Rigid PCB Coupon Boards (11mm × 22mm, with a thickness of 64 mils)

Thermal Response, 64mil Rigid CB, DRV Package, Thermal Pad Soldered and Thermal Response, 64mil Rigid CB, DRV Package, Thermal Pad not Soldered display the thermal response for a 64mil rigid PCB with QFN packaged parts, both with and without soldered thermal pads. The data show that when the thermal pad is soldered, the thermal resistance is about twice as low compared to when it is not soldered. In both cases, the stabilization time for heating and cooling is approximately 5 seconds.

Figure 3-3 Thermal Response, 64mil Rigid CB, DRV Package, Thermal Pad Soldered

Figure 3-4 Thermal Response, 64mil Rigid CB, DRV Package, Thermal Pad not Soldered

Note that the 63.8%, 86.4%, and 95% levels of the final temperature steps align with the Gaussian step function temperature change diagram. The deviation from the ideal step function is more pronounced in the 64mil rigid PCB, while the 32mil thick PCB shows a closer match to the ideal curve.

Flex PCB Coupon Boards (11mm × 22mm, with a thickness of 6 mil)

Thermal Response, 6mil flex CB, DRV Package, Test Point Soldered and Thermal Response, 6mil flex CB, DRV Package, Test Point not Soldered highlight the thermal response of the device on a 6mil flexible PCB with QFN packaged parts. When the thermal pad is not soldered, the self-heating temperature is 1.8 to 2 times higher than in the soldered condition. The stabilization time for heating and cooling improves to 3-4 seconds. The data indicate that the heating and cooling curves match the calculated ideal curve due to the reduced connected thermal mass of the flexible PCB.

Figure 3-5 Thermal Response, 6mil flex CB, DRV Package, Test Point Soldered

Figure 3-6 Thermal Response, 6mil flex CB, DRV Package, Test Point not Soldered

Rigid PCB (11mm × 22mm, 32 mil thickness)vs. Flex PCB (11mm × 22mm, 6 mil thickness)

Thermal Response, 32mil Rigid CB, YBG Package and Thermal Response, 6mil flex CB, YBG Package show the temperature change on rigid and flexible PCB with BGA WCSP parts. The thermal step similarity in both cases indicates that the primary thermal resistance comes from the BGA package and PCB contacts, not from the PCB. The 6mil flexible PCB achieve a settling time of less than 2 seconds, with the heating curves closely aligning with the ideal step function curves. This improvement can be attributed to the lower thermal mass of the flexible PCB.

Figure 3-7 Thermal Response, 32mil Rigid CB, YBG Package

Figure 3-8 Thermal Response, 6mil flex CB, YBG Package