SMT007 Magazine

SMT-Aug2018

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AUGUST 2018 I SMT007 MAGAZINE 31 The visual inspections for electrochemical migration and corrosion after SIR testing are performed at 30–40X magnification in light field and dark field lighting. Localized Extraction and Cleanliness Testing System This test system utilizes a steam head (Figure 2) to extract a sample of deionized water and flux residue effluent from a localized region of approximately 0.1 in 2 (6.45 mm2). The test system is designed to extract the flux residue effluent by heating deionized water and deliv- ering it to the test site (red arrow in Figure 2), followed by a vacuum aspiration of the solu- tion into the collection reservoir (blue arrow in Figure 2). This cycle is performed nine times to produce a volume of effluent sufficient to fill the collection reservoir to a point where the exposed traces on the test coupon are covered. The test system applies a known bias (10 VDC) across the test coupon electrodes and measures the resulting current every 0.25 seconds. The test system provides for two different acceptance criteria schemes. The more strin- gent criteria are recommended for use on IPC Class 2 and Class 3 assemblies and the less stringent criteria are recommended for use on IPC Class 1 assemblies. It should be noted that no IPC specification refers to this test, and the Figure 2: Localized extraction and cleanliness testing steam head. [2]

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