Due to the arrayed nature of the Computed Tomography (CT) Detector, high density area array interconnect solutions are critical to the functionality of the CT detector module. Specifically, the detector module sensor element, hereby known as the Multi-chip module (MCM), has a 544 position BGA area array pattern that requires precise test stimulation.
A novel pogo-pin block array and corresponding motorized test socket has been designed to stimulate the MCM and acquire full functional test data. The pogo-pin block design has specific features which capture and guide the pogo-pins while still allowing for easy pin replacement at the test vendor. In addition, the socket design includes many unique design elements, including built-in protection for the pogo-block from user access, thermal control considerations, and stop features to prevent over clamping. Additional mechanical design features to blind-engage a flexible circuit with the MCM will be discussed. The entire socket and pogo-block system is replicated to create a multi-socket tester that is currently deployed at the OEM vendor.
This test system enables full characterization of the MCM including gain connectivity testing and full linearity testing of the device. Various additional aspects of the test system will be discussed, including software control of the socket and data collection of the entire signal chain. This type of test socket architecture can be a model industry example for in-circuit test as well as for final functional testing of a BGA type device.
Overall the MCM injection tester had significant design challenges that were explored in this paper, including pogo pin design, socket mechanical considerations, and socket reliability. The concepts of an integrated pogo-block and motor driven gear socket assembly can be leveraged for test systems that need precise alignment and consistent force. In addition, reliability aspects of the test socket were explored in detail, showing the test system is capable of surviving over 60,000 cycles. Lastly, the tester graphical user interface was shown to outline how the overall test sequence behaves. This test system can be used as a model example for other equipment manufacturers who face similar high density signal interfaces that require precise alignment and accurate clamping.
Initially Published in the IPC Proceedings