# How to Choose High-Speed Board-to-Board Connectors for Your Design
📅 March 25, 2026 | 📂 High-Speed Connectors | 👤 Richmon
Choosing the right high-speed board-to-board connector is a critical decision in modern electronics design. Get it wrong, and you’ll face signal integrity issues, manufacturing problems, or supply chain headaches. This guide walks you through the selection process step by step.
## Start with Your Signal Requirements
Before looking at connector catalogs, define your signal requirements clearly. This forms the foundation of your entire selection process.
### Data Rate and Bandwidth
What data rate does your application need?
– **5 Gbps or below**: Standard high-speed connectors may be sufficient
– **10-25 Gbps**: Look for connectors with specified signal integrity performance
– **40+ Gbps**: Premium connectors with advanced shielding and impedance control
Remember that connector bandwidth must exceed your signal’s fundamental frequency. A 25 Gbps NRZ signal has significant energy at frequencies above 12 GHz. Check that the connector’s bandwidth specification accounts for this.
### Signal Type
Different signal types have different requirements:
– **Single-ended signals**: Easier to route, but more susceptible to crosstalk
– **Differential pairs**: Better noise immunity, require matched impedance and length
– **Multi-lane interfaces**: Need consistent performance across all lanes
For differential signals like PCIe or HDMI, the connector must maintain controlled differential impedance (typically 85 or 100 ohms) through the entire signal path.
### Signal Integrity Budget
Every interconnect in your signal path introduces losses:
– PCB traces
– Vias
– Connectors
– Cables
Allocate a portion of your total signal integrity budget to the connector. Typical high-speed connectors contribute:
– Insertion loss: 0.5-2 dB depending on data rate and design
– Return loss: -10 to -20 dB
– Crosstalk: -30 to -50 dB between adjacent pairs
If the connector eats too much of your budget, you’ll struggle to meet your overall performance targets.
## Define Your Mechanical Requirements
Mechanical constraints often narrow your connector options significantly.
### Board Spacing (Stack Height)
How far apart are your boards? Common stack heights include:
– 5-8 mm: Low-profile applications
– 10-15 mm: Standard spacing
– 20-30 mm: Large spacing with room for components
Some connector families offer multiple stack heights with the same footprint, giving you flexibility in mechanical design.
### Pitch (Contact Spacing)
Pitch determines how many signals you can fit in a given space:
– **0.4 mm**: Ultra-fine pitch for high-density applications
– **0.5 mm**: Fine pitch, common in compact designs
– **0.8 mm**: Moderate pitch, easier to route
– **1.0 mm+**: Standard pitch, more routing space
Smaller pitch means higher density but also tighter routing constraints and more demanding assembly requirements.
### PCB Real Estate
Consider the total connector footprint, not just the contact area:
– Mounting features
– Keep-out zones for signal routing
– Ground pad requirements
– Mechanical support features
A connector with smaller pitch may not save board space if it requires large ground pads or keep-out zones.
### Termination Style
How will you attach the connector to your PCB?
– **Surface mount (SMT)**: Preferred for high-speed signals, compatible with standard reflow processes
– **Through-hole**: Better mechanical strength, but requires wave soldering or selective soldering
– **Press-fit**: No soldering required, used in backplane applications
For high-speed designs, surface mount is typically the best choice because it minimizes signal path discontinuities.
## Evaluate Signal Integrity Features
For high-speed applications, signal integrity is the make-or-break factor.
### Impedance Control
The connector must maintain consistent impedance through the mated interface:
– **Single-ended impedance**: Usually 50 ohms
– **Differential impedance**: Usually 85 or 100 ohms
Impedance discontinuities cause reflections that degrade signal quality. Look for connectors with specified impedance tolerance, typically ±10% or better.
### Shielding
High-speed connectors need effective shielding to:
– Contain electromagnetic emissions (EMI)
– Protect signals from external interference
– Reduce crosstalk between adjacent signals
Shielding options include:
– Metal shields around signal contacts
– Ground contacts intermingled with signal contacts
– Full metal housing
For the highest data rates, choose connectors with integrated metal shielding.
### Crosstalk Performance
Crosstalk occurs when signals on one pair affect adjacent pairs. Check the connector’s crosstalk specification:
– Near-end crosstalk (NEXT)
– Far-end crosstalk (FEXT)
– Values should be -30 dB or better for high-speed applications
Some connector designs include ground contacts between signal pairs specifically to reduce crosstalk.
