The printed circuit board industry has long been interested in the ionic cleanliness of printed board surfaces and its correlation with corrosion, electrochemical migration, dendritic growth, and subsequent opens, leakage current, or shorting during testing and in the field. Initial methods for cleanliness evaluation included resistivity of solvent extract (ROSE) that measured the conductivity of a solution after flowing it over a surface of interest. A major disadvantage of this technique was its inability to detect specific ionic species generating the measured conductivity. Ion chromatography (IC) has recently become an important technique for the evaluation of ionic cleanliness. This technique, which detects individual ions, allows quicker trouble–shooting of contamination sources and better predictions about the detrimental effects of each ionic species. It is able to measure concentrations of major anions, such as chloride and bromide, as well as major cations such as sodium, ammonium, and potassium at low parts–per–million (ppm) and even parts–per–billion (ppb). Concentrations of weak organic acids (WOAs) can also be measured by IC. This application note describes an IC method using a Dionex IonPac AS11-HC-4μm column and Dionex ICS-5000+ HPIC system to determine extractable anionic contaminants on the surface of PCBs including inorganic anions and weak organic acids following the extraction procedure described in IPC-TM- 650 Method 2.3.28. The 15 anions mentioned in the IPC Method are bromide, chloride, fluoride, nitrate, nitrite, phosphate, sulfate, acetate, adipate, formate, glutamate, malate, methane sulfonate, succinate, and phthalate. Our method addresses all anions but glutamate that contains a α-amino group, and α-carboxylic acid group, and a side chain carboxylic acid, and therefore is possibly removed during the suppression process.

Determination of anions on the surface of Printed Circuit Boards (PCBs) by IPC-TM- 650 method 2.3.28 using HPIC

253rd National Meeting (2017)

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