PCB Assembly Process in Taiwan | From DFM to Production 

11. X-Ray Inspection for Hidden Solder Joints

X-ray inspection can be used where solder joints cannot be adequately evaluated by visual inspection or AOI.

Typical applications include:

• BGA

• QFN

• LGA

• Bottom-terminated components

• Other assemblies with hidden solder joints

Depending on the package and inspection requirements, X-ray can help evaluate conditions such as:

• Solder bridging

• Voiding

• Insufficient solder

• Alignment

• Hidden solder-joint conditions

X-ray requirements are determined according to the component package, product requirements, and applicable inspection criteria.

Not every PCB assembly requires X-ray inspection.

12. THT / DIP & Mixed-Technology Assembly

Many PCB assemblies contain components that cannot be assembled using SMT alone.

For through-hole and mixed-technology products, the manufacturing process may include:

• Manual component insertion

• Through-hole assembly

• Wave soldering

• Selective soldering

• Hand soldering

• Mechanical component installation

• Connector assembly

• Applicable rework operations

The soldering method depends on the component type, PCB design, production quantity, thermal requirements, and accessibility.

Mixed SMT and THT assemblies are planned as one complete manufacturing process rather than as unrelated operations.

13. Programming & Firmware Loading

Where required, ICs, MCUs, memory devices, or other programmable components can be programmed as part of the manufacturing process.

Programming may be performed at different stages depending on the product and production method.

Programming requirements may include:

• Firmware file

• Firmware revision

• Programming interface

• Programming tool

• Device configuration

• Serial number

• Calibration data

• Verification procedure

Firmware and programming revision control should be confirmed before production.

Programming status can also be incorporated into applicable production or test records according to project requirements.

14. ICT & Functional Testing

Inspection confirms manufacturing conditions, but many electronic products also require electrical or functional verification.

Depending on the product, testing may include:

• Power-on verification

• In-Circuit Testing (ICT)

• Functional Testing (FCT)

• Voltage and current measurement

• Communication interface testing

• I/O verification

• Sensor verification

• Customer-defined test procedures

• Product-specific functional checks

Test scope is determined according to the product and customer requirements.

AOI or X-ray inspection should not be considered a replacement for functional testing when product-level operation needs to be verified.

15. Customer Test Procedures & Functional Test Fixtures

For customer-specific products, functional testing can be performed according to an agreed test method.

Customers may provide:

• Existing test procedures

• Pass/fail criteria

• Test points

• Required measurements

• Input power conditions

• Communication commands

• Programming requirements

• Reference units

• Existing test fixture information

Where required, we can evaluate the design and preparation of a functional test fixture based on the customer's test method and production requirements.

Fixture development may include:

• Mechanical interface

• Electrical connections

• Test probes

• Power interfaces

• Communication interfaces

• Measurement equipment

• Programming interface

• Operator procedure

• Pass/fail criteria

Fixture development scope, validation requirements, and applicable NRE costs are reviewed before implementation.

16. Inspection & Quality Control Throughout Production

Quality control is not limited to a single inspection at the end of production.

Depending on the product and manufacturing requirements, inspection and verification may occur at multiple stages:

Incoming Material → Solder Paste Printing → SPI → First Article → SMT Placement → Reflow → AOI → X-Ray where required → THT Inspection → Programming Verification → ICT/FCT → Final Inspection

Different inspection methods are used for different purposes.

For example:

• IQC checks applicable incoming material requirements.

• SPI evaluates solder paste printing before placement.

• First Article Verification checks the initial production setup.

• AOI inspects visible SMT assembly conditions.

• X-Ray evaluates applicable hidden solder-joint conditions.

• ICT/FCT verifies electrical or functional requirements.

• Final Inspection verifies the completed assembly before release.

Using multiple inspection points helps identify manufacturing issues closer to the process where they occur.

19. Production Traceability

Traceability requirements vary by customer, product, and industry.

Depending on project requirements, production records may include:

• PCB part number and revision

• BOM revision

• Production lot

• Component lot or date-code information where required

• Firmware revision

• Programming status

• Serial number

• Inspection records

• Test results

• Rework records

• Manufacturing date

• Shipment information

Customer-specific traceability requirements should be identified during project preparation so that the required information can be incorporated into the manufacturing process.

For regulated or quality-sensitive products, additional traceability requirements may apply according to the customer's specifications and applicable industry requirements.

20. Final Inspection & Final Quality Audit

Before completed PCB assemblies are released for shipment, final inspection is performed according to the applicable product and customer requirements.

