C-Cage jig and cage preparation procedure

Equipment Needed

  1. If not already done, remove C-cage jig end plate from rest of jig

  2. Using ethanol and kimwipes, clean the jig. The parts which should be cleaned include:

  3. Remove a C-cage from the environmental chamber. Remember to be careful with the Rohacell cages since they are very fragile. Determine the top of the cage.

  4. Verify that the dimensions of the cage meet specs. The dimensions are summarized here. If any of the width measurements are outside of the range between -2 mils and +4 mils from the spec width (2.094"), make a note and choose another cage.

  5. Determine the correct orientation of the C-cage with respect to the gluing fixture. The handwritten ID number for the cage should be on the top end of the cage. To verify this is truly the top, look at the raised areas on each of the six faces where the silicon will be glued. Each of these should have notches in two corners (these provide a relief for the gluing of the bias tabs to the silicon). These notches are on the "bottom" end of the face, i.e. on the end toward the MCM plenum. Hold the cage such that the bottom points toward the plenum support arm of the jig.

  6. Now, gently slide the C-cage onto the gluing fixture. Take care to push only on the thick cross-ribs of the cage, and not on the thin parts where the silicon will be glued. The spaces between the inner and outer barrels on each of the three faces should just slide over the spacer blocks. Slide the C-cage onto the blocks until it is approximately centered on the blocks.

  7. Attach the outer jig end plate, sliding it onto the locating pins on the top and bottom spacer blocks. It is possible to have locating pins in two spots on each of the top, bottom and center spacer blocks, but we are just using the outermost 2 pins (i.e. upper hole on the top block and lower hole on the bottom block). Due to the tight tolerances, it may require some jiggling to get the end plate fully onto the pins. Take care not to use too much force; remember there is a very fragile C-cage on the jig, and that we eventually will need to remove this plate without damaging the cage. Insert and tighten securely the 8-32 screws into each of the three spacer blocks.

  8. Verify that the end plates are in the correct position by sliding the vacuum pickup fixture onto its locating pins on each of the 6 faces. If there is a problem, most likely it is due to the plates not being tightly connected to the spacer blocks, since all jigs have been adjusted with shims. If tightening doesn't solve the problem, shimming may be necessary.

  9. Now we will center the C-cage on the jig, using two depth gauges. Adjacent to each of the four ribs of the C-cage, there are two holes (one on the inner face side, and one on the outer face side) drilled in each of the end plates of the gluing jig. These holes will allow the insertion of a rod from a depth gauge. Set the two depth gauges to the same depth and press them tightly against the end plates to center the cages (be careful not to damage the cage). The depth the gauges should nominally be can be determined from the width measurements: the outer edges of the end plates are nominally 3.260" apart,and the spec width of the cages is 2.094", so that the depth gauge for a spec cage should be (3.260-2.094)/2 = 0.0583" This number should be adjusted for the actual cage width, and, since the jigs aren't perfect, adjustment will be needed to get the ideal centering. The aim here is to center to within +/- 1 mil.

  10. Remove two Rohacell central plenum middle spacer blocks from the environmental chamber (In the container marked Part C). These have been pre-measured and separated into bags of equal width. Choose two from the same bag with a width comparable to the C-cage being used.

  11. Attach the plenum middle spacer blocks to the plenum support fixture on the C-cage gluing fixture. The thickest side of the spacer blocks should be away from the support fixture (i.e. the relief grooves should be on the inside of the plenum). Each of the plenum middle spacer blocks have a thin groove cut into each side; on the side of the plenum support fixture away from the arm, attach the metal C-spring onto the end of the plenum support fixture such that the tabs on the ends of the C-spring are in the grooves of the plenum middle spacer blocks. On the side of the plenum support fixture nearest the arm, the groove in the spacer block should line up with a groove on the plenum support fixture--insert a small piece of poster board to join the middle spacer block to the plenum support fixture.

  12. Using a scalpel, cut 4 pieces of nylon 4-40 threaded rod to a length of roughly 4.5". Using a scalpel should avoid any burrs on the ends of the rod and on the ends of the thread, but if necessary, deburr with sandpaper. Put the threaded rod through the holes in the corners of the plenum middle spacer blocks.

  13. Remove the remainder of the plenum pieces from the environmental chamber (4 top spacer blocks, 4 bottom spacer blocks and two end blocks). Choose them so the sizes are as close to uniform as possible over the plenum. Construct the plenum using the threaded rod. Make sure the top and bottom spacer blocks are oriented correctly (i.e. with the slot to hold the MCM facing away from the plenum support fixture). The bottom and top blocks can be distinguished by the size of the wirebond relief slot (on the face opposite the MCM holding slot)--the bottom block has a shorter wirebond relief slot. When the plenum is completed, attach nylon washers and nuts to the threaded rod.