4.3.2.1 WCSP (YBG) Package

Revision B of the Bluetooth-Enabled High Accuracy Skin Temperature Measurement Flex PCB Patch uses the TMP117AIYBGR to demonstrate one potential technique for measuring skin temperature. In this design, the WCSP version of the TMP117 has the coated backside placed directly against the skin of the wearer, and heat is conducted from the skin directly to the TMP117. In an end system that uses this technique the TMP117 can be covered in a soft overmolding to protect the device from damage.

This technique can be modified for applications that use enclosures but still want to measure skin temperature such as smartwatches or earbuds. The TMP117 can be placed against a metal contact to conduct heat from the wearer's skin, as shown in Figure 24. Alternatively, the underside of the device can be used to transfer heat as shown in Figure 25. If using the underside of the package, consider using a board stiffener made of a biocompatible and thermally conductive material such as stainless steel.