Final verification may include:

• Workmanship

• PCB revision

• Assembly revision

• Component installation

• Labeling

• Serial number

• Programming status

• Functional test status

• Customer-specific requirements

• Mechanical assembly

• Packaging requirements

Applicable inspection and test records can be maintained according to the agreed project and quality requirements.

21. Packaging & Shipment Preparation

Packaging requirements depend on the product and customer specifications.

Depending on the project, packaging may include:

• ESD-safe packaging

• Protective packaging

• Moisture barrier packaging where required

• Vacuum sealing where applicable

• Product labeling

• Carton labeling

• Customer-specific packaging instructions

Finished assemblies are prepared for shipment according to the applicable handling and delivery requirements.

From Prototype to NPI, Pilot Run & Production

The core PCB assembly manufacturing process is generally similar from prototype through repeat production.

A prototype and a larger production order may both require:

• Material preparation

• Solder paste printing

• SMT placement

• Reflow

• Inspection

• THT assembly

• Programming

• Functional testing

However, manufacturing controls and production planning can change as volume increases.

Prototype

Prototype builds typically focus on:

• Design verification

• Initial component sourcing

• Manufacturing verification

• Programming

• Functional testing

• Identification of potential design or assembly issues

NPI

NPI focuses on establishing a repeatable manufacturing process.

Activities may include:

• DFM review

• BOM verification

• Process preparation

• Programming validation

• Test fixture preparation

• First Article Verification

• Functional test validation

• Manufacturing documentation

Pilot Run

A pilot run provides an opportunity to verify the manufacturing process at a larger quantity before repeat production.

Depending on the project, this may include:

• Process validation

• Yield review

• Test validation

• Fixture validation

• Packaging verification

• Material planning

• Production documentation

Repeat Production

Once the product design and manufacturing requirements are stable, repeat production can be planned using approved materials, established manufacturing documentation, validated programming, test procedures, and production controls.

Production planning may include:

• BOM and revision control

• Component forecasting

• Long-lead-time material planning

• MOQ / SPQ management

• Production scheduling

• Test capacity

• Yield monitoring

• Engineering change control

• Packaging

• Delivery planning

The objective is to move from initial engineering verification toward a controlled, repeatable, and scalable manufacturing process.

Does the PCB Assembly Process Change as Production Volume Increases?

The core manufacturing steps generally remain similar, but the manufacturing strategy can change as production volume increases.

Depending on the product and quantity, higher-volume production may require:

• Different panelization

• Dedicated production fixtures

• Automated testing

• Optimized SMT line setup

• Material forecasting

• Reel purchasing

• Additional process controls

• Different inspection or sampling plans

• Production yield monitoring

• Packaging optimization

• Expanded traceability

A 10-piece prototype and a 10,000-piece production order may therefore use the same fundamental assembly technology while having different production planning, cost structures, test strategies, and process controls.

PCB Assembly Acceptance Criteria

Workmanship and inspection requirements depend on the applicable customer and product requirements.

Where specified, PCB assemblies can be evaluated according to applicable IPC-A-610 acceptance criteria.

Customer drawings, specifications, approved samples, test procedures, or other acceptance criteria may also form part of the manufacturing requirements.

Acceptance criteria should be defined before production when customer-specific requirements differ from the applicable acceptance criteria.

Our PCB Assembly Manufacturing & Inspection Capabilities

Leader Global Electronics supports PCB assembly and EMS manufacturing in Taiwan with:

• 5 SMT Production Lines

• 1 THT Assembly Line

• SMT, THT & Mixed-Technology Assembly

• Components down to 01005

• BGA, QFN, LGA & CSP

• Solder Paste Inspection (SPI)

• Automated Optical Inspection (AOI)

• X-Ray Inspection

• ICT

• Functional Testing

• IC / MCU Programming

• Functional Test Fixture Development

• Box Build Assembly

• Maximum PCB Size: 500 × 500 mm

• Up to 6.2 Million Component Placements per Day

• ESD / MSD Control

The applicable manufacturing, inspection, testing, and production process is determined according to the actual PCB design and project requirements.

What We Need for PCB Assembly Manufacturing

For manufacturing review and quotation, please provide:

• Gerber files

• BOM with manufacturer part numbers

• Pick & Place data

• Assembly drawings

• Required quantity

• PCB fabrication requirements

• Programming requirements

• Functional test requirements

• Customer-specific inspection requirements

• Target delivery date

If customer-specific workmanship, traceability, testing, packaging, or documentation requirements apply, please include them with the RFQ.

If you are planning future production, providing expected prototype, NPI, pilot, and production quantities can also help us evaluate the appropriate manufacturing approach.

Our engineering team can review the manufacturing package before production planning.

Email: sales@leaderelec.com.tw

NDA available upon request.

