The part in question is a 2 x 2 mm LGA accelerometer.
1. First soldering scenario, 10% non working parts after the assembly:
- no ESD protection gear
- hot air gun smoothly brought near / away from above the part; low temperature & low air flow setting
- care has been exercised in handling the parts
2. Second soldering scenario, 36% non working parts after the assembly:
- wrist strap protection gear grounded to mains GND, nothing else
- hot air gun not-so-smoothly brought near / away from below the part (from the other side of the PCB); high temperature & high air flow setting
- care has not been exercised in handling the parts
I know ESD can damage such minute parts although I am not sure to what extent. 36% seems a bit high. Should I attribute this high rebuttal rate to the heating process ? Perhaps to something else ?
Responding to the comments
Care from the above paragraphs refers to directly touching the metal pins of the part or not. Probably not releveant ESD wise though. I should have been more clear on that, sorry.
As for the rest, I do not have a proper lab here, I am just hand assembling these PCBs at home. And the worst thing about this is that I do not have any temperature control. This is no bad soldering as re-soldering yields the same results. The rest of the circuit works OK once the faulty parts are removed. They have been kept in that special humidity absorbing bag they were shipped in.