decapsulation

3 methods:

first - by fuming nitric acid

Procedure:

1: heat the unit on the 140'C hot plate.
2: drip few fuming nitric acid at the middle of unit by using plastic sucker.
3: after observed the reaction between mold compound n acid, use tweezer to pick up the unit n wash with acetone.
    (nitric acid can be neutralized by acetone)
4: continue step 1 to step 3 until whole die expose.

-do not overheat the unit, once the mold compound heat up above a certain temperature, it is very difficult to decap.
-during the driping period, once saw the reaction, need to pick up the unit quickly to avoid the waste of reaction form a dirty layer on the unit. the layer is very difficult to be removed.

second - by fuming sulfuric acid

1: heat the unit on the 245'C hot plate.

2: drip few fuming sulfuric acid at the middle of unit by using glass sucker.
3: after observed the reaction between mold compound n acid, use tweezer to pick up the unit n wash with water.
(sulfuric acid can be desolved in water)
4: continue step 1 to step 3 until whole die expose.

-normally the temperature of hot plate will be higher because although the plate showed 245'C but internal part of unit may not be that temperature. higher the temperature speed up the decap speed.

third - by fuming sulfuric acid with jek etcher

1: after the temperature reach the required temperature (245'C), perform dummy etch with jek etcher before use to decap unit. (perform half of the time of unit etching)
2: try to the kapton tape to cover the area of unit which do not required to be etched.
3: after finished dummy etch, put unit inside the machine and let it run.
4: wash with alcohol following with unit ultrasonicifation by using alcohol.
5: washed with water.

-when finished the decapsulation with jek etcher, dummy etch is needed to run one more time to clear the dirt left on the     machine.
-unit is covered by using cover model corresponding to the unit package type.