To microelectronic engineers, BCB stands for benzocyclobutene, a polymeric material that combines bonding capability with appropriate electronic properties for chip manufacturing. Yet the reason that this base material - more accurately known as biscyclo[4.2.0]octa-1,3,5-triene or 1,2-dihydrobenzocyclobutene - is useful is because of its unusual polymerisation chemistry that rapidly forms other, more complex cyclic organic structures.
BCB was developed in the 1980s and has been a commercial technology since the 1990s, initially in the fabrication of radio-frequency integrated circuits and flat-panel displays. Since then its application across electronics has broadened, and one element in that success has been its precisely controllable and readily-monitored thermal curing process.
The polymerization process can be stopped before all monomer is consumed, to be finished at a later date, and this is how most BCB adhesive is supplied. The Diels-Alder reaction dominates in the second curing step