zirconium oxide plate are used.

[0018] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0019] (1) The PTC ceramic sintering sagger provided by the present invention utilizes graphite strips that play a supporting role between the upper cover plate and the sagger body, thereby ensuring the air permeability of the sintering sagger during the debinding stage, so that the organic matter added during the granulation process can be fully discharged after thermal decomposition; after the debinding stage, the temperature is increased to gradually oxidize and consume the graphite strips, and the upper cover plate falls down to form a sealed structure with the sagger body. After entering the sintering high-temperature zone, the sealed sintering sagger ensures the consistency of the internal temperature, avoids abnormal color of the edge of the PTC ceramic sheet caused by thermal radiation in the high-temperature zone, and improves the concentration of the sintering resistance value.

[0020] (2) The method for using the PTC ceramic sintering sagger provided by the present invention adopts a staged heating method. The purpose of each stage is: the PTC green body is heated from room temperature to the thermal decomposition temperature of additives such as PVA, and the temperature is kept for a period of time to fully pyrolyze the organic matter added in the granulation process, and then the temperature is raised to the debinding temperature zone to ensure that the thermal decomposition products of the organic additives can be fully discharged out of the sagger; the graphite strips will gradually oxidize and consume when the temperature is higher than 1000°C, so the temperature is uniformly raised to 1100±5°C and kept for 45±5min; after the graphite is completely oxidized and consumed, the upper cover plate falls down to form a sealing structure with the bowl body, and the temperature is uniformly raised to the sintering high temperature zone and kept for a period of time to complete the sintering of the PTC ceramic. At this time, the density of the sintered block reaches more than 75% of the theoretical density, so that all the pores in the sintered block are They are all in an unstable state, and then the temperature is uniformly reduced to 1240±5℃, kept warm for 45±5min, and then uniformly reduced to 1140±5℃, kept warm for 45±5min. At this time, the dynamic evolution of the microstructure is very slow, which can effectively inhibit the grain boundary migration, densify the sintered block, and reach the theoretical density. At the same time, it can also limit the abnormal growth of the particle size to ensure the uniformity of the grain size; through the staged heating method, after ensuring the discharge of organic additives and the oxidation and consumption of graphite, the sagger forms a closed structure in the high temperature zone, and the sintered block experiences a higher sintering temperature and then keeps warm at a lower temperature, which inhibits the rapid movement of the grain boundary, and can obtain a sintered block with fine and uniform grains, and finally obtain a PTC ceramic with dense structure, uniform grain size, uniform resistance distribution, and low edge color abnormality rate.

[0021] The present invention will be further described in detail below with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 The invention relates to a PTC ceramic sintering sagger.

[0023] Figure 2It is a front view of the PTC ceramic sintering sagger of the present invention.

[0024] Figure 3 It is a top view of the PTC ceramic sintering sagger body of the present invention.

[0025] Figure 4 It is a side view of the upper cover of the PTC ceramic sintering sagger of the present invention.

[0026] Figure numerals: 1. upper cover plate; 2. raised part; 3. reserved hole; 4. graphite strip; 5. bowl body; 6. opening. DETAILED DESCRIPTION

[0027] The technical scheme in the present invention will be clearly and completely described below in conjunction with the embodiments. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Although the representative embodiments of the present invention have been described in detail, it will be understood by those skilled in the art that various modifications and changes can be made to the present invention without departing from the scope of the present invention. Therefore, the scope of the present invention should not be limited to the embodiments, but should be limited by the attached claims and their equivalents.

[0028] like Figure 1-Figure 4 As shown, the present invention provides a PTC ceramic sintering sagger, comprising: an upper cover plate 1, a bowl body 5 and a plurality of graphite strips 4; wherein the edge of the top opening 6 of the bowl body 5 and the bottom of the upper cover plate 1 are respectively provided with a plurality of corresponding reserved holes 3; and the plurality of graphite strips 4 are respectively inserted between the corresponding reserved holes 3.

