China PCB Manufacturer & Assembler | Union Circuits

Rigid-flex PCBs combine rigid and flexible substrates to form versatile, three-dimensional circuits that enhance durability and design flexibility. These boards support stable component mounting and conform to complex shapes, making them ideal for aerospace, military, and other advanced applications with strict space and reliability requirements. Widely adopted across consumer electronics, medical technology, automotive systems, wearables, and IoT devices, rigid-flex PCBs allow for innovative, space-efficient designs. However, their sophisticated manufacturing processes and design complexities lead to higher production costs.

Multilayer PCB Manufacturing Processes

Step by step processes of producing multilayer PCBs, from DFM check to final inspection. 

1

Engineering

Check all the data provided to make sure the designing of the PCB is manufacturable, functional, reliable and cost effective. Raise questions if EQ, then issue MI for production.

2

Material Cutting

Cut the materials into panel according to MI. Including core, Prepreg, copper foils. Tooling holes need to be drilled at this step.

3

Pre-treatment

Prepare for the inner layer DFR (Dry Film Resist) lamination. To increase DFR adhesion, etch the surface of copper foils by jet-scrubber, buff brushing.

4

D/F Lamination

Laminate Dry Film on copper foils. D/F is used as a photosensitive material for photolithography.

5

D/F Exposure

Expose light onto the D/F. LDI (Laser Direct Imaging), which doesn’t require mask application, is an alternative solution.

6

DES

Same as the following. Developing the photoresist; Etching away unwanted copper; Stripping the remaining resist to reveal the circuit pattern.

7

Black Oxide

Etch the surface of copper surface to ensure adhesion of coppe and Prepreg.

8

Lay-up

Laminate copper foils, Prepreg and black oxided core to a single panel.

9

Hot Press

Heat the laminated layers under pressure in a vacuum melt Prepreg by heat to multilayer PCB formation. Other processes by the following will be the same as a double-sided PCB.

10

Drilling

Drill on board to form through holes.

11

Desmear

Remove the smear and resin residues left in the drilled holes, to ensure good electrical connectivity and improve the copper plating quality.

12

PTH

Electroless Copper Plating, a thin layer of copper is deposited on the hole walls through a chemical process, making them conductive.

13

Panel Plating

Electroplating, the thin copper layer is further reinforced with additional copper through electroplating, ensuring robust and reliable electrical connections.

14

Pre-treatment

Prepare for the next step, D/F lamination. To increase dry film adhesion, etch the surface of copper foils by jet-scrubber, buff brushing.
15

D/F Lamination

Laminate Dry Film on copper foils. D/F is used as a photosensitive material for photolithography.

16

D/F Exposure

Apply masks(films) on D/F and expose light onto the surface of copper foils. Currently, we use both ways, D/F and LDI (Laser Direct Imaging), which doesn’t require mask application.

17

DES

Developing the photoresist; Etching away unwanted copper; Stripping the remaining resist to reveal the circuit pattern.

18

O/L Inspection

Use AOI for outer layer inspection, to check for defects such as scratches, misalignments, and incomplete etching, ensuring the final board meets the required specification.

19

Pre-treatment

Clean and roughen the copper surface to increase the adhesion between the copper surface and solder resist

20

Solder Mask

Apply photo solder resist on one side then pre-baking, then printing solder resist on the other side, pre-baking, then exposure - develop - curing.

21

Silkscreen

Screen printing or injet printer printing the legend. 

22

Surface Finish

Apply surface treatment according to the specification, like Lead-free HASL, OSP, Immersion Gold/ Tin/Ag etc.

23

Profile

CNC routing, V-scoring, or punching, to de-panel the board from working panel. 

24

E-testing

Use Probe flying testing for prototype and small series, and E-test fixture for production orders.

25

FQA & FQC

Final Quality Control and Final Quality Assurance for the finished PCB.

26

Packing & Shipping

Packing according to the specification and deliver to wordwide customers.

High Frequency PCB Stackup

Multilayer PCB consists of core(s), Prepreg and copper foils, base on different thicknesses the detailed stackup can be vary. Leave the stackup to us if you don’t have a specific requirement. Below is a 6 layer PCB basic structure for example.

Top Brand Suppliers We Use

Explore our major suppliers offering top-quality products. We use top brand laminate and solder mask suppliers to guarantee quality from the source.

