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36 SMT Magazine • April 2015 Copper Mirror The induced corrosion on copper mirror was done according to IPC-TM-650 method2.3.32. The evaluation was made according to J- STD-004 criteria: • Type L: No complete breakthrough, as evidenced by white background showing through anywhere on the test spots; this condition includes discoloration of the copper due to a superficial reaction or a reduction of the thickness of the copper film without complete breakthrough • Type M: Partial or complete copper mirror removal in less than 50% of test area • Type H: Complete copper mirror removal allowed in more than 50% of test area The results were in accordance with the ini- tial specifications of the pastes; a summary is done in the Table 8 below. Corrosion Test The corrosion test was done according to IPC-TM-650 method 2.6.15 and the results were assessed according to J-STD-004 criteria: • No corrosion: No evidence of corrosion is present • Minor corrosion: Any initial change of color, which may develop when the test panel is heated during soldering, is dis- regarded. Discreet white or colored spots in the flux residues or a color change to green-blue without pitting of the copper or formation of excrescences is regarded as minor corrosion • Major corrosion: Any initial change of color, which may develop when the test panel is heated during soldering, is dis- regarded; subsequent development of green-blue discoloration with observation of pitting of the copper panel or excres- cences at the interfaces of the flux residue and copper boundary is regarded as major corrosion. The results are summarized in the Table 8. Surface insulation resistance (Sir) Water-soluble solder pastes are designed to be cleaned after soldering: SIR values given in the datasheet of cleanable solder pastes are figure 7: Wettability on test board pattern g (enig): (l) paste a; (r) paste d. Table 7: Tomsbtoning percentage. rEliaBiliTy aSSESSMENT OF NO-ClEaN aND WaTEr-SOluBlE SOlDEr paSTES, parT ii continues FeAture