[0029] In order to improve the airtightness of the sintering crucible at high temperature, a protruding part 2 that matches the opening 6 of the bowl body 5 is provided at the bottom of the upper cover plate 2. When the graphite strip 4 is pulled out, the upper cover plate 1 falls down, and the protruding part 2 is buckled into the opening 6 of the bowl body 5 to form a sealing structure with the bowl body 5.

[0030] The present invention also provides a method for using the above-mentioned PTC ceramic sintering sagger, comprising the following steps:

[0031] S1, using refractory materials such as mullite and alumina to make the upper cover plate 1 and the bowl body 5 of the PTC ceramic sintering sagger of the present invention;

[0032] S2. Place a zirconia plate with a thickness of ≥6 mm on the bottom layer of the bowl body 5 to support the green body and prevent the green body from reacting with the bowl body during high temperature;

[0033] S3, put the formed PTC blanks into the bowl 5, sprinkle 50-80 mesh zirconium powder in the gap between the blanks, use a 2-3mm thick zirconium oxide plate to block the contact surface between the blanks and the bowl 5, install the graphite strips 4 of corresponding specifications into the reserved holes 3 on the top of the bowl 5, and close the upper cover according to the position of the corresponding reserved holes;

[0034] S4, debinding and sintering: put the PTC ceramic sintering sagger into the sintering furnace, uniformly heat it to 350±10℃, keep it warm for 32±5min, so that the organic additives can be fully decomposed by heat; then uniformly heat it to the debinding temperature zone of 595-605℃, keep it warm for 115-125min to debind; after debinding, uniformly heat it to the graphite oxidation temperature zone of 1090-1110℃, keep it warm for 40-50min, so that the graphite 4 is completely oxidized and consumed, and the upper cover plate 1 falls and forms a sealing structure with the bowl body 5; uniformly heat it to the sintering high temperature zone of 1200-1400℃, keep it warm for 10-120min, complete the sintering of the PTC ceramic, and obtain the finished product after natural cooling.

[0035] The effects of the PTC ceramic sintering sagger and the method of using the same of the present invention are studied below through specific examples.

[0036] Embodiment 1:

[0037] The method for using the PTC ceramic sintering sagger provided in this embodiment comprises the following steps:

[0038] S1. The upper cover plate and the bowl body of the square PTC ceramic sintering sagger are made of mullite, a reserved hole is set on each of the four sides of the top opening of the bowl body, and a reserved hole corresponding to the reserved hole of the bowl body is set at the bottom of the upper cover plate.

[0039] S2. Place a 6mm thick zirconium oxide plate on the bottom of the bowl;

[0040] S3, put the formed PTC blanks into the bowl body, sprinkle 50-80 mesh zirconium powder in the gap between the blanks, use a 2-3mm thick zirconium oxide plate to block the contact surface between the blanks and the bowl body, install the graphite strips of corresponding specifications into the reserved holes on the top of the bowl body, and close the upper cover according to the position of the corresponding reserved holes;

[0041] S4. In order to obtain PTC ceramics with dense structure and uniform grain size, debinding and sintering are carried out according to the following heating process: put the PTC ceramic sintering sagger into the sintering furnace, uniformly heat it to 350±10℃ at a speed of 3-5℃ / min, and keep it warm for 32±5min to allow the organic additives to be fully decomposed by heat; uniformly heat it to 600±5℃ at a speed of 3-5℃ / min, and keep it warm for 120±5min; uniformly heat it to 850±5℃ at a speed of 3-5℃ / min, and keep it warm for 45±5 min; uniformly heat to 1100±5℃ at a speed of 3-5℃ / min, and keep warm for 45±5min; uniformly heat to 1265-1270±2℃ at a speed of 8-10℃ / min, and keep warm for 64±10min; uniformly cool to 1240±5℃ at a speed of 2-3℃ / min, and keep warm for 45±5min; uniformly cool to 1140±5℃ at a speed of 3-5℃ / min, and keep warm for 45±5min, complete the PTC ceramic sintering, and obtain the finished product after natural cooling.

