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The purpose of this paper is to develop an optimised sonochemical surface modification process which could be operated at low temperature and which uses non‐hazardous chemistry with short treatment times. A range of sonochemical parameters such as ultrasonic intensity/power and process temperature were investigated.

A 20 kHz ultrasonic probe was used as the ultrasonic source. Ultrasound was applied through deionised water (DI) to sonochemically surface modify a high Tg epoxy laminate material (Isola 370 HR). The efficiency of the sonochemical surface modification process was determined by weight loss, roughness, adhesion and scanning electron microscopy (SEM).

This study has confirmed that ultrasound has the ability to surface modify a high Tg epoxy substrate material (Isola 370 HR). Weight loss and roughness values were increased by using an optimised ultrasonic process compared to control samples which were processed under “silent” conditions. Adhesion testing showed an improvement in the adhesion level between the surface and the subsequently electroless plated copper.

Surface modification of high Tg materials generally utilizes wet chemical methods. These processes involve using hazardous chemicals, high temperatures, require high volumes of water for rinsing and need relatively long immersion times. This research has shown that by optimising ultrasonic parameters, surface modification can be brought about in deionised water (DI) at low temperature.

To build on the results detailed in the previous paper where it was shown that sonochemical surface modification could be achieved in water. This paper aims to look at one of the factors affecting sonochemical surface modification, namely the ultrasonic source to sample distance.

Ultrasound was applied through deionized water for the surface modification of three materials: a high Tg PCB laminate (Isola 370HR), a polyphenylene ether – polystyrene polymer (Noryl HM4025) and an acrylonitrile‐butadiene‐styrene/polycarbonate (Cycolac S705). The efficacy of the treatment was determined by weight loss, scanning electron microscopy, contact angle, roughness and tape testing after electroless copper plating.

The study confirmed, and extended the previous findings, that a range of substrates could be sonochemically surface modified in water, even though in this work the ultrasonic horn had a larger tip size and produced a different ultrasonic intensity. Although the results were material dependent, the ultrasonic source to sample distance was found to be critical. Employing a spacing of 5 mm produced samples which generally exhibited higher weight loss, roughness and significant changes in surface morphology than when a distance of 25 mm was utilized.

The paper demonstrates that sonochemical surface modification has the potential to be a much more sustainable surface modification process than those currently employed in the electronics industry. However, to achieve this outcome acoustic cavitation and factors affecting it (such as source to sample distance) must be understood so that suitable equipment can be built.

This paper sets out to give an introduction to sonochemistry and the effects brought about by the application of ultrasound that might be useful in surface modification; and to show the feasibility of sonochemical surface modification in water on a range of materials employed in electronic manufacturing.

Ultrasound was applied through DI water for the surface modification of four materials: a ceramic, a polyphenylene ester (polystyrene polymer (Noryl HM4025)), an acrylonitrile‐butadiene‐styrene/polycarbonate (ABS/PC‐Cycolac S705), and an FR4 laminate (Isola Duraver 104). The efficacy of the treatment was determined by weight loss, scanning electronic microscopy, contact angle and roughness.

Ceramic and Noryl materials can be surface modified sonochemically in DI water. Weight loss results suggested that, this was also the case for the Duraver laminate but the ABS/PC substrate was least affected by treatment in an ultrasonic field under these benign processing conditions.

Traditional “wet” surface modification techniques often use hazardous chemistry, high‐process temperatures, copious rinsing and long dwell times. This research programme addresses these issues by evaluating sonochemical surface modification techniques with the objective of producing a one‐step process using benign chemistry at lower temperature with less rinsing.