IGBT (IGBT)

IGBT stands for insulated gate bipolar transistor, a hybrid power semiconductor that combines the easy gate drive of a MOSFET with the high current density of a bipolar transistor. IGBTs switch large currents (tens to thousands of amps) at moderate frequencies (1-50 kHz), making them the dominant power device in industrial inverters, three-phase motor drives, induction heating systems, welding power supplies, electric vehicle traction inverters, solar string inverters, and uninterruptible power supplies above 5 kVA.

Construction and value: A single IGBT module ranges from a small TO-247 discrete device (a few grams, costing a few hundred rupees new) to large half-bridge or six-pack power modules weighing 200-800 grams and selling new for Rs 5,000-50,000 each. The module contains a silicon IGBT die and an anti-parallel free-wheeling diode die soldered to a direct-bonded-copper (DBC) ceramic substrate, with aluminium wire bonds (rarely gold, because of high currents), copper baseplate, and an aluminium oxide or aluminium nitride ceramic insulator. The economic recovery is mainly the copper baseplate and the silver-bearing solder, but functional second-hand IGBT modules salvaged from working but obsolete inverters can be resold to the repair-shop market at 30-50% of new module price.

Where IGBTs appear in Indian e-waste: Decommissioned solar string inverters (typically 5-100 kW units installed from 2012-2018 now reaching end-of-life), traction-converter modules from Indian Railways and metro rolling stock, large UPS units from data centres, and end-of-life industrial VFDs from manufacturing facilities. Test-bench-verified working modules are a meaningful side-revenue stream for e-waste plants that invest in a power-electronics test rig (Rs 3-5 lakh investment).

Trade-offs: Recovery of IGBT modules for reuse takes 10-15 minutes of skilled labour per module compared with seconds for bulk shredding, so the economics work only if functional modules can be sold above Rs 500 each. Below that threshold, the modules are routed to bulk PCB recycling, which captures only the copper and trace silver — a typical destruction of 70-80% of the latent value.