SMT Manufacturing: The Ultimate FAQ Guide

I know you’re probably wondering what SMT manufacturing is all about.

Well, this guide explores everything about SMT manufacturing.

So, keep reading to learn more.

What Is SMT Manufacturing?

SMT [Surface-mount technology] manufacturing is a process of directly soldering electrical parts directly on the surface of PCBs [Printed Circuit Boards].

The electronic part you will mount via SMT manufacturing is known as SMD [surface mount device].

SMT manufacturing is proving to be simple, cost-effective, and efficient since you will not pass leads through the printed circuit boards.

SMT manufacturering

SMT manufacturing

What Is The Process Behind SMT Manufacturing?

Here are the steps you will undertake when performing SMT manufacturing:

Design Of The PCB

The first step when conducting SMT manufacturing begins by designing and preparing the layout for the printed circuit board.

It entails working with the layout of the SMT printed circuit boards using various CAD package software.

Some of the software you can use include EagleCAD, KiCAD, EasyEDA, TinyCAD, etc.

File Preparation

This phase entails preparing the basic PCB files to make sure the SMT manufacturing process occurs smoothly.

Also, you will set up the machines necessary for the SMT manufacturing process.

Examples of SMT printed circuit boards manufacturing includes the following:

1. BoM file

Bill of Materials [BoM] is a list containing all the electronic parts that you will use in SMT manufacturing during PCB layout.

2. Gerber files

This file contains vital information about your PCB.

Examples of the information include spacing information, PCB layout information, tracks, layer information, etc.

3. PNP or CPL files

Pick and Place [PNP] or Component Placement List [CPL] are important as machines use them to determine the exact placement of electronic components.

Examination Of PCB Material

This phase entails the examination of surface-mount components and the printed circuit board.

It entails determining if the PCB design has any errors or flaws.

Besides evaluating the materials, you will also prepare the PCB stencils.

Stencils will offer an accurate position when conducting solder paste printing.

The technicians will produce the stencils in relation to the position of solder pads within the design of the SMT PCB design.

Printing Solder Paste

Solder paste is normally a mixture of tin and flux.

In this phase, you will use solder paste to connect surface-mount components and solder pads on printed circuit boards.

Besides, squeegees and stencils will assist you in this process.

Solder paste printing is a popular method when conducting solder paste printing.

However, jet printing is gaining popularity in large-scale SMT manufacturing processes.

Placement Of SMC Parts

Several SMT manufacturing processes entail the use of pick and place machines.

These machines use gripper nozzles or vacuum systems to pick and place the electronic components in exact locations on the PCBs.

Besides, this machine operates at a high speed and with high accuracy.

Thereafter, printed circuit boards pass via pre-reflow automated optical inspection [AOI] machines.

The inspection phase makes sure that all parts are securely and accurately placed on the PCB before conducting reflow soldering.

Reflow Soldering

In this state, you will pass the SMT PCB through a reflow soldering process.

The machine will form all solder connections between the PCB and the surface-mount components.

This process occurs as the machine heats the whole assembly to suitable temperature levels.

Automated Optical Inspection After The Reflow Process

Once you complete the reflow soldering process, the PCB undergoes a second automated optical inspection.

This is to ensure no errors exist following the reflow soldering process.

It will also determine if you have good quality solder joints.

Cleaning

This is the last stage you will perform during SMT manufacturing.

It entails using wipes with iso-propyl alcohol to eliminate residues from the printed circuit boards.

Which Industries Will Apply SMT Manufacturing?

The trend in electronic products is to make them comfortable, fashionable, smart, and simple to carry.

Besides, as the electronic components get tinier, they need to be intelligent and functional.

Here are some fields that employ SMT manufacturing:

Semi-conductor Industries

In the past, SMT manufacturing and semiconductors were independent but are being integrated into the modern world.

Advanced packing technologies are integrating the production of semiconductors and SMT manufacturing.

Semiconductor packaging industries are adopting SMT manufacturing when mounting passive parts.

Thereafter, they use semiconductor die bonds when mounting die for complete SIP manufacturing.

LED Light Industries

There are many LED products around us and LED lighting industries are adopting SMT manufacturing.

Besides, you will use the LEDs in street lights, LED panels, strip lights, etc.

Furthermore, they are affordable and energy-saving.

Automotive Electronic Industries

More electronic products are getting electronic as the works is continually advancing.

