C110 Copper vs C145 Tellurium Copper
C110 ETP copper and C145 tellurium copper are both near-pure conductive coppers, but they trade off in different directions. C110 maximizes electrical and thermal conductivity (391 W/m·K nominal) at the cost of gummy, difficult machining. C145 adds a small tellurium addition that makes it essentially free-machining while retaining most of that conductivity, ideal for machined conductors.
The verdict
Choose C110 for busbars, terminals and heat-sink parts where maximum conductivity matters more than machining ease. Choose C145 when you must CNC the part on a screw machine or lathe and can accept a slight conductivity drop (~355 vs 391 W/m·K nominal) for far better chip control and cycle time.
Side-by-side data
| Property | C110 Copper | C145 Tellurium Copper |
|---|---|---|
| Category | Copper Alloy | Copper Alloy |
| Density (g/cm³) | 8.94 | 8.94 |
| Tensile strength (MPa) | 220 | 250 |
| Yield strength (MPa) | 70 | 205 |
| Elongation (%) | 45 | 20 |
| Hardness | 40 HB | 70 HRB |
| Max service temp (°C) | 200 | 350 |
| Machinability | ●●●●● | ●●●●● |
| Corrosion resistance | ●●●●● | ●●●●● |
| Relative cost | ●●●●● | ●●●●● |
| Thermal cond. (W/m·K) | 391 | 355 |
| Typically used for | Electrical & thermal conductivity parts | Machined electrical conductors |
Which should you choose?
Choose C110 Copper when…
- You need the highest possible electrical and thermal conductivity (391 W/m·K nominal) for busbars, terminals or heat sinks
- Parts are sheared, stamped or cold-formed rather than heavily machined
- High elongation (~45%) and ductility for bending and forming is a priority
- The part is welded or brazed — C110 takes these joints cleanly without tellurium
- Code or spec calls out ETP/C11000 for electrical conductors
- Cost needs to stay at the lower end of the conductive-copper range
Choose C145 Tellurium Copper when…
- Parts are CNC-turned or screw-machined and C110's poor machinability (3.0 vs 4.5) hurts cycle time and finish
- You need good conductivity AND high production-rate machining in one material
- Higher yield strength (205 vs 70 MPa nominal) helps the part hold tolerance and resist deformation
- Service temperatures run hotter — C145 lists a higher 350°C nominal max vs 200°C
- You're making machined electrical contacts, connectors or welding tips
- Chip control and tool life on automatic machines drive part cost
Key differences that matter
- Both share copper's ~8.94 g/cm³ density and excellent conductivity class; C110 leads on raw conductivity (391 vs 355 W/m·K nominal).
- C145's tellurium addition roughly free-machines the copper, raising machinability to 4.5 vs C110's 3.0 — the single biggest practical difference.
- C145 carries much higher yield (205 vs 70 MPa nominal), so machined C145 parts hold dimensional stability better.
- C110 is more ductile (~45% vs ~20% elongation), favoring forming, bending and cold work.
- Both cost similarly in the conductive-copper band; the choice is process-driven, not price-driven.
- Tellurium can impair some welding/brazing — C110 is the cleaner pick where joining is critical.
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Open the Material SelectorGet a Quote →Frequently asked questions
How much conductivity do you lose going from C110 to C145?
Only a small amount. C110 is the conductivity benchmark at roughly 391 W/m·K thermal (nominal), and C145 retains most of it at about 355 W/m·K. Electrical conductivity follows the same pattern — C145 sits near 90–95% IACS versus C110's ~100%. For most machined conductors that drop is negligible against the machining gain.
Why is C110 so hard to machine?
Pure ETP copper is soft, ductile and gummy, so it smears and forms long stringy chips instead of breaking cleanly. That gives it a low machinability rating (3.0 here) and poor surface finish on lathes. C145 solves this with a tellurium addition that breaks chips, which is why it rates 4.5.
Can I weld C145 tellurium copper?
It can be joined, but the tellurium addition makes welding and brazing less forgiving than pure C110, and it can cause hot-cracking in some processes. If the part is welded or brazed as a primary joining method, C110 is the safer choice; reserve C145 for bolted, soldered or mechanically fastened machined parts.
Which is better for a heat sink?
C110, when the part is formed, stamped or extruded, because it gives maximum thermal conductivity (391 W/m·K nominal). If the heat sink must be CNC-machined with fine features and tight tolerances, C145 is a practical compromise — slightly lower conductivity but far easier to cut.
Property values are typical/nominal figures for early-stage guidance only and vary by temper, grade, supplier and heat treatment. Confirm critical specifications against a certified datasheet or with an mfgiq engineer before production.