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--- tutorial:lapping [2012/03/19 04:59] – mcmaster
+++ tutorial:lapping [2015/01/21 07:54] (current) – mcmaster
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 by John McMaster
+-01-20: shot a video, needs to be edited.  Should have some good details
 This tutorial will go through the details of what is needed to setup a lapping machine and basic usage.
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 I found colloidal silica to be a little irritating the first time I tried it without a lapping machine.  I think this was because I had to apply more pressure to make up for the lack of moving equipment as I didn't have any problems when using the lapping machine.  That said, watch out and consider alternatives if its bothering you.
+====== Why? ======
+Lapping relies on mechanical properties to take a slice out of an IC to show a single layer.  This sort of view can be very intuitive, especially in planarized chips.  Note that non-planarized chips may not give as good as results but it can still be useful.
+Heres an example of what you can get out of non-planarized chips (FIXME: these aren't aligned):
+{{gallery>:tutorial:lapping:sram_top_metal.jpg|}}
+{{gallery>:tutorial:lapping:sram_lapped.jpg|}}
 ====== Setup ======
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 ====== Tips ======
+Your finger will turn white from contact with the silica.  SiO2 is non-toxic and only and issue if its irritating you skin.  My experience seems to show that irritation probably means you are applying too much pressure.
+{{gallery>tutorial:lapping:finger.jpg}}
 Always wet your finger before picking up a die.  If it falls onto the lapping disk if you are lucky it will safely hit the splash guard.  If you are unlucky it will ricochet across the room and shatter against something hard.  Consider setting up a plastic sheet around the machine to minimize the impact of this if you have a valuable sample or use a jig.
 I have a portable microscope (as opposed to my main which is expensive and weighs several hundred pounds) dedicated for wetwork that makes quickly checking out the sample convenient.
+{{gallery>tutorial:lapping:overview_with_microscope.jpg}}
 If you find it takes you 20 minutes to get through though you are probably either not going fast enough or not applying enough pressure.
+Jigs can be used to take off precision layers but may be overkill for simple analysis.  When CT was asked about them he said he had lapping fixtures but didn't use them.  A lot of his pictures have uneven lapping so hes probably just interested in exposing a single area.  If one wanted full die photographs though they might be a good idea.
 ====== Removing an old disc ======