Professional PCB Manufacturing: A Key Step to Bring Your Product to Market
While hand-populating and soldering printed circuit boards (PCBs) on a repurposed electric hotplate may work well for prototyping products, it is not efficient or reliable for producing a significant number of PCBs needed for a product sold to customers or backers. To ensure proper functionality and quality, a PCB assembly (PCBA) service is essential for manufacturing and assembling not only the bare PCBs but also all the components on the board. Many PCBA services also offer testing to verify the functionality of each board before integration into the finished product.
PCBWay manufactured and assembled this LED controller module for a decorative lighting project.
What is the Process of PCBA (Printed Circuit Board Assembly)?
Seeed Studio’s flowchart illustrates the PCB assembly process, outlining the steps involved in producing a complete circuit board.
After each step of the assembly process, the boards go through various inspections to ensure quality. Some inspections are automated using computer vision systems, such as automated optical inspection (AOI) machines. These machines check if the amount of solder paste applied to each pad on the PCB is correct and accurate.
After each step of the assembly process, the boards go through various inspections to ensure quality. Some inspections are automated using computer vision systems, such as automated optical inspection (AOI) machines. These machines check if the amount of solder paste applied to each pad on the PCB is correct and accurate.
After the solder paste application, the boards are placed in an oven that melts the paste and establishes electrical connections between the components. The oven has a specific heating curve, and the boards are conveyed through the oven using a conveyor belt.
For through-hole components, the process is slightly different. These components are usually placed by hand and then soldered using a solder wave machine. The machine uses a small fountain of molten solder to quickly solder all the components’ legs on the underside of the board. The solder mask applied to the PCB ensures that the molten solder only sticks to the component legs and PCB pads.
Once the PCBA is completed, it undergoes a series of quality and functional tests. The boards are inspected to ensure that all parts are correctly assembled, and a flying probe tester is used to test all connections against the reference design. If offered by your PCBA manufacturer, functional testing is performed before shipping.
In this YouTube video by Strange Parts, he takes us on a tour of a printed circuit board assembly facility run by PCBWay. This is the company we will use in this article for our example PCB manufacturing.
Below is a YouTube video tour of PCBWay, a printed circuit board assembly facility, by Strange Parts. PCBWay is the service we’ll be utilizing in this article to have a sample PCB fabricated.
Prepping Files for Printed Circuit Board Assembly (PCBA)
To place an order for printed circuit board assembly, you need to prepare several files, including:
- Gerber files: These files are used to manufacture the bare PCB itself.
- Bill of materials (BOM): A BOM lists all the parts used in the design along with other relevant information required to source the parts and correctly place them on the PCB.
- Centroid file: Also known as insertion file, pick-n-place file, or XY data file, it is used to program the machines used to assemble your PCB.
- Assembly drawings: These are used to verify your design, for manual assembly and soldering, for rework, and for testing.
- Photos of a finished prototype board: These can be generally helpful for clearing up any ambiguity in your design files.
To begin the process of preparing the required files for PCB assembly, you first need to have a completed design. For the purpose of this guide, the control unit of a Borilux LED lighting project was designed using Autodesk Eagle.
It is advisable to prototype your circuit in addition to completing the design before proceeding with the process of preparing the files required for manufacturing and assembly. The cost of the boards, sourcing and shipping components, assembly, file preparation, and delivery charges for completed PCBs can be considerable with PCBA. Moreover, lead times for PCBA services usually take at least a couple of weeks. Therefore, it is wise to ensure that your circuit design operates as expected before investing your valuable time and resources into PCBA.
In this tutorial, PCB assembly services from PCBWay are used as an example. PCBWay is a renowned PCB manufacturing company that offers comprehensive PCBA capabilities. One of the advantages of PCBWay is its low minimum order quantity, which is beneficial when working on late-stage prototypes. This means that you won’t have to pay for a large number of prototype-assembled PCBs that you may not need. The process for preparing files and placing an order with PCBWay is similar to other manufacturers, but it is always recommended to review the documentation of your specific manufacturer to ensure that you are following their specifications for file preparation and other requirements.
Creating Gerber Files
If you have experience with manufacturing blank PCBs, you might be familiar with Gerber files. Generating Gerber files from an Autodesk Eagle design is also discussed in other articles. To recap, to generate Gerber files from an Eagle design, click on the CAM Processor button in the toolbar.
