Hermetically Sealed High Energy Tantalum Capacitor is high-performance, high-energy density, low impedance and full sealing. With the innovative multi-anode parallel structure, the self-impedance of the capacitor is significantly reduced, resulting in lower heat generation and higher reliability during high-power-density charging and discharging. Additionally, it can be used in circuits with some AC components for discharging and dual-purpose filtering as a filter and power compensation device.   To ensure high reliability during usage, please take note of the following points.   1. Test   1.1 Hermetically Sealed High Energy Tantalum Capacitor is a polar component, the polarity must not be reversed during use and testing. If the polarity is reversed, the reliability of the capacitor will be irreversibly damaged and cannot be used anymore.   1.2 Capacitance & Dissipation Factor Measuring Conditions: 1.0Vrms@100Hz   1.3 Equivalent Series Resistance（ESR）：measuredat1000Hz,1Vrms   1.4 Leakage current test: Apply rated voltage or class voltage for 5min. The qualified standards for leakage current can be found in the product specifications and corresponding specifications.   1.5 Professional testing instruments and fixtures must be used. A multimeter cannot be used to test any parameters of hermetically sealed high energy tantalum capacitor. It is not possible to use a multimeter to test it regardless of polarity.   1.6 Hermetically sealed high energy tantalum capacitor can store a high amount of electrical energy, after conducting a leakage current test, the capacitor must be thoroughly discharged by a standard leakage current tester before use. Discharge resistance: 1000 ohms; Discharge time: ≥ 5mins Residual voltage after discharge：＜1V   1.7 Test of electrical performance must be carried out in the following order and cannot violate. Test sequence: Capacitance & Dissipation Factor - ESR - Leakage Current – Discharge    2. Precautions for use on different circuits   2.1 Delay protection circuit The capacitors used in such circuits primarily serve as backup power for unexpected power outages, requiring them to automatically engage when the main power source suddenly fails. They must maintain a specified power supply duration under certain voltage and power density requirements. When designing circuits of this nature, please pay attention to the mathematical relationship between the total impedance of the capacitor's downstream circuit and the required voltage, capacitor capacity, and power needs. Additionally, during the design phase, it is advisable to leave at least a 50% margin in capacitor capacity selection to ensure that there is enough power supply time and power density in case of unforeseen factors. The specific calculation is as follows:   When the circuit is working normally, Input power: P Capacitance: C Voltage at both ends: U1 Then, the energy stored by the capacitor is  W1=C（U12）/2 Where U12 represents the square of U1. When the input power supply drops out, after a time t, the voltage at both ends U2, Then, the remaining energy of the capacitor is W2=C（U22）/2 The energy released during this process: W=W1-W2=C（U12-U22）/2 It should be equal to the energy required to keep the circuit working properly: W=Pt（i.e. input power multiplied by time） Therefore, C（U12-U22）/2=Pt From this, the minimum capacitance required for the circuit maintenance time t can be obtained as: C=2Pt/（U12-U22） In practical applications, U2 is the minimum input voltage that a circuit can operate normally.   Example: If when the circuit is working normally, the input voltage is 28V (U1), the input power is 30W (P), and the minimum input voltage that can work normally is 18V (U2). It is required that the circuit can still work even after a 50 millisecond (t) power drop-out from the input power supply, then the minimum capacitance required for energy storage capacitance is   C=2Pt/（U12-U22）  =2×30×50/（282-182）  =3000/（784-324）  =6.522mF=6522μF   An energy storage capacitor used in the front end of a power supply circuit has an input voltage of 50 V. When the power is cut off, the capacitor begins to supply energy to the subsequent circuit, and the voltage must be maintained at not less than 18 V while supplying energy for 75 W. Calculate the required capacitance. This circuit also requires an accurate loop resistance. The size of the circuit resistance determines the required capacity of the capacitor. The conversion formula for the performance of each parameter in this circuit is as follows: C=R×PT×T/(U1-U2)   In the equation:   C: Required capacitance (F) R: Total circuit resistance (Ω) Pt: The power that the circuit needs to maintain (W) T: Loop power holding time (s) U1: Input voltage (V) U2: Voltage that can maintain a certain power and discharge time (V) The capacitor used in such circuits must be derated to within 70% of the rated voltage.   