We all know that different
components are needed when an electronic product is expected to allow complex
functions. Such as the smart phone used daily. There are always parts like
chip, battery, camera module connected to a PCB within a device. While
difference between these components can lead to different ways of assembly. As
with a cellphone’s assembly, chips are mounted directly onto the PCB. Larger,
discrete units like the camera or battery, in contrast, require a connection to
the main board through dedicated flex cables. Given their differing form factors and connection
requirement, PCB assembly often needs a mixed-technology approach. Mixed
technology PCB assembly is not only about surface mount technology and
through-hole assembly. In many cases, the board may also go through selective
soldering, wave soldering, manual soldering, inspection, cleaning, and
functional testing.
In the PCBA industry, mixed technology PCBs are typically used in complicated
products, requiring both compact circuit design and strong mechanical
connections, which can place higher demands on the assembly process and the
full production workflow. So, for buyers, choosing the right PCBA manufacturer
can make the project much easier to manage. In the following sections, you will
learn the key details of mixed technology PCB assembly and how to use these
details to evaluate and select a suitable manufacturing partner.
What Is Mixed Technology PCB Assembly?
Mixed technology PCB assembly refers to a PCB assembly process that
combines different component mounting methods on the same printed circuit
board. The most common combination is SMT assembly plus through-hole assembly.
Surface Mount Technology in Mixed Assembly
Surface mount technology, or SMT, is used for
components mounted directly onto the surface of the PCB. These components are
usually small, lightweight, and suitable for automated production.
Common SMT components include:
Resistors, capacitors, diodes, ICs, QFNs, BGAs, SOT packages, LEDs,
and small connectors.
The SMT process usually includes solder paste printing, SPI
inspection, pick-and-place, reflow soldering, and AOI inspection. In a
professional PCBA factory, SMT equipment such as JUKI
pick-and-place machines, solder paste printers, SPI systems, reflow ovens, and
AOI machines helps ensure placement accuracy and soldering consistency.
Through-Hole Technology in Mixed Assembly
Through-hole technology is used for components with leads inserted
into plated holes on the PCB. These components are often larger and stronger
than SMT components.
Common through-hole components include:
Terminal blocks, transformers, relays, large capacitors, pin
headers, connectors, switches, and high-current components.
Through-hole parts are often used when the product needs better
mechanical strength, higher current capacity, or stronger reliability under
vibration and stress. This is why many industrial, automotive, and
power-related PCBAs still require through-hole assembly.
Manual Soldering and Selective Soldering
Even when a factory has wave soldering and selective soldering
equipment, manual soldering is still important in mixed technology PCB
assembly. Some components are heat-sensitive, irregular in shape, too close to
other parts, or unsuitable for automated soldering.
This is also why a skilled post-soldering team is still necessary.
Machines improve efficiency, but trained operators solve special process
problems and handle exceptions that equipment cannot fully cover.
Why Mixed Technology PCB Assembly Is Widely Used
Mixed technology PCB assembly is widely used because electronic
products need both high-density design and strong physical connections.
Higher Circuit Density
SMT components allow engineers to design smaller and more complex
circuit boards. This is important for smart devices, communication products,
control boards, and compact electronic modules.
Better Mechanical Strength
Through-hole components provide stronger solder joints and better
mechanical support. For connectors, switches, power terminals, and heavy
components, through-hole assembly is often more reliable than SMT.
More Flexible Product Design
Many products need different types of components on one board. For
example, a medical control board may include small ICs, sensors, connectors,
relays, and power components. A mixed assembly process allows engineers to
choose the most suitable package for each function.
Better Reliability for Demanding Applications
Industrial and medical PCBAs often face vibration, heat, humidity,
long operating time, and strict reliability requirements. Mixed technology can
help balance electrical performance, mechanical strength, and product
durability.
Key Challenges in Mixed Technology PCB Assembly
Mixed technology PCB assembly is more complex than standard SMT
assembly. The difficulty is not only in the soldering process, but also in
production planning and process control.
Process Sequence Control
A mixed technology PCBA may go through multiple production steps,
including SMT, reflow, AOI, through-hole insertion, wave soldering, selective
soldering, manual soldering, cleaning, testing, and final inspection.
If the sequence is wrong, components may be damaged, solder joints
may be affected, or rework may increase. For example, heat-sensitive components
must be protected from excessive temperature. Large through-hole parts may
block AOI inspection if they are inserted too early.
