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2021.05.26 Thermal Design

Thermal Resistance Data: JEDEC Standards, Thermal Resistance Measurement Environments, and Circuit Boards

Thermal Design of Semiconductor Components in Electronic Equipment

From this article, we explain thermal resistance data. We begin with standards and measurements relating to thermal resistance.

JEDEC Standards

JEDEC (the Joint Electron Device Engineering Council) is an industry organization that develops standards in the field of semiconductor components. There are numerous standards that must necessarily be dealt with not only by semiconductor manufacturers, but by others in the field of electronics as well. That measurement methods and conditions must conform to industry standards, regardless of heat issues, is a fundamental principle. It goes without saying that this is because comparisons and pass/fail judgments would not be possible if methods and conditions were not unified.

Among the JEDEC standards, the following are the main two standards relating to heat.

 JESD51 series:Includes nearly all standards relating to heat in packages for ICs and other            components
 JESD15 series:Standardizes thermal resistance models used in simulations

The following describes representative heat-related standards in the JESD51 series.

JESD51 Summary
JESD51-1 ETM methods for TJ measurements and transient thermal measurement methods (Dynamic/Static methods)
JESD51-2A Natural convection environments (Still Air) for thermal measurements of IC packages
JESD51-3 Low thermal conductivity boards for SMP package measurements
JESD51-4 Standards for TEG chips for thermal measurements
JESD51-5 Test board standards for packages with heat-dissipating components (fins etc.)
JESD51-6 Forced convection environments (Moving Air) for thermal measurements of IC packages
JESD51-7 High thermal conductivity boards for SMP package measurements
JESD51-14 Methods for Rthjc measurement of packages having one-dimensional heat dissipation paths

Thermal Resistance Measurement Environments

Environments for measurement of thermal resistance are stipulated in JESD51-2A. The following is an example of a thermal resistance measurement environment conforming to the JESD51-2A standard.

By placing the object for measurement within an acrylic chamber, securing a still-air state, the effect of airflow in the vicinity is eliminated, and the object for measurement is in a natural cooling state. By always setting the object for measurement in the same position, highly reproducible measurements are ensured.

Thermal Resistance Measurement Boards

There are also standards relating to the boards used to measure thermal resistance. Boards generally known as "JEDEC boards" are standardized by JESD51-3/5/7. An example is shown below.

Thermal resistance data is in essence acquired in conformance with these standard specifications. Ordinarily the standard specifications are also explicitly stated.

Key Points:

・Thermal resistance data is acquired in conformation with standard specifications; ordinarily the standard specifications are clearly stated as well.

・Among the JEDEC standards, the following are the main two standards relating to heat.
 -JESD51 series:Includes nearly all standards relating to heat in packages for ICs and
  other components
 -JESD15 series:Standardizes thermal resistance models used in simulations

・Environments for measurement of thermal resistance are stipulated in JESD51-2A.

・The boards used to measure thermal resistance are stipulated in JESD51-3/5/7.

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