In the connector and wire harness industry, the JST XH series is a staple for wire-to-board applications. However, a persistent ambiguity exists in procurement and design: many stakeholders refer to it as “XH 2.54mm,” despite the official specification being 2.50mm.
As a professional manufacturer of connectors and custom wire harnesses, we believe it is essential to clarify the technical origins of this misconception and the engineering risks associated with it.
1. Technical Specification: The Standard Pitch
According to the official JST (Japan Solderless Terminals) technical datasheets, the XH series is designed with a 2.50mm pitch.
The series was developed for high-density mounting in a wide range of electronic equipment. Its primary metrics are metric-based:
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Official Pitch: 2.50mm
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Current Rating: 3A AC/DC (AWG #22)
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Voltage Rating: 250V AC/DC
2. Why is JST XH Frequently Misidentified as 2.54mm?
The confusion between 2.50mm and 2.54mm is not accidental. It stems from three primary factors:
A. The Legacy of the 0.1-inch Standard
Historically, the electronics industry was dominated by U.S. imperial standards. The 0.1-inch (2.54mm) pitch became the universal standard for pin headers, breadboards, and perforated boards (perf-boards). Because 2.50mm and 2.54mm are visually nearly identical, many engineers and buyers colloquially group them under the “2.54mm” umbrella.
B. Physical Tolerance in Low Pin Counts
For connectors with a low number of circuits (e.g., 2P or 3P), a 2.50mm female housing can often be forced onto a 2.54mm male header. This “accidental compatibility” in low pin counts creates the false impression that the two standards are interchangeable.
C. Search Engine and Supply Chain Optimization
In the e-commerce landscape, suppliers often include both “2.50mm” and “2.54mm” in product titles to maximize search visibility. Over time, “XH 2.54” has become a common but technically incorrect search term that reinforces the myth.
3. The Risk of Cumulative Error
While a 0.04mm difference seems negligible, it is a linear cumulative error. As the pin count increases, the misalignment becomes critical.
| Circuits (P) | 2.50mm Standard Pitch | 2.54mm Cumulative Pitch | Cumulative Error |
| 2P | 2.50mm | 2.54mm | 0.04mm |
| 5P | 10.00mm | 10.16mm | 0.16mm |
| 10P | 22.50mm | 22.86mm | 0.36mm |
| 20P | 47.50mm | 48.26mm | 0.76mm |
Consequences of Misalignment:
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Mechanical Stress on Solder Joints: If a 2.50mm XH header is forced into 2.54mm PCB holes, the pins will be tensioned outward. This can lead to cracked solder joints or delaminated pads over time.
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Contact Fatigue: Misaligned pins exert uneven pressure on the internal terminals. This degrades the plating and reduces the effective contact area, leading to increased contact resistance and potential overheating.
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Assembly Failure: For high-pin-count connectors (10P and above), the cumulative error exceeds physical tolerances, making it impossible to insert the connector without damaging the housing or pins.
4. Professional Guidance for Procurement and Design
To ensure the long-term reliability of your hardware, we recommend the following:
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PCB Design: Always set your CAD library footprint to 2.50mm for JST XH. Do not use generic 0.1-inch (2.54mm) headers as substitutes in your layout.
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Clear Documentation: When requesting quotes for wire harnesses, specify “XH 2.50mm” to ensure the manufacturer utilizes the correct metric-standard molds.
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Alternative Standards: If your project requires strict 2.54mm compatibility (e.g., for use with standard DuPont headers), consider the Molex KK 254 series instead of JST XH.
Conclusion
Precision is the foundation of electrical connectivity. While the industry may continue to use the term “XH 2.54” loosely, rigorous engineering requires adherence to the 2.50mm standard.
As a manufacturer specializing in high-quality compatible connectors and wire harnesses, we provide technical verification for all our components. Contact our engineering team for precise specifications or custom wire harness samples.