CIS Soldering Techniques & Standards 3

Question 1

What soldering defect is characterized by solder that bridges two adjacent pads or leads that should not be connected?

Accepted Answer

Solder bridge (short)

Answer

A solder bridge is an unintended solder connection between two conductors that should be electrically isolated, creating a short circuit.

Question 2

Tombstoning of an 0402 chip resistor during reflow is most commonly caused by:

Accepted Answer

Uneven heating causing one pad to wet before the other

Answer

Tombstoning occurs when one pad melts and wets before the other, creating an unbalanced surface tension force that lifts one end of the component.

Question 3

A 'cold solder joint' is primarily identified by which visual characteristic per IPC-A-610?

Accepted Answer

Dull, grainy, or rough surface texture with poor wetting

Answer

Cold solder joints exhibit a dull, grainy, or crystalline surface caused by insufficient heat or movement during solidification, indicating poor wetting.

Question 4

What is 'solder balling' and what is its primary cause in SMT reflow processes?

Accepted Answer

Small solder spheres adjacent to joints, caused by solder paste spattering from moisture or rapid outgassing

Answer

Solder balling creates tiny solder spheres near joints when flux solvents or moisture cause explosive outgassing during the preheat phase, scattering solder particles.

Question 5

Per IPC-A-610 Class 2, what is the maximum allowable amount of lifted land (pad lifting) on a surface mount component?

Accepted Answer

Any lifted land that reduces electrical performance is a defect; minor lifting without separation may be a process indicator

Answer

IPC-A-610 classifies lifted lands based on whether the electrical function is compromised; any lift that separates the conductor is a defect across all classes.

(CIS) Certified IPC Specialist Practice Test

(CIS) Certified IPC Specialist Practice Test

CIS Soldering Techniques & Standards 3