As a demand for electrical systems with a wide data bandwidth has increased, high-performance packages ensuring high data rates, such as low power double data rate series, have become common. The need for high-performance test sockets has also emerged to test these packages. However, a conventional pogo pin socket has a limited test bandwidth due to the parasitic components arising from its spring. On the other hand, a silicone rubber socket satisfies the wide bandwidth requirement because it has low parasitic components due to high-density conductive metal powders in an elastic silicone rubber. In this paper, we propose an RLGC equivalent circuit model of a silicone rubber socket and first experimentally verify it. The proposed model is experimentally verified in the frequency domain by comparing the insertion loss obtained from the proposed model to the measurement up to 20 GHz. The proposed model is experimentally verified in the time domain by comparing the eye diagrams obtained from the proposed model to the measurement at a data rate of 12.5 Gb/s. Also, the insertion loss of the sockets with varied height, diameter, and pitch is analyzed using the proposed model. The proposed model provides physical insight of a silicone rubber socket, and it allows to determine whether a socket is reliable for testing high performance packages in a short time. It also gives us the idea how to design a high-performance test socket. Furthermore, we discuss the current capacity and life cycle of the silicone rubber socket in terms of signal integrity as well.

High-Frequency Modeling and Signal Integrity Analysis of a Silicone Rubber Socket for High-Performance Package

In this paper, structural and electrical characteristic deviations of silicone rubber sockets are analyzed depending on external force based on its lumped RLGC model. Electrical performances heavily depend on compression rate of the silicone rubber socket. Thus, study on the structural and electrical characteristic deviations of the silicone rubber socket depending on external force is needed for reliable tests. The deviations are analyzed based on an assumption based simplified equivalent model of the silicone rubber socket. For verification, a 3D electromagnetic (EM) simulation program is used and its results are compared with that of proposed RLGC models in the frequency domain. The electrical performance of the RLGC model is nearly identical to that of 3D EM simulation result. In addition, the electrical performance of the compressed silicone rubber socket is also nearly identical to that of a solder ball when it is compressed at different compression ratio.

Analysis of external force dependent lumped RLGC model of high-bandwidth and high-density silicone rubber socket

Three-dimensional integrated circuits (3D IC) based on TSV (Through Silicon Via) technology is the latest packaging technology with the smallest size and quality. As a result, it can effectively reduce parasitic effects, improve work efficiency, reduce the power consumption of the chip, and so on. TSV-based silicon interposers have been applied in the ground environment. In order to meet the miniaturization, high performance and low-cost requirements of aerospace equipment, the adapter substrate is a better choice. However, the transfer substrate, as an important part of 3D integrated circuits, may accumulate charge due to heavy ion irradiation and further reduce the performance of the entire chip package in harsh space radiation environment or cause it to fail completely. Little research has been carried out until now. This article summarizes the research methods and conclusions of the research on silicon interposers and TSV technology in recent years, as well as the influence of high-energy heavy ions on semiconductor devices. Based on this, a series of research methods to study the effect of high-energy heavy ions on TSV and silicon adapter plates is proposed.

https://www.mdpi.com/2079-9292/7/7/112/pdf

TSV Technology and High-Energy Heavy Ions Radiation Impact Review

This paper, for the first time, proposes and verifies a new coaxial silicone rubber socket for high-bandwidth and high-density package test using a fabricated sample. In addition, this paper also characterizes and verifies the coaxial silicone rubber socket. Because of the proposed coaxial socket’s novel coaxial structure, the proposed socket successfully achieves the electrical performance improvement. For verification, we compare the proposed socket and the previous noncoaxial socket in time domain. The proposed socket has greater eye height and eye width in the measured eye diagram than those of the noncoaxial socket. Moreover, the slope in the eye diagram is also improved in the case of the proposed socket. Therefore, the measured eye diagram for the coaxial socket shows the improvement in electrical performances. This paper also characterizes the equivalent RLGC model for the coaxial silicone rubber socket. In order to verify the RLGC model, we compare the insertion losses and eye diagrams from measurement, 3-D electromagnetic simulation, and the proposed RLGC model, respectively. Their insertion losses are comparable up to 20 GHz. Furthermore, the obtained eye diagrams are almost identical at the data rate of 9.6 Gb/s. In conclusion, this paper successfully proposes, verifies, and characterizes a new coaxial silicone rubber socket for the first time.

High-Frequency Electrical Characterization of a New Coaxial Silicone Rubber Socket for High-Bandwidth and High-Density Package Test

In this paper, an RLGC model of a silicone rubber socket is proposed and compared with simulation results. Due to the reusability of the silicone rubber socket, it is suitable for a reliable test. In addition, its electrical performance is compared with that of conventional solder balls. The performance of the two are compared using measurements in both frequency and time domains. Their eye diagrams are nearly identical at the data rate of 28Gbps, which is the data rate of a single channel in a 100Gbps transceiver IC that consists of 4 parallel channels.

Modeling and measurement of high-bandwidth and high-density silicone rubber socket for 100Gbps transceiver IC test

For high-speed package testing, conductive rubber contactors become more and more promising because of its excellent RF performance. For electrical characteristic analysis of the conductive rubber contactor, the lumped equivalent circuit model of conductive rubber contactor based on its physical dimension and structure is proposed and verified with 3D field and SPICE simulation.

Michael Bae

Papers

High-Frequency Modeling and Signal Integrity Analysis of a Silicone Rubber Socket for High-Performance Package

Analysis of external force dependent lumped RLGC model of high-bandwidth and high-density silicone rubber socket

Modeling and analysis of a conductive rubber contactor for package test

High-Frequency Electrical Characterization of a New Coaxial Silicone Rubber Socket for High-Bandwidth and High-Density Package Test

Modeling and measurement of high-bandwidth and high-density silicone rubber socket for 100Gbps transceiver IC test