I just tested a new type of chips - SMALL BGA chips, like in newer RAM memory types (DDR2/DDR3), and the similar chips from motherboards and cards. They are all small, square or rectangle shaped, and all of them have a foil base with solder balls.
I soaked the chips in concentrated HCl and bring them to boil 3 times, the most of the tin dissolved. I incinerated the chips and washed with water. This time i used poorman's AR with KNO3. There was still some tin left so it took me some time to filter the solution with metastannic acid. I dropped the gold with SMB and washed the gold powder with hot water. I redissolved the gold again with poorman's AR to be sure that all of the contaminants are gone. I waited until AR was crystal clear and the contaminants like silver chloride and metastannic acid was settled at the bottom, then i carefully decanted the AR solution through the filter paper and dropped the gold with SMB again. I rinsed the gold powder with hot distiled water 3 times/3 times with hot HCl/3 times with hot distiled water. i dried the gold, measured it and here are my results...
View attachment 30335
Total weight of chips: 233.7g
Number of chips: 919pcs
Average weight of one chip: 0.25429815g
Gold recovered: 1.1g
Avg. gold per 1kg: 4.706889g
Avg. gold per one chip: 0.001196953g