The Bill of Materials, popularly known as BOM plays a crucial role in the design and manufacturing stage of all electronic devices, starting from circuit boards. Without a detailed BOM, the project may need some revisions that make cause delays during production. Therefore, the BOM is one of the most critical aspects in PCB manufacturing.
Most times, manufacturers ask their customers to upload their BOM list whenever they submit an order. However, knowing the information a BOM should entail is crucial in designing one. Also, bill of materials should contain the necessary information. BOMs offer several benefits to both electronic manufacturers and customers. Therefore, it is important to understand what the bill of materials entails before designing one.
What is a Bill of Materials?
The bill of materials is regarded as a list of materials, components, and assemblies for product manufacturing. The information in the bill of materials is crucial for production. Therefore, manufacturers must depend on these pieces of information to manufacture a product. The BOM must be well detailed and very accurate. The success of a production depends on the BOM.
BOMs are both crucial to customers and manufacturers. For instance, it helps a customer to express their needs when they order circuit boards. Therefore, the PCB assembler uses this information to fabricate the circuit board or electronics according to the requirement of the customer. Also, you can refer the BIOM as an ingredient list for manufacturing a product.
As regards PCB design, the bill of materials is a detailed list that comprises all the components and parts for PCB manufacturing. BOM helps to easily track progress during production. A bill of materials is critical in PCB design. Therefore, a BOM must be accurate and not allow any potential misunderstanding.
All manufacturers begin with the production process by creating a BOM. This is because the BOM provides basic information about the product. BOM is not only used in the electronics industry, it is used in other manufacturing industries. Also, the BOM enhances production as the stages evolve.
What should a BOM Include?
A bill of materials must include specific information about the manufacturing process of a product. Below are high-level information a BOM should include:
Component value
The component value refers to the specified value for particular components. For instance, the component value for capacitor is capacitance. Inductance is the component value for inductors. This information will help you to keep the value in mind. Also, it could help in getting alternative parts when sourcing for components.
Part number
You must include the part number of each part in the BOM. Therefore, each part must be assigned a part number. This will help you identify parts easily. Manufacturers may choose a non-intelligent or intelligent part numbering scheme.
BOM level
It is crucial to assign every assembly or part a number to know where it fits in. This provides an understanding of the BOM structure.
Quantity
This information is very delicate and as such must be in the BOM. The quantity column indicates the number of a particular component the manufacturer needs to order.
Placement method
This placement method specifies how your manufacturer should assemble your part on the board. Also, the placement method can be surface-mount, through-hole, and combination of SMD and through-hole.
Reference designators
You will have to include reference designator if you have a product that comprises printed circuit board assemblies. Also, this information can prevent confusion during the production process. Reference designators are usually labels printed in silkscreen on the printed circuit board.
Part link
The part link is just a web link that reveals more details about the part. Also, it reveals more information to you and your manufacturer.
Other information included in a BOM
Package type
This refers to the type of body that houses electronic components. Also, the package provides an idea of the shape and size of the part. Also, package can help you lay out the PCB.
Procurement type
This reveals how every part of the PCB is made or purchased. Procurement type helps to create efficiencies in procurement and manufacturing.
Alternate part number
Part stock changes over time. A part which may be in stock when you created your BOM may be unavailable by the time you begin procurement. This is when an alternate part number becomes handy. Therefore, an alternate part number offers a substitute part when your original part is unavailable. Also, it saves time spent on looking for an alternative part.
This information reveals the number of connection points every component has on the board. In addition, including the footprint explains the arrangement of connectors like pads in SMT. Points and footprint are crucial for each BOM level and individual components.
BOM levels
BOM is a comprehensive list that contains multiple levels. Each of the BOM levels represents a sub-assembly or main assembly. Every BOM features structure marked according to the BOM levels. Therefore, the BOM level helps users to easily navigate the document and have a good understanding of the assembly.
What you should know Before Creating a Bill of Materials?
