Page 139 - CITS - Electronic Mechanic - TT - 2024

ELECTRONICS MECHANIC - CITS

6 High-Potential (Hipot) Test:
Purpose: To verify the dielectric strength of the PCB by subjecting it to high voltage.
Method: Apply a high voltage between conductors and substrate and measure leakage current or insulation
breakdown.
7 Microsection Analysis:
Purpose: To inspect internal structures and solder joints for defects such as voids, cracks, or delamination.
Method: Cut and polish a cross-section of the PCB and examine it under a microscope.
8 Environmental Testing:

Purpose: To evaluate the PCB’s performance under different environmental conditions such as temperature,
humidity, and vibration.
Method: Subject the PCB to environmental chambers or vibration tables according to relevant standards (e.g.,
MIL-STD-810).
Introduction to Rework and Repair Concepts
Rework:

Rework refers to the process of correcting defects or errors identified during the manufacturing or assembly of
electronic components or PCBs before they are completed.
Repair:

Repair involves fixing defects or failures discovered in finished electronic products or assemblies after they have
been manufactured and tested.
Common Reasons for Rework and Repair:

Soldering Defects
Examples include solder bridges, insufficient solder joints, cold solder joints, and solder balls.
Component Placement Errors
Incorrect component orientation, misalignment, or missing components.

Electrical and Functional Failures
Circuitry faults, shorts, open circuits, or failures identified during testing or operation.
Physical Damage:
Damage due to mishandling, mechanical stress, or environmental factors such as moisture, heat, or vibration.
Rework and Repair Processes:

Identification and Assessment:
The first step involves identifying the defect or failure and assessing its impact on the functionality and performance
of the electronic product or assembly.

Disassembly:
If necessary, the electronic assembly or PCB is disassembled to access the defective or damaged components.
Component Removal:

Defective components are removed using desoldering tools and techniques such as hot air rework stations,
soldering irons, or solder wick.
Cleaning and Preparation:

The area around the removed component is cleaned to remove residual solder and flux. PCB pads may be
prepped for re-soldering.

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CITS : E & H - Electronics Mechanic - Lesson 73 - 76