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Single wafer box for wafer quarters
Toni Pasanen' Aalto University, Department of Electronics and Nanoengineering
Single wafer boxes are a handy way to pack wafers securely e.g. during shipping or to store valuable samples firmly and securely. However, commecial products (e.g., here or here) are designed only for full wafers, and sometimes there is a need to store smaller samples, e.g. wafer quarters. Since the commercial products have a support for samples only at the edges, wafer quarters lie on the bottom at the center and can almost freely move in the box, which causes sample scratching.
In this project, a customisable single wafer box was designed for four wafer quarters. The box is significantly cheeper than the commercial ones and has sample supports also in the center, ensuring horizontal position of the samples. Furthermore, the box has separator walls for samples, which prevents the quarters from sliding on top of each other preventing sample scratching. The size of the box can easily be tuned for various wafer sizes by changing only one parameter in the scad code. The samples can be easily removed with tweezers due to a gap in the outer support. See presentation slides below for more information.
This project was performed as a final project of the L3999 course Fall 2017.
The wafer box, the lid and the spider spring are printed separately. Separate scad and stl files for all parts can be found at the NIH Printing repository. The wafer size supported by the box can be easily changed by a single parameter in the beginning of the scad code, which adjust all the other dimensions accordingly. Alternatively, the code offers the possibility to easily tune all dimensions by dedicated variables. These include wall and bottom thicknesses, tolerance for sample size, height of the box, edges and sample separators, and the tweezer gap dimensions. By default, the box is suitable for four 100 mm diameter wafer quarters, but the sample separators can be modified to support e.g. wafer halves or smaller samples. The bottom of the box has a groove matching with the edge, which enables stacking several boxes firmly. If the box or edge height is changed, the groove is adjusted accordingly by the code. Additionally, the box has a locking mechanism, which ensures that the lid stays firmly at its place. A separate spider spring prevents the samples from moving in vertical direction. If higher print speed or larger layer height is used in printing, the tolerance of the groove may need to be increased.
Detailed information with illustrative figures is presented here.
Bill of Materials
- Wafer box bottom
- Wafer box lid
- Spider spring
$0.78 (bottom) $0.50 (lid) $0.025 (spider spring)
Price of a commercial equivalent is $22.18, i.e., the cost savings with the 3D printed version with additional features is $20.88 per pc. The price of the used printer (LulzBot TAZ 6) is saved after 120 printed boxes.
1) Download the scad and stl files from the NIH repository. By default, the box is suitable for four 100 mm diameter wafer quarters. If this size is preferred, move directly to step 3.
2) Set the wafer diameter and corresponding tolerance in mm in the scad code by using the first two variables (named 'd_wafer' and 'toler_d'). All the other diameters can be changed by the corresponding variables explained in the comments. Make sure that the six first variables highlighted in the 'lid part' code match with the values set in the 'bottom part' code. Change also the spider spring dimensions accordingly. After all changes, export stl codes for the slicer.
3) Print the bottom and lid parts and the spider spring separately or in one run. Printing of a single piece took approximately 1.5 hours using a print speed of 50 mm/s and a layer height of 0.38 mm with PolyLite PLA and LulzBot TAZ 6 printer. Several bottom parts can be printed per one lid if the boxes are stacked.