Printed circuit boards (PCBs) form the core of electronics products. Traces on the PCB conduct signals between components. If a trace gets damaged, it can disable the circuit. Instead of scrapping the PCB, trace damage can often be repaired. Specialized PCB trace repair kits provide materials and tools to fix broken traces quickly. This article provides a step-by-step guide to PCB trace repair using such DIY kits.

Overview of PCB Trace Repair Kits

PCB trace repair kits contain supplies to fix open or damaged traces and pads. A basic kit usually includes:

• Conductive ink pen – repairs broken trace sections
• Protective lacquer – isolates repaired areas
• Precision tips – enable fine trace repairs
• Cleaning accessories – prep surface before repair
• Magnifier – helps detailed work

The core item is the conductive ink pen which recreates broken trace segments. The ink dries into a flexible conductive material repairing the electrical path. Other items aid the repair process.

More extensive kits add soldering accessories, replacement components, trace isolation materials, tools like tweezers and probes, and detailed manuals. However, even a basic kit with just the pens can fix many trace issues.

Example PCB trace repair kit

When to Repair Instead of Discarding PCBs

Common situations where PCB trace repair is worth trying instead of scrapping boards:

• Prototyping – Fixing faults iteratively on prototype boards before final design.
• Small Volume Boards – Unique/expensive boards where purchasing replacements has lead time and cost.
• Legacy Boards – Old boards where replacements are unavailable.
• Fast Turnaround – Faster to repair on-hand boards than order and wait for new ones.
• Intermittent Issues – Flaky boards where problem is hard to reproduce.
• Cosmetic Damage – Scrapes/nicks on surface that cut a trace completely.
• Pad Repair – Missing pads prevent soldering components.

As long as the PCB substrate itself is intact, many types of trace-level damage can be repaired. This avoids unnecessary scrap costs.

Precautions When Repairing PCB Traces

Trace repair looks easy but requires care to succeed:

• Review Schematics – Understand where the trace was routed and its connections.
• Note Overall Damage – Assess if issues are limited to traces or more extensive.
• Clean PCB – Remove all debris, residue and dust from repair area.
• Magnify Work Area – Use a magnifier to clearly see fine traces.
• Fine Control – Rest hands/arms to avoid shaking.
• Verify Results – Inspect repair and test circuit before reassembly.

Rushing through repairs by taking shortcuts usually leads to failures. Careful attention to details ensures a working fix.

Step-by-Step Process for PCB Trace Repair

Here is a walkthrough of the trace repair process using a typical repair kit:

1. Assess Damage

• Visually inspect the PCB to identify trace damage. Look for complete breaks in traces or scratched off areas.
• Cross-check against board schematics to understand where the trace was routed and its connections.
• Determine if surrounding areas are also damaged. Restrict repair to trace-level damage only.

2. Clean PCB Area

• Clean the work area using the provided cleaning swabs/pads and alcohol solvent.
• Remove all dirt, oxidation, residues or debris surrounding the damaged trace area.
• Allow area to fully dry before continuing. Proper cleaning enables the repair to adhere.

3. Prepare Conductive Ink Pen

• Select an appropriate tip size and attach it to the pen. Use finer tips for thin or intricate traces.
• Shake the pen to mix the conductive ink which settles over time.
• Prime the pen by pressing until ink flows out evenly. This prevents erratic flow.
• Adjust ink flow if needed by turning the adjustment screw on the pen body.

4. Trace Repair Outline

• Study the damaged trace path and determine where the ink will be applied to bridge the gap.
• Lightly sketch along this path with a non-conductive pen as a guide for the actual conductive ink trace.

5. Apply Conductive Ink

• Using the primed conductive ink pen, carefully draw a path following the outline to link the severed trace ends.
• Try to recreate original trace dimensions – match width and follow original routing.
• Overlap about 1 mm onto undamaged areas on each side for a robust joint.
• Let ink fully dry. Apply a second pass if conductance is inadequate.

6. Test Conductivity

• Use a multimeter or ohmmeter to check resistance along repaired trace. It should indicate continuity.
• If no conduction, apply more ink over area to build up material. Let dry and recheck.

7. Apply Protective Coating

• Paint a thin layer of the provided protective lacquer over the repaired region using an applicator.
• Let protective coating dry fully to prevent smudging.
• Optional step for extra isolation – helps prevent long term corrosion.

8. Reassemble and Test

• If access permits, hand solder components to restored pads to verify conduction.
• Fully reassemble the PCB and test its functionality. The circuit should operate normally now.

With practice, even intricate trace repairs can be executed reliably using this careful approach.

Tips for Repairing Different Trace Damage Cases

Besides complete breaks, various types of trace damage can occur. Here are tips for addressing each case:

Broken Trace

• Bridge over the severed segment with conductive ink using multiple coats if needed for conductance.

Missing Pad

• Rebuild pad area with conductive ink. Allow curing well to withstand soldering.

Damaged Solder Pad

• Remove residual solder mask carefully using a craft knife. Repair pad outline with ink.

