Ultimate Guide to PCB Fabrication Process in 20 Steps

PCB Design and Layout

Of course, the beginning step of any PCB manufacture is the design. The PCB layout should be designed in any readily available simulator.

PCB manufacture and design always start with a plan: the designer lays out a blueprint for the PCB that fulfills all the requirements as outlined. 

While designing the PCB layout, you must consider certain things, such as the width of the routes, connecting different elements, and placing vias of a specific size.

Prototype circuit boards should be compatible with the designer who creates a PCB layout using PCB design software.

NOTE: Before PCB fabrication, designers should inform their contract manufacturer about the PCB design software version used to design the circuit (commonly used software includes Altium Designer, OrCAD, Pads, KiCad, Eagle, etc. ). This helps avoid issues caused by discrepancies.

Different PCB design software may require additional Gerber file generation steps(we provide knowledge about generating Gerber files in Altium and Eagle); they all encode comprehensive vital information, including copper tracking layers, drill drawings, apertures, component notations, and other options. 

So it needs a thorough examination, designers forward PCB files to PC Board Houses for manufacturing.

Almost all PCB Fab Houses run Design for Manufacture (DFM) checks before circuit board fabrication to ensure the design fulfills minimum tolerances during manufacturing.

After all the checks are complete, the PCB design can be printed.

Pre-Production Engineering

The customer sends us a document, which is then submitted to the engineer for review and an accurate quotation again. We help confirm whether the production documents are missing or wrong and determine the process steps and associated checks.

Then, start to arrange production after confirmation.

Production Prepare

Cut Lamination

Cutting and laminating according to the size of the finished board or the size of the panel;

Drying

The primary purpose of drying is to remove the moisture in the board and prevent it from warping during processing. Generally, it is dried at 150℃ for 3-4 hours.

Inner Layer Imaging

Inner Film

A dry film is applied to the bare copper core board, and all photo image reactions are performed on the dry film.

Inner Exposure

Inner layer development

The exposed core plate is developed, the unexposed dry film is set to reveal the original copper skin, and the exposed dry film is retained.

Photoimaging is the primary process of open and short circuits. Therefore, the environmental sanitation requirements are very high. The air shower door must be cleaned before personnel enter, and all operators need to wear antistatic clothing.

Inner Layer Etching

Etching

The etching line protects the copper skin covered by the dry film, while the copper skin not protected by the dry film is etched away.

The line pattern that needs to be retained will be displayed by etching.

Unloading the film

Retreat the dry film of the copper sheet on the core board, and the line pattern to be retained is finally formed.

Inner Layer AOI

This is an automatic optical inspection to check whether the core plate after etching has an open or short circuit and whether the etching is clean.

Lamination

The copper foil is pressed to one board through an insulating medium (PP) between the layers.

Drilling

Drilling the laminated plate. At this time, there is no metal in the hole; that is, the layer cannot be connected to the layer.

Electroless copper deposition

The hole is coated with a skinny layer of copper through the chemical reaction, about 2-3 um.

Horizontal Electrolytic Plating

Since a thin layer of metallic copper is already in the hole, the copper in the base plate and the copper in the gap can be thickened to 5-8um by an electron transfer reaction.

Outer Layer Imaging

Outer Layer Film

A dry film is applied to the bare copper core board, and all photo image reactions are performed on the dry film. The hole is drilled into the plate; the dry film is attached to protect the spot.

Outer Layer Exposure

Outer layer development

This step differs from the development of the Inner layer because the copper under the dry film is the last to be retained after the inner layer is developed.

After the outer layer is formed, the copper of the dry film is the previous copper to be etched, and the copper that needs to be preserved is exposed at this time.

Graphic Plating

Thick copper plating

The bare copper (which needs to be retained at the end) is plated to the finished copper thickness. Generally, the copper plating thickness is 18-25 um.

