EV charging equipment combines power conversion, control, communication, sensing, and connection functions. Depending on the charger architecture and individual PCB design, manufacturers may need to assemble both compact SMT components and larger through-hole components.
A typical EV charger PCBA can therefore require a mixed manufacturing process:
SMT Assembly → THT Component Preparation → THT Insertion → Pre-Solder Inspection → Wave or Selective Soldering → Inspection → Testing
Some products may also require downstream processes such as conformal coating or mechanical assembly.
Building an effective THT assembly solution for EV charger PCBs requires more than selecting an insertion conveyor or soldering machine. PCB construction, component types, thermal mass, solder-joint layout, production volume, testing, and factory automation should all be evaluated together.
THT Assembly Solution for EV Charger PCBs
This guide explains how manufacturers can configure a practical THT production line for EV charging electronics.
Why Is THT Used in EV Charger PCB Assembly?
SMT is widely used for modern electronic assembly because it supports compact, highly automated production.
However, depending on the EV charger design, certain components may use through-hole mounting because of:
- Component package
- Physical size
- Lead structure
- Mechanical requirements
- Electrical requirements
- Product design
- Potential THT components can include:
- Transformers
- Inductors
- Chokes
- Large electrolytic capacitors
- Relays
- Connectors
- Terminal blocks
- Fuses
- Selected power resistors
- Selected power semiconductor packages
Not every EV charger PCB contains all of these components.
The correct THT process should therefore be developed from the actual PCB and BOM.
THT vs DIP in EV Charger Manufacturing
THT stands for Through-Hole Technology. Component leads are inserted through holes in the PCB and soldered.
DIP means Dual In-line Package, which describes a particular component package.
Therefore, THT is the broader technical term.
In electronics factories, however, terms such as DIP line, DIP assembly line, and DIP production line are often used as general names for the through-hole assembly section.
For EV charger PCBA manufacturing, the production process may contain many THT components that are not DIP packages.
Typical EV Charger PCBA Production Flow
A mixed SMT and THT process may look like:
PCB Loader → Solder Paste Printing → SPI → SMT Placement → Reflow → AOI → THT Component Preparation → THT Insertion → Pre-Solder Inspection → Wave/Selective Soldering → Cooling → Inspection → Testing
Additional processes may include:
- Programming
- Product-specific electrical testing
- Conformal coating
- Mechanical assembly
- Final system testing
The exact sequence depends on the charger design and manufacturing requirements.
Step 1: Review the EV Charger PCB and BOM
Before selecting THT equipment, manufacturers should collect:
- PCB dimensions
- PCB thickness
- Panel dimensions
- PCB weight
- THT component list
- Quantity of each component
- Component dimensions
- Lead structure
- Pin spacing
- Polarity/orientation
- Component packaging
- Bottom-side PCB layout
This information determines whether components should be:
- Automatically inserted
- Semi-automatically processed
- Manually inserted
It also affects the choice between wave and selective soldering.
Step 2: Classify THT Components
Not every THT component should be automated.
Components Potentially Suitable for Automatic Insertion
Automation may be considered when components have:
- Standardized geometry
- Compatible leads
- Consistent orientation
- Suitable packaging
- Sufficient production quantity
Components Suitable for Semi-Automatic Processing
Some parts may benefit from:
- Component presentation
- Guided insertion
- Fixtures
- PCB positioning
- Visual work instructions
Components Better Suited to Manual Insertion
Depending on the design, these may include:
- Large transformers
- Heavy inductors
- Large capacitors
- Irregular connectors
- Terminal blocks
- Low-quantity components
A hybrid automatic + manual strategy is often more practical than attempting to automate every THT component.
Step 3: Plan Component Preparation
Some THT components may require preparation before insertion.
Processes can include:
- Lead cutting
- Lead forming
- Bending
- Straightening
- Sorting
- Kitting
For higher-volume production, component preparation can become a bottleneck.
Manufacturers should determine whether repetitive preparation processes can be automated or semi-automated.
Component Packaging Affects Automation
THT components may arrive in:
- Tape
- Reel
- Tube
- Tray
- Bulk packaging
- Custom packaging
Even if a component is geometrically suitable for automatic insertion, inconsistent packaging or orientation can make feeding difficult.
Component packaging should therefore be reviewed early in the automation project.
Step 4: Design the THT Insertion Process
A flexible EV charger THT insertion area may use:
Component Preparation → Automatic Insertion for Suitable Parts → Manual Insertion Stations → Pre-Solder Inspection
Manual stations should be designed for:
- Efficient material access
- Clear work instructions
- Controlled component sequence
- ESD requirements
- Appropriate PCB support
Large or heavy PCBAs may also require stable fixtures or conveyor support.
