go ag-19 and farm for field telephones. They each gives 1 circuit board when salvaged. I cant say thats faster, you must be lucky but thats the only 2. way i know.

over a year old i know but the current two ways is AG-19 like he said or farming intel from fort knell and trading them in at the intel trader (if done correctly every run [4-5 filters] should net you around 3-4 (on harder difficulties))