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Surface Finishing

Ultrasound Assisted Surface Finishing

Many surface coatings require the substrate to be etched in order to provide good adhesion. This process can be very difficult on polymer substrates such as polypropylene, ABS, PTFE and epoxy bonded carbon fibre. Typically these are very resistant to chemicals so only very aggressive / toxic compounds such as Chromic Acid are able to etch them. The alternative is physical abrasion such as sand blasting, but this is labour intensive and difficult to apply to certain shapes.

 Surface Finishing Image

The Susonence project is developing ultrasonically enhanced etching. Acoustic cavitation in a liquid due to ultrasound application causes asymmetrical collapse resulting in the production of a powerful microjet of liquid towards the surface. This can produce surface activation and surface cleaning through both chemical and mechanical attack, as well as improved heat and mass transfer. The result is etching with greatly reduced or even no chemical application. 

Ultrasound Assisted Surface Finishing Diagram


 

Surface coatings also benefit from the addition of ultrasound. Better mixing and mass transfer can provide a superior finish. Particular benefits can be seen where the composition of the coating is of great importance, for example tin/lead plating.

 

 Example Tin/Lead Plating


PCB

Ultrasound Assisted PCB Manufacturing

Hole preparation and metallization are critical processes in the creation of reliable plated through-holes and blind vias. Adhesives used in PCB manufacturing such as acrylic are susceptible to being drawn-out during drilling leaving a type of smear which causes problems on metallisation.

PCB image

The function of the desmear process is to remove the residues from the drilling process. It is also designed to create topography or micro-roughening of the resin to improve coating adhesion. Normally the process is achieved by permanganate or plasma treatment.

 

PCB Image

Fig 1 - Improved smear weight removal using permanganate with ultrasound

 

The Susonence project focuses on the improvements which can be gained by the use of ultrasound combined with the permanganate desmear process. Significantly more material can be removed with this technique, reducing the chemical use and the temperature. Consequently large cost savings and environmental benefits can be achieved. 

The use of ultrasound is also being applied to various other materials used in the PCB industry such as polyimide. The use of ultrasound in etching processes can reduce the chemical consumption required.

Env-Aqua Limited (UK)

Env-Aqua Solutions Ltd was formed in 2005 to integrate specific elements of environmental consultancy activities with turnkey design, manufacture and supply of plant and equipment strongly allied to pollution prevention and control via recovery based approaches. Within many of these activities Env-Aqua has worked on and managed many inter-disciplinary research and development projects, both within the UK and Europe.

Env-Aqua’s current client base includes Entec, Envirowise, BAeSystems, The Royal Mint, Xm Services (Michelin Environmental Group) and the Deutsch Group of companies. The company has 2 senior consultant staff with a current turnover of circa 300,000 Euros.

The company has over 25 years experience, primarily in the electronic and surface engineering industrial waste treatment and pollution control sector, and has been instrumental in the design, installation and promotion of waste minimisation and resource recovery systems and programmes, with a global industrial client base. They also supply high level technical and commercial consulting advice to the finishing, surface treatment and waste treatment sectors.

ENVAQUA has participated in many collaborative research projects funded by the UK agencies or the EU. Currently, the company is coordinating two collaborative projects in metal recovery and recycling in surface finishing operations, one EU-funded collaborative and one UK Government-funded.

Additional information