Automotive PCBA in Vietnam: How SHDC Uses AOI, ICT and FCT for Assembly Verification

An automotive printed circuit board assembly can appear visually correct while still containing an electrical open, an incorrect component value or a functional problem that only becomes visible after power-up. Conversely, a board may complete a basic functional test even though it contains a placement or soldering condition that should have been identified earlier in production. For this reason, verifying an automotive PCBA in Vietnam should not depend on a single inspection method. A stronger test strategy combines three different layers:

Automated optical inspection, or AOI, for visible assembly conditions.
In-circuit testing, or ICT, for circuit-level electrical verification.
Functional circuit testing, or FCT, for product-specific operation.

SHDC’s company profile lists a Yamaha YSi-V 3D AOI system, a Kyoritsu ICT F-2000 Plus and functional-testing equipment. Its documented production flow also places AOI, ICT and FCT before outgoing quality control and final packaging. The exact inspection and test route, however, must be defined for each product rather than assumed to be identical for every assembly.

This guide explains what each method can detect, where its limitations begin and what US automotive OEMs should provide when developing a PCBA verification plan with SHDC.

Main content

What Does Assembly Verification Mean for Automotive PCBA?

Assembly verification is the structured process of confirming that a PCBA has been built according to its design data and performs according to its approved functional requirements.

It includes three related but different activities.

Inspection evaluates physical assembly conditions such as component presence, orientation, position and visible solder-joint quality.

Electrical testing checks whether circuit connections and selected components behave as expected.

Functional testing determines whether the powered assembly carries out its intended operation under customer-defined conditions.

These activities should not be treated as interchangeable. IPC J-STD-001J covers materials, methods and process requirements for soldered assemblies, while IPC-A-610J provides post-assembly visual acceptance requirements. IPC released the current “J” revisions in 2024 and recommends using the documents together where applicable.

For a broader discussion of process controls surrounding these tests, see SHDC’s PCB assembly quality control plan.

Manufacturing Defects and Functional Failures Are Different

Common manufacturing defects include:

Missing or misplaced components
Incorrect polarity
Solder bridges
Open solder joints
Insufficient solder
Wrong component values
Incomplete through-hole soldering
Damaged or lifted leads

Functional failures may include:

Incorrect power-up behavior
Output voltage outside the specified range
Communication failure
Sensor inputs not responding correctly
Relay or actuator outputs not operating
Firmware not interacting correctly with the hardware
Excessive current consumption
Incorrect sleep or wake-up behavior

A visual system may detect the first group but cannot fully verify the second. An electrical test may identify an open net but may not confirm the complete operating sequence of the product. That is why effective automotive PCBA verification uses several test gates.

SHDC’s AOI, ICT and FCT Process at a Glance

Verification stage	Primary question	Typical scope	Equipment shown in SHDC profile
AOI	Was the board assembled visibly as intended?	Component presence, orientation, position and visible solder conditions	Yamaha YSi-V 3D AOI
ICT	Is the circuit electrically assembled as designed?	Opens, shorts, connectivity and selected component values	Kyoritsu ICT F-2000 Plus
FCT	Does the assembly perform its intended functions?	Power, inputs, outputs, interfaces and customer-defined operations	Functional-testing equipment
Additional testing	Does the product meet special electrical or operating requirements?	High-voltage, aging or application-specific checks	Equipment shown in SHDC profile

The SHDC process diagram shows AOI after reflow, followed by repair where required. ICT and FCT appear later in the production route, before OQC, packaging and finished-product storage. The equipment portfolio also includes high-voltage and aging-test equipment.

This confirms that SHDC has multiple inspection and testing resources. It does not mean every board automatically receives all listed tests. Test coverage, limits, frequency and data-retention requirements must be agreed during project review.

AOI for Automotive PCBA Assembly Verification

Automated optical inspection uses cameras, lighting and programmed inspection criteria to compare an assembled board with the expected component and soldering conditions.

AOI is normally positioned after SMT reflow because this allows the system to examine both component placement and visible solder-joint formation.

What AOI Can Inspect

Depending on the component package, image quality and inspection program, AOI may detect:

Missing components
Incorrect polarity or orientation
Component rotation
Placement offset
Lifted leads
Visible solder bridges
Certain insufficient or excessive solder conditions
Incorrect markings when visually distinguishable
Components that are not seated correctly

The Yamaha YSi-V listed in SHDC’s profile combines two-dimensional inspection, three-dimensional inspection and four-direction oblique imaging in one platform. Angled imaging can provide additional views around component bodies and leaded packages that may be difficult to assess from a top-down image alone. (Yamaha Motor Global Site)

SHDC provides a more detailed explanation of automated optical inspection in PCB assembly.

