An exchangeable cartridge is the part of a bed-of-nails test fixture that holds probes and receptacles for a specific PCBA. When your board design changes or you need to test a different product, you swap the cartridge instead of replacing the entire fixture. The base — with its actuation mechanism, structural frame, and feedthrough plates — stays the same.
This is how a single test station handles multiple products without multiplying fixture costs.
How Exchangeable Cartridges Work#
The cartridge seats into the fixture base and aligns via guide pins. Depending on the fixture tier, it secures with latches (production) or corner fasteners (development).
Inside the cartridge: pogo pin probes pressed into receptacles, arranged to match your board's test point layout. The probe plate and pressure plate are specific to the PCBA under test. Everything else — the base frame, actuation mechanism, feedthrough plate, and any wiring to instrumentation — belongs to the base and stays put.
To swap cartridges: release the fasteners or latches, lift out the current cartridge, drop in the new one, and re-secure. On a Dev Pro, this takes under a minute. On a production Ingun fixture, the cartridge locks into the base frame via precision guide pins for repeatable alignment across millions of cycles.
When to Use Exchangeable Cartridges#
You benefit from exchangeable cartridges when:
- Multiple PCBA variants share a test station. One base, one set of instrumentation wiring, multiple cartridges — one per board design. A modular test fixture pays for itself when you're running even two or three board variants.
- Board revisions happen regularly. New revision means a new cartridge, not a new fixture. Your existing base, feedthrough plate, and wiring stay in service.
- You run a multi-product test cell. Service providers testing boards for multiple clients can share fixture bases across programs. One PCBA test fixture base, many cartridges.
- High-volume production wears out probes. Swap in a fresh cartridge while the worn one gets refurbished. No station downtime.
For single-product applications with no anticipated variants, a standard non-exchangeable fixture may be simpler. The Dev is built for this — low cost, fast turnaround, no cartridge mechanism to maintain.
Cartridge Options by Fixture Tier#
| Tier | Cartridge Type | Probe Plate Material | Cycle Life | Exchangeable? |
|---|---|---|---|---|
| Dev | Fixed probe plate | MDF or G10 | ~1,000 cycles | No |
| Dev Pro | Probe plate + pressure plate | MDF or TPCB (test point contact board) | 5,000–10,000 cycles | Yes — four corner fasteners |
| Production | Ingun test fixture cartridge | FR4 (fiberglass) | Millions of cycles | Yes — precision guide pin alignment |
For specific cartridge models, dimensions, and cycle life ratings, see the cartridges catalog.
Production Cartridge Variants#
FixturFab partners with Ingun for production-grade cartridges. Three variants cover different testing environments:
- Standard cartridges — for most production test applications
- ESD protection cartridges — for sensitive DUTs or integration with automated test equipment
- RF-shielded cartridges — for RF-sensitive testing environments
FixturFab can also source and customize specialized cartridges beyond Ingun's standard ATS line.
Development Cartridge Options#
The Dev Pro supports two probe plate configurations:
- MDF probe plate — direct wiring from probes to instrumentation. Used for most development applications.
- TPCB probe plate stack-up — routes test point signals through a PCB directly to feedthrough connectors on the back of the fixture. Cleaner wiring, faster setup.
Standard Dev fixtures use fixed probe plates — no cartridge exchange — because their fabrication cost is low enough that ordering a new fixture per board design is practical.
Cost and Lifecycle Benefits#
The first cartridge for a fixture base includes full design work: probe layout, plate fabrication, receptacle selection. After that, replica cartridges for the same PCBA skip the design step entirely. You get the same cartridge at a lower price with a shorter lead time.
When your board design changes, a new cartridge costs less than a new fixture because the base doesn't need to be re-manufactured. Your design files are saved in Studio — reordering a replica or configuring a cartridge for a new board revision starts from your existing fixture base configuration.
Over the life of a product line, this adds up. A single Dev Pro base might serve three or four board revisions. A production base might run for years, with cartridges swapped for new products, worn probes replaced, or ESD/RF variants rotated in as testing requirements change.
Ordering Additional Cartridges#
To order a new or replica cartridge:
- Open your fixture configuration in Studio
- Select the existing fixture base
- Upload updated Gerber files (for a new board design) or select "replica" (for an identical cartridge)
- Review and submit the order
FixturFab handles probe selection, plate fabrication, and assembly. Dev Pro cartridge replacements have a short turnaround since the base fixture already exists — submit your design files and we'll confirm the timeline. Production cartridge lead times vary by complexity.
Related Documentation#
- Cartridges — specific models, materials, dimensions, and cycle life ratings
- Fixture Bases — base specifications and compatibility
- Fixture Types — Dev vs. Dev Pro vs. Production comparison
- Signal Interfaces — hand-wired vs. Auto TPCB vs. Consigned TPCB
- Feedthrough Plates — connector panel customization