Electronic assembly is the process of putting small electronic components together, typically onto printed circuit boards (PCBs), to make complex circuits or assemblies. There are many types of equipment used in the assembly, including soldering guns, tinning pots, reflow ovens, solder paste dispensers, and hand-held thermal probes. The type of equipment required varies according to the type of product being assembled and its complexity.
Electronic products, both devices and equipment, undergo a rigorous production process before we get to enjoy them for our daily use. While aspects such as electronic design and prototyping receive necessary attention, another critical element includes electronic assembly. It is an aspect you must acquaint yourself with as an electronic engineer or hobbyist. So what does it entail? Who conducts this process, and what should you consider before picking one? The article aims to interrogate and equip you with all the relevant details that pertain to electronics assembly.
Assembly to most people is consolidating and integrating something to a particular platform. While this is true, electronic assembly refers to the integration of electronic circuits into a singular enclosure in the sphere of electronics. It can also imply the soldering of electronic components to a printed circuit board in electronic PCB assembly.
The term electronic assembly is common in electronic circles. Provided you possess the necessary equipment and tools for the assembly process, you can do it solo. But the emergence of electronics assembly services, the intricacies of assembly, and the need to assemble electronics in mass numbers make the solo assembly mission unnecessary.
Electronic assembly and electronic PCB assembly as processes often get used interchangeably. However, a minor difference exists between the two terms. For instance, electronic assembly is more broad-based and covers the assembly of both PCBs and other components in the electronic device or equipment. On the other hand, the PCBA process solely entails assembling components on the printed circuit board.
But to avoid getting all mixed up, the article will deliberate printed circuit board assembly as part of the electronics assembly process. It is also essential to understand that electronic assembly (PCBA) can encompass the DIY process or the automated industrial process. While the two processes essentially undergo a similar process, differences exist in the stages, technologies, and process speeds.
Electronic Assembly Steps
The electronic assembly process can take one of two forms. It can include the DIY process at home or the industry-level mass assembly process. However, the two forms often prove the same save for the equipment deployed, volumes, and technologies. So whether you want to assemble your PCB at home or a contract assembly manufacturer, the following represents the various steps in the electronic assembly process.
The process is akin to how you stencil a t-shirt using a silkscreen. It involves laying a metallic stencil over the PCB board to smear the paste on particular board parts. You can begin with a circuit board panel. In most cases, the panels will come with a total of sixteen copies, which you then merge to form broader or larger boards. A small amount of solder paste (preferably lead-free) is applied to the pad in specific spots where the components will get attached. It is where the stencil comes into play as it hastens the process. Remember, you can accomplish the stenciling process by hand or the stencil machine based on your capacity.
Pick and Place
The process populates the board with electronic components. It immediately follows after the application of the board with paste. Here, the components get placed on the designated spots either by hand or using a machine. Remember, you can assemble electronics using tiny and straightforward equipment instead of large and sophisticated equipment. However, machines make the pick and place process simpler and faster.
It is crucial for the reflow of the paste after the pick-and-place process. It allows for the creation of strong solder joints. A conveyor belt becomes helpful for this process in taking the boards through the reflow oven. The high heat of 250°C plus melts the solder as the board passes through the reflow oven. By encountering diverse temperature zones, the board warms and cools at a regulated rate. It also rapidly cools upon exiting the reflow oven, which fixates the components in their designated spots.
Additionally, the components inaccurately placed need a reworking later. However, the reflow process has little room for error, and thus minor misalignments often self-corrects. It does not imply that functional defects such as tombstoning cannot occur on the board during this process.
Remember, the attachment of components can either be SMD or SMT based on the type of circuit board and its intended application. Additionally, the reflow process for a one-sided PCB to that of double-layered or multi-layer PCBs is different. For a two-sided board with components on either side, the reflow process needs specific considerations. For instance, the side with the most minor or fewest components needs to get reflowed first. After that, the other side gets stenciled, components placed, before another round of reflow process.
The resulting surface tension on the board’s metal is high, which holds the components together and in place. However, fabricating factories with more complex and more extensive assemblies may prove somewhat different. The diverse board bits may get glued in the pick-and-place process to prevent the components from moving during reflow.
It is the next step post the reflow process. The process needs a technician to take the board and manually solder any plated through-hole components. For more extensive production facilities, the through-hole component soldering happens via a wave soldering technique. It is a technique that involves taking the board over an upright wave of molten solder. The molten solder then attaches to exposed metal and component leads on the circuit board.
Diverse design and quantity mixes make it essential and a possibility to attach as many surface mount devices (SMD) as possible. It also requires hand soldering of all the PTH components where you can utilize the Hakko FX-888Dsolder iron or Atten 937b if a beginner in the soldering process.
Inspection and Testing
It comes as the next step and primarily encompasses an automated optical inspection using the AOI machine. The AOI process identifies any parts problems such as missing cap, incorrect resistors, etc. the optical inspection machine often proves quick and utilizes diverse high-power cameras at various angles to observe different sections of the solder connections. Flawed and decent solder fillets (different areas of the solder connection) tend to reflect light differentially. Therefore, the automated optical inspection deploys diverse color LEDs for illumination and inspection of each connection. It performs light operations with incredible speeds and accuracy.
