WIMA

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

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

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 4030 5040 6054	250°C 250°C 250°C 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.