Packaging and assembly
In reflow, what is the defect called in which one end of a small part such as a chip resistor lifts up so the part stands on end?
- ATombstoning (the Manhattan effect)
- BStiction
- CLatch-up
Show answer and explanation
Answer: A. Tombstoning (the Manhattan effect)
If the solder at the two ends of a part melts at different times, or the solder amount or temperature differs, surface tension from the side that melts first pulls the part so the other end lifts and it stands up like a tombstone. This is called tombstoning and is prevented through pad design and uniform heating.
- A. Correct. One end of the part lifts so it stands up.
- B. Stiction is MEMS movable parts sticking.
- C. Latch-up is a high current caused by a CMOS parasitic thyristor.