What Documents Are Required for SMT Contract Manufacturing?
SMT (Surface Mount Technology) outsourcing is a core collaboration model in the field of electronic manufacturing, involving multiple precise stages such as PCB assembly, soldering, and inspection. Providing complete and standardized documentation not only helps the manufacturer quickly understand project requirements and offer accurate quotations, but also prevents rework, delays, or even product failures caused by technical discrepancies. Whether it’s a small pilot production for a startup or large-scale manufacturing for an established company, preparing all necessary documents in advance is the key to ensuring an efficient SMT production partnership.
Below are the four essential categories of documentation required before initiating SMT cooperation—covering the full process from project setup to mass production:
1. Basic Cooperation and Product Information
This serves as the manufacturer’s “first-hand reference” to confirm the project scope and basic product attributes, helping avoid misunderstandings later in production.
Project Brief
Key contents: Project name, cooperation type (prototype / mass production / urgent order), expected order quantity (per batch or monthly demand), delivery schedule, and target price range (optional).
Notes: Specify whether PCB fabrication and component sourcing are included (turnkey / consignment). For turnkey projects, indicate preferred component brands (e.g., Yageo, Murata) or quality grades (industrial / consumer).
Basic Product Parameters
Key contents: Product application (e.g., medical device / consumer electronics / industrial control), operating environment (temperature / humidity / vibration resistance), and reliability standards (e.g., MTBF targets, lifespan requirements).
Notes: For special industries (e.g., medical or automotive electronics), specify corresponding compliance standards (e.g., ISO 13485, IATF 16949) so the manufacturer can match appropriate production and inspection conditions.
Contact and Communication Mechanism
Key contents: Names and contact details (phone / email) of technical and business contacts, as well as response time requirements for urgent issues.
Notes: Define the change control process (e.g., email confirmation + formal change order) to avoid confusion during production when design modifications occur.
2. Core Technical Documents
These are the “technical blueprints” of SMT manufacturing, directly determining assembly precision, soldering quality, and product reliability. They must be complete, standardized, and unambiguous.
PCB Documentation
Required files:
PCB Gerber files (including top/bottom layers, silkscreen, solder mask, and stencil layers; format: RS-274X recommended);
PCB Layout source files (optional; Altium, PADS, etc., for footprint and layout verification);
PCB specification sheet: indicate material (e.g., FR-4, Rogers), thickness (e.g., 1.6 mm), number of layers (single / double / multilayer), surface finish (HASL / ENIG / OSP), solder mask color, and silkscreen color.
Notes: If the PCB is to be sourced by the manufacturer, provide supplier information or purchase standards. If supplied by the customer, indicate the PCB batch number and storage conditions (to prevent moisture or oxidation).
Component Documentation
Required files:
BOM (Bill of Materials): Include part numbers, full component models (e.g., 0402 100 nF 16 V X7R), specifications (package size, capacitance/resistance, tolerance, voltage/current rating), quantity (per board + wastage rate, suggested 5–10%), and optional substitutes.
Datasheets (for key components): ICs, connectors, and special parts with pin definitions, soldering temperature, and storage conditions.
Component package library: For special packages (e.g., QFP, BGA, 01005), provide packaging files (IPC standard or 3D model) to ensure accurate placement.
Notes: BOMs should be in Excel format, marking “key components” (e.g., main ICs) separately for prioritized procurement. If components are supplied by the customer, provide part list, batch numbers, and packaging details (reel / tube / tray).
Assembly and Soldering Process Files
Required files:
Pick and Place File: CSV/TXT format with reference designators, X/Y coordinates, rotation angles, and package types, fully matching the Gerber and BOM.
Stencil File: If the stencil is to be produced by the manufacturer, provide Gerber data or specify aperture parameters (e.g., opening ratio, anti-bridging design).
Soldering process requirements: Define soldering method (reflow / wave), solder profile (e.g., Sn-Ag-Cu for lead-free), and cleaning process (no-clean / water-clean / solvent-clean).
