Rework, Modification, and Repair of Electronic Assemblies Flashcards
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Read the first 7 Rework, Modification, and Repair of Electronic Assemblies flashcards as text
When reworking a BGA component, what is the primary purpose of the soak phase in the reflow profile?
Answer: To activate flux and equilibrate board temperature before reflow
The soak phase allows flux to activate and the entire assembly to reach thermal equilibrium, reducing thermal shock before the reflow peak.
According to IPC-7711/7721, which condition requires a Class 3 assembly to be scrapped rather than repaired?
Answer: Conductor damage exceeding allowable width reduction limits after repair
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.
What is the correct method to remove a through-hole component with multiple leads from a double-sided PCB without damaging plated-through holes?
Answer: Use a solder extractor on each lead sequentially while heating
Sequential heating and solder extraction on each lead prevents the thermal stress that could damage PTHs, ensuring barrel integrity.
When conformally coating a reworked area, what must be done if the original coating was a silicone type?
Answer: Remove all silicone residue before applying any new coating
Silicone residue prevents adhesion of most other coating types and must be fully removed before recoating to ensure conformal coating integrity.
A technician notices a solder bridge between two fine-pitch QFP leads after rework. What is the IPC-recommended first corrective action?
Answer: Use a flux-wetted solder wick to remove the bridge
A flux-wetted solder wick is the IPC-recommended method for removing solder bridges on fine-pitch leads without damaging the pads.
Under IPC-7711/7721, what is the maximum number of times a plated-through hole may be re-soldered before it is considered potentially compromised?
Answer: Three times
IPC-7711/7721 guidance generally limits PTH re-soldering to three cycles before barrel integrity may be compromised.
When performing a modification to add a jumper wire on a Class 3 assembly, which wire type is preferred per IPC-7711/7721?
Answer: Insulated, stranded copper wire
IPC-7711/7721 requires insulated, stranded copper wire for jumper modifications on Class 3 assemblies to ensure flexibility and prevent shorts.