01
Requirements and acceptance plan
Action: map functions, stimuli, loads, firmware, limits, and required records. Risk: testing an assumed behavior or undefined range. Evidence: approved test-plan revision and open-question closure.
Functional Test Service
PCBA Functional Test (FCT) Services
Confirm what will be powered, stimulated, measured, and recorded before the fixture is released. APTPCB builds the FCT setup around your approved firmware, loads, interfaces, limits, and production acceptance criteria.
Defined inputs
Power, signals, loads, and firmware
Pilot validation
Limits and reference behavior approved
Release records
Evidence agreed for the order
Get an Instant Quote
Functional test
What Is Functional Circuit Test (FCT)?
| Question | Answer |
|---|---|
| What is functional circuit test? | Functional circuit test (FCT) powers an assembled board and checks that it behaves as designed — firmware boots, interfaces communicate, sensors read within range and outputs drive their loads. |
| How is FCT different from ICT? | ICT checks components and nets while the board is unpowered and probe-accessible. FCT checks the working product, so it catches firmware, timing and system-level faults that ICT cannot reach. |
| When does FCT earn its cost? | When a board must be proven functional before shipment, when downstream assembly cost makes a late failure expensive, or when the product is safety- or mission-relevant. |
Coverage matrix
What Does PCBA Functional Testing Cover?
The released product requirements define the checks and limits. This matrix shows the information needed to turn a function into a repeatable production test.
| Product function | Typical FCT checks | Customer baseline | Possible result record |
|---|---|---|---|
| Power and startup | Rail presence, sequencing, reset, boot, inrush, and steady-state current | Nominal rails, timing, load state, and acceptance limits | Pass/fail, measured voltage or current, and failed step |
| Digital control and firmware | Firmware identity, boot state, GPIO, modes, commands, and fallback behavior | Approved image, programming method, expected states, and version rule | Firmware version, state result, error code, or response |
| Communication interfaces | UART, RS-232/485, I2C, SPI, CAN, LIN, USB, or Ethernet exchange where applicable | Protocol, command set, peer device, test data, termination, and timeout limits | Link status, response, data check, timeout, or failed transaction |
| Analogue and sensor paths | Stimulus, ADC reading, reference voltage, gain, offset, and range response | Stimulus source, calibration basis, test points, tolerance, and environment | Measured value, limit, channel, and pass/fail result |
| Outputs and loads | Relay, MOSFET, motor, fan, LED, display, buzzer, and other output behavior | Load or simulator, drive sequence, duration, expected output, and safe limits | Output state, measured level, timing, current, or failed step |
| User I/O and interlocks | Buttons, indicators, connectors, enable lines, and defined safety interlocks | Input sequence, expected feedback, fixture access, and acceptance criteria | Sequence status, response, operator prompt, or exception code |
A listed interface or function is not automatic coverage. Confirm the fixture, stimuli, peer devices, firmware, limits, sampling, and report fields for the actual order.
Engineering review to production release
When Is a Functional Test Fixture Worth Building?
Each gate closes a source of false rejects, missed failures, or untraceable results before the setup is used in volume production.
02
Fixture and golden-board baseline
Action: define stable power, ground, connectors, test access, loads, simulators, and the golden board or approved reference behavior. Risk: contact, reference, or setup variation being mistaken for board failure. Evidence: fixture definition and reference approval. The fixture is designed, machined and assembled in-house rather than subcontracted.
03
Test software and result handling
Action: implement power-up, commands, measurements, comparisons, error codes, and result storage. Risk: an unversioned program or opaque pass/fail decision. Evidence: released software version and result-field definition.
04
Pilot validation and limit tuning
Action: run representative boards, challenge known conditions, and review timing and thresholds. Risk: false rejects, escapes, or a cycle that does not match production handling. Evidence: pilot results, approved limits, and exception disposition.
05
Production release and change control
Action: release the fixture, program, work instruction, reference, and retest flow under revision control. Risk: firmware, fixture, or criteria changing without synchronized approval. Evidence: released baseline and board- or lot-linked results as ordered.
In-house fixture and test program
Who Builds the FCT Fixture and Test Program?
APTPCB designs, machines and assembles the FCT fixture in-house and develops the matching test program, so fixture geometry, probe selection, program logic and acceptance limits stay under one revision-control process. The customer approves coverage, limits and reference behavior before the setup is released.
| Stage | APTPCB (in-house) | Customer | Evidence released |
|---|---|---|---|
| Requirements | Map functions, stimuli, loads, interfaces and required records to a test plan | Provide functional specification, expected outputs and limits | Approved test-plan revision |
| Fixture design | Mechanical and electrical fixture design, probe and connector selection, strain relief and access strategy | Confirm board orientation, connector definitions and handling constraints | Released fixture drawing and wiring schedule |
| Fabrication and assembly | Machine and assemble the fixture in-house; verify contact force, alignment and connector keying before the first board is loaded | Approve any deviation from the agreed fixture concept | Fixture build record and pre-load check |
| Test program | Develop power-up, stimulus, measurement, comparison and error-code logic, and define result storage | Supply the approved firmware image and programming method | Released program version tied to a firmware revision |
| Golden board baseline | Check the fixture against known-good behavior and tune timing and thresholds | Provide a golden board where available, or approve reference behavior in writing | Pilot results and limit justification |
| Release and change | Release fixture, program and work instruction under revision control | Approve coverage, limits and any later change | Production release package |
Where a fixture is customer-supplied or a legacy jig is reused, the same table applies — the responsible party changes, and that change is recorded in the quotation rather than assumed.
Behavioral failures
Which Defects Can FCT Catch After Assembly?
