WHITE PAPER Understanding Polymer and Hybrid Capacitors Advanced capacitors based on conductive polymers maximize performance and reliability The various polymer and hybrid capacitors have distinct sweet spots in terms of their ideal voltages, frequency characteristics, environmental conditions and other application requirements. In this paper, we’ll show you how to identify the best uses for each type of advanced capacitor. We’ll also highlight specific applications in which a polymer or hybrid capacitor will outperform traditional electrolytic or even ceramic capacitors. POLYMER CAPACITOR VARIETIES Polymer capacitors come in four main varieties, including the hybrid. Each type has different electrolytic and electrode Hybrid capacitor technology combines the performance benefits of materials, packaging and application targets: electrolytic and polymer capacitors. • Layered polymer aluminum capacitors use conductive Capacitors may seem simple enough, but specifying them has polymer as the electrolyte and have an aluminum cathode actually grown more complex in recent years. The reason why (see Figure 1). Depending on the specific model, these comes down to freedom of choice. The universe of capacitors capacitors cover a voltage range from 2-25V and offer has expanded greatly over the past few years, in large part capacitances between 2.2-560µF. The distinguishing because of capacitor designs that take advantage of advances electrical characteristic of these polymer capacitors is in conductive polymers. their extremely low equivalent series resistance (ESR). For example, some of our SP-Cap™ polymer capacitors have These advanced capacitors sometimes use conductive polymers ESR values as low as 3mΩ, which is among the lowest in to form the entire electrolyte. Or the conductive polymers can be used in conjunction with a liquid electrolyte in a design known as a hybrid capacitor. Either way, these polymer-based capacitors Molding Silver Paste offer a performance edge over conventional electrolytic and Resin ceramic capacitors when it comes to: Terminal • Electrical characteristics. • Stability. Al2O3 • Longevity. Silver Paste Carbon Aluminum Foil • Reliability. Terminal Polymer • Safety. Figure 1 • Life cycle cost. Panasonic Two Riverfront Plaza, 7th Floor, Newark, NJ 07102-5490 www.panasonic.com/industrial Aluminum Case the industry. Packaged in a molded resin as compact surface mount devices, these layered polymer capacitors have a low profile. As a result of the electrical and form Back Plate factor characteristics, they have applications in a variety of handheld electronic devices or other applications that require a low-profile capacitor that will not interfere with a nearby heat sink. Rubber Seal Terminal • Wound polymer aluminum capacitors are also based on conductive polymers and aluminum, but they have a wound Aluminum foil structure (see Figure 2). The wound polymer capacitors Foil cover a wider range of voltages and capacitance values Aluminum Spacer than other types of polymer capacitors. Voltages extend Foil Al O from 2.5 to 100V, while capacitances run from 3.3 to 2700µF. 2 3 Electrolyte Impregnated in Spacer Like the layered polymer capacitors, the wound style Polymer has extremely low ESR values. Some of our OS-CON™ Figure 2 capacitors, for instance, have ESR values below 5mΩ. The wound style can also be surface mounted, Molding though they are not Resin Terminal quite as compact as the layered capacitors. Terminal Silver paste Ta2O5 Sintered Tantalum Carbon • Polymer tantalum capacitors employ a conductive Polymer polymer as the electrolyte and have a tantalum cathode (see Figure 3). They span voltages from 1.8 to 35V and Figure 3 capacitances from 2.7 to 680µF. They, too, have low ESR values. They, too, have low ESR, with some of our POSCAP™ capacitors exhibiting ESR values as low as 5mΩ. Packaged in a molded resin case, the tantalum polymer capacitors are among the most compact on the market. Our POSCAP M size, for example, measures just 2.0 by 1.25 mm. Though compact, a wide range of sizes is available for this capacitor type. Panasonic Two Riverfront Plaza, 7th Floor, Newark, NJ 07102-5490 www.panasonic.com/industrial Aluminum Case • Polymer hybrid aluminum capacitors. As their name suggests, these capacitors use a combination of a liquid and conductive polymer to serve as the electrolyte (see Figure Back Plate 4) and aluminum as the cathode. Think of this technical approach as the best of both worlds: The polymer offers high conductivity—and a correspondingly low ESR. The liquid portion of the electrolyte, meanwhile, can withstand high Rubber Seal Terminal voltages and provide higher capacitance ratings due to its large effective surface area. The hybrid capacitors offer a voltage range from 25 