Often the existing standard cover glass of CCD / CMOS image sensors cause disturbing reflections or interferences. This can be avoided by removing the cover glass.
The removal of the cover glass also offers interesting opportunities as a first step to improving a sensor, so that relatively inexpensive types can also be used for high-end applications. Examples are the attachment of customized filters, or the UV coating of the sensor surface.
Within the last few years Eureca has developed several procedures for removing glass covers from CCD/CMOS image sensors. Therefore, we can provide a suitable procedure for many sensor types. The different procedures have different failure rates of damaged sensors, which are however, in the best cases, only in the region of a few percent.
The development of suitable methods for the cover glass removal from image sensors was also part of a research program at Eureca, which was supported by the Central Innovation Program of the Mittelstand (ZIM).
We use both sensors from our own product range, as well as sensors that are provided by the customer. Before processing the latter these sensors first undergo an extensive quality control to detect e.g. possible changes in the manufacturing procedure. Only when, after a successful testing, it is sure that the sensor can be processed with a good chance of success and we have the approval of the customer, will the sensor be processed further.
After the removal of the glass cover, the sensors are inspected optically for possible damage and cleaned, if necessary. An additional electrooptical test with the recording of test images is possible, as long as we have a suitable camera board available. With sensors, which we process in higher volumes, this test is always made.
Then new (e.g. anti-reflective) glass covers or filters can be placed on the sensors in addition to a coating already described above. For applications where the sensors or cameras are used in a cooled application this can be done under an argon atmosphere to prevent condensation of trapped moisture.
As protection during the shipment to the customer a special adhesive foil is used,which has to be removed before the use of the sensor.
Many years of experience and a high volume of sales have shown that sensors without glass covers provide the same life time as the original types. Without glass covers the sensors are however mechanically very sensitive and have to be protected against humidity and dust.
So far the following types have been handled with success:
You can find closer information, including statistical data of the sensor contamination after the processing, in our PDF document Glass cover removal from image sensors.
After the glass cover removal the sensor can be processed further. Examples for possible improvements are: