GR500 HIGH RELIABILITY SOLID TANTALUM
Introduction
The solid tantalum capacitor has become an essential device
in circuits requiring high capacitance-voltage product and
extended environmental capability. The KEMET GR500
Graded Reliability concept has made available state-of-the-
art devices providing maximum assurance of meeting sys-
tem reliability goals. All Graded Reliability capacitors
receive meticulous attention from raw material selection
through manufacture, final inspection and shipping. Having
survived a very stringent quality control program, the result-
ing capacitors meet or exceed the most critical requirements
of space, satellite, missile and medical applications where
failure is, at best, expensive, and at worst, fatal.
KEMET is, therefore, committed to the principle of the
highest possible reliability in the manufacture and grading of
its GR500 Series capacitors.
The KEMET GR500 High Reliability concept disallows
grouping of diverse ratings and production batches to deter-
mine average failure rates. Instead, data from each and every
capacitor batch are statistically fitted to determine failure
rate on the basis of 100% life testing. Each homogeneous
production batch is “gradedʼʼ as a single inspection lot, and
documented evidence of failure rate achieved is supplied
with the parts, providing assurance of the most sophisticated
and accurate reliability measurement method in the industry.
Basic Requirements
A. Manufacturing Environment —
It is of vital impor-
tance that high reliability electronic components be manu-
factured in an environment which provides commitment to
the philosophy of high reliability production. GR500 Series
capacitors are manufactured in a plant area that stresses this
philosophy. Manufacturing and quality control personnel
are selected for experience and competence. Extensive
training in quality and reliability assurance techniques is
provided, and motivation of personnel is heavily stressed.
Raw material and in-process inspection techniques are
especially rigid. The result is a capacitor product of inher-
ently superior quality.
B. Screening Test —
All GR500 Series capacitors are sub-
jected to a broad test program. Despite the most rigid of
quality control procedures, some variation among batches of
capacitors must be recognized. This fact is understandable
when one considers the inherent differences which derive
from the 16 to 1 ratio of operating voltages, the 20 to 1 ratio
of physical sizes, and the 60,000 to 1 ratio among capaci-
tance ratings. Maximum assurance of reliability is achieved
by maintaining batch identity from the raw material with
respect to capacitor sizes and ratings as well as material
identification. Each batch is then subjected to extensive,
non-destructive 100% screening tests as indicated below.
1. Thermal Shock —
Inherent variations exist among
the temperature coefficients of expansion of the various
materials required in the manufacture of solid tantalum
capacitors. In worst-case combinations, individual
capacitors will exhibit sensitivity to temperature excur-
sions. Consequently, all GR500 Series capacitors
undergo ten temperature cycles between -65°C and
+125°C prior to the electrical testing which eliminates
those capacitors failing to withstand this extreme
change in environment.
2. Surge Current —
Each GR500 capacitor receives
10 cycles @ -55°C, + 85°C. Each cycle consists of rated
voltage charge for 4±1 seconds and a discharge for 4±1
seconds. Total DC resistance (excluding the test capac-
itor) is
≤1.0
ohms. The energy storage bank capacitor(s)
is 100,000 F minimum.
3. Grading —
This term is used to describe the tech-
nique which defines the failure rate of KEMET Graded
Reliability capacitors. Grading consists of placing
GR500 capacitors in an oven at 85°C for a minimum of
250 hours at a voltage greater than rated voltage. The
technique is fundamentally based upon the oft-docu-
mented fact that solid tantalum capacitors do not con-
form to the exponential distribution of time-ordered fail-
ures, but instead exhibit a constantly decreasing failure
rate. The Weibull distribution provides a valuable tool
for describing the behavior of solid tantalum capacitors,
and experimental fits are made to this distribution in
determining performance levels for each GR500 Series
batch. Actual test data are provided with each shipment
of capacitors to document the failure rate obtained.
4. Electrical Testing —
Each GR500 Series capacitor
is tested at 25°C for leakage current at rated voltage, as
well as capacitance and dissipation factor at 120 Hz.
Since uniformity is generally a valid indicator of relia-
bility, parametric distributions are graphically recorded
for each lot. Parts which deviate from the normal popu-
lation are discarded. Guaranteed maximum values are
as detailed in Table 1.
5. ESR —
Each GR500 capacitor is tested for ESR @
100 KHz. See electrical specification tables.
6. X-ray —
Each GR500 Series capacitor is examined
by X-ray in two planes with 90 degree rotation. Since
assembly of the solid tantalum capacitor is a blind oper-
ation, optical inspection cannot reveal internal defects
such as loose solder balls or deficient anode solder
bonding.
7. Hermeticity —
Each GR500 capacitor receives her-
meticity testing per MIL-STD-202, Method 112,
Condition D. This test uses a fluorocarbon liquid at
125°C ± 5°(257°F ± 9°F) at ambient pressure and detects
gross leaks by the observation of bubbles.
C. Sampling —
In addition to the 100% screening tests,
other tests are imposed on a sample basis to determine para-
metric stability and resistance to environmental extremes.
These tests are fully described in the GR500 Graded
Reliability Specification.
D. Available Special Testing —
In addition to the standard
testing outlined in this catalog, optional testing is available.
1. 100% ESR testing at various frequencies
2. 1 KHz DF
3. Tightened DC leakage, Capacitance and Dissipation
Factor limits.
1
© KEMET Electronics Corporation • P.O. Box 5928 • Greenville, SC 29606 (864) 963-6300 • www.kemet.com
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