As a PCBA company, we'd like to give you some insight into the pricing. It is great, that you are trying to understand how the prices change at different production quantities.
The sharp bend in your original graph at 10 pieces is accurate in our experience. I would like to add that beyond 1000 pieces a company is not likely to achieve much more cost savings, so I'd say that approximates volume pricing for the given circuit design and the manufacturer.
There are different factors when it comes to the cost of a PCB assembly. What is important to note is, that the designer determines the price more than anything. Your component selection and technological constraints define the cost beyond what optimization any EMS company can bring to the table.
Factors for PCB Assembly Pricing include:
- Component Selection and pricing.
- Bare PCB price based on technology, layer count, drill sizes etc.
- Manufacturing technologies used, such as SMD and THT assembly.
When it comes to how much the cost scales down with volume, you will see the lowest effect in THT assembly. Since this is generally a manual process, there is close no setup cost associated. There is a case to be made, that with very large volumes you could optimize the order of how things are placed or automate more of the component preparation. But as a rule of thumb, most EMS companies are probably not showing much scale effect in THT assemblies. Please note that double-sided SMD assembly with THT components on TOP or BOT can get quite expensive since those tend to be hand-soldered pin-by-pin instead of wave soldered unless the manufacturer uses selective soldering for THT. Here I found 10 cents per manual solder joint to be a good reference.
With SMD components, the design is really important. Generally, components smaller than approximately 5x5mm will have significantly higher assembly speeds compared to larger components. The sizes vary based on the manufacturer's pick and place machines, but I found 5x5mm or "smaller than SO8" to be a good reference. The assembly speeds of these small or large components vary by order of magnitude. On our standard assembly lines, we place slow components (large) with a speed of 1500 pieces per hour and fast components (small) with a speed of 7500 pieces per hour. If you figure an average pick and place line costs about half a million dollars and has an hourly rate of 200 USD with an operator, you can roughly estimate costs.
While I differentiate between large and small components when it comes to assembly speed, it is also important to note that component sizes smaller than 0603 tend to get more expensive again because of the very small size and large components can be more expensive if they are BGA or finepitch.
In addition, please keep in mind that SMD assembly requires the machines to be set up. Based on how many different components you have, this can be done in 30 minutes if the EMS company is focused on rapid prototyping or can take up to a day of machine downtime.
Summary:
- The price of the final PCB assembly cost is determined mostly by the design and component selection.
- THT assembly costs don't scale as much as SMD assembly cost because of setup times.
- Quantities under 10 pieces rarely make sense from a cost perspective.
- Quantities over 1000 pieces typically approximate volume pricing.
We do have some resources available on our Electronics Manufacturing Knowledge Base that may help you improve your product cost, such as our "Design Checklist for PCB Assembly" or our "Design Rules for Low-Cost PCB Manufacturing".
