Printed Wiring Assemblies (PWAs)
Improper modification of a solder lug causing short

This solder lug did not have a flatness requirement specified on the assembly documentation. The printed wiring assembly was part of a module with another printed wiring assembly mounted facing it. Because it was bent upward (in order to have better access during the soldering operation), this solder lug was in contact with a transistor on the facing board. Eventually vibration caused the solder lug to rub through the conformal coating on the adjacent transistor and result in a short circuit and module failure

Reference :
NASA-STD-8739.3 Attachment of conductors to terminals. 9.1 General   12. Terminals. Terminals shall be of proper size to accommodate the conductors. Terminals and conductors shall not be modified except for high voltage applications.