Polarity and Orientation Control
EV charger PCBAs may contain polarized components such as:
- Electrolytic capacitors
- Diodes
- Selected semiconductor components
Incorrect orientation can create serious downstream problems.
Controls can include:
- Clear PCB markings
- Material-bin identification
- Visual work instructions
- Guided insertion
- Material verification
- Pre-solder inspection
Detecting errors before soldering reduces rework complexity.
Step 5: Pre-Solder Inspection
Before the PCB enters soldering, check for:
- Missing components
- Wrong components
- Incorrect polarity
- Incorrect orientation
- Bent leads
- Incorrect seating
- Insertion-depth problems
For higher-volume production, early inspection is particularly valuable because repeated assembly errors can affect many boards before they are detected downstream.
Step 6: Choose Wave or Selective Soldering
Two major automated THT soldering options are:
Wave Soldering and Selective Soldering.
Neither process is universally better for EV charger PCBAs.
The correct process depends on:
- THT joint quantity
- Joint distribution
- PCB underside layout
- Bottom-side SMT components
- Thermal mass
- Production volume
- Product mix
- Required cycle time
Wave Soldering for EV Charger PCBs
Wave soldering can be efficient when the PCB contains many compatible THT joints and the underside design supports wave processing.
A typical wave soldering process is:
Fluxing → Preheating → Wave Soldering → Cooling
A wave soldering machine may include:
- Spray fluxer
- Preheating zones
- Conveyor
- Solder pot
- Pump/wave system
- Cooling
- Recipe/control system
Important process factors include:
- Flux coverage
- Preheating
- Solder temperature
- Conveyor speed
- Wave stability
- PCB orientation
- Component solderability
- Equipment maintenance
There is no universal wave soldering recipe for every EV charger PCB.
Selective Soldering for EV Charger PCBs
Selective soldering applies flux and solder to programmed locations.
It can be useful when:
- THT joints are localized
- Bottom-side SMT limits wave exposure
- Specific areas require controlled soldering
- Product mix requires flexible programs
Machine selection should consider:
- Nozzle size
- Nozzle access
- Bottom-side clearance
- Fluxing
- Preheat
- PCB support
- Joint quantity
- Cycle time
A small nozzle can access tighter areas, but it may increase soldering time if many joints must be processed individually.
Wave Soldering vs Selective Soldering
The actual PCB should determine the soldering strategy.
EV Charger PCBs and High Thermal Mass
Some EV charging electronics may use:
- Thick copper
- Large copper areas
- Large terminals
- Transformers
- Inductors
- Power components
- Heavy connectors
These features can create significant thermal mass.
As a result, the PCB may not heat uniformly during soldering.
This can influence:
- Flux activation
- Wetting
- Hole fill
- Process window
Manufacturers should evaluate actual PCB temperature behavior rather than assuming the machine setpoint represents every solder joint.
Preheating Is Particularly Important
Preheating can help:
- Activate flux
- Gradually heat the assembly
- Reduce thermal differences
- Support solder wetting
For a thermally demanding EV charger board, insufficient preheating may contribute to poor soldering.
However, there is no universal preheat temperature.
The correct process depends on:
PCB + Components + Flux + Solder Alloy + Equipment
PCB Support and Warpage
Large or heavy PCBAs can require additional support during transport and soldering.
Potential solutions include:
- Center support
- Conveyor support
- Fixtures
- Soldering pallets
Support should prevent excessive board movement while maintaining access to required soldering areas.
Should You Use a Wave Soldering Pallet?
A pallet may be useful when the board requires:
- Bottom-side SMT shielding
- Selective solder exposure
- Additional PCB support
- Protection of specific areas
However, pallets also introduce:
- Tooling cost
- Additional thermal mass
- Cleaning requirements
- Maintenance
- Storage
They should be used when justified by PCB design and process requirements.
Step 7: Cooling
After soldering, controlled cooling prepares the board for downstream handling and inspection.
Cooling capacity should be included in line planning, particularly for assemblies with:
- High thermal mass
- Large components
- High production volume
The PCB should not be transferred to sensitive downstream operations before it reaches appropriate handling conditions.
