The Last Mile of Electronics BOMs

The Last Mile of Electronics BOMs

The last mile in electronics is the most difficult. Especially when it comes to building out your Bill Of Materials (BOM).

It goes like this. You come up with an idea for a circuit. You search on for potential solutions using the information you have on hand. Maybe you’re looking to build a switching converter for converting a 12V source to 5V for an audio circuit you’re building. Your research lead you to some silicon you think might be solutions.  Since you’re going to put it into production, you have to pay careful attention to the various components’ Risk Rank. Next you read through datasheets, you digest some app notes and start to prototype with two different chips. You design small boards for each, order the parts from the wide range of distributors we have on and then use the rest of the parts in your lab to populate the passives on board.  Testing goes well and based on the results, you select one of the two chips and design that into a larger product PCB.  Your circuit is integrated into a finished product.  Awesome!

But wait, there’s more.

You see the part that’s in italics above? That’s for a reason. Many engineers have a store room of components for building up prototypes, from large engineering firms with stacks of components laying around to hobbyists in their garages with parts bins and “I’ll See If I Have It In The Junk Pile” collections.  Having a set of E12 resistors and a bunch of bulk capacitor values is  a really great resource for rapidly changing out values and prototyping a range of new functions with a circuit. But when it comes time to finalize the BOM, you no longer get to just assume, “I’ll use what I have”. Contract Manufacturers (CMs) need to know exact part numbers. When you are building 1000 units of a product, you’ll need to buy 1000 of that 4.7K, 0.01% resistor you grabbed off the shelf and designed into the circuit.  That means that you need to fill out the rest of your BOM and be very explicit with which parts you want them to use.

Some of you are probably saying that your CM takes care of this for you, and in some cases that’s very true. When you’ve got a good production partner, it’s best to send your BOM to a CM with line items that say something like “CAP 0603 100pF X7R” and then allow them to source whichever parts best suit their needs. In the best case scenario, they can sub in parts they already stock (and have preloaded on pick-and-place cassettes), reducing cost to you. This isn’t always the case though, especially if you are working through a new manufacturer you don’t yet know well or trust. There are a range of situations where it will be up to you to source the actual part numbers.

Now imagine the old workflow for filling out the passives on your BOM.  Line Item One: 10uF capacitor.

  1. You go to the site where you normally buy parts and type in “Capacitor”.
  2. You select your filters.
  3. You verify specs.
  4. You narrow down to a select group of parts.
  5. You sort by price.
  6. You see where there is availability.
  7. You cross your fingers and add the Manufacturer Part Number (MPN) to the BOM. Line item one is complete!

Now repeat this process for every passive you have on board.

On some BOMs, this can be upwards of 70% of the total number of parts listed, depending on complexity. If you work on a device that has 100 line items, that means you could be doing this 70 times or more. And you thought engineering would be exciting.

With the old workflow, the best you could hope for when you searched for “Capacitor 1pF” is a luck of the draw. Searches are often done on the “description” field of the various component listings. You get a result that is “1 pF”, but it’s mixed in with all the  “11 pF”, “21 pF”, “51 pF” and so on. Other times you’ll just get all the generic results for “Capacitor”.

We have improved this process: we call it the “infer service”. If you’re searching for something like “Capacitor 0603 0.1uF“, we recognize the thing you’re looking for, “capacitor” and we pull out the relevant parametric values! We even recognize that “0.1uF” can also be understood as “100nF” as it is listed in our system. This is done by looking at the entire search phrase and then processing it to recognize potential parametric options.

Infer Capacitor Search


This isn’t just important for passives. This radically alters how you do your searches for components in the first place. Our goal is to allow you to enter as much preliminary specification in the search bar as you want, and we derive the best set of possible components. All this before beginning the parameter dance of selecting specs from a list. The infer service moves us closer to that goal.

For now, rejoice in a simpler last mile. If you need to fill in your BOM or even if you just need to find components with specific parameters a little easier, the infer service will help you get your work done. We love hearing about success stories. Please send us a message on Twitter, our (brand new!) Facebook page or on our Community forum. And of course we always welcome comments on the blog below.

Happy searching!



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