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 typically ship in 1–2 days after design file submission. 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