Table
of Contents
1. What Does a PCB Assembly Do Inside an EV Charger?
2. How Power Requirements Affect EV Charger
PCB Assembly
3. From Fine-Pitch SMT to Power Component
Assembly
4. Testing EV Charger PCB Assemblies for the
Right Failure Modes
5. Conclusion
6. FAQs
At first glance, an electric vehicle charger
(EV charger) appears to be a complete charging device. But when you open the
device, you will find that the internal circuits have different tasks. Some are
responsible for control and communication, while others need to handle higher
currents, voltages and heat.
What does this have to do with manufacturing?
In fact, it has a significant relationship. The requirements for EV charger PCB
assembly of different circuits also vary. Control circuits may mainly use
precision SMT components, while power-related circuits may involve large
connectors, relays, through-hole components, as well as higher current-carrying
and heat dissipation requirements. Therefore, manufacturing the EV charger PCBA
is not simply mounting components on the EV charger PCB; it requires choosing
appropriate assembly, soldering and testing methods based on the actual
functions of the circuits.
In this article, we will start by explaining
the functions of different circuits inside the EV charger, and see what
practical impacts high currents, high voltages and heat will have on PCB
assembly, as well as how these requirements are implemented in the production
process. At the same time, we will also introduce the specific roles of SMT,
through-hole power component assembly, AOI, X-Ray and functional testing in EV
charger PCBA manufacturing.
What Does a PCB Assembly Do Inside an EV
Charger?
An EV charger usually has more than one type of
circuit. Different PCBs perform different tasks. Depending on the specific
system architecture, the EV charger PCB may be responsible for control and
communication, power management, metering, protection, or it may be responsible
for connecting external devices. Due to the different functions, the used
components are different, and the subsequent assembly and testing requirements
will naturally also be different.
|
Function
|
Typical
Electronic Components
|
Primary
Assembly Focuses
|
|
Control & Communication
|
MCU, communication ICs, sensing circuit
|
SMT accuracy, programming, functional testing
|
|
Power & High-Current
|
Power devices, relays, drivers, large connectors
|
Current handling, thermal load, solder joint quality
|
|
Metering & Interfaces
|
Metering IC, Connectors, I/O Circuit
|
Mixed Assembly, Connector Reliability,
Function Testing
|
Let's take a simple example. The smart EV
charger PCBA usually needs to handle charging control, network communication
and status monitoring. Therefore, it may use an MCU, communication ICs, sensing
circuits and a large number of SMD components. For such circuits, we pay more
attention to the assembly accuracy, soldering quality, as well as whether the required
functions are normal.
What about the power-related circuits? The
focus is quite different. These circuits may use power semiconductors, relays,
drivers and large connectors, which need to withstand greater current and
higher thermal loads. Compared to small SMD components, the problems faced when
mounting and soldering these devices are also different. The metering and
interface parts mainly handle the connection of sensors, displays,
communication ports and other external devices, and have corresponding
requirements for connector installation and function testing.
So, we cannot treat all the EV charging station
PCBA as the same type of circuit board for production. First, figure out what
this board is responsible for, and then decide how to assemble, how to solder,
which positions to check and which functions to test. For EV charger PCB
assembly, this is also an important step in determining the manufacturing
process.
How Power Requirements Affect EV
Charger PCB Assembly
Power-related circuits are a part that requires
particular attention in EV charger PCB assembly. The reason is simple: the
greater the current, the more attention needs to be paid to the current that
the PCB has to carry and the heat it generates; when the voltage increases, the
isolation requirements between different electrical areas become even more
important. Although these issues need to be addressed in the PCB design stage
first, they will ultimately affect the actual assembly, soldering, and testing.
High
Current and Heavy Copper
How does high current affect PCB assembly?
First, let's look at the PCB itself. For some high-current paths, an EV charger
PCB may use a wider copper area, a thicker copper layer, or other
current-carrying structures. A heavy copper PCB can be used to carry larger
currents and also helps with heat conduction, but as the copper increases, the soldering
conditions during production will also change.
We need to consider a very practical issue
during soldering: a large area of copper needs to absorb and transfer more heat
to reach the proper soldering temperature and form a good solder joint.
Therefore, in heavy copper PCB assembly, we need to set and verify the soldering
temperature curve based on the copper thickness, copper area, and the actual
component configuration to ensure that the solder joints are fully wetted while
avoiding excessive thermal stress on small or temperature-sensitive components.
Of course, this does not mean that all EV
charger PCB need to use heavy copper. The working current of control and
communication circuits may not be high, while the current-carrying requirements
of power-related circuits may be completely different. Whether to use heavy
copper ultimately depends on the specific electrical design.
High
Voltage and Electrical Isolation
The problems brought by high voltage are
different from those caused by large currents. For high voltage PCB assembly,
the creepage distance, clearance, and isolation areas are usually determined
during the design stage, but during the production process, we still need to
ensure that these designs will not be affected by assembly or rework.
In actual production, several key points need
to be paid attention to:
• Creepage and clearance: Components, solder, or hardware cannot occupy the originally
reserved safety spacing.
• Slots and isolation areas: During assembly and rework, the already designed isolation features
built into the PCB should not be damaged or interfaced.
• Components and alternative
parts: It is important to check not only the
electrical specifications but also the package dimensions and insulation
requirements.
• Soldering and rework: Attention should be paid to solder, residues, and the impact of the
rework process near the isolation area.
