PCB Assembly Expert
PCB Assembly is the Process of Populating or Stuffing Printed Circuit Boards with Electronic Surface Mount and/or Through-hole Components to form a Functional Printed Circuit Board Assembly (PCBA). The PCB Main Function is to Mechanically Support and Electrically Connect the Electronic Components.
Prototype PCB assembly process is very important before volume production,we provide 24h fast delivery time for you.
We could provide turnkey PCB assembly and you don’t worry about the sourcing components and also save cost for you.
Ball Grid Array(BGA) is an important type of surface-mount,we can produce high-quality BGA Assembly Board with excellent proceeds rates.
We provide surface-mount technology (SMT) assembly from prototype PCB assembly,low volume to high volume PCB assembly.
Component sourcing is very important stage during PCB assembly,especially material incoming assurance.
PCBMay: Your Professional PCB Assembly Provider in China.
As a leading and professional printed circuit board fabrication supplier in China, PCBMay also provides a one-stop PCB assembly service for you.
The most important step after PCB manufacturing is PCB assembly. If there is no PCB assembly, no work can be done with that PCB. The PCB assembly is the lifeblood of the PCB.
When a PCB is designed, it is designed with some functionality in mind. That is, it will determine what the PCB will do and what components it will use, and what kind of connection it will have between each component.
Now that the PCB design is complete, it is sent for manufacturing. When the PCB is manufactured, the necessary components are placed in it, i.e. it is made usable.
The process of installing this component is called PCB assembly. Earlier PCB assembly was done manually. But now with the advent of advanced technology, the PCB assembly process has become automatic.
That means now the whole process can be done automatically. As a result, the cost of assembling the PCB is much lower now and as a result, the price of the final product is lower.
|Process Capability Parameter
|24 hours expedited service can be offered. 3- 4 days normally for PCBA prototype orders. We will give you an accurate lead time when we quote for you.
|Rigid PCB, Flexible PCB, metal core PCB
|±0.035mm(±0.025mm) Cpk≥1.0 (3σ)
|Lead/Lead-free HASL, Immersion gold, OPS, etc.
|Surface mount (SMT), Through-hole (DIP), Mixed Technology (SMT & Thru-hole)
|Turnkey (All components sourced by PCBMay), Partial turnkey, Kitted/Consigned
|BGA Dia. 0.14mm, BGA 0.2mm pitch
|SMT Parts Presentation
|Cut Tape, Partial reel, Reel, Tube, Tray, Laser-cut Stainless Steel
|We supply custom cables, cable assemblies, wiring looms/harnesses, and power leads for various industries including automotive, security, mining, medical, and entertainment.
|Stencil with or without frame (offered free by PCBMay)
|Visual inspection; AOI checking; BGA placement – X-RAY checking
|3 Million~4 Million Soldering Pad/day
|100 Thousand Pins/day
Your Trust PCB Assembly Supplier in China
Are you looking for a reliable PCB assembly supplier in China? PCBMay is here and always support you when you need us. We’re in PCB industry for more than 10 years and serve over 1000 clients all around the world. If you need know more about the manufacturing process, please check here.
PCBMay is one reputable PCB manufacturer and assembly provider. We promise to go with considerable efforts and make sure that you will get high-quality PCB assembly.
You just send the Gerber file and BOM list to us, our professional engineering team will provide you the design suggestion for your reference.
There’re more than 500 workers in our plant and 6 fully automatic SMT production lines, 3 wave soldering production lines, 5 assembly lines, and auxiliary testing and aging facilities.
Don’t hesitate to contact us, we’re happy to help you.
PCB Assembly: The Ultimate FAQ Guide
Do you want to know about PCB assembly? There’s one FAQ guide, you will find more information here.
- What is PCB Assembly?
- Printed Circuit Board Basics
- PCB Pre-assembling Processes
- Printed Circuit Board Assembly Types
- Surface Mount Technology Printed Circuit Board Assembly Process
- Through-Hole Technology Printed Circuit Board Assembly Process
- PCB Assembly Applications:
- Basic steps in PCB design:
- Preparation for PCB assembly:
- Types of PCB assembly process:
- PCB assembly process flow:
- Surface Mount Technology Assembly Process:
- PCB Assembly Capability:
- How to Find the Best PCB Assembly, Service Provider:
What is PCB Assembly?
