Abstract
Metalized micron scale polymer particles have been utilised in anisotropically conductive adhesives for a number of years and more recent work has investigated their selective deposition to provide interconnects. In this work such particles have successfully been deposited onto substrates that included both unpatterned Cr/Au coated chips and test chips with “daisy-chain” interconnected bond pads, using an electrophoretic deposition technique. These were then bonded to matching substrates using a flip-chip thermocompression bonder. The interconnections formed using this method were then characterised in terms of their mechanical and electrical properties. Silicon wafers coated with gold were used as substrates for shear strength studies, which showed that the failure point of the bond produced was at the polymer-metal interface, suggesting that strong bonds had been formed between the particle surface metal layer and the substrate. The effect of the duration of the bonding process has been investigated via shear strength measurement. The particles were also deposited onto the bondpads of a daisy chain structure to allow the electrical properties of the bonds to be studied. This investigation showed that, for the same range of bonding conditions, the electrical resistance of the interconnection decreases as the mechanical shear strength increases. This occurs due to an increase in the bonded interfacial region between the particle and the substrate.