Pad Lifting
Copper pad separation during rework
What it is
Pad lifting occurs when a copper pad on a PCB separates from the substrate laminate during component rework, typically reballing or reflowing. The pad remains attached to the component or solder ball, while its connection to the underlying trace is severed. This exposes the internal PCB layers and creates an open or intermittent circuit at that connection point.
Lifting is mechanically distinct from cold solder joints, which involve poor wetting or incomplete metallurgical bonding. Pad lifting is a physical delamination event—the pad itself pulls away from the FR-4 or ceramic substrate. Common causes include excessive heat dwell time, aggressive thermal cycling, inadequate thermal mass management, or pulling at angles rather than vertically during component removal.
The severity ranges from partial lifting (pad edges still bonded) to complete separation (pad floats freely in solder or against the ball contact). Partial lifts may exhibit intermittent connectivity; complete lifts result in hard opens unless bridged by solder.
In practice
You encounter pad lifting most often during Pad Lifting — PCB pad damage and recovery operations on high-pin-count BGAs, particularly on boards with thin copper, weak pad adhesion, or insufficient solder mask coverage over the pad edges. After reflowing a reballed chip, the board tests intermittently or shows hard opens on specific balls.
Diagnostic workflow: Probe the pad with a multimeter in resistance mode. A normal pad-to-trace connection reads 0.1–0.5 Ω. A lifted pad often reads ∞ (open) or exhibits erratic continuity that changes with probe pressure. X-ray inspection reveals the pad has separated; optical inspection shows the pad may still be glossy and clean (not obviously defective) but visibly pulled away from the board surface.
During removal, if you observe the pad tearing away with the solder ball or hear a distinct crack as the component lifts, pad lifting has occurred. Prevention requires careful speed control during hot-air removal, even thermal application across the component, and vertical (not sideways) extraction. Use flux adequately to promote wetting and reduce thermal shock.
Once lifted, the pad cannot be simply resoldered. The via or trace underneath may still be intact, but the lifted pad provides no contact surface. Repair requires either Pad Lifting — PCB pad damage and recovery and reballing with a new pad (rework shop capability), or micro-soldering a bridging wire to the exposed trace—a Level 3+ technique unsuitable for production rework.
| Measurement / Condition | Expected (Normal) | Pad Lifting Indicator |
|---|---|---|
| Pad-to-trace resistance (contact) | 0.1–0.5 Ω | ∞ Ω (open) or intermittent |
| Solder joint appearance (X-ray) | Ball centered, pad flat against board | Ball connected; pad gap visible beneath |
| Optical inspection (rework) | Pad remains on board after ball removal | Pad lifts with ball; substrate visible |
| Reflow time at peak (260–280°C) | 10–30 seconds | >45 seconds increases risk |
| Extraction force direction | Vertical pull only | Sideways or angled pull triggers lift |
Prevention & control
Thermal profile: Reduce dwell time at peak temperature. Aim for 15–20 seconds, never exceed 35 seconds. Use accurate thermocouples to verify actual pad temperature, not just air temperature.
Heating method: Distribute heat evenly using larger stencils or spreading thermal mass under the component. Avoid point-source heat (naked iron, narrow hot-air nozzle).
Extraction: Use vertical lift tools, never hand tools. Commercial reballing equipment applies upward force perpendicular to the board plane. Hand-extract only if absolutely necessary—use a specialized extraction frame and apply slow, steady upward pressure.
Flux choice: Higher-activity flux reduces thermal shock and promotes wetting, easing mechanical stress during reflow.
Board condition: Inspect the board for traces of prior pad lifting damage, cracked solder masks, or weak ground planes. Some boards are inherently prone to lifting.