Also, the living standards of many people are improving thereby many families are acquiring cars for their daily usage.

Besides, cars are getting more intelligent.

Electronic systems in automobiles find their application in radio, entertainment units, telematics, etc.

Several automotive industries are applying SMT manufacturing to produce smooth mass production processes.

Besides, SMT manufacturing assists in saving costs while improving the quality of cars.

Home And Work Smart Industries

Several industries are using SMT manufacturing to produce intelligent home control units like burglar alarm systems, gas leakage units, intelligent lighting control, etc.

Consumer Electronic Production Industries

SMT manufacturing plays a vital role in the large-scale production of electronic consumer product components.

These products include video games, television sets, washing machines, computers, remote systems, etc.

What Are Some Control Methods You Will Use To Stop Defects In SMT Manufacturing?

The main concern as SMT manufacturing is increasing is to ensure electronic products remain reliable and perform suitably.

SMT manufacturing also ensures the longevity of electronic product development.

Process control systems need to be there to ensure practical manufacturing requirements that ensure standardized, reasonable, and regulation processes.

Rigorous control processes need to happen within the entire manufacturing process as it will expose quality concerns in a timely fashion.

This helps in minimizing loss and the number of rejected products due to disqualification.

For this reason, it is vital to conduct process control methods during SMT manufacturing.

SMT manufacturing entails solder paste printing, placement of components, and reflow soldering steps.

To obtain high reliability, you need to implement process control measures at all stages.

Solder Paste Printing Process Control Method

Ensure you inspect all PCB batches before solder paste printing.

Some inspection items include the occurrence of deformations, oxidation on pads, smoothness of printing, and if shorts, scratches, and exposure happen on the PCB surface.

Inspect The Whole SMT Manufacturing Process From Start To End.

Wear gloves when handling the boards, and make sure visual inspection happens at correct distances and angles.

Ensure you rigorously monitor the solder paste, avoid using overdue solder paste, and store good solder paste in cold closets or refrigerators.

Once you open the solder paste, use it within 7 days and ensure you operate in suitable environmental conditions.

Furthermore, ensure suitable solder paste printing happens under the following requirements:

  1. Complete printing
  2. Avoid bridging
  3. No deviations when printing
  4. Smooth and even printing thickness

Chip Mounting Process Control Method

A chip mounter can accurately and quickly place parts on pads via absorption, positioning, moving, and placing stages.

Some of the mounting requirements include:

  1. Accurately and sufficiently use all surface-mount devices
  2. Avoid errors from reoccurring by combining feeders and surface-mounted devices
  3. Accurately edit the program and ensure they meet programming needs
  4. Debug chip mounter before chip mounting and deal with breakdowns in a timely fashion during SMT manufacturing

Here are some measures you can undertake to deal with chip mounting defects:

  1. Analyze chip mounter operating sequence and identify logics within the transmission components
  2. Clarify operational processes before defects
  3. Study defect redundancy to determine if it happens at specific times
  4. Clarify defects to understand if they happen on surface-mount devices or component feeders
  5. Determine if defects occur at fixed positions after clarifying them

Reflow Soldering Process Control Method

The reflow soldering should meet these requirements:

  1. Avoid vibrations on transportation belts during the reflow soldering process
  2. Conform reflow direction to the PCB design
  3. Set appropriate reflow soldering temperature levels and conduct tests at specific intervals

How Does An SMT Machine Operate?

The machine operates automatically when placing electronic components on printed circuit boards.

Compared to thru-hole technology, SMT parts are directly placed on the surface of the printed circuit board without soldering.

Besides, the SMT machine operates quickly and accurately.

SMT manufacturing contains a head and arm that will reach all tubes, reels, parts, etc.

The machine will pick up the surface-mount component and precisely place them on the printed circuit board.

Furthermore, the machine employs vacuum heads that pick the electronic parts before accurately placing them on the printed circuit board.

They are commonly known as Pick and Place machines.

Also, they will pick individual components from reel magazines and place them on bare printed circuit boards.

Besides, you need to accurately program the machine to ensure it performs suitably and guarantees a quality finish.

What Are The Advantages Of SMT Manufacturing?

The advantages include the following:

Accurate Component Placement

The surface tension of solder will force electronic parts to alight with the solder parts, thereby minimizing errors during placement.

Cost

Since the surface-mount devices are smaller, you will spend less than when using larger parts in THT manufacturing.