A professional manufacturer should review the BOM, Gerber files,
component drawings, polarity requirements, soldering method, and inspection
plan before production starts.
Solder Joint Quality Control
Different soldering methods bring different risks. SMT solder
defects may include solder bridges, tombstoning, insufficient solder, component
shift, polarity errors, and BGA soldering issues. Through-hole defects may
include poor hole fill, cold solder joints, bridging, excessive solder, and
weak wetting.
That is why mixed technology PCB assembly requires inspection at
different stages instead of relying only on final testing.
Component and Material Management
Mixed technology PCBAs often involve many component types and
packaging forms. Before production, the factory must check material quantity,
MSL level, polarity, component value, package type, and BOM consistency.
For example, reel components can be counted by X-ray counting
equipment, while loose components can be checked by weighing. These small
details help reduce material shortage risks and avoid production interruption.
Manual Operation Consistency
Manual soldering and post-soldering work must be controlled by clear
standards. Without training and process instructions, different operators may
produce different soldering quality.
This is why employee training, production discipline, and stable
teams directly affect PCBA quality. Human-centered management is not only
company culture. In manufacturing, it also supports quality consistency.
Inspection and Testing for Mixed Technology PCB Assembly
A reliable mixed technology PCB assembly process needs inspection
before, during, and after production.
SPI Inspection
SPI, or solder paste inspection, is performed after solder paste
printing. It checks solder paste volume, height, area, and offset.
This step is important because many SMT defects start from poor
solder paste printing. If solder paste problems are detected early, the factory
can fix them before components are placed.
AOI Inspection
AOI, or automated optical inspection, is usually performed after
reflow soldering. It checks visible defects such as missing components, wrong
direction, component shift, solder bridges, and insufficient solder.
For high-mix, small-batch, and prototype production, offline AOI can
be especially useful because inspection programs need to change frequently. For
stable batch production, inline AOI helps improve speed and consistency.
X-Ray Inspection
Some solder joints cannot be checked by AOI because they are hidden
under the component body. BGA, QFN, and other bottom-terminated components
usually require X-ray inspection.
X-ray can help detect hidden solder bridges, voids, insufficient
solder, and solder ball problems. For mixed technology PCB assembly with BGA
components, X-ray inspection is a key quality control step.
ICT, Flying Probe, and FCT
Electrical testing should be selected according to product stage and
order volume.
Flying probe testing is suitable for prototypes, small batches, and
products that may still change. It does not require a dedicated fixture, so it
is flexible.
ICT is more suitable for stable designs and batch production. It
checks electrical connections and component parameters through a fixture.
FCT, or functional testing, simulates real product operation. For
some projects, an in-house FCT test platform can greatly improve testing
efficiency. For example, customized functional test systems can reduce long
manual testing time and improve data consistency.
However, testing should not be the only quality strategy. ICT,
flying probe, and FCT are filters, not complete error-proofing systems. Real
reliability comes from process control before defects reach the testing stage.
Traceability and MES Control in Mixed Technology PCB Assembly
Traceability is very important for mixed technology PCB assembly
because the process involves many steps, materials, operators, and inspection
points.
MES System for Production Control
A strong MES system can connect work orders, material information,
process instructions, inspection records, testing data, and production status.
For complex mixed technology PCBAs, operators should not rely only
on memory or verbal instructions. Special process requirements should be
displayed clearly before production starts. This helps reduce mistakes caused
by BOM changes, customer notes, engineering updates, or special soldering
requirements.
PDA Scanning and Production Records
PDA scanning can connect production actions and photos with customer
orders. For example, packaging photos or process records can be uploaded and
linked to the order. This improves transparency and helps with after-sales
analysis if a quality issue occurs.
For buyers, this kind of traceability means better control, better
communication, and lower risk.
How to Choose a Mixed Technology PCB Assembly Manufacturer
When choosing a mixed technology PCB assembly manufacturer, buyers
should not only compare price. They should evaluate the factory’s full
manufacturing capability.
Check Certifications and Compliance
For medical electronics, ISO 13485 is an important certification
because it shows stronger quality management requirements for medical-related
manufacturing. For other industries, buyers should also check whether the
manufacturer has relevant quality systems and compliance experience.
Ask About Equipment and Materials
Good equipment and stable materials help improve process
consistency. Buyers can ask whether the factory uses reliable SMT equipment,
solder paste brands such as Alpha, AOI, SPI, X-ray inspection, reflow ovens,
wave soldering, and selective soldering equipment.
