The assembly of circuit boards is one of the last stages of the design before the bard is tested and shipped. Working with a reliable PCBA company helps break down the barriers to doing all these, as the designer fixes any issues that may arise due to the board’s design.
Working with the designer comes with a lot of perks, most especially, if the company is a contract manufacturer. You can expect everything to be in-house – from sourcing the components to fabricating and assembling the components on the board.
In this article, we aim to inspire you with ideas on how to pick the best PCB manufacturing company.
What is PCBA Manufacturing?
It is the process of assembling the parts or components on a Printed Circuit Board (PCB). It is also called the “finished PCB,” due to the fact that all the necessary components must have been installed, added or soldered to the PCB’s surface.
Usually, after the assembly process is over, the PCB company subjects the board to a series of tests, ranging from In-Circuit Testing (ICT), In-Line Automated Optical Inspection (AOI) and Flying Probe Testing.
These tests are used to validate the board’s performance. If some issues or design errors are noticed, the PCB assembly house fixes those before shipping the circuit.
The Traditional Process of PCB Assembly
There are different kinds of processes used for making assemblies of components on circuit boards. However, the traditional or conventional process still reigns supreme.
If you are considering taking to this path, here are the exact steps to take:
1. The Application of Solder Paste
The first step is to apply the solder paste on the PCB. For this process to work, a careful observation must be made of the areas. Due to the intricacies and the smaller real estate on the board, it might be difficult to apply the solder paste. Besides, the paste cannot be applied all at once.
Therefore, the following best practices should be followed to the latter;
- Use stencils of different shapes and sizes should be used to help the navigation and application of solder paste in the respective areas/locations in the PCB.
- The solder paste should only be applied where it is needed in the board.
2. Component Placement on the PCB
Hillman Curtis helps you source for the components to be assembled on the PCB. Once we have the components, we proceed to place them where they are needed on the board.
We strategically place or mount the smaller parts on the solder paste board. It is to be noted that there are two major ways to go about the component placement – via robotic (pick and place) mechanism and manually.
3. Reflow for Solder Solidification
It is important to make the solder paste solid on the board. This is the reason for using a reflow process to subject the circuit board to a 500-degree reflow oven to solidify the solder paste.
The first process is the melting of the solder paste in the reflow oven. Once this is attained, the next step is to take the PCB back to the conveyor, where it is exposed to a cooler to solidify the solder paste.
4. Circuit Board Inspection
With the solder paste now solid on the board, the board is now subjected to “criticism.” At this point, it is inspected to verify the overall functionality of the components.
It is to be noted that the inspection stage brings the following to bare:
- Poor quality connections
- Misplaced components and;
- Electrical short-circuiting
It is to be noted that the reflow process is usually a factor for these poor performances. Due to the processes used, the PCB components might not function as expected.
With the help of Automated Optical Inspection (AOI), manual checks or x-rays, we will find out some existing problems with the components and have them fixed.
5. Through-Hole Component Insertion
The two common processes for inserting PCB components are via Through-Hole Technology (THT) and Surface Mount Technology (SMT). The former, THT, is commonly used.
So, at this stage, the manual or wave soldering process is used to insert the parts into the PCB.
6. Final Inspection
The PCB is almost ready after the components have been assembled. At this stage, the board is subjected to a final series of inspections. The electrical performance is the priority here and for this to be verified, the PCB would be subjected to testing under different voltages and currents.
7. Board Cleaning
A PCBA process that goes through the final stage of inspection successfully is now cleaned with deionized water. This is done to help remove the residues that are left on the board during the soldering process.
When the board has been washed, it would be dried via the placement under compressed air.
8. Packaging and Shipping
The Printed Circuit Board (PCB) is now ready. It will be packaged appropriately and shipped for an onward usage in the targeted electronic products.
Types of PCB Assembly
The assembly of circuit boards comes in different types. Understanding how all these work makes the difference on the one you choose to go for. The following are some of the common types of assembly processes used for Printed Circuit Boards (PCBs):
1. Rigid-Flexible PCBA
Also called the Rigid-Flex PCBA, it is a type of assembly process that combines the unique features of the rigid and the flexible circuit boards.
The features include a constant state of flexibility (for modifying the board for different uses), and molding of the same into flexed curves, especially during the installation or manufacturing stages.
The construction process of the rigid-flexible PCBAs include:
- Construction from the several layers of flexible circuit substrates.
- The substrates, depending on the design of the target applications, can either be externally or internally connected to one or more rigid PCBs.
2. Through-Hole Technology (THT) PCBAs
These are the circuit boards made with the Through-Hole Technology (THT). It involves the use of Pin-Through-Hole (PTH) components, inserted through holes before they are drilled into the PCB.
