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decap:epoxy_acid [2018/04/29 17:06] – [Nitric acid mixtures] mcmasterdecap:epoxy_acid [2025/02/03 06:42] (current) – [Rosin] mcmaster
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 ====== Live decap millling ======  ====== Live decap millling ====== 
 +
 +{{:mcmaster:decap:epoxy_acid:endmills.jpg?400|}}
 +
 +Above: HSS endmills are relatively inexpensive (above were about $3 each) and work reasonably well. They may be a better option than more expensive endmills that last slightly longer
 +
 +2021-12-29: McMaster has recently been using RFNA (instead of WFNA) which seems to be much faster on epoxy. Fast enough that I'm no longer pre-milling chips. This tends to be faster overall and removes risks of milling (damaging bond wires, etc)
  
 General recommendation for pre-milling packages General recommendation for pre-milling packages
  
-^ Package  ^ Package thickness  ^ Package width  ^ Depth target     ^ Endmill size    ^ +^ Package  ^ Pin pitch  ^ Package thickness                 ^ Package width  ^ Package length  ^ Depth target     ^ Endmill size    ^ Notes                                                                                                                                                                                                                                                                            ^ 
-| PDIP8    |                    |                |                  |                 | +| PDIP8    | 0.3"       |                                   |                |                 |                  |                 |                                                                                                                                                                                                                                                                                  | 
-| PDIP18   | 0.13               | 0.25"          | 0.030 to 0.035   | 3/16 (0.1875)"  | +| PDIP18   | 0.3"       | 0.13                              | 0.25"          |                 | 0.030 to 0.035   | 3/16 (0.1875)"  |                                                                                                                                                                                                                                                                                  | 
-| PDIP28   | 0.15               |                | 0.035 to 0.040"  | 3/8" (0.375)"               | +| PDIP28   | 0.3"       | 0.13                              | 0.27"          | 1.39"           | 0.030 to 0.035   | 3/16 (0.1875)"  |                                                                                                                                                                                                                                                                                  | 
-| PDIP40   | 0.15               |                | 0.035 to 0.040"  |                 |+| PDIP28   | 0.5"       | 0.15                              |                |                 | 0.035 to 0.040"  | 3/8 (0.375)"    |                                                                                                                                                                                                                                                                                  | 
 +| PDIP40   | 0.5"       | 0.15                              |                |                 | 0.035 to 0.040"  | 3/8 (0.375)"    |                                                                                                                                                                                                                                                                                  | 
 +| TO-99    |            | Ceramic: 0.11\\ Epoxy: 0.07 peak  | 0.31"          |                 | 0.018 to 0.023"  | 1/8 (0.125)"    | UL914\\ "30 mil down just cut one bond wire"\\ Pins leave about 0.16" center area. However, die is not centered, maybe 0.08" actual center area => 1/8" endmill works well\\ old note: "epoxy layer at its thickest is about 1.6 mm" => 0.063", maybe be more careful on depth?  |
  
 Don't cool the bit. Heat weakens epoxy. You will go through bits relatively quickly. Carbide bits do last longer, haven't figured out yet if they are cost effective. Be sure to replace a bit if its not cutting well. Don't cool the bit. Heat weakens epoxy. You will go through bits relatively quickly. Carbide bits do last longer, haven't figured out yet if they are cost effective. Be sure to replace a bit if its not cutting well.
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   * A few chips have higher bond wires than typical   * A few chips have higher bond wires than typical
  
 +Suppliers: 
 +  * 1/8 / 3 mm 
 +    * https://www.ebay.com/itm/231362129393?&autorefresh=true 
 +      * 1PCs 1/8''x1/4'' 4 Flute End Mill Cutter Milling Slot Drill Bit HSS 
 +      * 2019-12-26: qty 10 for $20.93 shipped ($2.09 each) 
 +    * 5Pcs/Pack Carbide Flat End Mill 4-Flute Mentalworking CNC Tool 3mm Cutting Dia 
 +      * 2019-12-26: qty 5 for $15.25 ($3.05 each) 
 +    * https://www.ebay.com/itm/303339639134 
 +      * 3mm Carbide End Mill 4-F CNC Milling Cutter Bit 3*4*50L 55° VHM coating *5pcs 
 +      * 2020-09-06: qty 15 for $43.24 ($2.88 each)
  
 ====== Copper bond wires ======  ====== Copper bond wires ====== 
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   - Optional: mill out a cavity about the size of the die   - Optional: mill out a cavity about the size of the die
   - Place IC in petri dish on hot plate   - Place IC in petri dish on hot plate
-  - Heat to 150C+  - Heat hot plate to 100C
   - Place one drop of FNA (possibly mixed with concentrated sulfuric) on center of chip   - Place one drop of FNA (possibly mixed with concentrated sulfuric) on center of chip
   - Wait a few seconds   - Wait a few seconds
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 Low cost technique using readily available materials. Low cost technique using readily available materials.
  
