A Day in the Life of the PCB Manufacturing Process

Zachariah Peterson
|  Created: June 21, 2022  |  Updated: July 2, 2022
PCB Manufacturing Process

Before implementing design for manufacturing, it is important to understand the underlying process behind producing a physical PCB. Regardless of the various technologies present in each facility, a large majority of industry-leading manufacturers follow a specific set of steps to turn your design from a drawing in a CAD application into a physical board.

The standard PCB manufacturing process follows a specific set of steps, and it's up to designers to know and understand all the steps involved in the PCB manufacturing process. By knowing the steps in the manufacturing process, it's much easier to spot PCB design mistakes that create risk of production failures which would require scrapping a board. Every designer must implement design for manufacturing (DFM) steps so that it will be possible to fabricate and assemble a PCB anywhere.

In this article, we'll cover the basics that designers need to know as part of our crash course series on PCB manufacturing. We'll briefly start with the PCB fabrication process that is used to create a bare board. Next, we will examine the PCB assembly process, where components are soldered onto the finished PCB before final test and inspection. Design for assembly (DFA) focuses on design practices that ensure components can be reliably assembled, and just like bare board fabrication, designers have a responsibility to be familiar with the PCB assembly process.

Standard PCB Fabrication Process

PCB fabrication focuses on bare board construction, etching, drilling, and finishing. The table below outlines the standard set of steps used to manufacture multilayer PCBs. This process begins with a complete set of design specifications and initial laminate materials, and it ends with a fabricated board that if fully ready to assemble.

Step 1:

  • Data Transfer from Customer
  • Data Prep
  • Cores/Laminate

Step 2:

  • Dry Film Resist Coating

Step 3:

  • Place Artwork
  • Expose Panels to Ultraviolet Light
  • Develop Panels (resist removal)

Step 4:

  • Etch

Step 5:

  • Strip Resist

Step 6:

  • Oxide Coating

Step 7:

  • Multilayer Lamination
  • Primary Drilling

Step 8:

  • Deburr and Clean
  • Desmear
  • Copper Deposition

Step 9:

  • Dry Film Photoresist Coat

Step 10:

  • Expose and Develop

Step 11:

  • Copper Pattern Plate (electroplating)

Step 12:

  • Strip Resist

Step 13:

  • Etch

Step 14:

  • Apply Solder Mask and Cure

Step 15:

  • Surface Finish Application

Step 16:

  • Apply Silkscreen Legend and Cure

Step 17:

  • Depanelization

With the final curing of your board complete, a manufacturer will then begin an electrical test process based on the test points you specified in your PCB layout. Electrical testing in the fabrication stage will normally involve continuity testing, where opens and shorts are verified between various nodes called out in your PCB netlist. All boards that pass this verification process are considered complete and are transferred into assembly.

Throughout the PCB fabrication process, there are multiple defects that could occur during production. The most common defects will occur during etching, drilling, and plating steps. Some of the possible fabrication defects that can occur and their possible solutions are listed in the table below.

Defect

Could be caused by…

Overlapping drill hits

  • Vias spaced too close
  • Mirrored holes into Gerber drill data

Unintended shorts

  • Plated holes placed too close to other conductors
  • Fine pitch between copper
  • The “1 mil clearance” defect

Trace detached from pad

Removed solder mask

  • Excessive solder mask opening, which leaves behind solder mask slivers

Pad delamination

  • Using an NSMD pad instead of an SMD pad
  • Processing temperatures for outer layers too high with thin copper

Open (unfilled) via-in-pad

  • Must specify via plug and plating to allow for via-in-pad designs

Unreadable silkscreen legend

  • Silkscreen legend too small
  • Silkscreen too close together
  • Silkscreen linewidth too thick

Open or short nets not caught during testing

  • Testpoints were not specified correctly
  • Testpoints were specified on internal layers

 

Once the design has passed fabrication and it has been electrically tested, the board could go through a further battery of tests to ensure quality. This normally involves environmental or mechanical testing to ensure the bare board fabrication process does not damange any materials or etched features in the PCB.

Standard PCB Assembly Process

PCB assembly involves placement of components with automated machinery (a pick-and-place machine) and subsequent soldering with an automated process. The main automated techniques for soldering in the PCB assembly process are

  • Wave soldering, used with through-hole components
  • Reflow soldering, used with SMD components
  • Selective soldering, an automated version of hand soldering

Hand soldering is not used in high-volume PCB assembly facilities unless it is aboslutely necessary. The reason for this is the very slow nature of hand soldering, and the varying consistency due to differing skill levels among workers.

After a finished PCB exits the soldering process, it will be inspected with automated equipment, and it will be cleaned of any residues (particularly flux residues) before being packaged and shipped. Completed PCBAsmay also go through their own inspection and testing process to identify any PCBs that would suffer from premature failure. These accelerated life tests involve subjecting a PCBA to extreme heat, pressure, mechanical stress, and electrical stress to determine the operational limits of the device. Once these limits are determined, the processing parameters or the design might be modified to ensure long-term reliability of the design and the final product.

PCB assembly process

The easiest way to ensure your design will comply with standard DFM/DFA requirements is to take advantage of your PCB design rules. The DRC engine in your design software can be customized around certain rule sets so that you can rest assured your layout will not suffer from common PCB manufacturing defects. Make sure you set DFM/DFA requirements in your design rules before you start your PCB layout.

When you're ready to take a DFM-centric approach to designing your PCB, the process begins with material selection as you start to create your PCB stackup. Material selection can affect DFM in some specialized products, such as high-frequency designs and in high voltage PCBs. Make sure you understand the wealth of material properties for PCB materials and how these affect manufacturing.

When you're ready to start your design and you want to make sure you meet every DFM requirement, use the design and layout features in Altium Designer®. Once your design is ready for a thorough design review and manufacturing, your team can share and collaborate in real time through the Altium 365™ platform. Design teams can use Altium 365 to share manufacturing data, project files, and design reviews through a secure cloud platform and in Altium Designer.

We have only scratched the surface of what’s possible with Altium Designer on Altium 365. Start your free trial of Altium Designer + Altium 365 today.

About Author

About Author

Zachariah Peterson has an extensive technical background in academia and industry. He currently provides research, design, and marketing services to companies in the electronics industry. Prior to working in the PCB industry, he taught at Portland State University and conducted research on random laser theory, materials, and stability. His background in scientific research spans topics in nanoparticle lasers, electronic and optoelectronic semiconductor devices, environmental sensors, and stochastics. His work has been published in over a dozen peer-reviewed journals and conference proceedings, and he has written 1000+ technical blogs on PCB design for a number of companies. He is a member of IEEE Photonics Society, IEEE Electronics Packaging Society, American Physical Society, and the Printed Circuit Engineering Association (PCEA), and he previously served on the INCITS Quantum Computing Technical Advisory Committee.

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