The ionic contamination on printed circuit boards (PCB) having different surface finishes was examined\nusing ionograph. The study was performed at the RT on three types of PCBs covered with: (i) hot air solder\nleveling (HASL LF), (ii) electroless nickel immersion gold (ENIG), and (iii) organic surface protectant\n(OSP), all on Cu substrates, as well as two types of fluxes, namely EF2202 and RF800. In the group of\nboards without soldered components, the lowest average value of contamination was for the ENIG 18 ?m\nsurface (0.01 ?g NaCl/cm2). Boards with soldered components were more contaminated (from 0.29 ?g\nNaCl/cm2 for the HASL LF 18 ?m surface). After spraying boards with fluxing agents, the values of\ncontaminants were the highest. The influence of phosphorus content in Ni-P layer of ENIG finish on ionic\ncontamination was examined. In the group of PCBs with Au coating, the smallest amount of surface\ncontaminants (0.32 lg NaCl/cm2) was for Ni-2-5%P layer. PCBs with Ni-11%P layer were higher contaminated\n(0.47 ?g NaCl/cm2), and another with Ni-8%P layer had 0.81 ?g NaCl/cm2. PCBs without Au\ncoating, had the lowest contamination (0.48 ?g NaCl/cm2) at phosphorous content equal 11%P. Higher\ncontamination (0.67 ?g NaCl/cm2) was at 2-5%P, up to 1.98 ?g NaCl/cm2 for 8% of P. Boards with Au\nfinish have lower value of contamination than identical boards without Au layer thus contributing to better\nreliability of electronic assemblies, since its failures due to current leakage and corrosion can be caused by\ncontaminants.
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