Through-Hole PCB Assembly Cost: What Drives It
Why Through-Hole Assembly Costs More Than SMT
A surface mount joint is made by a machine that places a component and an oven that solders a thousand joints at once. A through-hole joint is made by inserting a lead into a hole and soldering it, and inserting a lead is a mechanical operation that is difficult to automate for a mixed board. That single difference explains most of the cost gap: surface mount assembly typically costs around 0.50 to 2.00 US dollars per board in volume, while through-hole assembly runs from about 2.00 to 15.00 dollars per board depending on the mix.
Where a board carries both technologies, the price sits in between, generally 3.00 to 10.00 dollars, because the board passes through two soldering processes and two inspection steps.
The Cost Breakdown
- Board material. Roughly 1.00 to 8.00 dollars per board, driven by the area, the layer count, the copper weight, the finish and the quantity.
- Components. Roughly 0.50 to 15.00 dollars per board, and the largest single variable. A handful of connectors and electrolytic capacitors cost a few cents each; a transformer, a relay or a power module can cost dollars on its own.
- Insertion labour. Roughly 0.50 to 3.00 dollars per board for a simple mix, rising to 2.00 to 3.00 dollars where the component count is high or the layout is dense. This is the step that separates through-hole assembly from surface mount.
- Process and equipment. About 0.20 to 1.50 dollars per board for the wave or selective solder machine, the flux, the cleaning and the depreciation of the line.
- Test and inspection. About 0.50 to 2.00 dollars per board for functional test, visual inspection and any certification testing.
- Setup and tooling. Typically 100 to 500 dollars per order, covering the stencil, the fixture, the programming and the process setup.
- Freight and packing. Usually 50 to 200 dollars per shipment, more for expedited or special packaging.
The setup charge is the reason small orders look expensive per board. Spread over five hundred boards it disappears; spread over ten it dominates the quote.
How the Design Changes the Price
Insertion labour is where a design decision turns directly into money.
Hole diameter. Enlarging a through-hole from 0.8 to 1.0 millimetres makes it easier to insert the lead by hand or by machine, and can save around 0.30 dollars per board across a board with many holes. The limit is set by the pad size and the solder volume, so the hole is enlarged as far as the layout allows and no further.
Component count. Every additional through-hole part adds an insertion and a joint. Simplifying the design to remove a few components can save 0.50 to 1.00 dollars per board.
Layout density. A crowded layout slows the operator and increases the risk of a touch-up, pushing the labour cost from around 0.50 to 1.50 dollars up to 2.00 to 3.00 dollars.
Pad and lead geometry. Standardising the pad shapes and the lead forms reduces the setup and the handling time, and simplifies the wave solder process.
Assembly direction. A board that is designed so that all the through-hole parts can be wave soldered in one pass, rather than needing selective soldering in several steps, costs less and yields better.
A design that follows the manufacturability guidelines, with standard parts, generous holes and a simple layout, can reduce the assembly cost by 10 to 30 percent, which is 0.50 to 3.00 dollars per board on a typical project. Our notes on PCB manufacturing describe the fabrication side of the same rules, and our notes on SMT PCB assembly cover the surface mount process that usually shares the board.
Wave Soldering and Selective Soldering
Two processes make through-hole joints in production. Wave soldering passes the board over a standing wave of molten solder, which solders every exposed joint in a single pass and is the cheapest option where the board has many through-hole parts and can tolerate the thermal exposure. Selective soldering uses a small nozzle to solder one joint or one group at a time, which is slower but suits boards that already carry heat sensitive surface mount parts on the same side.
The choice affects the cost more than the solder does. A single wave pass costs a fraction of a selective programme with several positions, and it avoids the extra flux and cleaning that selective soldering can require. Where the design forces selective soldering, the cost is what it is; where the layout can be arranged to allow a wave pass, the saving is real.
Testing and Inspection
Every through-hole joint is visible, so the inspection is optical and the equipment is cheap. That is an advantage, and it is also a trap: a joint that looks good can be cold underneath, and a hole that is not fully filled can pass a visual check. The reliable controls are a controlled solder temperature and flux, a sample cross section to confirm the barrel fill, and a functional test of every board rather than only a visual inspection.
Test adds 0.50 to 2.00 dollars per board and is not optional on a board that has to work. In-circuit test checks the components and the nets, functional test confirms the product operates, and both are recorded. Our notes on quality management describe the process control that keeps the yield up.
Regional Price Differences
Labour is the dominant regional variable. In Asia, through-hole assembly typically quotes 2.00 to 6.00 dollars per board, while Europe and the Americas quote 3.00 to 10.00 dollars for the same work in small quantity. Freight and customs add to the landed cost of an offshore build, and the lead time includes shipping, so the comparison should be made on the delivered price and the delivered date rather than on the assembly quotation alone.
Component supply affects both regions. Shortages and allocation push the board cost up regardless of where it is assembled, and a design that accepts a second source for the critical parts is cheaper to keep in production than one that does not.
How to Estimate a Project
- Produce a complete bill of materials with the board specification and the quantities.
- Separate the through-hole parts from the surface mount parts, because they are costed differently.
- Get quotations from more than one assembler on the same data package.
- Add the setup charge, the test cost and any rework allowance of 0.50 to 2.00 dollars per board.
- Hold 10 to 15 percent of the budget for the unexpected, which on a first build is usually the components rather than the labour.
Where the volume is high enough, an order can push the unit price from around 15 dollars at prototype quantity down to 2 dollars, so the quantity decision is worth making before the supplier decision. Our notes on PCB assembly describe the process in more detail, and our notes on turnkey PCB assembly cover the option of buying the finished assembly rather than managing the components separately.
FAQ
Why is through-hole assembly more expensive than surface mount? Because each lead has to be inserted mechanically, while surface mount components are placed by machine and soldered in a single oven pass.
Is the setup charge included in the unit price? No. It is quoted separately and typically runs 100 to 500 dollars, depending on the complexity and the volume.
How long does through-hole assembly take? Prototypes usually about five working days, and volume orders around three weeks, including the component lead time.
How much can a better design save? Following the manufacturability guidelines, with standard parts, larger holes and a layout that allows a single wave solder pass, can reduce the assembly cost by 10 to 30 percent.
Conclusion
Through-hole assembly costs more than surface mount because inserting leads is a mechanical operation rather than a printing one. The price is driven by the board, the components, the insertion labour, the soldering process and the test, with the setup charge making small orders expensive per board. Enlarge the holes where the layout allows, standardise the parts, arrange the board so that one wave pass does the work, and test every board: those four decisions move the unit cost more than any negotiation.
