Evaluation of ENEPIG substrate for handheld product application

Electroless nickel (Ni) electroless palladium (Pd) immersion gold (Au) (ENEPIG) substrate metal finish was evaluated for suitability for handheld product. 3 main focus areas were covered in the evaluation: plating thickness measurement system, processibility and reliability. The plating thickness measurement system was established with physical analysis and mirco X-ray fluorescence. The processibility studies included Au-wire bondability on ENEPIG bond finger and lead free (Pb-free) solder paste printing on solder pad. The result showed feasibility of manufacturing electronic packages using ENEPIG substrate could be obtained with certain level of process parameters optimization. Package level reliability showed ENEPIG substrate had comparable reliability performance compared to Electrolytic NiAu / CuOSP substrate. For board level reliability, the temperature cycling on board (TCoB) and bend test (BT) showed ENEPIG substrate performed similarly but drop test (DT) showed earlier first drop to failures. The low package standoff offered acceptable number in first drop to failure despite of the application of ENEPIG substrate. Difference in substrate outer Cu layer thickness was discussed as a factor influencing drop test performance. Failure analysis (FA) found different drop testing failure modes over the ENEPIG substrate samples and CuOSP substrate samples.