Datasheet

STANNOL GmbH
Oskarstraße 3-7 42283 Wuppertal Tel. [phone] Telefax 0202-585111 E-Mail [e-mail]
Technical Data Sheet
STANNOL
®
Liquid Flux WF305F & WF305S
No-Clean No VOC
STANNOL
®
WF305F and WF305S are low residue, resin and halide free fluxes which meet the most demanding
legislation on volatile organic compound (VOC) emission during use.
- Suitable for clean copper or tin/lead substrate - Residues may be washed in water if required
- <1% VOC - meets air quality legislation - Non-flammable formulation
- Suitable for wave, spray and foam application - No Clean
APPLICATIONS
Recommended for consumer electronics, telecommuni-cations and for professional applications using conventional wave
soldering machines or units with nitrogen inerted waves. However, if there is a need for a wider process window (e.g. if the PCB
has been poorly preserved and/or exhibits very low solderability), the next generation of fluxes, NR3F-06 and NR3S-06, should
be recommended.
RECOMMENDED OPERATING CONDITIONS
The Printed Circuit Board: STANNOL
®
WF305F and WF305S are designed for optimum wetting of surfaces and are not
aggressive towards common plastics.
STANNOL
®
WF305F and WF305S have been formulated for high activity on clean copper and are effective on tin/lead coated
boards.
Machine Preparation: When switching to WF305F or WF305S from any other flux, ensure all fingers, pallets and conveyors
are thoroughly cleaned. lt is recommended that
STANNOL
®
Flux-Ex 500
be used in the finger cleaners.
Fluxing: STANNOL
®
WF305S
has been formulated for use in
spray
or
wave fluxers
in the same way as ordinary fluxes on
standard wave soldering machines.
WF305F
has been formulated for use in
foam fluxers.
The upper limit for flux coverage to ensure that soldered PCBs pass cleanliness tests is 40g m
-2
of circuit. Good soldering can
be achieved at half this volume.
STANNOL
®
WF305F and WF305S
mimics the foaming properties of conventional low solids liquid fluxes. However, as it is
water based, the foam is less prone to destabilisation through evaporative loss and contact with hot fixtures or pallets. There is
no requirement for the air to be dry.
Observing the following instructions will help ensure optimum foaming and soldering results.
1. Keep the flux tank FULL at all times.
2. The top of the foaming stone should be no more than 20mm below the surface of the liquid flux and if necessary the level
of the stone should be raised.
3. The ideal feed gas flow rate (pressure) is below that typically used for conventional solvent liquid fluxes and the preferred
width of the slot (opening) of the foam fluxer is greater (10-20mm). It is preferable to have a chimney for the foam which
tapers towards the top.
4. DO NOT use fixtures which have the potential to entrap flux.
lt is important to remove excess flux from the circuit boards using the standard air knife or brushes supplied on the wave
soldering machine. An air pressure of about 5 - 7psi is recommended and the nozzle should be about 25mm below the board
and angled back at a few degrees to the perpendicular to the plane of the board. This will ensure effective removal of excess
flux without transferring droplets to the top of the following board. Sufficient space should be allowed between the foam fluxer
and the air knife to prevent the air stream disturbing the foam.
Flux Control:
Since loss of solvent by evaporation is slow and moisture absorption does not occur, flux maintenance is simpler
than for alcohol formulations. Density measurements do not give a reliable guide to flux activity since changes are small and
difficult to detect. The
STANNOL
®
titration kit
is recommended for routine control at the production line.
STANNOL
®
WF305F and WF305S should not be stored below 0°C since they are liable to freezing. Cold temperatures (<10°C)
may cause separation.
Crystallised solids will re-enter solution with agitation at room temperature.
Preheating: As WF305F and WF305S contain significant quantities of water, it will be necessary to adjust the preheater setting
to remove the solvent and to ensure that the flux is properly activated. The optimum preheat temperature and time for a PCB
depends on its design and the thermal mass of the components but the cycle should be sufficient to ensure that the flux coating
is not visibly wet when it contacts the wave. A combination which has given good results is shown below.
Conveyor speed
ft min
-1
/ m min
-1
4.9 / 1.5
Topside preheat
°C / °F 110 / 230
lt is advantageous to fit a topside canopy over the preheaters to produce more effective drying and activation. This will allow the
use of faster conveyor speeds and improve soldering. At a speed of 1.5m min
-1
, a contact length of 38-50mm between the wave
and the PCB is recommended. At lower speeds, this contact length should be reduced. Very slow speeds through the solder
wave may produce dull solder joints. lt is particularly useful when setting up a machine to measure the preheat using the
STANNOL
®
SoldaPro Temperature Profile System (data sheet available).
Wenn’s ums Löten geht
When it’s about soldering
Quand il s’agit du soudage