What do you need to get a quote on a PCB assembly? This is a great question and often a source of confusion. There are four basic documents and exactly how they are transmitted depends on your company’s tools; we can work together to figure out what best fits your circumstance. Here we'll explain what documents are necessary, as well as what information they should all contain, and their role in the quote process.
The basic documents are:
1. Bare Board Print (and gerber files)
2. Assembly Print
3. Bill of Materials
4. Approved Vendor List
Bare-Board Print- Commonly referred to as a fabrication drawing or fab drawing, this print gives us the basic documents required to have your bare PCB fabricated. The bare-board print should include outer dimensions, board thickness, material, finish, number of holes along with the smallest hole size required, the number of layers required, solder-mask color one side or both, silkscreen color one side or both, and any other cost drivers. Lastly, your bare-board print should include both part number and revision. The format is typically pdf.
You will also need to the design files, a common version are gerber files. However you should really endeavor to provide the design files in an intelligent data exchange format like ODB++.
TIP⇒ Always Check Your Data – After any and all revisions to your drawings, ensure that all necessary changes are made to your assembly print and bare-board print, and that revision numbers match on all the documents. Mismatched revision numbers are a leading cause of confusion during quoting and first-time builds.
Assembly Print- Essentially the manufacturer’s blueprint, it shows the location of the parts, as well as any information on special markings or packaging required for the PCB. Like the bare-board print, the assembly print should include the assembly part number and revision. Most commonly provided in a PDF document.
Bill of Materials- (BOM) is the controlling document for components. At a minimum the BOM should have an internal part number, description, quantity per, and ideally a reference designator for each line item. Often BOMs include the approved vendor list (AVL), eliminating the need for a separate AVL. Best-practice BOMs will include the fab part number and revision. BOMs are most commonly provided in Excel format. Please note, you will need to provide separate drawings for any custom parts (i.e. cable assemblies, sheet metal, machining) to obtain pricing for these items.
TIP⇒ Practice Consistency – Make a standard format for your BOM that is easy to navigate and remains constant through every revision. The best file format to use is Excel, and it’s best to have a single line for each part number (called a ‘flat file’).
Approved Vendor List- (AVL) provides the manufacturer and the manufacturer’s part number associated with your internal part number (IPN) or reference. There can be multiple approved manufacturers for each IPN. Commonly this information is included as part of the BOM.
TIP⇒ Keep Records of Previous Revisions - It’s important to keep documentation on all previous versions of your design.