Sintering method for improving tantalum core size consistency

Abstract

The invention discloses a sintering method for improving the size consistency of a tantalum core. The sintering method comprises a process of placing an anode tantalum core of a tantalum capacitor in a crucible for vacuum sintering. The shape of the crucible is optimized, the crucible with the through holes in the periphery is adopted to replace a solid crucible, heat radiation is increased through the punching design, the tantalum core is optimized from an original single heat conduction heating mode to a heat radiation heating mode and a heat conduction heating mode, and it is guaranteed that the tantalum core is heated more evenly. And secondly, the crucible is loaded in a mode that the tantalum cores are directly contacted and stacked, and the traditional tantalum core crucible loading mode that the tantalum pressing plate and the tantalum cores are stacked in a staggered manner is omitted, so that the influence of the weight of the tantalum pressing plate on the deformation of the tantalum cores is reduced.

Description

Technical Field

[0001] The invention belongs to the technical field of capacitor preparation, and in particular relates to a sintering method for improving the dimensional consistency of a tantalum core. Background Art

[0002] During capacitor fabrication, the tantalum cores need to be sintered. A temperature gradient exists within the vacuum sintering furnace, caused by the positional differences resulting from the heaters' varying heights. Consequently, the actual temperatures vary between crucibles and between different layers of tantalum core within the crucible. The greater the height differences between the tantalum cores, the greater the actual temperature differences between the cores. Consequently, after sintering, the actual shrinkage of the tantalum cores varies, a factor that directly impacts their electrical performance and assembly fit. This is particularly true between crucibles. Due to the height gradient, the actual temperature difference between two adjacent crucibles can be approximately 20°C, significantly impacting the consistency of the tantalum core shrinkage. Adjacent crucibles with these temperature differences are referred to as high-temperature and low-temperature crucibles.

[0003] Patent application document with announcement number CN110000379A discloses a process for manufacturing tantalum cores for high-temperature all-tantalum capacitors. The process specifically includes the following steps: (1) selecting a tantalum core forming mold, wherein the lower punch of the forming mold adopts a punch mold with a convex chamfered circumferential edge; (2) using alcohol to demould and cold isostatic pressing to form a tantalum core blank; (3) forming a hook from the upper end of the tantalum wire of the tantalum core blank and hanging it on a tantalum wire mesh, then placing the tantalum core blank in a tantalum cylinder and performing hanging sintering using vacuum indirect heating to produce a tantalum core for a high-temperature all-tantalum capacitor. Although the document discloses a staged heating method, it solves the technical problem of improving the deformation of the bottom of the tantalum core after vacuum sintering, thereby increasing the dimensional consistency of the tantalum core after sintering. The measures taken are to chamfer the tantalum core during the forming process and to replace the traditional standing sintering with hanging sintering. Summary of the Invention

[0004] In order to solve the above technical problems, the present invention provides a sintering method for improving the dimensional consistency of tantalum cores.

[0005] The present invention is achieved through the following technical solutions.

[0006] The present invention provides a sintering method for improving the size consistency of a tantalum core, comprising placing a tantalum core of a tantalum capacitor anode in a crucible and performing vacuum sintering in a multi-stage temperature-raising manner.

[0007] Preferably, the vacuum sintering temperature is 400-1445°C and the vacuum degree is 2×10 -2 pa-3×10 -2 pa.

[0008] Preferably, the multi-stage temperature increase is to increase the temperature to 400-600°C as the first stage, then to 900-1100°C as the second stage, and finally to 1400-1445°C as the third stage.

[0009] Preferably, the heating time of the first stage and the second stage is 35-60 minutes, and the heating time of the third stage is 20-40 minutes.

[0010] Preferably, in the multi-stage heating, the temperature is raised to 400-600°C and then kept constant at that temperature for 8-14 minutes, the temperature is raised to 900-1100°C and then kept constant at that temperature for 8-14 minutes, and the temperature is raised to 1400-1445°C and then kept constant at that temperature for 20-30 minutes.

[0011] Preferably, a pressure plate is provided in the crucible, and the tantalum anode core of the tantalum capacitor is provided on the pressure plate.

[0012] Preferably, the tantalum capacitor anode tantalum cores are stacked and arranged on a pressure plate, adjacent tantalum capacitor anode tantalum cores are not separated by a pressure plate, and a pressure plate is provided on the stacked tantalum capacitor anode tantalum cores.

[0013] Preferably, the pressing plate is made of tantalum.

[0014] Preferably, a plurality of through holes are respectively provided on the side wall and the bottom surface of the crucible.

[0015] Preferably, the through holes on the bottom surface of the crucible are arranged in a linear distribution.

