Effect of process parameters on residual gas in metal package

Abstract

The effect of process parameters on the residual gases, H2O, O2, CO2 and H2 in the metal package were investigated in this study. It was found that the H2O mainly came from the surface adsorption of raw materials and the H2 was from the electroplated Ni/Au layers of Kovar alloy. The O2 primarily came from the water vapor and the environment, while the CO2 in the cavity was mainly generated by the reaction between the O2 and residual carbon. The temperature and holding time of the baking, parallel seam welding and screening aging process could effectively affect the content of H2O, O2, H2 and CO2 in the cavity. Prior to sealing, increasing the temperature of baking and parallel seam welding could reduce the contents of H2O, O2 and H2. However, after sealing, the H2O and H2 absorbed on the material surfaces continued to desorb into the sealed cavity during the screening aging process, leading to the increase of the H2O and H2 content. It was also found that the gas leakage has an important effect on the residual gas inside the cavity. In the long-term screening aging process, the O2 could leak into the cavity from the air because of the concentration gradient. In the meantime, the O2 reacted with the residual carbon to generate CO2, causing an increase in the CO2 content. As the CO2 concentration in the cavity was higher than that in the air, it would leak into the air until equilibrium was reached.