Especially pins in plastic take longer to dissolve and will cement your values on the base metal inside the plastic leaving it stuck in there.
The lesson learned is worth more than the gold lost.
Never throw a bunch of different e-waste together. Different approach for each type, some you can combine together in e.g. AP.
Save your nitric for refining.
Yep, I watched and listened to SO MANY vids from dozens of scrappers for 8 months before I even began, learning about each component, how they've changed over the years in composition, how to sort even the same types based on materials used in them year-to-year (which is CRITICAL for capacitors, they have so many types! Modern large capacitors are pretty much garbage. MLCCs after the year 2000 are useful only for people who are skilled at nickel recovery, which is a consideration with nickel now passing $12/lb, roughly 2.5 times the current price of copper.
Chips (especially the long IC chips with many leads from older boards), I found out, often have a higher amount of silver in them than any other PM... so the general 'wash them with HCl' to remove base metals can be a very bad idea, as that will create silver chloride that will be almost impossible to recover from the mess of chip dust. They also frequently have palladium-plated tips on the inside portions where the nano-wires attach... which themselves are unpredictable: gold, palladium, platinum. So you must assume ALL of them are present in a random bag of mixed IC chips.
I'll be trying a batch of crushed chips with mild sulfuric acid first, then more concentrated sulfuric (once I have my SO2 recovery apparatus setup! I plan to get as much life out of my reagents as physics and chemistry allows!) Any silver and palladium dissolving there can then be cemented out on copper and refined (some other metals will cement out, but in general the Ag and Pd will be much more concentrated after this cementing and easier to purify). Gold and platinum, conversely, will not be touched. So those metals will be left in the chip mush for traditional gold and platinum recovery methods, with little other metal remaining.
The HIGHLY toxic solution full of many many transition metals from the sulfuric steps will be cemented with iron to recover as much copper as possible, then evaporated, and roasted into oxide powder over modest heat (driving off the sulfate mainly as SO2, which can be enhanced by mixing with carbon with an oxygen feed or mixing in some sodium carbonate). Again, the gas capture apparatus will grab the fumes.
Ideally, I'd have preferred to use nitric acid, since nitrates decompose so nicely. But the sheer amount of goo generated from using nitrate on e-waste (tin, aluminum, bismuth, and a few other metals and metalloids form insoluble sludge in nitric) makes it implausible.