Researchers in the UK have developed a conductive adhesive that can be easily removed for recycling, writes Nick Flaherty.

The team at the University of Newcastle has already demonstrated reversible adhesive technology, but the new glue is electrically conductive. This means that it can join electronic components in the same way as solder. Unlike solder, however, a simple wash with a green solvent like acetone, or using an alkaline solution, allows the components to be separated for reuse or recycling.

This is a ‘one-pot’ adhesive and is water-based, so it does not emit organic solvent vapours and does not require a hardener. It is also as strong as other water-based glues. The glue is made in the same way as a paint, but silver particles are added rather than pigments, and this gives the formulation its electrical properties. Other conducting glues exist, and many of these also include silver for optimal conductivity, but none can easily be debonded.

The electrically conducting reversible adhesive has a conductivity up to 2.9 x 10 S/m and a lap shear strength of up to 1.5 MPa.

Adhesion is reversed by immersing the bonded joints at pH 14. By heating to 85 C and stirring the solution (500 rpm), the debonding time can be reduced to 30 minutes or less. Separation can also be achieved at 85 C at pH 7. Short debonding times can also be achieved at room temperature using acetone, a recognised green solvent.