PCB Assembly Equipment: The Ultimate FAQ Guide

I know choosing a suitable PCB assembly equipment can be an overwhelming task.

However, this guide will make everything simple and easy for you.

It explores all the vital PCB assembly equipment you may need.

Take a look:

What Are PCB Assembly Equipment?

PCBs are broadly available in a wide range of gadgets in an ever more digitized and automated society. They’re essential in the mast inconspicuous of devices, from radios and computer systems ensuring smooth operations in several industries.

When manufacturing a large number of PCBs, attaching the components by hand is improbable.

You instead use PCB assembly equipment to allow a more effective and time saving large scale production of PCBs.

Figure 1 PCB Assembly Equipment

PCB assembly equipment encompasses all the tools and machinery you employ in the fabrication and manufacture of PCBs.

The following are some of the assembly equipment you find in production lines:

  • Curing Oven: A curing oven is necessary for solder paste baking and adhesive setting for component attachment.
  • Pick and Place Machine: You have to place the components before the soldering process which you do by using this machine.
  • Reflow Soldering Machine: You employ this machine for reflow soldering of components which you mount on the surface.
  • Repair and Inspection Equipment: Allows you to inspect the board and identify any defects.
  • Solder Paste Screen Printer Machine: You employ this machine in screen printing solder paste to the board.
  • Solvent Cleaning Equipment: This machine is useful when removing residual solder flux after the soldering process.

What Is An SMT Solder Paste Printing Machine?

Applying solder paste to the board is the first stage in PCB assembly.

Solder paste is a gray substance consisting metal alloy particles usually comprising silver, lead and tin you use for component attachment.

It acts as an adhesive, holding the finished board together with components which would otherwise not stick without this paste.

You position a stencil over the board before applying the paste.

You can use a stainless steel panel with perforations as the PCB stencil. You apply solder paste over the stencil on the space allowed for component installation.

Figure 2 SMT solder paste printing machine

The solder paste printing machine allows you to carefully disseminate solder paste on the board.

Solder paste functions as a glue that secures connections on the printed circuit board.

Prior to applying the paste, you position a stencil over the PCB which is usually a panel of stainless steel. This panel has cut out holes identifying board parts you require for component attachment and where you apply the paste.

You hold the stencil and PCB in position in the printer machine during solder paste application.

A dispenser then releases defined amounts of solder paste to the pads while a blade spreads the paste uniformly.

The solder paste features prominently in the desired areas after removal of the stencil.

How Does An SMT Solder Paste Inspection Machine Work?

You find poor or inadequate solder paste printing contributes to a large percentage of difficulties in soldering.

Consequently, it is important and vital to verify the correct and precise printing of solder paste onto the board.

In small scale PCB production, using a reliable printing process for your solder paste is sufficient. However,

large scale PCB production requires use of an inspection machine to avoid significant rework expenses.

A solder paste inspection machine employs cameras that can capture 3D images to assess the solder paste’s quality.

You base the quality on parameters such as the volume of solder, its alignment, and dimension.

Where there’s inconsistency with the set parameters, the machine highlights such allowing you to make corrections.

You can employ automated optical inspection alongside this machine to effectually examine the printing process.

What Configurations Can You Employ With The SMT Solder Paste Printing Machine?

A solder paste printing machine is necessary for the board application of solder paste prior to attachment of components.

You can employ different equipment for solder mask screening given the automation level and board size.

You have three types of solder paste printing systems configuration which can be table top, standalone or in-line.

They include:

  • Manual: You carry out the processes in this machine by hand.
  • Semi-automatic: With this solder paste printing machine, you find some processes automatic with manual execution. For instance, you will find vision alignment capacity is manual.
  • Fully automatic: Here, all the processes are under computer control employing pre-programmed settings including automatic alignment.

What Do You Prefer A Stencil Over A Screen In SMT Printing Machines?

The preference of stencils over screens is down to their higher image precision, volume control, and extended useful life.

Screens find minimal use, however, the most frequent stencil material is stainless steel with brass and molybdenum as other options.

You find chemical etching the most popular method in making stencils.

However, other methods such as electroless nickel plating, electro-polishing, electrodeposition and laser cutting are options when considering pitch.

