How a printed circuit board is made: the main steps
From copper-clad laminate to the tested board: what happens in each step and where multilayer and aluminium boards differ.
Overview
A printed circuit board starts as a sheet of laminate (FR4 with copper foil on one or both sides) and is turned into a finished board by a sequence of mechanical, chemical and optical steps. Knowing the sequence helps you understand lead times, design limits and why some files cause questions.
The steps for a double-sided board
- Cutting and preparation. The laminate is cut to panel size and cleaned.
- Drilling. Holes for components, vias and mounting are drilled according to the drill file.
- Hole metallisation. A thin layer of copper is deposited in the holes and built up by electroplating, so that the holes connect both sides.
- Imaging. A photosensitive film (photoresist) is applied, exposed to UV light through the circuit pattern and developed.
- Etching. The copper that is not protected is etched away; the remaining resist is stripped and the traces are left.
- Solder mask. The coloured protective layer is applied and exposed so that pads and holes stay open.
- Silkscreen. The legend (designators, polarity marks) is printed.
- Surface finish. Exposed copper receives its finish; at PCB-ELECTRA this is lead-free HASL.
- Outline. Boards are routed out of the panel or scored for V-cut.
- Inspection and test. A 100% electrical test (short circuit and open circuit, flying probe) and AOI check every board (AOI also covers the copper pattern before the solder mask), followed by a final visual and dimensional check and packing.
What differs for multilayer boards
The inner layers are made first: each core is imaged and etched, then the cores are stacked with prepreg and pressed under heat and pressure into one board. Only then are the holes drilled and metallised, and the outer layers are processed as above. The lamination steps and the need to keep the layers aligned make multilayer boards slower to produce. See the stack-up guide and the pages for 4-layer and 6-layer boards.
What differs for aluminium (IMS) boards
An aluminium board starts from a laminate of copper foil, a thin thermal dielectric and an aluminium base. There is normally one copper layer and no plated holes, drilling is limited to mounting holes, the outline is routed rather than scored, and a dielectric withstand test is added. See aluminium PCB for LED and the IMS aluminium PCB page.
Lead time at PCB-ELECTRA
Standard production is 9 working days for 1- and 2-layer and aluminium boards; multilayer boards take longer, and urgent production is faster. The price calculator shows the delivery date of your configuration. How the checks work is described in electrical test and AOI.
Frequently asked questions
How long does it take to manufacture a PCB?
At PCB-ELECTRA standard production is 9 working days for 1- and 2-layer and aluminium boards. Multilayer boards take longer and urgent production is faster; the calculator shows the date for your exact configuration.
Is every board tested before it ships?
Yes. Every board goes through a 100% electrical test (short circuit and open circuit, flying probe) and automated optical inspection (AOI), at no extra charge.
Why do multilayer boards take longer?
The inner layers are processed first and then laminated, so there are extra imaging, etching and pressing steps, and the layers must be kept precisely aligned.
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