Our windows require optical coatings on both sides.....do they go on before or after your metals?
We can do it either way, however it is more common for the metal solderband coatings to be applied
after the optical coatings, mainly to ensure that the metals remain pristine.
you apply the metals directly over the optical coatings?
They can be, depending on the
composition of the optical films, but a much more reliable hermetic seal will be made if the metals are deposited directly
onto the substrate material. The optical coating process normally requires a "tooling land area" around the
perimeter of the window which will be free of the coatings, so this is rarely a problem. If the top layer of the optical stack
is MgF2, SiO, or SiO2, then we can bond to these materials as well as we bond to the substrate material, however, if the top
layer of the stack is one of the Zinc compounds, then we do not recommend applying metals over this material. One way
or another, we always do a test run, to be certain.
We need the
edges of our windows metalized, as well as the top surface perimeter......is this a problem?
at all, but you need to make us aware that this area is critical to your sealing process, as we need to take some special
measures to make sure that you get good coating quality on the vertical edges of your windows.
we have our windows coated on three sides, top, bottom, and edge?
Yes, but this option
should be considered carefully as it adds significantly to the cost of the metalizing process, as well as adding a LOT of
extra handling.........more handling always means potential cosmetic damage to the optical coatings.
Will the thickness of the metal on the edges be the same as the top surface metals?
they will be thinner by as much as 50%, yet still adequately thick for excellent soldering characteristics.
We will do a solder pot dip test as part of the final inspection whenever possible
What if we don't want any metals on the vertical edge....topside only.....can you accommodate this?
Yes, but it will require special fixturing to protect the edge. For example, we can machine an aluminum carrier
plate(s) with a recess for each window, such that the windows are sunken into the carrier. Still, considering the machining
tolerances of both the windows and the fixture, there will likely be enough of a gap around the windows to allow some of the
metals to "blow by" and accumulate on the vertical edge of the window.
hot will our windows get during the metalizing process?
Not to exceed 75° C
What is the maximum temperature that these films will survive?
450-500°C, but we have a recent report from a customer who has taken them to brazing temperatures (800C+) without
failure.......yes, that surprised us too!