Thermal characteristics of a four-chip magnetic bubble package

A thermal study was made of a magnetic bubble mass memory dual in-line package, which contains four bubble chips with a total memory capacity of 1/4 Mbits. The package consists of a number of component parts; and there are two groups of heat sources in the package distributed in the chips and in the driving coils. To determine the thermal characteristics of the bubble package, experiments were conducted to measure the transient and steady state temperature distribution of the package under certain natural convection conditions. It was found that the maximum steady state chip temperature rise over the magnet and the shield can may be expressed in terms of the total chip power, Qchipsand the total coil power, Qcoils, as , where Raiand Rbihave the dimension of thermal resistance and have been experimentally determined. The transient temperature distribution was measured from initial package temperatures of -50°C, 20°C and 90°C. Also, experiments were conducted to measure the transient temperature change from a steady state when the package was suddenly cooled by directed air jets. In all these cases the maximum temperature difference between the chips and the magnets at all times was determined, from which the deviation of the bias magnetic field from a desired value can be calculated from the temperature coefficient of the magnets and the garnet chips. This deviation is one of the factors that has to be taken into account in determining the minimum common margin between the high and low limits in which the bubble package can operate satisfactorily in the temperature range specified.