Zhong Jue

The characteristics of ultrasonic vibration transmission and coupling in bonding technology

Ultrasonic vibration transmission is a very critical and complex problem in bonding equipment. In this paper, the transmitting model of ultrasonic vibration in ultrasonic transducer and capillary have been given out by utilizing the propagating mechanism of ultrasonic wave in elastic body. The ultrasonic vibration displacement and velocity of high frequency were measured by using the laser doppler vibrometer PSV-400-M2(1.5MHz), then the conclusion in theory have been proven. Ultrasonic vibration displacement (or velocity) and energy density increase with decreasing section in the transmitting process. The coupling characteristics of ultrasonic longitudinal-complex transverse vibration system are simulated by Matlab software. Vibration locus shapes driven simultaneously by the same frequency and different frequencies are elliptical (or circular) loci and rectangular (or square) loci respectively. Microstructure characteristics at bonding interface were observed by using scanning electron microscope (KYKY2800), and would be improved by coupling loci, thus bond strength and quality would be enhanced. An advanced bond pattern would be indicated. And we draw some conclusions that have important theoretical and practical significance for further research about thermosonic bond technology.

Experiment study of temperature parameter effect on bonding process and quality in thermosonic wire bonding

An experiment study of temperature parameter on bonding process and bonding quality in thermosonic wire bonding was performed in this paper. The experiment method was based on changing regularly bonding temperature and gaining the bonding strength by shearing gold ball joint by a high precision gauge. The experiment results and analysis can find out the relationship of bonding temperature and bonding strength, and get the temperature ultimate, favorite temperature window and bondability window at that bonding condition. Moreover, the experiment can find that the effect of temperature on impedance and power of PZT transducer in bonding process. These experiment phenomena and analysis results can be help to research on bonding parameters matching and optimization in thermosonic wire bonding.

Study of Ultrasonic Power Parameter on the Large Aluminum Wire Wedge Bonding Strength

During the large aluminum wire wedge bonding experiments, the PZT driver signal and the bonding shear strength was acquired as the indicator of ultrasonic power and bonding strength respectively. With those data, the relationship between ultrasonic and bonding strength was studied. The experiments result shows that in this papers research condition: 1) the ultrasonic power were effected by ultrasonic power ratio and other uncontrolled factors such asymmetric substrate quality, unstable restrict between wedge tool and aluminum wire and so on; 2) when ultrasonic power less than LOW, increase power will increase the bonding strength and decrease the fail bonding; on the contrary, when ultrasonic power greater than 1.6W, increase power will decrease the bonding strength and increase the fail bonding; only when ultrasonic power between LOW and 1.6W, can stable and high yield bonding be reached

Vibration Simulation of Transducer System in Thermosonic Wire bonding

The vibration simulation model of transducer system in wire bonding was established by mechanical finite element method and verified by electric sine sweeping exciting method. The results show that, transducer system of wire bonder works with its second combination vibration mode that includes three nodes axial vibration of concentrator and one node radial vibration of capillary. There are many other undesirable modes that may be excited because they are very close to working frequency. These undesirable modes would waste ultrasonic energy and badly influence to bonding quality between gold ball and substrate, so they should be well controlled in bonding. Good agreement between simulation and experimental result was obtained, where the computed error of working frequency is only 1.2%. The research result can be used in performance study and design of an ultrasonic transducer

Experimental Studies of Frequency Characteristic on Transducer Power Supply and Vibration System in Ultrasonic Bonding System

PZT transducer works on its nature frequency in the process of ultrasonic wire bonding. Its actual frequency characteristic needs to be investigated for best performance. A direct digital synthesizer (DDS) was used to sweep frequency for output transformerless (OTL) power amplifier. Actual input and output voltage of OTL power amplifier component was acquired and analyzed. The experiment shows that OTL power amplifier component can be regarded as a linear system and that transfer function for this component also can be obtained with the data processing. This paper studied the influence of the bonding tool also. Deflection vibration of the tool has changed dynamical characteristics of the transducer system

Characteristic Comparing between Thermosonic Flip Chip Bonding and Reflow Flip Chip