FCT complements inspection and node-level electrical tests by observing powered behavior under the approved test conditions.
Startup
Power is present, but the board does not boot
A reset, sequencing, firmware, clock, current, or initialization problem can remain after visual inspection and continuity checks.
Communication
The interface connects, but transactions fail
Protocol response, timing, termination, firmware state, peer-device behavior, or data integrity can be checked against a defined exchange.
Loads and outputs
An output changes state but cannot drive the required load
The fixture can apply the approved load or simulator and evaluate output level, current, sequence, or response within stated limits.
Analogue behavior
Sensor or measurement channels respond outside range
Known stimuli can expose offset, gain, reference, channel, conversion, or firmware-scaling errors that are not visible in an unpowered check.
Test-method selection
PCB Functional Test vs ICT: Which Do You Need?
These methods are complementary. A production plan can combine them when defect screening, hidden-joint inspection, node access, and powered behavior all matter.
| Method | What it primarily checks | Important boundary | Typical role |
|---|---|---|---|
| AOI | Visible component presence, polarity, placement, solder, and workmanship features | Cannot prove hidden joints or product function | In-line assembly inspection before later electrical or functional tests |
| X-ray inspection | Hidden solder-joint and internal assembly features within the defined inspection scope | An image does not prove circuit behavior | Inspection of BGA, QFN, bottom-terminated, or otherwise hidden features |
| ICT or flying probe | Accessible nets, continuity, shorts, and selected component relationships | Coverage depends on test access and does not replace powered product behavior | Electrical assembly-defect screening before or alongside FCT |
| FCT | Powered response to approved stimuli, loads, firmware, interfaces, and sequences | Only the released test plan, conditions, and limits are verified | Product-specific behavior verification and production release evidence |
Use the PCBA testing and quality hub to map inspection and test layers to design access, production volume, failure risk, and required evidence.
Functional test planning
PCBA Functional Testing Service: Questions Before RFQ
What information is needed to quote PCBA functional testing?
Send the available Gerber data, BOM, schematic, connector and test-point details, firmware package, functional specification, expected stimuli and outputs, acceptance limits, target quantity, and required report fields. APTPCB uses this package to confirm practical coverage, fixture scope, pilot validation, and quote assumptions.
Does every FCT program require a golden board?
A known-good golden board is useful for fixture checkout and comparison, but the controlling baseline should be the approved functional specification, limits, firmware version, and expected behavior. If no golden board is available, the reference and approval method must be agreed before production release.
Can APTPCB develop the FCT fixture and test program?
Yes. APTPCB designs, machines and assembles the FCT fixture in-house and develops the matching test program, then validates the setup against a golden board or approved reference behavior. Work starts from an approved test plan covering fixture connections, power, loads, simulators, communication interfaces, software steps and result handling. The customer approves the coverage, limits, reference behavior and acceptance criteria before the production test is released. Where a fixture is customer-supplied, we build the program and validation around the existing jig.
Can the same FCT setup support prototypes and volume production?
The test intent can remain consistent, but prototype setups may use more manual access while production fixtures prioritize repeatability, operator handling, cycle time, error isolation, and result storage. A pilot run confirms the released setup before volume use.
Do I need FCT if the assembly already has ICT?
ICT and FCT answer different questions. ICT checks accessible electrical nodes and component relationships, while FCT powers and stimulates the board to verify defined product behavior. Programs can use both when assembly-defect screening and functional verification are required.
What records can be delivered with FCT?
The agreed record set can include pass or fail status, board serial number or lot, test date, failed step or error code, measured values and limits for parametric checks, and repair or retest disposition. Availability and retention are defined for the order.
Does an FCT pass replace product qualification or certification?
No. FCT verifies the functions and limits included in the approved production test plan. It does not replace system-level qualification, regulatory testing, environmental validation, or safety certification unless a specific approved requirement is explicitly included in the order.
Is the functional test fixture built in-house or subcontracted?
The fixture is designed, machined and assembled in-house, and the test program is developed by the same team. That keeps fixture geometry, probe selection, program logic and acceptance limits under one revision-control process, which matters when a firmware change or board revision requires the fixture and program to be re-validated together. If you already own a fixture, we can program and validate against it instead.
Records and RFQ closure
What Should an FCT Test Report Contain?
A pass label without a controlled baseline or useful failure detail is weak production evidence. Agree the identity, fields, limits, retention, and disposition flow needed by engineering, quality, and procurement.
RFQ inputs
Send the design revision, schematic, BOM, connector and test-point details, firmware image and programming method, functional specification, stimuli, expected outputs, limits, loads or simulators, golden-board status, quantity, serialization method, and required report fields.
Qualification boundary
FCT verifies only the approved production test plan. It does not replace system-level qualification, environmental validation, regulatory testing, or safety certification unless a specific approved requirement is included in the order.
| Record field | Purpose |
|---|---|
| Board or lot identity | Connect the result to the agreed serial number or lot method |
| Test date and revision | Identify when the test ran and which released program or plan applied |
| Pass/fail and failed step | Show the disposition and isolate the point of failure |
| Measured value and limit | Retain parametric evidence where the approved test records it |
| Repair and retest status | Close the nonconforming-board flow under the order procedure |
Record availability, format, sampling, and retention depend on the released test plan and order.
Before tooling approval
Confirm fixture ownership, maintenance, spare strategy, expected volume, cycle-time target, firmware control, reference method, report format, and the approval path for changes.
Get an FCT coverage and fixture review
Send the available schematic, BOM, firmware, functional specification, expected loads, acceptance limits, golden-board status, and reporting needs. We will confirm practical coverage and quote assumptions before tooling release.