Failure Mechanism of Underfill Fillet Cracks in Flexible Wearable Electronics

This paper studies the failure mode and failure mechanism of the underfill fillet cracks of a flexible surface-mount device, where the device is produced by mounting the stiff components directly onto the surface of a flexible printed circuit board; the underfill encapsulants are used to reduce the stresses around the solder joints. The underfill fillet cracks are observed in failed devices by the...