T491X337K010AG

Product Overview of the KEMET T491 Series

The KEMET T491 represents a modern approach to solid tantalum capacitor technology, specifically engineered for automated surface mount manufacturing processes. Built on decades of proven tantalum technology, the T491 combines established reliability with contemporary materials and manufacturing techniques to deliver consistent performance across a broad range of industrial applications.

The T491 series meets or exceeds the requirements of EIA standard 535BAAC, establishing a baseline for electrical performance and reliability. These capacitors are classified as moisture sensitivity level (MSL) 1 under J-STD-020, meaning they have unlimited floor life and do not require special moisture control measures during storage or handling prior to assembly.

Typical applications for the KEMET T491 series include decoupling and filtering functions in DC/DC converters, portable electronics, telecommunications equipment, and industrial control units. The combination of high capacitance density, low profile form factors, and proven reliability makes the T491 suitable for designs where space constraints and performance demands intersect.

Design Architecture and Construction of the KEMET T491 Series

The KEMET T491 employs a molded epoxy construction that encapsulates the solid tantalum core, providing mechanical protection and environmental isolation. The molded design enables the compact form factors that characterize the series while maintaining structural integrity through the rigors of automated assembly processes.

The capacitor body features laser marking for permanent identification, allowing traceability throughout the product lifecycle. The marking includes the capacitance value, voltage rating, and manufacturing date code, enabling rapid verification during assembly and troubleshooting.

The internal construction utilizes manganese dioxide (MnO₂) as the cathode material, a proven technology that delivers stable performance across the operating temperature range. This construction approach provides predictable electrical characteristics and long-term reliability in field applications.

Electrical Specifications and Performance Characteristics of the KEMET T491 Series

The KEMET T491 series delivers consistent electrical performance across its operating range through careful design and rigorous testing. Each device undergoes 100% surge current testing for select case sizes (C, D, E, U, V, and X), ensuring that components can withstand transient current events without degradation.

The electrical characteristics of the T491 are influenced by frequency, temperature, and applied voltage. Equivalent series resistance (ESR) decreases with increasing frequency, while capacitance exhibits a slight decrease at higher frequencies. These frequency-dependent behaviors are documented in the device's performance curves and must be considered when selecting components for AC ripple applications.

The T491 series demonstrates stable performance across its rated operating temperature range of -55°C to +125°C. Temperature compensation multipliers apply to maximum power dissipation ratings, requiring designers to derate the device when operating at elevated temperatures. This temperature-dependent behavior is predictable and can be incorporated into thermal design calculations.

Capacitance Range, Voltage Ratings, and Tolerance Options in the KEMET T491 Series

The KEMET T491 series offers capacitance values ranging from 0.1 microfarads to 1,000 microfarads, providing flexibility for diverse circuit requirements. Voltage ratings span from 2.5 VDC to 50 VDC, allowing designers to select the appropriate voltage rating for their specific application without over-specifying the component.

Two tolerance options are available: ±10% and ±20%. The ±10% tolerance option, designated by the letter "K" in the part number, provides tighter capacitance control for applications where circuit performance is sensitive to capacitance variation. The ±20% tolerance option, designated by the letter "M", offers cost optimization for applications with broader tolerance requirements.

Extended range values within each case size provide designers with granular selection options. This approach minimizes the need for parallel capacitor configurations and simplifies PCB layout by reducing the number of discrete components required to achieve target capacitance values.

Termination Finishes and Their Applications in the KEMET T491 Series

The KEMET T491 series offers multiple termination finish options to accommodate different assembly processes and environmental requirements. The standard termination consists of 100% matte tin (Sn) plating, which provides excellent wetting characteristics and compatibility with modern lead-free solder systems. This finish is designated by the letter "T" in the part number.

Gold-plated terminations, designated by the letter "G", are available for applications utilizing conductive epoxy attachment processes. Gold plating provides superior corrosion resistance and is preferred in high-reliability applications where long-term contact reliability is paramount.

Non-magnetic 100% tin terminations, designated by the letter "N", address applications where magnetic properties of the component must be minimized. Standard solder-coated terminations with tin-lead composition (SnPb), designated by the letter "H", remain available for legacy applications or specific customer requirements.

The choice of termination finish influences both the assembly process compatibility and the long-term reliability of the solder joint. Designers should verify that the selected termination finish is compatible with their specific reflow profile and solder alloy composition.

Thermal Management and Operating Temperature Range of the KEMET T491 Series

The KEMET T491 series operates reliably across a temperature range of -55°C to +125°C, encompassing industrial and extended temperature applications. However, the maximum power dissipation capability of the device decreases with increasing ambient temperature, requiring thermal derating at elevated operating temperatures.