To generate Gerber files from a design in Eagle, first, click on the CAM Processor button in the toolbar. Then, load a CAM job file that specifies how to format the Gerber files according to your manufacturer’s requirements. Most PCBA services offer a CAM file for download. For PCBWay, a profile developed by SparkFun Electronics is recommended.
To download the CAM job file, visit the SparkFun Eagle Settings repository on GitHub. This repository offers many useful resources for Eagle, such as various CAM profiles. It is recommended to download the entire repository as you might want to use other resources provided by SparkFun.
Once you have downloaded the SparkFun Eagle Settings repository from GitHub and extracted the .zip file, you need to locate the sfe-gerb274x-2layer.cam file in the SparkFun_Eagle_Settings-master/cam directory. Copy this file and paste it into your Eagle CAM directory, which is usually located in Documents/eagle/cam or a similar directory depending on your system.
To proceed with generating Gerber files, open Eagle and access the CAM processor dialog box. Select “Open CAM File” from the Load Job File dropdown menu if you are using PCBWay for manufacturing your electronics.
Before exporting the Gerber files, make sure to select the “Export as ZIP” checkbox in the configuration options.
Once you have selected the appropriate CAM job file and configured the settings, the next step is to export your Gerber files. To do this, make sure the “Export as ZIP” checkbox is selected and then click the “Process Job” button. You will be prompted to choose a directory in which to store the .zip file containing your set of Gerber files. These files will be sent to PCBWay to manufacture the bare PCB for your design.
Sourcing Parts
Before discussing the bill of materials, it’s essential to understand the various part sourcing options that are generally available for PCBA services. For PCBWay, there are multiple ways the manufacturer can obtain the components needed to assemble your boards. The sourcing option you choose affects the lead time required to manufacture your boards, the cost per board, minimum order quantities, logistics costs, and any additional work required before your PCBs can be assembled.
Consigned/Kitted: In a consigned part sourcing model, the PCBA customer buys all the components in the design and ships them to the manufacturer. The parts are put together in a kit, and the package includes all the parts required to manufacture the needed quantity of parts along with paperwork listing all the parts the kit contains and information on the PCBA order to which the kit belongs.
Consigned part sourcing can be attractive to product developers because it allows for a higher level of control over the design and manufacturing process. The product developer can ensure that parts are ordered correctly, there are no errors, and the design is well-managed. It is also useful if a design uses unique or difficult-to-obtain parts that the PCBA manufacturer may not have access to. Additionally, consignment provides intellectual property security.
However, the primary downside of consignment part sourcing is the work involved in tracking inventory, handling international shipping, putting together kit documentation, and doing part purchasing. For in-development products, developers may prefer to spend this time continuing to work on bringing the product to market.
Full Turnkey: With turnkey PCBA services, the manufacturer handles both the manufacturing PCBs and sourcing all the necessary components. This option allows the entire manufacturing process and part sourcing to be outsourced. The product developer provides the PCBA manufacturer with a detailed bill of materials, and the manufacturer obtains all of the parts using their preferred vendors (typically large distributors like Mouser and DigiKey).
The benefit of turnkey part sourcing is that it allows small teams of developers to focus on development, marketing, and sales rather than manufacturing. Turnkey sourcing also allows companies to be more agile in responding to changes in market conditions or demand. However, turn-key sourcing can also carry additional risks, such as incorrect parts orders due to misunderstandings in design or accompanying documentation. Additionally, turnkey sourcing can be more expensive than using a consignment model because some PCBA manufacturers charge a percentage of the total cost of parts or for the work involved in sourcing parts.
Partial Turnkey: Product developers can also choose to use a combination of consignment and full turnkey part sourcing options. The critical or less common parts of a PCB design can be purchased by the product developer and shipped to the manufacturer, while commodity parts are sourced by the manufacturer. For example, if you are developing a product with microcontrollers, LEDs, custom connectors, or other important components, you can source those parts yourself while leaving the manufacturer to source things like capacitors, resistors, and other common components.
Generating a Bill of Materials
A bill of materials (BOM) is an essential document required for getting your PCBs assembled. It contains a list of every component used in your design, along with reference designators for each part, manufacturer part numbers, and other vital information that allows the PCBA company to assemble your printed circuit board accurately. Having this information is crucial for the PCBA company to correctly assemble your PCB and source the necessary parts.
