Long Zhili

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.

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

Measurement of driving electrical signal and input impedance analysis of PZT transducer in thermosonic bonding

In thermosonic bonding process, the driving electrical signal and input impedance of PZT transducer reflect directly the bonding process between gold ball and substrate. This paper describes a method of getting the electrical signal of PZT transducer during the thermosonic bonding process, and analyzes the input impedance of PZT transducer based on the sampled data. From many experiment samples we find that, the driving voltage and current of PZT transducer are approximately 62 kHz sine wave; the range of the voltage is from 2 V to 8 V, and the current is only from 20 mA to 100 mA; the real bonding period is about 52ms. By PSD (power spectrum density) analysis to the electrical signal, we find that there are harmonics in the signal. At last, the paper uses the concept of generalized impedance to analyze the input impedance of PZT transducer during the thermosonic bonding process.

Study of prepress force on piezoelectric transducer of wire bonding

The friction contact model of ultrasonic propagation in wire bonding transducer is established. This paper studied piezoelectric driver structure. The relation of tighten moment and apply voltage is deduced. The wire bonding transducer scopes of tighten moment and apply voltage is reduced. It provides foundation for design and operating of wire bonding system.

Effect of Contact Interface in Transducer System in Ultrasonic Bonding

The effect of contact interface on ultrasonic energy propagation is the common problem of all kinds of ultrasonic transducer. In ultrasonic bonding, contact interfaces between different parts are nonlinear factors, so they affect directly the ultrasonic energy propagation and bonding quality. By using finite element method and laser Doppler vibrometer, the effect of contact interface on the ultrasonic energy and vibration are investigated. It is found that, incorrect contact interfaces cause multiple vibration models and mix certain resonance frequencies, induce non-stable output of the ultrasonic energy, and lead to hysteresis response. All these would cause some bonding shortcomings such as lower bonding strengths and chip tilting.

Effect of bonding pressure on transducer ultrasonic propagation in thermosonic flip chip bonding

As one of the key bonding parameters for thermosonic flip chip bonding, bonding pressure plays an important role for the bonding process. Moreover, as the load of the ultrasonic transducer system, bonding pressure affects directly the process of ultrasonic propagation, so it will influence the bonding quality. In this paper, in the condition that the bonding pressure was tuned regularly, the impedance characteristics of ultrasonic transducer were measured by a impedance analyzer, and the ultrasonic energy was measured by a laser Doppler vibrometer, and the shear bonding strengths at different bonding pressure settings were attained. It is shown that when the bonding pressure increases, the resonance frequency and resistance of transducer will increase, while the conductance and ultrasonic energy will turn down, and a stable and satisfied bondability can be found at a moderate pressure window. The impedance model for ultrasonic transducer was created by an equivalent circuit, and used to analyze the experimental effect of bonding pressure on ultrasonic propagation for transducer

Joint Time-Frequency Analysis of Capillary Tip Vibration in Thermosonic Wire Bonding

In thermosonic wire bonding process, the capillary of transducer is a critical component that contacts directly to the ball bump of IC chip, and its vibration characteristic is an important factor that affects directly the bonding quality. The aim of this investigation is to understand the vibration characteristics of capillary tip in thermosonic wire bonding. With laser Doppler non-contact measurement, vibration signal of capillary tip is picked up and analyzed by joint time-frequency analysis. The results show that, compared to pure time or frequency domain analysis, joint time-frequency analysis can more clearly and more completely reveal the dynamic vibration characteristics of capillary tip in joint time-frequency domain, including the shift of frequency, change of harmonic components and its corresponding energy in bonding process. Moreover, joint time-frequency analysis can be used to show success and failure in bonding