Solder Paste in a Bilayer Hole Solder blob in a model cylinder

Solder Paste in a Bilayer Hole

This evolver code calculates the shape of a solder droplet in a hole etched through a two-layer polymer coating. The idea is that the hole is completely filled with solder paste of a known solder volume fraction, and then reflowed to consolidate the solder.

Before you ask, yes, the solution to the problem without gravity is well-known, it is a spherical cap. But with gravity it deviates somewhat from this solution, and the precise extent of deviation can be important for some applications.

Running this file is a breeze. Just set your parameters, hit the "submit" button, save the generated file as yourname.fe, and then in the same directory, type

evolver yourname
and at the next prompt, type
and it will do all of the iteration, mesh refinement, etc. for you automatically. If at the end the scale is very small, so that it just does one iteration per cycle, then you may use
to give the system a "push" and move toward equilibrium.

The beauty of Evolver codes is that actual application is limited only by the user's imagination. We therefore encourage the user to use this code in whatever way it is helpful. The original driving force for writing this particular evolver solution was the issue of self-allignment of flip chip assemblies with underfill/solder bumps applied at the wafer level. Another code written for the underfill project can be found here.

This code was written by Adam C. Powell, IV while employed at the Materials Science and Engineering Laboratory at the National Institute of Standards, with partial support from the Advanced Techology Program.

Share and enjoy!

Hole radius (mm):
First layer thickness (mm):
Second layer thickness (mm):
Contact angle in the first layer (degrees):
Contact angle in the first layer (degrees):
Solder fraction in paste:
Solder-air surface tension (kg/s^2):
Density (kg/mm^3):