Several industrial facilities produce electroless copper for use in printed circuit boards. One major class is the high- strength copper, so called because of its extremely high strength. During the deposition process, hydrogen is commonly incorporated into the film and it is thought to be the cause of poor ductility.
In this work, the hydrogen content was measured by the fusion technique in three sets of high strength electroless copper specimens, respectively annealed at 423, 520 and 573 K. The hydrogen content decreased very rapidly at the two higher temperatures, and tended to a saturation value of approximately 20 ppm by weight with increasing annealing time. The cavity evolution with annealing time at 520 and 573 K was studied by transmission electron microscopy (TEM). It was found that the number of cavities increased with annealing time and with increasing temperature.
The data indicate that hydrogen degassing is not controlled by bulk diffusion and, hence, that hydrogen must be trapped. A comparison with recrystallization results demonstrates that more than half of the hydrogen retained in the electroless copper is in saturable traps. The TEM observations indicate that cavity coarsening takes place during annealing at 520 and 573 K.