[0016] The beneficial effects of the present invention are:

[0017] The present invention optimizes the shape of the crucible, replaces the solid crucible with a crucible with holes punched all around, and increases heat radiation through the punching design. The original single heat conduction heating of the tantalum core is optimized to two heating methods, heat radiation and heat conduction, to ensure that the tantalum core is heated more evenly. Secondly, the present application adopts a method of stacking tantalum cores in direct contact with each other to load the crucible. By eliminating the traditional method of stacking tantalum cores in a crucible with staggered tantalum pressure plates and tantalum cores, the effect of the weight of the tantalum pressure plate on the deformation of the tantalum core is reduced. In the sintering method of the present application, multiple crucibles of the same height can be stacked up and down for sintering. Each crucible has 4 layers, and 32 tantalum cores are placed in each crucible, which has good processing efficiency. The method of the present application can improve the deformation of the tantalum core after sintering, thereby increasing the consistency of the tantalum core. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 This is a schematic structural diagram of the connection between the tantalum core of the tantalum capacitor anode and the pressure plate of the present invention;

[0019] Figure 2 is a front view of the crucible of the present invention;

[0020] Figure 3 1 is a temperature rise curve diagram of Example 3 of the present invention;

[0021] Figure 4 Schematic diagram of the structure of the bottom surface of the crucible of the present invention;

[0022] Figure 5 It is a heating curve diagram of Comparative Example 1;

[0023] Figure 6 2 is a schematic diagram of the structure of the connection between the tantalum core of the tantalum capacitor anode and the pressure plate;

[0024] In the figure: 1- tantalum capacitor anode tantalum core, 2- crucible, 3- pressing plate, 4- through hole. DETAILED DESCRIPTION

[0025] The technical solution of the present invention is further described below, but the scope of protection claimed is not limited to the description.

[0026] Example 1:

[0027] like Figures 1 to 3 As shown, a sintering method for improving the size consistency of a tantalum core includes placing a tantalum capacitor anode tantalum core 1 in a crucible 2 and performing vacuum sintering.

[0028] Vacuum sintering adopts a multi-stage heating method, and the vacuum degree is 2×10 -2 The multi-stage temperature increase is to increase the temperature to 400°C as the first stage, then to 900°C as the second stage, and finally to 1400°C as the third stage.

[0029] In the first stage, the temperature rises from room temperature to 400°C in 35 minutes, the second stage from 400°C to 900°C in 35 minutes, and the third stage from 900°C to 1400°C in 20 minutes.

[0030] In the multi-stage temperature increase, the temperature was raised to 400° C. and then kept constant at that temperature for 8 minutes, the temperature was raised to 900° C. and then kept constant at that temperature for 8 minutes, and the temperature was raised to 1400° C. and then kept constant at that temperature for 20 minutes.

[0031] A pressing plate 3 is provided in the crucible 2 , and the tantalum capacitor anode tantalum core 1 is provided on the pressing plate 3 .

[0032] The tantalum capacitor anode tantalum cores 1 are stacked and arranged on a pressure plate 3 , and adjacent tantalum capacitor anode tantalum cores 1 are not separated by a pressure plate 3 , and a pressure plate 3 is arranged on the stacked tantalum capacitor anode tantalum cores 1 .

[0033] The pressing plate 3 is made of tantalum.

[0034] A plurality of through holes 4 are respectively provided on the side wall and bottom surface of the crucible 2 .

[0035] The through holes 4 on the bottom surface of the crucible 2 are arranged in a linear distribution.

[0036] Example 2:

[0037] like Figures 1 to 3 As shown, a sintering method for improving the size consistency of a tantalum core includes placing a tantalum capacitor anode tantalum core 1 in a crucible 2 and performing vacuum sintering.

[0038] Vacuum sintering adopts a multi-stage heating method, and the vacuum degree is 3×10 -2 The multi-stage temperature increase is to increase the temperature to 600°C as the first stage, then to 1100°C as the second stage, and finally to 1420°C as the third stage.

[0039] In the first stage, the temperature rises from room temperature to 600°C in 60 minutes, in the second stage, the temperature rises from 600°C to 1100°C in 60 minutes, and in the third stage, the temperature rises from 1100°C to 1420°C in 40 minutes.

[0040] In the multi-stage temperature increase, the temperature was raised to 600° C. and then kept constant at that temperature for 14 minutes, the temperature was raised to 1100° C. and then kept constant at that temperature for 14 minutes, and the temperature was raised to 1420° C. and then kept constant at that temperature for 30 minutes.

[0041] A pressing plate 3 is provided in the crucible 2 , and the tantalum capacitor anode tantalum core 1 is provided on the pressing plate 3 .

[0042] The tantalum capacitor anode tantalum cores 1 are stacked and arranged on a pressure plate 3 , and adjacent tantalum capacitor anode tantalum cores 1 are not separated by a pressure plate 3 , and a pressure plate 3 is arranged on the stacked tantalum capacitor anode tantalum cores 1 .

