Medical Design Briefs - September 2022 - 29

mains and will continue to add more features
to the PCB assembly process.
SMT assembly eases the constraints of
the board space when compared to the
THT assembly method. Through-hole
components require preparations such
as lead bending and trimming before inserting
in the holes. These steps increase
the assembly cost of the PCB. SMDs do
not have leads and are directly soldered
on the surface of the PCB. Higher pin
count packages are also available. However,
SMDs do require advanced assembly
skills and experienced staff to handle
the production line.
SMT assembly is capable of mounting
fine-pitch components, which is not possible
using the THT method. In applications
where space is premium, this SMT
feature is surely the front-runner. With
the SMT assembly process, PCBs that require
a mixed build of both throughhole
and surface-mount components
can be attained. Although SMT reduces
production costs, the capital investment
required on machinery is quite high
compared with the through-hole process.
The THT method is best suited for
applications where the final product is
exposed to continuous vibration or periodic
mechanical stress.
In applications where high-speed circuits
are required, SMT PCBs are the best
choice. Stray capacitance and inductance
issues are reduced in SMT PCBs because
there are fewer holes drilled on the PCB.
The automation of the SMT assembly
method drastically reduces the cost, and a
compact design provides small, lightweight
PCBs. Thus, SMT PCBs are used
extensively in applications such as wearable
consumer products and implantable
medical devices.
SMT assembly has made it possible to
choose flexible substrates for PCB fabrication.
Flex and rigid-flex PCBs are introduced
only because of the SMT assembly
process. The improved efficiency
of PCB assembly is attributable to the
automation of the entire process, which
eliminates the scope of manual errors.
Pick-and-place equipment speeds up assembly
of the PCB and reduces processing
time significantly.
Although SMT assembly offers multiple
advantages in the PCB manufacturing
process, there are few disadvantages
also. Surface mounting is not recommended
for harsh environment applications.
SMDs can easily get damaged in
high-thermal operations. Due to the
dense component placement on an
SMT PCB, there may be insufficient
space for a detailed silkscreen. Manual
debugging and identifying components
for any rework may become complex in
such PCBs.
To decide which assembly technology
is suitable for a given application, it is
essential to consider factors such as the
product usage, the environmental conditions
and stress applied, power requirements
with associated heat dissipation,
performance based on the
com ponent's package, assembly quality
and ease of rework, price benefits, and
component lead time. In most of the
conditions, SMT will be the best option
for PCB assembly.
SMT assembly is widely used in applications
like consumer electronics, mediInnovative
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Medical Design Briefs - September 2022

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