What Files Do You Need for an Accurate PCB Assembly Quotation?

What Files Do You Need for an Accurate PCB Assembly Quotation?

Quick Answer: An accurate PCB assembly quotation requires a revision-controlled BOM with manufacturer part numbers and alternates, fabrication Gerbers (or ODB++), pick-and-place centroid data, an assembly drawing with polarity and special process notes, and a clear test specification. Missing centroid files, ambiguous BOM lines, or undefined ICT/FCT scope are the most common reasons quotes slip by days and costs change after award.

Introduction

Procurement teams often send a partial BOM and ask for a “ballpark” PCB assembly price. EMS engineers cannot responsibly price labor, tooling, inspection, and test without knowing board complexity, component mix, and quality gates. For lighting OEMs and industrial product companies, the gap between a rough estimate and a binding quote is almost always documentation — not secrecy from the assembler.

This guide defines the file package Mihoray and other qualified EMS partners need to produce a first-pass accurate PCB assembly quotation. It covers mandatory deliverables, typical gaps that trigger requotes, and a submission checklist you can reuse across NPI and mass-production RFQs.

Definition: What “Accurate Quotation” Means in PCB Assembly

An accurate quotation is a priced offer that reflects real process scope: SMT and/or through-hole loading, stencil and fixture needs, programming, inspection (AOI, X-ray, manual), conformal coating, labeling, test time, and expected first-pass yield assumptions. It is tied to a specific revision of design data. Without locked files, “accurate” is undefined — any price is a placeholder.

PCB assembly pricing is not driven by board area alone. Two boards of the same size can differ by 40–80% in assembly cost when one uses 01005 passives and fine-pitch QFNs and the other uses 1206 and 1.27 mm pitch. File completeness lets the EMS model those differences before purchase order.

Mandatory Files for Quotation

Bill of Materials (BOM)

Provide a spreadsheet or ERP export with:

- Line item reference designators (match centroid and assembly drawing) - Manufacturer name and manufacturer part number (MPN) - Quantity per board - Description and package type (e.g., 0402, SOIC-8, QFN-32) - Approved alternates (AVL) or “no substitute” flags - DNI/DNP (do not install) lines clearly marked - Consigned vs turnkey supply intent per line if known

BOMs that list only generic descriptions (“10k resistor”) force the EMS to assume worst-case sourcing and package, which inflates quotes or causes rejection.

Gerber and Fabrication Data

Gerber RS-274X (or ODB++ / IPC-2581) defines copper, mask, paste, silk, drill, and outline. For assembly quotation, fabricators and EMS need at minimum:

- Copper layers, soldermask, paste stencil layers - Silkscreen (polarity marks) - Drill file and board outline - Fab notes: layer stack, finish (ENIG, HASL, etc.), thickness, impedance if controlled

If bare boards are consigned, still supply Gerbers so the EMS can verify pad geometry against your BOM packages and plan stencil aperture strategy.

Centroid (Pick-and-Place) File

Also called XY data, PNP, or machine file. Each SMT line needs coordinates, rotation, and side (top/bottom) per reference designator. Formats vary (CSV, ASCII); column headers should include `RefDes`, `X`, `Y`, `Rotation`, `Layer`.

Centroid must match the same BOM revision as the assembly drawing. Mismatched rotations are a top cause of wrong component orientation quotes turning into NPI delays.

Assembly Drawing

An assembly drawing (PDF or DWG) documents what automated files cannot:

- Polarity for diodes, LEDs, electrolytics, connectors - Keep-out zones and height restrictions - Fiducial requirements and panelization notes - Through-hole vs SMT process split - Special instructions: hand load, press-fit, staking, conformal coat areas - Label placement and serial number format

For LED driver and control boards, assembly drawings should call out thermal pad via requirements and any nodes that must not be coated.

Test Specification

Define expected test scope so labor and fixture costs are in the quote:

“Test TBD” often defaults to conservative pricing or excludes test entirely — then surprises appear at production release.

