The PCB fabrication market size is projected to reach USD 81 billion in the global market. 2 billion people by 2025 as reported by Grand View Research [1]. This tremendous growth points to the increasing need for advanced and high-performance electronics in numerous fields. Embodied in these achievements is the complex process of manufacturing printed circuit boards (PCBs), which form the basis of today’s electronics.
It covers all aspects of PCB fabrication from the various types of techniques used, the problems faced and measures taken to achieve effective manufacturing. With these aspects, you will better understand the industry of PCB manufacturing and acknowledge the challenges of creating electronic products.
PCB Fabrication Process: Turning Design into Reality
PCB fabrication therefore serves as a link between the idea of circuit and the actual fabrication of the same. Carefully, it converts the detailed traces and positions of components from a Computer Aided Design (CAD) file into a working and durable PCB. The PCB fabrication process can be broadly categorized into several key stages:
Data Preparation and Review
The first step entails a thorough examination of the customer provided design files. This is to avoid any tolerances, fabrication specifications and manufacturability problems from going unnoticed.
Inner Layer Imaging
In multi-layer PCBs, the design patterns on layers other than the first and the last are created on copper-clad laminate sheets using a photo-sensitive film known as photoresist. This film becomes rigid when exposed to ultraviolet light and forms a covering layer over the required copper traces and pads.
Inner Layer Etching
The remaining unprotected copper is then dissolved by a chemical solution and the desired circuitry on the inner layers is formed.
Layer Lamination
The inner layers are then arranged and laminated with prepreg – a fiberglass material that is saturated with resin. In lamination, high pressure and heat are used to ensure that all the layers become one and cannot be easily separated.
Drilling
Highly precise drillings are made to accommodate the component leads and vias which are the interconnection between the layers.
Outer Layer Imaging and Etching
Analogous to the inner layers, the outer layer pattern is imprinted on the laminated core using photoresist and etching processes. This step establishes the extent of the copper details discernable on the top and the bottom layers of the PCB.
Plating
Electroless plating or the electroplating method is used to copper plate the newly exposed surfaces of the drilled holes to get proper electrical conduction. This step also forms a continuous conductive path through the via holes which link to different layers of the printed circuit board.
Solder Mask and Silkscreen
A solder mask, which constitutes a non-conductive layer, is placed over the surface of the PCB, and the pads requiring soldering only remain exposed. This helps in avoiding the formation of solder bridges during the time of populating the circuit boards with components. Furthermore, there also exists a silkscreen layer which contains essential information like the part designators and polarity symbols on a PCB.
Finishing and Testing
The last process is called edge routing, during which the PCB gets fashioned into the planned size. These boards are then subjected to several electrical tests to assess if the boards are electrically functioning in the intended design.
Challenges in PCB Fabrication
Nonetheless, PCB fabrication has turned out to be a complicated task even with the development of technology and is open to several risks. Here are some of the most common hurdles encountered:
Dimensional Accuracy
The aspect of trace width and space should be accurate so as to facilitate the desires of signal integrity and electrical performance. Minor differences also result in malfunctioning or short circuiting of the electrical circuits as well.
Multilayer Registration
In this way, it is crucial to achieve perfect planarization of the multi-layer structure after each lamination process in order to provide proper electrical connections through the vias. Misalignment can lead to conditions such as shorts and openings in the electric circuits.
Plating Defects
Improper distribution of material within the drilled holes can compromise the connection between the member and the plate and ultimately cause the component to fail.
Solder Mask Issues
A break in the solder mask results in shortening or bridging between different conducting pads, interrupting circuit performance.
Surface Roughness
A composite surface topography of a PCB makes the soldering process challenging while at the same time increasing component detachment rates.
Strategies for Addressing the Fabrication Difficulties
However, the PCB fabrication industry has come up with various strategies to tackle these issues in order to deliver quality output. These solutions include:
Advanced Imaging Techniques
LDI is much more precise than photolithography in terms of dimensional accuracy and quality because of its fine resolution capabilities.
Optical Inspection Systems
AOI systems vigilantly inspect PCBs at various stages of production and can detect any malalignment, plating, or other issues.
Panel Plating
It also aims at providing uniform plating thickness throughout the whole PCB panel while reducing variations within the via holes.
Laser Drilling
Laser drilling is a clean process resulting in very small heat affected zones making it ideal as it does not cause warping or even delamination.
Solder Mask Optimization
High-reliability solder mask materials & highly skilled application results in uniformity with no voids or any form of inconsistency.
Surface Finishing
Surface finishes such as electroless nickel immersion gold (ENIG) or other finishes smooth out the surface to allow for the soldering of parts for better assembly and reliability.
Statistical Process Control (SPC)
Applying SPC methodologies enables actual monitoring and controlling of the fabrication processes hence improving the quality and minimizing the rate of defects.
Conclusion
PCB manufacturing is an amazing process of converting an electronic design into the circuit skeleton of thousands of electronics items. It can then be stimulating to appreciate the different stages of the process, the problems faced, and the approaches used to solve such core components. With the advancement in technology of electronics, similar processes will be seen in the fabrication of PCBs, to produce even complex and powerful circuits.
