Lead-Free (Pb-Free) Solder and Composition
Lead-Free Solder: Solder with NO Lead (Pb). Lead-Free 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
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 for PCB assembly and rework. 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 lead 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.
Various Chemistry for alloy composition in lead-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
Composition of solder paste for reflow and hot air soldering
Composition of BGA Balls
Chemistry of flux to be used in lead-free soldering
Temperature resistance and tolerance of led-free compatible electronic components
The best composition of solder as per the experts are:
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
Flux – Flux used in lead-free soldering has to be more active to withstand the high temperature.