The present invention generally relates to a plate sintering method to be used in a sintering process and so on of a screen-printing and sintering type solar cell plate.
A manufacturing process of a screen-printing and sintering type solar cell will be described as a representative example. FIG. 3(a) shows a screen printing step of extending the paste 1 of a film component of a solar cell through a screen 2 so as to make a printing film 4 on a plate 3 using a screen printing machine. FIG. 3(b) shows a drying step of effecting a low temperature drying operation, by a heater 6, of above described plate on a conveyer belt. FIG. 3(c) shows a sintering process of sintering the printing film 4 with a belt type electric furnace 7. A CdS film, a CdTe film, a C film, and an Ag+In film are sequentially combined by the repetition of the respective printing, drying, and sintering operations. A general belt type electric furnace used in the sintering step is shown in FIG. 4.
A heat treatment container with a plate 10 being accommodated in it is heated, on a conveyor belt 8 moving at a constant velocity v, within an inert gas atmosphere 12 by a muffler 11 having a heat source for continuously causing a given heat gain amount quantity of heat. The heat treatment container 9 is moved into the electric furnace. It is normally heated gradually to approximately 700.degree. C. and is retained within the muffler 11 for approximately one hour. Thereafter, it is gradually cooled near the exit to a normal temperature and is then taken out. The construction of the heat treatment container 9 is shown in FIG. 5. A plate 15, and an intermediate plate 14 for preventing the thermal deformation of the plate 15 are accommodated in a boat 13 made chiefly of a heat-proof ceramic. A cover 16 is provided with aperture portions for controlling the heat radiation coming from the heater of the electric furnace and the evaporation of the film components.
A sintering method of using such a heat treatment container as in FIGS. 3(a)-3(c) that is the conventional solar cell sintering method is not necessarily good in terms of the thermal efficiency of the plate, especially in a large area plate of approximately 1200 cm.sup.2. Large temperature differences are caused forward and rearward in the advancing direction of the heat treatment container and the plate, and the fusing reaction of the CdS film and the CdTe film become unequal, thus causing dispersion in the light/voltage conversion efficiency and so on of the solar cells.
Masking to realize a heat equalization with an object of controlling the heat radiation on the plate with respect to the above described basic problem has already been proposed is Japanese Laid-Open Patent Publication No. 1-105777). Such masking is considered to be applicable to the cover of the heat treatment container 9.
When the cover of the heat treatment container 9 has been designed using of the aforementioned masking method, drilling and so on have to be frequently changed in accordance with the hole diameter or the area aperture portions in the processing. When the productivity is considered, the efficiency is inferior.