PCB assembly · Shenzhen, China
PCB Assembly Services: SMT, BGA and Through-Hole Builds from 1 Piece
Queen EMS assembles printed circuit boards in our own factory in Shenzhen, China, for engineering teams in North America, Europe and Asia. We place parts from 01005 passives to 0.3 mm pitch BGAs, solder through-hole and mixed-technology boards, and inspect every build to the IPC-A-610 class on your order. You choose whether we source the components or you supply them.
Buying PCBA overseas
What Usually Goes Wrong with an Offshore PCB Assembly Order
Most PCBA failures that show up in the field start before the board reaches the line: a part substituted without approval, a generic part number that matches two different pinouts, or a hidden solder joint that nobody inspected.
- Parts are matched by full manufacturer part number. When a BOM line is ambiguous, we ask instead of choosing for you.
- Substitutions need your written approval. Your quote lists any alternates we propose.
- Hidden joints are checked. SMT builds go through 3D AOI, and BGA, QFN and other bottom-terminated parts are X-rayed.
- One example from our line: a BOM listed only “2N2222”. Incoming stock mixed two TO-92 versions with different pin orders, and the second batch failed functional test. Since then, incoming inspection checks every part’s full MPN and pinout against the CAD data.
Assembly services
PCB Assembly Services
Each service has its own page with detailed capabilities, design rules and quote requirements.
SMT Assembly
Surface-mount placement from 01005 passives to fine-pitch QFN and BGA, with 3D AOI.
View service →BGA Assembly
BGA and bottom-terminated parts down to 0.3 mm pitch, with X-ray of hidden joints.
View service →Through-Hole Assembly
Leaded parts, connectors and power components, by wave or selective soldering.
View service →Mixed Assembly
SMT and through-hole on the same board, built in one flow.
View service →Quick Turn Assembly
Prototype and engineering builds from 1 piece when files and parts are ready.
View service →IC Programming & Testing
Firmware loaded and functions checked before boards ship.
View service →SMT Stencil
Laser-cut stencils for your own line or for builds we assemble.
View service →Free DFM Check
An engineer reviews your Gerber and BOM before you order.
View service →Which Assembly Service Fits Your Board?
| If your board has… | Start with |
|---|---|
| Only surface-mount parts | SMT assembly |
| BGAs, QFNs or LGAs | BGA assembly |
| Connectors, transformers or other leaded parts only | Through-hole assembly |
| Both SMT and leaded parts | Mixed assembly |
| A deadline for first samples | Quick turn assembly |
| Firmware to load before shipping | IC programming & testing |
Capability index
PCB Assembly Capabilities
| Parameter | Capability | Why it matters |
|---|---|---|
| Component size | 01005 up to 100 mm parts | Covers dense consumer boards through large power and connector parts. |
| BGA pitch | Down to 0.3 mm | Fine-pitch processors, memory and modules. See BGA assembly. |
| Placement speed | Up to 90,000 CPH | Keeps production runs on schedule once parts are kitted. |
| Assembly types | SMT, through-hole, mixed technology | See mixed assembly for boards with both. |
| Through-hole soldering | Wave and selective soldering | Selective soldering protects nearby SMT parts on mixed boards. |
| Conformal coating | Applied to your drawing | Protects boards against moisture and contamination; your drawing defines coated and keep-out areas. |
| Inspection & test | 3D AOI, X-ray, flying probe, ICT, FCT | Choose with our inspection method selector. |
| Workmanship standard | IPC-A-610, Class 2 or Class 3 | Defines the solder joint and placement criteria your boards are inspected to. |
| Parts | Full turnkey, partial turnkey or consigned | See how parts are handled below. |
| Order quantity | From 1 piece | Prototypes and engineering builds without a minimum. |
| Bare boards | Made in our own factory | Fabrication and assembly run on one schedule. See PCB manufacturing. |
Not sure your board is within our limits? Run the capability quick-check or send your files for a free DFM check.
Build flow
From BOM to Tested Board
BOM and file review
Engineers check your BOM, Gerber and centroid files, flag ambiguous part numbers and confirm any alternates with you.
Parts
We source the parts (turnkey) or receive your kit (consigned). Incoming parts are checked by full MPN.
