Click to edit Master title style C-Tech Innovation Profitable Growth through Innovation Stuart Dalrymple Ultrasound as an enabling technology for sustainable electronic manufacturing

Click to edit Master title style Ultrasound as an enabling technology for sustainable electronic manufacturing Dr Andrew Cobley

Click to edit Master title style Agenda 1.Surface Modification in Electronic Manufacturing Problems associated with traditional methods 2.What is Sonochemistry? Acoustic cavitation Advantages for surface modification 3.Sonochemical Surface Modification Preliminary work Optimisation Conclusions 4. TSB project 5. Eco-Innovation project

Click to edit Master title style Traditional Wet Chemical Surface Modification SubstratesChemistryHazards PCBs, MIDs other polymers Solvent SwellVOC, flammable PCBs, MIDs other polymers Alkaline Permanganate Highly caustic, strong oxidant ABSChromic acidCarcinogenic, highly acidic Ceramics, glass Hydrofluoric acid Causes burns, targets bone Hazardous Chemistry VOCs, carcinogens, corrosive Environmental and health and safety legislation High Waste Treatment costs

Click to edit Master title style Traditional Wet Surface Modification Summary Traditional surface modification processes characterised by….. Long process times High temperature baths High water usage Hazardous chemistry CAN SONOCHEMISTRY HELP ?

Click to edit Master title style Sonochemistry The effect of sound on the chemistry of a solution

Click to edit Master title style Sonochemical Surface Modification Acoustic Cavitation

Click to edit Master title style boundary layer solid surface Acoustic Cavitation in a liquid NEAR A SURFACE UNSYMMETRIC COLLAPSE Inrush of liquid from one side of the collapsing bubble produces powerful jet of liquid targeted at surface Thinning of diffusion layer Surface Cleaning Surface activation Improved mass and heat transfer Thinning of diffusion layer Surface Cleaning Surface activation Improved mass and heat transfer Video courtesy of University of Twente, Netherlands. and Shimadzu Europa GmbH, Duisburg, Germany Microjetting/Microstreaming

Click to edit Master title style Sonochemical Surface Modification Microjetting –Mechanical/physical attack of surface –Scrubbing/cleaning action –Destruction of boundary layers –Movement of reactants to, and products/debris away from, the surface Extreme temperatures and pressures –Chemical/oxidative attack of the surface due to oxidative species –Breaking of bonds on surface of material –Chemical reactions on surface

Click to edit Master title style Sonochemical Surface Modification Original Research Concept Use ultrasound to make existing surface modification processes more sustainable Reduce chemical concentrations Reduce process times Reduce temperatures 3 year Platform study funded by

Click to edit Master title style Sonochemical Surface Modification Isola 370HR – Tg 180 ºC Materials Tested Cycolac S705 – ABS/PC Noryl HM4025 – Polyphenylene ester / polystyrene Courtesy of Moulded Circuits Ceramic Material

Click to edit Master title style Sonochemical Surface Modification of Ceramic 30 minutes HF Etch 1 minute HF Etch 1 minute Sonication in Water, 20 kHz 30 minutes Sonication in Water, 20 kHz

Click to edit Master title style Sonochemical Surface Modification in Water 20 kHz Horn, 29.3 W / cm 2, 60 minutes in DI Water, 40 ºC Isola 370HR as received x500 After Sonication x500 Noryl HM4025 as received x500 After Sonication x500

Click to edit Master title style Optimization of Ultrasonic Frequency Sonochemical Surface Modification in Water Optimization of Ultrasonic Frequency Noryl HM4025, 40 ºC, 30 minutes

Click to edit Master title style Sonochemical Surface Modification in Water Optimization of Ultrasonic Intensity at 20 kHz Effect of Ultrasonic Intensity on Weight loss for Noryl HM kHz, DI Water, 40 ºC, 15 minutes

Click to edit Master title style Sonochemical Surface Modification in Water Optimization of Probe to Sample Distance Effect of Probe to Sample Distance on Weight Loss for Isola 370HR 20 kHz, 4.8 Wcm -2, DI Water, 40 ºC