PCB assembly or PCBA is the process of installing or mounting different components on the Printed circuit board.
There are two types of PCB assembling processes. The first one is a manual process and the second one is an automatic process.
In a manual process, one can assemble his printed circuit board manually but for that, we must need some PCB soldering skill.
We have to pick up components and placed them in the right position and then soldering it properly. In the printed circuit board there are holes for each component.
In the automatic process, you have to contact a manufacturer or PCB assembly service provider and they will do it automatically with their advanced machine.
The automatic PCB assembly process is less time-consuming and can perform the assembly process more perfectly and accurately.
Printed circuit boards (PCBs) are an essential element of every electronic appliance; their reliability and durability are of supreme importance. Accordingly, the PCB material, circuit design, components, everything is carefully selected and used but printed circuit board assembling (PCBA) is also a vital factor that directly impacts the functioning and life of a PCB.
A poor-quality assembling can cause malfunctioning even if a PCB is developed with top-quality components and material.
Evidently, PCBs must be assembled as per the standard procedures.
After a PCB is manufactured, the components are assembled on it to form a circuit. As long as the components are not assembled on a PCB, the bare board does not provide the required functionality.
There are two major techniques of PCB assembling: through-hole assembling and surface mount technology.
Both techniques involve component placement and soldering on board.
PCB Assembly Process
Printed Circuit Board Basics
To understand how a PCB is assembled and the steps involved in PCB assembling, you must overview the layers that constitute a PCB.
A circuit board is made up of primarily two types of layers: a substrate and a conductive layer. But some other layers are also imprinted on a PCB for enhancing its protection and reliability.
The copper layer is also called the conductive layer; it is carved to form circuit tracks that eventually connect electronic components assembled on the board.
It is an insulator and the foundation of the circuit board. It forms insulation between traces to avoid the unwanted flow of signals. The substrate used In rigid PCBs forms insulation, but it also forms a robust base to carry heavy circuits.
Similarly, the substrate in flexible PCBs gives them flexibility.
It is produced over the conductive copper layer for protection.
It protects the copper layer against corrosion, and accidental short circuits (if any other conductive device accidentally comes in contact).
The solder mask layer is usually green in color.
After the circuit tracks have been created, the symbols, values, and essential details are labeled on the PCB with a white silkscreen layer.
It provides the details about each placement, where and which component or what value has to be mounted.
Now that you have learned about PCB basics, you should learn about pre-assembling procedures that are essential for reliable PCB assembling.
PCB Pre-assembling Processes
Commercially PCBs are not assembled right after assembling; they must go through the pre-assembly process.
After a PCB is manufactured, the assembly company or department runs a design for manufacturability (DFM) check.
It is so that the design of the PCB can be analyzed and cross-checked with the design files to ensure it is correct.
DFM check is run primarily to spot missing details, unwanted connections, and other technical flaws that can affect the circuit’s reliability and durability.
The DFM test is essential because some PCB designs require special care during assembling.
For example, the high-frequency circuits are prone to malfunctioning even if the track’s width varies a bit or the track’s shape is incorrect, or even if the space between tracks is too narrow; it affects the impedance of circuits and alters the functionality. Similarly, some electronic components are susceptible to electrostatic discharge (ESD) which means that they cannot be assembled using ordinary assembling equipment.
The purpose of the DFM check is to ensure that the PCB is ready for assembly and save time and cost.
Apparently, if a PCB is flawed and still assembled, the PCB won’t function as wanted, and in such cases, the design has to be improved, and the PCB has to be developed again; leading to cost and turnaround time escalation.
But with a simple DFM check, the possibility of developing a faulty PCB is eliminated.
To further learn about the possible problems and to validate the design, the assembler study’s the design files, data sheets App notes, and design requirements (if there are any).
Printed Circuit Board Assembly Types
Simple PCBs are assembled manually, but on a commercial scale, especially complex PCBs, the assembling process is carried out on an automated printed circuit board assembling machine.
