https://twitter.com/johndmcmaster/status/640699417897517056

• Lapping films applied more evenly using silicone rolling pin

https://twitter.com/johndmcmaster/status/640701284673155076

• Excessive pressure caused die to dig into lapping film

https://twitter.com/johndmcmaster/status/643284839097962496

• Acquired 1 um and 3 um lapping films for removing upper layers quicker

https://twitter.com/johndmcmaster/status/643284509564145664

• Tried to use 3 um film on virtex die (waxed to SBT jig) and removed center before sides
• Every previous lapping attempt I've done removed the edges first
• Unusually large die: possibly wax accumulated in center causing bulge

Virtex die

• Mostly decapped already by soaking in WFNA for a few days
• Used piranha etch to clean up
• Discovered remaining black epoxy/silicone doesn't quickly etch in piranha
• Still have a pile of ones that require decap cleanup
• Should have plenty for lapping R&D for a while
• Decapping: https://twitter.com/johndmcmaster/status/642410779304570880
• Bulk package removed via hotplate + pliers: https://twitter.com/johndmcmaster/status/642406536854138880
• Original chips: https://twitter.com/johndmcmaster/status/641020243159052288

Lapping stencil

• Idea: try to get closer to wafer lapping by not gluing chip down
• Requires making a stencil to hold die in place
• Use wax to affix stencil to fixture
• Still using lapping films. Looking into getting condition rings + cast iron plate