Effect of electrode pattern on the outputs of piezosensors for wire bonding process control

A polyvinylidene fluoride (PVDF) piezosensor was installed as an integral part of an ultrasonic wire-bonding transducer for measuring bonding parameters, such as impact force, ultrasonic amplitude, and bond time. Four different types of electrode patterns were used to optimize the sensor outputs. When the ring-shaped electrode of the sensor was subdivided into four different sections, namely the top, bottom, left, and right sections, different output signals were observed during the wire-bonding process. The top section of the sensor was more sensitive to the impact force while the left and right sections could track the changes in the ultrasonic amplitude proficiently. This sensor has good potential to be used in an in situ automatic wire-bonding process-control system

Cymbal actuator fabricated using (Na0.46K0.46Li0.08)NbO3 lead-free piezoceramic

(Na0.46K0.46Li0.08)NbO3 (NKLN8) lead-free piezoceramic was prepared by a mixed oxide route. The ceramic showed a single phase of orthorhombic perovskite structure at room temperature and a high Curie temperature of ∼430∘C. A cymbal actuator using NKLN8 as the actuation element and titanium alloy as the endcaps was fabricated and characterized. A similar actuator with traditional Pb(Zr,Ti)O3 (PZT) piezoceramic was also constructed for comparison. The results showed that the NKLN8 actuator has a higher fundamental resonance frequency of 107.1 kHz and a faster response of 9.3 μs with a comparable effective coupling coefficient of 0.15 at the expense of a lower strain coefficient of 1.9 nm/V. The observed actuator performance was discussed in relation to the ceramic properties

Improvements in Au wire bondability of rigid and flexible substrates using plasma cleaning

Thermosonic Au wire bonding is the most widely used interconnection technology in the BGA packages. Compare with Au ball bonding, the lower wire loop and finer bond pitch of Au wedge bond makes its ideal for low profile and high I/O applications, which is the subject of the current study. As bond pad surface cleanliness, substrate materials and wire bonding process parameters play a critical role on the yield of wire bonding, this study compare Au wedge wire bondability of rigid FR-4 and flexible polyimide (PI) substrate and examine the bonding improvements using plasma cleaning by the concept of process windows. Process windows demonstrate the bondability of the substrates at a combinations of varies bonding conditions, such as bonding temperature, bond power and with and without subjected to plasma cleaning. The plasma cleaning condition is optimized based on the process windows. Results indicated that a low plasma cleaning power with a short cleaning time resulted in the widest process window. Significant improvements of bondability were noted after plasma treatment with a substantial reduction in minimum bonding temperature for both substrates. The process window for the flexible substrate was much wider than the rigid substrates in the bonding conditions tested. © 2005 IEEE