[0043] The pressing plate 3 is made of tantalum.

[0044] A plurality of through holes 4 are respectively provided on the side wall and bottom surface of the crucible 2 .

[0045] The through holes 4 on the bottom surface of the crucible 2 are arranged in a linear distribution.

[0046] Example 3:

[0047] like Figures 1 to 3 As shown, a sintering method for improving the size consistency of a tantalum core includes placing a tantalum capacitor anode tantalum core 1 in a crucible 2 and performing vacuum sintering.

[0048] Vacuum sintering adopts a multi-stage heating method, and the vacuum degree is 2.67×10 -2The multi-stage temperature increase is to increase the temperature to 500°C as the first stage, then to 1000°C as the second stage, and finally to 1445°C as the third stage.

[0049] In the first stage, the temperature rises from room temperature to 500°C in 50 minutes, the second stage from 500°C to 1000°C in 50 minutes, and the third stage from 1000°C to 1445°C in 30 minutes.

[0050] In the multi-stage temperature increase, the temperature was raised to 500° C. and then kept constant at that temperature for 10 minutes, the temperature was raised to 1000° C. and then kept constant at that temperature for 10 minutes, and the temperature was raised to 1445° C. and then kept constant at that temperature for 25 minutes.

[0051] A pressing plate 3 is provided in the crucible 2 , and the tantalum capacitor anode tantalum core 1 is provided on the pressing plate 3 .

[0052] The tantalum capacitor anode tantalum cores 1 are stacked and arranged on a pressure plate 3 , and adjacent tantalum capacitor anode tantalum cores 1 are not separated by a pressure plate 3 , and a pressure plate 3 is arranged on the stacked tantalum capacitor anode tantalum cores 1 .

[0053] The pressing plate 3 is made of tantalum.

[0054] A plurality of through holes 4 are respectively provided on the side wall and bottom surface of the crucible 2 .

[0055] The through holes 4 on the bottom surface of the crucible 2 are arranged in a linear distribution.

[0056] Comparative Example 1:

[0057] like Figure 5 As shown, a tantalum core sintering method includes placing a tantalum capacitor anode tantalum core 1 in a crucible 2 and performing vacuum sintering.

[0058] Vacuum sintering adopts a multi-stage heating method, and the vacuum degree is 2.67×10 -2 The multi-stage temperature increase is to increase the temperature to 500°C as the first stage, then to 1000°C as the second stage, and finally to 1460°C as the third stage.

[0059] In the first stage, the temperature rises from room temperature to 500°C in 40 minutes, the second stage from 500°C to 1000°C in 30 minutes, and the third stage from 1000°C to 1460°C in 20 minutes.

[0060] In the multi-stage temperature increase, the temperature was raised to 500° C. and then kept constant at that temperature for 10 minutes, the temperature was raised to 1000° C. and then kept constant at that temperature for 10 minutes, and the temperature was raised to 1460° C. and then kept constant at that temperature for 25 minutes.

[0061] A pressing plate 3 is provided in the crucible 2 , and the tantalum capacitor anode tantalum core 1 is provided on the pressing plate 3 .

[0062] The tantalum capacitor anode tantalum cores 1 are stacked and arranged on a pressure plate 3 , and adjacent tantalum capacitor anode tantalum cores 1 are not separated by a pressure plate 3 , and a pressure plate 3 is arranged on the stacked tantalum capacitor anode tantalum cores 1 .

[0063] The pressing plate 3 is made of tantalum.

[0064] A plurality of through holes 4 are respectively provided on the side wall and bottom surface of the crucible 2 .

[0065] The through holes 4 on the bottom surface of the crucible 2 are arranged in a linear distribution.

[0066] Comparative Example 2:

[0067] like Figure 6 As shown, a tantalum core sintering method includes placing a tantalum capacitor anode tantalum core 1 in a crucible 2 and performing vacuum sintering.

[0068] Vacuum sintering adopts a multi-stage heating method, and the vacuum degree is 2.67×10 -2 The multi-stage temperature increase is to increase the temperature to 500°C as the first stage, then to 1000°C as the second stage, and finally to 1445°C as the third stage.

[0069] In the first stage, the temperature rises from room temperature to 500°C in 50 minutes, the second stage from 500°C to 1000°C in 50 minutes, and the third stage from 1000°C to 1445°C in 30 minutes.

[0070] In the multi-stage temperature increase, the temperature was raised to 500° C. and then kept constant at that temperature for 10 minutes, the temperature was raised to 1000° C. and then kept constant at that temperature for 10 minutes, and the temperature was raised to 1445° C. and then kept constant at that temperature for 25 minutes.

[0071] A pressing plate 3 is provided in the crucible 2 , and the tantalum capacitor anode tantalum core 1 is provided on the pressing plate 3 .

