Often when engineers and product developers think about a transition to lead-free products their focus is primarily on assembly optimization and product testing to ensure reliability. These are indeed critical aspects of a successful transition, however, there are other areas that are equally important. These include material selection, component specification/qualification, rework, failure analysis and remediation actions when failure occurs during assembly or testing.
Electrochemical migration (ECM) is defined as the growth of conductive metal filaments across a printed circuit board (PCB) in the presence of an electrolytic solution and a DC voltage bias . ECM, also known as dendritic growth, is a critical issue in the electronics industry because the intermittent failure behavior of ECM is a likely root-cause of the high occurrence of field failures identified as no trouble found (NTF)/could not duplicate (CND)[2,3].
In the electronics industry, the quality and reliability of any product is highly dependent upon the capabilities of the manufacturing suppliers. Manufacturing defects are one of the top reasons why companies fail to meet warranty expectations. These problems can result in severe financial pain and eventual loss of market share. What a surprising number of engineers and managers fail to realize is that focusing on processes addresses only part of the issue. Supplier selection also plays a critical role in the success or failure of the final product.
DO leave adequate space on your PCB for EMI suppression devices. With good EMI design practices, your circuit board may be very quiet. But to be on the safe side, leave extra space on the board for the addition of filters and chokes. It is also a good idea to add extra pads to the board in case a shunt capacitor is needed here or there.
DO NOT assume that "second sourced" parts will have the same spectral characteristics as the original. This is especially important for active components such as DC-DC converters. The fit, form, and function may be the same, but the EMI noise could be significant. Before investing in a large stock of these extra parts, plug one into your design and take it for a test drive.