Method for checking and producing a composite of a substrate stack, and hermetically sealed enclosure produced according to said method

A process for producing a hermetically sealed enclosure, the process comprising:

• planarly arranging at least one first substrate against a second substrate to form a substrate stack, the at least one first substrate and the second substrate being arranged directly against one another or on one another, so that at least one contact area is formed between the at least one first substrate and the second substrate at which the at least one first substrate is in direct planar contact with the second substrate, and the at least one first substrate comprising a transparent material;
• detecting a radiative reflection which comes about through irradiation of the substrate stack with a radiative input on the at least one contact area;
• ascertaining a first bond quality index Q1 of the at least one contact area from the radiative reflection;
• hermetically connecting the at least one first substrate and the second substrate to one another by direct joining of the at least one first substrate and the second substrate with one another in a region of the at least one contact area, so that a joining zone is formed which reaches into the at least one first substrate and into the second substrate and which directly meltingly joins the at least one first substrate and the second substrate to one another;
• detecting a further radiative reflection, which comes about through further irradiation of the substrate stack with the radiative input on the at least one contact area;
• and
• quantitatively ascertaining a second bond quality index Q2 of the at least one contact area from the further radiative reflection using the formula Q2=1−(A−G)/A or Q2=1−(N−G)/N, wherein A is an area of the at least one contact area, G is an acceptance area, and Nis an area of a useful region.