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FR-4 lead free
Finished board side
Min.drilled hole size
HALS/HALS lead free
Solder mask color
Vacuum packing,Plastic bag
Standard carton packing
Providing OEM service to all sorts of printed circuit board
There are two types of mounting technologies are prevailing in the
modern PCBA industry:
Surface Mount Technology: Sensitive components, some very small,
such as resistors or diodes are placed automatically onto the
surface of board. This is called SMD assembly, for surface mount
device. Surface mount technology can be applied on small size
components and integrated circuits (ICs). For example, PCBCart is
capable of mounting package with min. size 01005, which is even
smaller than the size of a pencil point.
Thru-Hole Technology: works well on components with leads or wires
that have to be mounted on board by plugging them through holes on
board. The extra lead part has to be soldered on the other side of
the board. This technology is applied on PCB assemblies containing
large components such as capacitors, coils to be assembled.
Step 1: Solder Paste Stenciling
The first step of PCB assembly is applying a solder paste to the
board. This process is like screen-printing a shirt, except instead
of a mask, a thin, stainless-steel stencil is placed over the PCB.
This allows assemblers to apply solder paste only to certain parts
of the would-be PCB. These parts are where components will sit in
the finished PCB.
The solder paste itself is a greyish substance consisting of tiny
balls of metal, also known as solder. The composition of these tiny
metal balls is 96.5% tin, 3% silver and 0.5% copper. The solder
paste mixes solder with a flux, which is a chemical designed help
the solder melt and bond to a surface. Solder paste appears as a
grey paste and must be applied to the board at exactly the right
places and in precisely the right amounts.
In a professional PCBA line, a mechanical fixture holds the PCB and
solder stencil in place. An applicator then places solder paste on
the intended areas in precise amounts. The machine then spreads the
paste across the stencil, applying it evenly to every open area.
After removing the stencil, the solder paste remains in the
Step 2: Pick and Place
After applying the solder paste to the PCB board, the PCBA process
moves on to the pick and place machine, a robotic device places
surface mount components, or SMDs, on a prepared PCB. SMDs account
for most non-connector components on PCBs today. These SMDs are
then soldered on to the surface of the board in the next step of
Traditionally, this was a manual process done with a pair of
tweezers, in which assemblers had to pick and place components by
hand. These days, thankfully, this step is an automated process
among PCB manufacturers. This shift occurred largely because
machines tend to be more accurate and more consistent than humans.
While humans can work quickly, fatigue and eyestrain tends to set
in after a few hours working with such small components. Machines
work around the clock without such fatigue.
The device starts the pick and place process by picking up a PCB
board with a vacuum grip and moving it to the pick and place
station. The robot then orients the PCB at the station and begins
applying the SMTs to the PCB surface. These components are placed
on top of the soldering paste in preprogrammed locations.
Step 3: Reflow Soldering
Once the solder paste and surface mount components are all in
place, they need to remain there. This means the solder paste needs
to solidify, adhering components to the board. PCB assembly
accomplishes this through a process called "reflow".
After the pick and place process concludes, the PCB board is
transferred to a conveyor belt. This conveyor belt moves through a
large reflow oven, which is somewhat like a commercial pizza oven.
This oven consists of a series of heaters which gradually heat the
board to temperatures around 250 degrees Celsius, or 480 degrees
Fahrenheit. This is hot enough to melt the solder in the solder
Once the solder melts, the PCB continues to move through the oven.
It passes through a series of cooler heaters, which allows the
melted solder to cool and solidify in a controlled manner. This
creates a permanent solder joint to connect the SMDs to the PCB.
Many PCBAs require special consideration during reflow, especially
for two-sided PCB Assembly. Two-sided PCB assembly need stenciling
and reflowing each side separately. First, the side with fewer and
smaller parts is stenciled, placed and reflowed, followed by the
Step 4: Inspection and Quality Control
Once the surface mount components are soldered in place after the
reflow process, which doesn't stand for completion of PCBA and the
assembled board needs to be tested for functionality. Often,
movement during the reflow process will result in poor connection
quality or a complete lack of a connection. Shorts are also a
common side effect of this movement, as misplaced components can
sometimes connect portions of the circuit that should not connect.
Step 5: Through-Hole Component Insertion
Depending on the type of board under PCBA, the board may include a
variety of components beyond the usual SMDs. These include plated
through-hole components, or PTH components.
A plated through-hole is a hole in the PCB that's plated all the
way through the board. PCB components use these holes to pass a
signal from one side of the board to the other. In this case,
soldering paste won't do any good, as the paste will run straight
through the hole without a chance to adhere.
Instead of soldering paste, PTH components require a more
specialized kind of soldering method in later PCB assembly process:
• Manual Soldering: Manual through-hole insertion is a
straightforward process. Typically, one person at a single station
will be tasked with inserting one component into a designated PTH.
Once they're finished, the board is transferred to the next
station, where another person is working on inserting a different
component. The cycle continues for each PTH that needs to be
outfitted. This can be a lengthy process, depending on how many PTH
components need to be inserted during one cycle of PCBA. Most
companies specifically try to avoid designing with PTH components
for this very purpose, but PTH components are still common among
• Wave Soldering: Wave soldering is the automated version of manual
soldering, but involves a very different process. Once the PTH
component is put in place, the board is put on yet another conveyor
belt. This time, the conveyor belt runs through a specialized oven
where a wave of molten solder washes over the bottom of the board.
This solders all of the pins on the bottom of the board at once.
This kind of soldering is nearly impossible for double-sided PCBs,
as soldering the entire PCB side would render any delicate
electronic components useless.
After this soldering process is finished, the PCB can move on to
the final inspection, or it can run through the previous steps if
the PCB needs additional parts added or another side assembled.
Step 6: Final Inspection and Functional Test
After the soldering step of the PCBA process is finished, a final
inspection will test the PCB for its functionality. This inspection
is known as a "functional test". The test puts the PCB through its
paces, simulating the normal circumstances in which the PCB will
operate. Power and simulated signals run through the PCB in this
test while testers monitor the PCB's electrical characteristics.