Hermetic weld for a thin film electrochemical cell activated with a solid electrolyte and housed in a ceramic casing

xyzA miniature electrochemical cell having a total volume that is less than 0.5 cc is described. The cell casing is formed by joining two ceramic casing halves together. One or both casing halves are machined from ceramic to provide a recess that is sized and shaped to contain the electrode assembly. The opposite polarity terminals are metal feedthroughs, such as of gold, and are formed by brazing gold into openings machined into one or both of ceramic casing halves. A thin film metallization, such as of titanium, contacts an edge periphery of each ceramic casing half. The first ceramic casing half is moved into registry with the second ceramic casing half so that the first and second ring-shaped metallizations contact each other. Then, a laser welds through one of the casing halves being a substantially transparent ceramic, for example sapphire, to braze the first and second ring-shaped metallizations to each other to thereby join the first and second casing halves together to form a casing housing the electrode assembly. A solid electrolyte (LiPON) activates the electrode assembly.