### S-Parameters
For demanding applications, request S-parameter data from the manufacturer:
– Insertion loss (S21)
– Return loss (S11)
– Crosstalk (S21 between ports)
This data allows you to simulate the connector’s behavior in your specific design using tools like SPICE or specialized SI software.
## Consider Assembly and Manufacturing
A connector that’s perfect electrically may be problematic in production.
### Soldering Process
– Is the connector compatible with your reflow profile?
– Does it require special solder paste or stencil design?
– Can it withstand multiple reflow cycles if you have double-sided assembly?
### Inspection and Test
– Can you inspect solder joints with AOI or X-ray?
– Are test points available for in-circuit testing?
– Does the connector support boundary scan testing?
### Rework
If a connector needs replacement:
– Is rework possible?
– What tools and skills are required?
– What’s the success rate for rework?
Some high-density connectors are difficult or impossible to rework, making early design decisions critical.
## Plan for Supply Chain Reliability
Technical performance means nothing if you can’t get the connector when you need it.
### Lead Time
– What’s the standard lead time?
– Does the manufacturer stock inventory, or is everything made to order?
– Are there allocations or restrictions on availability?
Lead times for specialized connectors can extend to 20+ weeks. Plan ahead and consider safety stock.
### Distribution Channels
– How many authorized distributors carry this product?
– Is it available through catalog distributors for prototypes?
– Can you buy directly from the manufacturer?
Multiple distribution channels reduce supply risk and give you more pricing options.
### Second Source Options
Having a second source protects you from:
– Manufacturer supply problems
– Price increases
– Quality issues
– End-of-life notices
Check if equivalent connectors exist from other manufacturers. Not all high-speed connectors have direct equivalents, so this should influence your selection.
### Lifecycle Status
– Is this a new product or established design?
– Has the manufacturer announced end-of-life?
– How long will this product be supported?
Avoid connectors that are near end-of-life unless you have a specific reason to use them.
## Verify Compliance and Certifications
Depending on your application, various certifications may be required.
### Environmental Compliance
– **RoHS**: Required for products sold in EU and many other markets
– **REACH**: Chemical registration for EU market
– **Halogen-free**: Required by some applications
### Safety Certifications
– **UL recognition**: For products sold in North America
– **CSA**: Canadian standards
– **TUV/VDE**: European safety standards
### Industry-Specific Standards
– **AEC-Q200**: Automotive qualification
– **MIL-spec**: Military applications
– **Medical device standards**: IEC 60601
## Document Your Decision
Create a selection record that captures:
– Your requirements
– Connectors evaluated
– Test results or simulation data
– Rationale for final selection
– Any risks or concerns
This documentation helps with:
– Design reviews
– Future projects with similar requirements
– Troubleshooting if issues arise
– Qualification and validation activities
## Get Samples and Test
Before committing to production:
– Order samples for prototype testing
– Verify mechanical fit in your enclosure
– Test signal integrity in your actual design
– Confirm assembly process compatibility
Testing reveals issues that aren’t apparent from datasheets alone.
## Work with Your Sourcing Partner
Whether you’re working with authorized distributors or independent sourcing partners, leverage their expertise:
– **Technical support**: Many distributors have application engineers who can help with selection
– **Availability information**: They know what’s in stock and what’s allocated
– **Pricing**: Volume pricing and availability can vary significantly
– **Alternative options**: They can suggest equivalent parts if your first choice isn’t available
For projects requiring flexibility in quantities or hard-to-find components, independent distributors often provide valuable support.
## Quick Selection Summary
| Step | Key Questions |
|——|————–|
| Signal Requirements | Data rate? Bandwidth? Signal type? |
| Mechanical | Stack height? Pitch? Footprint? |
| Signal Integrity | Impedance? Shielding? Crosstalk? |
| Manufacturing | Assembly process? Inspection? Rework? |
| Supply Chain | Lead time? Second source? Lifecycle? |
| Compliance | RoHS? Safety? Industry standards? |
## Conclusion
Choosing high-speed board-to-board connectors requires balancing electrical performance, mechanical constraints, manufacturability, and supply chain considerations. Start with your signal requirements, evaluate options systematically, and document your decisions.
Take time to test samples in your actual design before committing to production. The investment in thorough evaluation upfront prevents costly problems later.
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*Need help selecting connectors for your high-speed design? Contact Richmon for technical support and sourcing assistance.*