1. Introduction

Printed circuit board (PCB) is a multi-layered core electronics component with each layer having a unique design, layout and functionality resulting in well-structured equipment. Pre-planning PCB design and layout is quintessential for its adherence to industry best practices. It is obligatory to comprehend the weight of PCB board layout as part of the enduring journey in the market and to have an active participation in the success of projects rather than failure. With technological advancements, the demand for small and intricate PCB layout designs is elevating exponentially thus amplifying the need for proper strategizing of PCB layouts. From discussing the meaning of optimization to exploring different PCB design and layout optimization techniques, let us unfold covert insights for a modern-day successful PCB board which walks hand-in-hand with technological needs and is engineered with the best possible optimized layout.

PCB Layout Design

2.What is PCB Layout?

PCB layout is referred to as the spatial management of electronic devices and their interconnections on a PCB board set-up. It encompasses the substantial arrangement of different components of a device and the tracing of copper paths responsible for the movement of electrical currents across the PCB board. The PCB design and layout stage is the first step in manufacturing a PCB board. Printed circuit board layouts are not made just by anyone; rather technical professionals are hired to meticulously design an optimized PCB layout called PCB designers or circuit boards layout engineers. Specialized software is used by designers and engineers to craft and envision different PCB layouts considering all manufacturing parameters. Employing software not only makes the layout designing process easier but also saves resources by avoiding actual tracing of routes on PCB boards. With the ever-high need of an optimized PCB board layout due to reduction of physical dimensions of devices, it is a necessity to know what the difference between a circuit board layout and an optimized PCB layout is. 

The circuit board layout is the initial configuration of various elements on a PCB circuit board and routing of different pathways to establish a serviceable and operative PCB where primary focus is on connecting different nodes with one another taking in account all space-constraint parameters whereas optimized printed circuit board layout is refined circuit board layout; making altercations to printed circuit board layout to achieve improved performance, cost-effectiveness and smooth operation. Optimization of PCB layout is peculiarly done to fit maximum components on a single PCB board with minimal signal loss, reduced signal interference, perfected signal paths, increased signal integrity, proper power distribution and thermal management. Some key strategies are listed and compiled below to optimize a normal functional PCB circuit board.

3.Optimization Strategies of PCB Layout 

A number of approaches and techniques are put in service for optimization of a PCB board layout to meet industrial field requirements, cost-effectiveness, manufacturability and maximum efficiency and are discussed as follows:

1. Component placement: Components should be placed in a way to make it easier for assembler to organize different components. To achieve better results, it is advised to manually scheme the placement of different elements. Components working together should be placed nearby, power supply at a position where all elements can reach it easily and always keep room for a few extra traces for modifications, if needed.
2. Proper spacing of components: Close placement of components is alluring but should be avoided. Close placements do not make a layout optimal, rather induces problems at the time of soldering. Thus, it’s necessary to find a middle ground between close placement and optimal space between components.
3. Trace angles and lengths: 90-degree bending of copper traces is avoided to prevent corrosion and scabbing of routes on the board. 90-degree angles are more susceptible to radio frequency effects adhering to less stability of PCB layout design. In comparison to that, 45-degree angle ensures the possibility of having maximum tracks on least area possible on PCB board and is not much prone to corrosion. While maintaining the 90^o rule, trace lengths should be kept as short as possible to be secure against diverse types of signal degradations.
4. Length matching of traces: Traces are made of matching lengths to ensure simultaneous arrival of two different signals at a particular destination node. Arrival discrepancy between signals not only leads to delays but also assists to signal noise, thus pertaining to signal degradation. This technique should be used while designing PCB layout to prevent untidiness on PCB board. 
5. Proper orientation of components: To make soldering, assembly and testing of PCB boards easy, components should be placed uniformly in their pre-defined orientation given by their pin numbers.
6. Design For Manufacturing (DFM): It is important to keep consulting the guidelines provided by designer for trace widths, spacing, clearances and hole sizes time to time while assembling PCB.
7. Cross hatching: Cross-hatching is defined as the technique of using alternate wiring in adjacent layers of a PCB board. It is implemented for a number of reasons such as- electromagnetic coupling between two adjacent layers is prevented, thermal dissipation becomes even across all layers, parallel-plate capacitance effects are reduced to impressive levels and EMI interference is also reduced.
8. Trace width: It is one of the principal factors in making the PCB layout effective. Maximum current flowing via the trace, copper thickness and power requirements of components is calculated and fed into numerous online trace-width calculators available as input. Proper trace-width is essential for smooth journey of currents across PCB.
9. Trace spacing: Trace spacing is an important criterion while seeking out to optimize a PCB layout design. Preferably, it is greater or equal to 1.5 multiplied by trace width to isolate two adjacent routes, evade crosstalk, decrease signal interference and minimize parasitic capacitance.
10. Vias: In multi-layer PCB boards, vias are used to maintain electrical connectivity across all layers. However, vias can be both beneficial and harmful in making a PCB layout perfect. On a positive note, vias connect all the layers smoothly; increasing signal integrity and increasing routing flexibility while on the other hand these are known for causing reflections and increasing signal interference and crosstalk. To put vias to best aid, it is needed for the designers to carefully access the design specifications and accordingly plan their placement.

PCB Layout

11. Ground and Power planes: These are separate layers present in a multi-layer PCB board. The ground layer is responsible for providing low-impedance paths for signals to return while on the other hand, power plane distributes power supply across all layers. However, both planes safeguard PCB against electromagnetic interference. The power and ground layers are connected together at only the power input point of PCB board to control interference.
12. Parallel paths: Routes are designed in a parallel fashion for a PCB design layout. While the dapper look parallel paths create greatly delights the eyes, it concurrently reduces noise between two signals and even aids to signal amplification.
13. Impedance test equipment: Affording certainty to impedance matching, test equipment is employed to check impedance of traces and to measure the return loss of signal. It is executed to make all the necessary modifications in attaining desirable impedance of PCB boards.
14. EMI shielding: Electromagnetic interference shielding refers to blockade of external unwanted signals such as radio waves which may tamper with the proper functioning of PCB or other electronic components. It is achieved by inculcating a number of safety measures in PCB design such as- using materials with high electrical conductivity, using EMI filters and introducing power/ground planes in PCB.
15. Heat control elements: These are used to keep heat in control generated by some components such as voltage regulators, transistors, etc. Heat control elements commonly comprise of heat sinks and coolers which should be placed appropriately away from all the main parts of a PCB board to avoid system failure. 
16. De-coupling capacitors: These are not used by every manufacturer in the name of optimization of space on PCB boards but there is no other say while contemplating their involvement in PCB layout design. De-coupling capacitors are cheap and robust and must be included wherever possible and should be placed near ICs for better noise reduction.
17. Proper assembly techniques: During the final assembly of components on the PCB board, make sure to solder the small elements first and then adequately move all the way up to big components. It is recommended to do so as bigger components block the paths and make it difficult for easy movement of hands while soldering small components thus making the process more error prone.

4.Conclusion

PCB layout design is a complicated process but ensures the proper functioning of PCB in the long run. While we can work with a normal PCB layout, it is best practice to use optimized layouts for important devices, projects and products.