PCB Assembly Machine: The Machines Required for Professional Assembly

PCB assembly is as delicate of a process as circuit board fabrication. So assemblers need high-tech PCB assembly machine to mount and weld components on the board to make the circuit function as required. 

The assembly process has several stages, and each one needs several devices. We’ll categorize the machines by the PCB processes below, so read on to learn more!

Solder Paste Application

You need two machines for the solder paste application step to weld SMT devices.

Solder Paste Printing Machine

Also known as a stencil printer, this machine applies solder paste to the PCB via a stencil screen. The paste, a gray-colored slimy substance, contains flux and tiny metal-alloy balls.

Solder paste printing machines apply this paste using squeegees, which push the material through the stencil holes to specific areas on the board.

A high-precision automatic solder paste printer

A high-precision automatic solder paste printer

The machine fixes the PCB and stencil in position before applying the paste to ensure precise application.

Solder Paste Inspection Machine

Although the paste printing process has the element of high precision, you need a solder paste inspection machine to detect errors.

Roughly 70% of surface-mount technology issues arise from inaccurate or substandard solder paste applications. So the inspection is necessary, especially in producing higher volumes of PCBs to reduce rework.

The machine uses cameras to capture high-resolution 3D images to assess factors like solder height, volume, and alignment. If it detects any issues, it will raise an alert. 

Electronic Component Placement

The PCB heads to the automated component placement step after the precise solder paste application. This process requires the following machines.

Glue Dispensing Machine

Before surface-mount component placement, you need adhesive to hold the parts during soldering. This machine dispenses tiny glue dots on the board where the electronic components will sit.

The glue holds the components in place until the contacts get soldered to the pads. And if the board has thru-hole parts, the adhesive will secure them until the pins/leads get soldered.

Wave soldering for thru-hole components applies more pressure to the leads and can push the pieces out of place. So this glue is especially vital for thru-hole parts.

Pick-and-Place Machine

Also known as a surface-mount machine, this equipment picks SMT components from their packages, then places them above the applied solder paste.

The machines can place up to 30,000 components per hour and usually have several feeds to pick parts from multiple reels.

An automatic pick-and-place machine

An automatic pick-and-place machine

Older placement methods were manual, and this process transitioned from manual pick-and-place machines to semi-automatic to automatic.

For through-hole component insertion, the process can be manual or require robots.


After placing the components, use these machines to complete the soldering process.

Reflow Oven

Reflow soldering machines are ovens that heat and melt the solder paste under SMT components.

They have several zones to pre-heat, heat, and cool the board at controlled temperatures to create perfect electrical and mechanical bonds.

Circuit boards in an infrared reflow oven

Circuit boards in an infrared reflow oven

The machines also have conveyor belts for moving boards through the different temperature zones.

Wave Soldering Machine

It is impossible to solder through hole components using the solder reflow method; the molten solder will flow through the holes. The best way to weld these parts is using a wave soldering machine.

The device contains a bath of molten solder, which it agitates to create a wave of hot liquid. PCBs pass above the liquid metal at a height that the solder wave can contact the underside.

The molten metal attaches to the metal points (component leads and plated-through holes) but bounces off the other parts.

Manual insertion of through-hole components in PCBs on an assembly line before wave soldering

Manual insertion of through-hole components in PCBs on an assembly line before wave soldering

But these machines are becoming increasingly unpopular because the heat from the molten solder can damage sensitive surface-mount components. So assemblers have transitioned to selective soldering.

Selective Soldering Machine

Selective soldering only welds specific spots on the board that require through-hole assembly. Assemblers have the option of using either of the following.

  • Selective aperture tools
  • Selective dip solder fountains
  • Laser soldering machines
  • Robotic soldering irons
  • Hot gas induction soldering
  • Miniature wave solder fountains
Selective soldering using robotic soldering irons

Selective soldering using robotic soldering irons

Solder Pot

Solder pots are like small-scale versions of wave soldering machines. They are suitable for Dip soldering in small PCB assemblies, such as when producing LED bulb PCBs.

A soldering machine pot

A soldering machine pot

Solvent Cleaning Equipment

Although machines apply solder paste and control the soldering process, it is not always neat. Excess solder and flux can remain on the surface.

Flux is acidic and can corrode the board. On the other hand, excess solder can create unwanted connections, leading to short-circuiting.

Solvent cleaners remove these elements immediately after soldering to prevent damage later.

Conveyors and Handling Equipment

Machines like reflow ovens have conveyors to move the boards internally through the different heat zones. But external conveyors and handling equipment to move the PCBa across the assembly machines.

Conveyor belts in a PCB assembly factory

Conveyor belts in a PCB assembly factory

These machines enhance production efficiency and cut costs along the assembly line.

Inspection Machines

Inspection machines check the assembled boards to determine if they meet the customer’s requirements and assembly standards. They include the following.

Automated Optical Inspection Machine

Manual inspection using your eyes won’t cut it for modern PCB assemblies. Plus, it is slow. So AOI machines are necessary for mass production inspection to ensure consistent quality.

They resemble solder paste inspection machines because they use high-resolution cameras to capture board images for analysis. The equipment compares the captured image with a correct reference board image in the system for analysis.

An automated optical inspection device (vision measuring instrument) checking a circuit board

An automated optical inspection device (vision measuring instrument) checking a circuit board

So the machine can detect missing components, incorrect positioning, scratches, shorts, and other defects.

In-Circuit Testing (ICT) Machine

Also known as the bed of nails test, ICT testing involves using multiple spring-loaded pogo pins to inject current and test the board’s functionality.

Each board gets placed above the “bed of nails, where the pin positioning matches PCB contact points.

The board reliably contacts the pins for test signal transmission when pressed down. So if there are any shorts or discontinuities, the machine will find them.

The pogo pins are sharp and can create tiny dimples on the solder joints. So you might notice these dents on the board on delivery, and should be no cause for alarm.

Functional Validation Test (FVT) Equipment

These machines determine if the PCBs are good enough for shipping to the client because they load firmware into the board’s chip. After that, they check if the PCB functions as it should for its respective application.

One of the most popular functional tests is the hot mock-up, which simulates the operational environment of the end product. 

Rework Machine

If you detect faults when testing the boards, you need to repair the specific sections using rework stations.

The equipment primarily includes desoldering and re-soldering tools for removing and re-installing misbehaving or misaligned SMT components. Most rework stations are for re-mounting BGA components.

A BGA rework station

A BGA rework station

Coating Equipment

This process is not compulsory for all circuit boards, but it protects the circuits from environmental factors like dust and moisture. It requires these two machines.

Conformal Coating Machines

Conformal coating machines apply thin polymeric layers above printed circuit boards that conform to the board’s contours, hence the name.

The application can be via dip coating, brushing, dispensing, or spraying. And the polymer material can be silicon, acrylic, perylene, or urethane.

A PCB conformal coating machine

A PCB conformal coating machine

Curing Machines

This machine takes over after conformal coating application to cure the polymeric layer. Hot-air curing machines are typical in the industry, but their UV counterparts have the fastest curing times.

Wrap Up

As you can see, the assembly process involves multiple steps, and each stage requires at least one piece of assembly equipment. 

So you should set aside a significant sum to build a PCB assembly line. Or you can contact us to assemble your boards because we have all these machines. 

So contact us today with your circuit designs. We can do both fabrication and assembly at reasonable prices.