[0042] Comparative Example 1:

[0043] The same method as in Example 1 is used, except that a conventional non-sealed PTC ceramic sintering sagger is used in step S1.

[0044] The resistance, Curie temperature, pressure resistance and appearance of the PTC ceramic products obtained by firing in Example 1 and Comparative Example 1 were tested. Taking the pressure resistance of 0.3-0.4KΩ as an example, the pressure resistance performance of the finished products of Example 1 and Comparative Example 1 both passed the 380VAC, 3min requirement, and the Curie temperature @2*R25 was between 250-260°C; the resistance distribution results are shown in Table 1.

[0045] Table 1. Resistance distribution of PTC ceramic finished products

[0046]

[0047] Although the pressure resistance and Curie temperature of the finished ceramic products of Example 1 and Comparative Example 1 meet the requirements, it can be seen from Table 1 that the products fired using the PTC ceramic sintering sagger provided by the present invention in Example 1 and Example 2 all have resistance values ​​within 0.2-0.9 kΩ, which meets the requirements of PTC ceramics, and more than 80% of the finished products in Example 1 have resistance values ​​between 0.53-0.60 kΩ, while 0.67% of the finished products in Comparative Example 1 have resistance values ​​> 0.90 kΩ, which does not meet the production requirements, and the sintering resistance values ​​of different parts are more dispersed than those in Example 1; statistics on the number of ceramic finished products with abnormal edges in Example 1 and Comparative Example 1 show that there is basically no ceramic finished product with abnormal edge color in Example 1, while the color abnormality rate in Comparative Example 1 is as high as about 3%. It can be seen that the PTC ceramic sintering sagger provided by the present invention can reduce the color abnormality rate of the edge of the PTC sheet when sintering ceramics.

[0048] In summary, the PTC ceramic sintering sagger provided by the present invention utilizes the graphite strips that play a supporting role between the upper cover plate and the bowl body to ensure the air permeability of the sintering sagger in the debinding stage, so that the organic matter added in the granulation process can be fully discharged after thermal decomposition; after the debinding stage, the temperature is increased to gradually oxidize and consume the graphite strips, and the upper cover plate falls down to form a sealed structure with the bowl body. After entering the sintering high-temperature zone, the sealed sintering sagger ensures the consistency of the internal temperature, avoids the abnormal color of the edge of the PTC sheet caused by thermal radiation in the high-temperature zone, and improves the concentration of the sintering resistance; in the method of using the PTC ceramic sintering sagger, the temperature is increased in stages to ensure the discharge of organic additives, and the sagger forms a closed structure in the high-temperature zone after the graphite is oxidized and consumed. The sintered block is kept warm at a lower temperature after experiencing a higher sintering temperature, which suppresses the rapid movement of the grain boundary, and a sintered block with fine and uniform grains can be obtained, and finally a PTC ceramic with a dense structure, uniform grain size, uniform resistance distribution, and low edge color abnormality rate is obtained.

[0049] The above examples are merely illustrative of the present invention and do not constitute a limitation on the protection scope of the present invention. All designs that are the same or similar to the present invention fall within the protection scope of the present invention.

Claims

1. A PTC ceramic sintering sagger, characterized in that: include: An upper cover plate (1), a bowl body (5) and a plurality of graphite strips (4); wherein the edge of an opening (6) at the top of the bowl body (5) and the bottom of the upper cover plate (1) are respectively provided with a plurality of corresponding reserved holes (3); and the plurality of graphite strips (4) are respectively inserted between the corresponding reserved holes (3).

2. The PTC ceramic sintering sagger according to claim 1, characterized in that: The bottom of the upper cover plate (1) is provided with a raised component (2) that matches the opening (6) of the bowl body (5); when the graphite strip (4) is pulled out, the upper cover plate (1) falls down and forms a sealing structure with the bowl body (5).

