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FlexiCap
™
overview
FlexiCap™ termination
MLCCs are widely used in electronic circuit design for a multitude of
applications. Their small package size, technical performance and
suitability for automated assembly makes them the component of
choice for the specier.
However, despite the technical benets, ceramic components are
brittle and need careful handling on the production oor. In some
circumstances they may be prone to mechanical stress damage if
not used in an appropriate manner. Board exing, depanelisation,
mounting through hole components, poor storage and automatic
testing may all result in cracking.
Careful process control is important at all stages of circuit board
assembly and transportation - from component placement to
test and packaging. Any signicant board exing may result in
stress fractures in ceramic devices that may not always be evident
during the board assembly process. Sometimes it may be the end
customer who nds out - when equipment fails!
Knowles has the solution - FlexiCap™
FlexiCap™ has been developed as a result of listening to customers’
experiences of stress damage to MLCCs from many manufacturers,
often caused by variations in production processes.
Our answer is a proprietary exible epoxy polymer termination
material, that is applied to the device under the usual nickel barrier
nish. FlexiCap™ will accommodate a greater degree of board
bending than conventional capacitors.
Knowles FlexiCap™ termination
Ranges are available with FlexiCap™ termination material oering
increased reliability and superior mechanical performance (board
ex and temperature cycling) when compared with standard
termination materials. Refer to Knowles application note reference
AN0001. FlexiCap™ capacitors enable the board to be bent
almost twice as much before mechanical cracking occurs. Refer to
application note AN0002.
FlexiCap™ is also suitable for Space applications having passed
thermal vacuum outgassing tests. Refer to Syfer application note
reference AN0026.
Fired ceramic
dielectric
Tin outer
layer
Metal
electrodes
FlexiCap™ MLCC cross section
termination
base
Intermediate nickel
or copper layer
Application notes
FlexiCap™ may be handled, stored and transported in the same
manner as standard terminated capacitors. The requirements for
mounting and soldering FlexiCap™ are the same as for standard
SMD capacitors.
For customers currently using standard terminated capacitors there
should be no requirement to change the assembly process when
converting to FlexiCap™.
Based upon board bend tests in accordance with IEC 60384-1
the amount of board bending required to mechanically crack a
FlexiCap™ terminated capacitor is signicantly increased compared
with standard terminated capacitors.
It must be stressed however, that capacitor users must not
assume that the use of FlexiCap™ terminated capacitors will totally
eliminate mechanical cracking. Good process controls are still
required for this objective to be achieved.
● Picture taken at 1,000x
magnification using a SEM
to demonstrate the fibrous
nature of the FlexiCap
TM
termination that absorbs
increased levels of
mechanical stress.
Available on the following ranges:
● All High Reliability ranges
● Standard and High Voltage Capacitors
● Open Mode and Tandem Capacitors
● Safety Certied Capacitors
● Non-magnetic Capacitors
● 3 terminal EMI chips
● X2Y Integrated Passive Components
● X8R High Temperature capacitors
Summary of PCB bend test results
The bend tests conducted on X7R have proven that the FlexiCap™
termination withstands a greater level of mechanical stress before
mechanical cracking occurs.
The AEC-Q200 test for X7R requires a bend level of 2mm minimum
and a cap change of less than 10%.
Product
X7R
Typical bend performance under
AEC-Q200 test conditions
Standard termination 2mm to 3mm
FlexiCap™ Typically 8mm to 10mm
FlexiCap™ benets
With traditional termination materials and assembly, the chain
of materials from bare PCB to soldered termination, provides no
exibility. In circumstances where excessive stress is applied - the
weakest link fails. This means the ceramic itself, which may fail
short circuit.
The benet to the user is to facilitate a wider process window -
giving a greater safety margin and substantially reducing the typical
root causes of mechanical stress cracking.
FlexiCap™ may be soldered using your traditional wave or reow
solder techniques including lead free and needs no adjustment to
equipment or current processes.
Knowles has delivered millions of FlexiCap™ components and
during that time has collected substantial test and reliability data,
working in partnership with customers world wide, to eliminate
mechanical cracking.
An additional benet of FlexiCap™ is that MLCCs can withstand
temperature cycling -55ºC to 125ºC in excess of 1,000 times
without cracking.
FlexiCap™ termination has no adverse eect on any electrical
parameters, nor aects the operation of the MLCC in any way.
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Production process owchart Knowles reliability grades
DPA inspection
Rumble
Multilayer build
Fire
Ceramic powder
preparation
Electrode ink
material
Termination
Electrical test
Test verification
Packaging
Finished goods store
Plating
(if specified)
QC inspection
Additional Hi Rel
activities
(S02A 100% burn-in, QC insp)
Additional sample
Rel tests
(if specified)
Printing
(if specified)
Standard components
IECQ-CECC
(2)
AEC-Q200
(3)
Space
Grade
ESCC 3009
(1)
MIL Grade
Standard
reliability
High reliability
(space quality)
Knowles reliability surface mount product groups
Standard FlexiCap
TM
capacitors
(3)
Open Mode
FlexiCap
TM
capacitors
(2)
Tandem
FlexiCap
TM
capacitors
(1)
Standard
reliability
High reliability
Standard MLC capacitors
(4)
Notes:
1) “Tandem” construction capacitors, ie internally having the equivalent
of 2 series capacitors. If one of these should fail short-circuit, there is still
capacitance end to end and the chip will still function as a capacitor,
although capacitance maybe aected. Refer to application note AN0021.
Also available qualied to AEC-Q200.
2) “Open Mode” capacitors with FlexiCap
TM
termination also reduce the
possibility of a short circuit by utilising inset electrode margins. Refer to
application note AN0022. Also available qualied to AEC-Q200.
3) Multilayer capacitors with Knowles FlexiCap
TM
termination. By using
FlexiCap
TM
termination, there is a reduced possibility of the mechanical
cracking occurring.
4) “Standard” capacitors includes MLCCs with tin nish over nickel but no
FlexiCap
TM
.
Notes:
1) Space grade tested in accordance with ESCC3009 (refer to Knowles
Spec S02A 0100) or MIL Grade (in accordance with MIL-PRF-123, MIL-
PRF-55681).
2) IECQ-CECC. The International Electrotechnical Commission (IEC) Quality
Assessment System for Electronic Components. This is an internationally
recognised product quality certication which provides customers with
assurance that the product supplied meets high quality standards.
View Knowles IECQ-CECC approvals at http://www.iecq.org or at
www.knowlescapacitors.com
3) AEC-Q200. Automotive Electronics Council Stress Test Qualication
For Passive Components. Refer to Knowles application note reference
AN0009.
Manufacturing processes
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