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- December 18, 2022
- PCB knowledge
- (0)
- 09 mins
PCB BOM – a comprehensive guide
PCBs (printed circuit boards) are circuit boards used in the field of electronics that include traces, metal pads, and other parts soldered onto them to form an electrical circuit. A BOM (bill of materials) is typically attached to a PCB to track component inventories or generate inventory reports. The key issue is that while some PCBs don’t include a BOM, some do.
Let’s have a look at what is PCB BOM?
What is BOM in PCB?
BOM stands for Bill of Materials. The bill of materials lists all the components used in your PCB design. It also includes their quantities, which can be used to calculate the project’s total cost.
BOMs are useful for both manufacturers and customers:
●Manufacturers can use a BOM to manage inventory and prevent shortages; they’ll know what parts are needed for each order so that they can order them in time for assembly.
●Customers can use a BOM to track down parts manually or programmatically (e.g., using an Excel spreadsheet).
What is the use of BOM in the PCB assembly process?
The Bill of Materials (BOM) in PCB Assembly lists all components required to build the product.
It can be in the form of a spreadsheet or embedded in the design file.
The BOM is usually created during PCB schematic capture and board layout to ensure that all components are accounted for when building the board. This way, you can make sure to include all of the components and double count them when building your boards.
The BOM is also used to help determine your cost per unit and ensure that everything is accounted for when quoting your jobs to customers.
Different types of PCB BOM
Here are common types of PCB BOM:
EBOM
An EBOM (exploded Bill of Materials) is a list of parts with their quantity, size, color, and other attributes required to build a product. It shows how many parts are needed for each assembly and what assemblies are needed to build one unit.
MBOM
An MBOM (materials bill of materials) is similar to an EBOM but shows how much material is required for each assembly or part. It also shows how much material you need for every unit produced by adding all materials used in all assemblies or parts.
What should a PCB BOM include?
The following items are essential for any PCB BOM:
Part Number — The unique reference number assigned by a component manufacturer. This can be found on the component’s datasheet or packaging.
Quantity — How many of these components are needed? If you’re designing a prototype, you may need to change this value later as you add components or remove them if they’re not being used.
Reference Designator — A shortened version of the part number that identifies each part uniquely within its family (e.g., R1C, Q1). Some companies use their proprietary designators; others use industry-standard designators such as CWR06 for a 6-inch wire-wound resistor (R) 1-ohm value (C).
Description — A short description of what this part does in your circuit or why it’s included in your design.
Phase – The phase name or number. For example, PROJECT A or P1.
Procurement Type – The procurement type name or number. For example, Contractor, Mfg., or Other.
Unit of Measure – The unit of measure for each line item on the BOM. For example, Foot, Inch, Meter, etc. This can be used to calculate cost per unit when using multiple suppliers for the same part number from different countries with different currency conversion rates.
Common mistakes and how to avoid them when creating a BOM list
Several things can be corrected when creating a PCB BOM list. Here are some of the most common:
- Failure to monitor schedule
This mistake is fairly obvious: If you’re not monitoring the schedule and ensuring it’s being followed, your PCB BOM list will be useless. With a well-designed schedule, you can tell if certain project parts are over budget or behind schedule. This is especially important if you’re trying to control costs on the project.
- Wrong team
When creating a PCB BOM list, ensure that your team can create the deliverables in time for your customer’s deadlines. If you have a good team, you might stay caught up on other projects or have to rework deliverables because they weren’t done correctly in the first place.
- Failing to execute the full set of deliverables
While some companies limit their BOMs to hardware, software, or other tangible items, others need to include services and intangibles. A complete set of deliverables ensures a complete supply chain view, which is critical for effective decision-making.
- Inadequately resourced ERPs
Many companies must invest properly in their enterprise resource planning (ERP) systems. This often leads to incomplete data sets or data sources that cannot easily access or integrate into an overall solution framework.
Why do you need BOM management tools for PCB design?
