05041A820KA79A Datasheet, PDF (42/48 Pages) AVX Corporation – Multilayer Ceramic Chip Capacitor

Surface Mounting Guide
Appendix 1: MLC Capacitors
PHYSICAL PROPERTIES
The properties of MLC’s are decided by their chemical
composition and physical makeup. As manufacturers use
slightly different compositions and designs this means that
all MLC’s do not have identical properties. Most systems
are, however, based on doped barium titanate raw materi-
als and basically similar designs. There will be minor differ-
ences in value for some of the physical constants quoted
but these should not prove significant for practical purposes.
Temperature
Coefficient of expansion (CTE)
This varies according to which axis of the chip is being
measured.
Across terminations (L)
Across chip (W)
Electrode (Pd/Ag)
11ppm/°C
13ppm/°C
16ppm/°C
It should be remembered that in attempting to match circuit
board material with MLC’s that the dynamic system should
be considered (power on temperature rise) not the static
system (uniform temperature rise).
Toper > Tamb CTEsub > CTEcap
Solder Fillet
Capacitor
Maximum Stress
Substrate
Thermal Stress 1.
Thermal Conductivity
Ceramic
Termination (Ni Bar)
Electrode (Pd/Ag)
5W/m Kelvin
380W/m Kelvin
140W/m Kelvin
These figures show the problem of predicting the thermal
behavior of MLC’s each one being different according to its
form and number of electrodes.
Table 1. Coefficients of Expansion and Conductivity
Material
CTE (ppm/°C) C (W/m Kelvin)
Alumina
7
34.6
Alloy 42
5.3
17.3
BaTi03 doped
9.5-11.5
4-5
Copper
17.6
390
Copper c 1 Invar
6.7
Filled Epoxy
18-25
0.5
FR4/G10
18
Nickel
15
86
Polyimide/Glass
12
Polyimide/Kevlar
7
Silver
19.6
419
Steel
15
46.7
Tantalum
6.5
55
Tin/Lead
27
34
Toper > Tamb CTEsub < CTEcap
Capacitor
Maximum Stress
Solder Fillet
Substrate
Thermal Stress 2.
Ceramic
CTE 9.5 to 11.5
ppm /oc
4-5 W mK
Termination
Tin-Lead and
Nickel Over
Electrodes
Silver Glass
Frit
CTE 18ppm /oc
140 W mK
CTE 18ppm /oc
Thermal Conductivity
380 W mK
CTE and Conductivity of MLC Materials.
40