You can apply solder paste to multiple thicknesses of various SMD component substrate types by employing stepped thickness stencils.

Here, you to ensure the stencil apertures are in perfect alignment with the land patterns for fine pitch printing.

How Do You Employ A Solvent Cleaning Machine?

After soldering, you employ solvent cleaning equipment to eliminate flux residue and contaminants from a circuit board assembly.

You employ solder pastes that are water soluble and fluxes in most large scale productions requiring de-ionized water for cleaning.

Furthermore, using solder pastes with low-residue flux and less cleaning demands is currently common. However, when selecting the solvent cleaning equipment for your PCB, you consider several factors.

The type of flux you employ and the cleanliness requirements influence the solvent and cleaning equipment choice.

Efforts to eradicate chlorofluorocarbons (CFCs) and other ozone-depleting chemicals has shone the light on the cleaning process of PCB assembly.

Currently, you find electronic PCB assemblies employing solder with flux and solder paste types necessitating cleaning after the soldering process.

When using fluxes based on rosin, their insulating nature can transmit gluey substance making them inconsiderable for electrical testing.

Cleaning of military approved fluxes and solder pastes demands military requirements, along with testing for ionic contamination.

Thus, you prevent contamination and damage of the assembly by the excess flux.

You can eliminate rosin flux purely for aesthetic reasons and also as a process before application of a conformal coating.

When you have to employ rosin flux or paste, semi-aqueous blends, specific detergents, and non-ozone depleting solvents are advisable.

Regardless of your choice, your equipment cost depends on the material procurement while alternative solutions require knowledge of the flux type.

In choosing a cleaning technology, consider the manufactured product, performance, environmental impact, and cost.

What Is A Glue Dispensing Machine?

The glue dispensing machine releases bits of glue on the circuit board to hold components prior to soldering of the contacts.

Figure 3 Glue dispensing Machine

This is especially critical during wave soldering, whose wave force can displace larger components and also when executing double-sided soldering.

How Does A Pick-And-Place Machine Work?

After board construction, you have to precisely position the components with a board containing up to thousands of components.

While placement of components was previously manual using tools such as tweezers, today, you employ automatic equipment.

These machines can place many component pieces simultaneously on a board quickly and accurately. The pick-and-place machine is such a machine that picks components up before accurately placing them on the desired board location.

Figure 4 pick and place machine

The pick-and-place machine allows you to conduct this process without exhaustion and at a higher degree of accuracy.

These machines suck up components before arranging them precisely on top of solder lands.

Placement is at breakneck speed, with machines capable of working 30,000 components every hour.

As the most important section of a production line, pick-and-place machines account for around half the overall cost.

You have different machine types with some capable of working a wide component variety and others focused on a few types.

Nonetheless, these machines, on average, are faster, more accurate, and more flexible compared to insertion machines for through-hole components.

What Pick And Place Machines Types Are There?

You find two major types of pick and place machines: fine pitch, usually 0.5 mm, and ultra-fine pitch machines (0.4mm – 0.3mm).

The latter demand more sharpness and accuracy.

You can reduce the damage of leads via rough handling by employing these machines to cut and shape the IC package leads.

As a result, you improve the accuracy of the procedure.

The machines you need to appropriately assemble surface mount components in entirety varies based on various factors.

These include the component type, the board type, and the manufacturing quantity.

You can achieve maximum production by utilizing a dedicated SMT pick and place machine.

You can also employ a robot for component placement with the only limitations resulting from costs of developing software and hardware.

What Machine Do You Use In Drilling PCBs?

PCB drilling refers to the formation of holes and cavities into which you insert through-hole components.

PCB drilling is a mechanical and chemical process where you mechanically drill the board before removing material using electrolytic etching.

You can employ two different machine types in drilling PCBs:

Mechanical Drill

Mechanical drills are less precise but simple to use, employing drill bits of various sizes to achieve desired hole sizes.

You can employ a manual drill or an automatic drill press with achievable diameters capped at about 6 mils.

Figure 5 Mechanical drill

You can achieve about 800 hits for your drill bit before wear when used on soft board materials such as FR4.