In PCB Design, designers need PCB BOM management tools to identify the components in your designs and their associated costs. Here are some other advantages:
- Provide an inventory of parts for all designs
It’s very important to know the available stock of available parts. The more information you have about your inventory, the better equipped you are to make decisions about new orders and future purchases.
- Provide up-to-date parts information
Keeping track of the availability, price, and availability of components is important not only when it comes to designing new boards but also when making changes to existing boards. As soon as a part goes out of stock, it’s important to know so that you can place an order before it becomes unavailable. This way, you don’t end up in a situation where you have to scrap an entire board design just because one or two critical components are only available now.
- Usually, include component cost information
PCB design software allows you to add components to the design and get an estimated price for each. With this information, you can make better decisions about which components to use and how much they will cost.
- Real-time updating
When you add or remove components from your PCB design, they must be automatically updated in all other documents related to this project (PCB fabrication files, assembly drawings). This is what real-time updating means: once changes are made to a board design, they are immediately reflected on all other documents related to this project.
- Generate customizable BOM reports
Consider generating a custom BOM report that includes only the parts required by a specific job or customer order. You can do this with an easy drag-and-drop interface in most PCB design software packages. Such reports can be used as source documents for purchasing agents or subcontractors who will order components for manufacturing purposes.
How to create a BOM for your PCB?
There are three main ways to create a PCB BOM: manually, through software, or automation.
Tailor your BOM to your needs
Your first step should be to define what information should be included in your BOM. This will depend on what PCB you’re building and whether it’s being produced in-house or outsourced. For example, if an industrial-strength device requires special assembly techniques, this could include information such as torque settings, stencil thicknesses, and soldering temperatures.
Use templates
There are plenty of free BOM templates available online that you can use as a starting point. These templates are designed for specific purposes (such as inventory management), so they might differ from what you need. But they can still give you ideas about how to format your BOM and make it more effective. You’ll find lots of options at our SketchUp BOM Template Library.
Include the right amount of details
When creating a BOM, consider what information is important for others who might need to use it. This could include tube lengths, drill sizes, and additional notes about assembly or installation that would be helpful when ordering parts from suppliers or distributors).
Keep track of changes
If you are working on a project with multiple engineers, it can take time to track all the changes made. Kep has a solution for this problem: You can use Kep to monitor changes and keep track of them. This way, you don’t have to worry about losing track of any modifications that were made to your design in the past.
Limit access
If you have several people working on the same project, limiting access as much as possible is important. If multiple people can view the same design, they might make changes without even knowing they are doing so! With Kep’s restriction features, you can limit access based on specific users or groups within your organization. This will help prevent confusion and duplicate work.
Consider automation
Once you have created a PCB BOM for your PCB manufacturing process, consider automating some parts so that it runs more smoothly and efficiently. One way to do this is through scripting — which allows you to automate certain actions in Kep by writing code that performs certain processes when triggered by specific events or conditions within the software.
PCB BOM example
Here is an illustration of a small component from a PCB BOM that includes some of the details we have already covered. The clean, orderly, and appropriately labeled sheet is the first thing you’ll notice. Along with the part number, quantity, and description, it also includes the manufacturer’s name. Recognizing that every business may have a unique BOM, use this illustration to illustrate the range of a strong bill of materials.
BOM stands for Bill of Materials. The bill of materials lists all the components used in your PCB design. It also includes their quantities, which can be used to calculate the project’s total cost.
- Part Number
- Quantity
- Reference Designator
- Description
- Phase
- Procurement Type
- Unit of Measure
- Tailor your BOM to your needs
- Use templates
- Include the right amount of details
- Keep track of changes
- Limit access
- Consider automation
Final words
The bottom line is that a BOM is an important tool in your arsenal when developing your next PCB. Because it includes absolutely everything needed to manufacture the board, it’s vital information that can help with any discussion related to parts procurement. Compliance won’t be an issue if you keep your board’s BOM on hand and check it every time you get a quote from a manufacturer.
And since the process of creating PCB BOM for multiple boards is quite straightforward, as long as you know what you’re doing, you shouldn’t have too much trouble staying on top of things.
