|
Layout
Form
The components can
generally be positioned on the carrier material as desired. In
order to prevent soldering shadows or ensure regular
temperature distribution, extreme concentration of the
components should be avoided. In practice, it has proven best
to keep a minimum distance of the soldering surfaces between
two WIMA SMDs of twice the height of the components.
As a
basic principle for wave soldering, alignment of the soldering
surfaces in accordance with the transport direction of the
printed circuit board through the soldering wave is
recommended.
. |
|
Solder Pad
Recommendation
 |
| Size
code |
L
±0.3 |
W
±0.3 |
d |
a
min. |
b
min. |
c
max. |
|
1812
2220
2824
4030
5040
6054 |
4.8
5.7
7.2
10.2
12.7
15.3 |
3.3
5.1
6.1
7.6
10.2
13.7 |
0.5
0.5
0.5
0.5
0.7
0.7 |
1.2
1.2
1.2
2.5
2.5
2.5 |
3.5
4
4
6
6
6 |
3.5
4.5
6.5
9
11.5
14 | |
|
The solder pad size recommendations given
for each individual series (see SMD series concerned) are to
be understood as minimum dimensions which can at any time be
adjusted to the layout form.
. |
Processing
The processing of SMD components
- assembling
- soldering
- washing
-
electrical final inspection / calibrating
must
be regarded as a complete process. The soldering of the
printed circuit board, for example, can constitute
considerable stress on all the electronic components.
The
manufacturer's instructions on the processing of the
components are mandatory.
. |
Soldering
Process
|
Re-flow
soldering
 |
|
SMD-PET
|
| Size code |
Tmax. |
1812
2220
2824
4030
5040
6054 |
220°C
230°C
230°C
230°C
240°C
250°C | |
|
 |
| SMD-PEN |
| Size code |
Tmax. |
1812
2220
2824
4030
5040
6054 |
220°C
230°C
230°C
230°C
240°C
250°C | |
| SMD-PPS |
| Size code |
Tmax. |
1812
2220
2824
-
-
- |
250°C
250°C
250°C
-
-
- | |
| Temperature/time
graph for the permissible processing temperature
of the WIMA SMD film capacitors for typical
convection soldering
processes. | |
Due to the diverse procedures and the
varying heat requirements of the different types of
components, an exact processing temperature for re-flow
soldering processes cannot be specified. The graph shows the
upper limits of temperature and time which must not be
exceeded when establishing the solder profile according to
your actual requirements.
A max. temperature of T=210°C inside the
component should not be exceeded when processing WIMA SMD
capacitors.
. |
SMD
Handsoldering
WIMA SMD
capacitors with plastic film dielectric are generally suitable
for hand-soldering with a soldering iron where, however,
similar to automated soldering processes, a certain duration
and temperature should not be exceeded. These parameters are
dependent on the physical size of the components and the
relevant heat absorption involved.
|
| Size
code |
Temperature
°C/°F |
Time
duration |
1812
2220
2824
4030
5040
6054 |
225/437
225/437
250/482
260/500
260/500
260/500 |
2 sec
plate 1 / 5 sec off / 2 sec plate 2
3 sec plate 1 / 5
sec off / 3 sec plate 2
3 sec plate 1 / 5 sec off / 3
sec plate 2
5 sec plate 1 / 5 sec off / 5 sec plate
2
5 sec plate 1 / 5 sec off / 5 sec plate 2
5 sec
plate 1 / 5 sec off / 5 sec plate
2 | |
|
The above data are to be regarded as guideline values
and should serve to avoid damage to the dielectric
caused by excessive heat during the soldering process.
The soldering quality depends on the tool used and on
the skill and experience of the person with the
soldering iron in hand.
. | |
Solder
Paste
To obtain the best soldering performance we suggest
the use of following solder paste alloy:
Lead-free solder paste
Sn
-Bi
Sn - Zn (Bi)
Sn - Ag - Cu
(recommended)
Solder
paste with lead
Sn - Pb - Ag (Sn60-Pb40-A,
Sn63-Pb37-A)
. |
Washing
Basically, all plastic
encapsuled components, irrespective of the brand cannot be
considered as being hermetically sealed. They are therefore
only suitable for industrial washing processes to a limited
extent.
