The project deals with the effect of the airflow and temperature on the gold wirebond due to possible application in hot-wire anemometry. Theoretical fundamentals of wirebonding and hot-air anemometry are included in the text. From the area of anemometry, there is also a detailed description of measurement principles, areas of application and measuring instruments. The practical part of the text deals with design of the experimental sensor for hot-wire anemometry with use of the gold wirebond, including also the verification of the sensor's properties.

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The thesis summarizes the basic knowledge of Wirebonding. It also closely studying the various influences on the final shape, strength and reliability of the bonds. In the experimental part are found the optimal settings of various wire bonders. For wire bonder TPT HB-10 are found the optimal settings for different types of surfaces, which were contacted.

The first part of this dissertation explores the chemistry of an inhibitor complexation with Cu. First, the Cu oxidation state of the complex was +1. Second, identified by differential RAIRS, one source of Cu(I) for the Cu(I)-inhibitor complex could be Cu(I) oxide. The characteristic Cu(I) oxide peak at 650 cm⁻¹ was observed to decrease after CVD coating process was applied. This led to a major hypothesis that in order for the reaction between Cu(I) oxide and the inhibitor to proceed, protons from the inhibitor and oxygen from Cu₂O are stabilized by reacting to form water. The applicability of the passivation nature of Cu(I)-inhibitor films was explored for Cu-Al wire-bonded devices in its ability to protect from Cu-Al peripheral galvanic corrosion and the galvanic corrosion of the Cu-Al intermetallic compounds in their roles for corrosion-induced liftoff. The second part of this work studied the effect of replacing Al bond pad with Cu on the corrosion induced liftoff of wire-bonds when exposed to low ppm levels of chloride contamination. Applying protective coating to the Cu pad surface before wire-bonding was found to suppress the thermally induced oxidation of Cu in air, helping to enable successful Cu-Cu direct wire-bonding. Compared to Cu-Al devices with passivation coating, which has a few wires liftoff with 6 hours, the Cu-Cu bonded devices survived much longer, over 40 days, with almost no liftoff observed. This demonstrates that removing the galvanic contact, the root cause of the corrosion induced failure, is a more robust and permanent solution to the corrosion experienced by these devices.

With increasing miniaturization in microelectronics the wirebonds used in IC packages are witnessing a thrust towards fine pitch wirebonding. To have a precise control over loop height of the wirebond for fine pitch wirebonding, it is imperative to do mechanical characterization of the wirebond. The present work studies the mechanical properties of gold wire and wirebond using nanoindentation. The wirebond specimen surface was planarized using mechanical polishing. The loop height of the gold wirebond is directly proportional to the length of the heat affected zone (HAZ) above the ball of gold wirebond. Metallographic preparation of gold wirebond cross section reveals the presence of undesirable coarse grain structure in HAZ due to recrystallization and grain growth in the gold wire adjacent to the ball. The recrystallization temperature of our gold wire was found using D.S.C. to be 340.66°C. The doping elements present in the gold wire used, were identified using TOF-SIMS. Nanoindentation of the gold wire was done at different maximum loads to observe the hardness variation with load. The nanoindentation of gold wirebond has confirmed a v-shaped hardness profile in the HAZ. The hardness minima for the particular gold wire used with a ball size ratio of 2.4 was observed at distance of 160-170 µm from the neck of the ball. The elastic modulus was found to vary randomly and to be independent of the microstructure in the wirebond. A yield stress profile based on empirical hardness-yield strength correlation has been predicted for the gold wirebond. / Singapore-MIT Alliance (SMA)