CIS Rework, Repair & Modification Flashcards

What technique is used to remove excess solder from a through-hole barrel during rework without damaging the barrel plating?

Answer: Vacuum desoldering tool (solder sucker) or desoldering wick applied with a properly temperature-controlled iron

Vacuum desoldering tools or desoldering wick combined with a temperature-controlled iron are the standard methods for safely removing solder from through-hole barrels without damaging plating.

What is a 'conformal coating repair' and why is it required after rework?

Answer: Reapplying conformal coating to the reworked area to restore environmental and dielectric protection that was removed during rework

Conformal coating must be repaired after rework because rework requires removing the coating in the work area; restoration of the coating is required to maintain the board's environmental protection.

When replacing an SMT component during rework, what is the correct sequence of steps?

Answer: Clean pad → condition pad → apply solder paste or flux → place component → reflow → clean → inspect

The correct rework sequence is: clean residual solder from pads → condition pads → apply fresh solder paste or flux → place the new component → reflow → clean → inspect for acceptability.

IPC-7711 specifies that a repaired lifted land must restore conductivity and:

Answer: Be mechanically secured with epoxy adhesive and the conductor trace continuity restored with jumper wire if the pad was lost

IPC-7711 specifies that a lifted land repair requires mechanical stabilization with adhesive and trace conductivity restoration using a jumper wire where the conductor has been interrupted.

What is 'balling' of solder paste, and what rework issue does it indicate?

Answer: Solder paste that has formed spheres instead of reflowing into a joint, indicating insufficient heat or paste contamination during reflow

Solder paste balling occurs when the paste solvents and flux cannot adequately activate, causing the solder powder to coalesce into separate balls rather than forming a unified joint, indicating inadequate heat or contaminated paste.

According to IPC-7711/7721, what is the acceptability limit for the number of rework cycles on a printed circuit board conductor repair?

Answer: Determined by engineering disposition — no fixed IPC limit but must be documented

IPC-7711/7721 does not specify a universal limit on conductor repairs but requires engineering disposition and documentation for repairs, particularly multiple repairs in the same area on Class 2 and 3 boards.