PCB MANUFACTURER IN CHINA
PCB Assembly in China: SMT, THT & Turnkey PCBA Services
PCB assembly brings the bare board, electronic components, placement data and test requirements together into a controlled build. Use PCB Manufacturer in China to prepare inquiries for SMT, through-hole and mixed-technology assembly, with turnkey, consigned or shared component sourcing defined around your project.
A complete assembly quotation depends on more than the number of components. It needs a consistent board revision, an unambiguous bill of materials, placement information, sourcing permissions and an agreed definition of a finished, accepted assembly. The capability reference describes the technical scope available for inquiry; individual packages and processes require review against the actual design.
Choose who supplies the PCB and components
Define the supply model before asking for a price. “Turnkey” and “consigned” are useful shorthand, but an order still needs a list of responsibilities. Identify who purchases the bare boards, who procures each component, who approves alternatives and how remaining material will be handled after the build.
| Assembly model | Typical inquiry scope | Decision to settle first |
|---|---|---|
| Turnkey | Request fabrication, component procurement, assembly and the specified testing together. | Approved parts, permitted sourcing channels and substitution approval. |
| Consigned | Supply the agreed boards or components for the assembly operation. | Kit quantities, packaging, receipt checks and shortage handling. |
| Partial turnkey | Supply selected items while requesting procurement of the remaining BOM. | A line-by-line ownership list with delivery dates. |
| Assembly with additional operations | Include programming, coating, mechanical work or product-specific testing. | Work instructions, fixtures, approved materials and acceptance limits. |
A shared sourcing model is often useful when you already hold a critical part. Make the ownership split explicit in the BOM instead of describing it in a separate conversation. Each line should show whether the item is customer supplied, to be purchased, or intentionally not fitted.
SMT, through-hole and mixed assembly
Surface-mount assembly places components on board pads and joins them through the specified soldering process. Through-hole assembly addresses components with leads inserted through board holes. A mixed assembly combines these requirements, so the quotation should cover both operations and the inspection expected after each relevant stage.
Call attention to the packages that need special review: very small passives, fine-pitch devices, hidden joints, tall components and mechanically sensitive connectors. The SMT process reference discusses how component packages influence printing, placement and inspection. Use the manufacturer package drawing when confirming the exact part and land pattern.
Identify parts with restrictions on cleaning, solder exposure, handling or installation sequence. Describe the requirement in the assembly drawing and point to the component manufacturer’s instructions. If a connector or mechanical part must be installed after another operation, say so explicitly. Assembly sequence should be an agreed instruction, not a discovery made during the first build.
Build a BOM that can be sourced without guessing
A purchasing-ready BOM identifies the intended component precisely and connects it to the design. Include reference designators, quantity per board, manufacturer, complete manufacturer part number, a clear description and the fitted status for the requested variant. Supplier stock numbers may be useful, but they should not replace the manufacturer’s identity.
Give alternatives their own approval status. “Equivalent allowed” can mean different things to engineering and purchasing; specify which attributes must remain unchanged and which alternatives are already approved. For example, a passive part may have requirements beyond its nominal value, including package, tolerance, voltage rating or temperature characteristics. The person approving a substitute should have the relevant design requirements available.
When the product has several variants, provide either a separate controlled BOM for each build or an unmistakable variant matrix. Mark do-not-populate positions consistently. Confirm that quantities match the selected variant and that a component removed from the BOM is also handled correctly in the assembly drawing and test instructions.
Align placement data with the board revision
Placement data and assembly drawings should describe the same released design as the fabrication package and BOM. Identify the origin, units, board side and rotation convention used by the export. Supply a drawing that makes polarity, pin-one orientation and unusual mechanical placement easy to verify.
Use a single release identifier across the package. A BOM from one revision and placement file from another can appear plausible while describing different builds. Before sending the inquiry, compare reference designators and fitted quantities across the files. Resolve any unexplained mismatch, then include a short manifest listing the released documents.
