Embedded-cHow-ToBeginner · 3 min read

How to Find Broken Trace on PCB: Simple Methods Explained

To find a broken trace on a PCB, use a multimeter set to continuity mode to test the electrical path between points. Visually inspect the PCB for cracks or burns, and use a magnifying glass or microscope to spot fine breaks in the copper traces.

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Syntax

Here is the basic process to test a PCB trace using a multimeter:

Set multimeter to continuity mode: This mode beeps when two points are electrically connected.
Place probes on trace ends: Touch the multimeter probes to the start and end points of the trace.
Check for beep or resistance: A beep or near zero resistance means the trace is intact; no beep or high resistance means a break.

python

Multimeter.setMode('continuity')
Multimeter.placeProbe('start_point')
Multimeter.placeProbe('end_point')
if Multimeter.beep() or Multimeter.readResistance() < threshold:
    print('Trace is good')
else:
    print('Trace is broken')

Output

Trace is good

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Example

This example shows how to use a multimeter to find a broken trace on a PCB by checking continuity between two points.

python

class Multimeter:
    def __init__(self):
        self.mode = None
    def setMode(self, mode):
        self.mode = mode
    def placeProbe(self, point):
        print(f'Probe placed on {point}')
    def beep(self):
        # Simulate beep if trace is good
        return True
    def readResistance(self):
        # Simulate low resistance for good trace
        return 0.5

multimeter = Multimeter()
multimeter.setMode('continuity')
multimeter.placeProbe('Trace Start')
multimeter.placeProbe('Trace End')
if multimeter.beep() or multimeter.readResistance() < 1:
    print('Trace is good')
else:
    print('Trace is broken')

Output

Probe placed on Trace Start Probe placed on Trace End Trace is good

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Common Pitfalls

Common mistakes when finding broken traces include:

Not setting the multimeter to continuity mode, causing no beep even if trace is good.
Testing on solder mask instead of exposed copper, leading to false breaks.
Ignoring visual inspection; some breaks are visible as cracks or burns.
Not cleaning the PCB surface, which can cause poor probe contact.

python

Wrong way:
Multimeter.setMode('voltage')  # Incorrect mode
Multimeter.placeProbe('start')
Multimeter.placeProbe('end')
# No beep, but trace might be good

Right way:
Multimeter.setMode('continuity')
Multimeter.placeProbe('start')
Multimeter.placeProbe('end')
# Beep confirms trace integrity

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Quick Reference

Step	Action	Tip
1	Visual Inspection	Use magnifier to spot cracks or burns
2	Set Multimeter	Choose continuity mode for testing
3	Probe Placement	Touch probes on trace ends or pads
4	Check Result	Beep or low resistance means good trace
5	Clean Surface	Remove dirt or solder mask for better contact

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Key Takeaways

Use a multimeter in continuity mode to test PCB traces for breaks.

Visual inspection with magnification helps find visible cracks or damage.

Ensure probes contact exposed copper, not solder mask or dirt.

A beep or low resistance reading means the trace is intact.

Clean the PCB surface before testing to avoid false results.