PCB Pick-and-Place Files: Coordinates, Rotation and Side

A PCB assembly pick and place file tells the assembler where each component belongs, how it is rotated, and which board side carries it. Also called a component placement list (CPL), centroid file, or XY file, it is usable only when its coordinates and angles have agreed meanings. Define the units, board origin, placement reference point, rotation convention, and bottom-side treatment before release. Then verify identifiable components against the assembly drawing and obtain confirmation of the supplier’s imported interpretation, not merely confirmation that the file opens.

Identify the Required Columns in a Pick-and-Place File

A pick-and-place file needs an individual placement record identifying the reference designator, X coordinate, Y coordinate, rotation, and board side. State units and origin in the agreed headers or accompanying release note. Include footprint and component-identification fields when the supplier’s importer requires them; these do not replace the BOM’s part-selection information.

Use this review matrix to agree what the data means before troubleshooting individual placements. The confirmation column describes the evidence to request, rather than assuming that a recognizable column heading guarantees correct interpretation.

Distinguish the placement point from the pickup point

A geometric center, footprint origin and pin location are not interchangeable. In a placement export offering these fields, Center X/Y is calculated between the outermost pad locations, Ref X/Y is the footprint origin and Pad X/Y locates Pad 1. Confirm which pair the receiving workflow expects.

For an asymmetric connector, these points can differ substantially. A placement workflow may require the origin at the center of the smallest rectangle enclosing the footprint pads; an arbitrary library origin may not satisfy it. Agree the placement reference before resolving pickup and recognition. Any conversion must preserve intended pad alignment, not move the component just to provide a convenient nozzle landing area.

State Coordinate Units and the Board Origin

Coordinate units and the board origin establish the scale and position of every placement. Declare both, together with positive X and positive Y directions. A note saying only “origin at the corner” is incomplete when different views show different corners.

Millimeters, inches, and mils must remain distinguishable: 1 inch equals 25.4 mm, and 1 mil equals 0.001 inch. For example, a coordinate of 1.000 inch represents 25.400 mm, not 1.000 mm. Confirm scale using a known dimension before interpreting a large displacement as an origin error.

The version 9.0 exporter in this example distinguishes the drill/place file origin from the page origin and offers an explicit command-line origin-selection flag. Record the actual setting; do not assume the origin visible during editing was used for export.

For a practical release note, describe the datum physically: “Single-board coordinates; millimeters; origin at the lower-left outline corner in the top view; positive X right; positive Y up.” This is a project choice, not a mandatory industry origin.

Check separated features in both axes. One matching point proves neither scale nor rotation. Three non-collinear reference features provide a useful geometric check because a reflected layout cannot generally preserve their labeled arrangement. Treat their agreement as a data-alignment check, not a demonstration of placement-machine accuracy.

Interpret Rotation Using Package and Machine Conventions

A rotation value describes an orientation relative to a defined package zero; it is not a complete orientation instruction by itself. Record the viewing side, positive rotation direction, and the identifiable package feature that establishes zero. Specify clockwise or counterclockwise explicitly, rather than using a sign without a viewing direction. The referenced supplier, for example, publishes its own pin-1 baseline and counterclockwise convention; that does not establish the convention used by every assembler.

Separate the library’s zero orientation, the component’s board orientation, and the machine’s handling of the supplied part. A reel-loading orientation or nozzle setting must not silently redefine which circuit pad receives pin 1. Confirm the physical result with the manufacturer’s package information and the released footprint, rather than interpreting a familiar-looking number.

The values 0°, 90°, 180°, and 270° are useful review examples, not a complete set of permitted placements. An intentionally angled component may require another value. Likewise, -90° and 270° describe equivalent geometric orientations only when they use the same reference frame and positive direction; an importer may still require a particular numeric representation.

Machine software also distinguishes nozzle rotation modes. The reference implementation offers AbsolutePartAngle, relative to library orientation; PlacementAngle, compensated for final placement; MinimalRotation, using relative rotation after pickup; and LimitedArticulation, within available travel. Its PlacementAngle and LimitedArticulation modes require the specified pre-rotate vision setup.

These are machine-configuration choices, not alternative meanings to assign casually to the customer’s CPL. Ask the assembler to identify the package mapping and preserve the intended pad-to-pin relationship. Accept a numerical conversion only after its scope and physical outcome are established. Never prescribe a board-wide 90° or 180° correction merely because one component appears wrong.

Handle Bottom-Side Coordinates and Mirroring Explicitly

A bottom-side designation identifies the mounting surface; it does not explain whether coordinates are already mirrored. Specify whether bottom placements use a common top-view projection or a coordinate frame defined while looking directly at the bottom. Label assembly views accordingly.