Technical Specifications

Explore the technical specifications of our top-quality PCBs. Discover how we ensure reliability and performance with detailed specs.

No. Item Standard Advanced
1 Layer Count 2 /
2 Material Vendor ShengYi, KB, NanYa, ITEQ, isola Panasonic, Rogers, Nelco, Arlon
3 Material Type Normal FR-4, FR-4(Tg150), FR-4(Tg170), Halogen-free, CAF Resistance Polyimide, Aluminum/ Copper-base
4 Finished Thickness 0.2~5.0mm(0.005~0.197”) 0.2~6.5mm(0.005~0.256”)
5 Finished Size(min) 50 x 50mm(2 x 2") 30 x 50mm(1.2 x 2")
6 Finished Size(max) 610 x 1000mm(24" x 40" ) 610 x 1500mm(24" x 60" )
7 Trace Width/Space 0.10/0.10mm(4/4mils) 0.05/0.05mm(2/2mils)
8 Mechanical Drilling 0.2~6.5mm(0.008"~0.256") 0.15~6.5mm(0.006"~0.256")
9 Laser Drilling / /
10 Aspect Ratio 12:1 20:1
11 Copper Weight 0.5~12 OZ 20 OZ(max)
12 Solder Mask Color Glossy/Matt Green, white, black, red, blue Yellow, pink, purple
13 Silkscreen Color White, black /
14 V-scoring 30° 20°/ 45°/ 60°
15 Outline Tolerance ±0.006”(0.15mm) ±0.004”(0.10mm)
16 Surface Finishes Lead-free HASL, Immersion Gold/ Tin/ Silver, Plating hard Gold, OSP ENEPIG

State-Of-The-Art Equipment

Our cutting-edge technology plus morden equipments to ensures unparalleled performance and reliability for all your needs.

Related IPC Standards

IPC standards provide comprehensive guidelines and requirements to ensure the quality, reliability, and performance of PCBs used in various electronic applications. These standards cover a wide range of aspects, including design, materials, manufacturing processes, testing, and quality assurance.

PCB Design
IPC-2221C Generic Standard on Printed Board Design(Download a slash sheet). Published date: 12/01/2023.
IPC-2222B Sectional Design Standard for Rigid Organic Printed Boards(Download a slash sheet). Published date: 10/01/2020.
IPC-2223E Sectional Design Standard for Flexible/Rigid-Flexible Printed Boards(Download a slash sheet). Published date: 01/01/2020.
IPC-2226A Sectional Design Standard for High Density Interconnect (HDI) Printed Boards(Download a slash sheet). Published date: 09/01/2017.
IPC-2228 Sectional Design Standard for High Frequency (RF/Microwave) Printed Boards(Download a slash sheet). Published date: 10/01/2022.
IPC-2141A Design Guide for High-Speed Controlled Impedance Circuit Boards(Download a slash sheet). Published date: 03/01/2004.
IPC-2315 Design Guide for High Density Interconnects & Microvias(Download a slash sheet). Published date: 06/01/2000.
IPC-2316 Design Guide for Embedded Passive Device Printed Boards.(Download a slash sheet). Published date: 03/01/2007.
PCB Materials
IPC-4562B Specification for Metal Base Copper Clad Laminates for Printed Boards(Download a slash sheet). Published date: 02/05/2013.
IPC-4563 Resin Coated Copper Foil for Printed Boards Guideline(Download a slash sheet). Published date: 02/11/2008.
IPC-4101E Specification for Base Materials for Rigid and Multilayer Printed Boards(Download a slash sheet). Published date: 03/01/2017.
IPC-4103B Specification for Base Materials for High Speed/High Frequency Applications(Download a slash sheet). Published date: 11/01/2017.
IPC-4202C Specification for Flexible Base Dielectrics for use in Flexible Printed Boards(Download a slash sheet). Published: 01/01/2022.
IPC-4203B Cover and Bonding Material for Flexible Printed Circuitry(Download a slash sheet). Published: 03/01/2018.
IPC-4204B Flexible Metal-Clad Dielectrics for Use in Fabrication of Flexible Printed Boards(Download a slash sheet). Published: 08/01/2018.
IPC-FC-234A Pressure Sensitive Adhesive (PSA) Assembly Guidelines for Flexible, Rigid or Rigid-Flex Printed Boards(Download a slash sheet). Published: 12/23/2014.
Surface Finish
IPC-4552B Specification for Electroless Nickel/Immersion Gold (ENIG) Plating for Printed Boards(Download a slash sheet). Published date: 05/01/2021.
IPC-4553A Specification for Immersion Silver Plating for Printed Boards(Download a slash sheet). Published date: 06/16/2009.
IPC-4554 Specification for Immersion Tin Plating for Printed Circuit Boards(Download a slash sheet). Published date: 09/01/2013.
IPC-4555 Performance Specification for High Temperature Organic Solderability Preservatives (OSP) for Printed Boards(Download a slash sheet). Published date: 04/01/2022.
IPC-4556 Specification for Electroless Nickel/Electroless Palladium/Immersion Gold (ENEPIG) Plating for Printed Circuit Boards(Download a slash sheet). Published date: 02/05/2013.
ASTM-B-488 Electrodeposited Coatings of Gold for Engineering Uses.
MIL-G-45204 Electrodeposited Gold Plating on Metallic Surfaces.
Performance
IPC-SM-840E Qualification and Performance Specification of Permanent Solder Mask and Flexible Cover Materials(Download a slash sheet). Published date: 12/22/2010.
IPC-A-600K Acceptability of Printed Boards(Download a slash sheet). Published 07/01/2020.
IPC-6012F Qualification and Performance Specification for Rigid Printed Boards(Download a slash sheet). Published date: 09/28/2023.
IPC-6013E Qualification and Performance Specification for Flexible/Rigid-Flexible Printed Boards(Download a slash sheet). Published date: 09/01/2021.
IPC-6018D Qualification and Performance Specification for High Frequency (Microwave) Printed Boards(Download a slash sheet). Published date: 02/01/2022.
Testing
IPC-TM-650 Test Methods Manual(Download a slash sheet). Published date: 06/06/2012.
IPC J-STD-003D Solderability Tests for Printed Boards(Download a slash sheet). Published date: 01/01/2023.
IPC-9252B Requirements for Electrical Testing of Unpopulated Printed Boards(Download a slash sheet). Published date: 09/01/2016.