PCB Assembly Process FAQ

What is the typical PCB assembly process?

A typical PCB assembly process may include engineering review, PCB fabrication, component sourcing, incoming inspection, solder paste printing, SPI, SMT placement, reflow, AOI, X-ray where required, through-hole assembly, programming, functional testing, final inspection, and packaging.

The exact process depends on the PCB design, component packages, product requirements, production quantity, and customer specifications.

Why is SPI performed before SMT placement?

SPI checks solder paste after printing and before components are placed.

This makes it possible to identify printing conditions such as insufficient paste, excessive paste, offset, or missing deposits before the PCB proceeds through placement and reflow.

What is the difference between SPI and AOI?

SPI evaluates solder paste printing before SMT component placement.

AOI is generally used after component placement and reflow to inspect visible assembly conditions such as missing components, placement errors, polarity, tombstoning, bridging, and applicable solder-joint defects.

They perform different functions within the PCB assembly process.

Does AOI inspect BGA solder joints?

AOI cannot directly inspect solder joints hidden underneath a BGA package.

Where inspection of hidden solder joints is required, X-ray inspection may be used depending on the component package and project requirements.

Do all PCB assemblies require X-ray inspection?

No.

X-ray inspection is typically used where solder joints cannot be adequately evaluated using visual inspection or AOI, such as BGA and certain QFN, LGA, or other bottom-terminated components.

Inspection requirements are determined according to the PCB design and applicable quality requirements.

Do you perform first article inspection before production?

For applicable first-time, prototype, or NPI builds, first article verification can be used to confirm component placement, polarity, orientation, production setup, and applicable assembly requirements before continuing with the remaining production quantity.

The exact first article requirements depend on the project.

Can you follow our own inspection and test requirements?

Yes.

Customer-specific inspection criteria, functional test procedures, programming requirements, acceptance criteria, and documentation requirements can be reviewed during project preparation.

Where required, these requirements can be incorporated into the applicable manufacturing and quality documentation before production.

Can you manufacture a functional test fixture according to our test method?

Depending on the product and testing requirements, yes.

We can review customer-provided test procedures, test points, operating conditions, measurements, communication interfaces, programming requirements, and pass/fail criteria.

Where required, a functional test fixture can be designed and built according to the agreed testing method.

Fixture scope and applicable development or NRE costs are reviewed before implementation.

What happens if a defect is found during PCB assembly?

The affected material can be segregated while the issue is reviewed.

Depending on the defect, additional inspection, production-record review, engineering analysis, rework, root-cause investigation, corrective action, or customer communication may be required.

Reworked boards are re-inspected or re-tested according to the applicable process requirements before release.

Can you provide production traceability?

Yes, according to the agreed project requirements.

Depending on the product, traceability may include PCB and BOM revision, production lot, component lot/date-code information where required, firmware revision, serial number, inspection records, test results, and rework information.

Required traceability should be defined during project preparation.

Can you support IPC-A-610 requirements? 

Yes. PCB assembly workmanship and inspection requirements can be established according to the applicable IPC-A-610 acceptance criteria and customer-specific requirements.

The required acceptance criteria should be identified before production so that the appropriate manufacturing and inspection requirements can be incorporated into the project.

Is the PCB assembly process the same for prototypes and production?

The core manufacturing flow is generally similar.

Both prototype and production builds may require solder paste printing, component placement, reflow, inspection, through-hole assembly, programming, and testing.

However, larger production quantities may require different fixtures, material planning, automation, inspection plans, process controls, traceability, and production scheduling.

Can you support PCB assembly from prototype to production?

Yes.

Leader Global Electronics supports prototype, NPI, pilot-run, and repeat PCB assembly programs.

The manufacturing process can be developed progressively from initial engineering verification through NPI and pilot production to repeat manufacturing.

The applicable BOM, PCB revision, manufacturing documentation, approved components, programming procedure, test procedure, quality requirements, and production controls should be established before repeat production.

Request a PCB Assembly Manufacturing Review

If you are evaluating PCB assembly manufacturing in Taiwan, send us the available project files and manufacturing requirements.

For quotation, please include:

• Gerber files

• BOM with manufacturer part numbers

• Pick & Place data

• Assembly drawings

• Required quantity

• Programming requirements

• Functional test requirements

• Applicable inspection or quality requirements

• Target delivery date

If you already have an established manufacturing process, test procedure, quality plan, approved component list, or existing production documentation, these can also be reviewed during project preparation.

If future production quantities are known, please include them with the RFQ so that prototype, NPI, pilot-run, and production requirements can be evaluated together.

Email: sales@leaderelec.com.tw

NDA available upon request.

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