For bakers to manufacture a cake there is a need for them to purchase some important ingredients, like sugar, butter, and flour. Also, they need to have access to important tools, such as bowls, pans, mixers, etc. As this baker visits the store to purchase the necessary ingredients and tools missing, they go with a list. This list helps them remember what to purchase as well as the amount of each they should purchase.
Now, imagine the customer, instead of the baker decides to make the list. This could be worse in cases where this baker hardly saw the customer face-to-face to discuss things. Therefore, the way through which the customer revealed what was required was via the shopping list. Also, this list includes some information regarding ways of using each ingredient. The list is very similar to the BOM or bill of materials. The difference here is that rather than bake a cake, you will be making a hardware like the printed circuit board (PCB).
What Is a BOM?
Here we will be discussing what bill of materials is? The BOM is regarded as a comprehensive list of sub-assemblies and assemblies, raw materials, all the components as well as other important items for the product manufacturing. Furthermore, manufacturers have to depend on whatever information is included in the manufacturing BOM to help in building a specific product, therefore there is a need for high accuracy and it must be well detailed. In addition, customers make use of BOMs in explaining to the PCB or printed circuit board assembler his exact needs anytime they place an order for circuit boards. Also, this assembler makes use of it in building the circuit board to work in line with the specifications of the customer.
Things to Know Before You Create a Bill of Materials
The creation of detailed BOM could take time; therefore skipping this step could be tempting. However, the development of any of the records can ensure a more efficient PCB production process or product development process. Also it helps prevent costly mistakes, most especially for more complex designs.
Before you create your BOM, there is a need to provide answers to these questions.
What do you plan to build?
Before starting with the BOM step, there is a need to have started your project’s pcb design phase. If you fail to do this, you may fail to understand the preparation of the BOM. In addition, you may begin to compile the correct information regarding the parts needed as you are designing.
However, you cannot begin with creating the BOM quickly till the pcb design is ready. Also, make sure that your plan works fine as expected and a Gerber file has been produced. This Gerber file helps in explaining the PCB’s design information to the PCB manufacturer. Also, this step helps in determining the parts you need to add to your BOM.
How will I manage my BOM?
While creating the BOM, it may experience multiple iterations, and many people could handle it. Now, before starting, ensure that you establish a system that can manage it. Also, ensure that people are using the latest version. Furthermore, track the changes and also create identifiers to be used in different versions. Also, only allow a few people to edit your document. In addition, decide ahead who you will assign each task to, to avoid confusion.
Who can use it?
Due to the information the document includes, it may be used in multiple departments, like purchasing, engineering, design, and manufacturing, during the process of PCB production line. Therefore, creating this idea of people that needs the BOM helps you include accurate information.
What information should you include?
There is no need to understand and know the specifics at this stage. However, there is a need to understand those categories you would love to include in the document. Furthermore, all BOMs ought to have some basics, like quantity and part name and quantity. However, the other items are usually optional. Also, decide if you will add consumables like bolts and glues. Any preference for a specific supplier you purchase your parts from? However, take note that the most appropriate practice is making a very detailed and complete BOM.
How can you organize your BOM?
Before you start, it is important to decide the basic organization strategies. Also, take note of the number of sub assemblies (this refers to items that you’ll assembly in a separate way — items you will assemble separately to attach them onto your main assembly), levels, and files you’ll have, way of grouping the items, as well as other designations that you want to have. When the format of the BOM is created ahead, you will plug in data more efficiently immediately you begin writing the BOM.
What specific program will you use in creating it?
Before making the bill of materials, there is a need to know the software you’ll be using in order to create it. Essentially, a BOM list is like a spreadsheet, and majority of companies make use of Excel. Furthermore, as the business grows and the projects become more complicated, you’ll discover that you need a better program which is designed expressly for BOMs, from which there are so many.
How Can You Write your Bill of Materials?
Immediately all the necessary information has been sorted, then you can go ahead with writing the BOM list. This BOM list process is somehow straightforward; however, it could be challenging to find the information.
Create your document
First, open whatever program you want to use and then create the new spreadsheet document. Then give the file a name and then place the name on the project as well as other necessary information on top.
Organize your document
You can achieve this by establishing user permissions, setting up the change tracking as well as crating the necessary levels. Also, you may need to include more of this information as well as make some changes as you go.
Filling the columns
Next is populating the categories’ names at the top part of the columns. The titles must have things like the item quantity, name, part number, etc. We’ll give more detail in the following section.
Filling in of the rows
Here, you will use information to populate the rows. This must be done in line with the column’s category. Every board must feature a separate row. Also, you must make sure that the information is up to date and accurate as they are very important to your project’s success.
Update as required
Update the BOM information as necessary. Also, as you are creating your file, ensure that you save it very often and make sure that you keep one record of the changes. In addition, as you discover more information regarding your circumstances and project, you will most likely see the need to be very flexible through the production process of your PCB.
What Should You Include in a BOM?
All the information present in the BOM for the PCB assembly could differ with respect to the project. Here is some group of information commonly seen in them.
