ESA’s Science Payload Validation laboratory is developing a new type of detector characterisation bench, designed to cope with new challenges set by future instrument requirements and newly developed detectors. This new bench can accommodate large format detector up to 4kx4k 10um pitch or at least two 2kx2k 15um pitch side by side, it enables measurement in the 300 to 4000nm wavelength range, and can bring the detector temperature down to 20K. Its concept, based on lessons learned accumulated over the last 10 years, enables light and dark measurements to be performed in a single configuration reducing handling and optimising testing time in test campaigns. This contribution provides a general overview of the bench concept and main features. It details the main design challenges and describes the corresponding opto-mechanical and thermal design solutions, validated by early commissioning results.
Under an ESA contract, Leonardo UK developed the IBEX detector also referred to as LAPD for Large-format Avalanche Photo Diode array. Leonardo’s packaging solution relied on a chip-on-board solution incompatible with technical and performance requirements of ESA characterization campaign and experimental setup. An in-house solution has been developed, with ESA responsible for the design, manufacture, and test. And Leonardo responsible for gluing the device to the carrier and the wire bonding. ESA’s packaging solution relies on molybdenum carrier and two flexible PCB cables. The design, manufacturing, testing, and assembling of the various components of the LAPD package assembly entailed a variety of design iterations, tests, and trials. The material choice was a compromise between optimal CTE mismatch of Invar 36 and excellent thermal conductivity of TZM molybdenum (TZM = 0.5% titanium, 0.08% zirconium, 0.02% carbon). TZM molybdenum was chosen, and it was decided to verify the behavior by test. A thermal-vacuum test campaign showed that a mounted ROIC survives test representative conditions i.e., various thermal cycles between 20 and 200K. The gold coating of the molybdenum carrier is a real challenge, we will report on lessons learned. Similarly, the flexible PCB cables gluing to the carrier performed in-house is a delicate exercise. The flex cables are bonded to molybdenum blocks which are permanently mounted in a recess in the back of the carrier. Several trials were done for the mounting until successful result was reached. A sequence of thermal cycles between 20 and 200K were performed and showed no evidence of failure throughout the bond line between the block and flex cable. A handling jig was designed to fit Leonardo’s bonding setups for the die mounting and wire bonding. The handling jig is also used to safely mount the device in an in-house designed transportation and storage container.
ESA’s Science Payload Validation section (SCI-FIV) is developing a new detector test bench to expand its existing suite of test facilities and enable the characterisation of larger detectors (4k x 4k 15 μm pitch devices), sensitive over the visible to mid-wave infrared wavelengths (300-4000 nm) and at colder temperatures (down to 20 K). In this contribution we describe the main requirements of the bench, the novel mechanical and thermal concepts of the modular cryostat, as well as the requirements of the readout electronics chain, including a new detector controller. We also present ESA’s package and flex design for Leonardo’s LAPD (Large-format Avalanche Photo Diode array) device, the first detector to be tested with this new bench.
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