Multilayer PCB consists three or more copper layers separated by insulating dielectric materials like prepreg—a glass-reinforced epoxy, are essential in modern electronics. Typically structured in even-numbered layers (4, 6, 8, etc.), these PCBs integrate various signal, power, and ground planes to efficiently distribute power. Using a high-pressure, high-heat lamination process, these layers are bonded to form a unified board. Connections across layers are made via plated through-holes (PTH) and vias, closely resembling the manufacturing process of double-sided PCBs after lamination.

Multilayer PCB Manufacturing processes

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



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.


CCL Cutting

Cut the sheet CCL(Copper-Clad Laminate) into panels according to MI. Cutting - curium - debur.



Drill on board to form through holes.



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



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


Panel Plating

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



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

D/F Lamination

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


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.



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


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.



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


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.



Screen printing or injet printer printing the legend. 


Surface Finish

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



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



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



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


Packing & Shipping

Packing according to the specification and deliver to wordwide customers.

Multilayer PCB Stackup

Basic stackup structure of multilayer PCB, base on different material types, core thickness, copper/ solder mask thicknesses, the detailed stackup can be vary.

High Quality Multilayer PCB Manufacturing

Union Circuits employs cutting-edge manufacturing processes for its multilayer PCBs. This involves advanced techniques in material selection, lamination, exposure, etching, plating etc, ensuring that each PCB meets the highest standards of quality and reliability.

State-Of-The-Art Equipment

Extensive Services We Offer

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.

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