Ultrasonically enabled low temperature electroless plating for advanced electronic manufacture

Electroless plating is an important process for the metallization of non-conductive substrates and is therefore widely utilized throughout the electronics and packaging industry. Electronic manufacture now requires processes and materials that can meet the demands for miniaturization and reliability since holes and via diameters in both printed circuit boards (PCBs) and microelectronics are being reduced whilst aspect ratios are getting higher. It is critical for the future development of electronics that manufacturing processes become adapted to meet these requirements. In terms of electroless plating, miniaturization means that ensuring full coverage in vias and holes is extremely challenging whilst the electroless deposit structure is important to ensure high reliability, high conductivity etc. In addition the plating process must be able to meet the need for high production volumes (i.e. high deposition rates) whilst enabling more sustainable, low energy manufacturing. Performing electroless plating in an ultrasonic field has great potential to enhance the deposit properties and meet these advanced manufacturing requirements. This paper will discuss the results from the IeMRC funded ULTIEMet (Ultrasonically enabled Low Temperature Immersion and Electroless Metallization) research project which has utilized a methodology incorporating a mixture of electrochemical and laboratory plating tests. It has been found that by optimizing how ultrasound is introduced to the electroless process benefits such as reduced temperature plating, enhanced coverage and a finer grain structure deposit can be realized.