Case 17: Tilt Planets
Tilt planets can bring significant benefits. In this example we examine a planetary-rotation coater in which the rotation axes of the planets are tilt from the orbiting axis of the tooling.
For ease of comparison we model the same planet fixtures as in the conventional planetary coater case: they are flat and 25 cm in radius. Now we tilt the planet axis by -43 degrees, as shown in the chamber view below. Four such planets can now be accommodated in the 31-cm-radius orbit.
We compute for 36 points that cover a radius of the fixture. After optimizing the source location, the thickness nonuniformity is found to be 1.5% in the absence of masks, the associated material collection is 45.8%, as shown in the result panel below.
Next, we introduce a pair of uncoupled masks into the camber. They are positioned in a plane 20 cm above the source and are separated in azimuth angle by 120 degrees. We use the usual mask-fitting process: manually shaping the anchor points first followed by the automated optimization via the V-Grade 5 program. The resultant masks are shown in the mask panel below.
We re-calculate in the presence of the two masks.The result is shown in the result panel below. The thickness uniformity is improved with a nonuniformity of 0.10%; the material collection is 42.3%.
In both cases, with and without masks, the material-collection efficiency is substantially higher than the conventional planetary coater for similar thickness uniformity. Another benefit of this tooling is that the chamber size can be smaller than the more conventional type.
There is no magic about the 43-degree tilt angle for the planets, good coating results can be had at different tilt angles.
