SMD capacitors

It is important to double-check the failure criteria of specific vendors. For example, Panasonic SMD capacitors allow for a 30% fall in capacitance by the end of life. That means, for a 20% tolerance capacitor, you need to start with a nominal value 79% higher than your calculated value (also don t forget to account for the additional fall in capacitance at low temperatures). 

Many commercial capacitors can be used as thermometers since they show a strong dependence of their capacitance on temperature. Figure 9.15 shows the low-temperature C(T) curve for a commercial smd capacitor (ceramic capacitor KEMET-Y5V). 

Fig. 9.15. Capacitance of an smd capacitor (ceramic capacitor KEMET-Y5V) as a function of temperature.

Except for some exotic surface-mount technology (SMT/SMD) aluminum electrolytic capacitor types with solid electrolyte systems, in general, an aluminum electrolytic capacitor contains a wound capacitor element (the coil), impregnated with liquid electrolyte, connected to terminals, and sealed in a can (with a rubber plug at the end). The aluminum in the name,... 

In Table 4-2, we have the standard SMD component sizes. Note that usually, most pick and place machines cannot mount anything bigger than size 1515. So larger components may need to be hand-soldered. For ceramic capacitors, reliability requirements call for a certain... 

There are apparently customers who soldered on ceramic capacitors in their power supplies and found the clock was just too low. They figured the capacitance was above the guaranteed upper tolerance band (a rare event with commercial ceramics ), and shipped them right back to their manufacturers. But the problem was only that as soon as the PCBs went through the soldering process, age reset (or de-aging) occurred and so capacitance rose. If only they had waited for some more time, their clocks would have been right on However, I would have preferred SMD him capacitors if stability was so important. 

The class of ferroelectric materials have a lot of useful properties. High dielectric coefficients over a wide temperature and frequency range are used as dielectrics in integrated or in smd (surface mounted device) capacitors. The large piezoelectric effect is applied in a variety of electromechanical sensors, actuators and transducers. Infrared sensors need a high pyroelectric coefficient which is available with this class of materials. Tunable thermistor properties in semiconducting ferroelectrics are used in ptcr (positive temperature coefficient... 

Figure 1.51 (a) Ta capacitors as surface mounted devices (SMD) (b) corresponding schemes (c) SEM of sponge-like anode after oxide formation (d) SEM with cross-section through aTa/Ta205 particle. 

Other components such as capacitors or coils may be integrated in the network. As this requires an extra processing such components are also often mounted on the network, usually as SMDs. The network may also be used to mount integrated circuits and so provide complete circuit blocks. 

The new user of surface mount designs (SMDs) must rapidly learn the packaging sizes and types for SMDs. Resistors, capacitors, and most other passive devices come in two-terminal packages, as shown in Fig. 11.17, which have end-terminations designed to rest on substrate pads/lands. 

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