Wind power is expanding in Sweden as in many other countries. Varying wind power production may be a challenge for the electric power system to balance due to the intermittency. The paper studies three future scenarios of wind power expansion in Sweden and relates that to the current system power reserves located in each congestion area. Production from existing wind farms has been used to simulate future wind power production and variations. The variations that will be the largest challenge to handle are found in area four in South of Sweden, with small power reserves, big wind power expansion plans, small transmission capacity, and a limited smoothing effect due to the small area.

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Ultraviolet (UV) lasers can be used as microsurgery tools to deprocess electronic packages to expose the device and internal package features. A UV laser milling tool was characterized for various applications on multiple die stacked packages to assist in fault isolation and failure analysis. Laser milling procedures evaluated were package delayering to expose traces, trace cutting so that fails can be isolated between the die and package, wire bond exposure and cutting, multiple stacked die exposure through mold compound decapsulation and device milling. Results show excellent selectivity of the laser in removing organic material without etching copper traces at multiple layers in the organic package. Mold compound removal above the die was limited to within ~15 microns of the die surface to prevent any die damage. Mold compound decapsulation outside the die area to expose multiple layers of wire bonds for probing and inspection was developed after overcoming issues related to wire damage. In conclusion, laser milling procedures developed and evaluated show that the technique has a unique advantage in performing local package microsurgery with minimal damage or change in the global stress state of the package.

A laser spallation technique to measure the tensile strength of thin film interfaces is introduced. In this technique, a laser-generated stress wave of nanosecond duration in the substrate spalls off (completely removes) a coating deposited on the substrate’s front surface. The threshold laser energy is converted into the tensile stress (strength) at the failure site (usually the interface) by using an optical interferometer. Because of the ultra-short duration of the stress wave loading, all plastic deformation processes that usually accompany the coating decohesion event are suppressed such that the measured value can be regarded as fundamental or intrinsic to the material system (including the defects, if any). Application of this technique to test planar as well geometrically heterogeneous interfaces in IC’s, substrates, and packages is demonstrated. The technique is used to quantify the degrading effects of moisture and in-situ temperature rise on the tensile strength of a polyimide/Si3N4/Si interface system whose strength was systematically degraded by exposing the samples to controlled humidity (50-70% RH) conditions for varying duration (12-96 hrs) and temperatures (30°C-150°C). These measurements of strength degradation can now be used to predict device reliability from a fundamental standpoint in conjunction with simulations capable of predicting time-dependent stress concentrations, moisture accumulation, and temperature rise at critical interfaces during processing and service environment in actual systems.

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