So you wanna get your PCB assembled…

Preparation

Make an ActiveBOM. It’ll make life easier.

Cost Optimization

In general, you pay a little per component, a lot per part number. The pick and place machines have a finite amount of reels, and it costs time to have them replaced, so a high-P/N board will cost much more than a board with similar number of components, but fewer P/Ns. Sometimes this is unavoidable, but there are some tricks to help with this:

• Condense same parts into one P/N. The UTAT library has a lot of virtually identical components with slightly different part numbers, so over the course of a project multiple P/Ns might be selected for the same job.

  • In ActiveBOM, sort by Description and look for (primarily passives) that share similar characteristics.

    

  • Sometimes all parameters will match, sometimes they may differ in tolerance or voltage rating. It rarely hurts to upgrade components (i.e. 50V → 100V), but changing values slightly (i.e. 220nF → 100nF) may affect performance. Use your engineering skills to figure out which changes will have no effect!

  • In ActiveBOM, copy the winning P/N by rightclicking → Copy, then substitute the losing P/N by right clicking → Operations → Change … Search for the winning components and replace. Review the ECO for unexpected parameter changes, then execute. You know if this works because the two lines will combine to one (unless part revision differs, then update your parts from library.

• Only assembly on one side. Two-sided assembly is much more expensive, and only makes sense if you have an even distribution of components on both sides.
• Use generic components. UTAT’s library has a lot of AEC-qualified components which are more expensive and not strictly required for ground testing. You can sub them out by making an alternative solution and (if going with JLC assembly) using an LCSC basic component
  • If using JLC, prefer components here: https://jlcpcb.com/parts/basic_parts — no reeling fee!
• It’s OK to still hand assemble! You can get all the passives installed and do the ICs yourself which can help with part sourcing, or anywhere in between depending on how rare your components are. I’ve heard this called “birdseed” since you’re just installing the parts that look like birdseed

There are two types of costs: setup costs and assembly costs. Setup costs are per design and cover things like reeling, stencil, engineering, etc. Assembly costs are per board and cover the actual BOM, machine time, etc. This can mean that some boards have a high setup cost and low assembly cost (expensive to make one, cheap to make more) and others the opposite (cheap to make one, expensive to make many). While the cost of, for example, 3 boards may seem high, it could just be due to setup costs, and assembling two more may be very inexpensive as a result.

Variants

If you want to have some components not installed/placed, then you will need to use Altium’s Variants feature. Create a new variant named something like “Default” and then go though your schematics and DNP the components that you want non-populated.

I like to use this for what I expect to not want installed in the final product rather than what I want the assembly house to install, since then it documents what the state as-tested will be (padshares, component swaps, etc).

LCSC Part

If ordering from JLCPCB, consider pre-selecting LCSC part numbers to make the final selection of parts go way smoother. This also saves the decisions made into version control, so in the future it’s easier to see what decisions were made.

• In ActiveBOM, Add New → Custom Column → Name = “LCSC Part #”
• On LCSC’s website, the P/N is the 5ish digit number that begins with C . Try to find components from the JLC basic library first: https://jlcpcb.com/parts/basic_parts, then search LCSC directly.
• The inventory is given as AA-BB-CC, JLCPCB will only assemble if there is AA > 0 (i.e. Warehouse-South)
• Specify parts that you don’t want JLCPCB to place as DNP or something like that