The version 9.0 export example can negate bottom-layer X coordinates. A separate placement-export option reverses bottom-side Ref-Y and Pad-Y values. That option does not by itself establish the behavior of Center-Y. Record the applicable exporter, fields and settings.

Board setup adds another transformation stage. Distinguish board coordinates from the machine location and orientation of the board, including side-dependent handling. Account for any export coordinate conversion when configuring the receiving workflow.

Write a specific instruction, such as: “Bottom X/Y remain in the common top-view frame; no manual mirror has been applied. The receiving setup must reproduce the identified bottom-side pads.” This avoids a double transformation without prescribing a particular machine command.

Mirroring positions and interpreting rotations are related but separate checks. Define the flip axis, origin, and viewing direction before evaluating a bottom drawing. A correct-looking rectangular board outline alone cannot prove that an asymmetric part or its pin sequence is correct.

Check Polarity-Sensitive Parts Against Assembly Drawings

Polarity-sensitive parts validate a CPL by connecting an abstract angle to an identifiable physical terminal. Choose reference components whose pin-1 location, cathode, positive terminal, or connector key can be checked against the released assembly view. An incorrect library pin-1 definition can undermine apparently consistent placement data.

For the review, assemble a compact evidence set: the manufacturer’s package drawing, the approved footprint with numbered pads, the side-labeled assembly drawing, and the supplier’s imported overlay. Compare the same physical feature in the same view. A bottom package drawing cannot be compared directly with a top-view projection without accounting for the view change.

Use an integrated circuit and a polarized two-terminal part where available. Add an asymmetric connector when its placement reference differs from its body center. For a double-sided board, include an identifiable bottom-side device rather than checking top placements alone.

A symmetric resistor may reveal a coordinate error but cannot, by shape alone, expose every orientation error. Similarly, use silkscreen as supporting evidence, not as a substitute for the approved terminal mapping.

When the package information, footprint, and assembly drawing disagree, pause the affected placement and obtain engineering resolution. Do not choose whichever source makes the current export appear correct. This review validates CPL interpretation; it does not replace a separate investigation of conflicting polarity evidence.

Agree the Export and Import Interface

A PCB assembly pick and place file needs a documented export-to-import interface. The following options belong to the named tools and services; they are not a universal format specification or a statement of JASPER’s equipment configuration.

Save the export settings with the release. After importing, inspect the interpreted units, coordinates, side labels, and angles. Successfully reading a CSV proves that its syntax was accepted; it does not prove that the correct coordinate pair or package convention was selected.

A Worked CPL Review from Export to Supplier Confirmation

A CPL review should demonstrate agreement between numerical records and identifiable physical features. The following illustrative control-board example uses explicit geometry; it is not a customer production record or an actual machine export.

1. Define the example and export contract

The example board is CTRL-C, revision C, measuring 80.000 × 50.000 mm. It uses single-board coordinates with the origin at the lower-left outline corner in the top view. Positive X points right and positive Y points up. Both sides retain this common top-view X/Y frame.

The placement points below are the agreed package reference centers. Angles remain relative to each example library definition. Top angles are counterclockwise in the top view. The bottom example uses counterclockwise angles in its direct bottom-side package view; its zero definition is stated separately below.

Reference,X_mm,Y_mm,Rotation_deg,Side,Footprint
U1,20.000,15.000,90.000,Top,IC_A
D1,45.000,10.000,180.000,Top,DIODE_A
J1,70.000,40.000,0.000,Top,CONNECTOR_A
U2,15.000,35.000,90.000,Bottom,IC_B
R1,60.000,8.000,0.000,Bottom,RESISTOR_A

The footprint names identify this illustration’s definitions, not purchasable parts. Three decimal places indicate display precision, not a placement tolerance. For an actual release, retain traceable library identities and the supplier’s required component fields. The CSV is a review example, not a promise of direct compatibility with every importer.

2. Check scale and the shared origin

Use three labeled outline-related reference features at A = (5.000, 5.000), B = (75.000, 5.000), and C = (10.000, 45.000) mm in the common frame. A-to-B separation is 70.000 mm. Together, the three features make translation, scale, and reflection errors easier to distinguish.

Suppose all imported features are displaced by (+10.000, +5.000) mm while their separations remain unchanged. That pattern suggests a common translation mismatch. Investigate the origin mapping before editing component coordinates; the pattern is evidence, not proof of a single root cause.

