PCB Manufacturing

From Prototype to Production: Navigating the PCB Assembly House Process

Indide of a PCB Assembly House

The foundation stone of virtually all electronic devices, PCBs (printed circuit boards) are produced via an extensive process involving various steps ranging from designing the prototype to testing the final product. While PCBs come in different shapes and sizes, their fabrication and assembly process is more or less similar. PCB assembly houses are equipped to carry out this entire process with high precision and efficiency. For this, a lot goes into it which may be beyond your imagination. To find out what happens behind the closed doors of a PCB assembly house, scroll down!

Prototype Designing and Gerber Files

PCB Assembly Design and DFM

The first and foremost step is to lay down a detailed design of the PCB to be manufactured. No matter how basic the PCB requirements are, a clear design is necessary to avoid any chances of miscommunication and errors. As you know, the process of PCB fabrication and assembly is an extensive process requiring a considerable amount of time and money. Therefore, if any error or defect occurs, the entire consignment would require rework, further leading to increased cost and turnaround time. To prevent this, all certified PCB fabrication and PCB assembly houses prioritise the prototype designing process.

In this process, designers use PCB designing software, like Eagle, KiCad, Pads, OrCAD, Altium Designer, or a similar one, to create the layout of the desired PCB as per its functionality requirements, suggested budget and device specifications. Then, this design is forwarded for inspection and approval, and once approved, the design files are shared with the manufacturing team, usually in a Gerber file format.

As you know, PCBs may consist of multiple layers. Gerber files allow designers to build and view a PCB, layer by layer. The design layout also gives a glimpse of the effect on supply chain, manufacturability, yield and cost. So, it is safe to say that prototype designing holds the utmost importance in the production process of PCBs.

As a PCB assembly house begins with the prototype designing, the engineers first work on defining the specifications of the PCB board. This includes dimensions of the PCB, number of layers, material type, board thickness, plating finish, impedance control, minimum width/spacing, hole sizes, solder mask, silkscreen, minimum pitch, castellated holes, and RoHS compliance, among others.

The dimensions depend upon the size of the device, however, one has to keep in mind the number of devices to be assembled. If the device is on a larger side, but only a few devices are to be assembled, then manufacturing a larger PCB board would only increase the cost unnecessarily. Similarly, manufacturing a basic rectangular-shaped PCB board is cheaper than fabricating an irregular-shaped one. Therefore, all such factors help designers determine the right dimensions of the PCB board.

The number of layers, again, depends upon the requirements of the PCB and the device. A PCB with more layers is more complex, therefore, multiple layers are included in the design only when it is necessary and not otherwise. The material used by the PCB assembly house for fabricating a PCB can affect the total cost immensely. For example, flexible materials are costlier than rigid ones. However, going with a cheaper option without considering the PCB needs may later lead to PCB defects or chipping/cracking. Similarly, board thickness and all other such factors are predetermined to best suit both budget and PCB requirements.

Design Rule Violations

A PCB assembly house with all the necessary industry certifications will stick to all the design standards throughout the process. For this, designers may use tools like EAGLE DRC, FreeDFM, etc. The tools can help automatically identify and correct violations. While EAGLE DRC allows you to define your own design rule profile, FreeDFM is not very flexible to offer the same. However, it lets you assess the design against most of the common manufacturing standards.

Reviewing Design Files and Documentation

The next step is to generate the Gerber files for the final prototype design. This design file is then reviewed by PCB assembly house before proceeding further. File viewers, like MCN Gerber Viewer (for Mac) and Gerbv (for Windows and Linux), can be used for this. At this stage, designers ensure that everything is rendered clearly and that the design is complete.

After review, the design team documents the stack up and forwards it for production. To avoid any confusion or error, it is necessary that every layer is defined clearly so the manufacturer understands the order and can arrange all of them correctly. A simple .txt file or an Excel sheet can be used for this documentation part. Along with this document, other files, like the one with a graphical representation of the PCB, are saved together in one parent folder which is then forwarded in a .zip file usually.

Preparing Assembly Materials

PCB Assembly Materials

Once a PCB assembly house is done with design and documentation, the next step is to prepare materials, components and tools to assemble the desired PCB. Here, it is necessary to use cost-effective supplies without compromising the quality. Therefore, we at Viasion, ensure that all the components and materials are of the best quality and price to ensure the best results on a limited budget. Additionally, this step may also affect the turn time, so decisions should be made accordingly.