The bill of materials (BOM) is another essential file necessary for assembling your PCBs. It includes a list of all the components utilized in your design, along with reference designators, manufacturer part numbers, and other crucial details that aid in the correct assembly of your printed circuit board according to your specifications. However, the specific information contained in your BOM will vary depending on your part sourcing strategy (consigned, full turnkey, or partial turnkey). For PCBWay, your BOM should generally include the information listed below. Keep in mind that a member of the PCBWay team will review your BOM and may contact you if they need additional information or verification of any of the components listed.
For the different strategies of part sourcing (consigned, full turnkey, or partial turnkey), the required information for the bill of materials (BOM) will vary. Below are the information that PCBWay requires for the BOM depending on the sourcing model chosen:
Consigned/Kitted Part Sourcing BOM
- Line#
- Quantity per Part Number
- Reference Designator
- Part Number
- Part Description
- Package
- Type (Surface mount, Thru-hole or Hybrid)
Turn-key and Partial Turn-key Orders BOM
- Line#
- Quantity per Part Number
- Reference Designator
- Part Number
- Part Description
- Package
- Type (Surface mount, Thru-hole or Hybrid)
- Manufacturer’s Name
- Manufacturer’s Part Number
- Distributor’s Part Number
It’s important to note that the PCBWay team will review the BOM, and if they have any questions or need clarification on any component, they will reach out to the customer.
Generating a BOM with Eagle
Depending on the organization of your project, you may already have a list of parts used in the design of your PCB, in which case you can create the BOM for your PCBA manufacturer based on that list. However, if you don’t have such a list, you can use the BOM export tool in Autodesk Eagle to generate one from your design. One such tool is the SparkFun-BOM_Generator.ulp, which can be downloaded from the SparkFun Eagle Settings GitHub repository. Although Eagle does come with its own BOM generator ULP, the SparkFun version is more user-friendly and flexible.
To utilize the BOM, you need to open your BRD file and select the “Run ULP” button located in the toolbar.
First, navigate to your BRD file and click on the “Run ULP” button in the toolbar. After that, click on the “Browse” button and select the SparkFun-BOM_Generator.ulp from the previously downloaded SparkFun Eagle Settings repository. The dialog box for the ULP will open, and it will have two main sections. The left section displays all the parts that will be included in the BOM, while the middle panel shows the part designators that will not be added to the BOM, such as wire pads that have designators but no actual components. To control which parts will appear in your BOM and which ones will not, you can move groups of parts back and forth between these sections.
Once you have finalized the BOM list, you can export it as a CSV file.
After exporting the BOM as a CSV file, it can be imported into various spreadsheet programs like Google Drive or Microsoft Excel. Once the BOM is imported, you can add any necessary information you want to include in the document.
Generating Centroid Files
The final document necessary for placing an order for your PCBA has various names. It is called a centroid file, pick-and-place file, or XY data file, which provides information about the placement of each surface-mount device (SMD) part on your PCB, including its reference designator, coordinates, and rotation. When submitting your design to most PCBA manufacturers, such as PCBWay, you will need two centroid files, one for the top side and one for the bottom side of the board. Even if your design does not have any components on the backside, generating the centroid file for the backside can be useful for clarity.
The data in the centroid files is organized as a list of values separated by commas.
The pick-and-place machines are programmed using the information in the centroid file, which is critical for the PCBA manufacturer to ensure that each part is placed on your board correctly, with the right position and orientation.
Creating Centroid Files using Eagle
Generating centroid files in Eagle is a straightforward process. The Eagle software provides a feature that enables users to export centroid files for their designs. To export centroid files, open your BRD file and navigate to the menu bar. Click on File, then select Export, and choose Mount SMD.
After selecting the “Mount SMD” option under “File” > “Export” in Eagle with your BRD file open, you can then choose a location to save your two centroid files. It’s recommended to save both files in the same location.
Collecting Supporting Materials
We have discussed the necessary files required to manufacture and assemble your PCB, which include Gerber files, a bill of materials, and centroid files. However, you may also provide additional information to help your PCBA service better comprehend your design and assembly requirements. These supporting materials don’t follow any standardized format, and you should focus on any documents that avoid misunderstandings between you and your PCBA service, as mistakes can be expensive.
Assembly Diagrams can be a helpful supporting document that ensures your PCBA service comprehends the location of the components that require mounting on your PCB. An assembly diagram is a chart that shows the various components and their values that belong in different positions on your PCB.
