Leveling the gap-pad material.

Also see ROC holddown buttons.

The gap-pad material that transfers the heat from the ROC to the cooling plate is a clay-like substance that comes in 1/8" thick sheets. On the back of the ROC are many small components, similar to these ones on the back of a FEM board. You can press the material over these components, but then the surface that faces the cooling plate is no longer flat.

Shown here is a piece that has been pressed over the components and taken off again and flipped over. You can see the indentations.

The jig shown here allows you to level the gap-pad surface after it has been pressed over the backside components.

It is a flat surface, with 3 sides of 1x0.5" Aluminum U-channel.

The ROC board (or in this case a FEM board) is mounted on 6/32 threaded rods with a spring and a wingnut, such that the height can be changed.
Adjust the height all around such that a long file, laying on the edges of the jig, just touches the bumps in the gap-pad material.

A few short strokes, applying no pressure other than the weight of the file, will take off the high points of the gap-pad material. Carefully raise the board and file until all the bumps are leveled.

The material will clog the file quickly, so after every few strokes, clean the file with a brass brush.

The procedure for dealing with the gap-pad material and the ROC is thus as follows:
  1. On a 1:1 printout of the ROC, lay out the two pieces of gap-pad material. Use one of the already-made cardboard ROCs for this.
  2. If any sticks out beyond the ROC perimeter, trim it off with a sharp blade.
  3. Remove the protective foil from the exposed side.
  4. Position the ROC on top, and gently press it into place.
  5. Turn this sandwich over, onto something soft like foam or bubble wrap.
  6. Remove the paper ROC, and peel off the other protective foil.
  7. Gently press the stuff onto the ROC board, pressing it around the backside components.
  8. Mount the ROC on the jig described above, and level the bumps.
  9. If the ROC is not ready to be mounted, put the protective foil back to keep the stuff clean.
  10. Store the boards in this position, to prevent the gap-pad material from falling off.
Hubert Van Hecke
Last modified: Mon Sep 12 17:32:55 MDT 2011