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McMaster notes

2021-04-21

Goal: set RP2-B0 in wax on Allied sample holder
RP2-B0
- Decapped 2x “live” from photo shoot to bare die
- Around 277 um thick. Later measurement 281 um
Sacrificial dies
- Samsung k4h560438e-tcb0
- 324 um
Area
- Samsung: 5.3 x 11.1 = 58.8 mm2
- RPI: maybe 4 mm2
- Net: maybe 60 mm2
Etchant: 20% w/v KOH in water
- https://cleanroom.byu.edu/koh
- Approx 250 um / hour heated ⇒ 4.15 um / min
Etch
- Etch 1
  - 25 min @ 177F hotplate
  - 306 um
- Etch 2
- 30 min?
  - raised temp?
  - 297, 302 um
  - High spots forming (was warned might be uneven at this conc)
- Etch 3
  - Now hotplate at 220F
  - 286 um, 291 um
  - 14 um in 30 min
  - (286 - 277) * 2 = 18 more min?
  - Lots of metal flaking off
- Etch 4
  - 20 min
  - Ultrasound. Lots of stuff flaked off
  - Didn't note final thickness…
Check all dies for thickness before mounting
- Not all started at exactly the same time, although was close
Order replacement lapping gauge
- 543-452B, ID-C125EB
  - 1 um resolution
  - 25 mm travel
  - Long
  - Flat carbide tip. Will need to switch to new unit
- Skips
- Can't modify spares to be long enough
- One that might work I can't get to power up. Completely broken?
Set in wax
- 0.4 mm gap in area(s). Not ideal but may still work

Goal: setup lapping machine, lap RPI chip from other day

TODO:

Inventory:

2x MultiPrep systems w/ arm
- Both were surplus / in bad condition
- One is more “ready to go”
Lots of lapping disks
Is my old colloidial silica still good?

Notes:

Installed old magnetic polishing cloth
Post 1.49“
- Could I mount stopcock to it somehow?
Main crank 40 TPI
- Wheel is marked in um (635 um)
Allied-Parallel-Lapping-Integrated-Circuits.pdf
- If gauge is moving its already too much pressure
- Instead use recommended distances
- Based on 500 um die
- Imperial Polishing Cloth, #50-150-500: 0.840 mm