[[decap:epoxy]]
 
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decap:epoxy [2018/02/28 06:55] – [A. Zonenberg etch rate measurement] mcmasterdecap:epoxy [2020/02/27 20:57] – mcmaster
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 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. 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 =====
 +
 +{{:mcmaster:decap:epoxy:cob_silicone.jpg?600|}}
 +
 +Experiments trying to decap COB while keeping PCB intact
 +
 +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
 +
 +Above is a compromise between PP providing the best chemical resistance and silicone providing the best seal
 +
 +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
 +
 +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
  
  
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   * They do the whole chip but avoid die area   * They do the whole chip but avoid die area
   * Light Ray - IC Decapsulation   * Light Ray - IC Decapsulation
 +
 +
 +===== mcmaster ezlaze =====
 +
 +TODO: add pictures, estimate material removal rate
 +
 +Basically this was too slow to be practical except for very small samples. That said, it did work very well. A quicklase or other higher throughput Nd:YAG system would likely work well
  
 ====== Sandblast ====== ====== Sandblast ======
 
decap/epoxy.txt · Last modified: 2023/09/04 07:42 by mcmaster
 
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