Tips for Working with PCB Assembly Houses
So, you’ve prototyped your circuit, you’ve designed your board, and you want to bring it to market. What’s next? Well, aside from choosing a high quality manufacturer to fabricate your PCB, you’ll also need to select a vendor to professionally assemble the required components to the board. While choosing the right assembly house may seem daunting, we’ll share a few tips to make sure your next project goes smoothly.
Communicate! Early and Often
You’re the engineer. You’re the designer. You’ve put your blood, sweat, and effort into every detail. Why would you leave someone else to assume what you want? Open a line of communication with an account or program manager to make sure your project is built exactly how you’d like it. Plus, the assembler probably has resources you haven’t thought about. Since these talented engineers and designers are experienced working with assembly projects like yours, they can provide invaluable feedback on your project such as:
- Advice on effective board design.
- Suggesting alternative components (to solve availability issues) or manufacturing methods.
- Informing on current trends across the industry to keep your product on the cutting edge.
To Offshore or Not Offshore? Consider the Big Picture!
While it is easy to be enamored by the low prices of international manufacturing there are some major considerations to keep in mind that may result in higher total costs in the long term.
- Substandard or imitation parts. A manufacturer may be tempted to cut corners and costs by using parts that are not up to the standard you specified, or, American industry standards. Or your manufacturer may unwittingly receive counterfeit parts despite their best efforts to purchase from reliable sources. Poor work could lead to board malfunctions or failures later, making your “cheaper” boards costly to replace.
- International suppliers are often overbooked and deal with hundreds of projects all at once. This can lead to endless delays when a different project has higher priority or goes wrong.
- Delivery from Asian manufacturers often takes three to five business days when considering freight and customs. This makes it difficult to reliably order last minute rush units when inventory is low.
We’ve all been there: there’s one part that would be perfect for your product. There’s just one problem: you can only get it from one source that is constantly out of stock. Unfortunately, components such as these make it difficult to properly source your project and can potentially set your timeline back for months. For this reason, you should avoid these components at all cost and build in widely available parts that are available from several sources with large, stable stock quantities or reasonable substitutes.
In the prototyping phase it is easy to overlook silkscreen markings. You have the board layout open in your EDA tool and you’re likely hand soldering. On the flip side, your assembly house relies on these small letters and numbers to identify which part goes where. If a polarity or pin 1 marking is missing the assembler will have to hold the job to clarify component orientations with you. Incorrect markings can often lead to the wrong part being placed, consequently destroying entire production runs.
Complete and Understandable Bill of Materials (BOM)
A clear, concise bill of materials is equally as important as silkscreen markings. Your assembly house will be using this crucial document to purchase all the components necessary to build your project and will match the reference designators to the silkscreen. It is important to ensure your BOM is a spreadsheet listing each “line item”, the reference designators related to that line, and a brief description. Assembly houses also prefer BOMs with at least one supplier link to each part.
Consider Lead Time
By now, you are probably deeply aware of the time necessary to develop and test your prototype. However, when transitioning your project into production your build time may balloon exponentially. Some parts may not be easy to source in the necessary quantity, boards may be difficult to build, initial setup may take time. To be sure your product makes it to market quickly, be sure to ask your assembly house for guidance on how to reduce lead times. It may be as simple as allowing component substitutes or paying a small expedite fee.
Proper File Formats
Make sure the manufacturer you choose is experienced in working with the file formats you submit.
- Board Files: Most large suppliers are used to working with the industry-standard file format RS-274X (commonly known as “Gerber”), although most now also accept ODB++ files. In addition, if there are surface mount components, then the assembly house will need “XY data” (also called “pick and place data”). The XY data is a list of the centroids of each component so that the assembler can program their pick and place machine.
- BOM Files: Most in the industry have standardized around either MS Excel (.xlsl), CSV, or PDF. While most suppliers are capable of reading any of these formats it is important for your BOM to be formatted as a spreadsheet with proper line formatting.
It’s both exciting and stressful to finally see your project exit the design phase and head into production. While not an exhaustive list, these are just a few of the tips we’ve learned over the years from working with assembly houses across the industry, and we hope that it helps make your transition a little easier. To learn more check out 10 Tips to Ensure PCB Assembly Success.
As always, we at Bay Area Circuits stand ready to assist you in all stages of the process.