The following steps are tenable when making a PCBA with the THT process:
This process requires a manual placement of the THT components on the board’s surface. It requires precision and speed – two of the major distinguishing factors that we offer at Hillman Curtis.
The components are inspected to be sure they are accurately-placed and are positioned where they are meant to be on the board.
Wave Soldering Process
This is the third and last process in the THT PCBA design process. It entails the movement of the circuit board over a 500˚F. The movement is done in a slow, wavelike motion.
After the heating/wave soldering process is completed, the PCB would then be placed in an open place/cooler for it to be dried and for the connections on the PCB to be solidified.
3. Surface Mount Technology (SMT) PCBA Process
This is often regard as an opposite of the THT process of assembling components on the PCB’s surface.
Although it uses the same three-step model as the THT, the SMT PCBA process is best for the complex applications.
The overall design concept includes making a direct placement or mounting of the PCB components with the help of a solder paste.
The following are the steps are used when making PCBAs with the SMT process:
Solder Paste Printing
The first step is to print or apply the solder paste on the PCB’s surface. For the best results, a solder paste printer is to be used for this process.
Note also that the following are worth having in mind when making the solder paste printing:]
- A template of stencil or a solder screen must be used. It helps to highlight where the solder paste is to be applied on the board.
- The solder paste application process should be smooth and cover only the correct or outlined places where the components are to be applied on the PCB.
The assembly process is now about to begin. The process is usually automated with the help of a robotic pick and place mechanism.
In addition to speeding up the process, the use of a robotic pick and place mechanism helps in the following ways too:
- It ensures the mounting of the components or the Integrated Circuits (ICs) on the corresponding pads.
- The automated process is further enhanced by the usage of component reels in the pick and place machine. These reels are responsible for the rotation to help supply the components to the pick and place machine.
The last step in the SMT process of PCBA is to pass the board through a 23-foot-long furnace, also called the reflow oven. It is to be subjected to a 500˚Ftemperature to aid the melting of the solder paste.
The solder paste must have been melted and form a strong bond between the PCB’s surface and the components.
Once the bond has been established, the PCB is then removed from the reflow oven and passed through the coolers where it will be cooled – and the components fixated at the respective locations on the board.
4. Mixed PCB Assembly Services
This is another type of PCB assembly. It involves the combination of the Through-Hole Technology (THT) and Surface Mount Technology (SMT) processes.
This combination is necessitated by the fact some PCBs cannot be assembled with either the SMT or THT processes. Thus, the combination of the two helps to facilitate the process.
Here are some facts about the mixed assembly process for PCBs:
- Solder paste is not used for this process.
- The surface mounting process is often used to place the components on the board.
5. BGA PCB Assembly Process
This process of assembling Printed Circuit Boards (PCBs) is based on the concept of Ball Grid Array (BGA). The features include:
- The PCB’s performance at higher speeds is enhanced by the traces connecting the package’s leads to the wires or balls. These balls or wires are shorter and are used to connect the die to the package.
- The BGA PCB assembly process bolsters heat conduction via the external dissipation of heat from the IC.
The Differences between Automated and Manual PCB Assembly Processes
The two major processes of assembling components on a PCB are automated and manual. They are based on the Surface Mount Technology (SMT) and Through-Hole Technology (THT), respectively.
On the one hand, the automated process helps to facilitate the component placement with the use of a robotic pick and place machine/mechanism.
The manual PCB assembly process, attributed to the Through-Hole Technology (THT), involves the placement and separation of the components, based on the shape, size and heat sensitivity.
While the manual process takes a lot of time, it can also be beneficial due to the streamlined process of conducting heat away from the board and ensuring that the components are accurately-spaced.
How to Choose the Best PCB Assembly House
The best Printed Circuit Board Assembly (PCBA) companies have a couple of unique operating capabilities, such as:
- Experience: the top PCB assembly companies have extensive years of experience assembling components on top of a PCB’s surface. At Hillman Curtis, we are the best when it comes to streamlining your PCBA needs in one house. We handle the component sourcing, board fabrication, testing, assembly and final inspections of your PCBs.
- Manufacturing Costs: as a contract manufacturer, we work with your budget, while offering the best PCB assembly service.
- Quality Assurance: this has to do with the expected quality of your PCBA, as per the industry standards. The company has the necessary certifications, especially the ISO9001:2015, UL, RoHS and BSCI.
Get Your Circuit Board Assembled at Hillman Curtis
As a 24-hour PCB manufacturer and assembler, Hillman Curtis is always ready to take your orders. Due to the assembly process, we expect our customers to be clear about their requirements. For example, if you are looking to have the PCB assembled via manual assembly, we would ask you to make separate columns in the Bill of Materials (BOMs) to specify the precautions and any special requirements you would like to be taken for the manually-assembled PCB components.