Flexibility In Design

To enhance the printed circuit board functionality, you can combine SMT and THT manufacturing.

EMC Compatibility

Small parts with low lead induction enable you to attain small radiation loop areas thereby achieving suitable electromagnetic compatibility.

Manufacturing Automation

Since the design and electronic components are standardized, you can automate the manufacturing process.

Quick Production Set-up

Since you will not drill the printed circuit board during mounting, you will save more time during the assembly process.

High Circuit Speeds

SMT manufacturing enables you to achieve high circuit speeds which most manufacturers attest to as beneficial.

Low Induction Or Resistance

The high-frequency performance will minimize unsuitable RF signal consequences.

Production Speeds

SMT manufacturing increases production speeds since you will eliminate or reduce drilling thereby having a short set-up time.

Multitasking

High-end electronic parts are highly versatile.

Quality And Quantity

It is possible to place electronic components on both sides of the printed circuit board, thereby offering several connections for every part.

This means you require a few PCBs in devices.

Selective Soldering

It is possible to customize the soldering as you can use solder glue for the attachment of components.

Stability

SMT manufacturing offers more stability and ensures better performance in vibration or shaking environments.

What Are The Disadvantages Of SMT Manufacturing?

Some of the disadvantages include the following:

  • Unsuitable for sole component attachment methods subject to regular mechanical stress
  • Damage of solder connection by potting components pasting via thermal cycling
  • Unable to install many SMT component packages in sockets
  • Smaller components require cryptic and smaller markings since they have less surface area than thru-hole components
  • Easy to break
  • Produce small power
  • The high initial cost of equipment
  • Easy to drop or damage components when installing
  • It is difficult to conduct visual inspection making it hard to test
  • Small size and several solder joint types make the inspection process difficult
  • High learning costs due to its technical complexity
  • It is not possible to mount parts that generate more heat or high electrical loads as the solder will melt under these temperatures

How Does SMT Manufacturing And SMD Manufacturing Compare?

Surface-mount technology [SMT] manufacturing is the technique of placing electronic components such as surface-mount devices on a printed circuit board.

SMT Manufacturing

SMT Manufacturing

SMT manufacturing uses precise solder paste amounts on the printed circuit board.

Thereafter, a pick and place machine will mount the surface-mount device on the printed circuit board.

Surface-mount device [SMD] is an electronic component that you will place on the surface of a printed circuit board using surface-mount technology.

SMD Manufacturing

SMD Manufacturing

How Does SMT Manufacturing And THT Manufacturing Compare?

SMT manufacturing is the process of placing different kinds of surface-mount devices on the surface of a printed circuit board.

SMT Manufacturing

SMT Manufacturing

It will use a solder paste that will form a bond between the pads and the components.

Through-hole technology [THT] manufacturing is the process of inserting component leads within pre-drilled holes in a printed circuit board.

Thereafter, you will solder the leads on the opposite side of the printed circuit board using devices like soldering irons or wave soldering processes.

The devices you will use in SMT manufacturing are smaller than those in THT manufacturing.

Also, you can place components on both sides of a printed circuit board in SMT manufacturing which is not possible with THT manufacturing.

THT Manufacturing

THT Manufacturing

What Is SMT Manufacturing Soldering Process?

SMT manufacturing soldering process entails using a semi-solid pate containing fine solder and flux.

This forms a solder paste which you will dispense on the solder pads on printed circuit boards.

Besides, you can dispense the solder paste using stencils through a screen printing process with surface-mount technology screen printers.

After placing the solder paste on the PCB, you will relay the board to a pick and place device.

The pick and place device will pick up the surface-mount devices and accurately place them on the printed circuit board.

Once the machine finishes the process of placing the components on the board, the PCB moves into the reflow soldering oven.

The reflow soldering oven contains different chambers where the board will pass through.

In the first chamber, the pre-heat zone, the oven will gradually and uniformly raise the temperature of the components and the board.

This process happens in small increments to prevent cracks from forming on the PCB because of thermal shock.

Afterward, the PCB moves into the high-temperature zone.

Here, the high-temperature levels will melt the solder paste thereby soldering the component leads to the PCB pads.

The molten solder’s surface tension will assist in keeping the components in the correct place.

Besides, surface tension will align parts on their respective pads automatically.

Thereafter, the PCB undergoes a cooling process to prevent damage to the components and board.