2.2 Charging and discharging circuit Due to its high energy density and low impedance characteristics, this capacitor is the best choice for high-power discharge circuits. The hermetically sealed high energy tantalum capacitor used in such circuits can still achieve high power density infinite charging and discharging under certain conditions and still has high reliability. It is the best instantaneous power supply.   In such circuits, the relationship among the capacitance of capacitors, the output power density and load power can be calculated by referring to clause 2.1.   In this type of circuit, the maximum discharge current I to which the capacitor can be subjected individually must not exceed 50% of the current value calculated in the following formula; Due to the inherent thermal equilibrium issue that capacitors inevitably face during high-power discharges, the maximum DC current pulse that tantalum capacitors can safely withstand in a DC high-power discharge circuit with a fixed impedance is determined by the following formula:   I=UR /（R+ESR）   In the equation:   I: Maximum DC surge current (A) R: The total impedance of the circuit for testing or discharging (Ω) UR: Rated voltage (V) ESR: Equivalent series resistance (Ω)   From the above formula, it can be observed that if a product has a higher ESR (Equivalent Series Resistance), its safe DC surge current capability will be reduced. This also implies that if one product has half the ESR of another, its resistance to DC surge will be twice as high, and its filtering characteristics will be better as well. When using capacitors in such circuits, since the capacitors operate continuously at high power levels, the actual operating voltage should not exceed 70% of the rated voltage. Considering the impact of heat dissipation on reliability, it is even better to derate the usage to below 50% for higher reliability. Furthermore, when using this type of capacitor in such circuits, due to the high operating current, the capacitor will experience some heating. When designing the capacitor's placement, it is essential to ensure that it is not positioned too close to other heat-sensitive components. Additionally, the installation space for this capacitor must have good ventilation.   2.3 Filtering and power compensation for the power supply secondary  The allowable AC ripple value of the capacitor used in such circuits must be strictly controlled. Otherwise, excessive AC ripple can lead to significant heating of the capacitor and reduced reliability. In principle, the maximum allowable AC ripple value should not exceed 1% of the rated voltage, the current should not exceed 5% of the maximum permissible discharge current, and the maximum allowable operating voltage of the capacitor should not exceed 50% of the rated voltage.   3. Derating design of hermetically sealed high energy tantalum capacitor   In general, the reliability of capacitors is closely related to the operating conditions of the circuit. To ensure an adequate level of reliability during usage, it is essential to adhere to the following principles: 3.1 Reduce more rather than less Because the greater the derating of capacitors, the higher the reliability in handling unexpected power shocks. Additionally, derating design should be based on reliability under possible extreme usage conditions, such as high operating temperatures, high ripple currents, and significant temperature and power fluctuations.   3.2 Select large capacity rather than small The larger the capacitance, the higher the instantaneous electrical energy it can provide. Additionally, since this capacitor falls under the basic category of tantalum electrolytic capacitors, it experiences greater capacity loss at low temperatures (compared to solid tantalum capacitors). Therefore, the capacity selection should be based on the capacity at extreme negative temperatures. This is particularly important for capacitors used at high altitudes. Specific capacity variations at low temperatures can be found in the product specifications and relevant standards.   3.3 Selection of Impedance For circuits used in situation 2.3, it is essential to choose products with a lower ESR whenever possible for higher reliability and improved filtering performance.   3.4 Selection of Capacitor Size Due to the fact that smaller products with the same capacity and voltage must be manufactured using tantalum powder with higher specific capacity, the ESR of the product will be higher, and the leakage current will also be greater. Therefore, the reliability of the product will be lower than that of larger products. When installation space allows, products with larger volumes should be used as much as possible to achieve higher reliability.   