So, we need to verify these critical areas
through DFM and pre-production review before formally putting the EV charger
PCBA into production. Which positions cannot be occupied? Which areas need additional
inspection? These questions should be clarified before starting production.
Power
Components and Thermal Capacity
Let's take a look at the components themselves.
Power electronics PCB assembly usually involves not only small SMD components,
but also may include:
• Power semiconductors
• Relays and large connectors
• Inductors and transformers
• Small resistors, capacitors, and
control ICs
These components vary greatly in size and
thermal characteristics, and cannot be soldered in the same way naturally. Large
components and large copper areas require more heat, while small components
heat up fast and cannot take a lot of heat for a long time.
This is why a power PCB may need several
assembly and soldering processes. We may use a combination of SMT, through-hole
assembly, reflow soldering and selective soldering to separate the different
kinds of components, depending on what the actual board design is.
From Fine-Pitch SMT to Power
Component Assembly
In an EV charger PCB assembly, there are often
not just small SMD components. The control and communication area may be
dominated by SMT components, while the power area may feature relays, large
connectors, inductors, transformers, and other larger components. The different
types of components require different assembly methods.
During production, we usually handle them
separately:
• SMT components: MCU, communication ICs, resistors, capacitors, etc., will undergo
solder paste printing, SPI, automatic placement, reflow soldering, and AOI
inspection.
• Through-hole and power
components: relays, large connectors, inductors,
transformers, etc., with pins, can be assembled using through-hole technology,
and then choose between wave soldering or selective soldering based on the PCB
structure.
Why can't everything be assembled in the same
way? Because an EV charging station PCB assembly may undergo both SMT and THT
processes, and large power components, large copper areas, and small SMD
components have different heat conditions. We need to arrange the assembly
sequence and soldering processes according to the actual PCB.
Inspection is the same. SPI and AOI can detect
many problems in SMT production, but some solder joints are invisible. For
example, BGA, QFN, and component with bottom thermal pads, we need to use X-Ray
to further check the hidden solder joints.
At PCBasic, we arrange the production process
based on the actual structure of the EV charger PCBA. SMT, DIP, wave soldering,
and selective soldering can be combined according to the type of components,
and are combined with SPI, AOI, and 3D X-Ray inspection instead of applying the
same production process to all projects.
Testing EV Charger PCB Assemblies
for the Right Failure Modes
The AOI inspection has been passed. Does this
mean the board has completed the testing? No. The AOI can detect issues such as
component offset, polarity, and some soldering problems, but it cannot tell us
whether the circuit can actually work properly. For EV charger PCB assembly,
different problems require different inspection and testing methods.
During production, we usually combine several
methods:
• SPI, AOI and X-Ray: SPI is used to check solder paste before reflow, AOI is used to
detect visible placement and soldering issues, and X-Ray is employed to examine
the solder joints that cannot be seen beneath BGA, QFN, etc. components.
• ICT or flying probe
testing: This can check for open circuits, short
circuits, electrical connections, selected component values, and circuit conditions.
• Functional testing: FCT focuses more on whether this EV charger PCBA can operate
according to the design requirements. Depending on the project, we can test
power-on, voltage, communication interfaces, I/O, control signals, firmware programming,
and other specified functions.
So, are all the boards tested with the same set
of tests? No. The issues that need attention for smart EV charger PCBA focused
on control and communication, and the EV charger PCB related to power, are not
the same. If the project has requirements, high-voltage or power-related PCBA
may also need to undergo insulation, load or temperature rise testing.
Therefore, the test plan should be clearly
confirmed before production. What needs to be tested for the EV charger station
PCBA? What fixtures are needed? What firmware is required? What are the
qualification standards? The earlier these pieces of information are
determined, the easier it will be to maintain consistency in volume production
tests. As for the safety and compliance certifications of the entire product,
they need to be separated from the tests conducted during the PCBA production
stage.
In PCBasic, the test plan is confirmed together
during the project introduction stage. Based on the actual requirements of the
EV charger PCB assembly, FAI, flying probe testing, ICT, FCT or dedicated
functional test fixtures can be selected. Production and test data can also be
recorded through MES, facilitating traceability during volume production.
Conclusion
Completing an EV charger PCB assembly is not
merely about attaching components and performing soldering. We also need to
consider the actual functions that this circuit board is supposed to perform.
The control circuit, power circuit, high current path, and high voltage
isolation area each have different manufacturing requirements, so the assembly
and testing methods also need to be adjusted accordingly.
Before the EV charger PCBA enters production,
we need to confirm the PCB structure, component configuration, assembly
process, and testing requirements in advance. Clearly defining these
requirements in the early stage can reduce rework and adjustments during
production and also facilitate a smoother transition from prototype builds to
mass production for the project.
If you are preparing an EV charger PCB project, PCBasic can assist in reviewing your PCB files, BOM,
assembly and testing requirements before production, and develop corresponding manufacturing
plans based on the actual project needs.
FAQs
Q1: What is the difference between an EV
charger PCB and an EV charger PCBA?
An EV charger PCB
is the bare circuit board, while an EV charger PCBA is the completed board with
components mounted and soldered. EV charger PCB assembly is the process of
assembling those components onto the PCB.
Q2: Does every EV charger PCB require heavy
copper?
No. A heavy copper
PCB is mainly used when higher current-carrying capacity is required. Control
and communication boards may not need heavy copper.
Q3: Why are both SMT and THT used in EV charger
PCB assembly?
SMT is commonly
used for small, high-density components, while THT is suitable for larger
components such as relays and connectors. Many EV charger PCB assembly projects
therefore use both processes.
