What Is a Pick and Place File?
A pick and place file (also called a centroid file, XY file, or insertion file) is a plain-text data table that tells an automated SMT assembly machine the exact position, rotation, and board side of every surface-mount component on a PCB. Without it, your contract manufacturer’s pick-and-place machine has no instructions — and your boards don’t get assembled.
In a reverse-engineering or board copy context, the pick and place file is one of several manufacturing deliverables extracted from a physical sample board. It sits alongside Gerber files, the bill of materials, and netlist connectivity data as part of a complete assembly-ready package.
What a Pick and Place File Actually Contains
The file is typically a CSV or tab-delimited text file. Each row represents one component placement. The columns vary slightly between EDA tools, but the core fields are standardized across the industry:
| Field | Description | Example |
|---|---|---|
| Reference Designator | Unique ID from the schematic (R1, C14, U3) | U7 |
| X Coordinate | Horizontal center of the component body, in mm or mil from the board origin | 45.720 mm |
| Y Coordinate | Vertical center of the component body | 22.860 mm |
| Rotation | Angle in degrees (0–360), counter-clockwise from the EDA tool’s 0° reference | 270° |
| Side | Top or Bottom layer | Top |
| Value / Part Number | Component value or MPN — used to cross-check with BOM | 100nF / GRM155R71C104KA88 |
| Package / Footprint | Physical footprint name (0402, SOIC-8, QFP-144) | 0603 |
Some CMs also expect a height column (Z-axis clearance in mm) so the nozzle doesn’t crash into adjacent tall components during placement. If your board has parts taller than 6 mm — electrolytic caps, connectors, shielding cans — ask your assembler whether they need this field.
How a Pick and Place File Is Generated During Board Copy
When you design a board from scratch, your EDA tool exports the centroid file automatically from the layout database. In a board-level copy service, there is no original design database. The file must be reconstructed. Here is how our engineers handle it:
Step 1 — High-Resolution Imaging
Both sides of the bare and populated board are scanned at 1200+ DPI. A calibrated optical reference (fiducials or board edges) establishes the coordinate origin. For boards where silkscreen markings are unreadable or worn away, imaging also captures pad geometry to help identify footprints.
Step 2 — Component Mapping
Every SMD part is cataloged with its reference designator, footprint, and orientation. This is done in parallel with the BOM extraction and component identification guide process. Pin-1 indicators, polarity marks, and package asymmetries are recorded to determine rotation.
Step 3 — Coordinate Extraction
Component center coordinates are extracted from the reconstructed PCB layout. Our engineers use the pad-center midpoint for two-terminal passives and the body centroid for ICs. Coordinates are referenced to the same origin used in the Gerber files — typically the lower-left corner of the board outline — so that the pick and place file and the stencil aperture data align exactly.
Step 4 — Cross-Verification
The completed file is overlaid on the Gerber copper and paste layers in a CAM viewer. Every component centroid must land within the pad pattern of its footprint. Rotation is verified against pin-1 orientation on the copper layer. A mismatch here — even 90° — means tombstoned ICs or reversed diodes on the production line.
Common Pick and Place File Errors That Kill Assembly Yield
Assembly houses report that centroid-file errors account for a surprising share of first-article failures. These are the problems we see most often when clients bring us files from other sources:
- Wrong origin point. The file uses board center as origin; the CM expects lower-left corner. Every placement shifts by half the board dimension. Fix: agree on the datum before export.
- Rotation convention mismatch. Some EDA tools export clockwise rotation; most CMs expect counter-clockwise (IPC-7351 convention). A 90° part shows up at 270°. Fix: confirm the convention with your assembler and convert if needed.
- Mixed units. X in millimeters, Y in mils, or vice versa. The file looks fine in a text editor but places components off the board. Fix: standardize on mm (IPC preference) and state the unit in the file header.
- Missing bottom-side components. The file only lists the top layer. The CM programs the machine, flips the board, and has no data. Fix: export both sides, either in one file with a Side column or as two separate files clearly labeled.
- Stale reference designators. The BOM says C12 is a 10 µF cap; the pick and place file maps C12 to coordinates where a 0402 100 nF pad pattern sits. This happens when the BOM and centroid file are generated from different design revisions. Fix: regenerate both from the same final layout snapshot.
