The OPAx863 does not require heat sinking or airflow in most applications. The maximum allowed junction temperature sets the maximum allowed internal power dissipation. Do not allow the maximum junction temperature to exceed 150°C.
Operating junction temperature (TJ) is given by,
As a worst-case example, compute the maximum TJ using an OPA2863-DGK (VSSOP package) configured as a unity gain buffer, operating on ±6-V supplies at an ambient temperature of 25°C and driving a grounded 500-Ω load.
PD = 12 V × 2 mA + 62 /(4 × 500 Ω) = 42 mW
Maximum TJ = 25°C + (0.042 W × 180.3°C/W) = 33°C, which is well below the maximum allowed junction temperature of 150°C.