BOM is a detailed document that the designer must provide to the manufacturer with information on the materials and components utilized for a specific PCB design.
Let’s understand this by imagining that you need a dress. You go to the designer and tell him you need golden buttons from ABC brand, laces in LMN’s design and color, threads in XYZ brand in certain colors, and fabric (size, color, and manufacturer).For all the choices you made for the essentials of your design if you have their links you share those links in order to be more specific and accurate. You can ultimately help a tailor or designer to create the dress of your dreams by using the design and its measurements together you provided with the choice of all the accessories and fabric.
Similar to this, when you give a manufacturer gerber files for a PCB design, you also give them a BOM file, or bill of materials file. Manufacturers can purchase and assemble components with the necessary orientations on pcb taking into account BOM files.
What is BOM?
A detailed description of every part and material needed to create and assemble a printed circuit board is contained in the bill of materials, or BOM, for the PCB. It plays an important role in PCB fabrication, procurement, and assembly. Based on this specified BOM, the manufacturer and assembler can create the required PCB, therefore it must be detail-oriented while yet extremely precise.
Who creates and manages a BOM?
The Art of Managing BOM: A Story of Collaboration and Innovation
Depending on the organizational culture, different organizations adhere to different hierarchies. Usually, a team of professionals involved in the product development process creates a Bill of Materials (BOM) for a Printed Circuit Board (PCB). Multiple stakeholders, including the following, must provide input for the design of a PCB BOM:
- Project managers oversee the full process of developing a product, including the BOM. They are responsible for delivering quality project on time, so quality, quantity and procurement of the components is very important for them.
- Electrical engineers design the circuit and select the required components in order to achieve the function that they want. In determining the ratings, values, types, tolerances, and quantities of components that should be used on the PCB, they are the vital part of BOM making.
- PCB designers are responsible for the layout of the PCB, including component placement, electrical routing, and taking into consideration of the board’s mechanical specs. They depend on the provided BOM to make sure that the selected components are mechanically fit set to the size of pcb and required system.
- Component engineers are in the role of identifying components that match to the required requirements for availability, cost, and reliability. They could give recommendations for component replacement and selection.
- Mechanical engineers could be involved in the design process if the PCB is a part of a larger mechanical assembly. They need BOM to understand the mechanical requirements and space constraints of the PCB.
- As a project develops, maintaining the BOM is typically the job of documentation specialists. Throughout the course of the product’s lifetime, they make sure the BOM is correct and up to date. After the BOM is created and completed by every aspect, the design department’s project manager will forward it to the manufacturing and purchasing department for further process.
- The procurement team is in responsible for identifying and procuring the parts listed in the BOM. In order to determine the specific part numbers, quantities, and vendors for each component, they rely on the BOM.
- Manufacturing engineers use the BOM to lay out the assembly process, which includes component placement, soldering procedures, and quality control methods. A flawless and free of mistakes assembly process is made possible by accurate BOM.
- Quality control department can look over the BOM to confirm that the correct parts were used throughout the PCB assembly process in the right amount. It can be referred to as a quality check list during the quality assurance process.
So, we can say that the development of a PCB BOM is a combine effort of various departments mentioned above. As per hierarchy of the organization the process may differ but these all are the stake holders of BOM. To create an accurate and useful BOM that supports the successful design, manufacture, and assembly of the PCB, good communication and cooperation between various stakeholders are important.
How to Create a Comprehensive BOM?
The following essential information for each component should be included in a thorough bill of materials (BOM) for a printed circuit board (PCB), although they may vary from project to project based on the specifications for PCB and PCBA assembly. Here are a few categories that should be in the BOM; you can add or remove them according to what you require.
Reference Designator: There must be unique identity across each component on Pcb or example U1, U2, U3 for ICs similarly R1, R2, R3 for resistors and C1, C2, C3 for resistors. Lable them same as you label in Pcb file and mention other categories along them.
Part Number: The component’s part number from the manufacturer. This knowledge is essential for locating and choosing the right component.
Manufacturer: the company that creates the component. This makes it easier to get parts from trustworthy vendors.
Value: The component’s electrical value or rating. For instance, the voltage and current ratings for other components, the capacitance value for a capacitor, or the resistance value for a resistor.
Package Type: The component’s actual packaging or footprint. Specifying this helps to ensure proper component placement and assembly because different components come in different package types.
Description: A brief overview of the component, which may also give further details about its features, functions, standards, tolerance ratings, operating voltages etc.
Quantity: The total number of parts needed to assemble a PCB. In order to prevent shortages or overages during production, make sure that this quantity is precise. It is very necessary to make it accurate for series production and cost estimation.
Component Location: This is very helpful for PCBs with many layers that are complex. It details the precise coordinates or location where each component should be placed.
Layer: Mention the layer on which particular layer, whether top or bottom it should be placed.
Placement method: A likewise specify the surface mount technology or placement method that will be used to attach each component to the board. Through-hole and surface mount technology (SMT) are among of these techniques.
Datasheet Links: Links to the technical documentation or datasheets for each component. By doing this, it is made sure that everyone involved with the BOM has access to precise specs.
Supporting files: You’ll generate files as you design your board, including CAD files, data sheets, schematics, and instructions that don’t fit within the BOM spreadsheet. When needed, you should attach these additional files and link them to the relevant BOM level and components.
Notes: Any additional details or special instructions pertaining to the component, such as suggested soldering methods, sources of alternative materials, and recommended soldering techniques.
Alternative part numbers: If any component is unique and its availability is less, then provide the alternative part number with same footprint otherwise pcb designer has to change foot pattern on pcb board.
Distributor: The distributor or manufacturer who are providing components to procure. For quality products it is very important to mention distributor.
List of manufacturers: A list of authorized suppliers or manufacturers for each component is provided under Approved Manufacturers. This might aid in guaranteeing dependability and consistency.
Cost: Including the price of each component is optional, however doing so could help in cost analysis and planning.
Availability: The component’s lifetime state is listed, showing whether it is active or it is approaching the end of its intended lifespan, or it is obsolete. This is critical for the product’s long-term planning and maintenance.
Lead time: Lead time is listed in the BOM in order to check how much time component will take to be there for planning production and keeping the track of inventory.
Revision History: This is very important to mention the revision history, when and how BOM modified along with dates and summary of modifications.
A complete and precise BOM must be done for optimal and quick PCB assembly, procuring, and maintaining. A successful and reliable end product is created by making sure that the right components are used, procured, and assembled on the PCB during production.
Additionally, Rush PCB Limited is offering model templates that may be filled using the data gathered and documented in detailed BOM together with other Geber files. To get in touch for model BOM template, please feel free to email or contact us.