How to Source PCB Assemblies
PCB assembly RFQ checklist: fab files and drawing, BOM with approved alternates, centroid data, IPC class, turnkey or consigned parts, test and coating.
50 shops tagged PCB assembly among 841 electronics manufacturing companies in the Noramark directory
A PCB assembly quote is really three quotes: the bare board, the components, and the assembly labor and test. The board and the labor are predictable from good files. The components are not: availability, lead time and price change week to week, and one part with no stock can hold the whole order. Most quoting delays come from an incomplete bill of materials.
A good PCB assembly RFQ sends a complete data package (fabrication files and drawing, a BOM with manufacturer part numbers and approved alternates, pick-and-place data and an assembly drawing), states the IPC acceptability class, says whether the assembler buys the parts (turnkey) or you supply them (consigned), and defines the test. Ask for prices at two or three quantities: stencil, programming and setup costs spread quickly, and component price breaks do too.
RFQ checklist
19 things to settle on the drawing or in the request before you ask for PCB assembly quotes. Print it and tick it off against the print, or copy it into the RFQ.
Bare board
Fabrication data: Gerber (RS-274X) or ODB++ or IPC-2581, drill files, and a fabrication drawing
The fabrication drawing carries what the image files do not: stackup, material, thickness, finish, class and tolerances.
Layer count, board thickness, copper weights and stackup, with impedance targets if controlled
Controlled impedance needs a defined stackup and test coupons. The fabricator may propose its own standard stackup to meet the targets.
Laminate: standard FR-4 with a minimum Tg, or a high-frequency or halogen-free material
Lead-free soldering runs hotter. Boards with several reflow passes or heavy copper often need a higher-Tg laminate.
Surface finish: lead-free HASL, ENIG, immersion silver, OSP or ENEPIG
Fine-pitch and BGA parts want a flat finish such as ENIG. HASL is the cheapest but uneven.
Fabrication class: IPC-6012 Class 2 or Class 3
Class 3 tightens plating, annular ring and inspection requirements and costs more.
Panelization and depaneling method, or leave it to the assembler
The assembler panelizes for its own line. A fixed customer panel must still suit its equipment.
Components
BOM with reference designators, quantities, manufacturer names and manufacturer part numbers, plus approved alternates
Without part numbers the assembler has to guess, and without alternates one out-of-stock part stops the build.
Turnkey, consigned or partial turnkey: who buys which parts
Turnkey adds purchasing markup and shortage risk to the assembler's price but saves you logistics. Consigned parts must arrive complete, labeled and with extras for machine attrition.
Do-not-populate parts and build variants
Variants change placement programs and inspection; the assembler needs a BOM per variant.
Lead-free (RoHS) or tin-lead process, and any REACH or conflict-minerals declarations
A tin-lead build needs a line that runs it, and declarations take component data the assembler must collect.
Moisture-sensitive parts, and whether components must come only from authorized distributors
Requiring authorized channels limits broker buys and reduces counterfeit risk, which matters most in aerospace, medical and defense.
Assembly and test
Pick-and-place (centroid) file, and an assembly drawing with polarity and orientation marks
The centroid file programs the placement machines; the drawing settles polarity and anything the file does not show.
Workmanship standard: IPC-A-610 Class 2 or Class 3, and J-STD-001 if required
The class sets solder joint acceptance criteria and inspection effort.
Through-hole and mechanical assembly: wave, selective or hand soldering, connectors, hardware and heat sinks
Through-hole and mechanical steps are often manual and are priced as labor.
Inspection: AOI, X-ray for BGA and bottom-terminated parts, first article
X-ray is the only way to see joints under a BGA, and it adds time per board or per sample.
Testing and programming: flying probe or ICT, functional test with your fixture and procedure, firmware loading
Functional test needs a fixture and a procedure from you. Flying probe needs no fixture but is slower per board.
Conformal coating: type (acrylic, silicone, urethane), areas to coat and to mask, and cleaning before coating
Masking connectors and test points is handwork, and flux residue may need cleaning before coating adheres.
Quantity and delivery
Quantities at two or three levels, and whether a prototype build comes first
Stencils, programming and first article are one-time costs that spread fast with quantity.
Packaging: ESD bags or trays, labels, serialization
Serialization and custom labels add a step per board.
What to send with the RFQ
- Gerber or ODB++ files, drill files and the fabrication drawing.
- A BOM spreadsheet with manufacturer part numbers, reference designators and alternates.
- The centroid file and the assembly drawing.
- Test requirements, and any test fixture, procedure or firmware.
- Quantities, turnkey or consigned, and the target date.
Lead times
| Prototype or first parts | Quick-turn assembly: about 5-15 business days when parts are in stock. Bare boards alone can be made in a few days at a premium. |
|---|---|
| Production or repeat orders | About 3-6 weeks typical. Scarce components can stretch this to months, so check the BOM for availability before committing to a date. |
Typical of U.S. job shops, from order or approved drawing to shipment; confirm with the shop for your part.
What drives the cost
- Components: usually the largest share of a turnkey quote, and the most volatile.
- Placement count, especially fine-pitch, BGA and through-hole parts.
- Board complexity: layer count, HDI features, impedance control and Class 3.
- Setup: stencils, programming and first article, spread over the quantity.
- Test fixtures, test programming and test time.
- Conformal coating with masking, and hand assembly.
Common mistakes
- A BOM without manufacturer part numbers, or with obsolete parts.
- No approved alternates for passives and common parts.
- No fabrication drawing, so stackup, finish and class are guessed.
- Consigned parts arriving short, loose or without attrition extras.
- Missing polarity marks on the silkscreen and the assembly drawing.
Questions to ask the shop
- Can you review our BOM for availability and lifecycle before quoting?
- Do you fabricate boards in-house or buy them, and from where?
- What inspection and test equipment do you have: AOI, X-ray, flying probe, ICT?
- Are your operators trained to IPC-A-610 and J-STD-001, and do you hold ISO 9001, AS9100 or ISO 13485 if we need it?
- How do you prevent counterfeit components?
Typical materials
Charts and calculators
Frequently asked questions
- Turnkey or consigned PCB assembly?
- Turnkey is simpler: the assembler buys every part and owns the shortages. Consigned saves the purchasing markup and suits parts you already stock or must control, but you carry the logistics and must send extras for machine attrition. Many builds are partial turnkey: you supply the expensive or scarce parts and the assembler buys the rest.
- IPC Class 2 or Class 3?
- Class 2 is for dedicated-service electronics where continued performance is wanted but interruption is not critical: most industrial and commercial products. Class 3 is for high-reliability products that must work on demand, such as life-support medical, aerospace and military electronics. Class 3 costs more in fabrication, assembly and inspection.
- What files does a PCB assembler need?
- Gerber or ODB++ files with drill data, a fabrication drawing, a BOM with manufacturer part numbers, a centroid (pick-and-place) file and an assembly drawing, plus test requirements and any programming files. Most PCB design tools export the whole package in one step.
Build the RFQ: attach the print and this checklist
Attach the drawing (PDF) and the model (STEP), and put your answers to the checklist in the description. A Noramark sourcing specialist matches the request with U.S. shops that make PCB assemblies and contacts you within 1 business day.
