Differences

This shows you the differences between two versions of the page.

--- decap:epoxy [2018/02/27 22:03] – mcmaster
+++ decap:epoxy [2023/09/04 07:42] (current) – mcmaster
@@ Line 133: / Line 133: @@
 One problem from this lack of circulation is that it may create pockets of low concentration acid, leading to corrosion.  The above dies were washed before that picture was taken to remove copper nitrate residue that had built up.  It probably came from a paddle but may have come from the PCB.  After rinsing with water, the bottom of the die was CA glued down.  Then the back of the die was gently cotton swapped with acetone.  Finally, the whole thing was soaked in acetone to release the die.
+===== McMaster live 2019-11-10 =====
-====== Live analysis considerations ======
+{{:mcmaster:decap:epoxy:cob_silicone.jpg?400|}}
-Commercial "automatic" machines use a variety of techniques to etch the IC appropriately. One such technique is to seal off the area under attack using a chemically inert gaskit. See nitric acid gasket compatibility chart[9].
+Experiments trying to decap COB while keeping PCB intact
-Sulphuric acid may be added to nitric acid to help preserve copper, if present (see the acid page for details).
-====== Laser ======
+TLDR best result
+  - Cut a polypropylene tube (ie from a microfuge tube) roughly the size you want to expose to acid
+  - Heat tube up to soften it
+  - Warm PCB
+  - Attach hot tube to PCB, letting plastic deform into place
+  - Let cool a little
+  - Seal outside of tube with silicone
+  - Let silicone cure
+  - Decap with gentle heat on hotplate (maybe 160F max) using 2 WFNA : 1 H2SO4
-General results
+Above is a compromise between PP providing the best chemical resistance and silicone providing the best seal
-  * Some settings work decent
-  * Risk of melting bond wires and/or die
-    * Use lower power and/or pulsed?
-  * Practice on samples before trying something you care about
-  * Puts off nasty fumes. Make sure to have good ventilation
-===== jamiecraig =====
+{{:mcmaster:decap:epoxy:silicone_surface.jpg?400|}}
-{{:decap:epoxy:laser_chip_p8211261.jpg?400|}}
+Above: hardened silicone bubbles on WFNA surface
-Above: laser decap from below ([[https://www.jamiecraig.com/wp-content/uploads/2015/08/P8211261.jpg|Source]])
+Silicone only experiment
+  * Made silicon dam by layering up
+  * Silicone surface cured, but internally didn't always
+  * Uncured silicone dissolved in WFNA and floated to top. This then cured and blocked the surface
+    * Interesting, but not what I was looking for
+  * Acid may eventually undermine the PCB, but eating the silicone itself came first
+  * Consider using a lot more silicone than you need to help mitigate acid splashes
+    * Maybe cover board surface with kapton?
-https://www.jamiecraig.com/de-encapsulating-ics-with-a-laser-cutter/
+Someone also suggested I should try PTFE gasket. In the past I had tried kapton which didn't work well (acid tended to wick into kapton). Maybe PTFE would repel acid better
-  * Seemed to work okay
-  * What would it look like if touched up with WFNA?
-===== EMSL 6502 test =====
+Reference: https://twitter.com/johndmcmaster/status/1193807272171827200
-{{:decap:epoxy:img_20180227_101636.jpg?400|}}
+====== Live analysis considerations ======
-Above: poor results. Maybe from CO2 laser (source: photo by mcmaster from EMSL test)
+Commercial "automatic" machines use a variety of techniques to etch the IC appropriately. One such technique is to seal off the area under attack using a chemically inert gaskit. See nitric acid gasket compatibility chart[9].
+Sulphuric acid may be added to nitric acid to help preserve copper, if present (see the acid page for details).
-===== Silicon Exposed =====
-{{:azonenberg:laser_08_df_neo10x_annotated.jpg?400|}}
+====== Laser ======
-Above: [[http://siliconexposed.blogspot.com/2013/08/laser-ic-decapsulation-experiments.html|source]]
-http://siliconexposed.blogspot.com/2013/08/laser-ic-decapsulation-experiments.html
-  * Poor results
-  * Cranberry glass
-===== Misc =====
-https://www.youtube.com/watch?v=-x4lyX1C4q0
-  * Gold backing block
-  * Good leadframe exposure
-  * Die unclear how well exposed
-  * Scanned entire chip (including die area) up until the end
-https://www.youtube.com/watch?v=2HMocYiwMYc
-  * Cavity into pic
-  * Gives a close up at the end
-https://www.youtube.com/watch?v=SvWgSs2_f00
+[[decap:laser]]
-  * Laser Decapsulation FALIT System Software | Image Templates
-  * Pro system demo
-https://www.youtube.com/watch?v=sSRl3Vqbos8
-  * They do the whole chip but avoid die area
-  * Light Ray - IC Decapsulation
 ====== Sandblast ======
@@ Line 269: / Line 254: @@
-====== A. Zonenberg etch rate measurement ======
-FIXME: move this somewhere better
-Copper etch - 70 ml 3% H2O2 + 10 ml conc. HCl. Heat to 70C, agitate with magnetic stirrer.
-Test sample was Altera Stratix IV. Silver or tin plated copper. Plating was gone after <1 min in etchant, metallurgy of the plating was not studied. 20 minutes of etching = 0.13mm removal so 6.5 um/min. This number is likely +/- 30% or so because the temperature of the solution slowly increased over the etch period.
 ====== References ======