Do not assume that a component illustration communicates its electrical orientation. Identify polarity-sensitive parts in the drawing, and include package information where markings are ambiguous. For connectors, describe the mating direction and any critical height or edge alignment. These details matter when the assembled board must fit into an enclosure that is not available at the assembly site.
Prepare a customer-supplied kit
A consigned build needs a kit plan as well as a BOM. Ask the assembler to confirm the supplied quantity required for each part, including any process allowance. Agree that allowance rather than applying one percentage to every component. The necessary handling plan may differ between a full reel, cut tape, loose parts and a tray of large devices.
Label every supplied item with a traceable identifier that maps to the BOM, and keep the original packaging information available. State whether any parts have been opened, repacked, recovered or previously processed. Request confirmation of how the kit will be checked on receipt and how discrepancies will be reported before the build starts.
Agree the disposition of unused material in advance. Your order should say whether remaining components will be returned, stored for a defined future build or handled under another written arrangement. For expensive or scarce parts, request a material reconciliation that connects received, consumed, rejected and remaining quantities to the relevant line item.
Define inspection and testing as separate deliverables
A test plan should identify what is checked, when it is checked, which limits apply and what record is delivered. The reference scope includes solder paste inspection, automated optical inspection, X-ray, in-circuit test and functional test. Availability does not mean that every method is automatically included in every quotation.
- Process inspection: identify the inspection stages needed for the assembly and the records you expect.
- Hidden-joint review: mark the packages or locations that need a defined inspection approach.
- Electrical testing: specify the accessible test points, fixture needs and fault coverage objectives.
- Functional testing: provide the procedure, firmware, loads, interfaces and pass/fail limits.
- Programming: identify the approved image, version, programming interface and verification step.
For functional testing, a statement such as “board must work” is too broad to price or execute consistently. Write the power-up sequence, input conditions, measurements and acceptance limits. Define what happens if a board fails, whether rework is permitted, and which result must be retained against the assembly serial number. The quality and evidence guide provides a practical order checklist.
Use the first build to close open instructions
A prototype assembly can help you validate the manufacturing package as well as the product. Decide what must be reviewed before additional boards are assembled: component orientation, mechanical fit, programming, functional behavior or a specific inspection result. Put those hold points in the order so production and engineering share the same expectations.
Record corrections against the source documents. If an engineer resolves an orientation question during the build, update the controlled drawing before the next order. If a component substitution is accepted, update the approved BOM rather than relying on a message from the previous build. This prevents the same question returning when another person manages the reorder.
When moving to a larger quantity, confirm which fixtures, programs and setup data can be reused and which need review. A successful prototype is useful evidence, but the repeat order should still name the exact revision, quantity, test scope and documentation required.
Ask for a quotation with visible assumptions
A clear assembly quotation separates the board, components, setup, assembly, test, additional operations and delivery scope sufficiently for you to compare alternatives. Ask whether component availability has been checked and how long pricing remains valid. Identify any line items awaiting engineering approval or a sourcing decision.
Lead time should be tied to explicit prerequisites. The release of the final files, receipt of customer material, approval of alternatives and readiness of test fixtures may happen at different times. Request a schedule that identifies those dependencies and separates manufacturing completion from shipment and arrival planning.
For a cost review, ask which changes would alter the manufacturing effort without compromising the product requirements. Examples to investigate include a different panel arrangement, a clearer variant strategy or using an already approved component alternative. Evaluate each proposal against the product specification; a lower quoted price alone does not establish that the revised build is suitable.
Send one complete assembly inquiry
Prepare the fabrication package, BOM, placement file, assembly drawing, variant definition and requested quantity together. Add the intended sourcing model, test scope, programming requirements and delivery destination. If an item is still being developed, identify it as an open requirement and state when the final instruction will be available.
Use the RFQ checklist to assemble the package, the PCB manufacturing guide for bare-board requirements, and the FAQ for common purchasing questions. Send project questions to Tina@4PCBA.com or Get a Quote with the released documents.