Printed circuit boards (PCBs) incorporate various connectors establishing critical interfaces for input power delivery, data signals, component modularity, and production programming/testing. Different connector types suit the specialized connectivity needs across consumer, automotive, telecom, industrial and other electronics applications. Understanding PCB connector varieties, attributes and implementation considerations helps designers select appropriate options matching desired functionality.
Common PCB Board Connectors
Myriad connector families work across frequent use cases:
Edge Board Connectors
The most prevalent, edge connectors align PCB cards into slotted receptacles in motherboards enabling compact daughtercards expansion. High-density options reach >1000 pins for add-in bus extensibility.
Wire-to-Board Headers
Vertical pin receptacles solder onto PCBs mating with insulation displacement or crimped wire harnesses for power and signals. Provide field wiring terminations.
Card Edge Contacts
Exposed gold-plated copper fingers along board edges make reliable connections inserts directly plugging into mating connectors. Used heavily on modules and memory cards.
Board-to-Board Connectors
Interconnect smaller PCBs internally to routing backbone boards. Stacking headers with standoffs provides alignment. High-speed signal options exist.
Coaxial Connectors
Transmit RF signals between boards, test equipment, antennas and transmission lines. Impedance-controlled designs match characteristic line impedances minimizing reflections.
Discrete Wiring
Individual wired cable connections solder directly to boards at thru-hole pads or surface mount points provide basic non-connectorized interfaces.
Key Electrical Characteristics
Critical attributes guide connector selection for target applications:
| Parameter | Considerations | Concerns |
|---|---|---|
| Pitch | Distance between adjacent pins/pads | Affects achievable interconnect density |
| Current Rating | Maximum recommended per-pin sustained current without overload | Excess heating damages connectors |
| Voltage Rating | Maximum permissible voltage between adjacent pins | Potential arcing risks insulation breakdown |
| Contact Resistance | Source of voltage drops affecting low-level signals | Poor connections increase resistance graduating signal levels |
| Inductance/Capacitance | Intrinsic interconnect passive component properties | Alters signal propagation changing shape or timing |
Matching electrical qualities to signal types ensures proper connectivity across interfaces.
Interconnect Physical Attributes
Mechanical construction determines connector viability across deployment contexts:
| Characteristic | Description | Example Variations |
|---|---|---|
| Mounting Style | Attachment means to PCB | Through-hole pins, surface mount tabs/pads, press-fit stubs |
| Durability | Component lifecycle longevity – insertions/withdrawals before failure | 50 up to 10,000+ cycles meets goals from prototyping to field usage |
| Pitch Options | Supported gaps between adjacent pins/pads | 0.4mm to 2.54mm or greater spacing |
| Current Ratings | Range of allowable sustained amperages per pin | 0.5A signals to 10A+ power delivery |
| Circuit Counts | Number of distinct signal/power connections | As few as 2 to several hundred in complex interfaces |
| Polarization Keys | Physical means preventing misoriented insertion | Corner chamfers, bump offsets, asymmetry between ends |
Careful connector matching aids PCB interconnection success.
Specialized Connection Applications
Requirements driving many electronics links demand connectors with unique capabilities:
High Density – Thousands of contacts in small footprints route multitudes of signal, storage and data traffic. Sergeant strips, dual beam contacts and staggered grids pack connections.
High Speed – Controlled geometries with ground shields reduce signal distortion across interfaces carrying multi-Gigabit serdes channels. Impedance tuning ensures wave propagation fidelity.
Ruggedized – Plated metal shields grounded to chassis divert electrical noise away from contacts in demanding environments with vibration, fluids and debris. Redundant pins provide fault tolerance should individual connector circuits fail from abuse or wear.
Hot Swap – Special pin sequencing allows installing/removing modules without external equipment power interruption across live backplanes. Ensure proper grounding precedes signal or supply activation preventing damage.
Hermetic Sealing – Glass/ceramic insulation plus specialized epoxy encapsulation protects solder joints and prevents air/moisture ingress along connectors securing interior PCB integrity across temperature extremes or immersed conditions.
These illustrate connector optimization toward niche link demands.
Implementation Best Practices
Following design rules for integrating connectors facilitates manufacturing and enhances field reliability:
- Position connectors early aligning placement to enclosure cutouts and mating equipment
- Include generous keep-out zones around connectors leaving ample working space
- Consider production processes selecting compatible mounting styles
- Incorporate mechanical reinforcement securing connectors likely suffering customer wiring strains
- Add test points probing essential signals aiding diagnostics
- Review orientation avoiding upside-down misalignments
- Clarify pull directions
- Verify connector ratings meet worst-case needs with margin
Thoughtful planning avoids issues arising from overlooked connectivity assumptions needing last-minute corrective actions.
Connector Comparison Guide
Balancing options against critical considerations aids selections:
| Parameter | Edge Board | Pin Header | Card Edge | Coaxial |
|---|---|---|---|---|
| Programmability | Mediocre | Low | Poor | Very Limited |
| Signal Integrity | Fair | Varies | Excellent | Outstanding |
| Assembly Complexity | Simple | Medium | Complex | High |
| Cost Factors | Low | Very Low | Medium | High |
| Ruggedness | Low | Medium | High | Medium |
| Orientation Control | Fair | Good | Fair | Excellent |
Matching distinct strengths to specific connectivity contexts optimizes PCB interfaces.
FAQ
What are the most common connectors used on consumer PCBs?
Consumer electronics emphasize compact formats and mass assembly optimization. High density card edge connections suit expansion while vertical pin headers offer manufacturing simplicity wiring boards internally to external cables and accessories.
How do designers determine number of required connector pins?
Summing signals for directly-linked components indicates baseline interconnect needs. Adding grounded drain lines between signal groupings prevents crosstalk along the connector. Further duplicating certain critical power or data pairs builds redundancy coping with individual pin failures.
Can connectors get damaged while wave soldering boards?
Yes, connectors undergo thermal stresses requiring protection or selective attachments after reflowing other board components. Common methods include physical shielding, customized heating cycles, glue dot affixing connectors post-solder, or using screw terminals.
What checks validate connector mounting quality?
Thorough inspections after population verify flush pin alignment and top seating flatness against PCBs with no air gaps indicative of lifted pads suggesting latent solder fractures. Continuity testing confirms properly connected circuits through each pin while pull strength validates solid mounting adhesion to specification thresholds.
How do costs between connectors compare?
Basic wire-to-board headers and card edge fingers prove extremely inexpensive around $0.10-0.25 range suitable many applications. More complex coaxial multipin connectors for RF or ruggedized mounting situations can reach $50+ requiring strategic use only where capabilities warrant premiums.
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