Subplate Gluing

George Stephans Last Updated 5/7/2000

This document describes the steps involved in gluing the subplates onto the SMD assemblies. This is the first step in hybrid assembly that is performed outside the Electronics Facility (EF).

  1. Preparation
  1. SMD assemblies returned from assembler and tested by EF
  2. Hybrid entered in database and tracking sheet prepared
  3. EF records DC offset of temperature sensor
  4. EF records the capacitance value (around 2.14 pf) for the batch of calibration capacitors used on the SMD assembly
  5. EF selects subplate, checks the dimensions, and measures its thickness in 3-4 places
  6. EF delivers subplate, SMD assembly, and sheet with recorded measurements
  1. Parts list (in order of use)
  1. Hybrid tracking sheet
  2. SMD thick film circuit board assembly
  3. Ceramic subplate
  4. Gluing jig
  5. Round Al washer
  6. Rectangular Al plate with hole
  7. Two pieces of mylar, both longer and wider than the subplate
  8. Dexter Epoxy Patch
  9. Al plate with flat edge to spread epoxy
  10. Anti-static cloth squares
  11. Two (2) white plastic alignment pieces
  12. T.F.E. Dry-lube (Teflon) spray
  13. Weights (bolts with tops covered with plastic)
  14. Transport box
  15. Oiler for applying glue drops
  1. Inspecting & cleaning
  1. Subplate should be smooth on the top and the bottom.
  2. Check SMD for good chip bond pads
  3. Look for any obvious scratches or shorts in pads and lines.
  4. Check for loose components or components that are badly out of alignment with their contact pads
  5. Check subplate for metal or ceramic chips or other debris
  6. Clean components (subplate, Al pieces, and plastic pins) with alcohol. Do not clean SMD assembly
  2. Gluing
  1. Check jig setup. Al pin should be on the left for right-handed hybrids and on the right for left-handed hybrids. Hybrids are labeled according to whether the connector is on the left or right when the chip pads face you.
  2. Do a fit check of all pieces, they should fit together and into the jig slots
  3. Jig gets wiped occasionally with T.F.E. Dry-lube.
  4. Mix epoxy in small plastic bowl or on the mylar sheet. (~1" length of bead is needed)
  5. Spread epoxy on one piece of mylar, reserving some for the Al pieces.
  6. Put second piece of mylar on top
  7. Use the straight edge of a piece of Al to spread the epoxy into a very thin layer between the mylar pieces. If the epoxy looks cloudy, it’s too thick.
  8. Separate the two pieces of mylar
  9. Press the ceramic subplate onto one of the pieces of mylar. Avoid getting epoxy on edges.
  10. Remove the mylar, check edges of the subplate for epoxy, and place it in the jig, epoxy side up
  11. Make sure ceramic butts against the pin in the jig
  12. (Optional) Add 3-4 small (diameter about 1 mm or less) dots of epoxy evenly spaced across the top of the ceramic
  13. Place the SMD assembly down on top of the subplate. It can be placed 2-3 mm away from the jig post and then slid towards the post to spread epoxy. Try to lay it down front to back. Avoid sliding parallel to the short edge. Make sure it is in the slot in the jig.
  14. Press SMD down gently with anti-static cloth squares
  15. Add a small amount of Dry-Lube to the point of the plastic pins. One option is to spray in the cap and then wipe on the pins. Spray away from work area.
  16. Put Al washer on end of plastic pin and then place in circular cutout near jig post. A small amount of added epoxy is needed, but be careful not to use too much. Repeat for rectangular Al piece at the other end.
  17. Make sure plastic pins are inserted into the subplate. Rectangular pieces should be aligned with the edge of the SMD assembly.
  18. Put weights on top of SMD assembly, cushioned with anti-static cloth
  19. Re-check alignment in jig and plastic pins
  20. Make sure everything is flat and in its correct slot or hole
  21. About 2-3 hours later, gently lift the hybrid and rotate the plastic alignment pins to make sure they're not stuck. Check for excess epoxy which can be cleaned carefully with alcohol
  22. Allow to cure overnight, at least 12 hours
  23. Keep epoxy cup or mylar sheets next to jig
  1. Finishing
  1. Check that epoxy has cured properly
  2. Carefully remove plastic pins, clean and put in proper storage box
  3. Carefully remove hybrid from jig
  4. Check for blocked holes, excess epoxy squeezed out, etc.
  5. Store hybrid in transport box
  6. Check jig for excess glue, clean and store
  7. Have expert check final result, possibly adding epoxy reinforcement
  8. Record gluing step in the database