However, the count reduces when you use the drills on harder materials such as ceramic.

Laser Drill

You can achieve tiny holes up to 2 mils when employing a laser drill without physical contact with the board.

The laser drill machine employs a laser beam to extract material from the board creating accurate holes.

While you can easily control the drill depth with a laser drill machine, it is an expensive process. Additionally, where you have different board materials, the contrasting optical characteristics makes efficient burn through by the laser beam difficult.

Figure 6 laser drill

How Does The Reflow Soldering Machine Work?

Upon placing all the components, you have to secure them via a soldering process.

Soldering involves melting solder material to create connections with conductive properties between the components and the board.

The most common soldering technique for surface mounted components in PCB assembly is reflow soldering.

After populating the board, you transfer it to a conveyor and through a massive oven you call reflow soldering machine.

Figure 7 Reflow soldering Machine

The solder paste melts and hardens as it passes through several zones set at delicately controlled temperatures.

As a result, it makes formidable electrical connections between the boards and components via the pads.

Movement of the PCB in the reflow soldering machine is by a conveyor system.

Inside the machine, preheating, melting, wetting, drying and cooling of the solder paste takes place securing the components to the board.

The key aspect of reflow soldering is using an external heat source to melt the solder.

The melted solder flows and enters the pads to conclude the circuit board’s soldering operation.

What Are The Types Of Reflow Soldering Machine?

In surface mount technology, there are a variety of reflow soldering procedures, each with its own set of benefits and drawbacks.

Some of the most important decision variables are the cost of the equipment, the cost of maintenance, and the yield.

The following are the most often used reflow soldering procedures in PCB assembly:

Vapor Phase

The vapor phase technique is extremely adaptable, allowing use in any assembly type but at greater operating expense than the infrared process.

Figure 8 vapor phase reflow soldering machine

You can employ many phase process models for both batch and in-line formats.

Infrared

The infrared type finds common use firing heavy ceramic film deposits, but at a considerably greater temperature.

Before, you could use the same equipment for reflow soldering when handling substrates of glass epoxy. The results were however disastrous with burning of the board, charring and warpage taking place.

What Are The Zones In The Reflow Oven?

You find the following zones in the reflow oven:

  • Preheat Zone: This is the foremost zone where you subject the board assembly to temperature rise slowly but evenly.

You avoid cracks resulting from thermal shock as a result.

  • Thermal Soak Zone: The temperature level in this zone is such that it melts the solder paste securing the leads to the board pads.
  • Reflow Zone: Also the “time above reflow”, it’s where you achieve the machine’s maximum temperature.

The nature of components’ on the PCB and the board’s thermal resistance capability determine the peak temperature value.

  • Cooling Zone: Refers to the ultimate zone where cooling of the PCB assembly is steady allowing solder joints’ solidification.

Figure 9 Reflow oven

What Are The Advantages Of Using A Reflow Soldering Machine?

You find employing the reflow soldering machine beneficial in the following manner:

Better Suited To Complex Assembly

Reflow soldering is specific to surface mount technology where it satisfies the demands of challenging assembly.

Reflow soldering is the only way you can fashion components such as the QFN and BGA.

Excellent Weld Quality

The reflow oven employs hot air in the process to initiate convection and conduction.

You achieve a consistent temperature, excellent soldering quality, and a highly desirable soldering effect.

You Can Mass-Produce

Reflow soldering has a high soldering efficiency.

You can copy the soldering parameters indeterminately upon establishing a desired temperature making it ideal for mass manufacturing.

How Does The Wave Soldering Machine Function?

A wave soldering machine derives its name from the soldering process where you traverse the board assembly through a hot solder wave.

You apply a flux layer over the component leads and solder lands as a cleaning procedure ensuring proper adherence.

A preheating process follows the application of flux to avert thermal shock.

You then traverse the board through a molten solder containment where it interacts with a wave of solder.

The solder wave joins the component contacts to the solder pads on the board.

Compared to reflow soldering, wave soldering finds less common use due to many board components being SMT.

Wave soldering is specific to through-hole components.

With wave soldering, the board’s contact time at high temperature is short reducing occurrence of warpage.

Additionally, the process is sufficiently effective resulting in solder joins of great quality.

