A common example of cases where the solder barrier was insufficient is seen in the graping defect, or its relative, the head-in-pillow defect. If you are experiencing one of these defects, a solder paste with better oxygen barrier properties is bound to help.Click to see more on …
A final finish, which was already introduced more than ten years ago, is now receiving renewed attention because of its suitability for both Pb-free soldering and wire bonding applications, namely Electroless Nickel / Electroless Palladium / Immersion Gold (ENEPIG). Brittle fracture on BGAs is also no issue with this combination of metallic layers.
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In order to maintain the solderability of PCBs over a period of storage time, it is necessary to protect the copper surface mount pads with solderable surface finish. Up to now the most common finish is eutectic tin-lead alloy by hot air solder levelling (HASL) method because it has the most desirable properties of ideal PCB surface. Unfortunately this coating does not meet the requirement of soldering pads planarity – fundamental factor for fine – pitch, very large scale integration (VLSI) surface mount technology (SMT) and contains lead – one of the most toxic metals.