With how interconnected the world is, I’m still in awe of all the people knowing and learning multiple languages. Luckily as an engineer, we all are able to speak a common language when it comes to any engineering subject: numbers. No matter where you live zero is zero, pi is pi, and 2+2 will always equal, hold on let me grab my calculator, 4.
In our current design and manufacturing ecosystem, we are often tasked with working with manufacturers, part suppliers, engineers, and a plethora of other folks outside of our in-house design team. Of all these various moving parts involved with creating the end product, you’re lucky if you only have three different languages to be aware of by the time you look at the bill of materials (BOM).
A word that will be one of your best friends as a PCB designer, though, is prototyping. Prototyping is thought to be a quick and dirty way to get your design mocked up via schematics, drawings, and BOMs; however, the speed of your prototyping process can sometimes be anything other than ‘rapid’. The disconnect between your prototyping manufacturer and your design can cause speed bumps in this process. But how can a smart BOM help this?
Before Your BOM, How do You Start With Rapid Prototype Manufacturing?
So you’ve gotten to the stage in your design where you are just about ready to unveil your design to some investors at a local event, but you’ll need a few prototypes quickly manufactured in order to give them something to hold and feel. You find a manufacturer overseas who has done some great work in the past and you decide to give them a shot. Let’s now make our way through some tips in order for you to avoid some common pitfalls and present them with a fully optimized and ready to rapidly produce BOM.
Be Thorough, Very Thorough
Growing up, my folks constantly preached over-communication. This, of course, was a late night conversation when I was staying out far past curfew without a whisper of where I was, but the same can be conveyed in all aspects of your BOM. It’s far better for you to be overly descriptive in your efforts to describe your design. Sending revisions of your BOM back to your manufacturing takes the rapid out of your rapid prototyping very, well, rapidly.
Your BOM should over-communicate your design and leave no questions for the manufacturer to ask ensuring a higher quality first pass check. Don’t leave it up to the manufacturer’s creativity to assume anything in your BOM, especially if there exists a language barrier between you.
- Did you list the max voltage on your capacitors?
- What about the % tolerance on your resistors?
- And packaging parts, even the stickers?
With these in mind, your manufacturer can have a very clear and concise understanding of what your design entails. Now comes the question of design variability.
Ensuring your document is thorough can increase first pass quality in your rapid prototyping stage.
Many parts of your BOM don’t have to be the exact part numbers listed, rather, they just need to perform within a range of specs. In these cases, you’ll have a part in mind but if the manufacturer doesn’t have the specified part a substitute will do. This variability in your BOM should be labeled as such. Even the use of a simple color-coded legend will do.
Red labels could mean the part is critical to the design, no substitutes allowed. Yellow might mean P/N changes allowed but to be approved prior to implementation. Green could mean P/N changes allowed without approval as long as specifications met. Now, this is not an industry recognized method of variability, but implementing a simple system into your BOM could save you an arm and a leg when sourcing parts that may (or may not) be suited for your design.
If you have been following along well, then you have over-communicated and color-labeled each part and specification on your BOM. But what if you have a few changes that you plan to implement before you send it to the manufacturer? Should you be tracking these changes? Here’s a spoiler for you: of course you should.
Color coding your BOM is a great way to convey variability.
Tracking Changes in Your BOM
It’s very rare that you are the only one referring back to your design, and even more your BOM. Being the most relevant document to your manufacturer, you BOM is your playbook of your design, telling all the players involved (engineers, sourcing agents, manufacturers) what parts go where and why.
Folks who will be touching your BOM more than a time or two are bound to have to have to deal with a handful of changes that are inevitably going to happen, and if there is no rhyme or reason to why changes were made, your team may be left scratching their heads and some explanations will be expected later on.
Instead of leaving folks wondering why changes were made, let them know as they happen via change logs, version documents, and revision histories. Anything in your BOM that is revised should be listed within the spreadsheet itself so each team member is able to follow the breadcrumbs of your changes. It is a small act which will go a long way to encouraging efficiency in your rapid prototyping.
The first lesson to keep in mind is that communication, and over-communication, are pivotal in keeping any of your design processes stable and on-track through any product variations. The barriers that exist between overseas and in-house manufacturers do not have to be inhibitive if you remove the chances of misunderstanding. And the easiest place to begin is in your smart PCB design software, like Altium Designer with its ActiveBOM tool to keep your lists organized.
If you would like to further discuss methods that will increase first pass quality when optimizing your BOM for rapid prototyping, talk to an Altium expert today.
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