What Are The Different Types Of Connectors On A PCB?

Choosing PCB connectors feels overwhelming, right? Pick the wrong one, and your project hits a snag. Understanding the types helps you select wisely.
Connectors on a PCB bridge electrical pathways. Common types include wire-to-board (like JST, Molex), board-to-board (mezzanine, edge card), I/O (USB, HDMI, Ethernet), and RF connectors (SMA, U.FL). Each serves specific signal, power, or mechanical needs.

I've spent nearly 20 years in embedded systems, and if there's one thing I've learned, it's that connectors are far more than just plastic and metal bits. They are critical, often "invisible," components, especially when you're dealing with high-speed signals or power integrity. Thinking about them late in the design is a recipe for headaches. Let's break down what you need to know to keep your project moving smoothly.

What are the 3 types of cable connectors?

Staring at a pile of cables and wondering which connector does what? Using the wrong one means no connection or worse, damage. Let's clarify some common categories you'll encounter with PCBs.
For PCBs, cable connectors generally fall into: 1. Wire-to-Board (connecting discrete wires or multi-conductor cables to the PCB), 2. Board-to-Board (often via ribbon cables), and 3. Input/Output (I/O) connectors (linking the PCB to external devices or systems).

Exploring Cable Connector Categories

When we talk about cable connectors in the context of PCBs, we're usually looking at a few main scenarios. Each category serves a distinct purpose in linking your PCB to other parts of a system or the outside world. Understanding these helps in early-stage design planning. For instance, at Honeywell on the Tuxedo Keypad, we had all three types in one product: internal wire-to-board for sensors, ribbon cables for display modules, and USB/Ethernet for external I/O.

How to choose PCB connectors?

So many connectors, so little time! If you choose poorly, you might face signal degradation, mechanical failure, or even production nightmares. The key is a systematic approach.
Choose PCB connectors by evaluating: 1. Electrical needs (current, voltage, signal speed, impedance). 2. Mechanical aspects (size, orientation, mating cycles, retention). 3. Environmental conditions (temperature, humidity, vibration). 4. Cost and availability.

Detailed Guide to Connector Selection

Selecting the right connector is a critical design step. As I mentioned, connectors are not just passive parts; they can be performance bottlenecks if chosen carelessly, especially for signal integrity (SI) and power integrity (PI). When I led hardware design for a next-gen infusion pump at Smiths Medical, connector selection for sensor integration was paramount – we needed high reliability and specific current ratings, often down to a few milliamps, but with very low contact resistance.

How do you connect two PCB boards together?

Need to link two circuit boards? A shaky connection can bring down your whole system. Reliable inter-board links are crucial for modular designs and complex electronics.
Connect two PCB boards using board-to-board connectors (like mezzanine/stacking or edge connectors), ribbon cables with IDC connectors mating to headers, or flexible printed circuits (FPCs) with specialized FPC connectors.

Methods for Inter-PCB Connection

Connecting multiple PCBs is common, and the choice of method impacts mechanical design, signal integrity, and cost. In aerospace projects, I've relied heavily on rugged board-to-board connectors for vibration resistance, while consumer products often use FPCs for their flexibility in tight spaces.

What are JST connectors used for?

You've seen those small white connectors, right? Not knowing what they are can stop your prototyping or repair dead in its tracks. Let's demystify them.
JST connectors, a brand name from JST Mfg. Co., refer to a wide variety of wire-to-board and wire-to-wire connectors. They are commonly used for low-power applications, batteries, sensors, motors, and internal wiring in consumer and industrial electronics.

Understanding Common JST Series

JST is a major manufacturer, and "JST connector" is a common term, but it covers many distinct series. It's crucial to identify the specific series by measuring pitch and checking features, as they are not interchangeable. For instance, the popular JST PH 2-pin is almost a standard for single-cell LiPo batteries in hobbyist electronics, but it's only rated for 2A.

(Note: Always verify with official JST datasheets for precise ratings, applicable wire gauges, and derating curves. Many "JST-style" connectors exist from other manufacturers; check their specs carefully.)

How to identify connector type?

Facing an unknown connector can be frustrating, especially when you need a mate or replacement. Panic sets in if you can't order the right part. But there's a method to this madness.
Identify a connector by: 1. Measuring pin pitch. 2. Counting pins/positions and rows. 3. Observing housing shape, color, and locking features. 4. Searching for manufacturer markings/part numbers. 5. Comparing to online catalogs using these parameters.

A Systematic Approach to Connector Identification

Identifying an unknown connector feels like detective work. Here’s a systematic approach I use, refined over years of debugging and reverse-engineering everything from elevator controls to photonic computing evaluation boards.

1. Measure Pin Pitch⁵

This is the distance from the center of one pin/contact to the center of the next. Use digital calipers for accuracy. Common pitches include: 0.3mm, 0.4mm, 0.5mm, 0.8mm, 1.0mm, 1.25mm, 1.27mm (0.05"), 2.0mm, 2.5mm, 2.54mm (0.1"), 3.96mm (0.156"). This is often the most critical dimension.

