IEC TR 63378-1:2021 PDF

Overview

IEC TR 63378-1:2021 - Thermal standardization on semiconductor packages, Part 1 - defines common terminology and usage guidelines for thermal resistance and thermal characterization parameters of BGA and QFP semiconductor packages. The Technical Report standardizes how thermal metrics are described (temperatures, resistances and characterization parameters) and provides guidance on measurement variability, simulation practices and thermal design considerations relevant to package- and board-level thermal assessment.

Key topics and technical requirements

• Scope and definitions: Precise definitions of temperature points such as ambient air temperature (T_A), junction temperature (T_J), case/top temperature (T_C / T_T) and board temperature (T_B).
• Thermal resistance: Formalization of thermal resistance concepts including junction-to-ambient (θ_JA), junction-to-case/top (θ_JC / θ_JCTOP) and junction-to-board (θ_JB). Example equation given: θ_JA = (T_J − T_A) / P (where P is steady‑state power dissipation).
• Thermal characterization parameters: Clarifies Ψ-parameters (for example Ψ_JT, Ψ_JB) which relate a temperature difference to total device power and are distinct from pure thermal resistance.
• Accuracy and variability of θ_JA: Analysis of factors that influence θ values - board copper distribution, ambient conditions, power dissipation and measurement/simulation setup. The report includes simulation models (examples: a 35 mm × 35 mm BGA 544-pin package and a 20 mm × 20 mm LQFP 144-pin package) to illustrate variation and discrepancy of θ.
• Guidelines for thermal design: Practical advice for using thermal characteristics in device and system-level thermal assessments; outlines evaluation items and simulation conditions to improve comparability.
• Normative reference: Links to IEC 60191-4 for package outline coding and classification.

Practical applications and intended users

IEC TR 63378-1 is designed for professionals involved in thermal management and semiconductor packaging:

• Package designers and semiconductor manufacturers - to standardize datasheet thermal terms and reporting.
• Thermal engineers and system architects - for accurate thermal modeling (θ and Ψ use) and component selection.
• PCB designers - to understand board copper effects and placement impact on package thermal resistance.
• Reliability / test laboratories - to harmonize measurement setups and compare θ results across vendors. Practical uses include defining thermal specifications on datasheets, creating simulation boundary conditions, performing junction-temperature calculations, and guiding system-level cooling strategies.

Related standards

• IEC 60191-4 (mechanical standardization and package coding)
• Other parts of the IEC 63378 series (see IEC webstore for the full series)

Keywords: IEC TR 63378-1, thermal resistance, thermal characterization parameter, θ_JA, Ψ_JT, BGA thermal, QFP thermal, semiconductor package thermal design.