4. Installation   4.1 Installation ways  The positive lead wire of hybrid energy tantalum capacitors cannot be directly welded to the circuit board, but must be welded to the circuit board through the external lead wire. High energy tantalum composite will be present. There are three ways to install the circuit board, as shown below: Figure 1：Installation mode of single negative pole lead (fixed by mounting frame)    Figure 2：Double negative or triple negative lead installation mode (fixed by negative lead)     Figure 3：Double screw or triple screw installation (fixed by screw)   4.2 Considerations for Installation Method Selection  Due to the relatively large mass and size of this capacitor, it is advisable to adhere to the following principles during installation: （a）For specifications with large size and mass, standard mounting brackets provided by the manufacturer should be used as much as possible to ensure that the connection between the product and circuit will not experience instantaneous open circuits when the equipment encounters large vibrations and overload impacts, and also to ensure installation strength requirements. (b) For conditions where size and mass are relatively small and there are stringent requirements for installation space, capacitor products with built-in mounting bolts can be used. For such installations, it is essential to ensure that the circuit board has a high level of strength. Additionally, after tightening the mounting bolts, epoxy-based sealant must be used to secure the bolts. If conditions allow, other forms of fastening (such as applying adhesive to the capacitor base) can also be employed to ensure that the capacitor's mounting strength meets the requirements for extreme conditions of use. (c) For products used in high-power continuous discharge circuits, capacitors should not be installed too close to devices with significant heat dissipation to prevent the capacitor from overheating and experiencing reduced reliability. Additionally, capacitors used in such circuits should not have heat-insulating sealant coatings applied to their casings to avoid a decrease in heat dissipation performance, which could lead to increased temperatures and reduced reliability of the capacitors. (d) For products used in high-power uninterrupted discharge circuits, it is essential to have good ventilation conditions to ensure that the heat generated by the capacitors can be promptly expelled, preventing excessive temperature rise of the capacitors. (e) The anode lead of hermetically sealed high energy tantalum capacitor is connected to the casing with an insulating ceramic material. Therefore, during installation, the positive lead that is fixed to the circuit board must be connected using nickel-based leads that are soldered on; it is not permissible to directly solder the excessively short tantalum leads onto the circuit board. This is because short positive leads can compromise the capacitor's seal when subjected to high overload and high-frequency vibrations, leading to leakage and capacitor failure.   5. Circuit protection   5.1 If the selected capacitor operates at a frequency with significant power variations, it is advisable to implement overload protection in the power supply circuit providing energy compensation to the capacitor. This helps prevent overloading of the power supply when there is a sudden surge in starting current. 5.2 The circuit in which this capacitor is used must have reverse voltage control and a separate discharge path to prevent the capacitor from experiencing reverse surges during operation and shutdown. The energy stored in the capacitor should be correctly discharged after use.    

Hidden defects-the occurrence and impact of cracks In the process of daily use or assembly and repair, the printed circuit board inside the equipment will inevitably be affected by various mechanical stresses, including bending stress. The bending of the printed circuit board causes the force to be transferred to the surface mounted multilayer ceramic capacitor through solder. These forces are concentrated at the bottom of the capacitor, but the ceramic material is hard, inelastic and fragile. When the bending force is large enough, the ceramic material on the bottom side of the capacitor will crack (see Figure 1).   Fig. 1 Schematic diagram of ceramic crack caused by typical bending   The crack generally starts from the bottom of the capacitor and extends in the ceramic at an angle of 45 degrees. It usually ends at the end electrode, or it may continue to extend to the top of the ceramic, and then ends. This crack may cause the whole end of the ceramic capacitor to separate from the main body. Once the crack occurs, the electrical parameters of the capacitor may not change significantly. In the next few hours, days, even weeks, it can still maintain the same capacitance, loss tangent or ESR (equivalent series resistance) as before, but the generation of cracks establishes a foundation for future electrical faults. The generation of cracks may cause water vapor and ions to continuously penetrate into the capacitor in the following time. A very "tight" crack may take more time to turn into an electrical fault. If the fault part is exposed to high current, local heating will be generated inside the crack, which will lead to the failure of the capacitor, and the whole circuit will eventually fail. In order to evaluate the bending capacity of ceramic capacitors, the bonding strength test of end coating is widely used in the reliability research of capacitors.   