Common Gaps That Cause Requote

Lighting programs frequently combine custom magnetics, unique LED bin codes, and region-specific safety components. If those are not in the BOM with approved alternates, assembly quotes will not match production reality.

How to Prepare a Clean RFQ Package

Use a single folder or zip per revision, named consistently:

```text RFQ_ProjectName_RevC_2026-06-27/ BOM_RevC.xlsx Centroid_RevC.csv Gerber_RevC.zip AssemblyDrawing_RevC.pdf TestSpec_RevC.pdf Panelization_RevC.pdf (if applicable) README_RFQ.txt (quantity breaks, target lead time, incoterms) ```

In `README_RFQ.txt` or the email cover sheet, state:

- Annual and first-build quantities (e.g., 500 / 5k / 20k) - Turnkey vs consigned components - Required certifications (ISO, UL awareness, RoHS, REACH) - Target lead time and destination country - Whether NPI includes engineering support or production-only

Revision discipline matters more than file format perfection. Mihoray quotes against one locked Rev; change control after award follows your ECN process.

Example Submission Checklist

Use this table before sending any PCB assembly RFQ:

Completing 14 rows before submit typically cuts quote turnaround from a week to two or three business days on standard technology boards.

Cost and Schedule Impact of Incomplete Data

Every requote cycle adds calendar risk to line-fit programs and fixture pooling. Late discovery that FCT takes 8 minutes, not 2, can erase margin on a fixed-price assembly deal. Early file completeness lets EMS propose DFM feedback (pad size, test point access) while pricing is still negotiable.

For high-mix lighting electronics — multiple SKUs on shared lines — accurate files also determine whether programs can share stencils, share AOI recipes, and batch setup. That operational detail belongs in the quotation model, not as a post-award change order.

Mihoray Perspective on RFQ Quality

Mihoray runs in-house SMT for LED strip and neon flex control electronics. Quotes for driver and dimming PCBs assume complete centroid and assembly polarity data because LED and MOSFET footprints are orientation-critical. A clean RFQ package aligns procurement with reflow profiles, coating masks, and aging-test hooks defined in the test spec.

Conclusion

Accurate PCB assembly quotations are a documentation problem first and a negotiation problem second. Gerber, BOM, centroid, assembly drawing, and test specification together define process scope; omit any one and the price is a guess. Standardize your RFQ checklist, lock revisions, and treat file packages as part of product release — not as an afterthought to sourcing.

Q: Is BOM alone enough for an accurate PCB assembly quote? A:

No. A BOM without Gerber, centroid, and assembly data cannot define SMT complexity, panelization, or test labor. At minimum, pair the BOM with fabrication outputs and pick-and-place data for a credible quote.

Q: What file format is best for centroid data? A:

CSV with clear columns for reference designator, X, Y, rotation, and layer is widely accepted. Ensure units (mm vs mil) and origin match the Gerber data the EMS imports.

Q: Can we quote before the test spec is final? A:

You can request a quote excluding test, but the EMS should label assumptions explicitly. Final pricing requires cycle time, fixture needs, and pass/fail criteria — especially for FCT on lighting controllers.

Q: Do we need Gerbers if we consign bare PCBs? A:

Yes. Assembly engineering still validates pad stacks, mask openings, and stencil feasibility against your BOM packages.

Q: How many quantity breaks should we include? A:

Provide at least three: NPI/prototype, first production, and steady-state annual volume. Breaks drive stencil amortization, setup batching, and material MOQ economics.

About Mihoray

Mihoray is a professional LED strip and neon flex manufacturer based in China, operating 3 SMT production lines with reflow soldering, protective coating, and full QC for architectural and export lighting programs. In-house PCB assembly supports driver and control boards where complete Gerber, BOM, centroid, and test packages keep quotations aligned with real high-mix production.

Core Products: LED Strip · COB LED Strip · Neon Flex · Linear Lighting Manufacturing: SMT assembly · Reflow process control · Aging test · OEM / ODM lighting solutions

For PCB assembly quotations, contact Mihoray with a revision-locked RFQ folder and quantity breaks so engineering can respond with process-accurate pricing.