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This paper aims to investigate the root causes of and implement the improvements for the inter layer dielectric (ILD) crack for LQFP C90FG (CMOS90 Floating Gate) wafer technology devices in copper wire bonding process.

Failure analysis was conducted including cratering, scanning electron microscopy inspection and focus ion beam cross-section analysis, which showed ILD crack. Root cause investigation of ILD crack rate sudden jumping was carried out with cause-and-effect analysis, which revealed the root cause is shallower lead frame down-set. ILD crack mechanism deep-dive on ILD crack due to shallower lead frame down-set, which revealed the mechanism is lead frame flag floating on heat insert. Further investigation and energy dispersive X-ray analysis found the Cu particles on heat insert is another factor that can result in lead frame flag floating.

Lead frame flag floating on heat insert caused by shallower lead frame down-set or foreign matter on heat insert is a critical factor of ILD crack that has never been revealed before. Weak wafer structure strength caused by thinner wafer passivation1 thickness and sharp corner at Metal Trench (compared with the benchmarking fab) are other factors that can impact ILD crack.

For ILD crack improvement in copper wire bonding, besides the obvious factors such as wafer structure and wire bonding parameters, also should take other factors into consideration including lead frame flag floating on heat insert and heat insert maintenance.

This paper aims to combine the grooves with an annular air thrust bearing with multi-hole restrictors and discusses the influence of the groove parameters on the bearing performance.

Four models of aerostatic bearings with grooves of different geometries are established. The pressure distribution, load-carrying capacity (LCC), stiffness and flow characteristics of the flow field in the bearing clearances are obtained by computational fluid dynamics simulation.

The numerical and simulation results show that air bearing with grooved restrictors can slow down the pressure drop at the air inlet and increase the LCC and stiffness of the bearing. The gas flow in the aerostatic bearing is also studied, and the air vortex in the recess is analyzed.

This research optimizes the structure of the annular air thrust bearing, analyzes the gas vortex in the recess, improves the LCC and stiffness of the bearing and provides a reference for the bearing in the selection of groove parameters.

The peer review history for this article is available at: https://publons.com/publon/10.1108/ILT-01-2023-0006/

The purpose of this study is to evaluate the tannase-assisted extraction of tea stem pigment from waste tea stem, after which the stability of the purified pigment was determined and analyzed.

The extracting process was optimized using the response surface methodology (RSM) approach. Material-liquid ratio, temperature and time were chosen as variables and the absorbance as a response. The stability of the tea stem pigment at the different conditions was tested and analyzed.

The optimized extraction technology was as follows: material-liquid ratio 1:20 g/ml, temperature 50°C and time 60 min. The stability test results showed that tea stem pigment was sensitive to oxidants, but the reducing agents did not affect it. The tea stem pigment was unstable under strong acid and strong alkali and was most stable at pH 6. The light stability was poor. Tea stem pigment would form flocculent precipitation under the action of Fe²⁺ or Fe³⁺ and be relatively stable in Cu²⁺ and Na²⁺ solutions. The tea stem pigment was relatively stable at 60°C and below.

No comprehensive and systematic study reports have been conducted on the extraction of pigment from discarded tea stem, and researchers have not used statistical analysis to optimize the process of tannase-assisted tea stem pigment extraction using RSM. Additionally, there is a lack of special reports on the systematic study of the stability of pigment extracted from tea stem.