Skip to content

Trace, via & reflow repair

After a battery leak or a SMD capacitor leak, the board is often eaten: cut traces, missing vias, dissolved pads. Here is how to rebuild cleanly.

Assessing corrosion damage

  • Under SMD caps / around the battery: scrape the solder mask, inspect under the microscope. A trace can be conductive on the surface but eaten underneath (rising resistance, intermittent contact).
  • Point-to-point continuity against the schematic (or a reference board): find the open or resistive links.
  • Through-hole vias: corrosion attacks the inner copper → a layer-to-layer link can be cut while looking intact on the surface.

Cleaning first (mandatory)

  1. Neutralise the electrolyte (conductive/corrosive): IPA + brush; alkaline battery leak → a little vinegar then IPA rinse, dry.
  2. Remove the attacked solder mask around the area, take the copper bare (gentle scrape, glass fibre).
  3. Do not refit a part until the area is clean and dry.

Repairing a cut trace

  • Short gap: solder bridge or a small wire (30 AWG wrap) soldered between two sound, tinned copper points. Secure with lacquer/glue.
  • Long break: wrap wire point to point (pin to pin of the part), pressed down and glued; re-do the solder mask (UV lacquer) to protect.
  • Rebuild a lifted pad: adhesive pad/eyelet kit, or solder the part's leg directly to the re-tinned trace + reinforcement.

Repairing a via

  • Cut through-hole via: run a thin wire through the hole, solder both sides (recreates the layer link). On multilayer, if an inner plane is cut, the wire must reach the correct node per the schematic.
  • Crimp eyelets (via repair kit) for a cleaner result.

EPROM legs / oxidised sockets

  • Blackened legs: clean, re-tin; if a leg is eaten, solder a leg stub or replace with a fresh programmed EPROM (EPROM).
  • Fit a turned-pin socket for future removals/refits.

Reflow & reball (QFP/BGA customs)

  • Cracked joints on a QFP (fine pitch): reflow with hot air + flux, or rework pin by pin with a fine iron + wick for bridges.
  • BGA (recent customs): reball with a preheater + hot air, stencil and balls — a delicate job, last resort.
  • Always preheat the board (multilayer) to avoid ripping traces and vias.

See also

Sources & attribution

  • Synthesis of established PCB repair techniques (retro/arcade).

Review & corrections

How this space is used

Spotted a wrong value, an outdated procedure, a chip reference that does not match your board? Say so here, with what you observed (model, board revision, serial number, measurement). Every report is cross-checked against a source before anything changes — an unverifiable correction is published as “reported by …, not cross-checked” rather than silently applied.

Reading is open to everyone; posting requires signing in with Discord. Reports from the wiki's declared reviewers are handled first; anyone else's are read too, but go through a human before anything is changed.