There are two main types of PCBA; the primary difference between both types comes from the different types of electronic components used in the circuit.
The two main types of electronic components are surface-mount devices and through-hole devices.
The major difference between these types is their physical architecture; through-hole devices are larger and have longer pins. The detailed differences are as follows.
Surface Mount Devices
Surface mount devices are smaller than their respective through-hole packages, which reduces board size and requires extreme care
. A 01005 size SMD is barely 0.4×0.2mm in size whereas a human hair is 0.1mm thick.
Tiny Surface-mount Devices
SMDs are soldered directly on the top of the printed circuit board but given their small size; they are soldered using special equipment; regular solders can burn SMDs.
Through Hole Devices
Through Hole Devices are comparatively larger and cheaper, they are suitable for circuits that do not need to be compact.
Moreover, through-hole components are commonly available, whereas the SMD package of many components does not exist.
The through-hole components are places on one side of the board, and their pins are soldered on the other side. As the pins have to be passed to the other side, holes are drilled in the board.
Now since, both SMD and THD have certain differences in their physical architecture, their assembling processes also differ.
Surface Mount Technology Printed Circuit Board Assembly Process
Step 1: Apply Solder Paste to the Board
Surface mount devices are soldered on the top of the board, and their pins are small, which is why their soldering demands extensive care.
Unlike through hole components’ assembling, surface mount devices are placed on the board after applying solder.
The solder applied onboard is in the form of paste; that is why it is called solder paste.
To ensure the solder paste is applied only to the specific pads where component pins have to be soldered, a solder stencil is placed on the board before the solder paste is applied.
As the solder stencil is designed according to the circuit layout; there are cut-through holes in places that have to be soldered.
These holes enable the solder paste to apply on board; specifically in regions that have to be soldered.
Like solder wire, the solder paste is a composition of metals, and it is in the form of tiny balls. Solder paste contains 96.5% tin, 3% silver, a very small fraction of copper and flux.
The flux enables the solder paste to ease the process of solder paste melting and bonding to the board.
When applying solder paste, it is important to the precise quantity and only in regions that have to be soldered; improper quantities can cause solder spreading and the formation of unwanted connections.
As the solder stencil and the board are not fixed, even a slight push can displace the solder stencil and cause solder paste spreading on unwanted regions.
To ensure the stencil does not move, a mechanical fixture is used for firmly holding the board and stencil together.
Then an automated machine spreads the solder paste through the stencil in the right quantity.
Step 2: Component Placement
Once the solder paste has been applied to the board, the board is ready for component soldering. As already explained, surface mount devices are sensitive, and even an ESD from human hands can damage them, and SMDs can be tinnier than a pencil tip. This is why on a commercial scale the pick and place process of SMDs is also automated; a robotic machine picks the components and places them in their right position on the board. The machine is preprogrammed; the program instructs the machine about the positions where the components have to be placed.
It uses a vacuum grip to pick and place components.
Conventionally, this step was performed manually with tweezers’ help; the assembler picks the components with a tweezer and places them on the board.
But since the SMDs are too small and precise placement is difficult with hands, the manual placement was not entirely reliable.
Whereas with automated machines, the pick and place process is more effective.
Step 3: Soldering
The solder paste and components have been placed on the board by this step, but the solder paste is still unsoldered.
To permanently bond the components to the board, the solder paste needs to be solidified.
The process of solidifying solder paste and soldering the components to the board is called reflow soldering.
Reflow Soldering Process
To solder the components, the board is passed into a reflow through a conveyor belt.
The oven is equipped with heaters and coolers. The PCB first passes through the heating section where the temperature ranges around 250 degrees Celsius which is high enough to melt the solder paste and cover the solder pads and component pins.
As the PCB moves through the oven, it is passed through a series of coolers which solidify the molten solder paste and form a joint.
Consequently, the components are permanently soldered to the PCB.
Reflow soldering for single-layer PCBs is simpler and easier as compared to double-layer PCBs.
In the case of double-layer PCBs, each side has to be soldered separately. The soldering begins with the side that carries fewer components.