[0072] The tantalum capacitor anode tantalum core 1 and the pressure plate 3 are arranged crosswise and stacked, and the pressure plate 3 is arranged on the top tantalum capacitor anode tantalum core 1.

[0073] The pressing plate 3 is made of tantalum.

[0074] The crucible 2 has no through hole 4 .

[0075] Ten pressed disc-shaped CASD5 type 100V1900μF (Ф34×4, designed specific capacitance of 17000μF·V / g) tantalum capacitor anode tantalum cores were sintered using the methods of Examples 1 to 3 and Comparative Examples 1 and 2. The shrinkage rate and specific capacitance of the tantalum cores were then tested, and the average values of the results are shown in the following table.

[0076]

[0077]

[0078] As can be seen from the table above, this application reduces the heating rate in the three heating stages. The faster the temperature change to which the tantalum core is subjected, the greater the degree of shrinkage of the tantalum core. Therefore, by reducing the heating rate, the tantalum core is heated more evenly. The maximum difference in volume shrinkage of the tantalum core between different crucibles is reduced to 0.4%, and the specific volume difference is reduced to 100. The maximum difference in volume shrinkage of the tantalum core between different layers in the same crucible is reduced to 0.2%, and the specific volume difference is reduced to 40. As a result, the volume shrinkage and electrical performance parameters of the tantalum core are greatly improved.

[0079] Finally, this application limits the calcination to 1445°C, and at the same time extends the constant temperature time after the third stage of heating by 5 minutes. Lowering the temperature of the high-temperature holding stage can effectively reduce the diffusion and flow process between the tantalum powder particles in the high-temperature crucible, thereby reducing the number of closed pores and the shrinkage rate of the tantalum core size. At the same time, increasing the constant temperature time of the high-temperature holding stage increases the further diffusion and flow between the tantalum powder particles in the low-temperature crucible, thereby increasing the shrinkage rate of the tantalum core. In Comparative Examples 1 and 2, the difference in shrinkage rate of the tantalum core in the high-temperature crucible is as high as 3.5, and the difference in shrinkage rate of the tantalum core in the low-temperature crucible is as high as 4.3, indicating that when the maximum sintering temperature is greater than 1445°C or the tantalum core and the pressure plate are stacked crosswise, the sintering effect of the tantalum core will be greatly affected.

Claims

1. A sintering method for improving the dimensional consistency of tantalum cores, characterized by: The method comprises placing a tantalum capacitor anode tantalum core (1) in a crucible (2) and performing vacuum sintering in a multi-stage temperature raising manner.

2. A sintering method for improving the dimensional consistency of a tantalum core according to claim 1, characterized in that: The vacuum sintering temperature is 400-1445°C and the vacuum degree is 2×10 -2 pa-3×10 -2 pa.

3. A sintering method for improving the dimensional consistency of a tantalum core according to claim 2, characterized in that: The multi-stage temperature increase is to increase the temperature to 400-600° C. as the first stage, then to 900-1100° C. as the second stage, and finally to 1400-1445° C. as the third stage.

4. A sintering method for improving the dimensional consistency of a tantalum core according to claim 3, characterized in that: The heating time of the first stage and the second stage is 35-60 minutes, and the heating time of the third stage is 20-40 minutes.

5. The sintering method for improving the dimensional consistency of tantalum cores according to claim 3, characterized in that: In the multi-stage heating, the temperature is raised to 400-600° C. and then kept constant at that temperature for 8-14 minutes; the temperature is raised to 900-1100° C. and then kept constant at that temperature for 8-14 minutes; the temperature is raised to 1400-1445° C. and then kept constant at that temperature for 20-30 minutes.

6. The sintering method for improving the dimensional consistency of tantalum cores according to claim 1, characterized in that: A pressing plate (3) is arranged in the crucible (2), and the tantalum capacitor anode tantalum core (1) is arranged on the pressing plate (3).

7. A sintering method for improving the dimensional consistency of a tantalum core according to claim 6, characterized in that: The tantalum capacitor anode tantalum cores (1) are stacked and arranged on a pressure plate (3); adjacent tantalum capacitor anode tantalum cores (1) are not separated by a pressure plate (3); and a pressure plate (3) is arranged on the stacked tantalum capacitor anode tantalum cores (1).

8. The sintering method for improving the dimensional consistency of tantalum cores according to claim 6, characterized in that: The pressing plate (3) is made of tantalum.

9. The sintering method for improving the dimensional consistency of a tantalum core according to claim 1, wherein: A plurality of through holes (4) are respectively provided on the side wall and the bottom surface of the crucible (2).

10. The sintering method for improving the dimensional consistency of tantalum cores according to claim 9, characterized in that: The through holes (4) on the bottom surface of the crucible (2) are arranged in a linear distribution.

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