Step 8: Post-Solder Inspection
Typical THT soldering defects can include:
- Solder bridges
- Insufficient solder
- Incomplete hole fill
- Poor wetting
- Excessive solder
- Icicles
- Solder balls
Potential causes can include:
- Flux application
- Preheat
- Solder temperature
- Solderability
- PCB design
- Lead condition
- Conveyor parameters
- Wave/nozzle condition
Troubleshooting should evaluate the complete process rather than changing one parameter in isolation.
Inspection Equipment
Inspection methods depend on the product and joint structure.
Potential methods include:
- Visual inspection
- AOI where applicable
- X-ray for selected hidden structures where required
- Electrical testing
X-ray should not automatically be treated as necessary for every THT joint.
Inspection should match the actual defect risks and product requirements.
Step 9: Testing EV Charger PCBAs
Testing is an important part of EV charger electronics manufacturing.
Depending on the board function and product requirements, processes may include:
- ICT
- Programming
- Functional testing
- Communication testing
- Product-specific electrical testing
Where higher voltage or other safety-related tests are required, manufacturers should use equipment and procedures appropriate to the actual product and applicable requirements.
Testing must also be included in production-capacity planning.
Testing Can Become the Main Bottleneck
Consider:
The effective finished-line capacity is approximately 35 boards per hour because testing is the slowest process.
Increasing wave soldering capacity from 90 to 120 boards per hour would not significantly improve finished output.
Parallel Testing
Suppose one functional test requires: 90 seconds per PCB
but the production takt is: 30 seconds per PCB
A simplified capacity calculation suggests:
90 ÷ 30 = 3 parallel test positions
may be needed before allowing for loading, unloading, efficiency, retest, and product variation.
Testing architecture should therefore be designed alongside assembly equipment.
Step 10: Balance the Complete THT Line
Evaluate:
Component Preparation → Insertion → Inspection → Soldering → Cooling → Inspection → Testing
Important metrics include:
- Takt time
- Cycle time
- WIP
- First-pass yield
- Rework
- Changeover
- Downtime
- Equipment utilization
The objective is not maximum soldering-machine speed.
It is stable output of good finished PCBAs.
High-Mix EV Charger PCB Production
Factories producing multiple charger models may prioritize:
- Flexible manual insertion
- Semi-automatic preparation
- Quick changeover
- Recipe management
- Adjustable conveyors
- Flexible selective soldering
- Efficient test-fixture changeover
A possible configuration is:
Component Preparation → Manual/Semi-Automatic Insertion → Pre-Solder Inspection → Selective/Wave Soldering → Inspection → Testing
For high-mix production, flexibility can be more valuable than maximum automation.
Medium-Volume THT Production Line
A medium-volume configuration may use:
PCB Loading → Component Preparation → Insertion Conveyor → Manual/Semi-Automatic THT Insertion → Inspection → Wave/Selective Soldering → Cooling → Inspection → Parallel Testing
This configuration can provide a practical balance between:
- Labor
- Flexibility
- Capacity
- Investment
Higher-Volume Automatic THT Line
For stable higher-volume products, manufacturers can evaluate:
Automatic PCB Loading → Automatic Component Preparation → Automatic THT Insertion for Suitable Components → Manual Insertion for Irregular Components → Automatic Transfer → Wave/Selective Soldering → Cooling → Inspection → Parallel Testing → Unloading
Optional automation can include:
- Barcode identification
- Buffers
- Automatic width adjustment
- Recipe management
- Traceability
- Production-data collection
Not every step needs to be automated to create an efficient high-volume line.
Integrating SMT and THT Production
EV charger PCBA manufacturing may require both SMT and THT lines.
A complete process can be:
Solder Paste Printing → SPI → SMT Placement → Reflow → AOI → THT Insertion → Wave/Selective Soldering → Inspection → Testing
Capacity should be balanced across both sections.
For example:
SMT output: 100 boards/hour
THT output: 55 boards/hour
Testing output: 30 boards/hour
In this case, increasing SMT placement speed does not address the main production limitation.
Testing should be evaluated first.
Material Logistics
High production capacity depends on stable material supply.
Plan:
Incoming component storage
Kitting
Component preparation
Line-side inventory
Material verification
Replenishment
Empty packaging handling
An automatic insertion machine cannot maintain output if components are not prepared and supplied consistently.
Traceability
Depending on the product and customer requirements, traceability may include:
- PCB ID
- Product model
- Material lot
- Production time
- Machine
- Soldering recipe
- Inspection result
- Test result
Barcode systems can help connect individual PCBAs with manufacturing data.
Traceability requirements should be defined before equipment procurement.
