ISO 4825-1:2023

Overview

ISO 4825-1:2023 - part of the ISO series on fine ceramics (advanced technical ceramics) - specifies a standardized test method for thermal property measurements of metalized ceramic substrates, focused on evaluation of thermal resistance for use in power modules. The method simulates a high‑output SiC (silicon carbide) power module by mounting a heater chip on a metallized ceramic substrate and measuring heat flow to a temperature‑controlled cold plate. The result is an index of the substrate’s heat‑dissipating performance in power electronics.

Key Topics and Requirements

• Scope & Principle
  • Measures the thermal resistance (K/W) between a heater chip and a cold plate by dividing the temperature difference by the heat power radiated from the heater chip in a bonded assembly.
  • Aims to minimize measurement error through steady‑state conditions and temperature‑controlled cooling.
• Apparatus
  • Metalized ceramic substrate with front metallic pattern (heater area + insulated electrode pads) and a full metal back layer.
  • Heater chip that imitates a semiconductor device - typically SiC or equivalent thermal conductivity; nominal dimensions 5 mm × 5 mm (thickness ≤ 0.5 mm); heat output ≥ 200 W; temperature tolerance ≥ 250 °C; includes built‑in temperature sensor.
  • Cold plate (recommended > 60 × 60 × 20 mm) connected to a chiller capable of offsetting heater power.
  • Power supply, controller/recorder, and thermocouples/temperature sensors (complying with IEC 60584‑1 where applicable).
• Procedure & Materials
  • Heater chip bonded to substrate using a thin, high‑conductivity joining layer/TIM (e.g., Au/Cu/Zn‑based solders or Ag sinter) with heat resistance ≥ 250 °C.
  • Maintain identical test conditions (cold plate, chiller flow, joining layer) across measurement series.
  • Includes calculation, reporting requirements, and examples of test set‑up (Annex A) plus interlaboratory evaluation data (Annex B).
• Normative references
  • ISO 554 (standard atmospheres) and IEC 60584‑1 (thermocouples).

Applications and Users

• Practical for manufacturers of metallized ceramic substrates, power module designers, materials engineers, and independent test laboratories who need a repeatable index of heat‑dissipation performance for:
  • SiC and other wide‑bandgap power modules
  • High‑output power electronics where thermal management is critical
  • Qualification of joining materials and thermal interface materials (TIMs)
• Useful in R&D, quality control, product comparison, and design validation to optimize substrate selection and thermal path design.

Related Standards

• ISO 554 - Standard atmospheres for conditioning/testing
• IEC 60584‑1 - Thermocouples: EMF specs and tolerances
• ISO/TC 206 - Technical committee responsible for fine ceramics series

Keywords: ISO 4825-1:2023, fine ceramics, metallized ceramic substrate, thermal resistance measurement, power modules, SiC, heater chip, cold plate, TIM, chiller, thermal conductivity.