NOVELTY - The process comprises preparing a perforated anode and a perforated cathode on each side of the electrolyte so as to leave the first surface zone of both sides of the electrolyte not covered by the anode or cathode, depositing a solder joint composition layer on the surfaces of the anode and the cathode corresponding to the second zones, vertically stacking a plate and a cell interconnection, heating the stack of cells and interconnection plates at a temperature sufficient to melt the solder composition, and cooling the stack at room temperature.    USE - The process is useful for fabricating of a high temperature electrolyzer or high temperature fuel cell.    ADVANTAGE - The process is capable of simply, reliably and economically fabricating a robust high temperature electrolyzer or high temperature fuel cell with improved performance, life time and other characteristics, avoids contact of too high pressures and inhomogeneous distribution of stresses thus avoiding the cracking of the cells, and prevents the leakage of hydrogen from the cathode to the anode, oxygen from the anode to the adjacent cathodes and water vapor into the cathodes and anodes.    DETAILED DESCRIPTION - The process comprises preparing a perforated anode and a perforated cathode on each side of the electrolyte so as to leave the first surface zone of both sides of the electrolyte not covered by the anode or cathode, depositing a solder joint composition layer on the surfaces of the anode and the cathode corresponding to the second zones, vertically stacking a plate and a cell interconnection, heating the stack of cells and interconnection plates at a temperature sufficient to melt the solder composition, and cooling the stack at room temperature using electrolytes to form electrolytes and interconnectors. Each of the elementary cells includes a planar porous anode and cathode having cut-outs and is respectively arranged on each of the surfaces of a dense planar electrolyte, and brazed joints made by the infiltration of a predetermined amount of brazing material into the electrodes at contact points between the elementary cells and the interconnection plates. The first non-covered zone defines a second zone of the electrolyte face according to a location of solder joint to obtain a unit cell comprising the perforated anode and cathodes. The quantity of the composition is present in such a manner that its molten state the composition fills all the porosity in the thickness of the anode or cathode to the surface of the electrolyte, and exceeds beyond the surface of the anode or the cathode with a thickness of more than 20% of the thickness of the anode or cathode. The amount of brazing composition is such that in the molten state it does not exceed beyond the surface of the anode or cathode. A lower terminal plate of the stacking is placed on a support before heating, and an upper terminal plate of the stacking is placed on a support after cooling. The perforated anode and cathode are prepared by selective deposition of a suspension of respective anode and cathode materials by screen printing using a mask, and the respective layers are sintered and then removed by laser ablation or machining. The electrolyte is a dense material having porosity of less than 10 vol.% and a thickness of 90 mu m. The composition is deposited on second zones by screen printing using the mask or a manually with a robot and a syringe and a pneumatic dispenser. The anode and cathode are porous material having a porosity of 30-50 vol.% and a thickness of 40 mu m. The soldering step is performed under air. The anode, the cathode and the electrolyte have identical flat surfaces that coincide with each other.    DESCRIPTION OF DRAWING(S) - The figure shows a schematic cross-sectional view of a stack of high temperature electrolyzer or fuel cell.    Cell (91)    Lower interconnectors (95)    Upper interconnectors (96)    Sealed solder (97)    Upper plate. (98)