CIS CIS Acceptability Criteria & Defect Recognition 2

Question 1

What is 'tombstoning' in the context of SMT assembly?

Accepted Answer

A defect where one end of a chip component lifts off its pad during reflow

Answer

Tombstoning (also called drawbridging) occurs when one end of a small chip component lifts during reflow due to unequal surface tension forces on the solder.

Question 2

According to IPC-A-610, component skew for chip resistors and capacitors is acceptable for Class 2 when:

Accepted Answer

Both terminations remain on their respective pads within specified limits

Answer

For Class 2, component skew is acceptable as long as both terminations remain on their pads within the allowable placement offset limits specified for the component type.

Question 3

What defect is described as solder that forms a sharp peak or spike projecting from a solder joint?

Accepted Answer

Solder icicle (solder spike)

Answer

A solder icicle or solder spike is a sharp protrusion of solder projecting from the joint, which can cause shorts if it contacts adjacent conductors.

Question 4

For IPC-A-610, what is the acceptability status of a solder ball that is NOT entrapped under a component and can be removed without damaging the assembly?

Accepted Answer

Process indicator for Class 1, defect for Class 2 and 3

Answer

Solder balls not trapped under components are a process indicator for Class 1 and a defect for Class 2 and Class 3 assemblies per IPC-A-610.

Question 5

'Dewetting' in soldering refers to:

Accepted Answer

Solder that wetted a surface but then partially pulled back, leaving an uneven, irregular surface

Answer

Dewetting occurs when solder initially wets a surface but then contracts or pulls back, leaving irregular solder masses separated by areas where the base metal is exposed.

(CIS) Certified IPC Specialist Practice Test

(CIS) Certified IPC Specialist Practice Test

CIS CIS Acceptability Criteria & Defect Recognition 2