Three-dimensional (3D) interconnection technology based on glass through vias (TGVs) has been used to integrate passive devices, and optoelectronic devices due to its superior electrical qualities, outstanding mechanical stability, and lower cost. Nevertheless, the performance and reliability of the device will be impacted by the thermal stress brought on by the mismatch of the coefficient of thermal expansion among multi-material structures and the complicated structure of TGV. This paper focuses on thermal stress evolution in different geometric and material parameters and the development of a controlled method for filling polymers in TGV interconnected structures. In addition, a numerical study based on the finite element (FE) model has been conducted to analyze the stress distribution of the different thicknesses of TGV-Cu. Additionally, a TGV interconnected structure model with a polymer buffer layer is given to solve the crack problem appearing at the edge of RDL. Meanwhile, after practical verification, in comparison to the experimental results, the FE model was shown to be highly effective and accurate for predicting the evolution of stress, and several recommendations were made to alleviate stress-related reliability concerns. An improved manufacturing process flow for the TGV interconnected structure was proposed and verified as feasible to address the RDL crack issue based on the aforementioned research. It provides helpful information for the creation of highly reliable TGV connection structures.

The introduction of 5G mobile communication created the need to support a large number of radio frequency (RF) bands. This required high performance and reduced size for microacoustic filters. Based on these requirements, a new three-dimensional wafer-level packaging (3-D WLP) solution based on the predecessors’ developed technology was presented to resolve reliability issues for surface acoustic wave (SAW) filter packages with large cavities. In the 3-D WLP, vertical interconnects were realized using through glass vias (TGVs). To enable such a process scheme, thin glass caps with TGVs were formed through laser-induced chemical etching. Then, glass capping dies were bonded on the corresponding LiTaO ₃ (LT) device wafer to generate a cavity structure. Partial filling of the vias on the pad was used, and a metal trace was formed on the glass. Ball grid arrays (BGAs) were formed on top of the glass. Finally, an SAW filter WLP was fabricated. This glass capping packaging avoids the outgassing problem of conventional thin-film acoustic packaging at high temperatures, which would cause the contamination of the interdigital transducers (IDTs). In addition, a numerical study based on the 3-D finite element (FE) model has been conducted to analyze the reliability of the package. The built model was applied to perform parametric studies on the effects of package geometry, material properties, and the processing conditions on reliability. Based on the above studies, the optimized SAW filter WLP successfully passed the reliability test of pre-con level 3 and temperature cycling test (TCT, −40 °C ~ 125 °C).

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.

The rapid growth of the advanced consumer 5G wireless mobile phones has propelled the demands of fabricating surface acoustic wave (SAW) filters with smaller size and high performance. Three-dimension wafer-level package (3-D WLP) for SAW filter is a promising solution to replace conventional surface mounted technology and chip-scale packaging. In this article, a new WLP for SAW filter with a size of 1.3 mm ×1.1 mm ×0.35 mm is developed using thin dry film capping. The new 3-D WLP significantly reduces the overall thickness which is particularly meaningful for low-profile smartphones and tablets. A number of key processes were developed. To improve the quality, finite element modeling (FEM) is used to simulate the mechanical stress to optimize cavity structure. Reliability tests were performed and the results indicated that there were no significant frequency response changes occurred and low insertion loss (IL) in pass band was less than 0.2 dB after pro-conditional level 3 test, unbiased highly accelerated stress (uHAST) test, and temperature cycling (TC) test on SAW filter packages. It can be concluded that 3-D WLP for SAW filter achieves miniaturization, good electrical performance, and reliability.

In recent years, glass interposer has emerged as a superior alternative to organic and silicon-based interposers for advanced 2.5D or 3D IC, due to its attractive advantages such as excellent electrical isolation, better radio frequency performance, better feasibility with the CTE and could be fabricated with large size. However, the warpage for wafer level 2.5D or 3D packaging using glass interposer is a serious issue. In this paper, A new type of 3D wafer level packaging for MEMS based on glass interposer is presented and the warpage during the molding process is investigated based on finite element simulation. The effect of different material parameters and thickness of glass on warpage characteristics is investigated. The results show that when the CTE increases from 3 ppm/°C to 10 ppm/°C for glass interposer, the wafer warpage variation from “smile” to “cry”. Our experiments indicated that the optimized glass interposer successfully passed the reliability test of precondition level 3. It is a conclusion that the process flow of the glass interposer and FEM simulation process offers a significant reference for 3D product applications. Moreover, in the next step, we will discuss how to modify the material parameters and thickness of the EMC to improve the performance of the glass interposer.