CIT Rework, Modification, and Repair of Electronic Assemblies 2

Question 1

When reworking a BGA component, what is the primary purpose of the soak phase in the reflow profile?

Accepted Answer

To activate flux and equilibrate board temperature before reflow

Answer

The soak phase allows flux to activate and the entire assembly to reach thermal equilibrium, reducing thermal shock before the reflow peak.

Question 2

According to IPC-7711/7721, which condition requires a Class 3 assembly to be scrapped rather than repaired?

Accepted Answer

Conductor damage exceeding allowable width reduction limits after repair

Answer

IPC-7711/7721 defines allowable repair limits; conductor damage that still exceeds width reduction limits after repair renders the assembly non-conforming for Class 3.

Question 3

What is the correct method to remove a through-hole component with multiple leads from a double-sided PCB without damaging plated-through holes?

Accepted Answer

Use a solder extractor on each lead sequentially while heating

Answer

Sequential heating and solder extraction on each lead prevents the thermal stress that could damage PTHs, ensuring barrel integrity.

Question 4

When conformally coating a reworked area, what must be done if the original coating was a silicone type?

Accepted Answer

Remove all silicone residue before applying any new coating

Answer

Silicone residue prevents adhesion of most other coating types and must be fully removed before recoating to ensure conformal coating integrity.

Question 5

A technician notices a solder bridge between two fine-pitch QFP leads after rework. What is the IPC-recommended first corrective action?

Accepted Answer

Use a flux-wetted solder wick to remove the bridge

Answer

A flux-wetted solder wick is the IPC-recommended method for removing solder bridges on fine-pitch leads without damaging the pads.

(CIT) Certified IPC Trainer Practice Test

(CIT) Certified IPC Trainer Practice Test

CIT Rework, Modification, and Repair of Electronic Assemblies 2