Overview of JST Connectors

JST connectors are compact, rectangular-shaped connectors that use a crimp-style connection method. They consist of two main components:

1. Housing – The plastic body that holds the metal contacts and provides insulation. JST housings come in different sizes, colors, and materials depending on the series.

2. Contacts – The metal terminals that carry current/signals and physically mate with the contacts in the corresponding housing. JST contacts are typically made of brass, phosphor bronze, or BeCu alloys plated with tin, gold, or silver.

To make a connection, stripped wire leads are crimped onto the contacts using a special crimping tool, then the contacts are inserted into the housing until they lock in place. JST connectors are designed for low-voltage DC power and signal applications up to around 600V and 10A, with operating temperatures up to 85°C or 105°C.

Naming Convention

JST connector series are named using a 2-3 letter abbreviation followed by the number of positions (poles) and the pin pitch in millimeters. For example:

• XH-04-2.5 = XH series, 4 positions, 2.5mm pitch
• SM-06B-SRSS-TB = SM series, 6 positions, SRSS locking type, top entry

Additional suffixes denote locking types, mounting styles, wire entry directions, PCB termination types, etc.

Common JST Connector Series

Now let’s look at some of the most widely used JST connector series and their key specifications:

XH Series

XH is one of the most popular JST series for general-purpose 2.5mm pitch wire-to-wire and wire-to-board connections. It offers up to 16 positions in a compact package with a double-contact lance design for high reliability.

Specs:
* Current rating: 3A max
* Voltage rating: 250V
* Pitch: 2.5mm
* Positions: 2-16
* Wire gauges: 22-28 AWG
* Mating cycles: 50

Applications:
* Battery packs
* Power supplies
* Lighting
* Consumer electronics
* Wire harnesses

PH Series

PH is a 2.0mm pitch connector commonly used for signal-level connections in consumer electronics, medical devices, and industrial equipment. It has a similar contact structure to XH.

Specs:
* Current rating: 2A max
* Voltage rating: 100V
* Pitch: 2.0mm
* Positions: 2-16
* Wire gauges: 24-32 AWG
* Mating cycles: 30

Applications:
* Laptops
* Printers
* Servos
* Sensors
* LED lighting

VH Series

VH is a high-current 3.96mm pitch connector for power applications up to 10A. It has a robust contact design with 2 points of contact for reliability.

Specs:
* Current rating: 10A max
* Voltage rating: 250V
* Pitch: 3.96mm
* Positions: 2-6
* Wire gauges: 18-22 AWG
* Mating cycles: 100

Applications:
* Power supplies
* Battery chargers
* Industrial equipment
* Electric vehicles
* Solar panels

GH Series

GH is a 1.25mm pitch connector optimized for high-speed signal transmission and EMI shielding. It offers 2-10 positions in a space-saving design.

Specs:
* Current rating: 1A max
* Voltage rating: 50V
* Pitch: 1.25mm
* Positions: 2-10
* Wire gauges: 28-32 AWG
* Mating cycles: 30

Applications:
* Tablets
* Cameras
* Wearables
* Medical devices
* Automotive electronics

SM Series

SM is a wire-to-board connector with a positive lock for cable assemblies. It has a low profile 2.5mm pitch design and an optional strain relief.

Specs:
* Current rating: 3A max
* Voltage rating: 250V
* Pitch: 2.5mm
* Positions: 2-12
* Wire gauges: 24-30 AWG
* Mating cycles: 25

Applications:
* Servo motors
* Stepper motors
* Encoders
* Industrial sensors
* Consumer appliances

ZH Series

ZH is an extra-compact 1.5mm pitch connector for high-density wire-to-board connections. It has a reliable contact design and optional side locks.

