OQA Rejects: ESD or EOS?

Guest

How can you tell if a test reject at OQA is due to EOS or ESD?

Secret

Joined: 20 Jun 2026 Posts: 76

Secret,

What do you mean by "How can you tell if a test reject at OQA is due to EOS or ESD?"? ESD is a form of EOS. Maybe what you mean is how can you tell if the failure is due to ESD or ATE-induced EOS? FA is needed.

If there's gross metal burn-out, then it's EOS. If the signs are less subtle, then you need to understand the attributes.

If there are no visual anomalies, then it would be hard to determine if failure is due to ESD or EOS. ESD is more likely if: 1) dielectric/gate oxide ruptures are observed at steps or edges of lines connected to an external pin; 2) there's a point emission or hot spot at the rupture site; 3) the device is ESD-sensitive; and 4) ATE simulations can't duplicate the problem. ESD and ATE simulations should be done to prove or disprove one or the other.

FARel Engr

Joined: 20 Jun 2026 Posts: 20

Secret,

ESD can occur anywhere and in random, so this is very hard to catch. All you can do is check for 'weaknesses' in the ESD controls in the line where the OQA failure occurred. If there are no weaknesses and field meter readings are below 100V at all times everywhere, then maybe ATE is the culprit.

If you suspect your ATE to be causing the failure, then what you can do is to get 200 units from a good lot and to retest these units over and over in the ATE. If you get failures after several test cycles, then your hunch may be correct. You then need to review every test block in the test program for sources of EOS conditions. Maybe you also need to monitor your supplies/inputs for spikes with an oscilloscope.

Some ATE-induced EOS are very subtle that they really look like ESD. So better be careful.

Test Engg 99