Background, Motivation and Objective
Ultrasonic bonding is important in today’s microelectronics manufacturing. Small deviations to the designed profile in the bonding tool’s working surface increase the number of low quality bonds. High yield is important in applications such as single-point Tape Automated Bonds (spTAB) in the CERN-ALICE detector or wire-to-wire bonds in the ESA-Electric Sail. We have developed a
method to measure the profile of the bonding tool’s working surface and its wear during the bonding process in order to increase the yield.
Statement of Contribution/Methods
Scanning White Light Interferometry (SWLI) is an interferometric method that measures 3D surface profiles. Using a broadband light
source SWLI can interrogate step heights up to several millimeters with nanometer scale vertical resolution.
We measured profiles of spTAB tools. The tools’ working surface should have two perpendicular grooves with uniform depth along
their length. SWLI measurements showed that some tools featured deviations in groove depth (Fig. 1). We also measured 3D profiles
of bonds made with such a non-spex tool and measured their strength with destructive pull force tests. These bonds featured a height outside the specifications (7 ± 1 μm), and were weaker than those made with an in-spex tool, which featured a maximum sustainable pull force of 12 ± 1 g.
Discussion and Conclusions
SWLI can characterize the accurate topology of the working surface of bonding tools with nm scale resolution in a few seconds. This
allows on-the-fly measurement of ultrasonic bonding tools used for high-end applications. It could be used either for quantitative
quality control when fabricating tools or to check tool wear during usage when bonding a large number of wires.
|Titel på värdpublikation||2010 IEEE International Ultrasonics Symposium|
|Status||Publicerad - okt. 2010|
|MoE-publikationstyp||A4 Artikel i en konferenspublikation|
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