Equipment does not guarantee quality by itself, but it shows whether
the manufacturer has the basic capability to handle complex PCBA projects.
Evaluate Engineering and Innovation Ability
A strong PCBA manufacturer should not only follow instructions. It
should also be able to solve manufacturing problems.
For example, patents related to first-article inspection devices,
MES system improvements, or production efficiency tools can show that a factory
has practical innovation ability. These improvements often come from real
production pain points.
Compare Cost and Long-Term Value
Compared with manufacturing in higher-cost regions such as the
United States, China-based PCBA manufacturers can often provide better
cost-effectiveness. However, buyers should not choose only the lowest price.
A better choice is a manufacturer that can balance cost, quality,
lead time, inspection capability, and engineering support.
Confirm Lead Time and Delivery Certainty
For mixed technology PCB assembly, delivery risk may come from
material shortage, process waiting time, manual soldering capacity, testing
bottlenecks, or rework.
A reliable manufacturer should have clear production planning,
material checking, MES tracking, and stable delivery control. Fast delivery is
important, but delivery certainty is more important.
Mixed Technology PCB Assembly at PCBasic
PCBasic provides mixed technology PCB assembly services for
customers who need SMT assembly, through-hole assembly, testing, traceability,
and one-stop PCBA manufacturing support.
The value of PCBasic is not only component soldering. It comes from
complete process control, including material inspection, SMT production, SPI,
AOI, X-ray inspection, through-hole assembly, functional testing, MES
traceability, cleaning, final inspection, and packaging.
For high-reliability projects, PCBasic can support additional
process requirements such as deionized water PCBA cleaning and protective
packaging. For special boards, multi-layer protection such as bubble bag, ESD
bag, and outer cushioning can help reduce static and transportation risks.
PCBasic also emphasizes continuous improvement. Patents, internal
MES development, first-article inspection improvement, and production
efficiency optimization reflect the company’s ability to solve real
manufacturing problems. At the same time, staff training, welfare, incentive
systems, and human-centered management help maintain a stable production team
and consistent workmanship.
For buyers looking for mixed technology PCB assembly, PCBasic can be
a suitable partner for projects that require cost-effectiveness, quality
control, delivery certainty, and engineering support.
Conclusion
Mixed technology PCB assembly is more than combining SMT and
through-hole components on one board. It is a complete manufacturing process
that requires careful control of materials, soldering sequence, inspection
methods, testing strategy, traceability, and delivery management.
For buyers, the right PCBA manufacturer should provide more than a
low quotation. It should have suitable equipment, trained operators, strong
inspection capability, reliable MES traceability, clear engineering support,
and stable delivery control.
As electronic products become more complex, mixed technology PCB
assembly will continue to play an important role in industrial, medical,
automotive, communication, power, and IoT applications. Choosing an experienced
PCBA manufacturer can help reduce risk, improve reliability, and support
long-term product success.
FAQ
What does mixed technology PCB assembly mean?
Mixed technology PCB assembly means using more than one assembly
method on the same PCB. It usually combines SMT assembly and through-hole
assembly, and may also include wave soldering, selective soldering, manual
soldering, AOI, X-ray inspection, ICT, flying probe testing, and FCT.
Is mixed technology PCB assembly more expensive than SMT assembly?
Usually, yes. Mixed technology PCB assembly may require more process
steps, more manual work, more inspection, and more testing. However, the cost
depends on board complexity, component types, order volume, testing
requirements, and lead time.
Why are through-hole components still used in modern PCB assembly?
Through-hole components are still used because they provide stronger
mechanical support and better reliability for connectors, terminals, relays,
transformers, switches, and high-current components. Many industrial and power
products still need through-hole parts.
What inspection methods are used for mixed technology PCB assembly?
Common inspection methods include SPI, AOI, X-ray inspection, manual
visual inspection, ICT, flying probe testing, and FCT. The right inspection
plan depends on component type, board complexity, and product reliability
requirements.
How do I choose a reliable mixed technology PCB assembly
manufacturer?
You should evaluate the manufacturer’s SMT and through-hole
capability, equipment, inspection methods, testing ability, certifications, MES
traceability, engineering support, lead time control, and experience with
similar products. For medical projects, certifications such as ISO 13485 are
especially important.
