Polyimide vs PET flex circuits — why one survives a soldering iron and one melts

Polyimide film, usually amber or orange, is rated for continuous high temperatures and briefly survives soldering. PET (polyester) film, common in cheaper membrane-style circuits with printed silver ink traces, softens well below soldering temperature.

Why it matters

Touch an iron to a PET circuit with silver-ink traces and the film shrivels and the trace is gone. Those circuits are repaired cold — conductive silver epoxy or ink, mechanical clamping, and careful curing — never with a hot iron.

Quick identification

• Amber, flexible, copper traces visible: likely polyimide — careful low-mass soldering possible.
• Clear/white/grey film with dull grey or silver printed traces: likely PET with silver ink — cold repair only.
• When in doubt, test heat on an unused tab edge, never on a live trace.