Obsolete semiconductors do not disappear from service boards when the factory stops making them. Maintenance teams, aerospace programs, and industrial controls still need those exact MPNs — often years after the original distributor delisted them.
Search the exact MPN first
Start with the full manufacturer part number including package suffix. USParts.us indexes supplier listings by MPN and matches common variants so LM358, LM358N, and related lines surface together when suppliers published them.
If the exact suffix is unavailable, review cross-reference datasheets internally before substituting — marketplace search shows what exists, not what is electrically equivalent.
Look for surplus inventory, not just franchised stock
Obsolete parts often live in excess inventory at independent distributors, contract manufacturers, and asset recovery firms. Those sellers list surplus on marketplaces because franchised channels no longer carry the line.
Free electronics marketplaces aggregate that fragmented supply so you are not calling ten warehouses for one BOM.
Use quotes when price is not published
Legacy or scarce lines frequently show as price on request. Submit a quote request with quantity and needed date code range. Suppliers with stock can respond with formal offers without you committing to buy through an anonymous form.
Document sources for quality-sensitive programs
For regulated industries, keep traceability on date code, condition, and supplier identity. Marketplace listings show supplier company names so your quality team can approve vendors before purchase.
Ready to search or list parts?
Use free BOM search to source components, or list your surplus inventory so buyers can find your MPNs on USParts.us.