We have discussed the necessary files required to manufacture and assemble your PCB, which include Gerber files, a bill of materials, and centroid files. However, you may also provide additional information to help your PCBA service better comprehend your design and assembly requirements. These supporting materials don’t follow any standardized format, and you should focus on any documents that avoid misunderstandings between you and your PCBA service, as mistakes can be expensive.
Assembly Diagrams can be a helpful supporting document that ensures your PCBA service comprehends the location of the components that require mounting on your PCB. An assembly diagram is a chart that shows the various components and their values that belong in different positions on your PCB.
Placing your PCBA Order with PCBWay
At this stage, you have all the necessary files to place your PCBA order, including:
- Gerber files that contain the necessary information for the PCB manufacturer to fabricate your boards. Each Gerber file represents a different layer of your design.
- The Bill of Materials (BOM) that lists all components in your design, including reference designators and other relevant information for sourcing parts.
- Centroid files that enable your manufacturer to program their pick-and-place machines, listing all SMD components in your design and their placement coordinates and orientations.
- Additional materials such as assembly diagrams and prototype photos that can assist your manufacturer in comprehending your design in its entirety and avoiding potential misunderstandings that could impact the final product.
With all these files in hand, you can proceed with placing your PCBA order. Simply navigate to PCBWay’s ordering page.
Bare PCBs Ordering
To order your bare PCBs from PCBWay, you need to fill out the necessary information in the first section of their ordering page. Below are the parameters you need to specify and their respective explanations:
| Parameter | Explanation |
|---|---|
| Board type | This asks if your design files are for a single board or a panelized set of PCBs. For this tutorial, we will use single pieces. If you are creating a panel, you can choose to design it yourself or have PCBWay do it for you. |
| Different Design in Panel | If your design is not a panel, enter “1”. If you are making a panel, your panel might contain multiple copies of a single PCB design or multiple different designs. |
| Size | This is the size of the smallest rectangle that can fully enclose your design. You can find this information on the Eagle Control Panel. |
| Quantity | This is the number of bare PCBs you want to be made. This quantity will most likely match the quantity of boards you plan to have assembled unless you have a specific reason for wanting both assembled and bare boards. |
| Layers | This is the number of layers your PCB has. In this tutorial, we have a 2-layer board. |
| Material | This parameter designates the material from which your PCBs will be made. For this tutorial, we will use FR-4. |
| FR4-TG | This stands for “FR4 glass transition temperature” and specifies the maximum temperatures your PCB substrate is designed to withstand. TG 130-140 is the standard value. |
| Thickness | PCBs can be made in various thicknesses, but the most common thickness is 1.6mm. |
| Min Track/Spacing | This parameter specifies how fine the traces on your PCB are and how closely they are spaced. A tighter spacing will increase the cost. The typical value is 6/6mil. |
| Min Hole Size | This parameter specifies the smallest hole diameter in your design. |
| Solder Mask | You can choose to get your PCB made in a variety of colors. Green solder mask has the best performance, but you can opt for different colors based on your preference or project requirements. In this tutorial, we chose white as the solder mask color because it is for an LED lighting PCB. |
| Silkscreen | You can also choose the color of the silkscreen for your PCB. Depending on the color of your solder mask, you may not have a choice in silkscreen color. For example, if your solder mask is white, you cannot choose a white silkscreen. |
| Gold fingers | Gold fingers are a design feature used to allow a PCB to be plugged into a socket. You may be familiar with this design feature if you’ve ever assembled a PCB. Graphics cards and other PCI devices have gold fingers to plug into the motherboard. |
| Surface finish | There are several different technologies for applying a finish to the SMD pads and plated through-holes on your PCB. In this tutorial, we will use HASL lead-free because it is inexpensive and does not contain lead. |
| Via Process | You can generally ignore this parameter because Eagle specifies a via process, and PCBWay will use that setting even if you choose a different option on the ordering page. |
| Finished copper | This parameter specifies the thickness of the copper layer on the plated FR-4 from which your PCB will be made. The thickness of copper is expressed as a weight of metal per square foot of board area. The default value is 1 oz Cu. |
| Extra PCB product number | PCBWay will print a number on your PCB that allows them to identify and track your boards through the manufacturing and assembly processes. If you want this number omitted, there is an extra charge. |
When you select the .brd file in the Eagle Control Panel, you can easily find the size of your PCB displayed.
Gold fingers are a specific type of connector used for board-to-board connections.
Naturally, you have the flexibility to modify any of these settings based on the specifications of your project.
Naturally, you have the flexibility to modify any of these settings based on the specifications of your project.
