Effective Transmission of High Frequency Ultrasound into a Silicon Chip through a Polymer Layer

摘要

In this paper, we describe an effective transmission method of high frequency ultrasound into a silicon chip via the polymer layers. The layer is inserted between water and the chip, and the pressure of about 0.1 MPa is applied to the contact interface between the layer and the chip. The polyvinylidene chloride and polyvinyl chloride layers of 9 μm thick bring the ultrasonic resonance between water and silicon, and the ultrasound in the frequency range of 20 to 80 MHz is transmitted into the chip more effectively than the usual water immersion case. In practice, we carry out the acoustic imaging of the flip chip package via the layer, and clearly visualize the defective solder bumps beneath the chip under the dry-contact condition. Besides, the quality of the dry-contact image is equivalent to the water immersion image.