AOI Programming Matters as Much as the Machine

Installing an AOI system does not automatically guarantee effective defect detection. A usable inspection program requires:

A correct component library.
Defined inspection regions.
Polarity and marking references.
Appropriate height and position limits.
First-article verification.
Review of false calls.
Revision control when the BOM or PCB changes.

If thresholds are too broad, real defects may escape. If they are too narrow, the system may generate excessive false failures and slow production.

For automotive-related projects, the OEM should identify critical components, polarity-sensitive devices and solder joints that require particular attention.

What AOI Cannot Confirm

AOI cannot fully verify:

Electrical continuity
Resistance or capacitance values
Firmware operation
Communication protocols
Product operating sequences
Intermittent electrical faults
Internal BGA solder connections without additional inspection
Long-term product reliability

IPC-A-610J is a collection of visual acceptability requirements and does not provide criteria for X-ray or cross-section evaluation. An AOI pass should therefore not be interpreted as proof that the PCBA is electrically and functionally complete. (electronics.org)

AOI Defect Review and Repair

AOI results should enter a controlled review loop:

The system flags a suspected condition.
An operator or technician distinguishes a genuine defect from a false call.
Confirmed defects are categorized.
The board is transferred to controlled repair when allowed.
The repaired area is reinspected and retested according to the work instruction.
Defect data is reviewed for recurring process trends.

A defect Pareto can help identify whether failures originate primarily from solder paste printing, placement, reflow, component handling or inspection-program settings. Common defect mechanisms are discussed further in SHDC’s guide to common PCB assembly defects.

ICT for Circuit-Level Electrical Verification

In-circuit testing uses electrical probes or a dedicated fixture to access points on the assembled PCB.

Depending on the board design and test program, ICT can evaluate:

Open circuits
Short circuits
Continuity
Resistor and capacitor values
Diode orientation
Basic semiconductor junctions
Power and ground conditions
Missing or incorrect components that create measurable electrical differences

Keysight describes ICT as a method for measuring electrical properties such as resistance, capacitance and voltage at specific PCB nodes. These measurements help identify opens, shorts and incorrect component values.

SHDC’s equipment profile lists the Kyoritsu ICT F-2000 Plus. The profile does not state a universal fault-coverage percentage, fixture configuration or test-node capacity, so these details should be confirmed for each project.

Why ICT Supports Faster Fault Isolation

Suppose a board fails FCT because it does not power up.

FCT confirms that the product does not work, but it may not immediately show why. ICT can help isolate the underlying cause, such as:

A short between the power and ground nets
An open connection
A reversed diode
An incorrect resistor value
A missing component
An assembly fault at a measurable node

This diagnostic capability can reduce troubleshooting time and improve feedback to the assembly process.

ICT Depends on Design for Testability

ICT requires physical and electrical access. Test points should be incorporated before the PCB layout is released.

Relevant design considerations include:

Test-point access to critical nets
Sufficient pad size
Probe spacing
Access from one or both sides
Stable ground references
Board support to prevent flex
Clearance around tall components
Fixture alignment features
Programming and power-injection points

Keysight notes that custom fixtures are normally required for each PCB layout and that good design for test can improve access while reducing fixture complexity.

OEMs should therefore complete a design for testability review before finalizing the PCB.

ICT Limitations

ICT does not normally verify the complete operating behavior of a product.

Its limitations may include:

Reduced coverage when test access is limited
Difficulty accessing dense packages or hidden nodes
Fixture development cost
Program-debug time
Limited firmware verification
Inability to simulate the complete operating environment

For low-volume projects, the value of a dedicated ICT fixture must be weighed against tooling cost and expected fault coverage.

FCT for Product-Specific Performance Verification

Functional circuit testing powers or stimulates the PCBA and observes whether it performs according to the approved product specification.

Unlike AOI and ICT, FCT is highly application-specific.

A functional test may verify:

Input voltage and current
Power-up sequence
Output voltage or current
Sensor inputs
Relay or actuator outputs
Analog and digital signals
Communication interfaces
Firmware and hardware interaction
Fault-response behavior
Product-specific operating modes

NI describes functional testing as verifying the operation of the combined system of components, commonly at one or more points in production and at the end of the manufacturing line.

For more detail on their different purposes, see SHDC’s comparison of ICT vs. functional testing.

