Development of 3D Wafer Level Hermetic Packaging with Through Glass Vias (TGVs) and Transient Liquid Phase Bonding Technology for RF Filter

Abstract

The development of 5G mobile communication created the need for high-frequency communication systems, which require vast quantities of radio frequency (RF) filters with a high-quality factor (Q) and low inband losses. In this study, the packaging of an RF filter with a through-glass via (TGV) interposer was designed and fabricated using a three-dimensional wafer-level package (3D WLP). TGV fabrication is a high-yielding process, which can produce high precision vias without masking and lithography and reduce the manufacturing cost compared with the through silicon via (TSV) solution. The glass interposer capping wafer contains Cu-filled TGV, a metal redistribution layer (RDL), and the bonding layer. The RF filter substrate with Au bump is bonded to the capping wafer based on Au-Sn transient liquid phase (TLP) bonding at 280 °C with a 40 kN (approximately 6.5 MPa) bonding force. Experimental results show that shear strengths of approx. 54.5 MPa can be obtained, higher than the standard requirement (~6 MPa). In addition, a comparison of the electrical performance of the RF filter package after the pre-conditional level three (Pre-Con L3) and unbiased highly accelerated stress (uHAST) tests showed no difference in insertion attenuation across the passband (<0.2 dB, standard value: <1 dB). The final packages passed the reliability tests in the field of consumer electronics. The proposed RF filter WLP achieves high performance, low cost, and superior reliability.

Ultrahigh Aspect Ratio Through Glass Vias Perforation Utilizing Selective Laser‐Induced Etching with Nanochannels

“…Currently, TGVs are gaining traction over TSVs [14,15] because of their superior electrical properties and cost-effectiveness, particularly in the radio frequency field where they are favored over traditional organic and silicon interposers. [16,17] One of the main challenges in TGV fabrication is the high-density perforation of vertical vias through glass substrates. Traditional methods like photosensitive glass, [18,19] focused electrical discharging, [20] laser drilling, [21,22] and electrochemical discharge machining [23,24] are hindered by issues such as large hole sizes, uneven sidewalls, and slow etching rates.…”

“…Currently, TGVs are gaining traction over TSVs [ 14,15 ] because of their superior electrical properties and cost‐effectiveness, particularly in the radio frequency field where they are favored over traditional organic and silicon interposers. [ 16,17 ]…”