Click to edit Master title style Sonochemical Surface Modification of ABS Modified process As received After Sonication at 40 kHz

Click to edit Master title style Sonochemical Surface Modification of Electronic Materials Conclusions Significant sonochemical surface modification can be achieved on a variety of materials used in electronic manufacture using water as the liquid medium The project has identified a number of factors influencing sonochemical surface modification –Frequency –Ultrasonic intensity –Probe to sample spacing –Liquid temperature –Added surfactant etc The project produced a technology platform from which potential commercial applications are emerging

Click to edit Master title style HIGH EFFICIENCY PRINTED CIRCUIT BOARD PROCESSES HEPROC Effect of Ultrasound on Permanganate Etch in Desmear Process Nine Month Feasibility Project Funded by the Technology Strategy Board (TSB)

Click to edit Master title style Desmear Process ProcessMake - upTemp. (ºC)Time M-Treat AQ (Solvent Swell) 20% v/v M-Treat K 22 g/l NaOH 601 min 24 sec Rinse2 min M-Permanganate P0, 33, 65 g/l M-permanganate P 0 or 32 g/l NaOH 5,25,40,60,852 min 48 sec Rinse3 X 1 min Neutralizer3% (v/v) H 2 SO 4 3% (v/v) 37% H 2 O 2 Ambient48 sec Rinse2 min DI Rinse1 min Permanganate – with/without ultrasound (vigorous stirring) Ultrasound – 20 kHz ultrasonic probe, Power 50 W, Probe to sample distance 5 mm

Click to edit Master title style Isola 370HR Laminate Effect of Ultrasound on PCB Desmear Isola 370HR Laminate Baseline Baseline value obtained using - 65g/l KMnO4, 32g/l 85 ºC Ultrasound always gives higher weight loss Half strength permanganate at 60 ºC gives weight loss equivalent to baseline

Click to edit Master title style SEMs of Through Holes Solvent – Yes K 2 MnO 4 – 65 g/l, NaOH – 32 g/l, Temperature – 60 ºC Solvent – Yes K 2 MnO 4 – 65 g/l, NaOH – 32 g/l, Temperature – 60 ºC Silent Ultrasound Solvent – Yes K 2 MnO 4 – 33 g/l, NaOH – 32 g/l, Temperature – 60 ºC Solvent – Yes K 2 MnO 4 – 33 g/l, NaOH – 32 g/l, Temperature – 60 ºC Silent Ultrasound

Click to edit Master title style Effect of Ultrasound on Permanganate Etch in Desmear Process Solder Float Assessment Experimental Runs Isola 370 HR 4-Layer MLB Hole size – 0.9 mm Diameter Solder Float – 1 X 260 ºC, 10 seconds Run NoUltrasound Permanganate ICD rate (%) Temp.Conc.NaOH ºCg/l Standard Kelan Desmear No Yes Yes

Click to edit Master title style Effect of Ultrasound on Permanganate Etch in Desmear Process Conclusions Initial weight loss studies indicated that the application of ultrasound to the permanganate part of the PCB desmear process produced higher weight loss and would enable lower temperature and lower permanganate concentrations to be used. SEM examination of through holes confirmed these findings Applying ultrasound to the permanganate in a semi- production mode produced defect free PCBs at lower temperatures and lower permanganate concentrations

Click to edit Master title style SUSONENCE Three year multi-partner project Aims to produce industrial scale ultrasonic equipment for sustainable surface modification Target sectors - metal finishing and printed circuit board Objectives Reduced use of toxic/ hazardous chemicals Waste minimisation/ diversion from landfill Reduced energy consumption Reduced water consumption

Click to edit Master title style The system is designed to be very flexible in its operation. Applications pre-treatment Etching Post treatment Rinsing The ultrasound tank is connected to a heater chiller which controls the temperature between 0 and 80ºC. Other tanks have a built in heater. An extraction system has been implemented.

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