15
D
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
Solder paste with lead
Sn - Pb - Ag (Sn60-Pb40-A, Sn63-Pb37-A)
Washing
Basically, all plastic encapsuled compon-
ents, 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 interio
r
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 pro-
cess. 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
Due to the stress which the components
are subjected to during processing, rever-
sible parameter changes occur in almost
all electronic components. The capaci-
tance recovery accuracy to be expected
with careful processing is within a scope of
DC/C 5 %.
For the initial operation of the device a
minimum storage time of
t 24 hours
is to be taken into account. With cali-
brated 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-PET achieves
the best values for all fields of application.
The expected value is about:
Û0 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 ana-
logous through-hole WIMA capacitors.
Compared to ceramic or tantalum
dielectrics WIMA SMD capacitors have a
number of other outstanding qualities :
” 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 avai-
lable 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 vol-
tage and capacitance values, as well as
in telecommunications e.g. the well-known
telephone capacitor 1mF/250VDC.
11.08