Test method for bonding strength of end plating The bonding strength test of end plating is also called substrate bending test. Before the test, the capacitor is installed in the center of a specific printed circuit board. Taking GB / T 2693-2001 as an example, the test sample is required to be installed on an epoxy screen glass printed board with a length of 100 mm and a thickness of 1.6 mm. The bonding strength test of end plating generally includes the following steps: 1) Place the PCB in the bending test device with the capacitor facing down, and test the capacitance C0 before the test when the PCB is in the horizontal state; 2) The bending tool can make the bending depth (d) reach 1 mm at the speed of 1 mm / s ± 0.5 mm / s to maintain the bending state of the circuit board for 20 s ± 1 s (see Fig. 2); 3) Test the capacitance C after the test under the bending state of printed circuit board, and monitor the electrical parameters of the whole bending state if necessary; 4) Reset the bending test device to restore the circuit board from the bending state and remove it from the test device; 5) Check the appearance of the test sample.   Fig. 2 bending test device   When the step-by-step bending method is used to find the limit of the bending capacity of the test sample, the bending tool can make the bending depth (d) reach 1 mm, 2 mm, 3 mm, 4 mm and 5 mm respectively at the speed of 1 mm / s ± 0.5 mm / s, and the bending state of the circuit board can be maintained for 20 s ± 1 s when the depth is reached, and then the capacitance is tested.   Mechanical model of bonding strength test of end plating The stress analysis of the test base plate shows that the base plate is mainly affected by the supporting force provided by the supports on both sides and the pressure P exerted by the bending tool. In the actual test, the width of the bending tool and support of the test device is greater than the width of the test base plate by 20 mm, and the base plate will not be affected by torque. Therefore, the model is regarded as a two-dimensional three-point bending model, as shown in Fig 3.   Fig.3. 3 points bending model of test substrate   The bending moment in the middle of the test base plate is M = PK, where K is the distance between the pressure P and the support of the test device. The maximum bending normal stress in the middle of the test substrate is   The stress position is the lower surface of the test substrate, which shows tensile stress, where W is the bending section coefficient. The cross section of the test substrate is rectangular, therefore:   Where B is the width of the test substrate and H is the thickness of the test substrate; In the end:   Bending shear stress of test substrate under pure bending state.   Experimental phenomena and result analysis Through the analysis of the test results of the bonding strength of the end coating, it is found that there are three main situations between the capacity change rate (c-c0) / C0 and the bending depth (d): as shown in Figure 4: 1. With the gradual increase of the bending depth (d), the capacity change rate does not change significantly. After reaching a certain depth, the capacity change rate drops sharply. When the test substrate is restored to the flat state again, the capacity change rate will decrease rapidly, Capacity is restored; 2. As the bending depth (d) increases, the capacitor fails. When the test substrate is restored to the flat state, the capacity does not recover; 3. With the increase of bending depth (d), the capacity change rate does not change significantly. Fig. 4 Relationship between depth of reduction and capacity of end plating bonding strength test   During the test, due to the cracks in the ceramic material of the capacitor, accompanied by the fracture of some electrodes, it may temporarily cause some loss of capacity, so the capacity change rate decreases. However, once the strain is eliminated, the electrodes can be "combined", and when the electrodes are connected again, the lost capacitance will be restored. In many cases, especially when the bending depth (D) is small, the cracks caused by the test cannot be evaluated by visual inspection or electrical performance testing. We regard these cracks as hidden defects. After the end coating bonding strength test, the climate sequence test can further evaluate whether the sealing of the test sample is damaged, and further evaluate the impact of these hidden defects on the reliability of MLCC.

