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Lead Free Solder and Composition | Pb-Free Solder

Lead Free Solder and Composition Differ from Leaded Solder Composition. Tip (Sn) is Present in Both Lead Free and Leaded Solder but Lead (Pb) is Not Present in Lead-Free Solder.

Lead free solder composition is different from composition of leaded solder. There is NO Lead (Pb) is Lead Free solder. Lead Free Solder is taking rapid momentum around the world after the EU (European Union) Directives to wipe off lead (Poison) from electronic soldering considering its health and environmental effects.

Terms to Know when Understanding Lead Free Solder Composition

RoHS: Restriction of Hazardous Substances [ lead (Pb), mercury (Hg), cadmium (Cd), hexavalent chromium (CrVI), polybrominated biphenyls (PBB) and polybrominated diphenyl ethers (PBDE).]

WEEE: Waste from Electrical and Electronic Equipments.

Lead Free Solder

Lead Free Solder

Why Lead Free in Electronics

Many of the electronic companies and manufacturers around the globe were using Tin-Lead (Sn/Pb) solder (Solder Wire, Solder Bar, Solder Paste) for PCB assembly and rework / repairing. They also used No-Clean Liquid Flux and No-Clean Solder Paste. They did not bother to clean the PCB and the flux residue after assembly. These boards were later dumped into earth.

While Pb is dangerous and harmful during the assembly process, dumping the board in soil was harmful to the environment. This ultimately lead to make lead-free PCB assembly mandatory.

Video: Types of Solder Wire

Lead Free Solder and Composition

Various Chemistry for alloy composition in Pb-free solder was explored. Several things had to be kept in mind:

Best & Popular Lead Free Solder Composition

  1. Lead Free Solder Wire – Sn96.5/Ag3.0/Cu0.5
  2. Lead-Free Solder Bar- Sn99.3/Cu0.7
  3. Lead-Free Solder Paste – Sn96.5/Ag3.0/Cu0.5

Other Less Popular Pb-Free Solder Composition

COMPOSITION MELTING POINT
96.5% Sn/3% Ag/0.5% Cu 217°C
95.5% Sn/3.8% Ag/0.7% Cu 217°C
93.5% Sn/3% Sb/2% Bi/1.5% Cu 218°C
95.5% Sn/3.5% Ag/1% Zn 218°C – 221°C
96.5% Sn/3.5% Ag 221°C
95% Sn/5% Ag 221°C – 240°C
96% Sn/4% Ag 221°C
97.5% Sn/2.5% Ag 221°C – 226°C
97% Sn/2% Cu/0.8% Sb/0.2% Ag 226°C – 228°C
99.3% Sn/0.7% Cu 227°C
97% Sn/3% Cu 227°C – 300°C
95% Sn/5% Sb 232°C – 240°C
65% Sn/25% Ag/10% Sb 233°C
96% Sn/4% Cu 235°C
42% Sn/58% Bi 138°C
91% Sn/9% Zn 199°C
  • Flux – Flux used in lead-free soldering has to be more active to withstand the high temperature.

Alpha Cookson is one of the leading and trusted manufacturers and suppliers of both Lead-Free and Leaded Solder Wire, Paste and Bar.

Lead-Free Solder Composition with High Temperature Melting Point

Metal / Alloy (%)

Melting Point

Use / Application

Sn

Ag

Sb

Au

Bi

Ge

Solidus

Liquidus

Lower Tj IGBT usage

96.5

3.5

221°C

Eutectic

Also known as “J-alloy”

65

25

10

233°C

Eutectic

Generally Used in step-soldering processes

95

5

237°C

240°C

Highest Sb content possible in standard Sn/Sb wire

91.5

8.5

241°C

248°C

Generally Used in step-soldering processes

90

10

243°C

257°C

Highest melting standard Sn/Sb alloy

86

14

Very poor solderability

11

89

262°C

360°C

Very high tensile strength and thermal / electrical conductivity

20

80

280°C

Eutectic

Usable for very high Tj die-attach like SiC

88

12

356°C

Eutectic

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Santosh Das

Santosh, founder of this Electronics Tutorial Website, is an Electronics Geek, Blogger and Young Entrepreneur. He possesses vast experience in the field of electronics, electronic components, PCB, Soldering, SMT, Telecommunication, ESD Safety, and PCB Assembly Tools, Equipment and Consumables. Keep visiting for daily dose of Tips and Tutorials.

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29 Responses

  1. Advance Tech says:

    Great content.Thanks for sharing this fruitful content.

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