High-frequency characterization of through package vias formed by focused electrical-discharge in thin glass interposers

Abstract

This paper presents the modeling, design, fabrication and characterization, up to 30 GHz, of low loss and high aspectratio 55 μm diameter through package vias (TPVs) in 300 μm thick glass interposers. These TPVs were fabricated using a novel, high-throughput, focused electrical discharge method and low cost panel-based double-side metallization processes. Such a glass interposer is targeted at two emerging applications, (a) large 30 mm to 60 mm body size 2.5D interposers to achieve 28.8 Gbps logic-memory bandwidth and (b) 3D interposers for mm wave applications at 28 GHz local multipoint distribution service (LMDS) for future 5G networks. Accurate measurement of the electrical performance of fine pitch metallized through vias in glass up to 30 GHz and beyond is critical for both these high performance interposer applications. In this paper, two novel characterization methods are applied: 1) the short-circuit-andopen-circuit method and 2) the dual-via-chain method. The resistance and the inductance of a single via are extracted by using a short-circuit structure along with an open-circuit structure. At 10 GHz, the values for the series resistance and inductance have average values of 0.1 Ω and 160 pH respectively. Long dual-via chains were designed to evaluate their performance in insertion loss, delay and eye diagram. The insertion loss achieved with the longest dual-via chain was found to be less than 1 dB/cm up to 30 GHz with only a 6.2 ps delay in the TPVs, and the simulations indicate a wide open eye.

Electrical Modeling and Analysis of Tapered Through-Package via in Glass Interposers

“…Some of the published papers [1], [8]- [10] observed the phenomena of TPVs in glass, while other papers [11]- [14] failed to identify this taper effect. The simulated relative transmission results and the simulated crosstalk with frequency were presented for TPVs with various taper angles drilled by different methods [8], [9], and the exit via diameters were examined for various taper angles in the case of a fixed top diameter of 50 μm [1].…”

Microelectronics packaging technology roadmaps, assembly reliability, and prognostics

“…Through-package vias (TPVs) and re-distribution layers (RDLs) are two key building block technologies for glass interposer. The TPV technology was presented by J. Tong et al [26] covering detailed electrical modeling, design, and characterization using 3D glass interposers. High frequency characterization, up to 30 GHz, was presented for high aspect-ratio 55-µm diameter TPVs in 300-µm thin glass, formed by a novel focused electrical discharge method that is capable of greater than 1000 vias per second throughput.…”

High Reliability and High Performance 30μm Through-Package-Vias in Ultra-Thin Bare Glass Interposer

“…The approximated inductance of a single via can be retrieved from the reflection coefficient S 11 by the method described in [7]. The input impedance, converted from S 11 can be expressed as Z 11 = 2 (R + j2πfL), where R is the via resistance and L is the via inductance.…”