Introduction
Winding engineers requiring maximum slot fill, clean-soldering and no-shredded-strip from a fiber-insulated copper wire select Grade 1 Class 155 solderable polyurethane enameled wire. This conductor provides a Grade 1 tighter bulk insulation profile and the direct-solderability benefit of a polyurethane wire avoiding any mechanical stripping steps without sacrificing thermal performance in Class F environments.
What is Grade 1 Solderable Polyurethane Enameled Wire, Class 155?
Grade 1 solderable (completely dissolves cleanly in a bath, none required) polyurethane enameled wire, Class 155. Round Copper Winding with a single layer Enamel (Polyurethane) coated to 155 degrees °C.
Under IEC 60317-20:2013, the wire has a Grade 1 insulation build a very flat layer of evenly distributed enamel which provides the optimum cross sectional area of conductor in a 0.111 inch winding slot. This wire is also known popularly by the denominations 1UEW/155 or QA/155 Grade 1.[18]. Purchasing engineers also order by similar standards such as NEMA MW79-C or JIS C3215-2.
Together, direct solderability, headroom to 155 °C and Grade 1 dimensional accuracy make this series the one of first choice for small, high-performance precision magnet wire coils in electric motors, transformers, relay coils and RF electronic assemblies.
Key Specifications & Technical Parameters
The values below reflect IEC 60317-20:2013 requirements and published industry data.
| Parameter | Value / Range |
| Conductor material | Electrolytic tough pitch (ETP) copper |
| Conductor diameter range (Grade 1) | 0.018 mm – 0.800 mm |
| Insulation build | Grade 1 (single-layer polyurethane, minimum thickness per IEC table) |
| Thermal class | Class F — 155 °C continuous (IEC 60317-20:2013) |
| Temperature index | ≥ 155 (per IEC 60172) |
| Heat shock temperature | ≥ 175 °C (no cracking after winding on mandrel) |
| Cut-through temperature | No failure within 2 min at 200 °C |
| Breakdown voltage test temperature | 155 °C elevated temperature test |
| Solderability bath temperature | 390 ± 5 °C (solder bath, direct immersion) |
| Applicable standards | IEC 60317-20:2013; NEMA MW79-C; JIS C3215-2; GB/T 6109 |
Features and Benefits
Direct solderability at 390 ± 5 °C → no stripping operation, reduces assembly cycle time, and per unit labour cost in automated winding lines.
Insulation build in Grade 1 → thinner OD than Grade 2 for same conductor diameter, allowing for a higher copper fill factor and lower per coil DC resistance.
Thermal headroom to Class F ( 155 C)→ safe for motors, transformers, and solenoids running .sustained hi load cycles without insulation breakdown.
High frequency Q-value performance (e.g. Low dielectric loss tangent at high frequencies); specified for RF coils, flyback transformers and switching power supply windings.
If the continuous film does not contain pinholes it will, the Pinhole-free continuous filmbe able to resist the high-temperature breakdown-voltage testing the installation will endure, it will minimize the chance of inter-turn faults in coils which are both dense and high-voltage.
Humidity and abrasion resistance→ preserves the insulating integrity in sealed enclosures, potted assemblies and in high humidity operation.
Excellent Electrical Conductivity → It is made from high purity copper, offering low resistance for electrical use.
Superior Insulation and Dielectric Strength→Polyutherene Protects the Insulation from Mechanical Damage and Failure The polyutherene coating significantly insulates, has remarkable mechanical durability and is making less susceptible to the chances of a short circuit.
Applications
Wire of this type is used in practically all large and small critical components such as miniature and fractional-horsepower motors, power distribution transformers, as well as high-temperature continuous-duty solenoid valves. It is also utilized as insulated fine-wire in relay and contactor coils subjected to rapid switching cycles of heating and cooling. Others include high-frequency radio frequency (RF) inductors, RF coils, and precision instrument sensors. So from heavy industrial control boards to miniature consumer-electronic devices and HVAC sub-assemblies, Grade 1 UEW/155 is present.
