Abstract As capacitor manufacturing continues to advance towards smaller package applications, 3-D conformal-coated chip capacitors are an ideal solution for high capacitance, low ESR, and low voltage applications. Introduction Selecting decoupling capacitors for energy storage/transfer processing in microprocessor systems is a complex task. Due to the emphasis on product physical size, processor manufacturers typically only specify the capacitance required to meet the device's energy conversion requirements, without considering the available space for suitable capacitor arrangements. Processors used in embedded single-board computers also require higher capacitor charge-discharge performance, thus demanding a low time constant. As capacitor manufacturing continues to advance towards smaller package applications, 3-D conformal-coated chip capacitors are an ideal solution for high capacitance, low ESR, and low voltage applications. High Capacitance and Low ESR Technologies Several technologies have been developed to optimize capacitance per unit volume. For example, coated tantalum chip capacitor technology eliminates the lead frame structure of conventional voltage-scale solid tantalum capacitors, while this semiconductor-like special packaging technology significantly reduces the average size. Vishay has developed coated tantalum sheet technology for capacitor applications that meet NASA requirements. These products far exceed the volumetric efficiency of standard scaled surface mount tantalum capacitors (SMD). However, designers still need to minimize ESR, a requirement that has spurred several candidate solutions. Polymer aluminum capacitors have very low ESRs, in the range of 10mΩ or less, filling the application space between high-capacitance multilayer ceramic capacitors (MLCCs) and tantalum polymer capacitors. However, while they meet the ESR requirements for filtering applications, their volumetric efficiency is typically much lower than tantalum technology. In applications where assembly space is scarce, this technology must give way to other technologies such as tantalum. Solid tantalum capacitors Solid tantalum capacitors are available in standard and low-ESR types. Both types are fabricated using a standard leadframe structure. The ESR value of the solid tantalum low-ESR type is in the 100mΩ range at 100kHz. Since the ESR value depends on the outer surface of the anode, larger form factors generally have lower ESR values. Extensive powder development work in solid tantalum capacitors has resulted in new, lower ESR values. Improvements in surge voltage have also enhanced the capabilities of solid tantalum technology. Polymer tantalum capacitors utilize a new type of highly conductive polymer. This highly conductive polymer is used in the cathode instead of manganese dioxide. The improved conductivity of the polymer cathode leads to lower impedance and lower ESR. The low impedance also results in excellent high-frequency filtering response. Polymer tantalum capacitor technology boasts the lowest ESR, significantly lower than conventional solid tantalum capacitors of similar size. In fact, leadframe structure primarily limits the available capacitance for a given form factor. Multi-anode tantalum capacitors Currently, the dual requirements of high capacitance and low ESR are being addressed by a 3-D packaging approach: multi-anode tantalum capacitors, which eliminate the conventional leadframe. This structure achieves high capacitance in a miniaturized SMD package and is compatible with the pins of conventional voltage-scale tantalum devices. Importantly, this technology achieves very low and stable ESR. The main electrical and mechanical properties of multi-anode capacitors include: High capacitance: typically >1000F; Very low and stable ESR over the operating temperature range; Low inductance; Wide rated voltage range: 4V, 6.3V, and 10V; Low DCL <60A; Small size, low thickness 3D chip package; Leadframe-less; Standard pinout, compatible with standard voltage-rated tantalum capacitors. Decoupling capacitor applications: Today, a large number of embedded controllers are built using a single-board computer (SBC). The dominant industry standard is PC/104, which specifies a 3.8” x 3.6” form factor. New, smaller proprietary specifications are also emerging, particularly for SBCs based on 16-bit and 32-bit processors. Furthermore, PC/104 SBCs must also allow for stack-through connections of multiple PC/104 boards to fully utilize the maximum mounting height of 4.0mm (0.16"). A significant number of designers also prefer to create their own custom embedded controller solutions using a microcontroller or microprocessor with selected peripheral components. These solutions may be implemented directly on the PCB, but like ordinary SBCs, they are subject to space constraints. Therefore, materials and packaging structures must be designed to allow a capacitor to fit into the very small space between the CPU and chipset without exceeding strict height limitations. Power requirements are typically defined by the microprocessor or microcontroller manufacturer based on the voltage regulation module (VRM). Most systems are built on a synchronous buck converter capable of providing multiple voltage values. Typically, they will provide 1.5–1.8V, 3.3V, and 5.0V to the processor core, processor and chipset I/O, and various basic electrical units on the general-purpose board, respectively. The processor core voltage, or VCORE, is often a major challenge when selecting low-ESR body capacitors. Evaluation of suitable capacitor technology is crucial. This analysis examines processor manufacturers' recommendations regarding core voltage, such as specifying a suitable filter capacitor for the VCORE. A new processor requiring a 1.5V core voltage has the following exemplified requirements: Output voltage = 1.5V–1.8V; Output ripple voltage = 2% of output voltage; Output current > 14A; Output filter capacitor = 3900F/4V, ESR < 3m. The effectiveness of this new packaging technology was investigated, and the capacitor technologies described above were evaluated to determine the optimal technology for a PC/104SBC integrated output filter capacitor in terms of board layout, component height, and electrical performance. However, existing aluminum electrolytic capacitors were excluded because they exceeded the maximum height of 4.0mm (0.16"). A comprehensive review of various capacitor technologies was conducted to determine the implementation with the minimum total pins on the printed circuit board (PCB), the lowest ESR, and while meeting height constraints. A comprehensive table summarizing all Vishay's technology options is provided below. Conclusion While Polymer tantalum capacitors offer excellent ESR, the overall capacitance requirements necessitate a greater number of individual surface-mount capacitors. To achieve the required bulk capacitance, 18 255D series 330F capacitors are needed, occupying a total board space of 558 mm² (0.88 inch²). This is significantly higher than the arrangement of four Vishay 597D multi-anode tantalum capacitors.