Step 4: Assembly Inspection
Technically the assembly process completes by the end of reflow soldering but to ensure the PCB functions correctly, it is inspected for potential flaws.
This is essential because in some cases, the solder does not properly melt and connect the pin with the pad, or the unintentional misplacement of an item causes improper solder.
Moreover, in some cases, unwanted connections are established that cause malfunctioning.
This is why the assembling process does not end with reflow soldering, and the PCB is thoroughly checked for improper connections.
The inspection is performed using any of the following methods (depending on the design).
Even though the machines’ inspection is reliable, manual inspection still remains the most commonly practiced method.
This is because human vision is more reliable in comparison to machines.
Manual inspections are suitable for small circuits, but it is impractical for large and complex circuits.
Automatic Optical Inspection
Unlike manual inspection, the automatic optical inspection (AOI) is performed by a machine.
The machine directs light on each solder from multiple directions and analyzes the solder through cameras.
AOI is a suitable and effective method if the circuit design is complex or a large number of PCBs need to be inspected.
This method is used only for inspecting solders that cannot be visualized by the human eye or camera.
The –ray inspection can detect hidden solder flaws as the x-ray can pass through layers.
Step 5: Assembly Functionality Testing
After a PCB successfully passes the inspection phase, it goes through the functionality testing stage.
This is to ensure that the PCB performs the required functions. Certain functionality tests are performed on the PCB to test different aspects of functioning.
The functionality test is performed by powering the PCB and matching the outcomes with the same circuit’s simulation.
If the PCB’s output matches the simulation, it passes the test; otherwise, it fails.
PCB Testing Process
This stage helps analyze whether the PCB has been assembled correctly or not.
In case a PCB fails a functionality test, the problems are highlighted and corrected in the later boards; leading to cost reduction and time-saving. If a PCB assembly fails the inspection or testing phase, the assembly team reworks on it or scrap it.
Through-Hole Technology Printed Circuit Board Assembly Process
The assembly of through-hole components is slightly different from the assembly of surface mount components but some steps are common.
As already explained, the through-hole components are placed on one side of the board and soldered on the other side; they are soldered using solder wire instead of solder paste.
This is because the solder paste (in the molten form) can run through the holes to the other side of the board. Follows are the assembly steps of through-hole devices.
Step 1: Drilling
As the pins of the components have to be passed to the other side, holes are drilled inside the PCB. Traditionally, hand drills are used for drilling purposes, but commercially automated drilling machines perform the task.
Moreover, the automated machines can effectively drill dozens of PCBs within an hour, whereas the manual drilling process is slow and less reliable.
Step 2: Component Placement
Like SMD assembly, the components are placed on the board with their pins passing through the holes.
The component placement is can be either manual or automatic.
Step 3: Soldering
The soldering of through-hole components can be either manual or automatic. Their difference is as follows.
The manual soldering of through-hole components is simple and easy for small-scale PCBs; an assembler can single-handedly solder a complete board, but the process can be hectic if the design contains several components.
Usually, a mechanical fixture is used for holding the PCB from the edges as the soldering process involves the use of both hands.
Automatic soldering, also known as wave soldering is somewhat like SMD soldering in an oven; automatic soldering involves passing the PCB through an oven for soldering. But in this case, after putting the components on board, the board is passed into the oven through a conveyor belt and the pins are washed with molten solder and then cooled. But automatic soldering has some limitations; it is suitable only for single-sided PCBs.
Step 4: Through Hole PCB Inspection and Functionality Testing
Alike SMD assembly, the through-hole PCB is also inspected to find potential assembly flaws and later tested to check its functionality.
Evidently, PCBA is an extensively technical process and requires extraordinary care.
PCB Assembly Applications:
We know that PCB is a very important thing in almost all electronic devices now.
So the applications of PCB assembly are much wider. We will briefly discuss some applications of PCB assembly here.
LED Matrix and LED Display PCB Assembly:
Now almost all of us use LEDs. Advanced PCB assembly technology is used to create all these LED matrices and displays.
