What to Send for a PCBA Quote: Gerber, BOM, and CPL Files Explained
A PCBA quote is only as fast as the files behind it. Here is what each file is for, what goes inside it, and the mistakes that most often send a quote back with questions.
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Most delays in a PCB assembly quote have nothing to do with pricing. They come from a missing file, a BOM line nobody can identify, or a placement file that does not match the board. The engineer reviewing your request has to stop, write to you, and wait.
This guide covers the three files every assembly quote depends on, what each one needs to contain, and a short checklist to run before you submit.
The three files, and what each one answers
File
Question it answers
Required?
Gerber
What does the bare board look like?
Yes, to submit a request
BOM
Which parts go on it, and how many?
Needed before we can price
CPL
Where does each part go, and which way round?
Needed before we can price
You can submit a request with Gerber files alone and add the BOM and CPL afterwards. The quotation clock starts once all three are in.
Gerber files
Gerber files describe the bare board layer by layer: copper, solder mask, silkscreen, and the board outline. The drill file, usually in Excellon format, lists every hole.
A complete set includes:
All copper layers, top to bottom
Solder mask and silkscreen for both sides
Solder paste layers, which are used to make the stencil
The board outline
Drill files for plated and non-plated holes
Export them from your design tool and put them in a single archive. We accept zip, rar, and 7z archives, as well as individual gbr, ger, and pcb files.
Common problems
No board outline. Without it nobody knows where the board ends.
Missing paste layers. The fabricator can still build the board, but the assembler cannot cut a stencil.
Layers from two revisions. If you re-export one layer after a late change, re-export all of them.
Requirements that live only in your head. Gerber data does not carry board thickness, copper weight, surface finish, or impedance targets. State them on the request form or attach a fabrication drawing.
Bill of materials (BOM)
The BOM lists every component on the board. For quoting, the manufacturer part number matters more than anything else in the file.
Each line should have:
Column
Example
Why it matters
Reference designators
C1, C2, C5
Links the line to positions on the board
Quantity
3
Must equal the number of designators
Manufacturer part number
GRM155R71C104KA88D
Identifies the exact part to buy
Manufacturer
Murata
Removes doubt when part numbers look alike
Description
0.1 µF 16 V X7R 0402
Lets a reviewer catch a wrong part number
Package
0402
Confirms the part fits the footprint
Send it as a spreadsheet: xls, xlsx, csv, or txt. A PDF of a spreadsheet has to be retyped by hand.
Common problems
Descriptions without part numbers. "10k resistor 0603" can be met by hundreds of parts with different tolerances and prices. If any of them will do, say so. If not, give the part number.
Quantity does not match the designators. A line that says quantity 4 and lists three designators will be questioned every time.
Do-not-populate parts left in. Mark them clearly as DNP or remove them.
Distributor part numbers only. A distributor's stock code is tied to one seller. The manufacturer part number can be sourced anywhere.
Decide how parts will be sourced
Your request should say which sourcing model you want:
Turnkey. We buy every part on the BOM.
Consigned. You ship all parts to us.
Partial turnkey. You supply some parts and we buy the rest. List which ones you are supplying.
For turnkey and partial turnkey builds, also say whether substitutes are acceptable. You can allow us to propose alternatives for your review, ask to be consulted first, or require exact parts only. Exact parts only is the safest choice and the slowest when a part is out of stock.
Component placement file (CPL)
The CPL tells the pick-and-place machine where each part goes. You will also see it called a pick-and-place file, a centroid file, or an XY file.
Each line needs five things:
Column
Example
Notes
Reference designator
U3
Must match the BOM exactly
X position
24.130
Center of the part
Y position
18.415
Center of the part
Rotation
90
In degrees
Side
Top
Top or bottom
State the units, millimeters or mils, in the file. Send it as xls, xlsx, csv, or txt.
Common problems
Designators that do not match the BOM. "R01" in one file and "R1" in the other are different parts to a machine.
Units not stated. A coordinate of 1000 could be one inch or one meter.
Origin not stated. Coordinates are measured from a reference point. Use the same origin as your Gerber export, typically the lower-left corner of the board.
Bottom-side parts mirrored incorrectly. Design tools handle the bottom side in different ways. Export the bottom-side placements as your tool produces them and do not adjust them by hand.
Rotation deserves a note of its own. Design tools and component reels do not always agree on what zero degrees means for a given package. This is normal, and it is one reason every placement file is checked against the board before production. Marking pin 1 and polarity clearly on the silkscreen makes that check quick.
Other files worth attaching
None of these are required, but each one removes a question:
Assembly drawing. Shows polarity, orientation, and any parts that need special handling.
Fabrication drawing or stack-up. Carries the bare-board requirements that Gerber files leave out.
Test procedure. Needed if you want functional testing. Without one, there is nothing to test against.
STEP model. Useful when the board has to fit an enclosure.
Details the form will ask for
Have these ready alongside your files:
Quantities. You can request up to three quantity tiers in one quote, which shows where the price breaks fall.
Assembly sides. Top, bottom, or both.
IPC-A-610 class. Class 2 suits most commercial and industrial products. Class 3 is for high-reliability electronics where continued operation is critical. The class changes workmanship criteria and cost, so choose it before the quote, not after.
Testing. AOI, X-ray, in-circuit test, functional test, or flying probe. Fixture-based tests take time to prepare.
Who supplies the bare boards. We can fabricate them, or you can ship your own.
Before you submit
The Gerber archive contains every copper layer, both masks, both silkscreens, both paste layers, the outline, and the drill files
All layers come from the same export
Board thickness, copper weight, and surface finish are stated on the form or a drawing
Every BOM line has a manufacturer part number, or says that any equivalent is acceptable
BOM quantities match the designator counts
Do-not-populate parts are marked or removed
Every designator in the CPL appears in the BOM, with identical spelling
The CPL states its units and origin
Pin 1 and polarity marks are visible on the silkscreen
Sourcing model, substitution policy, IPC class, and test requirements are decided
What happens after you submit
An engineer reviews the files and writes to you if anything is unclear. Once the required files are complete, you receive an itemized quotation, typically within one business day. Nothing is charged at the request stage. You decide after you have seen the numbers.
If your design is confidential, you can sign an NDA online before you upload anything.
