Thermal cycling was performed in a Thermotron SE600 3 3 environmental chamber. This unit is capable of achieving chamber temperatures as high as 191 C and as low as ?87 C. Heating and cooling are achieved by forced air convection. In order that the chamber operates at peak efficiency, it is important that the airflow in the chamber is disrupted as little as possible. Airflow in the chamber is directed from top to bottom and for this reason, the boards are placed vertically in the chamber. All the boards are placed on a single wire shelf mounted halfway up the chamber. The boards are arranged in two parallel columns of ten panels each. The relative position of each board is shown in Figure 2. To hold them vertically, each row of boards is held in two parallel, notched aluminium holders. Each board is mounted so that the 50-pin connector attachment area (connectors are not populated) and ribbon cable are uppermost.

Figure 2: Schematic of the test board layout within the temperature chamber

In order to attach to the event detectors, the ribbon cables are passed through a side access port mounted at approximately the same height as the shelf. To prevent disruption to the airflow of the chamber and so as not to prove a hindrance whilst loading other boards, the ribbon cables are threaded straight down through the wire shelf and run across the bottom of the chamber before passing back through the shelf and out of...