Making an LED display is one of the hardest tasks because here you have to maintain the design sent by the customer and also have to create the perfect and reliable product.
First, we have to manufacture the circuit board designed by the PCB designer.
Then we have to arrange an LED bulb. There is a number of led modules in the market.
You have to choose as per the customer’s requirement.
The next step is assembling an LED board. First set your board at the assembling unit.
Put your components (LEDs) under the pick and place machine and then it will place all the LED components and solder them accordingly.
LED Display Assembly
Simplifying the Complex Task:
Before the automatic assembly process, there are so many problems.
The manual PCB assembly process was hard. It was time-consuming and costly.
So the cost of the final product was always costly. In the manual assembly process, there is a high chance of error in soldering which may affect the quality of the product.
But in the automatic assembly process, it is always safe because we can check all the comment placement measurements through software.
Side by side it is less time-consuming and can produce a large number of assembled PCBs at the same time. It can easily maintain the quality of the product.
Industrial PCB Assembly Applications:
In many industrial applications, we use PCB assembly. These types of PCBs are called industrial PCB assemblies.
Industrial automation systems are useful for automating the whole process of manufacturing and controlling a manufacturing unit from a remote device.
This type of automation system is made up of complex Industrial PCB assembly.
Because of its high configuration operating power industrial PCBs are used to operate such complex systems.
Industrial PCB assemblies are more complex than consumer PCB assemblies.
Working with normal wiring is almost impossible in industrial applications.
Here the safest way to operate this advanced machinery is using Industrial PCB assembly. Assembling this type of PCB is not an easy process. There are so many steps involved.
So PCB manufacturers with the most advance and latest equipment can manufacture and assemble this type of PCBs.
Industrial PCB assemblies need to be done carefully as they have to work in extremely high temperatures and harsh condition.
Industrial PCB Assembly
Automotive PCB Assembly:
In the automotive industry, the use of PCB is increasing day by day. PCBs are not only used in windshield wipers or headlights but now they are used in many places like automatic door locks, sunroof operation, and many other places.
Most of the PCBs used in cars are used for advanced operations. All these PCBs require advanced machines for assembly.
This is because if the PCB assembly is not working properly, the components in the PCB can be damaged in car jerking and other difficult situations.
In aerospace engineering, PCBs are used widely to develop different applications.
The PCBs that are used in aerospace applications have to work in a much more difficult environment than other PCBs.
This type of PCB is used in planes, satellites, space shuttles, etc.
Assembling PCBs for Aerospace equipment is much more challenging than any other PCB assembling.
A little problem in assembling can create a huge problem in any aerospace system.
So in the case of this type of PCB assembly, some unique machinery has to be used and many precautions have to be taken.
In maritime applications, PCBs are used to build different control systems, navigation systems, and communication systems.
Many precautions have to be taken to assemble the PCB used in maritime applications.
This type of PCB is usually waterproof so that it can work in water and excess heat.
Most of the defense equipment is highly dependent on PCB.
PCBs used for military applications should be reliable and durable.
Starting from a radar system to a long-range communication system, a wide-range control system PCB is used widely.
PCB designing and assembling defense equipment is not an easy task.
Specialized designers and highly advanced manufacturers are responsible for assembling this type of PCB.
Top defense equipment manufacturer uses their specialized PCB assembly unit to accurately assemble each and every component of PCB.
Medical PCB Assembly
All of you are familiar with ECG, CMRI, X-rays, etc. All of these machines are largely depend on PCB within them.
Now there is PCB in the pulse oxy meter which is now used by almost everyone.
The PCB of the devices used for medical purposes has to be very accurate and perfect. For this, you need to contact an experienced service provider to assemble all these PCBs.
Robotics PCB Assembly
The popularity of robotics is growing day by day. Almost every engineering field trying to utilize the power of robotics to automate the process of working.
So the demand for PCB for robotics development is increasing day by day.
Assembly services for robotic PCB are now available all over the world.
IoT is now one of the most demanding technology.
