Polyimide Capillary Tube: Custom PI Micro-Tubing for Sensors & Semiconductor Equipment

Polyimide (PI) capillary tube is a thin-wall tube with capillary-size inner diameter, made from polyimide resin, varnish or film. WELLELE manufactures PI
capillary tubing by four routes — extrusion, dip coating, flat winding and spiral winding — each with different seam structure, lumen geometry, wall build
and cut-length behavior. Reviewed custom sizes range from capillary IDs upward to approximately 50 mm ID, with wall thickness from about 0.015 mm to 0.35 mm; the exact combination depends on process, tolerance and application.

Thin wall polyimide tubing

Polyimide (PI) capillary tube in extruded, dip-coated, flat-wound or spiral-wound construction. Capillary-size IDs, walls from 0.015 mm, for sensors, thermocouples and semiconductor equipment.

Thermistors and temperature sensors

. Thin-wall PI capillary insulates and protects thermistor and temperature-sensor leads in compact assemblies without adding stiffness.

Analytical and laboratory instruments

. PI capillary tubing appears in precision instruments and small-diameter component rotection; where fused silica is used for separation science, PI is an alternative when flexibility and electrical insulation matter more than optical clarity

Semiconductor probe and process equipment.

PI capillary is used for probe insulation, tooling separation and component rotection where cleanliness, temperature and electrical isolation are specified.

Thermocouples and hot-spot wiring.

PI capillary separates thermocouple wires and sensor junctions where glass braid or PTFE cannot handle the temperature

thin PI tube Key Reference Data

Parameter	Reference value	Basis / source
Custom tube ID	Capillary sizes to approx. 50 mm	WELLELE capability review (per process)
Custom wall thickness	Approx. 0.015 mm to 0.35 mm	WELLELE capability review (per process)
PI film continuous temperature	UL-rated continuous service 220–240 °C, grade-dependent	DuPont™ Kapton® datasheets (via MatWeb)
PI film brief peak exposure	Up to 400 °C	DuPont™ Kapton® datasheets
PI film low-temperature usability	Down to −269 °C	DuPont™ Kapton® datasheets
Dielectric strength (film)	Approx. 7,700 V/mil at 1 mil (0.025 mm) film; lower at greater thickness	ASTM D149 (per film grade)
Dielectric constant	Approx. 3.4 at 1 MHz (film)	Film manufacturer datasheets
Flammability	UL 94 V-0 (selected Kapton film grades)	UL 94, per grade datasheet
Compliance documents	RoHS / REACH declarations matched to exact product scope	Supplier document review

Material-film data is reference information and does not define finished-tube performance. Finished-tube results depend on film grade, process, wall construction, seam structure, curing or winding condition and cutting method.
Confirm critical values by sample testing before volume production.

Which Construction Fits a Capillary-Size Part?

Construction	Capillary suitability	Seam	Typical use
Extruded PI tube	Seamless, true capillary IDs from about 0.2 mm	None (non-wound lumen)	Sensor leads, probes, coil and continuous formats
Dip-coated PI tube	Thin-wall precision, controlled surface	None (coated over mandrel)	Thermistor leads, semiconductor tooling, tight-wall tolerances
Flat-wound PI tube	Compact short sleeves, small-bore fit	Axial film overlap	Short capillary sleeves, lead isolation
Spiral-wound PI tube	Larger bores, adjustable wall build	Helical overlap	Probe shafts, larger sensor assemblies

Extruded and dip-coated constructions give a non-wound lumen — usually the right choice when the capillary ID, roundness or wall uniformity is the critical
dimension. Wound constructions are chosen when film source, cut-length format or larger bore matters more.

Custom Sizes and Tolerances

Parameter	Range (indicative)	Notes
Inner diameter	From approx. 0.2 mm capillary	Extruded/dip-coated give the smallest true capillary IDs
Outer diameter	Sized to ID + wall	Check roundness and ovality for long lengths
Wall thickness	Approx. 0.015–0.35 mm	Thin wall preferred for heat transfer; thicker wall for voltage standoff
Cut length	Custom, coil or straight	Coil format common for continuous runs
Typical tolerance	Reviewed per critical dimension	ID, wall, length and cut-end specified separately

State which dimension is critical — ID, wall, roundness or cut-end — before quotation. Different processes hold different tolerances on each.

PI Capillary vs Fused Silica vs Metal Capillary

Aspect	PI capillary	Fused silica capillary	Metal capillary
Electrical insulation	Insulating	Insulating	Conductive (needs coating)
Flexibility	Flexible, bend-tolerant	Brittle, fragile at small OD	Stiff, formable
Temperature	−269 °C to 400 °C (film data)	High, application-dependent	High
Chemical resistance	Good, moderate acids	Excellent	Depends on metal
Cost at small ID	Moderate	Low-moderate	Moderate-high
Typical use	Sensor leads, probe insulation	Chromatography, separation science	Precision fluidics, structural

Custom PI Micro-Tubing FAQ

What is the smallest polyimide capillary tube you make?

Extruded construction supports true capillary IDs from about 0.2 mm.
Dip-coated and wound constructions cover other thin-wall and sleeve formats.
Send the ID, wall and application to confirm the starting size

Is polyimide capillary tube heat shrink?

 No. PI does not shrink like polyester heat-shrink tubing. If shrink fit is
required, review Mylar/polyester heat-shrink tubing instead.

What temperature can PI capillary tube withstand?

PI film is usable down to −269 °C and is UL-rated for continuous service at 
220–240 °C in many grades, with brief exposure up to 400 °C. Finished-tube
temperature capability depends on wall and construction — confirm by sample.

Can you supply PI capillary in coil form?

Yes, where the construction and wall allow. Extruded PI is available in coil format for continuous runs; wound constructions are normally cut to length.

How do I specify a polyimide capillary tube?

Send ID, OD or wall, length, tolerance priority, operating temperature, electrical duty and the assembly method. We review manufacturability before quotation.

Is "Kapton tube" the same as polyimide tube?

Kapton is a DuPont brand of polyimide film. A Kapton tube is a film-based PI tube with confirmed film source; extruded and dip-coated PI tubes are described
as polyimide tube. See our polyimide vs Kapton comparison.

Polyimide Capillary Tube: Custom PI Micro-Tubing for Sensors & Semiconductor Equipment

Thin wall polyimide tubing

Thermistors and temperature sensors

Analytical and laboratory instruments

Semiconductor probe and process equipment.

Thermocouples and hot-spot wiring.

Custom PI Micro-Tubing FAQ

Prepare a Polyimide Tube RFQ

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