©
2013 CARTS International - ECA (Electronics Components, Assemblies & Materials Association), Arlington, VA
CARTS International 2013 Proceedings
, March 25-28, Houston, Texas, USA
High Voltage Multi-Layer Ceramic Capacitors for Use at High Temperatures
Jim Magee, John Bultitude, Lonnie Jones, Mark Laps, Javier Zavala, Ana Garza, Glenda Torres,
Wanda Andrews, Abhijit Gurav, Corey Antoniades and Reggie Phillips
KEMET
Electronics Corporation, 2835 KEMET Way, Simpsonville, SC 29681, USA
Tel: +01-864-228-4052, Fax: +01-864-967-6823, e-mail: reggiephillips@kemet.com
Abstract
Multi-layer ceramic capacitors (MLCC) rated to 200Vdc for use at 200
o
C were developed using a high temperature C0G
dielectric technology compatible with nickel electrodes. To meet the need for improved pulse detonator performance larger
case size (2824 to 4540) capacitors rated to 2000Vdc at 200
o
C were then developed using this technology. The growing
demand for higher temperature electronics capable of exploiting new reserves of oil and natural gas led us to develop a
range of smaller case (0805 to 2225), high voltage designs (> 500V to 2000V). The electrical characteristics of these
surface mounted MLCC, such as insulation resistance, voltage breakdown, impedance and ESR, are described. The basic
properties of some selected capacitors are compared to MLCC made with precious metal electrodes at high temperatures to
explain the performance enhancements of this new product range. Reliability data at 200
o
C is presented for some MLCC
examples from the new product range and the mechanisms associated with reliable high temperature performance are
reviewed. This new range of MLCC will allow designers of high temperature electronics to realize reliable, miniaturized
circuit designs with stable capacitance at high voltage and high temperature.
Introduction
In a previous presentation
1
work to develop a range of high temperature capacitors based on a C0G type dielectric with
nickel electrodes was described. The bulk dielectric material used in the dielectric formulation was calcium zirconate. The
oxygen present is held tightly within the crystal lattice that results in a very low level of oxygen defects. Since the presence
of these defects is minimized the migration of oxygen vacancies at elevated temperatures does not compromise the
reliability of the BME MLCC as described for other more common types of dielectric such as X7R and X5R based on
barium titanate. High temperature MLCC rated to 200V for use at 200
o
C were successfully qualified using a C0G
dielectric formulation based on calcium zirconate. A range of higher voltage, large case size pulse detonation capacitors
was subsequently developed to meet downhole market need for more reliable capacitors in this application. These
developments and the application of this technology to smaller case size, high temperature rated MLCC are described
below. The electrical properties are reviewed and compared to high temperature MLCC based on X7R dielectrics made
with precious metal electrodes.
High Temperature C0G Dielectric Development
Multilayer ceramic capacitors using nickel base metal electrodes were originally developed using barium titanate based
dielectrics. The high permittivity of these ferroelectric materials provided high capacitance; low voltage solutions in X5R
and later X7R class 2 capacitors. To achieve reliable performance reduction resistant formulations were developed together
with re-oxidation processes to replace vacancies formed during the high temperature firing in reduced atmosphere. This
technology was applied to C0G dielectrics using calcium zirconate as the main component in order to replace the more
expensive precious metal compatible systems that typically use barium-rare earth titanates
2
. The C0G dielectrics were also
developed to be Pb-free unlike some of the precious metal compatible dielectrics. In later work
1
Highly Accelerated Life
Testing (HALT) was performed on 50V rated MLCC made from the same batches of calcium zirconate based dielectric
with and without re-oxidation. An example of this work is shown in Figure 1.
©
2013 CARTS International - ECA (Electronics Components, Assemblies & Materials Association), Arlington, VA
CARTS International 2013 Proceedings
, March 25-28, Houston, Texas, USA
Figure 1. HALT test of 1206, 47nF, 50V rated C0G with and without re-oxidation
There was no degradation of IR with and without re-oxidation even at temperatures of 175
o
C at 12 x the rated voltage of the
MLCC for 92hours. These results were attributed to the much higher affinities of calcium and zirconium for oxygen so
tightly binding this within the crystal lattice of the dielectric. The low level of oxygen defects on processing allowed us to
develop a range of MLCC based on this high temperature C0G technology. Initially this work was directed at rated
voltages of ≤ 200V for use at 200
o
C but to meet the demand for pulse detonator capacitors larger, higher voltage MLCC
were subsequently developed as described below.
High Voltage High Temperature MLCC Designs
The capacitor designs developed for use at 200
o
C at rated voltages ≤ 200V use a standard overlap design as shown in the
example of a cross-section in Figure 2.
Figure 2. Cross–section 1206, 25V rated, 100nF MLCC rated for use at 200
o
C
1000010001001010.10.01
99
95
90
80
70
60
50
40
30
20
10
5
1
Final IR (MO hm)
Percent
No Re-Ox
Standard Re -Ox
Re-Ox
HALT @ 175C, 400V for 92 hours
C1206H473J5GAC