Pick a connector for board-to-board stacking

No wires here: two boards plug straight into each other as a stack, mezzanine pair, or card and backplane. The spec that sneaks up on people is mated stack height—the exact distance between the boards after mating. Most families offer several heights behind nearly identical part numbers, so “same series” does not mean “same mechanical fit.”

Basic orientation, deliberately number-free

This is the basic map, from hobby stacking headers through industrial mezzanine pairs and classic backplanes. There are no current, cycle, or dimensional values here; those come from the exact family's height tables, per-pin ratings, and tolerance data. Once impedance-controlled mezzanine or modern backplane signal integrity enters the conversation, you've crossed into high-speed design. Bring the manufacturer's SI documentation and the right specialist with you.

Use this when

• Two PCBs mount rigidly, parallel (or perpendicular), and permanently-ish to each other — a daughtercard, a module on a carrier, a display on a controller, a card in a rack.
• The interconnect density or repeatability of a direct board joint beats running a wire harness between the boards.
• The assembly comes apart for service occasionally, not daily — board-to-board families are mostly low-cycle.

Avoid this when

• The boards move relative to each other, can't hold tight coplanarity, or live in different mechanical assemblies — use a short FFC/FPC jumper or a wire-to-board harness instead (internal PCB harnessing); a flex bridge forgives what a rigid stack cannot.
• The interface is external, sealed, or field-serviced — that's a panel connector problem (sealed feedthrough, defense/rugged I/O).
• The joint sees severe vibration with no mechanical support plan — §2's caution applies: a board-to-board connector without standoffs or rails is a fretting experiment.
• You need frequent mating (a dock, a test interface) — check cycle ratings first; consider pogo/spring-pin docking or a debug/service port architecture instead.

Families to start with

• 0.1 in / 2.54 mm stacking headers — the Arduino-shield / Raspberry Pi-HAT pattern: female socket strips plus long-tail stackable headers. Cheap, everywhere, friction-fit, and unpolarized — fine for bench and maker stacks, with the same offset/reversal traps as their Dupont cousins.
• Shrouded / keyed header pairs (2.54 mm class) — the production upgrade: polarization and pin protection for the same job.
• 2 mm and 1.27 mm pin/socket strips — the density step between 0.1 in and true fine pitch; PC/104-heritage stacks live here.
• Fine-pitch mezzanine systems — defined mated-height SMT pairs with alignment features: Hirose DF40-class, Molex SlimStack, Samtec's mezzanine ranges, and TE/Harwin equivalents. This is the modern SBC/module standard — and where the mated-height table and pick-the-pair discipline matter most.
• Card edge — the connector lives on one board and mates with plated fingers on the other (PCIe/M.2-style, legacy gold-finger cards). Cheapest possible second half; cycle life and reliability ride on the finger plating and bevel.
• DIN 41612 / IEC 60603-2 (Eurocard/backplane class) — the classic rack card-to-backplane pin-and-socket family; still everywhere in industrial and legacy systems. Press-fit (compliant-pin) termination is common on backplanes.
• Pogo / spring-pin arrays — compressible contacts for docking, test fixtures, and battery-style interfaces; a different mechanical philosophy (sliding/compressing wipe, external retention required).

The two rules in one picture: the standoffs carry the load, and the connector pair is ordered to the mated stack height.

Search terms

• board to board connector mated height 8mm 0.8mm pitch
• stackable header extra long pins 2.54mm
• mezzanine connector pair receptacle header stack height
• DIN 41612 connector 64 pin type B backplane
• card edge connector 2.54mm gold finger
• spring loaded pogo pin connector board

Specs to check

• Mated stack height, from the manufacturer's height table — and that your two part numbers are the matched pair for that height. Same family, wrong height code = no mate, or a stressed one.
• Polarization / anti-offset — can the boards assemble shifted by one row or rotated? Unpolarized strips can; keyed and shrouded families can't.
• Alignment capture — self-alignment range, guide features, or guide pins, especially where the stack assembles blind.
• Mating cycles — often low, and lower as pitch shrinks. Match to the service model, with margin.
• Per-pin current and the power strategy — signal contacts are not power contacts; families offer dedicated power pins or you allocate (and derate) groups per the datasheet.
• Tolerance stack — PCB thickness, standoff length, connector height, and coplanarity across both boards must close so the pair neither bottoms out nor barely wipes.
• Vibration and the support plan — standoffs/rails/wedge-locks sized so the connector carries signals, not structure.
• Signal-integrity boundary — fast lanes (high-speed serial, RF on board) need the family's impedance-controlled variants and the manufacturer's SI data; that's your cue that "basic" is over.

Parts people forget

• Standoffs and their screws — they are part of the interface, not shop supplies; put the length and torque on the drawing.
• Both halves, as a pair — header and receptacle, same series, same height code, on the BOM together.
• Guide pins / chamfered leads where assembly is blind.
• Board keep-outs and land patterns per the manufacturer drawing — including keep-outs under the mated connector on both boards.
• Spares for fine-pitch parts during development — rework kills them faster than service does.

See What People Forget.

Common traps

• The connector as the only mechanical support. It will work on the bench and fret, fatigue, or crack solder joints in the field. Standoffs first, connector second.
• Two catalogs, one wrong height. Mixed mated heights across "the same" family is the classic board-respin discovery.
• Unpolarized stacks assembled offset or reversed — the Dupont trap at board scale; keying or asymmetric mounting prevents it.
• Card-edge cycles assumed free. The mating half is plated fingers; plating spec, bevel, and cycle expectations belong in the design, not in hope.
• Tolerance stack never closed. Coplanarity and standoff math decide whether fine-pitch contacts actually wipe; the datasheet's tolerance section is load-bearing reading.
• Treating a stack joint as a service disconnect. Low-cycle families in a pull-it-weekly role wear out early — see the service-model logic in §1.

Questions to ask a vendor/FAE

• Which part-number pair gives my required mated height, and what is the height tolerance?
• What is the effective wipe length at worst-case tolerance stack, and the recommended coplanarity budget?
• What are the mating-cycle rating and the per-pin current at my loaded-contact count and temperature?
• What alignment capture range does the family provide, and are guide hardware or polarization options available?
• For fast lanes: is there an impedance-controlled variant, and where is the SI documentation?

Example documentation bundle

• A comparison-matrix row: requirement, candidate families, choice.
• An assembly drawing calling out both connector P/Ns, the mated stack height, standoff length/torque, and guide hardware.
• An ICD entry for the board interface: pinout, power-pin allocation, keep-outs, mate/unmate procedure, cycle budget.
• A design-review pass covering the tolerance stack and the mechanical-support plan.

Related: Internal PCB harnessing (the wire alternative) · Micro-D / compact high-rel · Connector Anatomy (§5) · Major Connector Categories (§2) · Identification Workflow.