1.6 Cost and Lead-Time Drivers Without the Math

The final price of an electronic assembly is not determined by a random markup; it is a summation of physical complexity and supply chain risk. Two PCBA designs may look identical to the naked eye—same size, green solder mask, similar components—yet one costs $15 and ships in 3 weeks, while the other costs $45 and ships in 40 weeks. Understanding the specific levers that drive cost and time allows you to engineer them out of the product before the design is frozen.

1. The BOM: The 80% Gorilla

In almost every EMS project, 70% to 80% of the total unit price is the raw cost of the components (Bill of Materials). Labor is a minor fraction.

The Driver: Sole Sourcing vs. Multi-Sourcing

Standard Parts: A 10kΩ resistor is a commodity. If Brand A is out of stock, the factory buys Brand B. Cost is low; lead time is days.
Sole Source Parts: A specialized sensor or a specific microcontroller available from only one manufacturer.
If a critical chip has a 52-week lead time → Then your entire product launch is delayed by a year, regardless of how fast the factory runs.
Risk: Component obsolescence. If the sole manufacturer stops making it, you must redesign the board.

2. PCB Technology: Layers and Density

The bare board fabrication cost is driven by how many times it must be laminated and drilled.

The Driver: HDI and Via Structure

Standard: A 4-layer board with standard "through-hole" vias (drilled all the way through) is cheap and robust.
Advanced: "Blind" or "Buried" vias (holes that connect internal layers without penetrating the whole board) require laser drilling and sequential lamination.
If you design with High Density Interconnect (HDI) features unnecessarily → Then raw PCB cost can triple.

3. Assembly Complexity: Machine vs. Hand

Machines are fast and cheap; humans are slow and expensive.

The Driver: Through-Hole vs. SMT

SMT (Surface Mount Technology): Pick-and-place machines place 30,000+ components per hour. This is the cheapest way to build.
Through-Hole: Requires component leads to be inserted into holes. While some can be automated, odd-shaped connectors or transformers often require manual insertion by an operator.
If you replace a surface-mount USB connector with a through-hole version → Then you add manual labor cost to every unit.

The Driver: Single vs. Double Sided

If you place components on both sides of the board → Then the board must run through the production line twice (two print, two place, two reflow cycles), effectively doubling the processing time.

4. Test and Yield: The Hidden Tax

"Yield" is the percentage of units that pass inspection on the first try. "Scrap" is the money you throw away.

The Driver: First Pass Yield (FPY)

If a board costs $100 to build and you have a 90% yield, you effectively throw away $10 for every unit you ship. The customer pays for the good units and the bad ones.

If a design is difficult to manufacture (tight clearances, tiny pads) → Then yield drops, and unit price rises to cover the waste.

5. The "Open Book" Quoting Model

Traditionally, manufacturers gave a "Black Box" price: "It costs $50." You had no idea if that was $10 material + $40 profit, or $45 material + $5 profit.

The Solution: Open BOM Transparency

Modern EMS engagements use "Open Book" pricing. The EMS lists the exact cost of every component, their labor rate, and their profit margin explicitly.

Benefit: It empowers the engineer. If you see that one specific connector costs $4.00 and drives the price up, you can design it out.
Control: It prevents "phantom markups" where a supplier pads the cost of cheap resistors.

Pro-Tip: Ask for the "Long Lead Item" (LLI) report during the quoting phase. This highlights the single component that defines the schedule. Often, changing one capacitor can save 20 weeks of waiting.

Final Checklist

Driver	Low Cost / Low Risk	High Cost / High Risk	Action
Components	Generic, Multi-sourced	Sole Source, Proprietary	Validate alternates in the BOM.
PCB	2-6 Layers, Standard Vias	HDI, Blind/Buried Vias, 10+ Layers	Stick to standard stack-ups unless necessary.
Assembly	Single-sided SMT	Double-sided, Heavy Through-hole	Minimize manual insertion parts.
Testing	Automated (ICT/FCT)	Manual Troubleshooting	Design test points onto the board.
Logistics	Sea Freight (4-6 weeks)	Air Freight (3-5 days)	Plan inventory early to avoid air shipping fees.