Turnkey PCB assembly: what's included, what sets the lead time, and what drives the quote
You send files, not parts, and the assembler sends back working boards. Easy to order, harder to read the quote: most of what you pay for is parts, and the slowest part on the BOM sets the date.
Filed under Engineering and services
Short answer: Turnkey PCB assembly means one supplier buys the bare boards and every component on your BOM, assembles and tests the boards, and ships them finished. You send files, not parts.
Turnkey PCB assembly is the default way small and mid-size hardware companies buy boards. You send a package of files, the assembler sends back working boards, and nobody on your side has to chase reels of capacitors. It is simple to order. It is harder to read the quote, because most of what you are paying for is not on the assembler's own shop floor. This note covers what turnkey includes, how it differs from partial turnkey and consigned builds, what sets the lead time, and the lines that move the price.
What turnkey PCB assembly includes
The Wikipedia entry on electronics manufacturing services lists what an EMS company can cover: "printed circuit board assembly, component sourcing, new product introduction, design for manufacturability (DFM) reviews, testing, and box-build or system integration." A turnkey board order pulls most of that into a single purchase order:
- Bare board fabrication, usually bought by the assembler from a board shop it already works with.
- Component sourcing for every BOM line, including the extra parts lost in machine setup.
- A DFM and DFA review of your files before anything is bought.
- SMT and through-hole assembly, with the stencil and machine programs.
- Inspection and test: AOI, X-ray where the parts need it, and whatever functional test you specify.
- Packing and shipping of finished boards.
What it does not include unless you ask: a test fixture (that is a separate, one-time cost), conformal coating, programming beyond a standard image, box build, and any engineering help with the design itself. If you need one of those, put it on the RFQ so every quote covers the same work.
Turnkey, partial turnkey and consigned
The difference is who buys the parts.
| Model | Who buys components | Who carries attrition and shortages | When it fits |
|---|---|---|---|
| Full turnkey | The assembler | The assembler, priced into the quote | Most programs; you want one party responsible for the whole board |
| Partial turnkey | The assembler buys most lines; you supply named parts | Split by line | You hold stock of a costly or programmed part, or have better pricing on a few lines |
| Consigned (kitted) | You buy and ship every part | You | You already run a purchasing team with an approved vendor list |
Consigned looks cheaper on paper because the assembler is quoting labor only. In practice it moves work and risk to you. Assemblers set kitting rules that a consigned build has to meet. The assembler wants to buy the commodity parts itself.
Partial turnkey is often the practical middle. You supply the two or three parts that are expensive, scarce or pre-programmed, and the assembler buys the rest.
What sets the lead time
- Parts. The assembler cannot start until every line is in the building. One long-lead regulator or connector holds the whole build, no matter how fast the line is.
- Bare boards. Fabrication runs in parallel with parts buying, and usually finishes first on simple boards. HDI, heavy copper or unusual materials take longer.
- Assembly and test. Programming, first-article checks, the build itself and test.
The best case is fast. Sierra Circuits, a US quick-turn shop, advertises full turnkey boards "in as fast as 5 days." That speed depends on every part being in stock at a distributor. When a part is not, the schedule is set by that part's factory lead time, not by the assembler.
Two habits shorten it. Check part lifecycle before you release the BOM. Sierra's note on end-of-life and obsolete components recommends that sourcing teams "conduct periodic bill of materials checks to identify components approaching NRND, EOL, or obsolescence." And list approved alternates on the BOM for every line where an alternate is acceptable, so the buyer does not have to stop and ask you.
What drives a turnkey quote
When you compare quotes, these are the lines that move the total:
- The parts. Components are often the largest share of a turnkey price, especially at low volume. The quote reflects the assembler's buying price and the quantity it has to buy, which can be a full reel, not the exact count you need.
- Attrition. Pick-and-place machines lose small parts during setup and running.
- Minimum buys and leftovers. If a part only sells by the reel, someone pays for the whole reel. Ask who owns the leftover parts, whether they are held for your next order, and for how long. The EMS ownership note covers excess and obsolete inventory terms in more detail.
- One-time costs. Stencils, machine programming, test fixtures and first-article inspection are usually charged once. Make sure they appear as separate lines, so you can see them and not pay for them again on the reorder. See what NRE cost covers.
- Workmanship class and inspection. A board judged to IPC-A-610 Class 3 costs more to build and inspect than a Class 2 board. Name the class on the RFQ so every quote is built to the same standard.
- Quantity and quote validity. Unit price falls with volume because setup is spread across more boards. Component prices move too, so ask how long the quote is valid and what happens if a part's price changes before purchase.
What to send so the quote is real
A turnkey quote is only as good as the package behind it. Send a complete BOM with manufacturer part numbers and approved alternates, Gerbers and drill files, a centroid file, an assembly drawing, the workmanship class, and a test specification. The PCBA checklist walks through each file and the questions to settle before the first build. If you are still deciding whether one supplier should run the whole product and not just the board, turnkey manufacturing covers that wider question.
Before you sign, ask four things in writing:
- Which BOM lines will be bought from the manufacturer or an authorized distributor, and what happens if one is not available.
- Whether any substitution, even an "equivalent" passive, needs your written approval. It should.
- Which one-time costs are in the quote, and which ones repeat on a reorder.
- Who owns leftover components and test fixtures, and where they are kept.
How JCH runs a turnkey board
Jack runs turnkey board builds for US companies with partner assemblers. He reviews the file package and BOM before anything is quoted, so the quotes compare like for like. He settles the workmanship class, alternates and one-time costs in writing, and he checks the first boards against your drawing before volume. The steps are laid out on the electronics and PCBA process page, and inspection is covered in how lots are inspected. If you have a board ready to quote, send the package.
Straight answers
What is turnkey PCB assembly?
Turnkey PCB assembly is a board build where one supplier buys the bare boards and every component on the BOM, assembles and tests the boards, and ships them finished. The buyer sends the file package (BOM, Gerbers, centroid file, assembly drawing, test specification) instead of parts.
What is the difference between turnkey and consigned PCB assembly?
In a turnkey build the assembler buys the components and carries attrition and shortages. In a consigned (kitted) build the buyer buys and ships every part, meets the assembler's kitting rules, and carries the attrition. Partial turnkey splits it: the buyer supplies a few named parts and the assembler buys the rest.
What sets the lead time for turnkey PCB assembly?
Three clocks: getting every component in, fabricating the bare boards, and assembly and test. The parts clock usually decides it, because the build cannot start until the slowest part on the BOM arrives. Quick-turn shops can deliver in days when every part is in distributor stock.
Why does a turnkey PCB assembly quote include extra parts?
Pick-and-place machines lose small parts during setup and running, so assemblers buy extra (attrition), and some parts can only be bought by the full reel. Those extras, and any reel minimums, are in the turnkey price. Ask who owns the leftover parts and how long they are held.
What should I send to get an accurate turnkey PCB assembly quote?
A complete BOM with manufacturer part numbers and approved alternates, Gerbers and drill files, a centroid (pick-and-place) file, an assembly drawing, the IPC-A-610 workmanship class, and a test specification. Ask each supplier to list one-time costs separately.
How this note was made: researched and drafted with AI assistance, checked against the sources listed below and edited at JCH Design & Manufacturing.