to 80V and capacitances between 10 Aluminum and 330µF. At 20 to 120mΩ, ESR values for hybrids are higher Foil than other types of polymer capacitors, but still very low Aluminum Spacer considering the higher power applications they address (see Foil sidebar). Al2O3 Hybrid Electrolyte Impregnated in Spacer POLYMER CAPACITOR ADVANTAGES Polymer + Electrolyte Liquid Despite differences in their materials and construction, the four Figure 4 types of polymer capacitors share a collection of desirable electrical properties: • Great frequency characteristics. Thanks to their ultra low ESR values, polymer capacitors have a low impedance near their resonance point (see Figure 5). And lower impedance Figure 5 reduces AC ripple in power circuits. Our testing has ESR lowers impedance near the resonance point, reducing AC ripple. IMPEDANCE CHARACTERISTICS Impedance Capacitance: ½πfC Inductance: 2 fL, where L = ESL π Resistance: ESR Impedance (Z) Impedance (Z) Frequency Frequency Z Large: Z Small: Ripple Ripple Z Large: Z Small: Panasonic Two Riverfront Plaza, 7th Floor, Newark, NJ 07102-5490 www.panasonic.com/industrial DC Bias 10 STABLE CAPACITANCEDC Bias Reliable Capacitors For IT 100 DC Bias 10 -10 Infrastructure 0 -2-10 -10 Information technology infrastructures have a little-known ) -3-20 (% -20 C weak link: The capacitors in their power supplies. ) -4-30 / (% ) dC C -30 -5-40 / Conventional electrolytic capacitors tend to fail prematurely (% C dC -40 when their liquid electrolyte dries up‚ which happens in / -6-50 dC -50 response to elevated temperatures and long on times. -7-60 -60 -8-70 Conventional tantalum capacitors are one possible solution -8-70 to these premature failures. However, tantalums require -90 01234567 -9-80 voltage derating to avoid a very undesirable failure mode— DC Bias (V) 01234567 -90 DC Bias (V) namely, the potential for fires. 01234567 DC Bias (V) More advanced polymer-based capacitors have emerged Temperature Range 2200 as a way to improve lifecycle and reliability of IT equipment Temperature Range 2200 such as servers, switches, routers and modems. Temperature Range ) 2200 (% C 1100 ) Polymer wound capacitors such as OS-CON do not have a C/ (% C 1100 ) C/ liquid electrolyte and therefore can have extremely long life. (% C 1100 C/ 0 POSCAP polymer-tantalum capacitors contain no oxygen --5555--3535 --115555 2525 4545 6655 8855 11005 0 in their formulation. So they are not prone to combustion --5555--3535 --115555 2525 4545 6655 8855 11005 0 Temp. ( ) upon failure. SP-Caps also have a similar benign failure --5555--3535 --115555 --110 2525 4545 6655 8855 11005 mode. --110 Temp. ( ) --110 Temp. ( ) All three families of advanced capacitor also offer the --220 features required for information infrastructure: --220 --220 -3300 • Compact size. -3300 • Low ESR MLCC -3300 • High Ripple Current MLCCMultilayer ceramic capacitor (6.3V47µF/3216/X5R) • Long Life. PolymerMLCCMultilayer ceramic capacitor capacitor (6.3V47µF/3216/X5R) PolymerPOSCAP,Multilayer ceramicSP-Cap capacitor capacitoror OS-CON (6.3V47µF/3216/X5R) (6.3V47µF) PolymerPOSCAP, SP-Cap capacitor Figureor OS-CON 6 (6.3V47µF) POSCAP, SP-Cap or OS-CON (6.3V47µF) revealed as much as a fivefold reduction in peak-to-peak deliver subpar performance in the field. Hybrid capacitors voltage changes when comparing polymer capacitors to add another dimension to capacitance stability. They keep conventional low-ESR tantalum capacitors. a stable capacitance in the face of common operating conditions—high frequencies and low temperatures—that • Stable capacitance. With ceramic capacitors, capacitance reduce the capacitance of conventional liquid electrolytic drifts in response to temperature changes and DC bias. capacitors. Polymer capacitors have no such problem and remain (see Figure 7). stable over time (see Figure 6). This stability is particularly important in industrial and automotive applications, which • Enhanced safety. Conventional electrolytic capacitors tend to experience fluctuations in operating temperatures. can suffer from safety issues that could cause them to We’ve seen cases where elevated temperatures caused short circuit and fail. The problem arises when electrical an effective capacitance loss of 90% or more for ceramic or mechanical stresses create defects or discontinuities in capacitors, meaning that the conventional capacitors the oxide film that forms the capacitor’s dielectric. Polymer Panasonic Two Riverfront Plaza, 7th Floor, Newark, NJ 07102-5490 www.panasonic.com/industrial HYBRID CAPACITOR capacitors have a self-healing capability that eliminates Capacitance vs. Frequency this failure mode. The repair takes place in response to the CapacitancePERFORMANCE vs. Frequency 1000.0000 joule heating that occurs when a dielectric