How to Pick the Right JST Connector for PCB Harness

Choosing the right JST connector for your PCB harness means matching your electrical, mechanical, and assembly needs to the characteristics of each JST series. From the compact, low-current PH and ultra-fine SH/ZH families to the high-power VH line, pitch size dictates footprint and amperage limits. Mechanical features like locking latches and polarised housings prevent mis-mating, while PCB mount styles (through-hole, SMT, vertical, or right-angle) affect assembly and durability. Finally, consider wire-gauge compatibility, crimp versus IDC styles, environmental ratings, and required certifications. With these criteria, you’ll confidently pick a connector that delivers reliable performance. When volume ramps up, Romtronic, our in-house factory, stands ready to manufacture harnesses to your exact specifications.

Table of Contents

1. Compare JST Series

1.1 PH Series (2.0 mm pitch)

PH connectors feature a 2.0 mm pin spacing and compact housing, ideal for signal-level wiring in dense PCBs. They carry up to 2 A at AWG 24 and are rated for 100 V AC/DC, with a temperature range of –25 °C to +85 °C.

1.2 XH Series (2.5 mm pitch)

With a 2.5 mm pitch, the XH series handles higher currents (3 A at AWG 22) and voltages up to 250 V AC/DC. Their robust housing supports operation from –25 °C to +85 °C, making them a workhorse for power and control signals.

1.3 SM Series (2.5 mm pitch, wire-to-wire)

SM connectors employ a friction-lock latch for vibration resistance. They support a maximum of 3 A at 250 V and are common in automotive or drone harnesses where secure retention is critical.

1.4 SH/ZH Series (1.0–1.5 mm pitch)

For ultra-compact applications, SH (1.0 mm) and ZH (1.5 mm) offer minimal footprints but limit currents to about 1 A and voltages to 50 V. Their fine pitch suits miniaturised electronics but demands precise crimping.

1.5 VH Series (3.96 mm pitch)

VH connectors serve heavy-current needs—up to 10 A at AWG 16 and 250 V—with a secure locking device and wide contact spacing to manage higher power safely.

2. Match Pitch to Application

High-Density Boards: Choose SH/ZH (1.0–1.5 mm) for tight layouts, knowing you’ll cap out at ~1 A per circuit.
Mixed Signal & Power: PH (2.0 mm) and XH (2.5 mm) balance size and current, covering 2–3 A needs in consumer and light-industrial gear.
Heavy Power Feeds: VH (3.96 mm) supports thicker AWG 16–22 wires for currents up to 10 A.

3. Verify Electrical & Wire-Gauge Specs

Always consult the manufacturer’s datasheet for exact ratings. Exceeding AWG ranges risks poor crimps or overheating. For instance, PH typically uses 24–32 AWG, XH handles 22–30 AWG, and VH accepts 16–22 AWG.

4. Evaluate Mechanical Features

Locking & Polarisation: SM’s friction latch and XH’s keyed housings prevent mis-mating and loosening under vibration.
Housing Styles: Shrouded and polarised designs guide insertion and protect contacts, reducing assembly errors.

5. Choose PCB Mount & Assembly

5.1 Mount Styles

Through-Hole (THT): Superior retention under mechanical stress, ideal for heavy cables.
Surface-Mount (SMT): Enables pick-and-place automation but may need reinforcement in vibration zones.
Right-Angle vs. Vertical: Right-angle headers help manage cable routing in tight enclosures.

5.2 Crimp vs. IDC

Crimp-Style Contacts: Deliver reliable performance using proper tooling; expect 1.0–3.0 A ratings depending on the series.
Insulation Displacement (IDC): Fast assembly without stripping—HR series IDC handles 2 A at AWG 24 and 250 V, with a thin, high-density design.

6. Environmental & Compliance

Temperature Range: Most series support –25 °C to +85 °C; some high-temp variants extend further.
Certifications: When targeting regulated markets, look for UL, CE, and CSA marks on datasheets.

7. Selection Checklist

Series & Pitch: Match board density and current needs.
Electrical Ratings: Confirm current, voltage, and wire gauge.
Mechanical Locking: Choose latches or polarisation as needed.
Mount Style: Balance assembly method with mechanical strength.
Crimp vs. IDC: Weigh speed versus long-term reliability.
Environmental Factors: Verify temperature, vibration, and compliance standards.

When you’ve nailed your specifications, Romtronic—our wholly owned factory—can produce bespoke cable assemblies and PCB harnesses with exacting quality control, on schedule, and at scale.

Alex Wang

Alex Wang is the Marketing Manager at Romtronic, holding a degree in International Business. With 7 years of sales experience in the electronic cable and harness industry, he oversees marketing efforts across North and South America. He deeply understands the industry and excels in market analysis, providing tailored advice to help clients better plan their purchasing and sales strategies.