Leakage evaluation circuits

The level of surface cleanliness may also be evaluated by measuring the surface-insulation resistance (SIR) of a separate test pattern. The SIR test sample consists of an interdigitated comb pattern of conductor lines and spacings on a printed-circuit laminate representative of the actual circuit. The IPC B-25 or IPC B-24 test patterns (Fig. 4.3) are standard in the industry to evaluate the degree of cleanliness of a surface. If the test pattern is well cleaned and no ionic residues remain, the insulation resistances between conductor lines will be 10 ohms or greater and will not drop appreciably under moist ambients. If residues remain, leakage currents... 

---