Notes: For fine-pitch devices such as BGA or QFP, include “rework process requirements” (e.g., hot-air temperature, repair steps). If special soldering processes are needed (e.g., lead-free, low-temperature), specify them in advance.
3.Production and Testing Documents
These documents define the production process and inspection standards, helping the manufacturer quickly set up production lines and establish an appropriate quality control plan.
Production Process Requirements
Key contents: Whether first article inspection (FAI) is required; approval process for the first sample (e.g., mass production only after customer sign-off); in-process inspection frequency (e.g., once per hour); batch traceability requirements (e.g., linking component batch numbers with product batches).
Notes: For small-scale pilot runs, specify whether a “trial production report” is needed — including yield rate, defect analysis, and process improvement suggestions.
Testing Standards and Equipment Requirements
Required files:
Inspection checklist: Define mandatory tests such as AOI (Automated Optical Inspection), X-Ray (for BGA and hidden joints), ICT (In-Circuit Test), FCT (Functional Test), and aging tests.
Inspection standards: Include AOI defect judgment criteria (e.g., acceptable bridge, insufficient solder limits) and FCT functional test points (voltage / current / signal parameters).
Test fixture design: For FCT testing, provide test fixture design files (e.g., Gerber, test point coordinates) or request the manufacturer to design them (specify requirements clearly).
Notes: For functional testing, supply test programs (e.g., LabVIEW scripts) or test cases, outlining test steps and pass criteria (e.g., voltage range 3.3V ± 0.1V). If special industry tests are required (e.g., RoHS verification, ESD testing), inform the manufacturer in advance.
Packaging and Labeling Requirements
Key contents: Packaging method (e.g., anti-static bag, tray, carton), material specifications (anti-static grade), labeling details (model, batch number, production date, quality mark), and moisture/shock protection (e.g., desiccants, foam padding).
Notes: For export products, specify if packaging must meet international shipping standards (e.g., ISTA 1A) and whether customs codes or CE/FCC labels are required.
4.Quality and Compliance Documents
For specific industries or export products, relevant compliance documents are required to ensure adherence to industry standards and market entry regulations.
Quality System Documentation
Key contents: If the customer enforces a quality management system, provide their quality manual or specify which standards the manufacturer must follow (e.g., ISO 9001, IATF 16949). For automotive or medical products, include a “Quality Risk Assessment Report” (e.g., FMEA).
Compliance and Certification
Key contents: Industry certifications required (e.g., RoHS, REACH, UL, CE), and whether the manufacturer must assist in certification (e.g., providing samples or test data). If certifications already exist, provide copies for reference to align production processes.
Notes: For RoHS compliance, specify whether a “RoHS label” is required and if any restricted substances (e.g., lead, cadmium) must be controlled. For medical electronics, provide relevant “Medical Device Registration” information to ensure conformity with regulatory standards.
5.Common Issues and Documentation Pitfalls
Inconsistent data: The most common problems include mismatched component models between the BOM and placement file, or discrepancies between Gerber files and PCB specifications (e.g., board thickness). It’s recommended to cross-check the three core files — BOM, Gerber, and Pick & Place file — in advance.
Non-standard file formats: Using non-standard coordinate file formats or incomplete Gerber layers prevents direct use by the manufacturer. Always follow standard formats (Gerber RS-274X, coordinate CSV).
Missing key information: Omitting soldering temperature profiles or unclear testing standards can lead the manufacturer to follow default parameters, which might not meet your requirements. Verify each item against the “Technical Document Checklist” to avoid omissions.
Outdated documentation: For any design updates during cooperation, issue a formal “Change Notice” specifying the modification details and effective date to prevent production based on old revisions.
Conclusion
The essence of SMT outsourcing lies in precise alignment — manufacturers rely on documents to understand customer expectations, while customers rely on documents to guarantee product quality.
The checklist above covers every essential document, from basic information to compliance records. It is recommended to organize all materials by category and confirm their accuracy with the manufacturer’s technical team before project kickoff.
If you encounter difficulties during document preparation (e.g., BOM optimization or process documentation), consult your manufacturer’s technical support team. Early communication helps resolve potential issues and ensures smoother, more efficient SMT collaboration.