What Soldering Techniques Can You Use In SMT Manufacturing?

The different soldering techniques you can use entail the following:

  • Vapor phase reflow soldering
  • Infrared reflow soldering
  • Hot gas convection soldering

What Are Some Types Of SMT Manufacturing?

There are three types of SMT manufacturing namely Type I, Type II, and Type III.

Also, they may be either active or passive surface-mount components.

Besides, they incorporate both surface-mounted devices [SMDs] and through-hole components [THT].

  • Type I surface-mount technology

In this assembly type, you will only find surface-mount components.

Also, the assembly can come as either double-sided or single-sided printed circuit board.

  • Type II surface-mount technology

This assembly version encompasses both Types I and III assembly methods.

Besides, it lacks active surface-mount devices on the underside but may have discrete amounts of SMDs on the underside.

  • Type III surface-mount technology

This assembly method has discreet amounts of surface-mount components that you will glue to the underside.

What Are Some Electronic Components You Will Use In SMT Manufacturing?

The two types of electronic components include active and passive surface-mount parts.

Passive Electronic Components

These components offer no extra power gain to the device or printed circuit board.

They employ a simpler surface-mount technology and come in cylindrical or rectangular shapes.

Besides, passive surface-mount capacitors and resistors come in varying sizes for different applications.

There are two main types of surface-mount discrete resistors:

  1. Thin-film surface-mount resistors
  2. Thick surface-mount resistors

The other types include:

  1. Resistor networks
  2. Ceramic capacitors
  3. Tantalum capacitors
  4. Tubular components

Active Electronic Components

The two main categories of active surface-mount components include:

1. Ceramic leaded chip carriers

They exist in post-leaded and pre-leaded variations.

Pre-leaded versions have copper alloy attachments while post-leaded versions have their leads attaching to castellations of leadless ceramic chip carriers.

ceramic lead chip carrier

Ceramic Lead Chip Carrier

2. Leadless ceramic chip carriers

These chip carriers lack leads but contain gold-plated terminations enabling them to function at high frequencies.

leadless ceramic chip carrier

Leadless Ceramic Chip Carrier

The other variations include:

  1. Small outline transistors [SOT]
  2. Plastic surface-mount device packages
  3. Small outline integrated circuit [SOIC]
  4. Plastic leaded chip carriers [PLCC]
  5. Ball grid array [BGA]
  6. Small outline J packages [SOJ]
  7. Fine pitch packages

What Are Some Sizes For Solder Paste Printing In SMT Manufacturing?

The most popular powder size for solder paste in SMT manufacturing are types 3 [T3], 4 [T4], and 5 [T5].

Besides, larger particle sizes have a lower numerical value within solder powder.

What Should You Consider When Sizing Solder Mesh For SMT Manufacturing?

It is difficult to fill apertures with suitable solder paste amounts as packages, parts, and solder connections are getting smaller with time.

Also, there is an increased demand for type 4 and 5 solder powders since type 3 solder paste is large for precise and reproducible fine pitch parts.

For instance, type 3 solder paste falls through a 325 screen mesh but not via 500 screens mesh, thus the terminology -325+500.

What Are The Stages In Reflow Soldering In SMT Manufacturing?

The stages within a reflow soldering machine in SMT manufacturing entail the following:

Soldering Oven

After you place the electronic components on the printed circuit boards, you will place them into a reflow soldering oven.

Pre-heat Zone

This is the first zone the PCB will pass on in the reflow soldering oven.

The pre-heat zone ensures that the temperature of the PCB and electronic components rise simultaneously.

The rate of temperature variation in this zone is 1℃ to 2℃ per second.

This rise continues gradually until the temperature reaches between 140℃ and 160℃.

Soaking Phase

Once you preheat the PCB, it remains within the soaking phase within the reflow soldering oven.

This happens at a temperature level between 140℃ and 160℃ for about 60 and 90 seconds.

Reflow Zone

The printed circuit board then moves to a zone where the temperature increases steadily at a rate of 1℃ and 2℃ per second.

Besides, the temperature will also rise to between 210℃ and 230℃.

This ensures the tin within the solder paste melts, thereby bonding all components leads to the PCB pads.

Furthermore, the molten solder helps maintain the surface tension thereby keeping the electronic components in place.

Cooling Zone

This phase will freeze the solder after exiting the heating zone.

The purpose of the cooling zone is to ensure no joint defects occur.