Technical Specifications
| Property | Specification |
|---|---|
| Conductor Material | Copper |
| Insulation Type | Polyurethane |
| Thermal Class | 155°C |
| Grade | Grade 1 |
| Solderability | Direct solderable |
| Diameter Tolerance | As per IEC Standard |
| Electrical Conductivity | High |
Grade 1 vs Grade 2 — Choosing the Right Insulation Build
Grade 1 and Grade 2 refer to insulation build — not thermal class. Both grades are available in Class 155. The choice affects overall wire diameter, slot fill, and winding application.
| Attribute | Grade 1 | Grade 2 |
| Insulation build | Thinner (single minimum coat) | Heavier (double minimum coat) |
| Overall diameter | Smaller for same conductor size | Larger for same conductor size |
| Copper fill factor | Higher — preferred for tight slots | Lower — suitable for open-slot windings |
| Dielectric strength | Standard per IEC 60317-20 | Higher — preferred for elevated voltage stress |
| Typical use case | Fine-wire coils, high slot fill applications | Medium-voltage coils, higher inter-turn voltage |
| Automated winding compatibility | Excellent — less mechanical stress from thin build | Good — slightly more robust to handling |
Specify Grade 1 when maximum conductor cross-section in a fixed slot volume is the priority. Specify Grade 2 when inter-turn voltage stress demands a thicker insulation barrier.
UEW/155 vs UEW/130 and UEW/180 — Thermal Class Comparison
Selecting the right thermal class avoids over-engineering (UEW/180 where UEW/155 is sufficient) and protects against thermal failure (UEW/130 in Class F applications).
| Attribute | UEW / Class 130 | UEW / Class 155 | UEW / Class 180 |
| Thermal class | B (130 °C) | F (155 °C) | H (180 °C) |
| Temperature index | ≥ 130 | ≥ 155 | ≥ 180 |
| Heat shock temperature | ≥ 155 °C | ≥ 175 °C | ≥ 200 °C |
| Cut-through (no failure) | 175 °C / 2 min | 200 °C / 2 min | 220 °C / 2 min |
| Primary standard | IEC 60317-4 | IEC 60317-20 | IEC 60317-51 |
| Typical motor frame class | Class B | Class F | Class H |
| Cost premium over UEW/130 | Baseline | Low | Moderate |
UEW/155 is the volume specification for Class F motor and transformer designs. It offers material cost efficiency over UEW/180 while meeting all IEC and NEMA Class F insulation system requirements.
Frequently Asked Questions
Q: What temperature does Grade 1 UEW/155 solder at without stripping?
Grade 1 UEW/155 requires direct dipping into a bath at 390 ± 5 °C , per IEC 60317-20. When immersed at that temperature, the enamel will transfer into the molten solder without mechanical or chemical pre-treatment. The wire tip may be tinned in one dip with a smooth tinned surface free of pin holes as pass criterion.
Q: What is the standard for solderable polyurethane enameled wire (PUEW) Class 155?
The international governing standard is IEC 60317-20:2013(1), which sets forth the requirements for ’/… Solderable polyurethane enameled round copper winding wire, thermal class 155…/’.(1) The North American standard is NEMA MW79-C, while Japanese supply chains use JIS C3215-2. All include tolerances, thermal characteristics, solderability, and electrical characteristics.
Q: Is this grade 1 UEW/155 used for high frequency coil winding?
Indeed. Due to a relatively low dielectric dissipation factor at high frequencies, polyurethane enamel (UEW/155 Grade 1) is specified for use on flyback transformers, gate drive transformers, RF inductors and switch mode power supply windings. Specifies it for use where minimising the dielectric loss and hence the coil Q-value is a design criterion along with Class F thermal acceptance.
Request a Quote for Grade 1 UEW/155 Enameled Wire
Grade 1 solderable polyurethane enameled wire, Class 155, provides the best of both worlds by elegantly combining a direct-soldering friendly insulation build with an accurate construction to IEC 60317-20 specifications making assembly easier and meeting Class F thermal performance in motor, transformer, and high frequeny coil applications.
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