Brian Samuel Beaman

A novel elastomeric connector for packaging interconnections, testing and burn-in applications

Elasticon connectors have been developed for a wide variety of interconnection and test applications which include module-to-board, board-to-board interconnections; high density module, board and LCD testings; as well as chip/wafer testing and burn-in to produce Known-Good-Die. Depending on the applications, the Elasticon connectors can be fabricated into two basic types, the single-sided (integrated to a substrate) and the double-sided (interposer) structure. The single-sided structure, the Integrated Probe, is designed and fabricated for test and burn-in applications. The density, compliance, thickness, pattern and size of both the one- and two-sided structures can be easily tailored to meet the requirements of each specific application. The fabrication processes involve wire bonding, laser and polymer casting and curing. The electrical, mechanical and thermal properties of the connector have been fully characterized. To achieve high compliance with low contact force, a proprietary elastomeric material has been formulated to achieve not only high compliance but high thermal stability. The conductive element uses highly conductive, corrosion free, and oxidation resistant noble metals and their alloys. The reliability and durability of the elastomeric connector have been evaluated with mechanical cycling, thermal cycling, stress relaxation, outgassing, and temperature and humidity rest. The thermal stability of the connector, including both the polymer and the conductive element, has been measured to exceed the burn-in temperatures, which range from 125 to 180/spl deg/C.

New ball grid array module test sockets

New sockets have been-designed and fabricated for testing advanced BGA modules. The socket can easily be custom designed to match any BGA footprint, size and pitch. The socket materials, including the contact metallurgy, frame and the elastomeric materials, are capable of performing burn-in test at temperatures higher than 150/spl deg/C for a prolonged time in air. The compliance of the sockets are tailored to bring just enough contact force to penetrate the thin oxide layer on the solder without severely deforming the solder ball. As a result, low and stable contact resistance has been achieved with low contact force in repeated touch-down cycles. The contact force to solder balls ranges from 12 to 50 grams per contact at 10 mils displacement. The contact structure and geometry have been enhanced to allow for multiple module test cycles (>50000 life cycles) with negligible damage to the contact pads.

A new direction for elastomeric connectors

Elastomeric connectors are a relatively new technology compared with conventional connector systems. A wide variety of elastomeric connectors are available today to meet the interconnection requirements for many different electronic packaging applications. Multichip modules are one of the many applications that benefit from the high density interconnection capabilities of elastomeric connectors. The ELASTICON connector is a new high performance elastomeric connector that was developed to address some of the key limitations of existing MCM and land grid array connectors. The ELASTICON connector uses gold or gold alloy wires for the conductive elements embedded in an elastomer material. The size, shape and spacing along with the elastomer material properties can be tailored to specific application requirements. The processes that have been developed for fabricating the ELASTICON connector represent a new direction for elastomeric connector manufacturing. Besides LGA packaging applications, ELASTICON connectors can be used for board-to-board and cable-to-board interconnections as well as high density PCB and IC chip testing applications.<<ETX>>

Benchmark Testing of LGA Sockets for Server Applications

Recent trends for industry standard microprocessors show a transition from using micro PGA (pin grid array) sockets to using LGA (land grid array) sockets to meet the increased performance challenges for new server applications. These new industry standard LGA sockets use a hybrid construction with a solder ball connection to the printed circuit card and a compression connection to the contact pads on the bottom surface of the microprocessor package. Custom LGA sockets have been used for many years in high end server applications and provide improved electrical performance compared to these new hybrid LGA sockets. New LGA socket technologies continue to be developed to meet the variety of server application requirements. Benchmark testing has been performed on a variety of custom LGA sockets along with the hybrid LGA sockets used for industry standard applications. The benchmark testing includes evaluations of contact reliability performance, high speed electrical performance, and high current performance. The test hardware was designed to simulate the product application including the processor package construction, the printed circuit card cross section, along with the heat sink and retention hardware configuration. The results from the benchmark testing identify the limitations for various types of LGA sockets and provide critical insights for selecting the optimum solution for a given application.