For your PCB assembly’ optical inspection needs, who better trust than RayMing PCB and Assembly? The company not only provides optical inspection services but the whole PCBA process and at cost-effective prices. It runs the boards through an AOI machine for optical inspection and ensures that the right components are used and in the correct spot on the board. It also ensures that no incorrect solder fillets are present nor solder jumpers among adjacent pins. Consequently, defective parts or components get flagged at this point, allowing for continuance with quality and functional components.
Immediately post the board’s inspection, it has to undergo a testing process to ensure functionality. Post the inspection of the board; it is tested to ensure it does what it is supposed to do. However, the testing process of the circuit boards often proves arduous and time-consuming, especially for large volumes. It makes text fixture programs such as Pogo vital for rapid testing. For instance, Pogo pins deploy a loaded head spring to provide electrical connections for different spots on the circuit board for data and power. Additionally, more extensive facilities can deploy the flying probe test in testing the board connections.
The manufacturing process often leaves the printed circuit boards with metal core PCB with residue (flux). For instance, soldering leaves some flux on the circuit board. With time, this flux can become sticky, distort the look of the board, or turn acidic, which then weakens the soldering joints. It, therefore, becomes prudent to wash the board after the board gets inspected and tested. After all, customers deserve the most polished and functional printed circuit boards post-production and assembly.
Cleaning of the boards is possible in a unique dishwasher, especially when assembling the boards on a large scale at a commercial scale. All you need to ensure in this instance entails loading them in the special dishwasher. It (dishwasher) comes as stainless steel and utilizes deionized water for cleaning purposes. Additionally, the dishwasher features high pressure and temperature to function seamlessly.
The washer utilizes a loop system (closed). Post the cleaning process; the washer pushes the wastewater to a basin below it where it collects. It then gets tested for electrical conductivity. When the electrical conductivity proves low (whenever the resistance is high), it indicates the completion of the wash phase. At this point, the water gets recycled via a filtration system that deploys high-quality filters.
So why the deionized water? Deionized water is pure from any ions and thus cannot kill your electronic product when it accidentally gets drenched in it. However, ions in standard tap water will damage your electronic product because of short-circuiting of diverse parts upon contact or submersion. It is also crucial to note that deionized water is toxic for humans. As a result, it helps to take safeguards to avoid accidents when handling the dishwasher. If you cannot access this specialized dishwasher, obtain a crockpot.
Before packaging, it is always essential to ensure that the printed circuit board is dry. However, this step is the ultimate one in the electronic assembly process. Sealing can happen in ESD plastics once the boards have gotten ascertained for their cleanliness and their dryness. The process uses heat to seal each PCB into separate packages of ESD plastic.
Since packaging and picking need to prove, as rapid as possible, most electronic assembly companies ensure the electronic products are pick ready before they go to the shipping division. Consequently, it is prudent to establish a chain of ten pieces with a label (bar-coded) on every end. The barcode possesses the SKU, product name, and a unique batch identify to help track possible problems.
Once the product is wholly packaged, it is sent over to the shipping floor.
Types of Electronic Assembly
A lot of companies provide printed circuit board assembly (PCBA) services. The PCBA process often requires a costly yet straightforward setup. It can involve either one of two types of the electronic assembly in automated PCBA or manual PCBA. However, the modular, prototyping, product assembly also qualifies as a type of electronic PCB assembly.
Automated Printed Circuit Board Assembly
It is a type of electronic assembly that uses automated machines to pick and place components. Other crucial automated machines also include those used to solder the printed circuit boards. Such a computerized assembly system saves plenty of effort and time and is helpful in bulk or batch manufacturing. However, it becomes an expensive assembly process because of the following factors.
- The solder stencil creation process
- Surface mount technology machine programming, primarily for the pick and place process
- Reflow soldering process
- Labor charges
- Solder flux cleaning
- Diverse quality compliance inspections
While such factors contribute to the high assembly costs, they are instrumental in making the assembly process rapid or quick besides proving ideal for mass PCB assembly. It becomes essential to comprehend that the price corresponds to the BOM, type, and size of components. Other factors contributing to the high cost of the automated electronic assembly include capacitors and the 0201 resistors package. Further, the double-sidedness of a circuit board also increases the automated electronic assembly.
Manual Printed Circuit Board Assembly
It is a type of PCBA that entails de-soldering and soldering by hand. The method is ideal for customized product (PCBs) assembly, especially if you need a few prototypes. You do not need a CAD file to place the components as you do it manually automatically for this type of assembly. Conversely, de-soldering needs a gun (hot air) and a solder sucker to pull parts or components from the printed circuit board.
A significant benefit of the manual assembly process entails the ability to de-solder parts at any time. It is an instrumental attribute when it comes to servicing and repairing PCBs. Remember, QFN and BGA components can only get soldered manually to ensure it looks tidy.