Once you select the checkbox, you will be directed to another set of parameters that you need to configure for your PCBA order.
| Parameter | Explanation |
|---|---|
| 3 flexible options | First, you can select the type of part sourcing to use, as discussed above. In this case, I am using the Turnkey service. |
| Board type | Next is the type of board you want to have assembled. This parameter should be set to match the Board Type parameter in the above section. |
| Assembly side | You will also choose which side of your PCB has components mounted to it, the top size, the bottom side, or both sides. |
| Quantity | You will again select the order quantity. This parameter will probably match the quantity parameter from above. |
| Number of unique parts | This parameter specifies the total number of different types of components in your design. This parameter does not indicate the total number of parameters, just the number of different types… |
| Number of SMT parts | …this parameter indicates the gross number of SMT parts in your design. |
| Number of through-hole parts | You will also indicate how many PTH components your design uses. |
After inputting and reviewing all the required information on the ordering page, click the “Calculate” button. On the right-hand side of the page, you can select your desired PCB build time. The standard build time is typically 3-4 days, but you can choose to expedite your order for an additional fee. It’s important to note that the build time does not include the time required for PCBWay to obtain the parts for your project, whether you are shipping the components or selecting the turnkey option. Also, the final price shown on the page does not include the cost of components if you choose turnkey as your part sourcing option.
“After entering all the necessary information about your design files in the PCBWay ordering system, the next step is to upload the design files themselves. There are three upload buttons for image files: the first for your Gerber files in a .zip archive, the second for your BOM in either Excel format or CSV, and the third for your centroid files, along with any additional files, in a .zip archive.
After submitting all the required design files, the PCBWay team will review your order to ensure that there are no issues with the Gerber or centroid files or any other information provided. If any issues are found, they will contact you via email.
If you opt for turnkey or partial turnkey part sourcing, you will receive an updated BOM with pricing for each component in your design along with the lead time required for PCBWay to procure your parts. This updated BOM will be sent to you within a day or two after you place your order.
After submitting all the required files, the PCBWay team will review your order, which includes verifying the correctness of your design files and other details you provided. In case of any issues, PCBWay will contact you via email.
If you opt for turnkey or partial turnkey part sourcing, you will receive an updated BOM a day or two after you place your order, which includes pricing and lead time information for all the components in your design. You can review this BOM and make any necessary changes before giving your approval for PCBWay to proceed with manufacturing and assembling your boards.
Before shipping, PCBWay will send you an email with photos of your assembled boards. You should carefully examine the photos and check that all components have been installed correctly in the right places and orientation. This gives you the opportunity to give the boards your final approval before they are shipped out. The final cost of getting your boards made will be the price you paid when placing your order, plus the cost of the components listed in the updated BOM.
After you have given your final approval for the assembled boards, PCBWay will proceed to ship the fully assembled PCBs to your address.
Conclusion
Transitioning from manual assembly of your PCBs to professional assembly by a PCB assembly company such as PCBWay is a crucial step towards introducing a new product to the market. If you have already developed a few prototype PCBs, the process of having your boards assembled professionally only requires creating a few extra files.
| File | Purpose |
|---|---|
| Gerber Files | This set of files gives your PCBA manufacturer the information needed to make your blank PCBs. |
| Bill of Materials | This is a list of components in your design, along with reference designators. |
| Centroid Files | This pair of files is used to program pick-and-place machines so they know where each of the components in your design belong and in what orientation they should be mounted to your boards. |
| Supporting Materials | These optional files can include assembly diagrams, photos, or other resources that will help ensure there are no miscommunications between you and your PCBA manufacturer. |
When opting for professional PCB manufacturing, you must also choose a part sourcing method. Your PCBA manufacturer can obtain all the required components for building your design in several ways.
| Part Sourcing Method | Description |
|---|---|
| Consigned/Kitted | One option is for you to get all the components needed for your design yourself, package them up, and send them all to your PCBA manufacturer. |
| Full Turnkey | Some PCBA manufacturers, like PCBWay can handle all of the part sourcing for you. |
| Partial Turnkey | You can go with a combination of consigned and turnkey part sourcing. Generally this involves sourcing the more important parts of your design yourself, and leaving your PCBA manufacturer to source the more common parts. |
Employing the services of a professional PCBA company enables you to scale up your production to meet the demands of your orders, without the risk of quality issues that can arise from building the electronics yourself. This helps to prevent bottlenecks and ensures that your products are consistently produced to the highest standards.