During the washing process, washing agents can
penetrate the interior of the component by capillary action
through microcracks which might have occured.
This is
dependent on a number of parameters e.g.
- washing agents
- viscosity of the
washing solvent
- temperature/time of the washing
process
- mechanical washing aids such
as
- ultrasonic
- water pressure
- rinsing and spraying
pressure
The type of washing
agent to be used is largely specific to the individual user or
is often laid down by the manufacturer of the washing
equipment. The agressiveness of the washing agent to be used
can thus only be judged in appropriate test series relating to
each individual washing process. By and large, the basic rule
is that the washing process should be carried out as gently as
possible.
. |
Drying
During the washing process, aqueous
solutions can penetrate the component. This can lead to
changes in the electrical parameters. Suitable drying measures
should ensure that no residual moisture or traces of washing
substances are left in the component.
. |
Initial
Operation / Calibration of the Device
Due to the stress which the
components are subjected to during processing, reversible
parameter changes occur in almost all electronic components.
The capacitance recovery accuracy to be expected with careful
processing is within a scope of
| C/C| < 5%
For the initial operation
of the device a minimum storage time of
t >
24 hours
is to be taken into
account. With calibrated devices or when the application is
largely dependent on capacitance it is advisable to prolong
the storage time to
t > 10 days
In
this way ageing effects of the capacitor structure can be
anticipated. Parameter changes due to processing are not to be
expected after this period of time.
. |
Humidity
Protection Bags
Taped
WIMA SMD capacitors are shipped in humidity protection bags
according to JEDEC standard, level 1 (EMI/static-shielding
bags conforming to MIL-B 81705, Type 1, Class 1).
Under
controlled conditions the components can be stored two years
and more in the originally sealed bag. Opened packing units
should be consumed instantly or resealed for specific storage
under controlled conditions.
. |
Reliability
Taking account of the manufacturer's guidelines and
compatible processing, the WIMA SMD stand out for the same
high quality
and reliability as the analogous through-hole WIMA series.
The technology of metallized film capacitors used e.g. in WIMA
SMD achieves the best values for all fields of
application.
The expected value is
about:
 < 2
fit
Furthermore the production
of all WIMA components is subject to the regulations laid down
by ISO 9001:2000
as well as the guidelines for component specifications set
out by IEC quality assessment system (IECQ-CECC) for
electronic components.
. |
Electrical
Characteristics and Fields of Application
Basically the WIMA SMD series have the same
electrical characteristics as the analogous through-hole WIMA
capacitors.
Apart from the advantages shown in the diagrams
of the electrical
parameters in comparison with X7R ceramic and tantalum
capacitors, WIMA SMD capacitors have a number of other
outstanding qualities compared to ceramic or tantalum
dielectrics:
favourable pulse rise time
low ESR
low
dielectric
absorption
available in high
voltage series
large capacitance
spectrum
stand up to high mechanical stress
good long-term
stability
As regards technical performance
as well as quality and reliability, the WIMA SMD series offer
the possibility to cover nearly all applications of
conventionally through-hole film capacitors with SMD
components. Furthermore, the WIMA SMD series can now be used
for all the demanding capacitor applications for which, in the
past, the use of through-hole components was
mandatory:
measuring
techniques
oscillator circuits
differentiating and
integrating circuits
A/D or D/A
transformers
sample and hold circuits
automotive
electronics
With the
WIMA SMD programme available today, the major part of all
plastic film capacitors can be replaced by WIMA SMD
components. The field of application ranges from standard
coupling capacitors to use in switch-mode power supplies as
filter or charging capacitors with high voltage and
capacitance values, as well as in telecommunications e.g. the
well-known telephone capacitor
1μF/250VDC. |