Conformal Coating for EV Charger PCBAs
Some EV charger PCBAs may require conformal coating depending on:
- Installation environment
- Humidity exposure
- Contamination risk
- Enclosure
- Product specification
- Customer requirements
A possible downstream process is:
Testing → Cleaning/Surface Preparation → Selective Coating → Inspection → Flash-Off → Curing → Final Inspection
However, not every EV charger PCB requires conformal coating.
Coating should be based on actual product requirements rather than being treated as a universal process.
Utilities
Depending on the equipment configuration, manufacturers may need:
- Electrical power
- Compressed air
- Exhaust
- Ventilation
- Nitrogen where required by the process
- Network connections
- Utilities should be planned before installation.
Maintenance and Spare Parts
Stable production requires preventive maintenance.
For insertion equipment, maintenance can include:
- Feeding mechanisms
- Sensors
- Insertion heads
- Conveyor
- Controls
For wave or selective soldering equipment:
- Fluxing system
- Preheating
- Conveyor
- Solder pot
- Pump/wave/nozzle
- Cooling
- Exhaust
- Controls
Critical spare parts should be evaluated based on failure risk, downtime impact, and procurement lead time.
New vs Pre-Owned THT Equipment
EV charger manufacturers may consider both new and suitable pre-owned equipment.
When evaluating pre-owned machines, review:
- Mechanical condition
- Machine age
- Maintenance history
- Controls
- Software
- PCB handling
- Spare-parts availability
- Technical support
For soldering equipment, also inspect:
- Fluxer
- Preheat
- Conveyor
- Solder pot
- Pump/wave/nozzle
- Cooling
- Exhaust interfaces
Evaluate total cost of ownership rather than purchase price alone.
THT and PCBA Production Solutions from Fuliu Electronics
Established in 2014, Fuliu Electronics is dedicated to providing customers with high-quality PCBA intelligent manufacturing solutions and services.
With extensive experience in the SMT industry, we specialize in dependable equipment, professional technical support, and complete SMT and PCBA production line solutions.
Our product portfolio includes SMT pick and place machines from Fuji, Panasonic, ASM, Yamaha, JUKI, and Hanwha, together with ERSA reflow ovens from Germany, MagicRay SPI/AOI inspection systems, automatic solder paste printers, supporting PCBA equipment, pre-owned SMT equipment, SMT spare parts, machine leasing, and maintenance services.
For EV charger electronics manufacturers, Fuliu Electronics can help evaluate the complete process:
SMT Assembly → THT Component Preparation → THT Insertion → Wave/Selective Soldering → Inspection → Testing → Optional Conformal Coating
As part of our global growth strategy, Fuliu Electronics is actively expanding into international markets, with key focus areas including India, Vietnam, the Philippines, Indonesia, the Middle East, South Africa, and Europe.
Conclusion
A successful THT assembly solution for EV charger PCBs should be developed around the complete manufacturing process:
SMT Assembly → THT Component Preparation → THT Insertion → Pre-Solder Inspection → Wave/Selective Soldering → Cooling → Inspection → Testing
For high-mix production, flexible manual and semi-automatic THT assembly combined with suitable soldering equipment may provide an efficient approach.
For stable higher-volume manufacturing, automatic component preparation and insertion for suitable parts can be combined with manual insertion for irregular components, automated soldering, inspection, and sufficient parallel testing capacity.
Most importantly, manufacturers should optimize finished PCBA throughput and total production economics, not the rated speed of a single machine.
If you are planning a new EV charger PCB production line, upgrading an existing THT/DIP process, or integrating through-hole assembly with an SMT production line, Fuliu Electronics can help evaluate your PCB dimensions, BOM, component packaging, target capacity, soldering process, testing requirements, existing equipment, factory layout, automation target, and investment budget to develop a suitable PCBA manufacturing solution.
Frequently Asked Questions
Depending on product design, THT can be used for transformers, inductors, large capacitors, relays, terminals, connectors, fuses, and other components whose package or mechanical/electrical requirements suit through-hole mounting.
No. THT is the mounting technology, while DIP is a particular package style. “DIP line” is nevertheless commonly used as factory terminology for THT assembly.
Yes, suitable standardized components can potentially use automatic insertion. Large, heavy, irregular, or low-quantity components may remain better suited to manual or semi-automatic insertion.
It can be suitable when the board contains many compatible THT joints and the PCB underside supports wave processing.
Selective soldering can be useful for localized THT joints, mixed-technology boards, or layouts where broad wave exposure is undesirable.
Large copper areas and power components can absorb significant heat, affecting preheating, wetting, and hole fill. The actual PCB thermal behavior should be evaluated during process development.