First comes the PCB bare boards designed and fabricated exactly per the specific design. Some PCB assembly houses, like Viasion, are equipped to manufacture them in-house while others buy them from third-party vendors and suppliers. Note that PCB manufacturers in China are especially sought-after for this PCB production as the country’s booming electronics market makes it the best choice for quality and cost-effective PCB solutions.

After PCB bare boards, come the solder stencils necessary for the assembly of PCBs. Solder stencils are required to mark the placements of various components and their thickness determines the amount of solder paste applied. Note that an insufficient amount of solder paste can further lead to improper soldering whereas excess solder paste can lead to solder-bridging. Therefore, to avoid such errors, the quality of solder stencils should not be overlooked.

Now, since Viasion offers one-stop solutions for PCB-related needs, we take care of all such requirements, including solder stencils. In case you hire a PCB assembly house that is equipped only to assemble PCBs, you may need to outsource tasks like PCB fabrication and solder stencil manufacturing. While this may help you save a small amount of money, outsourcing different tasks to different companies can increase the hassle, chances of error and the need to monitor every task separately. Therefore, prefer companies that offer end-to-end PCB fabrication and assembly solutions.

As you must have guessed by now, after PCB bare boards and solder stencil, the next requirement is for the assembly components. Different devices need different components as per their functionality and specifications. The components must also be selected as per the size of the device. What type of assembly technology is used is dependent on the type of components, i.e. SMT is used in the case of smaller components and through-hole technology for assembling bigger components with leads. So, the PCB assembly house should be manned with experienced staff who can help you discover the right components for your PCB needs. Viasion Technology Co. Ltd. excels in finding the best quality PCB assembly components for you at the most competitive prices to provide the best customer experience.

To assemble all the components on the PCB bare board with the help of solder stencil, assembly equipment like a reflow oven, solder paste, pick-and-place machines, etc. are also required. Viasion houses state-of-the-art equipment to minimise the chances of error and fabricate high-precision PCB assemblies. If you are looking forward to setting up your own PCB assembly house, you would need to procure all such assembly equipment to carry out the process.

The Assembly Process

PCB Assembly and Inspection

Once the PCB assembly house has run a Design for Manufacture (DFM) check, and all the required materials are in place, the assembly process begins. It begins with the punching of holes through all the layers and films. This helps in aligning them together at different stages throughout the assembly process. Then, the copper pathway tracing is done. It is necessary to keep cleaning the board to prevent contamination as it may cause open circuits or short-circuits. Then, the technician layers the panels with a photoresist before the board is exposed to UV light. The steps of copper tracing also vary with the number of layers of the board. Afterwards, technicians wash the board with strong chemical preparations to wash away unwanted copper from the board, while the required copper remains protected under the photoresist.

The entire process of PCB fabrication and assembly involves multiple rounds of inspection to detect any error and avoid proceeding further in case of any by PCB assembly house. One such round is carried out at this point. After inspection, technicians align all the layers together and bind them together with the substrate. Holes are then drilled where the leads of the various components are to be connected. However, the leads are connected only after another round of plating and copper deposition on the surface of the holes for establishing connections.

Note, in the case of a single-layered PCB where components are mounted through surface mount technology, many of these steps are not required like drilling. After solder paste placement, the components are directly mounted on the board with the help of automated pick-and-place machines. Then, the board is conveyed through a reflow oven present in a PCB assembly house for soldering.

A final etching round is carried out at the end to protect the desired copper and remove the extra copper. This establishes all the connections properly.

You may think that the PCB assembly is not ready but industry experts know that a PCB is not ready without silkscreening. This process involves the labelling of the PCB as all the vital information and specifications are printed on the surface of the PCB, usually with the help of an ink-jet printer.

While do

cumentation and inspection are carried out throughout the process at various stages, one final round of automated and manual tests is carried out at the end to prevent all chances of errors. Finally, the boards are cut in a way they can pop out from the original panel without using force.

Conclusion

The process of PCB fabrication and assembly is a complex process, the steps of which are subject to the type of PCB to be manufactured, its layers, and other specifications. In some cases, manual assembly processes are also employed due to the specific needs of a project. If you are looking for a PCB assembly house for your PCB prototyping or bulk production needs, look no further than Viasion Technology Co. Ltd. as we excel in the field with 16+ years of experience and 200+ professionals working at our facility day and night to ensure 99% customer satisfaction. So, contact us today to get a quote or to know more!

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