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Soldering Definition

Uses

Ideal requirements

Properties

Composition

Classification

Procedures

If solder joint done properly there should be nofusion or alteration of the two components joined. Fusion welding is the process whereby thepieces that are joined are melted or fused togetherwithout solder (filler).

Prerequisites of soldering To achieve Bonding Cleanliness Wetting of the surfaces

Ideal requirements of dental solder Ability to resist tarnish and corrosion.

Fusion temperature 100-150F (60C) below thatof the parts to be joined.

To be free flowing when melted.

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Resistance to pitting.

At least as strong as the parts being joined.

Color compatible with parts to be joined.

Properties Fusion Temperature. Strength Resistance to tarnish and corrosion. Solder gap. Free flowing.

Classification of Gold Solder Fineness Carat Fusion Temperature

Carat

It is the amount of gold in parts per 24.

an alloy that is 18 K is 18 parts gold per 24(18/24) = 75% gold .

FLUX Is placed on the surfaces to be soldered before they areheated.

Added to the metal surface to improve solder flow,

prevent oxidation (actually flux dissolves oxides),

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prevent contamination.

Oxidation of metal surfaces during solderingprocedures can prevent both flow and wetting of solder.

FLUX

1st, displaces gases and removes oxidesfrom surface by reduction or dissolution 2nd, is displaced by the solder

FLUX Borax, Boric Acid, Silica, or Sodium tetraborate

Used with noble alloys (gold alloys for crown andbridge and ceramo-metal alloys).

Fluoride Fluxes are need for Chrome-Nickelmetals (base metal alloys) since Borax based fluxdoes not dissolve chromium oxide.

Anti-Flux A material used to outline the area tobe soldered in order to restrict the flowof solder (limit spreading of solder).

Placed on casting before flux application.

Most common types: Soft graphite pencil

Polishing rouge (Iron Oxide)

Whiting compound (a calcium basedcompound).

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Soldering Procedure Indexing Investing

Soldering

Pre-soldering Preveneer soldering.

Refers to soldering the metal framework before theaddition of porcelain.

A high fusing solder (1100C) is used because thesolder joint must withstand subsequent heating during theaddition and firing of porcelain.

Post-soldering Refers to soldering after the porcelain is added. A low fusing solder is used because soldering must bedone at a lower temperature than the maturation of

porcelain. All staining and glazing of ceramic units must be doneprior to soldering. The porcelain should not contact the investment or flux,and the units should not be quenched.

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3. Make soldering index :fast-setting impression plaster in

impression carrying tray or tonguedepressor.

4. Make soldering block:Box index and pour soldering investmentTrim to uniform shape and notch solderingblock ,

Flush boiling water,Place flux and antiflux

REPAIRING CASTING VOIDS

Solder cannot be used to repair deficientmargins or occlusal holes. CAN be used to repair PITS and HOLES in axialsurfaces. Platinum foil over hole on inside of casting: actsas matrix for solder.