Process improvements and material advances are enabling today’s ceramic capacitors to operate in high-frequency, high-temperature and highly transient environments. These ceramic capacitors handle higher amounts of charge in smaller packages and are allowing design engineers to achieve higher levels of performance in more efficient capacitor designs.
Ceramic capacitors are fixed-value capacitors with a ceramic dielectric. The most common type is the surface-mount multilayer ceramic capacitor, although leaded-disc ceramic through-hole capacitors and microwave-leadless-disc ceramic capacitors are also used in some applications. The composition of the ceramic material defines the electrical behavior and therefore applications.
With today’s electronics devices required to operate at higher frequencies, capacitor suppliers have improved ceramic formulations capable of sustained operation at higher frequencies.
For instance, AVX Corp. offers the GXOS series of ultra-broadband capacitors (Figure 1) designed to address DB blocking from 16 kHz to 40 GHz. The capacitors are designed to mount on strip lines with widths of less than 20 mils. The capacitors are rated at 0.1 microfarads with a voltage rating of 6.3 VDC at 85 °C.
Figure 1: The AVX GXOS Series ultra-broadband capacitors. (Source: AVX Corporation)
Piezoelectric noise reduction is another area of focus by capacitor suppliers. Ceramic capacitors with reduced piezoelectric noise reduce noise generation in high dv/dt circuitry. KEMET Electronics Corp. recently introduced what it claims is the world’s first 250 V-rated 0402 case-size capacitor with values up to 330 picofarads. The material used in the capacitors eliminates piezoelectric noise, offers high-thermal stability and no capacitance delay with time.
Miniaturization continues to occur in ceramic capacitors. According to Ron Demcko, at AVX, ceramic formulations continue to be developed and improved for stable operation across temperature and are able to withstand higher voltage stresses, which enable the use of thinner dielectric layers.
Precision-processing technology has enabled Murata to develop one of the smallest case sizes on the market, the 008004, which measures 0.25 x 0.125 mm (Figure 2). These capacitors require a mounting area approximately half that of a 0.1005 case (0.4 x 0.2 mm), which was previously the smallest case size.
Figure 2: Murata’s 008004 case-size capacitors.(Source: Murata Americas)
Murata has also applied this technology to pack more capacitance into other industry-standard case sizes. The company now offers 2.2 microfarad capacitors in the 0201 case (0.024 x 0.012 in.) and 22 microfarad capacitors in the 0402 (0.039 x 0.020 in.) case size.
High-temperature Operation
The ability to withstand sustained high temperatures is another characteristic of newer ceramic capacitors. AVX’s AT Series MLCCs are capable of long-term operation to 250 °C in both military and commercial applications. The capacitors are offered in capacitances ranging from 100 pF to 1 microfarad, with tolerances of +/-5, 10 or 20 percent.
KEMET has also done extensive work in C0G (NP0) and X7R formulations, producing ceramic capacitors able to operate at temperatures beyond 150 °C and at voltages exceeding 200 V, noted Scott Carson, product marketing manager.
According to Carson, KEMET developed custom dielectric formulations that possess high reliability at increasing temperatures, improved raw materials with ultra-high purity, high crystallinity and smaller particle sizes, improved methods of dispersions and milling powders to make the ceramic and electrode layers, as well as refined the technology of stacking and lamination thinner layers.
The high-temperature soldering and board assembly environments many capacitors must withstand has also created a need for capacitors that can withstand board flexing. AVX, for example, offers a FlexiTerm™ termination option that allows some MLCCs to handle up to 5 mm of board flexure without failures.
Similarly, the VJ ….31X automotive series capacitors (Figure 3) from Vishay Intertechnology have polymer-flexible terminations for added protection against board-flexure damage. These capacitors are available with C0G (NP0), X7R and X8 die.
Figure 3: Vishay’s VJ ….31X automotive-series capacitors. (Source: Vishay Intertechnology)
Through-hole Capacitors
Although surface-mount ceramic capacitors have seen the majority of improvements, some of these advancements are filtering down to through-hole capacitors as well. The need for through-hole ceramic capacitors remains, such as in environments where high vibration, welding or custom lead forming is present or where PC boards are impractical, according to Frank Yang, Application Engineer for Murata Americas.
To this end, Murata launched its RCE series axial-leaded-monolithic ceramic capacitors for automotive applications. The capacitors comply with AEC-Q200 automotive requirements and the ISO7637-2 surge test. The devices have a capacitance range of 1.0 picofarad to 22 microfarads, and a rated voltage of 25 V to 1 kV.
KEMET expanded its line of Animax high-temperature axial capacitors (Figure 4), utilizing the same internal technologies used in KEMET’s surface-mount X8L and X8R dielectric platforms. Designed for high-vibration environments, the capacitors are designed to withstand temperatures as high as 150 °C with capacitance to 2.2 microfarads and voltages up to 50 V.
Figure 4: KEMET’s Animax high-temperature axial capacitors. (Source: KEMET Electronics Corp.)
The Animax capacitors are designed for decoupling, bypass and filtering in environments such as down-hole oil exploration, automotive, defense and aerospace.
Market Steady
Like other component sectors, the ceramic-capacitor market has not been immune to economic downturns and world events that impact the electronics supply chain. The earthquake in Tohoku, Japan four years ago impacted the supply of barium titanate and other titanate materials used in manufacturing ceramic capacitors, in turn prompting OEMs to stock up on ceramic capacitors. This eventually led to an oversupply.
Current market research reports project the ceramic-capacitor market to grow over the next few years due to demand from smartphones and mobile devices, TVs and computers. Price erosion has long been a trend in capacitors, particularly multilayer-ceramic-chip capacitors (MLCCs). This is particularly true with high-CV components, according to Mark Obuszewski, Worldwide Business/Marketing Manager at AVX.
Mitigating the price erosion that has been in high demand, particularly from the automotive and smartphone sectors, has helped stabilize prices, noted Murata’s Frank Yang. Capacitor suppliers believe the key players in the market will remain so for the foreseeable future.
“We don’t expect any major consolidation among the ceramic suppliers,” says AVX’s Mark Obuszewski. “Some of the smaller suppliers may be purchased, but we don’t expect a major shake-up.”