Value-Added Services

From quickturn prototype PCB manufacturing to Assemblied PCB, we have got you covered.

Free DFM Check

PCB Layout optimization, EQ confirmation, to improve production yield and cost reduction.

Quickturn PCB Manufacturing

As quick as 24 Hours for Prototype PCB manufacturing, small series as fast as 5~7 days.

Prototype PCB Manufacturing

No MOQ limit, PCB Prototype as less as one single piece. Even one piece we care.

HMLV Orders

Focus on High-Mix-Low-Volume PCB Manufacturing for more than 10 years.

Components Sourcing

Hard-to-find components sourcing; NRND components substitue; global network.

Quick turn PCB Assembly

24 Hours PCB Assembly upon all components secured. Medium batch as fast as 3~5 days.

Prototype PCB Assembly

Focus on High-Mix-Low-Volume PCB Manufacturing for more than 10 years.

Turnkey PCB Assembly

From PCB Manufacturing, Parts Procurement to PCB Assembly, we have got you covered.

Frequently Asked Questions

Explore our FAQ section for clear, concise answers to your most common questions. Find the information you need quickly and easily. .

We always follow customer specification to choose the right material. From our record, CEM-1 is the most commonly used.

Single-sided PCB is the simplest PCB, it is cost-Effective, simplicity and easier to repair and troubleshoot due to the single layer of circuitry.

Single-sided PCB is only suitable for simple circuits with low component density, it's not suitable for high-speed or high-frequency applications.

Yes, but the design must consider the current-carrying capacity of the traces and ensure adequate heat dissipation. Thicker copper layers and wider traces are often used for high-current applications.

Single-sided PCBs are commonly used in consumer electronics, power supplies, industrial equipment, toys, and basic audio equipment etc.

We prefer Gerber RX-274X format, .brd, . .PcbDoc, .tgz acceptable.

For new clients, our standard payment terms are 30% advance payment and 70% before shipment. We accept various payment methods, including wire transfer and PayPal.

Single-sided PCB is always in mass production, base on the volume it usually takes 5 wds to weeks.

Single-sided PCB is easy, but we also run necessary visual Inspection, E-testings etc to ensure the quality.

We can ship to anywhere as long as there is local DHL/FedEx/UPS service there.

Get In Touch

Feel free to contact us if you have any questions, even though you have no needs at this moment.

Scroll to Top