Medical, food contact and semiconductor packaging injection molding are completed in Class 10000/Class 100 cleanrooms, with strict restrictions on dust shedding, metal particle precipitation, volatile organic compounds and surface contamination. Conventional industrial thermocouples contain unpolished metal burrs, oil-containing mineral filling, fiber shedding insulation and easily oxidized loose springs, which will pollute cleanroom melt and fail hygiene inspections. Cleanroom dedicated thermocouples implement full-process pollution-free design from raw material selection to finished product packaging, with five mandatory special technical standards that cannot be simplified.
First, oil-free full-sealed mineral insulation filling standard. Ordinary industrial thermocouples add mineral oil lubricant during wire drawing and magnesium oxide compaction, which volatilizes into cleanroom melt under high temperature and produces toxic organic residues. Cleanroom thermocouples cancel all oil lubricants, adopting high-purity calcined food-grade magnesium oxide powder for vacuum compaction filling. The hot junction welding point uses fully sealed vacuum encapsulation, isolating internal alloy wires and filling powder from contact with external plastic melt to prevent powder leakage and metal particle shedding from welding gaps. Even if the sheath surface is slightly scratched, internal filling materials will not contaminate the clean production environment.
Second, mirror passivated anti-precipitation metal sheath treatment. The probe sheath uses 316L or Hastelloy alloy with ultra-fine mirror electrolytic polishing, eliminating surface micro pits, burrs and grain boundaries that accumulate dust and carbon residues. After polishing, chemical passivation treatment forms a dense inert protective film on the metal surface, completely blocking trace heavy metal ion precipitation under long-term high-temperature contact with acidic medical and food melts. Ordinary matte unpolished steel sheaths have rough surfaces that trap tiny metal debris during thermal expansion friction, which peel off and mix into finished medical plastic parts, triggering product biocompatibility test failures.
Third, dust-free non-shedding outer cable insulation. Glass fiber braided insulation is completely banned for cleanroom thermocouples, as tiny fiber fragments fall off during bending and mold disassembly, polluting cleanroom air and melt. All outgoing wires adopt integral extruded PTFE insulation or seamless stainless steel flexible metal hoses. PTFE material releases zero toxic volatile substances below 260°C, with smooth surface that does not absorb dust; metal hoses isolate internal signal wires without shedding fine particles, suitable for high-temperature cleanroom mold wiring. Connector shells use solid PPS plastic without loose filler powder, and all internal spring shrapnels are passivated stainless steel to avoid rust powder shedding.
Fourth, low-particle spring bayonet contact structure optimization. Standard spring probes have gaps between spring coils that accumulate dust and carbon residues. Cleanroom customized springs adopt solid integral forming structure with seamless surface, and the compression stroke is precisely controlled to avoid metal friction debris generated by spring expansion and contraction. The compression fitting between probe and mold hole adds PTFE sealing gaskets to block mold steel metal abrasion particles from entering the sensing zone and contaminating the melt flow channel.
Fifth, dust-free packaging and delivery management specifications. Finished cleanroom thermocouples are ultrasonically cleaned with deionized water, baked to remove all moisture, then vacuum-sealed in dust-free PE bags in a Class 1000 clean workshop before delivery. Spare parts must be stored in sealed dust-proof cabinets inside the cleanroom, forbidden to be placed in ordinary workshop environments with oil, dust and metal scrap pollution. During mold maintenance, operators wear dust-free gloves to disassemble and install probes, avoiding hand oil and sweat contaminating the polished sheath surface.
Cleanroom thermocouple supporting verification certifications include FDA food contact material certification, ISO 13485 medical biocompatibility test report and RoHS heavy metal limit detection. Any cleanroom hot runner mold equipped with ordinary industrial thermocouples will face the risk of batch product contamination and customer factory audit failure, so standardized clean-grade sensor matching is a non-negotiable basic requirement for hygiene-level injection molding production.
