Wave Soldering Thermal Profile Calibration after Extended Factory Shutdowns
Calibrating wave solder thermal profiles after extended shutdowns prevents barrel fill defects, dross contamination, and micro-ball bridging.
Touch up Rework
Meaning
The manual correction of localized defects on printed circuit boards or mechanical parts involves localized soldering or refinishing to meet quality standards. This touch up rework is performed by trained operators who repair solder bridges, missing solder, or surface scratches without subjecting the entire assembly to another thermal cycle. It is used to salvage components that would otherwise be rejected and scrapped.
Technical Procedure
Operators use specialized soldering irons with fine tips and auxiliary flux to correct defective solder joints. During touch up rework, the temperature of the soldering iron must be controlled to prevent thermal shock to the surrounding components or delamination of the board. The operator carefully melts the defective solder, adds a small amount of fresh alloy, and removes any excess material using a desoldering wick.
This action must be completed quickly to avoid burning the board.
Quality Control
Post-rework inspection under magnification is required to verify that the repair has been executed successfully and does not introduce new defects. Once touch up rework has been performed, the joint must be cleaned with an appropriate solvent to remove any corrosive flux residue. Visual standards, such as IPC-A-610, are used to evaluate the reworked joint to ensure it meets acceptable criteria.
This step prevents field failures caused by poor manual soldering.
Process Limitation
Excessive heat application will cause irreversible damage to the copper pads and board substrate. If an operator attempts to rework the same joint multiple times, the copper pad may lift away from the laminate, rendering the board unusable.