Desoldering Techniques & Tools: Wick, Pumps & Rework

Soldering is easy because gravity and capillary action pull molten solder into the joint. **Desoldering** requires working *against* surface tension and thermal mass to extract every atom of solder from a through-hole plating barrel. ### The Paradoxical Secret of Desoldering: > [!TIP] > **Add Solder to Remove Solder**: When trying to desolder an old, dry, oxidized solder joint, the iron cannot transfer heat efficiently. **Always apply a dab of fresh solder and liquid flux first!** The fresh flux cleans oxides, creates a fluid thermal bridge, and allows your vacuum pump or wick to extract the entire joint cleanly in one stroke.

A **Desoldering Pump (Solder Sucker)** uses a spring-loaded piston to create an instantaneous partial vacuum that swallows molten solder. ### Step-by-Step Vacuum Extraction: 1. Depress the plunger until it clicks locked. 2. Heat the solder joint with your soldering iron tip until the entire pool is fully liquefied (350^circC). 3. Bring the silicone nozzle of the pump right up to the joint, enclosing both the iron tip and pad to form a tight seal. 4. Press the trigger release button. The rapid vacuum pulls all molten solder into the pump chamber. 5. While the joint is cooling, gently wiggle the component lead with needle-nose pliers to confirm it is free from the hole walls.

**Desoldering Wick** consists of thousands of ultra-fine copper wire strands braided into a ribbon impregnated with rosin flux. ### The Capillary Action Method: 1. Apply a drop of liquid flux directly to the copper braid. 2. Lay the clean edge of the braid flat over the solder pad. 3. Press a wide chisel iron tip firmly onto the braid. 4. Within 2 seconds, heat will conduct through the braid, liquefying the solder underneath. Capillary tension will cause the molten solder to climb up into the copper weave like water into a sponge. 5. **Lift the iron and wick TOGETHER simultaneously**. If you remove the iron first, the wick will freeze solid to the PCB pad! 6. Snip off the solder-filled section of wick with flush cutters before the next use.

PCB copper traces are glued to the fiberglass FR4 board with epoxy adhesive. Excessive heat (>370^circC) or prolonged contact (>5 seconds) breaks down the adhesive, causing the delicate copper ring to lift off the board permanently. ### Prevention Rules: - Never exceed 4 seconds of continuous heat application per pad. If the joint doesn't clear, stop, let it cool for 30 seconds, and try again with fresh flux. - Never pry or lever components with force while the solder is semi-molten. - Use wide chisel tips for faster heat delivery instead of holding tiny needle tips on pads for 10+ seconds.