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Manufacturing a PCB is a complex task with several stages involved. From designing a PCB to assembling, one has to be critical about a number of things, such as the material being used, the design of PCB, fabrication techniques and the layering processes, and each stage needs to be properly documented. In this post, we shall discuss the details of the fabrication process. The fabrication process is quite critical and keeping in view the compact nature of modern devices, it has become even more complex.

Before initiating the fabrication, an appropriate PCB design needs to be well in place as it may impact the outcome in terms of tolerances, the level of Coefficient of Thermal Expansion, and structural reliability. The design should include details regarding drilling, layering, copper-coated layers, apertures, components, etc. A flawless design can make the work of the fabrication team much easier. Using the design specification, the actual physical board of the PCB is formed.

The process of fabrication, in itself, involves a number of techniques and processes. Firstly, layouts are made on copper-coated laminates using images as references. Excess copper is scraped off by the etching technique so that the traces and pads are clearly visible. Holes are drilled for the purpose of component mounting. Following the process, the boards are either soldered or extra protective layers are added. Markings such as logos, company name etc. are also added during the fabrication process. Then, the copper-coated surface is fine-tuned, for a perfect finishing. 

These are some basic steps involved in the process of fabrication. However, the ongoing advancements in the field of science and technology pave way for further innovations that deliver more effective techniques, delivering boards with better functionality and capabilities. In addition to addressing the basic needs of a PCB, the modern PCBs are more flexible and compact in nature and have high resistance to heat and hold the capacity to withstand any environmental parameters.

PCB Laminate is an essential component as it holds the different layers of a PCB together. Traditionally, a PCB has multiple layers of substrate, copper, solder mask, and silkscreen. These layers are sandwiched between the laminate sheets that are then heated and pressurized to create the final piece of uniform thickness; the process is called lamination.

There is various material available for lamination like FR-4, Polyimide, Teflon etc. It is essential to choose the appropriate material for lamination as it forms the base for the PCB. The selection of appropriate material is a technical process as it requires due consideration of the thermal, electrical, chemical and mechanical properties of the material.

Do consider the following points while selecting application-centric PCB laminate material:

Mechanical Properties:

• High Peel Strength for lesser chances of de-lamination. The peel strength is the bonding force between the lamination and the copper layers.
• High Flexural Strength to avoid any cracks or breaks. Flexural strength is the ability of the material to withstand physical stress without causing any cracks or damage to the material.
• Delayed De-Lamination Time for higher durability. The delamination time defines the duration, a PCB laminate can withstand exposure to high temperatures before it starts to unravel. 

Thermal Properties:

• Optimal Glass Transition Temperature (Tg). The glass transition temperature defines the sensitive temperature range of the substrate, exposure to which can cause the substrate to harden or soften.
• Lower Thermal Expansion to avoid any changes in the dimension or other stress on the PCB. This is possible if the substrate has higher CTE i.e. Coefficient of Thermal Expansion. CTE is the expansion rate of a PCB.
• Higher Thermal Conductivity (k) to allow adequate heat distribution. It is directly linked to the heat transfer capability of the board. A lower k may result in uneven distribution of heat across the board which might result in overheating of certain layers.
• Higher Decomposition Temperature (Td). If exposed to a higher temperature, the substrate starts to decompose, which needs to be avoided in any case. It is essential to ensure that the Td of the material is higher than that of the board.

Chemical Properties:

• Non-Flammable Material. When exposed to heat, if the material is combustible, there are chances of the circuit board catching fire. 
• Moisture Absorption Value of Substrate ranging from 0.01% to 0.20%. The moisture absorption value directly affects the substrate’s thermal and electrical properties. It also increases the rate of delamination, making it water-resistant.

Electrical Properties:

• Dielectric Constant (Er) ranging between 3.5 to 5.5 Er. The electrical resistance and signal integrity of the substrate defines the Er. The dielectric constant and dielectric loss tangent of the material needs to be maintained at a stable range to avoid electric shocks.
• Dielectric Loss Tangent ranging between 0.02 to 0.001 to not let the material lose its strength. Though, one must be very careful of the Loss tangent in the case of analogue signals. 
• Higher Electrical Strength ranging between 800V/mil to 1500V/mil to withstand any electrical breakdown.
• Also, one must ensure the optimal Volume Resistivity (p) and Surface Resistivity (pS) of the substrate.

