- Effect "What does it look like?"
- May appear as:
- Electrical open, intermittent open and/or
gross functional failure
- May be detected as missing section of the
wire in x-ray or optical inspection. Occasionally:
- seen as a melted ball at each termination of the break
- associated with carbonized epoxy 'sheath' or shell
- Causes (What caused the damage?)
- Sustained high current or power dissipation
- Typically greater than 1 amp
- Sources (What generated the voltage spike)
- Humans
- Mis-insertion of IC / device
- Wrong test program
- Machine
- System test over-current event
- Check over-current limiters on system testers
- Unregulated power supplies
- Check for unregulated or faulty power supplies
- Environment
- Lightning strike, power supply surge/transient
- Device and application exposure to lightning and/or
power supply transients during test or assembly
- Latch-up condition
- Application and test procedures against latch-up conditions
- Methods for Investigation
- Look first at
- Quantify scope/size of problem
- Is it a sporadic occurrence?
- Does it happen on a recurring basis?
- Does it appear to be "batch" related?
- Most likely problem areas
- Is there adequate ESD training?
- Are ESD control components maintained?
- Are there unwanted voltage spikes in Electrical Test?
- Are machines properly grounded?
- Did any of the following occur?
- Non-standard process handling (ie. re-work, off-line
sampling); Process or material changes prior to recent events (ie.
ESD component or raw material changes; Power distribution to plant or
assembly line)
- Didn't find anything. Now What?
- ESD survey
- ESD audit using spec: EIA 625
- Humidity survey (>40%RH)
- Grounding (human and machine)
- Packing materials
- Remove non-essential ESD-generating material
- ESD or static field sources
- Check application for inductors in proximity
- Supply line monitors
- Found something. Now what?
- Address any findings resulting from ESD survey or process review
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