February 18, 2017

AVX tantalum capacitor anode technology

AVX Distributor Data: AVX tantalum capacitor Anode selection
         Switching power supply, a common trend of microprocessor and digital circuit is used to reduce the noise of high frequency at work. In order to do this, the components must have low ESR (resistivity), high capacitance and high reliability.
        AVX tantalum capacitor An anode for the overall surface area, especially the surface area and volume ratio, is one of the key parameters to determine the ESR value, the surface area is large, the larger the value of ESR. The use of multi anode is greatly reduced one way AVX tantalum capacitor ESR value, its practice is to use the same electrode material in a capacitor body.
The traditional approach
       In the application of long-life and high reliability, the conventional MnO2 electrode plate AVX tantalum capacitor Which is still a popular choice. The manganese dioxide technology can provide excellent field performance and stability in environment and in a wide range of voltages such as 2.5 ~ 50V with high resistivity and thermal resistance rate, device design operating temperature at 125 DEG C. However, compared with the AVX polymer tantalum capacitors, high manganese dioxide electrode system ESR is a disadvantage.

 AVX tantalum capacitor anode technology

Anode selection
        Single anode technology has become the universal standards of choice is due to its excellent price. Multi anode design provides a lower ESR value, but its drawback is that production cost is higher than that of single anode solution.
       The design of slot type anode chip integrated process using standard is a result of low ESR and low cost tradeoff. Therefore, groove design is usually used for price sensitive and low ESR design, multi anode technology suitable for both low ESR requires high reliability applications, such as telecommunications infrastructure, network, servers and military / aerospace applications.
In addition to these differences, the concept of multi anode has another two.
(1) has better heat dissipation performance multi anode design, which means that multi anode capacitance can be sustained higher current carrying capacity; similarly, multi anode capacitance against the current surge hazard is also stronger.
(2) compared to the single anode unit volume, multi anode capacitor with low efficiency, which leads to a hypothesis that cannot be achieved with a single multi anode anode as CV (constant voltage factor. In fact, the thin anode to achieve more easily, and more easily penetrate second manganese dioxide electrode system, the higher CV can be used, therefore, multi anode capacitor can achieve the same or even higher levels of CV.
Common anode type
        On the market today commonly used multi anode tantalum usually adopts the vertical arrangement for 3 ~ 5 anode in a capacitor body, as shown in figure 1. This is actually from a manufacturing point of view, if from the perspective of ESR, this solution is not as good as the horizontal layout, anode plate thinner in a horizontal layout further reduced ESR.

 AVX tantalum capacitor anode technology

Figure 1 Multi anode device using anode two or more than two in a capacitor body

        Multi anode device new multi anode design cost with the number increasing exponentially anode. At present, most use in the design of the optimal design of triple anode has been close to the cost and ratio of ESR.
        The longitudinal structure design, an anode electrode through silver epoxy resin glue is connected to the second, and then to the other electrode lead frame. A single anode capacitance the same approach is used in the standard, so the manufacturing technology and the old similar, without new technology links added many additional investment anode design.
        On the other hand, , horizontal design need new solutions for connection between the anode, which directly leads to the modification of costly technology. Therefore, so far, this design has not been used for single batch multi anode capacitor life production. The horizontal design is more often used in some special applications, is through welding or jigging system, two or more than two complete capacitor is added to the array or module.
       The differences between the performance of ESR horizontal and vertical structure as shown in figure 2. This example is the calculation of the D type capacitor based on the theory of Figure 2 shows that the two horizontal structure and vertical structure of anode triple anode system ESR value is similar. However, the relative price advantage in the ESR horizontal structure is more obvious.

 AVX tantalum capacitor anode technology

Figure 2 the horizontal and vertical structure performance similar to that of capital becomes the decisive factor

       Compared to the horizontal structure, vertical design more restricted in reduced height, the capacitor current height in 3.5 ~ 4.5mm. Today, this factor is more important, even in such as telecommunications infrastructure, military application, the miniaturization of electronic products has become a test in the past, this is not some.
      The two anode transverse "mirror" structure, researchers have developed a new type of multi anode structure. Lead mirror structure using improved frame shape, the lead frame is positioned on the two anode. The structure solves the problems connected with horizontal arrangement of electrodes, and the process of modification cost decreased to an acceptable level.
      The effect of the two anode performance of ESR mirror design is slightly inferior to the three pole longitudinal structure, but it is cheaper to manufacture. The main advantage lies in the design of the mirror, it makes the multi anode capacitor height decreases, the minimum fell to 3.1mm.
      The use of other advantages of mirror design, its symmetrical layout helps to reduce the inductance (ESL). The symmetry of the structure as part of compensation of the inductance loop, to reduce the ESL to use the classic lead frame design under.
      A D type single anode design of the ESL value is 2.4nH, the typical value is about 2.1nH. The mirror design ESL value about 1nH is half the conventional design. This will mirror multi anode to resonance frequency higher value, as shown in figure 3.

 AVX tantalum capacitor anode technology

Figure 3 performance mirror design
(a) shows its capacitance frequency decrease below the single anode solution (b), and the ESR value is so

       If the use of mirror structure anode thinner, the capacitor will drop to lower frequency. The resonance frequency of mirror design changes, the reason is that the current general DC/DC converter the switching frequency range (250 ~ 500kH) due to reduced ESL increased significantly.
      Another advantage is to improve the image design of the thermal performance as shown in Figure 4, resulting in the anode current ripple heat can be cooled by lead divergence on the PCB plate and tantalum wire.

 AVX tantalum capacitor anode technology

      Therefore, although the single anode class D capacitors can continuously heat only 150mW, but the mirror structure of similar size can handle 255mW capacitor. Capacitance type horizontal mirror multi anode capacitor current can reach the value of 220 to 1000 mu F, voltage is 2.5 ~ 10V, the ESR value is 25 ~ 35m. The future development will be further extended to the voltage range of 35 and 50V, which will make the capacitor very attractive new application in Telecom design increasingly heavy to the height. A single 35 ~ 50V capacitance in the maximum height in the 3.1mm with 10 ~ 22 F capacitance, 65 ~ 140m. The ESR value, this is any other technology are difficult to match.

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