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
Which IPC document is the primary reference standard for rework, repair, and modification procedures on printed board assemblies?
Answer: IPC-7711/7721
IPC-7711/7721 is the industry-standard reference specifically covering rework, modification, and repair of electronic assemblies.
When using a hot-air pencil to remove an SOT-23 component, why should the nozzle diameter be matched closely to the component size?
Answer: To concentrate heat on the target component and minimize thermal damage to adjacent parts
A matched nozzle concentrates heat on the target SOT-23, reducing heat spread to neighboring components and preventing collateral damage.
What is the purpose of applying a dam (epoxy barrier) around a repair site before filling a hole or void?
Answer: To contain the repair material and define the repair boundary
The dam confines the repair fill material (epoxy or solder) within the repair zone, preventing it from spreading to adjacent areas.
A Class 3 PCB has a conductor that was accidentally cut during rework. The conductor width is 0.5 mm. What is the minimum width the repair conductor (jumper) must maintain per IPC-7711/7721?
Answer: Equal to or greater than the original conductor width
IPC-7711/7721 requires repair conductors to equal or exceed the original conductor width to maintain the original current-carrying capacity.
During rework of a lead-free assembly using tin-lead solder, what is the most critical concern?
Answer: Mixing tin-lead and lead-free alloys can create solder joints with unpredictable melting points and reliability
Mixing tin-lead and lead-free solder creates alloy combinations with variable melting points, potentially compromising joint reliability and certification compliance.
When repairing a solder mask void over a conductor, which material is typically used per IPC-7711/7721?
Answer: UV-curable liquid solder mask or solder mask repair ink
IPC-7711/7721 specifies UV-curable liquid solder mask or dedicated solder mask repair ink for restoring solder mask voids over conductors.
ESD precautions during rework require that the technician verify the wrist strap is functional by testing it at a minimum of:
Answer: At the beginning of each shift or work session
ESD control standards require wrist strap verification at the start of each shift to ensure the ground path is intact before handling ESD-sensitive assemblies.