The OEM Must Define the Functional Requirements

An automotive FCT program cannot be built from the PCB files alone.

The OEM may need to provide:

Schematic
Connector pinout
Permitted input-voltage range
Expected current consumption
Input stimuli
Expected outputs
Timing limits
Firmware
Programming procedure
Communication protocol
Load conditions
Fault-response criteria
Pass/fail tolerances

Depending on the product, the test plan might include CAN, LIN, analog-sensor simulation, ignition states, load simulation or sleep and wake-up behavior. These are examples of possible automotive requirements; SHDC’s profile does not confirm that every protocol or interface is already supported.

Golden Samples and Test Limits

An approved reference assembly can help correlate a newly developed FCT fixture, but a golden sample should not replace an engineering specification.

The test program should include:

Nominal values
Upper and lower limits
Measurement uncertainty
Time-based conditions
Fixture identification
Instrument calibration
Firmware revision
Test-program revision

Limits that are too broad can permit escapes. Limits that are too narrow can create false failures and unnecessary retesting.

AOI vs. ICT vs. FCT

Criteria	AOI	ICT	FCT
Main purpose	Visual assembly verification	Circuit-level electrical verification	Product-function verification
Typical production stage	After reflow or soldering	After assembly	Near the end of the process
Powered board required	Usually no	Depends on the test	Usually yes
Detects missing components	Yes, when visible and programmed	Sometimes electrically	Sometimes through functional failure
Detects visible solder bridges	Yes	Detects resulting short	May detect resulting malfunction
Measures component values	Generally no	Selected components	Usually only indirectly
Verifies firmware	No	Usually no	Yes, when included in test scope
Dedicated fixture	Not normally an ICT fixture	Usually required	Usually required
Main limitation	Cannot prove electrical function	Limited by test access	May not isolate root cause efficiently

A practical way to understand the difference is:

AOI asks whether the board was assembled visibly as intended. ICT asks whether the circuit is electrically connected as expected. FCT asks whether the product works as intended.

How AOI, ICT and FCT Work Together

A layered verification strategy creates several defect-containment gates.

Gate 1: AOI Detects Visible Assembly Errors

Detecting a reversed diode or missing component immediately after reflow is generally more efficient than discovering it during a later electrical or functional test.

Gate 2: ICT Isolates Circuit-Level Faults

ICT can identify an open, short or incorrect component value before the board enters a longer functional sequence.

Gate 3: FCT Confirms Intended Operation

FCT checks product behaviors that cannot be confirmed through images or isolated component measurements.

Consider three examples:

Reversed diode: AOI may detect the polarity error, ICT may confirm the abnormal junction condition and FCT may show that the board cannot operate.

Hidden open connection: AOI may pass the board, ICT may identify the open net and FCT may only report a broader functional failure.

Incorrect firmware: AOI and ICT may both pass, while FCT detects incorrect communication or operating behavior.

No combination delivers automatic 100% fault coverage. The remaining risk depends on PCB design, component accessibility, inspection algorithms, fixture design, test limits and process maintenance. Keysight recommends combining ICT with complementary visual and functional methods to address coverage gaps.

From Pilot Build to Automotive Production Approval

AOI, ICT and FCT should be developed and validated during the pilot-build stage rather than first introduced at mass production.

Activities may include:

Debugging AOI inspection regions
Reviewing false calls
Validating ICT probe contact
Correlating fixture measurements
Confirming FCT sequences
Establishing pass/fail limits
Measuring test-cycle time
Reviewing first-pass yield
Investigating no-fault-found results
Confirming repaired-board retest requirements

SHDC’s article on production validation testing provides additional context for confirming manufacturing readiness before volume production.

Automotive Documentation Context

When required by the customer, inspection and test records may support:

Control plans
Pilot-build reports
Failure Pareto analysis
Fixture-validation records
Calibration records
First-pass yield reporting
Rework documentation
Production-part approval evidence

AIAG’s current quality-core-tool resources include APQP 3rd Edition and the standalone Control Plan 1st Edition. The updated guidance includes topics such as sourcing, change management, traceability, risk mitigation and gated program management.

Automotive requirements must also be reviewed against the actual customer. The IATF maintains separate customer-specific requirements for individual OEMs, and these documents can change over time.

SHDC’s Supporting Assembly and Test Infrastructure

SHDC states that its EMS scope extends from component soldering, assembly and testing through final packaging.

