Application research on the time–frequency analysis method in the quality detection of ultrasonic wire bonding

Imperfection in a bonding point can affect the quality of an entire integrated circuit. Therefore, a time–frequency analysis method was proposed to detect and identify fault bonds. First, the bonding voltage and current signals were acquired from the ultrasonic generator. Second, with Wigner–Ville distribution and empirical mode decomposition methods, the features of bonding electrical signals were extracted. Then, the principal component analysis method was further used for feature selection. Finally, an artificial neural network was built to recognize and detect the quality of ultrasonic wire bonding. The results showed that the average recognition accuracy of Wigner–Ville distribution and empirical mode decomposition was 78% and 93%, respectively. The recognition accuracy of empirical mode decomposition is obviously higher than that of the Wigner–Ville distribution method. In general, using the time–frequency analysis method to classify and identify the fault bonds improved the quality of the wire-bonding products.

Cell Interconnections in Battery Packs Using Laser-assisted Ultrasonic Wire Bonding

This paper presents the results of a series of bonding tests using a laser-assisted ultrasonic wire bonding process. Aluminium and copper wire, both 500 μm (20 mil) thick, were bonded to nickel-coated steel caps of type 21700 battery cells. Mechanical bond strength tests prove that laser-assisted wire bonding has significant advantages over room temperature wire bonding. For example, it can be used to reduce the process time with aluminium wire or to increase the bondability of copper wire on nickel-coated steel. The results show a direct relation between tool tip temperature and measured bond strength. The quality of the joints was effectively improved by heating the tool tip up to 430 °C. These advantages are the same as in classic thermosonic wire bonding, but without the major disadvantage of having to heat to whole package. The cell temperature was shown to remain safely below the critical 60 °C in any application.

Recent Progress in Transient Liquid Phase and Wire Bonding Technologies for Power Electronics

Transient liquid phase (TLP) bonding is a novel bonding process for the joining of metallic and ceramic materials using an interlayer. TLP bonding is particularly crucial for the joining of the semiconductor chips with expensive die-attached materials during low-temperature sintering. Moreover, the transient TLP bonding occurs at a lower temperature, is cost-effective, and causes less joint porosity. Wire bonding is also a common process to interconnect between the power module package to direct bonded copper (DBC). In this context, we propose to review the challenges and advances in TLP and ultrasonic wire bonding technology using Sn-based solders for power electronics packaging.

Process advantages of thermosonic wedge-wedge bonding using dosed tool heating

Thermosonic wire bonding has a number of advantages over “cold” ultrasonic wire bonding. Despite these potential advantages, it is rarely used besides ball-wedge and gold wedge-wedge applications, mostly due to the drawbacks and limitations of available heating technology. A recently introduced novel thermosonic process using a laser-heated bonding tool avoids most of these drawbacks. This contribution presents the results of two series of bonding tests which have used this novel process to bond aluminium and copper heavy wire to sheets of the same metal. The bond test results prove that thermosonic wedge-wedge bonding with a laser-heated tool has a number of significant advantages in both aluminium and copper wire bonding. It can be used to reduce the process time, to decrease the mechanical stress in the substrate by reducing ultrasound vibration amplitude and/or normal force, and to increase bond strength. These advantages are the same as in classic thermosonic wire bonding, but without the major disadvantage of having to heat to whole package. Because of the high thermal conductivity and capacity of the investigated metal sheet substrates, the observed positive effects of a heated tool are expected to be significantly higher on real-world substrates such as power semiconductors.