Paste and placement
Solder paste is printed through a laser-cut stencil and parts are placed by machine.
Reflow and through-hole
SMT parts are reflowed; leaded parts are wave or selectively soldered after.
Inspection and test
3D AOI on every SMT build, X-ray for hidden joints, then flying probe, ICT or functional test as specified on your order.
Final inspection
Boards are inspected to the IPC-A-610 class on your order, coated if specified, then packed for shipping.
Which Test Catches What
| Check | What it finds | When we use it |
|---|---|---|
| 3D AOI | Missing, shifted or reversed parts; solder bridges | Every SMT build |
| X-ray | Voids and bridges under BGA, QFN and LGA parts | Boards with hidden-joint parts |
| Flying probe | Opens, shorts and wrong values, without a fixture | Prototypes and low volume |
| ICT | The same faults, faster, with a test fixture | Repeat and higher-volume builds |
| Functional test | Whether the board works as designed | When you provide a test procedure or fixture |
Component sourcing
Turnkey or Consigned: How Parts Are Handled
You decide who buys the parts. For consigned and partial kits, send parts in labelled reels, trays or tubes, with a little spare for machine loss on small passives. We confirm exact quantities in your quote.
- Full turnkeyWe source every part on your BOM. Best when you want one quote and one purchase order.
- Partial turnkeyYou supply some parts, for example a controlled IC; we source the rest. Best when some parts are allocated or already in your stock.
- ConsignedYou supply all parts as a kit. Best when you already hold the inventory.
Quality
Quality System and Workmanship Standards
Every assembly is inspected to the IPC-A-610 class on your order. Bare boards are 100% electrically tested before assembly.
| Class 2 | Class 3 | |
|---|---|---|
| Typical products | Industrial, telecom, consumer electronics | Medical, aerospace and other high-reliability products |
| What changes | Standard solder fillet and placement criteria | Tighter fillet, wetting and placement criteria |
Industries & projects
Industries and Assembly Projects
Ordering
Ordering: Files, Quotes and Lead Times
Gerber or ODB++, BOM with full manufacturer part numbers, centroid file and assembly drawing. Add test requirements if you need ICT or functional test.
PCBA quotes within 24 hours of receiving complete files.
Typically 5–8 working days once all components are in stock. For turnkey orders, part availability sets the start date; your quote confirms the ship date.
From 1 piece.
Full turnkey, partial turnkey or consigned.
Made in our own factory. See PCB manufacturing.
Tools & guides
Assembly Planning Tools and Guides
- SMD sizes explained: surface-mount component dimensions
- SMT vs SMD vs THT: choosing an assembly technology
- Engineering change notices (ECN) for PCB and PCBA
- QFN package: types, footprints and soldering
- Reflow soldering profile optimization for SMT
- How to specify PCBA reliability testing
- How to audit a PCB assembly factory
- HS codes for PCB and PCBA imports
FAQ
PCB Assembly FAQ
What is the difference between PCB and PCBA?
A PCB is the bare board. A PCBA is the same board with components soldered on, inspected and tested.
Do you source components, or do I supply them?
Either. We can source every part (full turnkey), source the rest while you supply some (partial turnkey), or build from your kit (consigned).
How long does PCB assembly take?
Typically 5–8 working days once all components are in stock. For turnkey orders, part availability decides the start date, and your quote confirms the ship date.
What is the smallest part and finest BGA pitch you can place?
01005 passives and BGAs down to 0.3 mm pitch. See BGA assembly.
Can you build to IPC-A-610 Class 3?
Yes. Assemblies are built and inspected to Class 2 or Class 3, as specified on your order.
Do you offer selective soldering and conformal coating?
Yes. Selective soldering is used for through-hole parts on mixed boards, and conformal coating can be applied when your drawing specifies the coating and keep-out areas.
Is there a minimum order quantity?
No. Assembly orders start from 1 piece.
What files do I need for a PCBA quote?
Gerber or ODB++, a BOM with full manufacturer part numbers, a centroid (pick-and-place) file and an assembly drawing.
Get a PCB Assembly Quote
Send your BOM and Gerber files. An engineer reviews them and returns a PCBA quote within 24 hours.