Flux Faqs
Q.1. What is the difference between the standard
brazing fluxes and the fluoride-free brazing flux ?
Ans. The fluoride free brazing fluxes don't contain fluorides while
traditional brazing fluxes are formulated containing different chemicals
with fluorides. Fluorides are added to remove oxides from the metal surfaces
and allow the filler metals to flow consistently and efficiently.
Fluoride-free fluxes use a different method to remove oxides layers from the
base metals.
Q.2. Are water soluble fluxes reliable for
producing high quality electronics?
Ans. Water soluble fluxes are good for producing high quality
electronics. Manufacturers have been using these fluxes for a long time.
Moving away from rosin fluxes and freon cleaning did a great deal to spur
this activity. It should be intelligently used and must have a good cleaning
process associated with it.
Q.3. Mention the dangers associated with water
soluble fluxes.
Ans. Water soluble fluxes are very aggressive in their ability to
strip oxides. The activators used in the flus determines the degree of
aggressiveness. It acts like a corrosive material and does not know when to
stop stripping oxide. Another disadvantage is that if you don’t clean
the flux residues off, it will continue to erode the base metal. Apart from
that, metal migration and electrical leakage currents are also common
failures with incomplete removal of water soluble fluxes.
Q.4. How do I know what flux to use?
Ans. The primary function of flux is to prevent the base metal from
oxidizing during brazing and promoting capillary action for the filler
metal. As the alloy begins to melt the flux should be in the fluid state at
that time and remain in the same state until the brazing process is
completed. The melting temperature of different alloys vary and so the
choice of flux should be. In selection of brazing flux, temperature and
brazing time are the two important factors to consider.
Q.5. What amount of flux should be put on the
joint?
Ans. The amount of flux should be enough so that during brazing the
metal didn't burn off. Flux prevents the metal from oxidization so it should
be there during the brazing. Excess flux isn't also good because it will
cause pinholes and not allow the alloy to flow properly.
Q.6. What is Flux?
Ans. Flux is a chemical compound, which is used during the different
metal joining processes. Its main function is to protect the joint surface
from air and prevents oxide formation. In this way it helps the capillary
action to occur efficiently and in making stronger joints.
Q.7. In what forms fluxes are available?
Ans. Fluxes are available in paste, liquid, powder, and slurry form
depending on the type of flux. Liquid, Paste, and slurry fluxes are all
water based while the dispensable fluxes are petroleum based.
Q.8. How fluxes are cleaned off of joint after
brazing?
Ans. The easiest way to clean off the flux of brazed joint is to
quench and soak the assembly in hot water. Hydrochloric acid (up to 25%) can
be used to add to the water for stubborn flux residue. If required some
special cleaners can also be used.
Q.9. What is brazing paste?
Ans. Brazing paste is a chemical compound consisting of metal alloy
in powder form mixed with a binder. When required, it is mixed with flux to
provide protection from oxidization.
Q.10. How alloys are selected for brazing the
metals?
Ans. The alloys used for brazing are also called filler metals. The
alloys should be metallurgically compatible with the metals to be joined.
Brazing two dissimilar metals require a filler metal which could prevent
interface corrosion.
Air
Condition/Refrigerator