3. Verify placement points and top rotations

For U1, the zero-orientation vector from its placement center to pin 1 is (-1.000, +1.000) mm. Rotating that vector 90° counterclockwise gives (-1.000, -1.000), so pin 1 must appear at (19.000, 14.000) mm. This checks an orientation, not just the center location.

For D1, the zero-orientation vector to the cathode is (-1.000, 0.000) mm. At 180°, the cathode must appear at (46.000, 10.000) mm.

J1 illustrates a different issue: its agreed placement center is (70.000, 40.000), but its footprint origin and pin 1 are at (66.000, 38.000) mm. Importing that origin as the center would shift the placement by (-4.000, -2.000) mm. Do not diagnose this as a board-origin error when other components align.

4. Verify the bottom view without rewriting the CPL

For this illustration only, turn the board about its vertical midline, parallel to the top-view Y-axis. In the resulting direct bottom view, define a new lower-left origin, positive X right, and positive Y up. The original top-view lower-right corner becomes this bottom-view origin.

Common top-view frame:  X right, Y up, origin at original lower-left
Direct bottom frame:   X right, Y up, origin at original lower-right
For this 80.000 mm-wide board and this stated flip only:
x_bottom_view = 80.000 - x_top_view
y_bottom_view = y_top_view
U2 center: (15.000, 35.000) -> (65.000, 35.000) mm

In U2’s example bottom-side library, the zero-orientation pin-1 vector is (-1.000, -1.000) mm in the direct bottom frame. A 90° counterclockwise rotation produces (+1.000, -1.000). Pin 1 therefore appears at (66.000, 34.000) in that bottom view, corresponding to (14.000, 34.000) in the common top-view projection.

R1’s zero-orientation long axis runs left-to-right in the direct bottom view, so its 0° record must remain horizontal. Its reflected center is (20.000, 8.000) mm.

Negating X about the original zero would instead give -15.000 mm for U2, not 65.000 mm. This reflection constructs a labeled drawing view. It is not an instruction to change the exported X value to 65.000, nor does it define a universal bottom-side rotation conversion.

5. Close the review with identifiable evidence

A complete supplier confirmation for this example would state:

CTRL-C revision C was interpreted in millimeters using the stated single-board origin. Bottom X/Y were retained in the common top-view frame. The imported placement points and identified terminal locations match the review table in the labeled views. The export settings, importer mapping, and resulting program revision are retained with the review. Any change to the intended pad-to-pin relationship requires engineering approval before placement.

The real release also needs the reviewed file identities, overlay evidence, responsible approver, and applicable machine-program revision. Do not substitute this example wording for those records.

Five Application Scenarios for CPL Review

CPL review should emphasize the conventions most likely to change in the particular handoff. These five scenarios apply the preceding checks without treating every project as an identical file-conversion exercise.

First SMT prototype

Check the export against the board outline and a recognizable integrated circuit before machine programming. Resolve the reference-point definition while the placement list is small enough to inspect closely. Retain the settings so a later export can be compared with the same interpretation.

Double-sided controller

Review an identifiable component on each side and label both assembly views. Confirm whether bottom coordinates remain in the top-view frame. A successful top-side import cannot demonstrate correct bottom-side mirroring, package orientation, or board-fixture setup.

Board with an asymmetric interface connector

Compare the connector’s agreed placement point, pad positions, and mating orientation. This is especially useful where a library origin sits at pin 1 rather than at the selected center. Separate a component-specific offset from a global board shift.

Transfer to another assembler

Revalidate the imported physical orientation even when the customer’s CPL has not changed. The new supplier must establish its own package mapping and machine setup. Preserve the source design intent instead of inheriting unexplained numerical corrections from the previous supplier.

Panelized production

Decide whether the supplier receives single-board placements plus a panel map or expanded panel coordinates. Verify instance identity and the placement of an asymmetric component in each differently rotated instance. Avoid applying panel offsets twice; retain an explicit relationship to the single-board coordinate frame.

Frequently Asked Questions

A CPL is ready for review when the receiving team can interpret its coordinates, sides, and package orientations without guessing.

Next Step: Submit an Interpretable Placement Package

For a JASPER review, prepare the CPL, export-setting record, side-labeled assembly drawings, applicable BOM, and board outline. Add a compact note defining units, origin, reference points, rotation conventions, and bottom-side treatment. Identify the parts that will demonstrate correct interpretation.

Use JASPER’s PCB assembly services to discuss the project handoff. Before production release, obtain agreement on the imported physical placements and responsibility for any necessary conversion. Keep that agreement tied to the reviewed files and program revision.