In electronics, cost reduction is a constant theme. To save a few cents, engineers have tried many unconventional approaches — using PCB traces as antennas is already a familiar practice in the industry. Carefully designed special traces take on the role of signal reception on the board, simplifying the BOM and eliminating the cost of buying a discrete antenna. Many real projects use this method, as shown in the case images below:
A more recent idea circulating in the industry is far more surprising: using a PCB trace to replace a fuse. In other words, the component that is supposed to open under overload and protect the circuit would be replaced by a copper-foil trace. Is this a clever cost-saving method, or a gamble with safety? The following sections break it down.
The conclusion first: it is technically feasible, but it is not recommended in practice.
How It Is Done Technically: Controlling Current with Copper Foil
The core idea of replacing a fuse with a PCB trace is straightforward: use the current-carrying limit of copper foil. By precisely controlling trace width, length, and thickness, the trace operates normally at rated current. When the circuit is overloaded and the current exceeds what the copper foil can withstand, the trace overheats and opens, interrupting the circuit.
A concrete example: a common PCB copper thickness is 35 μm. At a trace width of 1 mm, copper foil of this thickness can carry about 1 A per millimeter of width. If the circuit needs 5 A protection, a 5 mm-wide trace would theoretically be sufficient (in practice, length and heat dissipation must also be taken into account). Dedicated calculation tools are also available in the industry to determine the required parameters. For a target current of 10 A, for example, the required via count and temperature rise can be calculated explicitly:
Critical Risks That Cost Reduction Should Not Ignore
Although the method is technically possible, replacing a fuse with a PCB trace introduces hazards that cannot be avoided. These five risks cannot be bypassed:
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Once it fails, the board is scrap; repair means replacing the PCB.
A standard fuse can be replaced after it opens, at low cost and with little effort. After a PCB trace fuses, it cannot be replaced on its own. The entire board may have to be scrapped, which increases maintenance cost and wastes material.
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Safety risk is high: fire and secondary short circuits are possible.
When the trace opens, copper foil may splash metal balls and cause a secondary short. If the copper foil is designed incorrectly (too long or too short), it may fail to open in time and allow the input wiring to overheat and catch fire, or it may carbonize the PCB and damage nearby components.
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Fusing behavior cannot be controlled reliably.
A standard fuse can be specified for fast-blow or slow-blow operation. A PCB trace has only copper foil as the material, so response speed and consistency are poor. It may fail to open when it should, or open when it should not.
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Safety approval is unlikely, and the product may not be allowed on the market.
Exposed copper foil is easily affected by electrostatic discharge, moisture, and temperature variation, so stability is poor. Safety standards in many countries and regions — for household appliances and automotive electronics, for example — either prohibit this design or restrict it tightly. The design is unlikely to pass review.
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Design difficulty is high and may increase cost instead.
Drawing a trace is not enough. To obtain a usable fusing result, the parameters must be calculated precisely. A single-bend trace should be used rather than a serpentine trace, in order to reduce the effect of heat dissipation. Manufacturing tolerance requirements are extremely tight. A small error can make the protection ineffective and raise production cost instead.
Standard fuses, by contrast, are available in many ratings for different applications. Common types such as JSR30 and SR60 are established, safety-oriented choices:
Final Note: Cost Reduction Must Not Cross the Safety Line
Saving the cost of one fuse means accepting risks such as board scrap, safety incidents, and failed safety approval. Those losses far exceed the cost that was saved.
Whether the product is a household appliance, an automotive electronic system, or industrial equipment, a standard fuse is the more reliable choice. It meets safety standards, provides defined protection, and is easy to service later. The core of electronic design is reliability and safety. Cutting cost while ignoring these risks will cost more in the end.
