Planning the PCB Assembly for Your New Product Introduction Project

In order to make the assembly process for your project as smooth as possible, it is best to have a plan in place from the very beginning to the end of your project. With a thorough plan in place, the most common assembly delays can be readily avoided. For example; missing information, stock issues, and incorrect information being provided.

The files that are provided during the quotation stage are very important tools in communicating the requirements and specifications of your project to Bittele. The required files can be organized into four categories:

BOM
Centroid
Gerber Files
Additional Documentation

BOM:

The BOM is a required file for Bittele’s assembly process because of the valuable information it provides. The BOM should include each electrical component that needs to be assembled in your project. Each unique component will have its own row in the BOM with the following information: Quantity, Product Number, Reference Designator, Description, and Item Number. For an example please see the sample BOM. During the quotation stage, the BOM is used to determine the cost of the components and any potential stock issues. At the quotation stage the BOM is also analyzed for discrepancy issues between the quantity and the number of reference designators given, and the given item description and the item description that is available online. Once the order is released to Bittele’s production team the BOM is used to cross-reference the components with the Datasheets of the components, Centroid information and the Gerbers of the board. At this stage any orientation, footprint, clearance, and other assembly issues are checked and investigated.

Centroid:

The Centroid, XY, or Pick and Place file is simply used as a map for our automated assembly machines to place your components in the correct location and in the correct orientation. Bitteles production team scrutinizes the Centroid and the Gerber files to ascertain that the information provided holds no discrepancies.

Gerbers:

Besides providing the fabrication information of the PCB’s of your project the Gerbers also contain information on the assembly location of your components. This can be seen with SMT Pads on the paste layers, drill locations for TH components, and the silkscreen.

Additional Documentation:

Occasionally your project will have special assembly requirements such as a TH component that needs its leads trimmed to a certain length, or a component that is heat sensitive and thus must be assembled by hand. In such cases, it is best to provide a document with instructions detailing how these special cases must be handled.

As your project develops from its design stages to prototype and then its production stages these four documents must be maintained accurately so that there are as few issues in your project as possible. Developing a BOM early in the development stage of your project can help outline potential stock issues before they cause delays that can only be solved through alternative components that may require the modification of Gerbers. Information from your Centroid and Gerbers can be used to discover discrepancy issues before Bittele reviews your files at which point an issue can cause you to modify your Gerber files which may cause delays. Having the documentation for your special requirements upfront will avoid the delays that will be caused by having to write such documentation in the middle of the production process. Having these documents ready in the early stages of your project can also be very helpful because of how they can be used to provide accurate project estimations without finalizing the project.

Here are a few things to consider as you plan the assembly portion of your project:

SMT Component packages: Certain packages, such as QFN’s, BGA’s and 0201’s have additional assembly and inspection costs associated with them.

Single-Sided vs Double-Sided SMT Assembly: Double-sided assembly costs more than Single-sided assembly.

Stock Issues: As mentioned above it is good practice to plan for alternatives in case key components go out of stock or to stock up on them when they are available ahead of time.

Special requirements: As mentioned above it is a good idea to keep track of all the special requirements your project may need so that it is possible to get an accurate quote for both the cost and the turn time of your project.