3. A method for using a PTC ceramic sintering sagger, characterized in that: The following steps are involved: S1. Using refractory materials to manufacture the upper cover plate (1) and the bowl body (5) of the PTC ceramic sintering sagger as claimed in any one of claims 1 or 2; S2, placing a zirconium oxide plate on the bottom layer of the bowl body (5); S3, inserting the formed PTC blanks into the bowl (5), and sprinkling zirconium powder in the gaps between the blanks, using zirconium oxide plates to block the contact surface between the blanks and the bowl (5), installing graphite strips (4) of corresponding specifications into the reserved holes (3) at the top of the bowl (5), and closing the upper cover (1) according to the positions of the corresponding reserved holes (3); S4. Debinding and sintering are performed by adopting a staged heating process: the PTC ceramic sintering sagger is placed in a sintering furnace, and the temperature is uniformly increased to the thermal decomposition zone, and the temperature is kept for a period of time so that the organic additives in the PTC green sheet are fully decomposed by heat; then the temperature is uniformly increased to the debinding temperature zone, and the temperature is kept for a period of time to perform debinding; after the debinding is completed, the temperature is uniformly increased to the graphite oxidation temperature zone, and the temperature is kept for a period of time so that the graphite strip (4) is completely oxidized and consumed, and then the upper cover plate (1) falls down to form a sealing structure with the bowl body (5); the temperature is uniformly increased to the sintering high temperature zone, and the temperature is kept for a period of time, and the finished product is obtained after natural cooling; the temperature of the thermal decomposition zone is 340-360°C, the temperature of the debinding temperature zone is 595-605°C, the temperature of the graphite oxidation temperature zone is 1090-1110°C, and the temperature of the sintering high temperature zone is 1200-1400°C.

4. The method for using the PTC ceramic sintering sagger according to claim 3, characterized in that: In step S4, the heating rate of the debinding temperature zone is 3-5°C / min, and the temperature is kept for 115-125min.

5. The method for using the PTC ceramic sintering sagger according to claim 3, characterized in that: In step S4, the graphite oxidation temperature zone is heated at a rate of 3-5°C / min and kept warm for 40-50min.

6. The method for using the PTC ceramic sintering sagger according to claim 3, characterized in that: In step S4, the heating rate of the sintering high temperature zone is 8-10°C / min, and the temperature is kept for 10-120min.

7. The method for using the PTC ceramic sintering sagger according to claim 3, characterized in that: The stepwise heating process of step S4 is as follows: placing the PTC ceramic sintering sagger into a sintering furnace, uniformly heating the sintered sagger to 350±10°C at a speed of 3-5°C / min, and keeping the temperature for 32±5min; uniformly heating the sagger to 600±5°C at a speed of 3-5°C / min, and keeping the temperature for 120±5min; uniformly heating the sagger to 850±5°C at a speed of 3-5°C / min, and keeping the temperature for 45±5min; uniformly heating the sagger to 1100±5°C at a speed of 3-5°C / min, and keeping the temperature for 45±5min; uniformly heating the sagger to 1265-1270±2°C at a speed of 8-10°C / min, and keeping the temperature for 64±10min; uniformly cooling the sagger to 1240±5°C at a speed of 2-3°C / min, and keeping the temperature for 45±5min; uniformly cooling the sagger to 1140±5°C at a speed of 3-5°C / min, and keeping the temperature for 45±5min, and obtaining the finished product after natural cooling.

8. The method for using the PTC ceramic sintering sagger according to claim 3, characterized in that: The refractory material used in step S1 is mullite or alumina.

9. The method for using the PTC ceramic sintering sagger according to claim 3, characterized in that: In step S2, the thickness of the zirconium oxide plate is ≥6 mm.

10. The method for using the PTC ceramic sintering sagger according to claim 3, characterized in that: In step S3, 50-80 mesh zirconium powder and a zirconium oxide plate with a thickness of 2-3 mm are used.

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