CID Research Methods & Evidence-Based Practice 3

Question 1

What is the primary purpose of including test coupons within a PCB manufacturing panel?

Accepted Answer

To serve as test specimens for process qualification without consuming production boards

Answer

Test coupons are dedicated specimens designed to the same process as production boards, allowing destructive or electrical testing without sacrificing saleable units.

Question 2

TDR (Time Domain Reflectometry) is used in PCB research primarily to measure:

Accepted Answer

Impedance profiles and signal discontinuities along transmission lines

Answer

TDR launches a fast-rise pulse and analyzes reflections to map impedance variations and discontinuities along a transmission line.

Question 3

Which IPC-TM-650 test evaluates plated through-hole reliability under repeated thermal cycling stress?

Accepted Answer

Interconnect Stress Test (IST)

Answer

IST (IPC-TM-650 2.6.26) applies controlled thermal cycling to PTH coupons and monitors resistance change to detect fatigue cracking.

Question 4

A controlled PCB via plating experiment yields a p-value of 0.03. How should this result be interpreted?

Accepted Answer

The observed difference between plating processes is statistically significant at the 5% level

Answer

A p-value of 0.03 is below the conventional 0.05 threshold, meaning the probability of the observed difference occurring by chance alone is 3%, indicating statistical significance.

Question 5

During microsection analysis of a PCB via, a 'knee crack' at the barrel-to-annular-ring junction most likely indicates:

Accepted Answer

A thermomechanical fatigue failure driven by CTE mismatch under thermal cycling

Answer

Knee cracks form at the stress concentration point where the PTH barrel meets the land due to Z-axis CTE mismatch during repeated thermal excursions.

(CID) Certified Interconnect Designer Practice Test

(CID) Certified Interconnect Designer Practice Test

CID Research Methods & Evidence-Based Practice 3