Insects and birds sing, spring water sings and sounds, and the sound originates from the vibration of objects. It is a well-known thing that the human ear can recognize sound waves with a vibration frequency of 20Hz~20kHz. However, multi-layer Chip Ceramic Capacitors (MLCC) sometimes makes a acoustic noise. What is going on?   Multi layer ceramic capacitors (MLCC) are made of ceramic medium and metal inner electrode which are superposed in a staggered way. After one-time high-temperature sintering, the ceramic chip is formed, and then the outer electrode metal layer is sealed at both ends of the chip. The dielectric material system of this kind of ceramic capacitor is mainly divided into two types: I ceramic dielectric and II ceramic dielectric.   I ceramic dielectric belongs to paraelectric medium (the main materials are SrZrO3, MgTiO3, etc.), and I ceramic dielectric will not produce electrostrictive deformation. Therefore, MLCC made of I ceramic dielectric material, such as ceramic capacitor with CG characteristics, will not produce acoustic noise when working, but the dielectric constant of this kind of medium is very small, usually between 10 ~ 100, so it is unable to produce large capacitance capacitor.   Type Ⅱ media belong to ferroelectric media (the main material is BaTiO3, BaSrTiO3, etc.), and ferroelectric materials will produce electrostrictive deformation. MLCCs made of type II dielectrics, such as X7R, X5R, etc., usually have a dielectric constant between 2000 and 4000, and the capacitance of the capacitor is relatively large, and it is easy to produce obvious howling noise under the action of a specific AC signal.     Why does MLCC have acoustic noise In order to better understand the nature of capacitor acoustic noise, let's first understand a natural phenomenon-the piezoelectric effect. In 1880, brothers Pierre Curie and Jacques Curie discovered that tourmaline has piezoelectric effect. In 1984, the German physicist Wodemar Voith deduced that only crystals with 20 point groups without a symmetry center could have the piezoelectric effect. The piezoelectric effect is due to the special arrangement of atoms in the crystal lattice of the piezoelectric material, which makes the material have the effect of coupling the stress field and the electric field. The academic definition of the piezoelectric effect is: when certain dielectrics are deformed by external forces in a certain direction, polarization will occur inside them, and at the same time, positive and negative charges will appear on its two opposite surfaces. When the external force is removed, it will return to an uncharged state. This phenomenon is called the positive piezoelectric effect. When the direction of the force changes, the polarity of the charge also changes. On the contrary, when an electric field is applied to the polarization direction of the dielectric, these dielectrics will also deform. After the electric field is removed, the deformation of the dielectric disappears. This phenomenon is called the inverse piezoelectric effect, or electrostriction. These two positive and inverse piezoelectric effects are collectively referred to as piezoelectric effects. The piezoelectric effect is a phenomenon in which mechanical energy and electrical energy are exchanged in dielectric materials. Obviously, the MLCC capacitor acoustic noise we are discussing belongs to the category of inverse piezoelectric effect. More generally speaking, under the action of an external electric field, the ferroelectric ceramic medium with piezoelectric effect will undergo expansion and contraction. This kind of expansion and contraction is called electrostriction. The electrostrictive properties of different ceramic media are also different. For other types of capacitors, because the dielectric material does not have a piezoelectric effect, or the piezoelectric effect is minimal, the howling on the circuit is basically due to the vibration generated by the inverse piezoelectric effect of the ferroelectric ceramic medium MLCC. （Picture source network） As shown in the figure above, the ferroelectric ceramic medium's ferroelectricity will produce piezoelectric effect noise. The general Poisson’s ratio (transverse deformation coefficient) of MLCC dielectrics is about 0.3. After an AC signal is applied, multilayer ceramic capacitors will stretch and deform in the direction parallel to the stacking direction and the circuit board, and the resulting amplitude is usually pm to nm level. When it is not soldered to the circuit board, the acoustic impedance of a single capacitor is different from that of the air, but if this is the case, it should be almost inaudible. When the ceramic capacitor is soldered on the circuit board, the capacitor and the circuit board are rigidly connected, and the deformation of the capacitor will pull the circuit board. The circuit board becomes an acoustic impedance transformer. When the vibration frequency reaches the distinguishable frequency band (20Hz~20kHz) of the human ear, then, you will hear acoustic noise .     