The above-mentioned properties play a crucial role in defining the efficiency of your circuit board. The safety and smooth functioning of your electric device is major concern, and one must never ignore that. Only seek a trusted name like Gelco when it comes to electric solutions like these.

PCBs stand for Printed Circuit Boards that act as functional blocks for most of the electronic devices. Almost all modern electronic devices, such as medical scanning devices, computer systems, LEDs, home appliances, industrial manufacturing and power equipment, sensors and safety devices, smoke detectors etc. function on PCBs.

PCBs are designed to provide controlled and reliable electrical connections between various component terminals. The patterns of a PCB design are critical to its functional utility. They have alternatively placed layers of conductive and insulating material to allow routing of the electrical connections and to control signal integrity. 

Design specifications of a PCB may vary according to the application requirements of the respective electronic device. But broadly, we can categorise PCBs into following types:

TYPES OF PCBS

Single Sided PCBs

This is the most basic kind with a single layer of copper which acts as a conductor of electric current passing through the components. Being basic in nature, they aren’t very costly and are mostly used in case of simple circuit electronics like sensors, electric toys, calculators, LED boards etc. Also, they are easy to design and manufacture and repairing them doesn’t require much expertise. 

Double Sided PCBs

The Double Sided PCBs are quite similar to the Single sided PCBs. The only difference is that a  Double Sided PCB has two layers of conductive copper, placed on both top and bottom of the board. Holes are drilled in the circuit board that connect the metal parts to both the sides. They are used for comparatively more complex devices such as mobile phones, test equipment etc.

Multi-layered PCBs

A multi-layered PCB has at least three or more layers of conductive material. Designing a multi-layered PCB is a crucial process as there is a possibility of air being trapped between the layers. Therefore, utmost care needs to be taken while assembling a multi-layered PCB. However, the type of PCB is compact in size and has higher flexibility which makes it easier to incorporate controlled impedance features. They are best applicable for aerospace devices, x-ray and other testing devices, satellite systems, GPS technology etc.

Rigid PCBs

A Rigid PCB can hold as many layers of conductive material, there is no such specification on that. They can be single layered or double layered or multi-layered type PCB, depending on the application. What makes it rigid is that once the PCB is manufactured, it cannot be altered. A rigid PCB cannot be bend into any other shape. They are made of solid substrate with copper tracks. They are commonly used for devices of daily use like computing systems etc. 

Flexible PCBs

On the contrary, a flexible PCB is fabricated in a way that it can be folded or transformed into any desired shape. They are mostly placed in modern portable devices like hard disks, printers etc. that hold limited internal space due to their very compact structure.

Rigid-Flex PCBs

A Rigid Flex PCB is a type of a hybrid PCB board which has both – a rigid hard board connected with multiple flexible PCBs. Having a complex structure, designing and assembling process is more complicated and expensive. However, there is a growing demand for Rigid-Flex PCB due to its convenient applicability. Most commonly used for devices that require multiple circuit boards. 

High-Frequency PCBs

A High Frequency PCB is specially designed to meet the requirement of transmitting signal  to your electronic device. It can be either of the PCB kinds – flexible or rigid, majorly used for the purpose of incorporation high frequency flow rate. Such PCB designs are applicable in industries that require high-density interconnect such as telecommunication, military, aerospace etc.

Aluminium Backed PCBs

This PCB type is similar to any of the above mentioned PCB, the only difference is usage of aluminium as the conducting metal instead of copper. It inexpensive and environment friendly as it can be easily recycled and is non-toxic. They are used mostly for devices expected for high output power applications such as power supplies, traffic lights etc.

There are a number of PCB designers and manufacturers  in the market but it is always advisable to buy PCBs from a reputed and trusted name. Gelco is one such trusted and experienced manufacturers of different types of PCBs. The company has consistently provided their customers with high-quality circuit boards with excellent speed, and performance.