Principle Metals in Solders Alloys

ELEMENT

INFORMATION

MP ºC

S.G.

TIN (Sn)

THE BEST WETTING OF THE SOFT SOLDER ALLOYS CONSTITUENTS, IT IS AN AGGRESSIVE ELEMENT THAT DISSOLVES MOST METALS IT COMES IN CONTACT WITH DURING SOLDERING. TIN IS ALSO SOLUBLE IN MOST OTHER LOW MELTING METALS AND FORMS AN APHA AND BETA METAL PHASES. IN THE ALPHA PHASE THE OTHER METAL IS DISSOLVED IN THE TIN AND IN THE BETA PHASE THE TIN IS DISSOLVED IN THE OTHER METAL.

 

232

 

7.29

LEAD (Pb)

LEAD IS A FILLER METAL THAT HAS VERY LITTLE WETTING ON ITS OWN. WHEN ALLOYED WITH A MORE AGGRESSIVE METAL IT CREATES A USEABLE, MORE MALLEABLE ALLOY.

328

11.35

ANTIMONY.(Sb)

ANTIMONY IS NORMALLY USED AS A HARDENING AGENT. DUE TO IT’S HIGH RATE OF OXIDATION, IT INHIBITS WETTING BY CHANGING SURFACE TENSIONS OF THE SOLDER.

631

6.69

COPPER.(Cu)

NORMALLY NOT ALLOWED WITH LEADED SOLDERS; WILL DECREASE TINS AGGRESSIVENESS TOWARD SOLDERING IRON TIPS. WIDLY USED IN LF SOLDERS FOR DUCTILITY

1083

8.96

BISMUTH.(Bi)

USED TO LOWER THE MELTING POINT OF SOLDER ALLOYS, IT IS MAINLY USED IN FUSIBLE ALLOYS. DUE TO IT’S HIGH OXIDATION RATE IT WILL INHIBIT WETTING.

271

9.80

GALLIUM.(Ga)

A LOW MELTING ELEMENT USED TO LOWER THE MELTING POINT AND IMPROVE ALLOYING. BENEFICIAL FOR HEAT TRANSFER OR WHERE LIQUID SWITCHES ARE USED.

30

5.90

GERANIUM.(Ge)

NORMALLY ALLOYED WITH GOLD, IT’S USED AS A SOLDER FOR BONDING TO GERANIUM DEVICES. ALSO IMPROVES GRAIN STRUCTURE

937

5.32

GOLD.(Au)

USED WHERE HIGH SURFACE SIGNALS OR HIGH CORROSION RESISTANCE IS NEEDED. ALSO USED FOR SOLDERING TO GOLD IN HIGH RELIABILITY DEVICES

1063

19.30

INDIUM.(In)

USEFUL WHEN A VARIETY OF TEMPERATURE ALLOYS ARE NEEDED OR WHERE THERMAL MISMATCHES OF COMPONENTS CAUSE JOINT FAILURE. ALSO USED ON SOLDERING TO GOLD BY REPLACING TIN IN THE ALLOY. WHEN USING INDIUM, IT SHOULD BE COATED OR SEALED IF POSSIBLE.

156

7.31

CADMIUM.(Cd)

LOWERS THE MELTING POINT OF FUSIBLE ALLOYS AND ALSO USED FOR EMF CIRCUITS.

321

8.64

SILVER.(Ag)

USED TO REDUCE SILVER SCAVENGING ON SILVER THICK FILM CIRCUITS. SLIGHTLY INHIBITS WETTING. IMPROVES LF ALLOYS MECHANICAL STRENTGH

961

10.53

ZINC.(Zn)

NOT NORMALLY USED IN SOLDERS, EXCEPT TO SOLDER TO ALUMINIUM. ALSO USED IN CASTING ALLOYS TO INCREASE STRENGTH AND REDUCE COST.

419

7.14

 

* These are only indicative values and should be correctly calculated, when used in any design or application.