On what occasions does MLCC have acoustic noise In common audio circuits, especially audiophiles, people usually like to use ruby, black diamond and other electrolytic capacitors. Because the working frequency of the audio circuit is usually relatively low, such as several kHz or tens of kHz, and the ferroelectric ceramic capacitor may produce a whistling sound that can be heard by the human ear at this working frequency. This effect will be lost at frequencies much higher than 30kHz, because the capacitor itself cannot respond quickly to change the pressure level. Therefore, the peak response range and noise characteristics determine that these capacitors should be used with caution in audio circuits and high gain circuits. Under the action of specific AC signals, MLCCs using ferroelectric ceramic dielectrics (such as X7R/X5R) may produce howling. The violent howling comes from violent vibration, and the amplitude of the vibration is determined by the degree of the piezoelectric effect, which is proportional to the intensity of the electric field. When the applied voltage is constant, the thinner the medium, the stronger the piezoelectric effect and the louder the howling sound.   What is the impact of MLCC acoustic noise Due to the existence of capacitive howling, when mobile electronic devices are close to human ears, the audible noise generated by electronic products (laptops, tablets, smart phones, etc.) will affect the user's feelings, and violent howling will make people feel irritable . Under an alternating electric field, the ferroelectric domains of ferroelectric ceramic capacitors will alternately turn as the direction of the electric field changes, causing friction within the ferroelectric domains and increasing the probability of failure of the capacitor. In addition, the appearance of capacitor whistling also indicates that the voltage ripple on the capacitor is too large. Severe voltage ripple will affect the normal operation of the circuit and cause the circuit to work abnormally.   How to solve MLCC acoustic noise There are many ways to solve the howling noise generated by MLCC capacitors, and the solution may increase the cost. 1. Changing the type of capacitor dielectric material is the most direct method. Use Class I ceramic capacitors, film capacitors, tantalum electrolytic capacitors, aluminum electrolytic capacitors and other capacitors that do not have piezoelectric effect instead. However, issues such as volumetric space, reliability, and cost need to be considered. 2. Adjust the circuit to eliminate the alternating voltage applied to the MLCC as much as possible. 3. Adjust the specifications and layout of the PCB circuit board to reduce vibration and help reduce the level of howling. 4. Adjust the size of MLCC. 5. Use MLCC with no noise or low noise.   Based on this, for the MLCC product itself, we can adopt the following solution strategies (1) Thicken the protective layer. Since the thickness of the protective layer has no internal electrodes, this part of the BaTiO3 ceramic will not be deformed. When the solder height at both ends does not exceed the thickness of the bottom protective layer, the deformation generated at this time will have less impact on the PCB, which can effectively reduce noise. (2) Additional metal support structure. The structure diagram of the bracket capacitor is as follows. It uses a metal bracket to isolate the MLCC chip from the PCB board. The inverse piezoelectric effect produces deformation and elastically buffers the metal bracket to reduce the effect on the PCB board, thereby effectively reducing noise. (3) Adopt lead product structure. The principle is similar to that of the metal bracket. (4) Design and manufacture using dielectric materials with weak piezoelectric effect. By further doping barium titanate (BaTiO3) to sacrifice a certain dielectric constant and temperature characteristics, a dielectric material with greatly reduced piezoelectric effect is obtained, and the MLCC made with it can effectively reduce noise. (5) Substrate embedded design. A new structure with capacitors mounted on the interposer circuit board is adopted to suppress howling.   Conclusion Based on the acoustic noise phenomenon of MLCC capacitors, combined with the structure of the chip ceramic dielectric capacitor and the characteristics of the ceramic dielectric material, we analyzed the howling mechanism of ferroelectric ceramic dielectric capacitors, and finally enumerated the solutions and strategies to solve the howling phenomenon. . In different application scenarios, engineers in the electronics field need to weigh the cost and actual effects and choose the best solution to develop better products.