7.3

Thermal characteristics

The device thermal characteristics are defined below, and the constant values are given in Table 4:

•

θJA is the junction-to-ambient thermal resistance (EIA/JESD51-2 and EIA/JESD51-6).

θJA represents the resistance to the heat flowing from the chip to ambient air. It is an indicator of package

heat dissipation capability, a lower θJA means better overall thermal performance. It is calculated as

follows:

θJA = (TJ - TA)/PH

where:

–

TJ = junction temperature

–

TA = ambient temperature

–

PH = power dissipation

•

φJT is the junction-to-top-center thermal characterization parameter (EIA/JESD51-2 and EIA/JESD51-6).

•

φJT is used for estimating the junction temperature by measuring TT in an actual environment. It is

calculated as follows:

φJT = (TJ - TT)/PH

where TT = temperature at the top-center of the package

•

θJC is the junction-to-case thermal resistance.

θJC represents the resistance to the heat flowing from the chip to package top case. θJC is important when

an external heat sink is attached on package top. It is calculated as follows:

θJC = (TJ – TC)/PH

where TC = case temperature attached with a cold plate

•

θJB is the junction-to-board thermal resistance (EIA/JESD51-8).

•

θJB represents the resistance to the heat flowing from the chip to PCB. θJB is used in compact thermal

models for system

‑level thermal simulation. It is calculated as follows:

θJB = (TJ – TB)/PH

where TB = board temperature with ring cold plate fixture applied

Table 4. Thermal characteristics

Symbol

Max TJ (°C)

TT (°C)

φJT (°C/W)

θJA (°C/W)

θJB (°C/W)

θJC (°C/W)

Value

96.95

96.88

0.15

26.32

12.39

7.95

7.3.1

Board design

For information and recommendations related to board design, landing pads, stencils, and the solder reflow profile

for LGA packages, refer to AN5886 Guidelines for design and board assembly of land grid array packages,

available on www.st.com.

STM32WBA5MMG

Package information

DS14801 - Rev 3

page 14/25