Modular, Prototyping, Product Assembly
In this PCB assembly type, the printed circuit board stuffed with parts or components gets assembled within a sheet metal, plastic, or any other similar material enclosure. As a result, electronic assembly service providers resort to deploying three-dimensional modeling software programs such as PRO-E, AUTOCAD, and Solid Works. It is also possible to design a harness or wiring of the whole product.
Electronic Assembly Companies
Electronic assembly companies have a core mandate of manufacturing and testing PCBs, cable harnesses, cable assemblies, printed wiring boards, and wiring harnesses for electronic products. Such products can apply in different industries. While assembling such electronic products can become a reality from home, it is always beneficial to outsource the services from experts. What are some of the benefits of working with electronic assembly companies?
Benefits of Electronic Assembly Companies
Electronic assembly service providers offer flexibility besides easing staffing issues, especially for small and understaffed companies. Since most of these companies deal in the large-scale assembly of electronic products, they pool resources. These pooled resources such as raw materials and their procurement procedure maximize the economies of scale. Further, electronic assembly companies offer value-added services. It includes engineering design, functional testing, manufacturability analyses, trouble-shooting services, etc. Such benefits allow the customer to focus on other aspects of the business. Because of this, customers can constantly adjust and respond to immediate demand spikes for electronic products efficiently and quickly.
How to Pick an Electronic Assembly Company
Plenty of electronics assembly companies indulge in the large-scale assembly of printed circuit boards. While some might view the selection process of a suitable electronic assembly company as difficult, it is often not the case. The process becomes simpler when you understand your assembly needs. One key recommendation, however, is always to source the services of a wide-ranging service provider. The assembler should not only provide assembly of PCBs and products but PCB fabrication, as well. It is also vital for the electronic assembly company to offer product assembly besides deliver of the products.
But what are some of the considerations you should factor in before picking a suitable electronic assembly company? Below are important factors to consider.
Factors under consideration
- It is essential to look for an electronic assembly company that offers an attractive quote (the best) regarding price vis-à-vis the quantity.
- The electronic assembly company also needs to have the least minimum order quantity (MOQ)
- The PCBA company needs to provide larger quantities ranging from 500, 1000, to 10000, especially when the customer’s order is large. Therefore, a company with a larger MOQ proves desirable.
- Electronic assembly company should also possess the least lead times.
- A vital aspect of the PCB assembly process entails the quality of electronic products, which can get discerned upon receiving the consignment post assembly. If the quality proves incredible and the assembly service top-rate, you can consider the PCBA Company for future electronic assembly needs. Additionally, experiences and good reviews from close and trusted allies can also prove pivotal, affirming the reputation of the PCBA Company.
Another way of checking the credibility and quality of assembly services entails the online route. You can check websites such as Alibaba, HKTDC, Aliexpress, eBay, Amazon online. Such options offer valuable alternatives for electronic assembly companies and suppliers you can choose from. But if you cannot distinguish the difference, it is important to consider that a manufacturer owns a production facility, factory, or warehouse. Conversely, an electronic supplier sells on behalf of OEM or factories. Such companies then keep the commission obtained after selling them at a higher cost.
- Always try and approach the electronic assembly or manufacturing company directly. It is better compared to approaching retailers or suppliers, especially on costs, quality guarantee, etc.
- You should check and consider any rating or feedback attached to a specific manufacturer or supplier, especially clients.
- It is also important to get insights about a prospective electronic assembly company from online reviews, especially previous clients.
- Another way of understanding the capability of an electronic assembly company entails checking the pictures of the electronic products. In this manner, you can then visually inspect the quality and see whether it tallies with the image. However, it is never guaranteed that the product’s image will be similar to that of the assembled product. But checking and comparing with what your needs are, is important.
- A supplier that has a money-back guarantee policy proves their commitment and professionalism.
- It is important to shun free delivery electronic assemblies suppliers. Such suppliers take plenty of time to ship your electronic product consignment. At times the shipment period can clock about sixty days to get delivered. Other times, the shipment may not reach you at all. Therefore, always try and choose suppliers who support EMS or DHL delivery.
- Pick a supplier or manufacturer who has an incredible record of prompt response to clients and customers. It ensures that your electronic assembly questions and other correspondence will add value to the quality of the electronic product.
- It is also vital to pick manufacturers or suppliers with the most industry experience besides awards on virtual or online stores.
- Value for money is an important aspect that needs consideration. For instance, the competition has reduced the assembly cost. Therefore, look at companies that can offer quality assembly service but at more affordable prices. Some of the companies, for example, have warehouses and factories in China where they have access to low-cost raw materials and cheap labor that, in turn, ensure low electronic product costs.
Every electronic designer or hobbyist has to understand the electronic assembly process. From what it all means to where to get the services becomes pivotal. After all, knowledge about electronic assembly helps in your design, production, and assembly process. We hope that the insights provided will come in handy in your electronic assembly endeavors.