The relationship between temperature and maximum allowable power dissipation is defined by a temperature compensation multiplier. At 85°C ambient temperature, for example, the maximum power dissipation is reduced to approximately 50% of the room temperature rating. At 125°C, the maximum power dissipation is further reduced to approximately 20% of the room temperature rating.

Designers must account for this temperature derating when calculating the maximum allowable ripple current or ripple voltage in applications where the capacitor will operate at elevated temperatures. Failure to apply appropriate temperature derating can result in excessive power dissipation, leading to accelerated aging and potential device failure.

Equivalent Series Resistance and Frequency Response in the KEMET T491 Series

Equivalent series resistance (ESR) is a fundamental parameter that characterizes the AC performance of the KEMET T491 series. ESR decreases with increasing frequency, following a predictable curve that is documented in the device's performance characteristics. At low frequencies (below 1 kHz), ESR values are relatively high, while at higher frequencies (above 100 kHz), ESR approaches its minimum value.

The frequency-dependent behavior of ESR directly impacts the device's ability to handle AC ripple current. Applications requiring low impedance at specific frequencies benefit from the T491's ESR characteristics, which improve at higher frequencies. This makes the T491 particularly suitable for switching power supply applications where ripple frequencies typically range from 100 kHz to several megahertz.

Capacitance also exhibits frequency-dependent behavior, with a slight decrease in capacitance value at higher frequencies. This effect is typically less than 10% across the operating frequency range and can be accounted for in circuit design calculations using the provided performance curves.

Ripple Current and Ripple Voltage Handling in the KEMET T491 Series

The KEMET T491 series can withstand AC ripple current and voltage superimposed on the DC bias voltage, subject to two fundamental constraints. First, the positive peak AC voltage plus any DC bias voltage must not exceed the DC voltage rating of the capacitor. Second, the negative peak AC voltage in combination with any bias voltage must not exceed the allowable reverse voltage limits specified for the device.

The maximum allowable ripple current is determined by the maximum power dissipation capability of the device and its equivalent series resistance at the ripple frequency. The relationship is expressed mathematically as: I(max) = √(P max / R), where I is the rms ripple current in amperes, P max is the maximum power dissipation in watts, and R is the ESR in ohms at the specified frequency.

Similarly, the maximum allowable ripple voltage is calculated using the formula: E(max) = Z √(P max / R), where E is the rms ripple voltage in volts and Z is the impedance in ohms at the specified frequency.

The maximum power dissipation rating varies by case size and must be reduced when operating at elevated ambient temperatures. Designers should consult the device's performance tables to determine the appropriate power dissipation rating for their specific case size and operating temperature.

Reverse Voltage Considerations and Polarity Protection in the KEMET T491 Series

The KEMET T491 series consists of polar devices that can be permanently damaged or destroyed if connected with incorrect polarity. The positive terminal is identified on the capacitor body by a stripe marking and, in some cases, by a beveled edge on the component body.

A small degree of transient reverse voltage is permissible for short periods, with specific limits defined in the device documentation. However, the capacitors should not be operated continuously in reverse mode, even within these permissible limits. Continuous reverse voltage operation can degrade the oxide layer and lead to increased leakage current and eventual device failure.

Circuit designers must implement polarity protection measures to prevent accidental reverse connection. This can be accomplished through careful PCB layout, use of keyed connectors, or inclusion of protective diodes in the circuit design. In applications where reverse voltage transients are possible, the circuit design should limit the magnitude and duration of such transients to within the specified allowable limits.

Surface Mount Assembly and Soldering Compatibility of the KEMET T491 Series

The KEMET T491 series is fully compatible with modern surface mount assembly processes, including wave soldering (single or dual), convection reflow, infrared (IR) reflow, and vapor phase reflow techniques. The symmetrical, compliant terminations of the T491 ensure reliable solder joint formation across a range of reflow profiles.

Preheating of components prior to reflow is recommended to minimize thermal stress on the device and the PCB. The recommended reflow profile conditions reflect the IPC/J-STD-020D standard for moisture sensitivity testing. The devices can safely withstand a maximum of three reflow passes at these conditions, allowing for rework operations if necessary.

For the larger case sizes (such as the X/7343-43 configuration with a 4.3 mm profile), wave soldering is possible but requires careful process development due to the tall profile. Hand soldering should be performed with care, focusing heat on the solder pad rather than the molded case body. Once solder reflow occurs, the soldering iron should be removed immediately to avoid thermal damage to the component.

