An inverse problem motivated by the nondestructive testing (NDT) of adhesively bonded structures used in the aircraft industry is studied. Using transmission line theory, a model is developed which, when supplied with electrical and geometrical parameters, accurately predicts the reflection coefficient associated with such structures. Particular attention is paid to modelling the connection between the structures and the equipment used to measure the reflection coefficient. The inverse problem is then studied and an optimisation approach employed to recover these electrical and geometrical parameters from experimentally obtained data. In particular the approach focuses on the recovery of spatially varying geometrical parameters as this is paramount to the successful reconstruction of electrical parameters. Reconstructions of structure geometry using this method are found to be in close agreement with experimental observations.
This paper is concerned with the detection of environmental ageing in adhesively bonded structures used in the aircraft industry. Using a transmission line approach a forward model for the reflection coefficients is constructed and is shown to have an analytic solution in the case of constant permeability and permittivity. The inverse problem is analysed to determine necessary conditions for a unique recovery. The main thrust of this paper then involves modelling the connector and then experimental rigs are built for the case of the air-filled line to enable the connector parameters to be identified and the inverse solver to be tested. Some results are also displayed for the dielectric-filled line.
MCC has been developing the use of flashlamp pulsed Nd:YAG laser technology to bond TAB leadframes to bumped IC die. With basic equipment, the process has been proven in a laboratory scale environment. As a result, MCC recently licensed a vendor to manufacture the equipment so that it can be used in prototype and later in production environments. This project was initiated to develop a benign alternative for thermocompression gang bonding, particularly for applications where IC bond pads would be located over active circuitry. In addition, because the laser beam's positions are computer controlled, the process has shown to be very desirable for bonding conventional devices with peripheral pads, especially in high product mix applications. Bond rates of 40 bonds/second have been demonstrated at MCC. The first production prototype will bond at 60–80 bonds/s and it is anticipated that, with further development, the full production equipment will bond at 200 bonds/s. The process that is most mature at the time of writing is for bonding tin plated copper leads to gold bumps. This system allows formation of reliable bonds because the formed bonds consist primarily of copper and gold. The bonds are at least as strong and reliable as with other methods of TAB bonding. Bonds with this metallurgical system have been subjected to severe environmental testing without failure. This paper will present results of laser inner lead bonding, the equipment used to develop it and the expectations of the future equipment as well as the future of the technology itself.
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