Reliability of thick Al wire: A study of the effects of wire bonding parameters on thermal cycling degradation rate using non-destructive methods

Abstract

Access from the University of Nottingham repository:http://eprints.nottingham.ac.uk/36483/1/Reliability%20of%20thick%20Al%20wire%20A %20study%20of%20the%20effects%20of%20wire%20bonding%20parameters%20on %20thermal%20cycling%20degradation%20rate%20using%20non-destructive %20methods.pdf Copyright and reuse:The Nottingham ePrints service makes this work by researchers of the University of Nottingham available open access under the following conditions. This article is made available under the Creative Commons Attribution Non-commercial No Derivatives licence and may be reused according to the conditions of the licence. For more details see: http://creativecommons.org/licenses/by-nc-nd/2.5/ A note on versions:The version presented here may differ from the published version or from the version of record. If you wish to cite this item you are advised to consult the publisher's version. Please see the repository url above for details on accessing the published version and note that access may require a subscription. AbstractThe effect of bonding parameters on the reliability of thick Al wire bond is investigated. Samples were prepared with 25 different designs with 5 different bonding parameters such as time, ultrasonic power, beginforce, end-force and touch-down steps (pre-compression) with 5 levels. The bond signals of ultrasonic generator were collected during bonding in order to obtain prior quality information of bonded wires. 3D x-ray tomography was then used to evaluate bond quality during passive thermal cycling between -55 °C and 125 °C. Tomography datasets were obtained from the as-bonded condition and during cycling. The results clearly show ultrasonic power, appropriate levels of begin-force and touch-down steps are all important for achieving a well attached and reliable bond. Analysis of the virtual cross-sections indicates a good correlation between the bond signal (i.e. the initial bond quality) and wire bond damage/ degradation rate. An improved understanding of the wire bonding process was achieved by observing the effect of the complex interaction of bonding parameters on the ultrasonic generator signals and degradation rate under thermal cycling.

Predicting Lifetime of Thick Al Wire Bonds Using Signals Obtained From Ultrasonic Generator

“…Our previous research confirmed that the current envelope of the electrical signal reflects the wire bonding machine parameters, and the correlation between the bond signal characteristics and the bond quality was confirmed by X-ray tomography images [11]. In this paper, this correlation between is examined for subtle change in bonding conditions, using a semisupervised learning algorithm.…”

“…In our previous work [11], we demonstrated a clear link between differences in bond quality arising from the changes in wire bonding parameters and the characteristics of the current envelope of the ultrasonic signals obtained from the transducer. In this paper, we examine whether the above method can be used to discriminate subtle quality differences arising from bonds made from the same parameters (e.g., as on a typical manufacturing line).…”

Thermal analysis of microwave GaN-HEMTs in conventional and flip-chip assemblies

“…There are two popular ways to assemble a discrete HEMT on a carrier: wire bonding and flip‐chip. The conventional wire‐bonding is more common; however, it suffers from several shortcomings such as the wire inductance effects, discontinuities, nonreproducible wire‐bonds, and low reliability of interconnects due to the thermo‐mechanical stress . Currently, the flip‐chip technique with electrical and mechanical bumping has become prevalent as an alternative method for conventional wire‐bonding assembly.…”

“…The conventional wire-bonding is more common; however, it suffers from several shortcomings such as the wire inductance effects, discontinuities, nonreproducible wire-bonds, and low reliability of interconnects due to the thermo-mechanical stress. [8][9][10][11] Currently, the flip-chip technique with electrical and mechanical bumping has become prevalent as an alternative method for conventional wire-bonding assembly. In this technique, transistor is mounted upside-down with bottom plate suspended in the air.…”

Evaluation of Ultrasonic Bonding Strength with Optoacoustic Methods

“…The bonding strength is often estimated with the bonded area. The bonded area was visualized by ultrasonic C-scan testing [12][13][14][15] and radiography [16,17]. In these studies, it was indicated that the relation between the bonded area and the bonding strength are linearly correlated.…”