Before creating a bill of materials, it is important you understand certain facts. Designing a BOM can be time-consuming. However, you shouldn’t skip any step. Before creating a BOM, you should consider the following questions and have answers to them.
What are you creating?
Before you decide to create a BOM, you should have started with the design phase of your project. Also, this design phase will prepare you ahead of time. It will help you know the parts, components and assemblies you will include in the BOM. Also, ensure your plan works as expected.
How should you manage the BOM?
Your bill of materials will undergo several iterations as you create it. Before you start creating a BOM, ensure you create a system for managing it. Also, ensure you use the latest version. Create identifiers for various versions. Also, you can allow a few people to edit your document. It is crucial you keep records of supporting documents like work instructions and CAD drawings.
Who will use the BOM record?
It is crucial to include several details in your BOM. In most cases, you may never have a face-to-face interaction with some people using your BOM. Therefore, your BOM have all the details they need throughout the lifecycle of the product. You should design your BOM based on the type of people who will be needing your BOM.
What information will your BOM include?
You need to know the information you will be including in your BOM list. Every BOM should comprise basic information like part name. Some items may be optional. Also, you will need to decide if you will be including consumables like fasteners and glues. Most manufacturers second-guess whether to include consumable in their BOM.
How to Write a Bill of Materials
Writing a bill of materials is a straightforward process. However, it is crucial you follow the necessary procedures when writing one. There are softwares that help you write a BOM list without stress.
Create the document
Open the software you intend to use. After this, create a new document. Name the document and include important information at the top.
Organize the document
Create user permissions and create any levels needed. Also, you might have to include more organizational data and make changes to the data as you progress.
Fill in the columns
Here, you will have to put the names of the categories at the columns’ top. Therefore, these titles will comprise things like part number, item name, and quantity.
Fill the rows
You will need to add information to the rows based on the category of the column. Also, each component on your printed circuit board will feature a separate row. It is crucial to ensure the information is up-to-date. This will determine the success of your project.
Update information
You will need to update the details in your BOM when needed. Always remember to save all the changes you have made to the file. As you know more about the project, you will need to be more flexible in the production process.
Tips in Creating BOM
Design your BOM based on your needs
Before creating a BOM, it is crucial to determine what you will need from it. Companies have various ways of creating BOMs. Also, the organization and information included in your BOM depends on the type of project. Therefore, you will need to customize your BOM based on the demands of your project.
Make use of a template
PCB assembler and PCB manufacturers always have BOM templates. You can get these templates on their websites or their sales departments. A template gives you an idea of what your BOM should look like. Also, it is ideal to get your template from the company you are working with. This will help to prevent problems that may arise when opening the BOM. Also, it will prevent any technical issues resulting from incompatible file types.
Ensure you include important and clear details
A bill of materials explains your PCB assembly to your manufacturer. Also, it indicates the quantity of components you will be including in your PCB assembly. Therefore, you must ensure your BOM is clear and well-detailed. Avoid adding information that will cause confusion.
Cross-check all details
Ensure you thoroughly check your BOM before you send it to your PCB manufacturer. Also, ensure all the necessary information included in the BOM is accurate. The accuracy of your BOM will determine the success of your project. Any little mistake could cost you.
Reduce editing capabilities
A lot of people will want to access your BOM. Therefore, ensure you don’t give editing permission to anyone. Only do it when it is necessary. You should rather provide a read-only access to the BOM document. Also, restricting editing capabilities can avoid misinformed and accidental changes.
Benefits of Creating a Bill of Materials
BOM is a detailed description of parts and components required for manufacturing. Also, it helps to create realistic project timelines. It is crucial in PCB assembly and PCB design.
Cost management
You will get a better price for every item when you order large quantities. Also, Bill of materials minimizes logistics to a significant level. A BOM helps you to plan the purchases of materials and estimate costs. Also, this document helps to regulate inventory and reduce production delays.