Specs:
* Current rating: 1.5A max
* Voltage rating: 100V
* Pitch: 1.5mm
* Positions: 4-32
* Wire gauges: 28-32 AWG
* Mating cycles: 25

Applications:
* Mobile phones
* Digital cameras
* Handheld devices
* Miniature sensors
* Medical equipment

Comparison Table

Here is a quick comparison of the JST connector series covered above:

Series	Pitch (mm)	Positions	Current (A)	Voltage (V)	Typical Applications
XH	2.5	2-16	3	250	Battery packs, power supplies, lighting
PH	2.0	2-16	2	100	Consumer electronics, medical devices
VH	3.96	2-6	10	250	High-power applications up to 10A
GH	1.25	2-10	1	50	High-speed signals, EMI shielding
SM	2.5	2-12	3	250	Servo/stepper motors, sensors
ZH	1.5	4-32	1.5	100	Compact handheld devices

As you can see, each series has its own strengths in terms of size, power handling, number of contacts, and target applications. Be sure to refer to the JST product catalog for complete specifications and compatibility information.

Crimping and Assembly

To ensure reliable connections, it’s important to use the correct crimp tooling and follow the proper assembly procedure for your JST connectors:

1. Strip the wire to the recommended length, being careful not to nick or cut the strands.

2. Select the appropriate crimp contact and tool setting for the wire gauge.

3. Insert the stripped wire into the contact barrel and crimp it using the tool. The crimp should be tight and free of wire strand protusion.

4. Gently pull on the wire to check the crimp integrity. The wire should not come out.

5. Insert the crimped contact into the housing cavity until it locks in place with an audible click. Repeat for all contacts.

6. Inspect the finished connector for any damage or misaligned contacts before mating.

JST offers both manual and pneumatic crimp tools, as well as semi-automatic crimping machines for higher volumes. Always refer to the JST assembly instructions and crimp specifications for your specific connector series.

Design Considerations

When designing with JST connectors, keep these guidelines in mind:

• Choose a connector series that meets your electrical and environmental requirements with some margin for safety.

• Consider the mating orientation, wire entry direction, and PCB mounting style that best fits your assembly process and space constraints.

• Allow enough clearance around the connector for the mating plug and wire strain relief.

• Follow the recommended PCB land pattern and hole sizes for your connector series.

• Use the appropriate crimp tooling and settings for your wire gauge to ensure gas-tight connections.

• Avoid excessive force when mating and unmating connectors to prevent damage to the housings or contacts.

• Consider using polarized or keyed connectors to prevent incorrect mating in multi-connector systems.

• Protect exposed connector contacts from dust, moisture, and debris when not mated.

Frequently Asked Questions (FAQ)

1. Can I mix and match JST connector series?

No, JST connector series are not interchangeable. Each series has its own unique housing and contact design that only mates with the same series. Always use mating connectors from the same series.

1. Are JST connectors waterproof?

Most JST connectors are not waterproof by default. However, some series like the ZE and XT offer IP67-rated sealing options for use in wet or dusty environments. If you need a waterproof connector, look for a series with an integral seal or gasket.

1. Can I solder JST connectors instead of crimping?

No, JST connectors are designed for crimp termination only. Soldering the contacts can damage the plastic housing and lead to poor reliability. Always use the specified crimp tooling and procedure for your connector series.

1. How do I choose the right wire gauge for my JST connector?

Each JST connector series has a range of compatible wire gauges based on the contact size and current rating. Refer to the product specifications to find the recommended gauge range for your series. In general, choose the largest gauge that fits the contact and meets your current requirements.

1. Can I reuse JST connectors?

JST connectors are rated for a limited number of mating cycles, typically 25 to 100 depending on the series. While you can reuse them within this cycle life, it’s best to replace them once they show signs of wear or damage. Reusing worn-out connectors can lead to intermittent connections and failures.

Conclusion

JST connectors offer a reliable and versatile solution for wire-to-wire and wire-to-board connections in a wide range of applications. By understanding the different JST connector series, their specifications, and design considerations, you can select the right connectors for your project and ensure a solid electrical connection.

Remember to always use genuine JST connectors and tooling for the best performance and reliability. With proper selection and assembly, JST connectors can provide a compact, cost-effective, and robust interconnect solution for your low-voltage DC power and signal needs.