CAMBRIDGE, UK – The high-temperature and time-consuming reflow process leaves space for electrically conductive adhesives, according to a new IDTechEx report. ECAs comprise a metal powder embedded within a polymer resin and are well suited to applications that require electronic components to be mounted on anything other than a conventional FR4 substrate, especially when the substrate material is thermally fragile.

Although more expensive and without the benefit of self-alignment, ECAs enable components to be immediately attached to the substrate and don't require either high reflow temperatures or lengthy thermal ramps, the firm says. They are thus highly unlikely to replace solder for conventional PCBs, but are predicted to increase their market share with the transition toward integrated and flexible electronics.

Furthermore, anisotropic conductive adhesives ACAs enable a lower pitch capacity than the more common isotropic conductive adhesives. At present, ACAs, which are supplied as either films or pastes, require high temperature and pressure to be applied during component placement, increasing both manufacturing costs and the risk of component damage. However, the emerging technology of field-aligned conductive adhesives removes this constraint since anisotropic conductivity is induced prior to attachment.

A promising emerging application for ECAs is in-mold electronics, used to make decorative surfaces with integrated capacitive touch sensing and lighting. Automotive interiors are the major use case, with the total IME market forecast to reach around $1.5 billion by 2032, according to IDTechEx. IME components are manufactured by screen printing conductive ink onto a flat (usually polycarbonate) substrate, after which electronic components are mounted.

Another promising ECA application is flexible hybrid electronics, a developing approach that can be regarded as taking the best of both from conventional and printed electronics. This requires components to be mounted onto flexible substrates with printed conductive traces, with ECAs (or alternatively ultra-low temperature solder) required so as not to damage low-cost PET substrates.

A specific use case for ECAs is stretchable electronics, required for e-textiles and some electronic skin patches. This will require slightly stretchable component attachment solutions. Since the mechanical properties of ECAs are largely dependent on the properties of the polymer resin, slight stretchability can be introduced by using an elastomeric material.