Ultrasonic features in bonding area are of interests for researchers in the field of microelectronics packaging. In this study, the interface characteristics of bonding were detected by using XD7100 X-ray, the velocity of ultrasonic vibration at bonding tool was determined with a PSV-400-M2 high frequency (1.5 MHz) laser Doppler vibrometer, micro- characteristics of the specimens of thermosonic flip chip bonding were inspected by using a high resolution transmission electron microscope. Results show that bubbles at the interfaces of reflow soldering flip chip were observed, however they were not discovered during thermosonic flip chip, the interface characteristics of thermosonic flip chip is better than that of reflow soldering flip chip. The acceleration of the ultrasonic vibration was about 500000 m/s2 for a 62.73 kHz bonding frequency. This strong mechanical effect activates dislocations in the metal crystalline lattice and enhances atomic diffusion across the bonding interfaces, and these differ from melting mechanism of reflow soldering.

Effect of technological parameters on optical performance of fiber coupler

To find out the influence of technological parameters on optical performance of fused optical fiber device, the fiber coupler was served as subject investigated by using the fused biconical taper machining as experimental setup. Fused fiber coupler’s optical performances such as insertion loss, excess loss, directivity and uniformity were tested with the optical test system that was constituted of tunable laser and optical spectrum analyzer. Especially the relationship between optical performance and drawing speed was investigated. The experimental results show that the optical performance is closely related to process conditions. At fused temperature of 1 200 °C, there exists a drawing speed of 150 μm/s, which makes the device’s performance optimum. Out of this speed region, the optical performance drops quickly. At drawing speed of 200 μm/s, the excess loss is relatively small when the fused temperature is above 1 200 °C. So the technological parameters have close relationship with optical performance of the coupler, and the good performance coupler can’t get until the drawing speed and fused temperature match accurately.

Experimental measurement and numerical analysis of fused taper shape for optical fiber coupler

To find out the effect of the shape of fused taper region on the optical fiber coupler, the fiber couplers were fabricated at different drawing speeds with a six-axes fiber coupler machine. The results, which were obtained from the shape of fused taper region measured with microscope, show that there is a close correlation between the cone angle and optical performance of fiber coupler. High-performance fiber coupler cannot be obtained until rheological shape is controlled accurately. The numerical analysis model, which was built based on generalized Maxwell viscoelastic theory, is resolved with ANSYS software. The calculated results accord with the experimental data. It can apply a theoretic basis for forecasting the shape of fiber coupler fabricated under the conditions of different technological parameters.

Devitrification behaviour of rapidly solidified Al87Ni7Cu3Nd3 amorphous alloy prepared by melt spinning method

Rapidly solidified Al87Ni7Cu3Nd3 amorphous alloy was prepared by using melt spinning. Its calorimetric behavior was characterized by using differential scanning calorimeter in a continuous or isothermal heating mode. phase transformation was investigated, with a special interest in primary crystallization, by using an in-situ examination of X-ray diffractometry (XRD) and high resolution transmission electron microscopy (HRTEM). The results show that, the whole devitrification of rapidly solidified Al87Ni7Cu3Nd3 amorphous alloy involves two main processes of primary crystallization and secondary crystallization that consist mainly of two reactions. For primary crystallization, the apparent activation energies, EIso and EKis and growth activation energies Eg are about 153, 166 and 288 kJ/mol, respectively. The interdiffusion of Al atoms is a rate-controlled step of formation of the α(Al) particles, but slow diffusion of Ni and Nd atoms plays a significant role in retarding growth of the α(Al) particles. For secondary crystallization, EIso, EKis and Eg of the first reaction are about 291, 208 and 290 kJ/mol, and those of the second reaction are about 367, 269 and 372 kJ/mol. The two reactions of secondary crystallization are controlled mainly in an interface-controlled three-dimensional mode, depending mainly on slow diffusion of Ni and Nd atoms.

Novel manufacturing method of optical fiber coupler

Based on the coupling mode theory that the coupling ratio of fiber coupler changes periodically with center distance of two optical fibers, a novel manufacturing method of optical fiber couplers was developed with fused biconical taper experimental system. Its fabrication process is that the fiber is fused but not stretched when light begins to split, and the reduction of diameter of fiber is dependent on the rheological characteristic of the fused fiber-glass. The performance of the coupler was tested. The results show that the performance of the novel optical fiber coupler meets the performance expectations, and its diameter of coupling region (about 30 µm) is twice as long as that of classical fused biconical taper coupler (about 16 µm), so the default, that is, the device is easy to fracture, is restrained and the reliability is greatly improved.