During typical reflow operations, a slight darkening of the gold-colored epoxy may be observed. This darkening is normal and does not indicate a defect or degradation of the component. The marking permanency is not affected by this color change.

Land Pattern Design and PCB Layout for the KEMET T491 Series

Proper land pattern design is essential for achieving reliable solder joints with the KEMET T491 series. Three density levels are defined to accommodate different PCB design requirements and manufacturing capabilities.

Density Level A is recommended for low-density product applications and wave solder processes. This density level provides a wider process window for reflow solder operations and is suitable for applications where component density is not a primary constraint.

Density Level B accommodates products with moderate component density and provides a robust solder attachment condition for reflow solder processes. This density level represents a balance between process robustness and space efficiency.

Density Level C is designed for high-density product applications where space constraints are significant. Before implementing the minimum land pattern variations associated with Density Level C, designers should perform qualification testing based on the conditions outlined in IPC standard 7351 (IPC-7351) to ensure solder joint reliability in their specific manufacturing environment.

The specific land dimensions for each case size and density level are provided in the device documentation. Designers should reference these dimensions when creating PCB layouts to ensure compatibility with their manufacturing processes.

Tape and Reel Packaging Standards for the KEMET T491 Series

The KEMET T491 series is packaged in embossed plastic carrier tape on 7-inch and 13-inch reels in accordance with EIA Standard 481. This packaging system is fully compatible with all tape-fed automatic pick-and-place systems used in modern surface mount assembly operations.

The carrier tape dimensions are standardized at either 8 mm or 12 mm width, depending on the component case size. The embossed cavities in the carrier tape are precisely dimensioned to hold the components securely while allowing for vertical removal after the cover tape is removed.

Component rotation within the tape cavity is limited to a maximum of 20 degrees for both 8 mm and 12 mm tape widths, ensuring consistent component orientation during automated placement. Lateral movement of components is restricted to a maximum of 0.5 mm, maintaining precise positioning for high-speed placement equipment.

The cover tape peel strength is specified to ensure reliable removal during the pick-and-place process. The total peel strength of the cover tape from the carrier tape is defined by specific force requirements, with the pull direction opposite to the direction of carrier tape travel.

Packaging quantities vary by case size and reel configuration. The 7-inch reel format is suitable for smaller production runs or component evaluation, while the 13-inch reel format accommodates larger volume production requirements. Specific packaging quantities for each case size are documented in the device's packaging information tables.

Environmental Compliance and Regulatory Certifications of the KEMET T491 Series

The KEMET T491 series meets RoHS compliance requirements (6/6) according to Directive 2002/95/EC when ordered with 100% tin solder, gold-plated terminations, or non-magnetic 100% tin solder. This compliance ensures that the components do not contain restricted substances such as lead, cadmium, mercury, hexavalent chromium, polybrominated biphenyls, or polybrominated diphenyl ethers.

The epoxy molding compound used in the T491 series is halogen-free and complies with UL94 V-0 flammability standards. The molded epoxy also complies with outgassing testing requirements under ASTM E 595, ensuring that volatile organic compounds released during thermal processing remain within acceptable limits.

Lead-free terminations are standard on the T491 series, supporting the transition to lead-free manufacturing processes across the electronics industry. The tin-based termination finishes provide excellent wetting characteristics with lead-free solder alloys, ensuring reliable solder joint formation in modern assembly processes.

Storage and Shelf Life Requirements for the KEMET T491 Series

Proper storage conditions are essential for maintaining the solderability and performance of the KEMET T491 series. KEMET recommends that maximum storage temperature not exceed 40°C and maximum storage humidity not exceed 60% relative humidity. Temperature fluctuations should be minimized to avoid condensation on the components, and storage atmospheres should be free of chlorine and sulfur-bearing compounds.

While the tantalum chip capacitors themselves are robust components, the solderability of the terminations can be degraded by exposure to high temperatures, high humidity, corrosive atmospheres, and extended storage periods. Packaging materials can also be affected by high temperature storage, with reels potentially softening or warping and cover tape peel force increasing over time.

For optimized solderability, component stock should be used promptly, preferably within three years of receipt. Designers and procurement personnel should implement first-in, first-out (FIFO) inventory management practices to ensure that older stock is utilized before newer components, minimizing the risk of solderability degradation due to extended storage.

Conclusion

The KEMET T491 series represents a mature, reliable solution for surface mount capacitor applications across industrial, telecommunications, and consumer electronics markets. The combination of proven solid tantalum technology, modern manufacturing processes, and comprehensive performance documentation enables designers to confidently specify these components for demanding applications. The availability of multiple capacitance values, voltage ratings, tolerance options, and termination finishes provides the flexibility needed to optimize designs for specific performance and cost requirements. Adherence to recommended storage conditions, proper PCB layout practices, and appropriate thermal derating ensures long-term reliability and consistent performance throughout the product lifecycle.