-Procedure+Sample procedure
   - Heat bath to desired temperature   - Heat bath to desired temperature
-    * The solution will start forming black whisps when it reaches minimum temperature.  Approx 150C is common. +    * TLDR: 200C is a good starting point  
-  - Cook until done.  Time varies greatly with temperature and epoxy+  - Cook until done 
 +    * TLDR: check every 15 minutes at 200C 
 +    * Time varies greatly with temperature, epoxy type, and thickness 
 +    * Solution opaque => difficult to monitor. You might need to pour to another container to check 
 +    * That said, probably on the order of 10s of minutes for 200C 
 +    * 350C will take seconds even for a thick chip 
 +  - Pour off as much acid as possible and then rinse chip in acetone
  
 Notes Notes
   * Temperature   * Temperature
 +    * The solution will start forming black whisps in solution when it reaches minimum temperature.  Approx 150C is common
     * Higher temperatures make it go faster.  I use about 200C as a compromise between fumes and working time     * Higher temperatures make it go faster.  I use about 200C as a compromise between fumes and working time
     * At about 300C fumes are a huge problem but I did decap a large plastic chip in about 10 seconds      * At about 300C fumes are a huge problem but I did decap a large plastic chip in about 10 seconds 
     * It may work best to reflux the acid as it will boil off rapid above about 275.  I use a watch glass to cover the beaker which helps considerably and is easy     * It may work best to reflux the acid as it will boil off rapid above about 275.  I use a watch glass to cover the beaker which helps considerably and is easy
-  * Water severely reduces effectiveness.  If a chip is inspected and washed, wash with acetone and then bake briefly on hot plate before adding back to solution+  * Water severely reduces effectiveness 
 +    * Use acetone instead of water if possible 
 +    * If a chip is inspected and washed with water, wash with acetone and then bake briefly on hot plate before adding back to solution
   * I put chips into a PTFE basket (drilled out smaller beaker) so that they can be quickly removed and inspected without cooling down the acid bath   * I put chips into a PTFE basket (drilled out smaller beaker) so that they can be quickly removed and inspected without cooling down the acid bath
-  * As the acid concentration drops it begins to boil up.  This is extremely dangerous and can lead to boiling over.  Mitigation: use big beakers, ideally 10 times as large as liquid level.  It also helps to use excess acid as things work faster anyway+  * As the acid concentration drops it begins to boil up.  This is extremely dangerous and can lead to boiling over 
 +    * Ideally use more acid as this will also decap chip quicker 
 +    * Using big beakers also helps, ideally 10 times as large as liquid level
 {{:mcmaster:decap:epoxy:boiling_h2so4_sludge.jpg?300|}} {{:mcmaster:decap:epoxy:boiling_h2so4_sludge.jpg?300|}}
   * Sulphuric eats most metals, although slowly. Expect pins and such to still be in tact, but the bond wires will likely break without any support   * Sulphuric eats most metals, although slowly. Expect pins and such to still be in tact, but the bond wires will likely break without any support
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-====== H2SO4 + FNA ======+===== H2SO4 + FNA =====
  
 {{:decap:hno3_h2so4_swollen.jpg?300|}} {{:decap:hno3_h2so4_swollen.jpg?300|}}
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 WARNING WARNING WARNING: this is very dangerous.  The mixture will instantly explode upon contact with many organics.  Not recommended, was more of a curiosity.  In short, a mix of these two will decap a chip much faster.  At room temperature the sample chip swelled up in addition to dissolving.  See [[http://uvicrec.blogspot.com/2012/06/cold-nitric-acid-experiments.html|Cold nitric acid experiments]] for details. WARNING WARNING WARNING: this is very dangerous.  The mixture will instantly explode upon contact with many organics.  Not recommended, was more of a curiosity.  In short, a mix of these two will decap a chip much faster.  At room temperature the sample chip swelled up in addition to dissolving.  See [[http://uvicrec.blogspot.com/2012/06/cold-nitric-acid-experiments.html|Cold nitric acid experiments]] for details.
  
 +
 +===== Drain Pipe Opener =====
 +
 +Some strong drain pipe openers are essentially Piranha solutions. Based on my experiments, this solution has worked great for most epoxy packages. It is also very easy to obtain in many countries and regions without any regulation, making it a good alternative to sulfuric acid. 
 +
 +That said, it's just as dangerous as concentrated sulfuric acid, so it should be treated with extreme caution and protection of PPEs.
 +
 +The only downside is that it eats away metal and bonding wires.
 +
 +Drop the chip in a beaker and submerge it in the solution. Heat the solution to boiling (warning: intense smoking will occur), and wait about 1.5 hours until the die is fully exposed.
 +
 +My personal recommendation is the Black Swan "Zap" 51996 Sulfuric Drain Opener, but similar-looking drain pipe openers should have the same ingredients.
 +
 +{{:decap:epoxy:pipe_opener_zap.jpg?100}} {{:decap:epoxy:pipe_opener_result.jpg?300}}
  
  
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 ====== Rosin ======  ====== Rosin ====== 
 +
 +https://ic.onidev.fr/en/die/rosin_decap.html
 +
 Boil a chip for a few hours in rosin, like used for soldering. Refluxing equipment is ideal. Should eat away the casing. Might be best used with Dremeling or other techniques to remove the majority of the epoxy first. The active ingredient for this is abietic acid. Boil a chip for a few hours in rosin, like used for soldering. Refluxing equipment is ideal. Should eat away the casing. Might be best used with Dremeling or other techniques to remove the majority of the epoxy first. The active ingredient for this is abietic acid.
  
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 There's a fine line between laziness and efficiency. I don't judge. There's a fine line between laziness and efficiency. I don't judge.
- 
  
 ====== References ====== ====== References ======
   * http://zeptobars.ru/en/read/how-to-open-microchip-asic-what-inside   * http://zeptobars.ru/en/read/how-to-open-microchip-asic-what-inside
-  * CDCA: http://www.ecpe.org/fileadmin/_recycler_/07_Kerisit_Tools_Dedicated_to_Chip_Access.pdf+  * CDCA: 403 errors (as of Nov 2023), archived in Wayback Machine: http://web.archive.org/web/20180106035620/http://www.ecpe.org/fileadmin/_recycler_/07_Kerisit_Tools_Dedicated_to_Chip_Access.pdf 
 +    * Original URL: http://www.ecpe.org/fileadmin/_recycler_/07_Kerisit_Tools_Dedicated_to_Chip_Access.pdf
  
decap/epoxy_acid.1525021611.txt.gz · Last modified: 2018/04/29 17:06 by mcmaster