Can You Perform Reworking Processes In SMT Manufacturing?

Yes, you can repair defective surface-mount devices using solder irons or non-contact reworking units.

Reworking systems are a suitable option as SMD operation with soldering iron needs expertise and are rarely feasible.

Reworking will correct some machine-generated or human flaws on the board.

Besides, it entails the following steps:

  • Melting the solder paste and removing the surface-mount component
  • Removing residual solder
  • Printing solder paste on the printed circuit board, either through dispensing or directly
  • Placement of new parts then reflowing

There are two non-contact soldering or desoldering processes include hot gas soldering and infrared soldering.

Infrared Soldering

Here, the energy that heats solder joints come from short or long-wave infrared EM radiation.

The benefits of this type include:

  1. Does not require compressed air
  2. Easy to set-up
  3. Quick infrared source reaction
  4. Low cost as you require no special nozzle for different component size and shape

Some disadvantages include:

  1. Surrounding areas receive less heat than central areas
  2. Reflow atmosphere is not possible
  3. Electronic component’s albedo dictates the surface temperature as dark surfaces are heated faster than light surfaces
  4. It is difficult to control temperatures and you may experience peaks
  5. The shape of the surface dictates the temperature
  6. To prevent surrounding components from damage, you need to shield them, thus time-consuming

Hot Gas Soldering

In this method, hot gas transmits the energy you will use when heating the solder joints.

The benefits of hot gas soldering include:

  1. It simulates the atmosphere of reflow ovens
  2. Other systems enable you to switch between nitrogen and hot air
  3. It allows you to evenly heat the targeted area
  4. Efficient heating as you can transmit large heat capacities
  5. The component temperature never surpasses the set gas temperature
  6. Fast processing and reliability with standard and specific part nozzles
  7. The solder joints experience small grains as it cools quickly after the reflow process

The limitation is that heat generator thermal capability equals slow reactions, thus you can distort thermal profiles.

What Equipment Will You Use In SMT Manufacturing Line?

These include:

  • Pick and place machine

This machine picks the components and accurately places them on pads on PCBs.

  • Solder paste mixer

This machine will evenly mix solder paste and powder.

It also assists in achieving suitable reflow and printing effects, standardized functionalities, and saves labor.

  • Oven

This machine bakes PCBs and removes moisture and sits at the end of the SMT manufacturing line.

  • SMT loader

This machine places PCBs in solder printing machine racks automatically.

  • Solder paste printing device

This machine prints solder paste on blank PCBs and is found before the pick and place machine in the SMT manufacturing line.

  • Solder paste inspection machine

This machine inspects the area, thickness, and distribution volume of the solder paste you print on printed circuit boards.

  • Reflow machine

This machine is responsible for melting solder between the pads and electronic parts.

It also cools them after leaving the reflow oven to form suitable electric connections.

  • Automated optical inspection

This device detects flaws of parts before and after the reflow soldering process.

  • Docking unit

This device connects various devices in the SMT manufacturing line.

  • SMT unloader

They receive and store circuit boards following reflow soldering.

What Are Some Trends In SMT Manufacturing?

Several devices are moving towards small, lightweight, and highly-reliable printed circuit boards.

SMT manufacturing is aiding in this process since you can use small parts.

Some advancements entail higher speeds, LED technology development, and soldering paste.

The main development in SMT manufacturing entails using simple to use, high-performance, and flexible printed circuit boards.

Trends that are shaping SMT manufacturing entail:

  • The rise of smart consumer products that need dense PCBs
  • Cyber hacking impacts PCB assembly industries
  • Excess use of unconventional substrates entailing flexible PCBs

What Are Some Causes Of Defects In SMT Manufacturing?

These include:

  • Poor placement of components
  • Bad soldering processes
  • Poor solder paste printing techniques

What Is The Cost Of SMT Manufacturing?

The cost depends on the following:

  • Accuracy of equipment
  • Quality and stability
  • Production capacity
  • Specification parameters

What Are The Types Of Line Layouts In SMT Manufacturing?

These include the following:

  • Single line with one rail pick and place layout machine
  • Two-to-one line with single rail pick and place layout machine
  • Two-to-one line with double rail pick and place layout machine
  • Two-to-one double rail pick and place layout A high-speed machine
  • Two-to-one double rail pick and place layout B high-speed machine
  • Three-to-one line with one rail pick and place layout machine
  • Multiple layout line combination

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