Separate ENIG Thickness Results from Nickel Corrosion Evidence

An ENIG thickness report can be satisfactory while a separate question about the condition of the nickel deposit remains open. Thickness and corrosion assessment describe different attributes. A useful investigation identifies the disputed attribute first and then requests evidence capable of resolving it.

Assign each report a specific purpose

Uyemura’s discussion of IPC-4552 revision A describes a corrosion inspection and rating approach in addition to deposit-thickness requirements. The page concerns that historical revision; use the revision required by the actual purchase specification for acceptance. Its useful distinction is that corrosion evaluation requires evidence beyond a thickness number.

Ask whether the concern is deposit thickness, surface appearance, local nickel condition or solder-joint performance. Keep separate columns for those questions in the investigation record. An XRF result should be identified by measurement location and purpose rather than treated as a general certificate that every finish attribute is acceptable.

Request traceable inspection evidence

For corrosion assessment, obtain the method, sample selection, preparation, images, classification and applicable disposition criteria. Require enough location information to connect each image to a board, pad and lot. A cropped micrograph without scale or preparation context is difficult to compare and may encourage overconfident interpretation.

Do not assign a corrosion level yourself from a low-resolution screenshot. Have the qualified laboratory explain how the observation was classified under the agreed method. Ask which features were examined and whether the selected sample represents the suspect population or only an isolated site.

Preserve the difference between cause and consequence

If the trigger was a fractured joint, preserve the fracture surfaces and assembly history before destructive preparation. The finish investigation and the joint-failure investigation should exchange evidence, but neither should assume the other’s conclusion. Record where the separation occurred and what analysis supports that interpretation.

A board with an unusual pad appearance may justify additional review, but appearance alone does not establish the failure mechanism. Conversely, a visually uniform finish does not close every subsurface question. Use affected and unaffected controls where available, with clearly stated selection logic.

Make disposition specific to the evidence

The disposition should identify the lot, sampled locations, contractual criteria and any additional verification required. Avoid importing numerical limits from an older online article into a purchase governed by another revision. If the specification is unclear, resolve that ambiguity before accepting or rejecting the population.

Retain thickness data alongside corrosion findings and assembly observations so that the combined record remains coherent. The result should explain which requirement passed, which concern was investigated and why the chosen disposition follows. That is more defensible than either accepting every board on thickness alone or rejecting a lot from one unclassified image.