Low Inductance Capacitors Introduction The signal integrity characteristics of a Power Delivery Network (PDN) The ESL of a capacitor determines the speed of energy transfer to a load. are becoming critical aspects of board level and semiconductor package The lower the ESL of a capacitor, the faster that energy can be transferred designs due to higher operating frequencies, larger power demands, and the to a load. Historically, there has been a tradeoff between energy storage ever shrinking lower and upper voltage limits around low operating voltages. (capacitance) and inductance (speed of energy delivery). Low ESL devices These power system challenges are coming from mainstream designs typically have low capacitance. Likewise, higher capacitance devices with operating frequencies of 300MHz or greater, modest ICs with power typically have higher ESLs. This tradeoff between ESL (speed of energy demand of 15 watts or more, and operating voltages below 3 volts. delivery) and capacitance (energy storage) drives the PDN design topology that places the fastest low ESL capacitors as close to the load as possible. The classic PDN topology is comprised of a series of capacitor stages. Low Inductance MLCCs are found on semiconductor packages and on Figure 1 is an example of this architecture with multiple capacitor stages. boards as close as possible to the load. An ideal capacitor can transfer all its stored energy to a load instantly. A real capacitor has parasitics that prevent instantaneous transfer of a capacitors stored energy. The true nature of a capacitor can be modeled as an RLC equivalent circuit. For most simulation purposes, it is possible to model the characteristics of a real capacitor with one capacitor, one resistor, and one inductor. The RLC values in this model are commonly referred to as equivalent series capacitance (ESC), equivalent series resistance (ESR), and equivalent series inductance (ESL). Slowest Capacitors Fastest Capacitors Semiconductor Product VR Bulk Board-Level Package-Level Die-Level Low Inductance Decoupling Capacitors Figure 1 Classic Power Delivery Network (PDN) Architecture LOW INDUCTANCE CHIP CAPACITORS INTERDIGITATED CAPACITORS The key physical characteristic determining equivalent series inductance The size of a current loop has the greatest impact on the ESL characteristics (ESL) of a capacitor is the size of the current loop it creates. The smaller of a surface mount capacitor. There is a secondary method for decreasing the current loop, the lower the ESL. A standard surface mount MLCC is the ESL of a capacitor. This secondary method uses adjacent opposing rectangular in shape with electrical terminations on its shorter sides. A current loops to reduce ESL. The InterDigitated Capacitor (IDC) utilizes Low Inductance Chip Capacitor (LICC) sometimes referred to as Reverse both primary and secondary methods of reducing inductance. The IDC Geometry Capacitor (RGC) has its terminations on the longer side of its architecture shrinks the distance between terminations to minimize the rectangular shape. current loop size, then further reduces inductance by creating adjacent opposing current loops. When the distance between terminations is reduced, the size of the current loop is reduced. Since the size of the current loop is the primary driver of An IDC is one single capacitor with an internal structure that has been inductance, an 0306 with a smaller current loop has significantly lower optimized for low ESL. Similar to standard MLCC versus LICCs, the ESL then an 0603. The reduction in ESL varies by EIA size, however, ESL is reduction in ESL varies by EIA case size. Typically, for the same EIA size, an typically reduced 60% or more with an LICC versus a standard MLCC. IDC delivers an ESL that is at least 80% lower than an MLCC. The Important Information/Disclaimer is incorporated in the catalog where these specifications came from or available online at www.avx.com/disclaimer/ by reference and should be reviewed in full before placing any order. 74Low Inductance Capacitors Introduction LAND GRID ARRAY (LGA) CAPACITORS LOW INDUCTANCE CHIP ARRAYS (LICA) Land Grid Array (LGA) capacitors are based on the first Low ESL MLCC The LICA product family is the result of a joint development effort between technology created to specifically address the design needs of current day AVX and IBM to develop a high performance MLCC family of decoupling Power Delivery Networks (PDNs). This is the 3rd low inductance capacitor capacitors. LICA was introduced in the 1980s and remains the leading technology developed by AVX. LGA technology provides engineers with choice of designers in high performance semiconductor packages and high new options. The LGA internal structure and manufacturing technology reliability board level decoupling applications. eliminates the historic need for a device to be physically small to create LICA products are used in 99.999% uptime semiconductor package small current loops to minimize inductance. applications on both ceramic and organic substrates. The C4 solder The first family of LGA products are 2 terminal devices. A 2 terminal 0306 ball termination option is the perfect compliment to flip-chip packaging LGA delivers ESL performance that is equal to or better than an 0306 8 technology. Mainframe class CPUs, ultimate performance multi-chip terminal IDC. The 2 terminal 0805 LGA delivers ESL performance that modules, and communications systems that must have the reliability of 5 approaches the 0508 8 terminal IDC. New designs that would have used 8 9s use LICA . terminal IDCs are moving to 2 terminal LGAs because the layout is easier for LICA products with either Sn/Pb or Pb-free solder balls are used for a 2 terminal device and manufacturing yield is better for a 2 terminal LGA decoupling in high reliability military and aerospace applications. These versus an 8 terminal IDC. LICA devices are used for decoupling of large pin count FPGAs, ASICs, LGA technology is also used in a 4 terminal family of products that AVX is CPUs, and other high power ICs with low operating voltages. sampling and will formerly introduce in 2008. Beyond 2008, there are new When high reliability decoupling applications require the very lowest ESL multi-terminal LGA product families that will provide even more attractive capacitors, LICA products are the best option. options for PDN designers. 470 nF 0306 Impedance Comparison 1 0306 2T-LGA 0306 LICC 0306 8T-IDC 0603 MLCC 0.1 0.01 0.001 1 10 100 1000 Frequency (MHz) Figure 2 MLCC, LICC, IDC, and LGA technologies deliver different levels of equivalent series inductance (ESL). The Important Information/Disclaimer is incorporated in the catalog where these specifications came from or available online at www.avx.com/disclaimer/ by reference and should be reviewed in full before placing any order. 75 Impedance (ohms)