Some observers predict that Internet traffic will grow faster for IoT objects than any other kind of device over the next five years, with more than 25 billion IoT objects in use by 2020, 76, and perhaps 50 billion devices altogether. IPv4 appears unlikely to meet that growing demand, even with the use of workarounds such as methods for sharing IP addresses.
Version 6 (IPv6) allows for a huge increase in the number of IP addresses. With IPv4, the maximum number of unique addresses, 4.2 billion, is not enough to provide even one address for each of the 7.3 billion people on Earth.
PCBs are helping to improve IoT applications. It is now easy to build customized IoT products due to the availability of PCB manufacturers and assembly services in the market.
Basic steps in PCB design:
PCB designing is a complex process. First, you have to choose the right software then you have to learn how to design with that software. There are few basics steps to design PCB. We will discuss that.
1. Creating the Schematic:
First, you have to start with the schematic. Schematic is like planning your circuit. In this step, you have to plan which components you want to use in your design.
You can easily select components from the library of the software you used.
After choosing the proper component you have to connect them according to your circuit diagram.
If you want to design a complex circuit diagram then you can use a hierarchical schematic.
It is always easy to convert a schematic to a board layout.
2. PCB Layout:
The second step is to create a PCB layout. For this at first, create a blank PCB document.
You can set the shape, dimensions, and layer stack-up information in this step.
All these pieces of information are editable or changeable. You can set them as per your requirement.
3. Schematic capturing Tool:
In this step, you have to use a schematic capturing tool to capture the schematic for the circuit.
You can do this in many ways. In this stage, the schematic may be entered into a schematic capturing tool that belongs to the software you use during design. Sometimes it may be an external package.
Always try to complete the design of the circuit in this step and properly convert the file into “netlist”. “Netlist” is nothing but the interconnectivity information of the circuit.
4. Component placement and planning:
In this step, we have to create a plan for the placement locations of all the components that means where the components will be located and how many spaces will left and whether it is sufficient for all the components.
As the planning is done now we have to perform the right placement of the components and prepare for the routing.
In this stage, the PCB software you used for the PCB design routes the physical connections.
All the connections done by the software happens as per the netlist. To do that number of layers can be used which are available for connections.
After completing. Now create via and holes as required.
Most of the time one layer is used as the ground plane and another as a power plane to reduce the noise level and resistance of the circuit.
The high component density can increase the difficulty level of the routing.
It is always recommended that if it is possible to remove unnecessary components from your design then do it so that routing can be done easily and it also saves your time.
6. PCB files and Gerber Files:
After completing the design we have to manufacture it from a PCB manufacturer.
In this case, the PCB manufacturer needs some information along with the design file.
All this information exported as a Gerber file. A Gerber file is simply opened ASCII vector format files for PCB.
The design information about each PCB layer is provided by the designer in this file.
Information related to the copper layer, drill data, solder mask, copper traces, pads, vias, etc is provided here.
The Gerber file is the most important file for PCB fabrication. Earlier a company used to make these Gerber files.
The name of this company was Gerber Scientific. This company was founded by Joseph Gerber.
For the special advantage of this type of file, it has become a very common file in the PCB manufacturing industry.
This type of file is mainly zipped into a single file and then it is ready to send to the PCB manufacturer.
The data package within the Gerber file may consist of different layers.
For Each element such as the copper layer, circuit diagram, power, etc similar Gerber files are required to create the desired pattern.
The process of generating a Gerber file may vary with the software you used for PCB designing.
Contact the manufacturer and send your design files to manufacture your PCB according to the design file.
Preparation for PCB assembly:
Before entering into the actual PCB assembly process there are few steps to follow carefully.
At first, a PCB assembly service provider should perform DFM checking or design for manufacturability checking. In this checking process, we can review all the design specifications of a PCB.
If there is an error in the design we can detect it in this step. Such as if the PCB designer leaves a very little gap between the two components then at the time of assembly there is a high chance of a short circuit.
DFM check is mandatory before any type of PCB assembly because it helps to avoid errors in assembly.
As it helps to avoid errors in assembly so it reduces the cost of PCB assembling and testing. Sometimes at the time of PCB manufacturing, there may be some errors that can cause difficulty in assembly.
