Development of a Oxygen Sensor for Marine ... - DTU Nanotech

6.3. THE ’O’-RING 55
Figure 6.8: The ’O’-ring is being squeezed out of where it is supposed to be.
The picture to the left shows it sticking out of the hole, while the
picture to the right shows it being squeezed over the chip.
6.3.1 Changing the resting area
Now the original design for the packaging had the ’O’-ring resting on a flat
area as show on picture 6.9. Also while the ’O’- was supposed to be squeezed
together it was only supposed to contract about 20 % percent, in order to
have a tight fit. So how was this solved? First off the resting area for the
’O’-ring was changed, so that it became a grove instead of a flat, as show on
picture 6.9.
Figure 6.9: The sketch to the left shows the original flat area, which the ’O’ring
rested upon, while the sketch to the right shows the changed
design, where a grove is added for the ’O’-ring.
This, along with a optimization of the process where the laser cuts the
grove, ensured that the the ’O’-ring no longer did this in most cases. Also it
was better to have the screw clamp give a smaller amount of pressure, and
then have the packing inside the oven a little longer if the PMMA layers
hadn’t bonded properly, rather than applying much pressure and cause the
’O’-ring to slip out. Since everything in the design should be able to survive
the extended duration inside the oven.