A charger factory that says “we test everything” is describing one of three gates. The three gates do different jobs, and a programme that only has one of them is the programme that discovers problems at the port.
Incoming inspection (IQC)
Components are checked against the approved bill of materials before they reach the line: power devices, capacitors, the transformer, the plug parts, the cable. The important part is not that the part arrives, it is that the part is the approved one — same manufacturer, same rating, same tolerance band. A substitute capacitor with the same capacitance but a lower ripple rating will pass a bench test and fail at hour two of a sustained load. IQC is where that variable is removed.
In-process inspection (IPQC)
The line is watched while it runs. At the SMT stage that means solder joint quality, placement accuracy and reflow profile; at final assembly it means screw torque, cable routing and the fit of the plug mechanism. These are checks on the process rather than on the product, which is why they catch systematic faults that a finished-unit test would only see as a percentage failure.
Outgoing inspection (OQC)
Every finished unit is function tested, and a sample is measured in detail: output voltage and current across the load range, ripple under load, temperature rise after a sustained run, and plug or pad retention. Because the destructive and ageing tests consume units, they run on a sample per batch rather than on everything — the sampling plan, not the test method, is what makes a claim defensible.
Which measurement catches problems first
In practice it is temperature rise. A drifting component, a marginal solder joint and an oversized load all show up as heat before they show up as a failed measurement. That is why the ageing rack exists: units run under load for hours and are re-measured afterwards, and the numbers are filed against the batch date code.
What a buyer should ask for
Not “do you inspect?” but “what is sampled, at what AQL, and what happens to a failed batch?” A useful answer names the three gates, the sampling plan, and the fact that the outgoing gate has the authority to stop a shipment. If a factory cannot stop a line, the inspection is a formality.