CIT Cable and Wire Harness Assembly Requirements 2 — Questions and Answers
Question 1: According to IPC/WHMA-A-620, what is the minimum bend radius for a coaxial cable in a fixed application?
- 3 times the cable outer diameter
- 6 times the cable outer diameter (Correct answer)
- 10 times the cable outer diameter
- 1 times the cable outer diameter
Correct answer: 6 times the cable outer diameter
IPC/WHMA-A-620 specifies a minimum bend radius of 6 times the outer diameter for coaxial cables in fixed applications to prevent signal degradation.
Question 2: When installing a wire tie (cable tie) on a harness, which condition constitutes a Class 3 defect?
- Tie tail extending more than 6 mm after trimming
- Tie installed at a conductor splice location (Correct answer)
- Tie body visible from the exterior
- Tie color does not match harness color
Correct answer: Tie installed at a conductor splice location
Installing a wire tie directly over a conductor splice is a defect in all classes because it can damage insulation and create stress on the connection.
Question 3: What does the term 'breakout' refer to in cable and wire harness assemblies?
- A point where wires exit the main harness trunk to a branch (Correct answer)
- The insulation stripping at wire termination ends
- The failure of a conductor under tensile load
- A separation between jacket layers in a multi-conductor cable
Correct answer: A point where wires exit the main harness trunk to a branch
A breakout is the point in a wire harness where individual wires or groups of wires branch off from the main bundle.
Question 4: Which IPC/WHMA-A-620 class requires the most stringent workmanship standards for harness assemblies?
- Class 1
- Class 2
- Class 3 (Correct answer)
- Class 4
Correct answer: Class 3
Class 3 represents High Performance/Reliability electronics where continued performance is critical, such as life-support or military applications.
Question 5: When using heat-shrink tubing on a wire harness, what is the correct sequence of operations?
- Shrink tubing, then terminate the connector
- Slide tubing on, terminate, then apply heat to shrink (Correct answer)
- Terminate, splice, then slide pre-cut tubing over the splice
- Apply adhesive, then slide tubing on before termination
Correct answer: Slide tubing on, terminate, then apply heat to shrink
Heat-shrink tubing must be slid onto the wire before termination because it cannot pass over a terminated connector, then heat is applied after termination.
Question 6: In IPC/WHMA-A-620 terminology, what is a 'lacing cord' used for?
- Securing the outer jacket of multi-conductor cable
- Bundling wire harness conductors together using a weaving pattern (Correct answer)
- Providing strain relief at connector backshells
- Joining two harness branches at a breakout point
Correct answer: Bundling wire harness conductors together using a weaving pattern
Lacing cord is a flat or round waxed string woven or tied around wire bundles to maintain their shape and organization.
Question 7: What is the purpose of a 'rat's nest' inspection step during harness assembly?
- To verify that all wire colors match the schematic
- To check that conductors are not tangled or crossed before final bundling (Correct answer)
- To measure the harness against a dimensional drawing
- To confirm that all splices are properly insulated
Correct answer: To check that conductors are not tangled or crossed before final bundling
A rat's nest inspection checks that individual conductors are routed correctly and not unintentionally crossed or tangled before the bundle is secured.
CIT Cable and Wire Harness Assembly Requirements 2
According to IPC/WHMA-A-620, what is the minimum bend radius for a coaxial cable in a fixed application?