So PCB manufacturers should be careful at the time of PCB manufacturing so that manufactured PCBs can be easily ready for assembly.
Types of PCB assembly process:
1. Through-Hole mounting technology:
When you want to build a highly reliable PCB then the Through-hole technology is the best technology to use for PCB assembly.
Through-hole mounting technology is one of the best technology for PCB assembly.
It is one of the most widely used technology for PCB assembly.
In this process the PCB assembly service provider all the components to the exact holes created at the time of printing.
The through-hole technology helps to build a more robust connection than the surface mount technology.
2. Surface Mounting Technology:
Surface mounting technology was developed in 1960 and from 1980 it becomes popular among electronics makers and electronics hobbyists.
In this process, we will solder the components we need.
If surface mount technology is used, then the board must be going through the reflow process again.
So that the solder paste melts and makes a good connection with the components and helps each component to sit firmly.
In this technology components mounted directly to the PCB using solder.
It is one of the most commonly applied technologies used by PCB assembly service providers.
Generally surface mount technology use vias to maintain the connection between various layers.
One of the major advantages of this technology is that it allows the assembler to attach components on both sides of the boards.
It also allows us to use smaller components which helps to reduce the size of the board. So the cost of the final product can be reduced using surface mount technology.
PCB assembly robots
PCB assembly process flow:
Applying Solder Paste:
Applying solder paste is the first step of the PCB assembly process.
In this step, thin stainless steel is used to apply the solder paste to some predefine places of the PCB.
Here the predefine places are defined at the time of PCB designing and also at the time of manufacturing.
These are the place where components will be placed later. Solder mask is basically made of 0.5% of copper, 3% silver, 96.5% tin.
A fixture generally holds the stencil so that the applicator can place the solder paste in the right place.
One thing to keep in mind is that soldering paste should always be used in the right amount.
Then spreads the paste across the stencil to apply it to every corner of the open area of the PCB.
Picking and Placing Components:
Picking and placing component is the most important step for the PCB assembly process.
Now a robotic machine picks all the necessary components and places them in the right places or predefined places.
These components may be surface mount components or SMD components.
After placing all the components they are soldered on properly on the board.
Picking and placing can also be done manually. Before coming to the automated picking and placing technology it was done manually.
Nowadays we are really blessed with advanced technology because helps automatically pick and place components to the right place of the PCB board.
In the manual picking placing and soldering process, there was a high chance of error and lack of accuracy but the automatic process is less time-consuming and it is highly accurate.
At first, the machine picking up a PCB board and place it at the assembly station.
The robotic arms then pick all the necessary components and place them in the exact position on the surface of the soldering paste.
3. Reflow Process:
After placing all the components we have to let them in the same place so that all the components can be attached perfectly to the PCB board. For this, we can run the reflow process.
Now for this, we have to move all the PCB boards to a conveyor belt. This conveyor belt will carry this PCB to the reflow oven.
In this oven, PCB will remain at the heat of 250-degree Celsius. This temperature can easily melt the solder paste.
Now the conveyor belt will carry the PCB to a cooler which will concentrate the melted solder so that all the components can sit firmly on the board.
For double-sided PCB reflow process has to be done for each side individually.
4. Removing the remaining Flux:
Now the remaining flux needs to be cleaned using water and chemicals.
Different types of chemicals are used depending on the type of solder.
5. Error checking and Quality Control:
After completing the reflow process we have to check the error in the final PCB.
Sometimes at the time of the reflow process due to rapid movement components can be misplaced and caused a faulty connection.
Due to misplaced components or fault connections, PCB may not work properly.
So we have to check all the errors and remove all the defective boards.
Another problem is the short connection. Short connections mainly happen at the time of the soldering or reflow process so we have to check all these errors and solve them as much as possible.
Solving error in PCB is always necessary to maintain the quality of the final PCB.
Because if we want a quality electronic product then we have to focus on the quality of the PCB and its assembly process.
Manual inspection is still one of the best inspection processes. For a small amount of PCB batches, visual inspection is enough to test the PCB board.
You can visually check all the components placed on the boards and also realize if there is any misplacement of any component.