At this time, the surface copper and copper thickness in the hole are plated together to reach the finished copper and hole copper thickness requirements.

Tin plating

To protect the copper foil, the surface of the copper has been thickened with a layer of white metallic tin.

Getting rid of the film

The dry film attached to the board is removed. At this time, the copper under the dry film will be exposed (etched away), and the copper that needs to be retained will be protected by tin underneath.

Outer Layer Etching

Etching

The tin protects the desired copper during this stage. The line will etch away the exposed copper while the copper-covered container will remain.

Tin Removed

The tin used to protect the copper is removed. The copper that needs to be preserved will be exposed at this time. All the outer circuit patterns have been completed up to now.

Solder Mask

Coat the entire panel with a liquid solder mask. The board is then exposed to high-intensity UV light. The solder mask protects copper circuitry from oxidation, damage, and corrosion.

WellPCB prints the solder mask under customers’ requirements and does not have an extra charge.

Silkscreen

Silkscreening is a vital step since this process prints essential information onto the board. Then, the PCB finally passes through the coating and surface finishing process.

Surface Finish

This step is to enable protection of the surface and good solderability. Joint surface finishes include Electroless Nickel Immersion Gold, Hot Air Solder Leveling(HASL),  Lead-Free HASL, Immersion Silver, OSP( anti-oxidation), etc.

Following the implementation of the Rohs directive in the EU, all products containing lead and bromine will not be allowed to enter the EU market; therefore, the traditional pewter process will be gradually replaced.

WellPCB defaults to the lead-free HASL for our customers. If you need to deal with it in a different way, please check the box when you place the order.

Profile

The engineering department creates a shape program based on the border provided by the customer.

The shaping process is based on the engineering department providing milling.

Other Surface Finishing Process

Such as V-CUT, gold finger beveling will be done after the profile process.

V-CUT

This is the process of cutting the manufacturing panels into specific sizes and shapes based on the custom design of the Gerber data.

The method employed either centers on using a router or a v-groove.

A router leaves small tabs along the board edges while the v-groove cuts diagonal channels along both sides of the board.

Both ways permit the boards to pop out from the panel easily.

Gold Finger

PCB connection points are primarily subject to constant plugging and unplugging due to their nature of interconnecting PCBs.

Hence, without a strong contact edge, they are prone to wear and tear that can cause device malfunction.

The act of plaiting the connectors with other metals (in this case, gold) enhances the durability of the edge connectors.

Know more here

Electrical Testing

So far, the board production has been completed, but another important thing is to conduct electrical testing to ensure functionality.

The main tests that are performed are the circuit continuity and isolation tests.

Basic electrical reliability testing, used for checking the integrity of the tracks and the through-hole interconnections-checking to ensure there are no open circuits or no short circuits on the finished board.

WellPCB using Flying Probe Testing depends on moving probes to test the electrical performance of each net on a bare circuit board.

To ensure optimum performance and quality, we check each net to ensure it is complete (no open circuits) and does not fall into any other trap.

Final Visual Inspection(FQA、FQC)

This is the final step in the PCB fabrication process. The professional quality control team will perform the final inspection of each PCB, including visual inspection, finished product size inspection, aperture hole number measurement, warpage measurement, etc.

We will print a test report for customer reference if the review is qualified.

Package&Delivery

After inspection, the PCBs are vacuum-sealed to keep out dirt and moisture. They are then securely boxed, sealed, and shipped by courier to customers all over the world.

WellPCB suggests DHL and FEDEX, which are more convenient and fast – generally 1-4 Days so you can receive the board as soon as possible and start your project soon.

Conclusion

I believe you have a general understanding of the fabrication process of PCB after reading this guide

If you are ready with your PCB design and want to implement it for your project, try using our quotation system and upload your CAD or Gerber files.

Our experienced professionals are available for consultation and to advise you when needed.

You can contact us to learn more about PCB manufacturing steps or problems encountered in file generation. We are always at your service.