Frequently Asked Questions (FAQ)

Q1. What is the difference between the ±10% and ±20% tolerance options available in the KEMET T491 series?

A1. The KEMET T491 series offers two tolerance options to accommodate different circuit requirements and cost considerations. The ±10% tolerance option, designated by the letter "K" in the part number, provides tighter capacitance control and is suitable for applications where circuit performance is sensitive to capacitance variation, such as precision filtering or timing circuits. The ±20% tolerance option, designated by the letter "M", offers broader tolerance limits and is appropriate for applications where the circuit can tolerate greater capacitance variation without performance degradation. The ±20% option typically provides cost advantages for high-volume applications where the broader tolerance is acceptable.

Q2. How does temperature affect the maximum power dissipation rating of the KEMET T491 series?

A2. The maximum power dissipation capability of the KEMET T491 series decreases significantly with increasing ambient temperature. At room temperature (approximately 25°C), the device operates at its full rated power dissipation. However, as ambient temperature increases, a temperature compensation multiplier is applied to reduce the maximum allowable power dissipation. For example, at 85°C ambient temperature, the maximum power dissipation is typically reduced to approximately 50% of the room temperature rating, and at 125°C, it is further reduced to approximately 20%. Designers must apply these temperature derating factors when calculating maximum allowable ripple current or ripple voltage in applications where the capacitor will operate at elevated temperatures.

Q3. What are the key differences between the available termination finishes for the KEMET T491 series?

A3. The KEMET T491 series offers four termination finish options, each suited to different assembly processes and environmental requirements. The standard 100% matte tin (Sn) termination, designated by "T", provides excellent wetting characteristics and compatibility with lead-free solder systems, making it the most common choice for modern assembly processes. Gold-plated terminations, designated by "G", offer superior corrosion resistance and are preferred for high-reliability applications or when using conductive epoxy attachment processes. Non-magnetic 100% tin terminations, designated by "N", are specified for applications where magnetic properties must be minimized. Standard solder-coated tin-lead (SnPb) terminations, designated by "H", are available for legacy applications or specific customer requirements. The choice of termination finish should be based on the specific assembly process, solder alloy composition, and environmental requirements of the application.

Q4. Can the KEMET T491 series withstand reverse voltage, and what precautions should be taken?

A4. The KEMET T491 series consists of polar devices that can be permanently damaged if connected with incorrect polarity. While a small degree of transient reverse voltage is permissible for short periods, the specific limits are defined in the device documentation and should not be exceeded. Continuous reverse voltage operation, even within permissible limits, can degrade the oxide layer and lead to increased leakage current and eventual device failure. Circuit designers must implement polarity protection measures to prevent accidental reverse connection. This can be accomplished through careful PCB layout with clear polarity markings, use of keyed connectors, or inclusion of protective diodes in the circuit design. In applications where reverse voltage transients are possible, the circuit design should limit the magnitude and duration of such transients to within the specified allowable limits.

Q5. What is the maximum number of reflow passes that the KEMET T491 series can safely withstand?

A5. The KEMET T491 series can safely withstand a maximum of three reflow passes at the recommended reflow profile conditions specified in the device documentation. These profile conditions reflect the IPC/J-STD-020D standard for moisture sensitivity testing. The three-pass limit allows for rework operations if necessary, such as component replacement or solder joint repair. However, designers and assembly personnel should minimize the number of reflow cycles to which components are exposed, as each reflow cycle introduces thermal stress to both the component and the PCB. Preheating of components prior to reflow is recommended to minimize thermal stress and improve solder joint reliability.

Q6. How should the KEMET T491 series be stored to maintain solderability?

A6. Proper storage conditions are essential for maintaining the solderability of the KEMET T491 series. KEMET recommends that maximum storage temperature not exceed 40°C and maximum storage humidity not exceed 60% relative humidity. Temperature fluctuations should be minimized to avoid condensation on the components, and storage atmospheres should be free of chlorine and sulfur-bearing compounds. While the tantalum chip capacitors themselves are robust, the solderability of the terminations can be degraded by exposure to high temperatures, high humidity, corrosive atmospheres, and extended storage periods. For optimized solderability, component stock should be used promptly, preferably within three years of receipt. Implementing first-in, first-out (FIFO) inventory management practices helps ensure that older stock is utilized before newer components, minimizing the risk of solderability degradation.

Q7. What is the moisture sensitivity level (MSL) classification of the KEMET T491 series, and what does it mean?

