积层陶瓷电容 (mlcc) 
mlcc 特性曲线

temperature coefficient
class 1 (temperature compensation series)

class 2 (high dielectric constant series)

dc voltage coefficient

aging rate
the capacitance and dissipation factor of class 2 capactiors decreases with time. it is known as 'again' that follows a logarithmic low and expressed in terms of an aging constant. aging is caused by a gradual realignment of the crystalline structure of the ceramic. the aging constant is defined as the percentage loss of capacitance at a 'time decade'. the law of capacitance aging is expressed as following equation:

ct2=ct1 x (1k x log10(t2/t1))
ct1: capacitance after t1 hours of start aging.
ct2: capacitance after t2 hours of start aging.
k: aging constant (capacitance decrease per decade)
t1, t2: time in hours from start of aging.
a typical curve of aging rate is shown in following figure.


when heating the capacitors above curie temperature (130°c~150°c) the capacitance can be renew. so capacitance of 2 capacitors will be complete deaged by soldering process; subsequently a new aging process begins.
because of aging, it is specified an age for measurement to meet the prescribed tolerance for class 2 capacitors. normally, 1000 hours (t2=1000 hrs) is defined.
