Step by step guide which will help to understand the PCB fabrication process. PCB manufacturing and assembly must be conducted in a clean environment that is free of contaminants. This is important to produce good quality boards that offer unfailing service for years.

1. By - Sierra Assembly Technology Inc.
PCB Fabrication Process

2. Introduction
• PCB fabrication is a laborious process with several time consuming steps.
• PCB manufacturing and assembly must be conducted in a clean environment that is free of
contaminants.
• This is important to produce good quality boards that offer unfailing service for years.
• PCB fabrication processes are briefly described in the following slides.
Sierra Assembly Technology Inc. (sales@sierraassembly.com)

3. PCB Fabrication Steps Listed
Designing Electronic Circuits
Layout Printing
Preparing Substrates
Etching
Drilling
Electroless Copper Deposition
Soldermask Application
Assembly
PCB Testing
Cutting Individual PCBs
Final Testing
Sierra Assembly Technology Inc. (sales@sierraassembly.com)

4. Designing Electronic Circuit
• With increasing complexity of electronic products, the demand for extremely convoluted PCBs is on the rise.
• PCBs are nowadays designed complicatedly with lots of connections and interconnections.
• PCB design is one of the crucial steps that must be carefully executed.
• At the design stage, it is important that the manufacturer and the customer work in hand in hand. This is the stage that
calls for lots of reworks.
• With the advancements of technology, several PCB design software are developed, supporting and easing the work of PCB
designers. One of the most popularly used design software is Eagle.
Sierra Assembly Technology Inc. (sales@sierraassembly.com)

5. Layout Printing
Once the customer approves the design, the layout is printed on any
photo basic gloss transparent paper.
Generally, laser printers are used for printing the layout.
Ensure that the layout is completely printed onto the paper. It is advisable
to take a sample print on a plain paper, and check the clarity and
completeness of the layout. After confirming details on the sample print,
you can move onto printing the layout on the gloss paper.
It is advisable to keep the print untouched for some time. This helps in
drying out the ink completely.
Sierra Assembly Technology Inc. (sales@sierraassembly.com)

6. Preparing Substrate
The next step is cutting the layout by leaving a generous amount of blank spaces in its sides.
Now, place the layout onto a laminated copper clad board.
Note – Copper laminate must be sized according to the dimensions of PCB layout.
Apply some heat and pressure on the assembly, and keep it untouched this way for some time.
The PCB layout will now be attached to both the paper and the copper laminate.
The paper on which the layout is printed must be removed at this stage.
The easiest and fastest way to accomplish this is soaking the substrate in water for some time.
Wait for a few minutes and take the substrate out from the water. Peel off the paper from the assembly. You may still find
remains of paper in the assembly. Remove the leftovers by soaking the assembly again in water for few hours.
Sierra Assembly Technology Inc. (sales@sierraassembly.com)

7. Etching
• Now, your assembly contains only a copper laminate with PCB layout attached to it.
• The purpose of etching is to remove unnecessary copper traces from the substrate.
• Though there are several etching solutions available, the most commonly used are ferric chloride or hydrochloric acid.
• Dip the assembly in the etching solution for some time. Take it out at times and see whether excess copper traces have
been removed. Continue the process until excessive copper is removed from the substrate.
• You can rub the board with a little acetone once the etching process has been completed. This renders a clean and shiny
finish to the board.
Sierra Assembly Technology Inc. (sales@sierraassembly.com)

8. Drilling
The next step in the PCB fabrication process is drilling holes.
Small to large holes are created to attach PCB components utilizing advanced laser drilling techniques, including:
• Excimer (ultraviolet)
• YAG (Infrared) lasers
• CO2 lasers
In addition, automated drilling machines and drill presses are also utilized to create precision holes.
Extreme care must be taken when drilling holes on the board. If not, it will damage the board beyond use
Sierra Assembly Technology Inc. (sales@sierraassembly.com)

9. Electroless Copper Deposition
Chemical deposition of a very thin layer of copper on the walls of the holes is the next crucial step in the PCB fabrication.
The plating thickness is usually kept as 1 mil and sometimes it is set as half mil.
Sierra Assembly Technology Inc. (sales@sierraassembly.com)

10. Soldermask Applications
• Coat the entire panel with a liquid soldermask. The board is then exposed to high intensity UV light.
• Soldermask is applied to achieve the following:
• Protect copper circuitry from oxidation, damage, and corrosion
• Prevent solder shorting between components, and maintain isolation of the circuits during assembly.
Sierra Assembly Technology Inc. (sales@sierraassembly.com)

11. Assembling
Now, it is time to assemble all the electronic components onto the respective holes in the board.
The components that are assembled in the board include:
• Terminals and Connectors
• Resistors
• Switches
• Capacitors
• Network Components
• Diodes
• Transistors
• Integrated Circuits (ICs)
The following techniques are employed in assembling these electronic components:
• Surface mount assembly
• Through-hole assembly
Sierra Assembly Technology Inc. (sales@sierraassembly.com)

12. PCB Testing
The finished boards are then sent for functional as well electrical
testing to ensure optimum performance and quality.
Different methods such as Bed of Nails Test, Rigid Needle adaptor, CT
scanning test, and flying probe are utilized to test efficacy,
operational excellence, and durability of the final assembly.
Every PCB assembly is comprehensively tested against the original
board data.
Sierra Assembly Technology Inc. (sales@sierraassembly.com)

13. Cutting Individual PCBs from the Production Panel
The final manufacturing stage is cutting individual PCBs from the production panel.
Generally, PCB manufacturers utilize computer-controlled milling machines or routers to cut individual PCBs without damaging
other boards in the panel.
Sierra Assembly Technology Inc. (sales@sierraassembly.com)

14. Final Inspection and Packaging
A team of sharp-eyed inspectors performs a final check on the finished assembly.
A rigorous inspection is conducted on individual boards to find out any obvious defects like scratches. Also, the team cross
checks the assembly with the mechanical drawing.
In addition, they also check compliance of the board with the specifications provided by the customers.
In addition to manual checking, several automated inspection machines are also utilized in this stage to inspect the final
assembly.
The approved boards are then vacuum sealed for protection. They are bubble-wrapped and securely boxed to keep out dirt,
moisture, and other contaminants. Sierra Assembly Technology Inc. (sales@sierraassembly.com)

15. Conclusion
As you can see in these slides, PCB fabrication involves several time consuming steps that must be done with utmost care.
Any flaw in these manufacturing processes will affect the performance, functionality, and durability of the final assembly.
PCBs that are fabricated following the right fabrication process will last long, and offer superior performance for many years.
Sierra Assembly Technology Inc. (sales@sierraassembly.com)