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.
Table of Contents:
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.
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:
- Composition of lead-free cored solder wire for hand-soldering
- Composition of solder bar for wave soldering, solder paste for reflow and hot air soldering and BGA Balls
- Chemistry of flux to be used in lead-free soldering
- Temperature resistance and tolerance of led-free compatible electronic components
Best & Popular Lead Free Solder Composition
- Lead Free Solder Wire – Sn96.5/Ag3.0/Cu0.5
- Lead-Free Solder Bar- Sn99.3/Cu0.7
- 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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