co

lo

pho

ny

Well, yes. I found
an article written by the CCC guys who popularized this technique a few years ago. Perhaps the most important part:
In "Präparationstechniken für die Fehleranalyse an integrierten Halbleiterschaltungen" von Friedrich Beck aus dem Jahr 1988 habe ich einen Hinweis auf die Entkapselung mittels Kolophonium gefunden. Kolophonium enthält Abietinsäure (etwa 40%). Beck schreibt: "Zum Öffnen wird das Bauteil im Drahtkörbchen in das auf 320 - 360 °C erwärmte Kolophonium getaucht, bis der Chip völlig freiliegt (5 - 10 Minuten); anschließend läßt sich mit trockenem Aceton das anhaftende Kolophonium entfernen." (S. 19, 20) Beck schreibt ferner, dass die Kolophoniumrückstände den Abzug versiffen und das schwer zu entfernen ist. Dies sei der Grund, warum das Verfahren selten angewandt wird.
As far as I understand, they say that the whole idea came from an old German book about semiconductor failure analysis, and according to the book, temperature of 320~360°C is required and it must be maintained for 5~10 minutes because that's how long the reaction takes. Also something about this technique rarely being used in practice because colophony messed up fume hoods

The rest of the article describes author's own experiments, and they were less happy because the process worked, but took an hour or two per chip. However, the author says nothing about any attempts at precise temperature control, he just used a spirit burner.
Well, I thought that I will be clever and perhaps manage to achieve reasonable speed by regulating temperature precisely in the recommended range. I loaded my old thimble cooker with colophony and two different SO8 chips, connected it to a variable DC power supply, shoved a thermocouple in it and adjusted power to reach and maintain progressively increasing temperatures above 300°C. (I tried 270°C for two hours previously, so it surely made no sense to bother with less than 300°C).
15 minutes at 320~330°C. There were small bubbles and some smoke coming, nothing terrible.
15 minutes at 330~340°C. Similar to above. Some colophony lost, but not a lot.
Then I refilled and tried to hit 350~360°C, but it ended up more like 360~380°C. Now, bubbling and smoking got much worse and colophony was disappearing faster.
After another 10~15 minutes, there was almost nothing left so I turned it off.
And the outcome? Almost nothing. Maybe the chips are a little smaller than initially, but surely not dissolved fully or even significantly. I have no patience to wait a few hours and see what happens.
This guy says it should be a few minutes. At this point I don't understand what's going on. At least I know that it isn't about temperature - less than 300°C is completely ineffective, and 400°C or more is lots of smoke and colophony gone.
Maybe there is something wrong with my colophony. I use some "activated" colophony for soldering. I will look if I can find unprocessed natural colophony somewhere. Other than that, no idea
