Test fixtures and bring-up jigs
A board you cannot test repeatably is a board you cannot manufacture repeatably.
Design for test is one of those disciplines that costs almost nothing at schematic stage and becomes impossible afterwards.
By the time a board is laid out, whether it can be tested repeatably is already decided — by where the test points are, what the boundary-scan chain covers, and whether the interesting signals reach anywhere a probe can land.
Two different jobs
A bring-up jig serves one engineer investigating one board. Current-limited supply, instrumentation attached, easy access to every rail and strap, and safe to leave powered on a bench while you think. It optimises for visibility.
A production fixture serves an operator who needs a repeatable answer in seconds, with no judgment required. It optimises for speed, repeatability, and pass criteria that cannot be argued with.
They are different objects. Building one and hoping it does both produces something that does neither.
What has to be decided on the product board
| Decision | Consequence if skipped |
|---|---|
| Test point placement and size | The signal you most need is unreachable |
| Probe access clearances | The fixture cannot physically reach past a tall component |
| Boundary-scan coverage | No way to verify interconnect on a solder-down assembly |
| Rail isolation | A short cannot be localised without cutting tracks |
| Fiducials and tooling holes | Fixture alignment is by eye, so results are not repeatable |
| Programming and debug access | Production programming needs a jig nobody designed |
Every one of these is free to include while the layout is open, and expensive to retrofit.
Solder-down modules change the picture
On a design where a module is reflowed onto a carrier, the two cannot be separated to isolate a fault. That raises the value of test-point coverage and boundary-scan access considerably, and it is a reason the test strategy has to be settled before the module standard is chosen — not after.
Truthful scope
In-house: test strategy, fixture PCB design, fixture mechanics in engineering polymers on our own machines, and bring-up jigs we use ourselves.
Through partners or your line: in-circuit test programming, the ICT machine, and volume fixture manufacture. We make sure the board presents the right test surface for whoever runs it.
Fixture designs and documentation transfer with the product, in native format and under EU jurisdiction — including to a contract manufacturer you choose later.
Common questions
Straight answers
When should the test fixture be designed?
Alongside the product board, not after it. Test point placement, probe access, boundary-scan availability and whether a solder-down module can be isolated are all product-board decisions. Designing the fixture afterwards means discovering that the signal you most need to measure has no accessible landing point.
What is the difference between a bring-up jig and a production fixture?
A bring-up jig exists to let one engineer investigate — power, instrumentation, easy access, safe to leave running. A production fixture exists to let an operator get a repeatable pass or fail in seconds, with no judgment required. Different goals, different mechanics, and conflating them produces something that does neither well.
Do you do bed-of-nails fixtures?
We design the fixture PCB, the probe map and the mechanics, and work with your assembler on the build. Full in-circuit test programming and the ICT machine itself belong with whoever runs the line — we make sure the board presents the right test surface for it.
What makes a good end-of-line test?
It fails for reasons that map to a repair action. A test that reports 'FAIL' teaches nobody anything; one that reports which rail was out of tolerance sends the board to the right bench. Designing pass criteria that carry diagnostic information is the part that gets skipped and then regretted.
Is this worth it at low volume?
Below a few dozen units, often not — a documented manual procedure is cheaper and more flexible. The crossover comes when the cost of an escaped defect, or the time an engineer spends repeating the same checks, exceeds the fixture. We will tell you which side of that line you are on rather than selling you a fixture you do not need.
Evidence
Where this has been applied
Competition robot: designing for repeated high-energy impact
A reliability testbed that punishes every shortcut — and where a destroyed capacitor turned into a transient-survivability design rule.
Flight-controller carrier for a tube-launched UAV
Teardown, clean-room re-implementation, and a rigid-flex carrier that fits inside a launch tube.