As the human inspection process is not always accurate so for the leather amount of boards or complex PCB boards we have to depend on the automatic optical inspection.
Automatic Optical Inspection Process:
In the AOIP process or automatic optical inspection process the AOI machine checks, a large number of PCB boards through its high power camera set at different angles.
These cameras can easily detect the low-quality soldering point quickly which allows us to check a large number of PCB boards in a relatively short time.
Although it is a rare method to inspect PCB it is used by many assembly service providers to inspect deep layer problems of multilayer PCB.
Surface Mount Technology Assembly Process:
In this process, a solder printer is used to apply the Solder paste to the board.
A stencil or solder screen is used to maintain the amount of solder paste that has to be appalled on the predefine places of the printed circuit board.
After applying the solder paste a solder paste we have to focus on component mounting.
Pick and place machine will do place all the components in the proper place.
Now we have to follow the reflow process we discuss above.
In this process, PCB has to pass through a reflow oven which helps to melt the solder paste, and then it will be placed in a cooler to concentrate the melted solder so that it can attach the components to the PCB board.
PCB Assembly Capability:
PCB assembly capability is the capacity of an assembly service provider.
PCB assembly requires high-end technology, especially for complex PCB.
If you want to assemble your PCB from a manufacturer always try to verify their capability.
Check what facilities are available in their assembly unit.
Are they capable of doing both SMT and through-hole technology and they are not able to provide both types of service?
Also, you have to check their testing capability and facilities.
All the top-class manufacturers always try to provide automatic optical inspection as well as x-ray inspection for deep layer inspection.
The soldering paste used during soldering should be of high quality so that it can provide a certain amount of durability to all the components on your board.
Low-quality soldering paste can cause so many problems.
If your PCB is assembled with low-quality soldering paste it may cause a faulty connection.
So be careful before placing your assembly order to any service provider.
How to Find the Best PCB Assembly, Service Provider:
High-end equipment and expertise:
Assembling PCB is not as easy especially when it comes to the Complex.
It needs some of the most latest and High-end equipment and powerful software that can assemble all the components and also able detect errors in each process.
So before choosing a PCB assembly service provider you have to verify whether the PCB assembly service provider can meet all these factors or not.
Depending on that you can choose your assembly service provider.
Another thing is that you have to confirm that your service provider has special expertise in assembling PCB.
Modeling your requirements:
Always try to choose a PCB assembly service provider who can help you, in the beginning, to model the requirements of your board and help you model your requirements with their high-end software.
It is also mandatory to choose those assembly service providers who can test your board once it is completed and can crosscheck all the impedance values you want.
Maintaining Quality to Cost ratio:
Always try to find a manufacturer who is able to provide you higher quality to cost ratio.
Higher customer rating:
Of course, customer rating is a big sign of a good assembly service provider.
After checking all the above factors you have to check the customer rating of a PCB assembly service provider and choose accordingly.
Proper component sourcing:
If your PCB assembly service provider can able to provide all of your components then it is good for you because don’t have to take pressure for component sourcing from a different component seller.
Sometimes few PCB assembly service providers may try to provide you duplicate content to save some money. Be careful about the duplicate content
Some PCB assembly service providers may pass your board on to you without testing it thoroughly.
As a result, you may get into trouble. After you get your boards in hand you may have noticed that they are not working.
For this, you need to contact an assembly service provider who will give you some proof of whether your board is tested or not.
Speed of Shipping:
Before ordering always try to find out the shipping time. Because most of the assembly service provider takes too much time to send your boards. Which may cause so many problems.
So from the above discussion, you can get some idea about PCB assembly and its process.
At present, the demand for PCB assembly is increasing as the demand for PCB manufacturing is increasing to increase the dependence on electronics products.
The demand for PCB assemblies is growing very fast, especially as the demand for customized projects increases.
PCB assembly service is now on the market. The number of PCB assembly service providers is increasing.
However, the points mentioned above should be kept in mind before choosing a service provider for PCB assembly.
If a small quantity is ordered by the board, it can be assembled manually. We hope you find the above discussion useful.
I will try to discuss this in more detail later.