ESD and CMOS handling practice Which of the following is NOT a recommended precaution when handling CMOS devices?
-
ADevices should be placed pins-down on a grounded conductive surface such as a metal plate.
-
BEarth-ground tools, test equipment, and metal benches.
-
CDo not insert CMOS into sockets or PCBs with power applied.
-
DWear wool clothing at all times.
Answer
Correct Answer: Wear wool clothing at all times.
Explanation
Introduction / Context:CMOS inputs are susceptible to electrostatic discharge. Proper ESD practice prevents latent or immediate device damage. Some habits reduce charge buildup; others make it worse.
Given Data / Assumptions:
- ESD can destroy gate oxides via high voltage spikes.
- Grounding and power-off insertion are standard precautions.
- Certain materials (e.g., wool) promote charge generation.
Concept / Approach:Best practice includes working on grounded surfaces, using wrist straps, keeping humidity reasonable, and never hot-plugging unprotected CMOS. Insulative clothing and carpets increase ESD risk and are discouraged.
Step-by-Step Solution:Identify clearly bad advice: wearing wool promotes static.Other listed items match standard ESD guidelines (ground everything, power off before insertion).
Verification / Alternative check:ESD control manuals recommend conductive mats, wrist straps, and avoiding static-generating materials like wool or some synthetics.
Why Other Options Are Wrong:Grounding surfaces and tools reduces ESD risk.Pins-down on grounded surface equalizes potential.Inserting with power off avoids latch-up and transients.
Common Pitfalls:Forgetting that humidity affects ESD, and neglecting personal grounding measures when moving around the lab.
Final Answer:Wear wool clothing at all times.