File Formats and Naming Conventions
There is no single universal file extension. What you receive depends on the EDA tool or the reverse-engineering house that produced it:
| Source / EDA | Typical Extension | Delimiter |
|---|---|---|
| Altium Designer | .csv | Comma |
| KiCad | .pos | Space / Tab |
| Eagle | .mnt / .mnb | Space |
| OrCAD / Allegro | .txt or .plc | Tab / Fixed-width |
| Reverse-engineering output | .csv or .xlsx | Comma |
Most CMs can ingest any of these as long as the column mapping is clear. If you are sending files to a new assembler, include a short README noting the origin point, unit system, rotation convention, and which column is which. Five minutes of documentation prevents five days of rework.
Where the Pick and Place File Fits in the Full Deliverable Set
A pick and place file alone is not enough to manufacture and assemble a board. It is one layer in a stack of interdependent files. Here is how they relate:
| Deliverable | Purpose | Relationship to Pick and Place |
|---|---|---|
| Gerber files (copper, mask, silk, drill) | Bare-board fabrication | Defines the pads the centroid must align to |
| BOM | Component procurement | Reference designators must match 1:1 |
| Pick and place file | Automated SMT assembly | — |
| Stencil aperture file | Solder-paste printing | Aperture locations must match pad locations in the centroid |
| Netlist | Electrical verification (DFM/DRC) | Validates that component placements create correct nets |
| Schematic | Design intent documentation | Source of reference designators and values |
When our team delivers a full PCBA copy and assembly package, the pick and place file ships alongside every item in that table, verified as a matched set. If any single file is regenerated, all dependent files are re-checked.
Tips for Reviewing a Pick and Place File Before Sending to Your CM
- Open the file in a spreadsheet. Sort by reference designator. Look for duplicates — two rows for R7 means one of them is wrong.
- Count the rows (excluding headers). The total should equal the number of unique SMD reference designators in your BOM. Through-hole parts are not included.
- Spot-check 5–10 components against the Gerber overlay. Pick at least one BGA, one fine-pitch QFP, and one 0201/0402 passive.
- Verify that polarized components (diodes, tantalum caps, ICs) show correct pin-1 rotation. A 180° error on a voltage regulator can destroy every board in the panel.
- Confirm the board origin matches the fabrication data. Load both in a CAM viewer and check alignment at the board corners.
When You Don’t Have a Pick and Place File
If you have a legacy board with no design files at all, the centroid data must be reconstructed through a complete reverse engineering workflow. The process recovers Gerbers, BOM, schematic, and the pick and place file as a unified package. Typical turnaround for a 4-layer board with 200–400 components is 7–12 working days; 8+ layer boards or boards with BGA-under-BGA stacking take longer due to the additional imaging and cross-section work involved.
For projects where you already have Gerbers and BOM but are missing only the centroid file, turnaround is shorter — often 2–4 working days — because the pad locations are already defined and only the component mapping and coordinate extraction remain.
Is a pick and place file the same as a centroid file?
Yes. “Pick and place file,” “centroid file,” “XY data,” and “insertion file” all refer to the same deliverable: a text table listing every SMD component’s reference designator, X/Y coordinates, rotation, and board side. The name varies by EDA tool and regional convention, but the content and purpose are identical.
Does a pick and place file include through-hole components?
Typically no. Through-hole parts are inserted by hand or by a separate insertion machine that uses its own programming data. The standard centroid file covers only surface-mount devices. If your board has mixed technology and your CM handles both, ask whether they need a separate through-hole placement file.
What happens if the pick and place file rotation is wrong?
The machine places the component at the wrong angle. For symmetric passives (0402 resistors), a 180° error is electrically harmless. For ICs, connectors, or polarized capacitors, even a 90° rotation error causes open circuits, shorts, or component damage. First-article inspection (FAI) catches most of these, but fixing them mid-run means reprogramming the machine and scrapping affected boards.
Can I generate a pick and place file from Gerber files alone?
Not directly. Gerber files define copper, mask, and drill geometry but contain no component-level intelligence — they don’t know that a set of pads belongs to “U3” or that it’s a QFP-48. You need either the original EDA layout database or a reverse-engineering process that reconstructs component mapping from the physical board and overlays it onto the Gerber data.
How accurate do the XY coordinates need to be?
For standard SMT (0402 and larger), ±0.05 mm accuracy is sufficient — the machine’s vision system and self-centering during reflow handle minor offsets. For fine-pitch parts (0.4 mm pitch BGA, 0201 passives), aim for ±0.025 mm. Our reconstructed centroid files are verified against the Gerber pad centers to stay within these tolerances.
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