The description is useful in listing the details regarding every part of the BOM, like dimensions, color, voltage, as well as other specifications. The details help in ensuring the most appropriate part to get ordered as well as avoid confusion due to similar elements.
Furthermore, ensure you list all the correct measuring units. For those items having multiple units, your choice has to be consistent all through the document
Name of Manufacturer
It is very important that you include the component manufacturer’s name. This will help those making use of the BOM in order to discover the best and right part. Also, it is very necessary to verify every piece available from your manufacturer before you go ahead to list it.
Also, make sure that it suits your project appropriately with respect to the delivery time, cost and specifications. When you check the information very early, this will assist in avoiding extra coast and time of getting a replacement part much later in your production process.
Another important information is the number of every part needed. Ensure that the information is up to date. This will help you take better advantage of the discounts for buying bulk items.
When you include your procurement type on the BOM spreadsheet, it helps you to make sure that you get the right part. The designation explains the way in which a particular component is made or bought. i.e. is the product custom-made or purchased off-the-shelf?
Indicating the flexibility required in the BOM could ensure a smoother production process. This is helpful in categorizing the items by the manner in which you are flexible with them. You can mark some of the parts critical; this means that the assembler has to work with the right specifications.
The other parts may play a significant role in your design, but you may be able to swap it for some equivalent parts of another brand. The manufacturer has to follow other specifications. At Rayming PCB, we don’t make any substitution or change without consulting the customer.
It is advisable to add alternate parts if your requested component is unavailable or there’s another change coming up. By so doing, it will reduce the time you have lost in all these situations.
The BOMs usually have multiple levels. Each of these BOMs represents the sub-assembly or the main assembly. Every BOM has a unique structure or product structure tree, which is marked and divided based on the BOM levels in order to assist users in navigating the document as well as understanding the assembly.
While you are designing the board, you will be creating files like CAD files, diagrams, data sheets, as well as instructions, which doesn’t fit in a BOM spreadsheet. For these types of instances, you will wish to attach the supporting documents as well as associate and link them with the right components and BOM level.
In creating the unique reference designator for all the parts of the PCB assembly indicating where these pieces goes onto your board. When you make the designator similar to the level used in the documents of your PCB design, this assists in the cross-reference of your PCB layout and BOM easily. The identifiers are usually made up of a number and a letter.
The materials document, the package’s description, etc should be included. The design of these packages serve in streamlining the production, as well as choosing the most appropriate package type could ensure that the process becomes more cost-effective and efficient.
There is a need for you to list the surface mount technology and placement method that your PCB project will make use of. This helps in describing the way all the components attaches onto the circuit board. The methods are surface mount technology and through-hole.
Here, you will notate the connection points that every component has on the circuit board. Furthermore, make sure that the footprint of every part is included. This throws more light on the connectors’ arrangement, like pads in the SMT or through-holes, which attaches them both physically onto the circuit board and then connects them electrically. In addition, make sure that you take note of the footprint and points for the individual components as well as BOM level.
Also, you may need to add some space to your sheet so as to mark areas where the parts of the lifecycles are. Furthermore, the designations of this category are design, testing, and production. These helps to easily track progress of your assembly, as well as create realistic project timelines.
Notes and Comments
Though, this category isn’t critical, it could increase your project’s efficiency drastically, most especially whenever unexpected changes or problems arise. Here is the place where you place any notes and comments which doesn’t fit in other categories.
What are the Tips for BOM Creation?
Tailor the BOM in order to meet your needs:
Before creating your BOM, take a decision regarding what both you and the companies you are partnering with requires from it and then make the design to suit those needs. BOMs are handled by different companies in different ways. So also, different projects neede different information, organization, as well as other features. Also, customize the BOM in line with your project’s unique demands.
Make use of a template
Every PCB assembler and manufacturer possesses BOM templates that you can get from their websites and departments before requesting a quotation. Make use of the company-given template helps in avoiding issues related to the opening and accessing of the BOM document as well as technical issues that are caused as a result of files that are incompatible.
Add the right details
Add enough helpful information as possible in the document. Remember that the BOM plays a very important role in throwing more light to people that have to build your PCB from the scratch. The people might not have talked to you before, and they may not speak exactly this same language. This is why your BOM needs to be clear, precise and detailed. Some information are not helpful and this will only cause confusion. However, make use of your best judgment.
Double-check your information
Check all information meticulously before your upload or send your bill of material to the manufacturer. Ensure that the information is accurate and you can also navigate the document the intended way. When we talk of PCB assembly, even very small mistakes could prove costly.
Track your changes
Make sure that there is a system that can help in keeping track of the changes to your document. At times, you want to have a record of the previous versions. This is in case you wish to refer to them. Ensure that every version is well labeled and that the one that is most updated is used for your project.
Limit the Editing Capabilities
Though so many people may need to gain access to the BOM, avoid giving them the editing permission unless it is necessary. Rather, the access you should give them is the “read-only access”. When you restrict the editing ability, it prevents misinformed and accidental changes. Furthermore, you may create a unique identifier for those having editing capabilities.