A7. The KEMET T491 series is classified as moisture sensitivity level (MSL) 1 under J-STD-020. This classification indicates that the components have unlimited floor life and do not require special moisture control measures during storage or handling prior to assembly. Unlike higher MSL classifications that require components to be stored in dry-pack conditions with desiccants and have limited floor life once the package is opened, MSL 1 components can be stored in normal working environments without special precautions. This classification simplifies inventory management and reduces the risk of moisture-related failures during assembly, making the T491 series particularly suitable for high-volume manufacturing operations.

Q8. How does equivalent series resistance (ESR) affect the performance of the KEMET T491 series in AC ripple applications?

A8. Equivalent series resistance (ESR) is a fundamental parameter that characterizes the AC performance of the KEMET T491 series and directly impacts its ability to handle AC ripple current. ESR decreases with increasing frequency, following a predictable curve documented in the device's performance characteristics. At low frequencies (below 1 kHz), ESR values are relatively high, while at higher frequencies (above 100 kHz), ESR approaches its minimum value. The maximum allowable ripple current is calculated using the formula I(max) = √(P max / R), where P max is the maximum power dissipation and R is the ESR at the ripple frequency. Applications requiring low impedance at specific frequencies benefit from the T491's ESR characteristics, which improve at higher frequencies. This makes the T491 particularly suitable for switching power supply applications where ripple frequencies typically range from 100 kHz to several megahertz.

Q9. What land pattern density levels are available for the KEMET T491 series, and how should they be selected?

A9. Three land pattern density levels are defined for the KEMET T491 series to accommodate different PCB design requirements and manufacturing capabilities. Density Level A is recommended for low-density product applications and wave solder processes, providing a wider process window for reflow solder operations. Density Level B accommodates products with moderate component density and provides a robust solder attachment condition for reflow solder processes, representing a balance between process robustness and space efficiency. Density Level C is designed for high-density product applications where space constraints are significant. Before implementing the minimum land pattern variations associated with Density Level C, designers should perform qualification testing based on IPC standard 7351 (IPC-7351) to ensure solder joint reliability in their specific manufacturing environment. The selection of density level should be based on the component density of the PCB, the manufacturing process capabilities, and the reliability requirements of the application.

Q10. What are the packaging options available for the KEMET T491 series, and how do they differ?

A10. The KEMET T491 series is packaged in embossed plastic carrier tape on 7-inch and 13-inch reels in accordance with EIA Standard 481. The carrier tape is available in either 8 mm or 12 mm width, depending on the component case size. The 7-inch reel format is suitable for smaller production runs or component evaluation, while the 13-inch reel format accommodates larger volume production requirements. Both reel formats are fully compatible with all tape-fed automatic pick-and-place systems used in modern surface mount assembly operations. The embossed cavities in the carrier tape are precisely dimensioned to hold components securely while allowing for vertical removal after the cover tape is removed. Component rotation within the tape cavity is limited to a maximum of 20 degrees, and lateral movement is restricted to a maximum of 0.5 mm, ensuring consistent component orientation during automated placement. Specific packaging quantities for each case size and reel configuration are documented in the device's packaging information tables.

Q11. How should hand soldering be performed on the KEMET T491 series to avoid damage?

A11. Hand soldering of the KEMET T491 series should be performed with care due to the difficulty in process control and the risk of thermal damage to the molded case. The soldering iron should be used to heat the solder pad rather than the component body, applying solder between the pad and the termination until reflow occurs. Once reflow occurs, the soldering iron should be removed immediately to avoid prolonged heating of the component. "Wiping" the edges of the component and heating the top surface is not recommended, as this approach can cause thermal stress and potential damage to the internal structure. Hand soldering should be considered a last resort for rework operations, with preference given to automated reflow processes that provide better temperature control and more consistent results.

Q12. What environmental compliance certifications does the KEMET T491 series meet?

A12. The KEMET T491 series meets RoHS compliance requirements (6/6) according to Directive 2002/95/EC when ordered with 100% tin solder, gold-plated terminations, or non-magnetic 100% tin solder. This compliance ensures that the components do not contain restricted substances such as lead, cadmium, mercury, hexavalent chromium, polybrominated biphenyls, or polybrominated diphenyl ethers. The epoxy molding compound used in the T491 series is halogen-free and complies with UL94 V-0 flammability standards. The molded epoxy also complies with outgassing testing requirements under ASTM E 595, ensuring that volatile organic compounds released during thermal processing remain within acceptable limits. Lead-free terminations are standard on the T491 series, supporting the transition to lead-free manufacturing processes across the electronics industry.