Fixing Broken Traces on Printed Circuit Boards (PCB): Techniques and Tips

When a printed circuit board (PCB) suffers damage to its traces, it can be a challenging task to repair. However, with the right tools and techniques, it is often possible to restore the integrity of the PCB. This article will guide you through the process of repairing both open and short-circuit traces, and provide tips for using solid wire replacements.

Understanding the Problem

Before embarking on the repair process, it's important to understand the types of traces that are affected. Surface traces can be repaired with solder bridges or small pieces of wire, especially if they are narrow and the board has a solder mask. For more extensive repairs, replacing the trace from end to end with a piece of wire is often the best approach.

Tips for Repairing PCB Traces

Fixing Open Circuit Traces

When a trace breaks in an open circuit, the following steps can be taken to repair it:

Scrape out 3-5 mm of new copper foil at the broken trace end of the PCB and apply a thin layer of solder with an electric soldering iron.

Take a thin copper wire of suitable length and tin it. Carefully solder the thin copper wire to the broken trace end of the PCB to connect the broken trace end.

Fixing Short Circuit Traces

To fix short circuits, follow these steps:

Open the PCB file, highlight the short-circuited network, and identify the closest and most likely connection point. Pay special attention to the short circuit inside the IC.

Choose a suitable place to break the wire by cutting it with a knife or another suitable method, and measure it with a multimeter to ensure the correct connection.

Preparing for Replacement

The first step in replacing a broken trace is to prepare the replacement wire. Remove 2 mm of insulation from one end of the wire. Ensure the wire maintains an even and EMC-compliant path on the PCB, avoiding any insulation violations.

Remove 2 mm of insulation from the other end of the wire.

Dip the wire ends in flux and surface mount both ends to the prepared PCB traces.

Use small parts of masking tape to keep the wire in direct contact with the PCB. Secure it in place with either conformal coating or cyanoacrylate (CA) drops 1 mm from each solder joint and every 20 mm, or by wetting the entire wire length between the PCB and the wire insulation.

Selection of Wire Size

The choice of wire size is crucial for effective trace replacement. Small traces can be replaced with 24-30 gauge wire, while larger traces require 22 gauge or heavier wire. Uninsulated bus wire can also be used for these repairs.

Extreme Conditions

If the trace is covered in solder mask, it must be scraped off at the entry point for soldering, and any insulation must be stripped from the ends of the wire. Form the wire over the route of the missing trace and secure it in place with CA or other glue to hold it firmly in position.

Conclusion

Repairing broken traces on PCBs can be a complex process, but with the right tools and techniques, it is often possible to restore functionality. By understanding the problem, preparing the appropriate replacement wire, and following the steps outlined in this article, you can successfully fix open and short circuit traces on your PCB.

For more information on PCB repair and related technologies, you can refer to the IPC (Institute for Interconnecting and Packaging Electronic Components) which offers rework certification training and supports the development of standards for circuit board repair.