Kester 951 is a halogen-free, non-rosin
organic flux designed for wave soldering conventional and surface mount circuit
board assemblies. The extremely low solids content (2.0%) and nature of the
activator system results in practically NO RESIDUE left on the assembly after
soldering. Boards are dry and cosmetically clean as they exit the wave solder
machine. There are no residues to interfere with electrical testing. Kester 951
exhibits improved soldering performance to minimize solder bridges (shorts) and
excessive solder defects. This flux is suitable for automotive, computer,
telecommunications and other applications where reliability considerations are critical.
The surface insulation resistance on soldered boards is higher than that provided
by typical organic water-soluble fluxes. Kester 951 contains a corrosion
inhibitor such that no corrosion products are formed when bare copper surfaces
are exposed to humid environments.
Performance
Characteristics:
• Improves soldering performance
• Eliminates the need and expense of
cleaning
• Non-corrosive tack-free residues
• Classified as ORL0 per J-STD-004
•
Compliant to Bellcore GR-78
Application Notes
Flux Application:
Kester 951 can be applied to
circuit boards by a spray, foam or dip process. Flux deposition should be 120-240
mg of solids/cm2 (750-1500 mg of
solids/in2). An air knife after the flux tank is recommended to remove
excess flux from the circuit board and prevent dripping on the preheater
surface.
Process Considerations:
The optimum preheat
temperature for most circuit assemblies is 93-110°C (200-230°F) as measured on
the top or component side of the printed circuit board. Dwell time in the wave
is typically 2-4 seconds. The wave soldering speed should be adjusted to
accomplish proper preheating and evaporate excess solvent, which could cause
spattering. For best results, speeds of 1.1-1.8 m/min (3½-6 ft/min) are used.
The surface tension has been adjusted to help the flux form a thin film on the
board surface allowing rapid solvent evaporation.
Flux Control:
Acid number is normally the
most reliable method to control the flux concentration of low solids, no-clean fluxes.
To check concentration, a simple acid-base titration should be used. PS-22 Test
Kit and procedure are available from Kester. Control of the flux in the foam
flux tank during use is necessary for assurance of consistent flux distribution
on the circuit boards. The complex nature of the solvent system for the flux
makes it imperative that Kester 110 Thinner be used to replace evaporative
losses. When excessive debris from circuit boards, such as board fibers and
from the air line build up in the flux tank, these particulates will redeposit on
the circuit boards which may create a build up of residues on probe test pins.
It is, therefore, necessary to clean the tank and then replenish it with fresh
flux when excessive debris accumulates in the flux tank.
Cleaning:
Kester 951 flux residues are
non-conductive, non-corrosive and do not require removal in most applications.
Storage and Shelf Life:
Kester 951 is flammable.
Store away from sources of ignition. Shelf life is 1 year from date of
manufacture when handled properly and held at 10-25°C (50-77°F).
Health & Safety:
This product, during handling
or use, may be hazardous to health or the environment. Read the Material Safety
Data Sheet and warning label before using this product.
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