Scraped Trace Area

• Lightly abrade scraped region to expose fresh conductor. Ink over it.

Partial Width Trace Scratch

• Build up trace thickness along scratched portion using added ink coats.

Oxidized Copper Trace

• Use fiberglass brush gently to reveal conductive copper before inking over.

With the right techniques, diverse trace damage scenarios can be successfully repaired.

Limitations of PCB Trace Repair

While trace repair kits are versatile, some limitations exist:

• Very fine sub-1-mm traces are difficult to repair reliably.
• Recreating complex pad geometries or dense via patterns may not be feasible.
• Repairs lack long term robustness versus original copper traces.
• Conductive ink pens have finite usage life and variable results.
• Repairs are temporary if root cause of damage remains unaddressed.
• Severe substrate damage affecting layers cannot be fixed.
• High voltage, high frequency or precision analog circuits may not function properly after repair.
• Insufficient cleaning and surface prep will undermine repair quality.

Understanding these caveats helps determine if repairing a particular board and type of damage makes sense over replacement.

Troubleshooting Common Trace Repair Issues

Problems during trace repair are usually fixable with the right corrective measures:

Issue	Possible Causes	Corrective Actions
No conduction after repair	– Insufficient ink thickness <br>- Ink smudged before drying <br>- Overlaps with undamaged areas inadequate	– Apply more ink coats <br>- Allow each coat to dry fully before next <br>- Extend overlap with existing trace segment
Ink flows unevenly	– Tip clogged <br>- Ink viscosity too high/low	– Clean tip opening <br>- Adjust pen ink flow as needed
Repaired trace conducts initially but fails later	– Flexing cracks ink trace over time <br>- Environmental exposure degrades ink	– Reinforce with additional protective coating <br>- Minimize mechanical stress on repaired trace
Solder pad lifted during repair	– Excessive heating during desoldering <br>- Aggressive scraping of residual mask	– Use desoldering braid instead of hot air <br>- Remove mask carefully by scraping edges first
Repaired board functions inconsistently	– Intermittent conduction along repaired area <br>- Unidentified damage elsewhere on board	– Use multimeter to isolate conduction faults <br>- Thoroughly inspect board for any other issues needing repair

With good troubleshooting practices, most repair issues can be diagnosed and rectified.

Ensuring Long Term Reliability of Repairs

To improve long term reliability of trace repairs:

• Flow slightly more ink than needed to create a robust conductor.
• Overlap repaired and undamaged areas well for strong adhesion.
• Apply protective coating to prevent corrosion over time.
• Avoid mechanical stress on repaired trace – handle board carefully.
• Periodically check repairs for deterioration and touch up if required.
• If possible, run board at slightly lower than rated temperatures.
• For very high reliability, consider having repaired boards professionally conformal coated.

With extra care during repair and follow-up maintenance, boards can function successfully long term following fixes.

PCB Trace Repair Alternatives

For damage beyond DIY repair capabilities, alternatives include:

Professional Repair Services – Many PCB assembly vendors offer repair services for complex damage. Useful for mission-critical boards.

Board Redesign – For systemic issues, re-designing the board with modifications may be better than repeated repairs.

Board Protection – Conformal coatings, potting, protective enclosures can prevent future damage.

Better Handling Procedures – Many trace issues result from mishandling or weak packaging. Improving board handling minimizes damage.

Component-Level Repair – Swapping damaged components may be simpler than repairing traces.

Cabling – Using external cabling to bypass damaged areas on the PCB.

Combining DIY trace repairs for accessible issues and other solutions for severe damage provides a robust repair strategy.

Conclusion

PCB trace repair kits are a quick, affordable way to fix damaged traces and avoid discarding boards. With careful assessment of damage, preparation of the work area, precision use of conductive ink pens, and rigorous testing, broken traces can be restored successfully. Understanding repair limitations, troubleshooting issues, and implementing reliability best practices ensures long-lasting fixes. For optimal results, trace repair should be used alongside other mitigation approaches like enhanced handling procedures and board-level protection. By harnessing trace repair techniques, companies can save time and cost when dealing with damaged PCBs.

Frequently Asked Questions

Can solder mask repairs be done with trace repair kits?

No, the ink in basic kits is not formulated to adhere to solder mask surfaces. Special epoxy compounds and processes are required for solder mask repairs which most DIY kits do not provide.

How long does conductive ink take to dry?

Drying time depends on the ink chemistry, with most types drying within 5-10 minutes at room temperature. Curing can be accelerated by gently heating the board after ink application.

Can surface mount pads be repaired with these kits?

Yes, SMT pads can be reconstructed using the conductive ink but extra precision is required due to their small size. Allowing longer curing time improves durability for soldering.

Do the kits only work on copper traces?

The ink adheres well to copper so it works very effectively for copper traces. Performance will be degraded on other surfaces like gold or tin-plated traces.

How many times can a pen be used before replacing?

Dependent on the kit, each ink pen typically allows 10-25 repairs before needing replacement. Higher-end pens may enable more repairs. Checking conductivity after each repair detects any degradation in ink quality.