Reduces data management
The bill of materials helps to coordinate budgeting and planning of your PCB designs. Ensure you generate your BOM from the PCB design. This will help to ensure your BOM remains up to date. Anytime, you add a new component, fill in the BOM and update your library.
Streamlines electronic design automation
Planning ahead minimizes the process involved in managing all parts. Also, it enables you to whip up a new prototype form library of parts.
Identify the cause of failure
With a BOM, you can identify the cause of failure in a PCB project. Therefore, the PCB manufacturer can replace the faulty parts and components on time. The information in BOMs makes it easy to track product failures. BOM detects even relatively small mistakes.
Ensures uniformity
BOM helps to ensure uniformity in the production line. This happens when every production run go through the same BOM. Therefore, these products remain consistent. Also, BOM offers efficient manufacturing processes.
A BOM offers great benefits when used in manufacturing processes. It is beneficial to both the manufacturer and customer. It ensures that both parties remain on the same page. Also, contract manufacturers can be on the same page with their customers.
Types of BOM structure
The bill of materials has two different types of structure.
Single-level BOM
This type of BOM structure displays each part of the product once. Also, this BOM displays the part alongside the quantity required. It looks like a shopping list. Single-level BOMs are quite easy to design. However, they don’t reveal the relationships between components, subassemblies, and assemblies used to manufacture a product. Therefore, it is not an ideal option complex product.
Also, if a product malfunctions, it will be difficult to determine the component that needs replacement or repair. For example, if you create a BOM for a vehicle in a single-format and the door handle becomes faulty. This BOM structure won’t differentiate between the parts in the handle and the parts used in the other vehicle.
Multi-level BOM
A multi-level bill of materials reveals the relationship between assemblies, components, and sub-assemblies. Also, this type of BOM identifying the materials that the higher-level assembly will comprise. Therefore, multi-level BOMs are the indented BOMs.
Furthermore, multilevel BOMs take more time to create. However, it provides greater details. Also, it distinguishes between the child and parent parts in a product. As a result of this, this type of BOM is commonly known as indented BOMs. Multi-level BOMs are widely used for complex products.
Types of BOM
While single and multi-level BOMs are ideal for use at different stages of product development, there are other types of BOM. These BOM types include:
Manufacturing BOM
This type of BOM is commonly used during the production phase, Also, it identifies the assemblies and parts required for producing a product. It includes packaging and accounts for items consumed during the production process. Also, a manufacturing BOM features the information of all the required parts used to build a product shipped to customers.
Anything in used in the final packaged product will be in the manufacturing BOM. The creation of a manufacturing BOM for a new product can take several weeks. If the product needs some changes, you can update the manufacturing BOM.
Engineering BOM
Manufacturers create an engineering BOM while a product is still going through the design phase. Also, this BOM defines the original design f a finished product. An engineering BOM features parts, subassemblies, and components designated by engineering. A completed product could have more than one engineering BOM.
An accurate engineering BOM is crucial, particularly for a new product. This is because this BOM ensures correct parts and materials are available in the accurate quantities. Any error in this BOM can have great implications. Inaccurate quantities can put the production phase to a halt.
Configurable BOM
A configurable BOM is commonly used for finished products configured to meet a customer’s requirements. Therefore, it identifies materials and parts needed to manufacture a product to meet the requirements of a customer.
Sales BOM
A sale BOM comprises the components and materials required to manufacture a product based on a customer’s order. You can generate this BOM from the sales order. Also, this BOM is ideal for an off-the-shelf product.
Conclusion
A bill of materials is essential in electronics and PCB manufacturing. It makes the product development process easier. You can avoid creating multiple errors when you use a BOM. For other relevant notes, BOMs are widely used throughout the PCB manufacturing process.
Furthermore, it is crucial to provide accurate information in your BOM list. This document must feature the right amount of raw materials, parts, and components needed for the manufacturing of a product.
