CIS Electronic Assembly & Manufacturing Processes 5

Question 1

What is the primary difference between Class 1 and Class 2 electronic assemblies per IPC-A-610?

Accepted Answer

Class 1 is general electronics with limited life expectancy; Class 2 requires extended reliable service

Answer

Class 1 covers general electronics where cosmetic imperfections are acceptable, while Class 2 requires extended service life and reliable performance in typical environments.

Question 2

What causes 'cold solder joints' during hand soldering?

Accepted Answer

Insufficient heat or movement during solidification

Answer

Cold solder joints result from inadequate heat transfer or disturbing the joint before it fully solidifies, producing a grainy, dull appearance and weak bond.

Question 3

In SMT stencil printing, what is the 'area ratio' rule used to determine?

Accepted Answer

Whether an aperture will release solder paste cleanly from the stencil

Answer

The area ratio (aperture opening area divided by aperture wall area) predicts paste release; a ratio above 0.66 generally ensures clean release.

Question 4

What is the function of the 'dross skimmer' in a wave solder machine?

Accepted Answer

Remove oxidized solder from the surface of the solder bath

Answer

The dross skimmer removes the layer of oxidized solder (dross) that forms on the molten solder bath surface to maintain solder quality.

Question 5

Which IPC document provides design requirements for printed boards (PCB fabrication)?

Accepted Answer

IPC-2221

Answer

IPC-2221 is the Generic Standard on Printed Board Design, defining requirements for PCB design including materials, electrical, thermal, and mechanical criteria.

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CIS Electronic Assembly & Manufacturing Processes 5