IEC 60738-1-1:2008

Overview

IEC 60738-1-1:2008 is the IEC blank detail specification for directly heated positive step‑function PTC thermistors intended for current‑limiting applications (assessment level EZ). It is a supplementary document to the IEC 60738‑1 generic specification and defines the required style, layout and minimum content for any detail specification. Detail specifications that do not follow IEC 60738‑1‑1 cannot be described as IEC‑compliant. This publication is to be read in conjunction with IEC 60738‑1 (generic specification).

Key topics and requirements

• Purpose and scope: Provides a template and mandatory content to ensure uniformity and traceability of detail specifications for PTC current‑limiting thermistors.
• Identification & drawings: Requires clear identification, short description, outline drawing (main dimensions), construction notes and assessment level (EZ).
• Mechanical & mounting data: Method(s) of mounting, dimensions (gauging), coating, and termination details (including solderability suitability).
• Electrical ratings & characteristics: Specifies items that must be given in the detail specification, such as upper/lower category temperatures (UCT/LCT), operating temperature range, maximum voltage, zero‑power resistance, tripping current, maximum non‑tripping current, residual and overload currents, and switching temperature.
• Marking, packaging & ordering: Mandatory marking requirements, packaging details and minimum ordering information (style, maximum continuous AC voltage, detail spec reference).
• Inspection & testing: Defines qualification and quality conformance procedures, including lot‑by‑lot (100% and sampled) and periodic test schedules. References sampling plans (IEC 60410), environmental and soldering tests (e.g., IEC 60068‑2‑58) and requirements for destructive vs non‑destructive testing.
• Documentation rules: Minimum content for test schedules, acceptance criteria (p, n, c values), test conditions and how to reference the generic specification.

Applications and users

Who uses IEC 60738‑1‑1:

• Manufacturers and component spec writers drafting IEC‑compliant detail specifications for PTC current‑limiting thermistors.
• Quality, test and inspection teams implementing specified lot and periodic inspection regimes.
• Purchasing and compliance personnel verifying vendor detail specifications are IEC‑compliant.
• Design engineers and system integrators specifying inrush/current‑limit components for power supplies, motor start protection, surge limiting or overcurrent protection.

Related standards

• IEC 60738‑1 (generic specification for directly heated PTC thermistors) - essential companion document.
• IEC 60068‑2‑58 (solderability/environmental tests for SMD) and IEC 60410 (sampling plans) - normative references used in test schedules.

Keywords: IEC 60738‑1‑1, thermistors, PTC thermistor, positive step‑function, current limiting, detail specification, assessment level EZ, quality conformance, sampling plan, solderability.