PCBA Cost: What Drives the Price of an Assembled Board

PCBA Cost: What Actually Makes Up the Price

Two quotations for the same board can differ by a factor of two, and the reason is almost never that one supplier is more expensive. It is that the two quotations cover different things, or that one of them was priced against assumptions rather than against real part numbers. Understanding what sits inside a PCBA price is what makes a quotation comparable and a cost reduction programme actually work.

The five elements inside a turnkey PCBA price

An assembled board price is the sum of a small number of very different cost types. They behave differently as quantity changes, and they respond to different levers.

The useful consequence is that component cost, which usually looks like the largest line, is the one a factory can influence least. Design choices influence it, but the purchasing department cannot buy a part below its market price, and a supplier who claims to is either sourcing from a channel with counterfeit risk or has built a margin into another line.

Why the unit price falls as quantity rises

The reduction is not a volume discount in the sense of a supplier choosing to charge less. It is arithmetic. Setup work is performed once regardless of whether the build is 50 boards or 5,000, and its cost is divided by the number of boards. The table below shows the shape of that curve on a representative industrial control assembly.

This is the reason a price quoted at 10 units says very little about the price at 5,000, and why a supplier should state the quantity band the quotation applies to.

The six decisions that move the number most

• Quantity and panel utilisation. How the board arrays on the fabrication panel is one of the largest single levers on bare board cost, and it is a design and panelisation decision rather than a purchasing one.
• Layer count, copper weight and material. These set the fabrication route. A four layer board and an eight layer board are not the same product, and heavy copper changes the assembly thermal profile as well as the board cost.
• Surface finish. ENIG, HASL and immersion silver differ in cost, in the storage window and in solderability. Changing the finish later changes all three.
• Acceptance class. Class 2 and Class 3 differ in inspection criteria and in the records retained. The class is fixed at quotation because it changes both the inspection effort and the documentation.
• Turnkey or consigned material. If the factory buys the components, the price includes sourcing, incoming inspection and availability risk. If the customer consigns them, those costs move to the customer and reappear as shortage risk and import duty.
• Test scope. Inspection only, in-circuit test or functional test, and whether a fixture has to be built. Test coverage is frequently the line that makes two quotations look different when the boards are the same.

Comparing two quotations properly

Quotations can only be compared if they are broken into the same parts. Ask for component cost against the BOM, bare board fabrication, assembly, test, and one-time items as separate lines, with the quantity band, the acceptance class, the surface finish and the material sourcing route stated. A lower headline figure that omits test coverage, assumes a cheaper finish or prices components from an unnamed channel is not a lower cost once the missing items are added back.

The quotation requirements page lists the file set that produces an accurate figure in the first place, and the DFM review is where most of the decisions above get tested against the process.

Where cost actually comes out of a programme

Savings that recur come from design and planning rather than from pressure on an hourly rate. In practice the levers that pay are these:

• Better panel utilisation. A change to board dimensions or spacing can remove more cost than a year of price negotiation, because it affects the largest shared input.
• Replacing obsolete and single-source parts. A pin-to-pin alternative removes both a price premium and a supply risk, and is normally found during DFM review rather than after a shortage.
• Standardising across products. Using one surface finish, one laminate and one solder mask colour across a product family reduces setup and removes changeover losses.
• Consolidating builds. Fewer, larger builds lower the per-board share of setup, even when total annual volume is unchanged.
• Take the material turnkey. Buying boards, parts and assembly from three suppliers stacks three margins and three sets of freight and duty. The turnkey model removes that stacking.
• Design for the process. Removing a part, relaxing a tolerance or reducing a layer count at design stage costs nothing compared to doing it after tooling exists.

What does not pay is asking for a lower hourly rate. Assembly labour is a shrinking share of a modern board price, and a supplier who discounts the rate is usually recovering it somewhere else.

Why an invoice can come in above the quotation

A well constructed quotation is normally held for the quantity and specification it was issued against. It can move for four reasons, and a supplier who names them in advance is easier to work with than one who does not.

• Quantity falls below the quoted band. If a build is cut after the material plan is fixed, the one-time items do not shrink with it.
• Component market movement. Memory, power semiconductors and passive components move in cycles. On a long programme the quotation states how material price movement is handled rather than assuming it away.
• Scope added after quoting. Coating, box build, additional test coverage or a higher acceptance class each add a process step and a documentation requirement.
• File revision after material is ordered. The ordering page sets out what a change costs at each stage, from free before material release to a new bare board after fabrication.

Quotation validity and the component market

Quotations here are normally issued with a validity window rather than as a permanent price, because component prices and availability genuinely move. The window is stated on the quotation. On a repeat programme, the structure of the quotation is kept and the material lines are refreshed against current availability, which is faster than re-quoting from the beginning and keeps the comparison with previous orders possible.

What it costs to start

First-order one-time items are usually a stencil, a test fixture if functional test is specified, a programming jig if the board needs programming, and first article inspection. Their cost depends on board size and test complexity rather than on quantity, and they are stated as separate lines so the customer can see what is repeatable and what is not. On a repeat build the stencil and fixture are already owned, which is a large part of why the second order is cheaper than the first.

Getting a number you can plan against

A price becomes useful when it is tied to a quantity, a specification and a date. Send the file set to Gelant.lei@kilandu.com, and the quotation comes back with component cost, fabrication, assembly, test and one-time items broken out, with the lead time and the minimum quantity stated. Typical turnkey lead time is 2 to 5 weeks from a complete file set. The MOQ and lead time page explains what sets those two numbers, and the Shenzhen factory page describes the site the boards are built on.