Quality Control & Inspection Procedures Flashcards

A batch of assembled boards returns from field with intermittent failures. Failure analysis reveals dendritic growth between conductors. Which root cause is most probable?

Answer: Ionic contamination remaining on boards after inadequate cleaning

Dendritic growth (electrochemical migration) is caused by ionic contamination in the presence of moisture and electrical bias, indicating inadequate flux residue removal.

During visual inspection, an inspector identifies a 'skewed' SMD component. Under IPC-A-610, the maximum allowable rotation for a chip capacitor to still be classified as acceptable for Class 2 is governed by:

Answer: The end cap must maintain minimum overlap with the land pad as defined in IPC-A-610 tables

IPC-A-610 defines acceptability for rotated chip components based on whether minimum land overlap and solder joint geometry requirements are still met, not a fixed angle.

What is the recommended practice when an inspector disagrees with an AOI rejection on a production line to avoid introducing subjectivity?

Answer: Dispositions should follow a defined accept/reject criteria reviewed by a second inspector or engineer

Best practice requires that AOI rejects be dispositioned against written acceptance criteria, with a second review by a qualified inspector or engineer to minimize subjectivity.

Which of the following best describes the function of a 'non-conformance report' (NCR) in a quality system?

Answer: A formal record documenting that a product or process does not meet specified requirements

An NCR formally documents any departure from specified requirements, initiating corrective action tracking and providing traceability within the quality management system.

When performing microsection analysis of a through-hole solder joint, which microstructural feature indicates that excessive heat was applied during soldering?

Answer: A thick, coarse intermetallic layer exceeding several micrometers

An excessively thick or coarse intermetallic compound (IMC) layer at the copper-solder interface indicates prolonged or excessive heat exposure, which embrittles the joint.

A CIS inspector is reviewing a workmanship standard for connector pin insertion. The pin is 0.1 mm short of minimum protrusion on the secondary side. What action is required for a Class 3 assembly?

Answer: Reject or rework the assembly — minimum protrusion is mandatory for Class 3

For Class 3, insufficient lead protrusion is a defect because adequate protrusion is required to form a reliable solder joint; the assembly must be reworked or dispositioned via formal deviation.

Which inspection method is best suited for detecting internal delamination within a multilayer PCB without destroying the board?

Answer: Scanning Acoustic Microscopy (SAM)

Scanning Acoustic Microscopy (SAM) uses ultrasound to detect internal delaminations, voids, and disbonds within multilayer PCBs non-destructively.