Its current company profile lists:

Four high-speed SMT lines
Three DIP lines
One assembly line
One test line
One packaging line
Yamaha YSi-V 3D AOI
Kyoritsu ICT F-2000 Plus
Functional-testing equipment
High-voltage testing
Aging testing
OQC and final packaging

The profile also shows QC, production and engineering functions within the organization and a production-management architecture connecting printing, SPI, placement, AOI, data and repair stations.

These facts support discussion of SHDC’s assembly and testing infrastructure. They do not by themselves establish:

IATF 16949 certification
A universal automotive control plan
100% AOI, ICT and FCT on every PCBA
Specific CAN or LIN test capability
X-ray inspection capability
Guaranteed fault-coverage percentages
Full serial-level test-data traceability

Those requirements should be confirmed during technical and commercial review.

For a wider overview of automotive manufacturing considerations, see automotive PCB assembly in Vietnam for US OEMs.

What US OEMs Should Provide to SHDC

A complete automotive PCBA test package should contain:

Manufacturing data

Gerber or ODB++ files
BOM with manufacturer part numbers
Pick-and-place data
Assembly drawings
Schematic
PCB specifications
Approved alternates

AOI requirements

Polarity references
Critical-component list
Marking variations
Visual acceptance criteria
Special solder-joint requirements

ICT requirements

Netlist
Test-point data
Expected component values
Coverage targets
Retest rules
Fixture-ownership requirements

FCT requirements

Connector pinout
Power conditions
Input stimuli
Expected outputs
Timing requirements
Firmware and programming files
Communication requirements
Pass/fail limits

Quality requirements

Product and test-program revision control
Data-retention period
Serial or lot traceability
Calibration requirements
Rework and retest procedure
Customer-specific submission requirements
Change-notification rules

SHDC’s PCBA manufacturer Vietnam RFQ checklist provides a broader list of information needed for technical review and quotation.

Automotive PCBA Verification Checklist

Before releasing a project into production, confirm that:

Critical defect types have been identified.
AOI coverage and limitations are documented.
ICT test points are available.
Fixture ownership and maintenance are agreed.
FCT inputs, outputs and timing limits are defined.
Firmware revisions are controlled.
Golden samples are approved and identified.
Pass/fail limits come from engineering specifications.
Retest and repair rules are documented.
Repaired boards receive appropriate reinspection.
Test equipment calibration is current.
Test-program revisions are controlled.
Required test records can be linked to the production lot or serial number.
Pilot-build results are approved before mass production.
Customer-specific automotive requirements have been reviewed.

Conclusion

Effective verification of an automotive PCBA in Vietnam requires more than checking whether the board looks correct or powers on.

AOI, ICT and FCT address different risks:

AOI identifies visible placement and soldering conditions.
ICT checks circuit connectivity and selected component-level characteristics.
FCT confirms customer-defined operating behavior.

The value of these methods depends not only on the equipment but also on design for testability, program development, fixture control, pass/fail limits, calibration and test-data management.

SHDC’s company profile confirms the presence of AOI, ICT and functional-testing equipment within its broader PCBA production process. For a specific automotive program, the OEM and SHDC should agree on the inspection route, test coverage, documentation and approval requirements before the pilot build begins.

Frequently Asked Questions About Automotive PCBA Testing

Is AOI enough for automotive PCBA verification?

No. AOI evaluates visible assembly conditions but does not fully verify electrical integrity, firmware or product function. ICT and FCT may be required depending on the product risk and customer specification.

What is the difference between AOI, ICT and FCT?

AOI checks visible assembly conditions. ICT measures circuit connections and selected components. FCT powers or stimulates the board to confirm that it performs its intended functions.

Does every automotive PCBA need all three tests?

Not automatically. The required test route depends on PCB design, production volume, failure risks, test access and customer-specific requirements.

Can AOI inspect BGA solder joints?

Conventional AOI cannot fully examine hidden solder joints under a BGA. X-ray or other methods may be required when the product risk justifies them.

What defects can ICT detect?

Depending on the fixture and program, ICT can detect opens, shorts, connectivity problems, selected incorrect component values and certain polarity or junction faults.

What does FCT test?

FCT may check power-up behavior, current consumption, inputs, outputs, communication, firmware interaction and other product-specific operating modes.

Why is design for testability important?

DFT creates the physical and electrical access required by ICT and FCT. It can improve fault coverage, simplify fixtures and reduce troubleshooting time.

Can SHDC provide automotive PCBA testing?

SHDC’s profile shows 3D AOI, Kyoritsu ICT F-2000 Plus and functional-testing equipment. The exact automotive test scope, coverage and reporting requirements must be confirmed for each project.