2. Count Pins and Rows

How many active positions are there? Is it a single row or dual row (or more)? For example, a "2x5 pin" connector has two rows of five pins each, for a total of 10 positions.

3. Observe Housing Characteristics

Note the housing's shape (rectangular, circular, D-shaped), color (though not always definitive), locking mechanisms (friction fit, latches, screws), and keying (slots/protrusions for orientation).

4. Look for Markings

Check for manufacturer logos (e.g., Molex flower, TE triangle, "JST") or any partial part numbers. These can be tiny, so a magnifying glass and good lighting are essential.

5. Determine Gender

Is it male (pins/blades) or female (sockets/receptacles)? For shrouded headers, the shroud is part of the male connector.

6. Consider Application Context

Where is it used? Power input (e.g., >5A may mean larger contacts), high-speed data (e.g., USB, HDMI have distinct shapes), RF signal (coaxial)? This can narrow down possibilities.

7. Utilize Online Resources

Distributor websites (Digi-Key, Mouser, Farnell) have powerful parametric search tools. Manufacturer websites (e.g., Samtec, Molex, TE, Hirose, JST) also have extensive catalogs. ConnectorBook.com is a great visual resource.

What is SMA in electronics?

You've probably seen "SMA" on Wi-Fi antennas or RF test equipment. If you're unsure what it is, you might overlook critical aspects of RF system design.
SMA (SubMiniature version A) connectors are coaxial RF connectors designed for high-frequency signals, typically from DC up to 18 GHz (some variants higher). They feature a 50-ohm characteristic impedance and a threaded coupling mechanism for secure connections.

SMA Connectors: Key Features and Considerations

SMA connectors are workhorses in the RF world. Their precise mechanical and electrical characteristics are vital. When I worked on the PACE evaluation board for a photonic chip at Lightelligence, ensuring clean SMA connections for high-speed test signals (multi-GHz) was absolutely critical; a poorly torqued or damaged connector could invalidate days of testing.

What are the different types of PCB spacers?

Mounting PCBs securely and with proper clearance is essential. Using the wrong spacer or standoff can lead to shorts, mechanical stress, or thermal issues.
PCB spacers (or standoffs) create and maintain space between PCBs or between a PCB and a chassis. Common types include threaded (male-female, female-female), unthreaded (clearance), and snap-fit, made from materials like nylon, brass, or stainless steel.

PCB Spacers and Standoffs: Materials and Types

Spacers and standoffs are humble but crucial hardware. The choice impacts assembly, electrical safety, and mechanical stability. In industrial automation projects, I've often used hex brass standoffs for their strength and ability to be tightened securely, ensuring PCBs didn't vibrate loose.

Spacer/Standoff Materials

Spacer/Standoff Types

How does an FPC connector work?

Connecting those paper-thin flexible circuits can be tricky. If you don't understand how FPC connectors work, you risk damaging the cable or getting an unreliable connection.
FPC (Flexible Printed Circuit) connectors secure FPCs by clamping them. Most use a ZIF (Zero Insertion Force) or LIF (Low Insertion Force) mechanism where an actuator presses the connector's contacts against the FPC's conductive traces, ensuring electrical continuity.

The Mechanics of FPC Connectors

FPC connectors are designed for the delicate nature of Flexible Printed Circuits (FPCs) or Flat Flexible Cables (FFCs). The clamping mechanism is key to a reliable connection without damaging the thin traces. I've seen many field failures in compact medical devices due to improperly seated FPCs – the actuator wasn't fully closed, or the cable was inserted skewed.

(Critical: Always ensure FPC is fully inserted (often visual markers on FPC help), aligned, and actuator (if ZIF) is properly closed. Match FPC/FFC thickness (e.g., standard 0.3mm including stiffener) to connector specs. Contacts can be top, bottom, or dual.)

What is the difference between FFC and FPC connectors?

FFC, FPC... they sound alike and connect alike, causing confusion. Using the terms or connectors incorrectly can lead to miscommunication or incompatible parts. Let's clear this up.
FFC (Flat Flexible Cable) is a simple cable with straight parallel conductors. FPC (Flexible Printed Circuit) is a custom-etched flexible circuit board, potentially with components. Connectors are often "FFC/FPC" compatible if pitch and thickness match, but the cables/circuits themselves differ in complexity.

Distinguishing FFCs from FPCs

While the connectors used for FFCs and FPCs can often be the same (hence "FFC/FPC connector" designation by manufacturers like Molex or TE Connectivity), the flexible elements themselves are quite different. Understanding this helped me specify the right flexible interconnect for many projects, from simple display FFCs to complex FPCs with integrated sensors.

(Note: Many connectors (e.g., ZIF, LIF) are designated "FFC/FPC compatible" if critical dimensions like pitch (e.g., 0.5mm, 1.0mm), conductor width/spacing, and overall thickness at the insertion point (e.g., 0.3mm ±0.05mm including stiffener) match the connector's specifications.)

Conclusion

Choosing PCB connectors correctly is vital. It involves balancing electrical needs, mechanical constraints, and the intended application to ensure reliable system performance. Remember, they're active parts of your design.