What Equipment Do You Employ In PCB Testing?

Manufacturers must ensure there are no defective parts on the PCB and that the board functions according to design.

An inspection of the board is therefore necessary as well as testing for performance issues such as disrupted electrical connections.

Automated Optical Inspection (AOI)

An AOI system uncovers initial flaws in the manufacturing process.

It takes pictures of the board surface using HD cameras creating images for examination.

You compare these images with the reference board design identifying any deviations and disparities. This machine can highlight missing components, incorrect placements, shorts and even abrasion marks.

In-Circuit Testing (ICT) Machine

This machine entails a fixture known as ‘bed of nails’ made up of pogo pins with spring-loads.

In their configuration, each pin makes contact with a node on the PCB’s circuitry.

You position complete PCBs on these pins before subjecting them under a press allowing connection of several test points simultaneously.

The bed of nails transports the board’s test signals via these connections assessing functionality and unearthing electrical breaches in continuity.

Boards examined this way may have minor indentations at the points of connection where the nails make contact.

It is a positive indicator however, as it suggests thoroughness of the investigation process of the board.

What Through-Hole Soldering Equipment Do You Need?

When working on a PCB employing through-hole technology, the following equipment are handy:

Wave Soldering Machine: This is the most important machine consisting of several sections as follows: belt conveyor, flux sprayer and preheating pad.

It also has a molten solder container that generates the wave of solder via pump action.

Solder Pot: This machine shares the operation principal of the wave soldering machine but at a reduced scale.

It is simply a container with molten solder allowing you to perform dip soldering.

Can You Employ Manual Equipment In PCB Assembly?

Yes, you can.

You find manual equipment useful for small-scale manufacturing and repair procedures.

The following are some of the most important tools and equipment.

  • Blower for Hot Air
  • ESD Protection and Prevention Tools
  • Iron and Soldering Station
  • Microscope and Magnifying Lamp
  • Pliers and Cutters
  • Screwdrivers
  • Soldering Machine of Soldering
  • Soldering materials including solder wire, solder paste, and flux.

When Do You Employ The SMT Baking Oven?

In surface mount technology, the baking or curing oven finds use in the soldering process of components.

Passing the PCB assembly through the baking oven preheats the solder paste, before melting, wetting and finally drying.

You employ the SMT baking oven on three surface mounting types: Type I, Type II, and Type III.

When conducting the solder process for Type I and Type II, curing in an oven minimizes solder flaws.

Additionally, for Type III SMD components, curing in a baking oven is an essential pre-process before the soldering process.

Figure 10 SMT baking Oven

You need a baking oven to undertake adhesive curing and solder paste baking which can happen in the same or different ovens.

When using a convection or infrared oven, you do not need separate baking ovens for both solder paste baking and adhesive curing.

You can undertake both processes in addition to the main reflow soldering using the same oven.

The volume needed determines whether or not you combine adhesive curing, solder reflow, and solder paste baking, in the same oven.

It also signifies that you have chosen convection method over alternative methods like convection belt soldering, laser soldering, or vapor phase.

Convection ovens find more use when working with surface mounted components presently, than any other oven type.

What PCB Repair Equipment Can You Employ?

Repair equipment when removing and replacing electronic components entails assembly tools and equipment employing conductive tips or blower (hot air).

Tools with conductive capability such as attachments for soldering iron are very affordable.

There are different tips taking various forms, sizes, and designs to fit a variety of through-hole and SMD components.

Their utility is however limited, but other such tips called composite tips, featuring built-in heating components are available at higher prices.

Such a tip can have digital temperature control with a safety make up against electrostatic discharge during the soldering process.

You also find rework stations employing hot air via nozzles of various diameters for different components at greater cost.

Using this machine ensures damage-free repair making it ideal for surface mounting and BGA rework and repair.

You also find in-line systems for repair and rework available albeit at high costs.

However, repair equipment may be manual and not automated unless you go for premium systems built for high volume work.

Additionally, even when undertaking large scale repair, you don’t need to employ automated repair equipment.

Rather, you should closely monitor the process to minimize the rate of failure.

For all your PCB assembly equipment, contact Venture electronics now.

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