Tombstone Example tomb-G for the Surface Evolver

[Click for the tomb-G.fe datafile in a second window.]

This model does an upright chip, in the tombstone position. It includes solder contact on the "top" of the chip (z+ face). The initial geometry still has the chip in a horizontal position, so the initial solder surface looks weird, but things straighten out when the chip is raised up and evolved.

Starting position.	Starting solder surface.
Chip raised up.	Solder when chip raised.
Solder after one iteration.	Evolved surface.

Notable features:

• Since the chip is to be in the tombstone position, solder will be making contact with the z+ face of the chip. Previous datafiles have made no provision for this. The main change is to extend the contact facets to the z+ face. Feeling too lazy to change all the vertex coordinates, I have left the chip in the horizontal position while adding the topologically correct faces. Hence the inside surface of the solder pokes out, as seen in the top right image. In the top left image, the coincidence of solder facets and chip facets gives problems to the graphics, so the white and red both show.
• The chip is moved into its upright position by the upright command, which rotates the chip 90 degrees, shifts it over the pad in the x direction, and lowers the chip to rest on the pad, as shown in the left middle image. The solder surface (middle right image) looks bad, but one iteration serves to pop it out into a good position (left bottom). The user has to invoke upraise before evolution.
• Note there are small cusps in the solder contact line along the chip corners.