Electrically-isolated and moisture-resistant designs for wearable devices
An example continuous glucose monitor includes a printed circuit board (“PCB”) having first and second outer layers and an inner layer; a semiconductor package having a plurality of pins coupled to the first outer layer of the PCB; an electrical contact formed on the second outer layer of the PCB; a trace having a first portion disposed on the first outer layer, a second portion disposed on the inner layer, and a third portion disposed on the second outer layer, the trace having a first end coupled to a first pin of the plurality of pins and a second end coupled to the electrical contact; and an encapsulant disposed around a perimeter of the semiconductor package, the encapsulant covering the plurality of pins, the first portion of the sensor trace, the third portion of the sensor trace, wherein an upper surface of the semiconductor package remains exposed.
1 . A wearable device comprising:
a printed circuit board (“PCB”) having first and second outer layers and an inner layer, the inner layer disposed between the first and second outer layers;
a semiconductor package having a plurality of pins, the semiconductor package coupled to the first outer layer of the PCB via the plurality of pins;
an electrical contact for a sensor formed on the second outer layer of the PCB;
a sensor trace having a first portion disposed on the first outer layer, a second portion disposed on the inner layer, and a third portion disposed on the second outer layer;
an encapsulant disposed around a perimeter of the semiconductor package, the encapsulant covering (i) the plurality of pins, and (ii) the first portion of the sensor trace, wherein the encapsulant is configured to not cover the sensor, and wherein an upper surface of the semiconductor package remains exposed.
2 . The wearable device of claim 1 , further comprising a housing defining a cavity and comprising a first housing portion and a second housing portion, the first housing portion coupled to the second housing portion to define the cavity.
3 . The wearable device of claim 2 , wherein the PCB is disposed between the first and second housing portions.
4 . The wearable device of claim 2 , wherein the first housing portion is welded to the second housing portion.
5 . The wearable device of claim 2 , wherein the second housing portion includes a first hole to allow the sensor to extend outside of the housing.
6 . The wearable device of claim 5 , wherein the PCB includes a second hole aligned with the first hole to allow the sensor to extend through the PCB.
7 . The wearable device of claim 6 , wherein the encapsulant is further disposed within the first hole and/or the second hole.
8 . The wearable device of claim 1 , wherein the sensor comprises first and second electrodes.
9 . The wearable device of claim 1 , wherein the encapsulant has a glass transition temperature greater than 45 degrees Celsius and a cure temperature of less than 175 degrees Celsius.
10 . The wearable device of claim 1 , wherein the encapsulant has a glass transition temperature greater than an operating temperature range of the wearable device and a cure temperature substantially lower than a melting temperature of a housing material of the wearable device.
11 . The wearable device of claim 1 , wherein the encapsulant has a resistivity of at least 10 13 ohms per centimeter.
12 . The wearable device of claim 1 , wherein a total height of the PCB and the semiconductor package is less than 9 millimeters.