Designing a Printed circuit board is best explained as assembling and solving a puzzle. A standard PCB fabrication process begins with knowing how the assembly works. It serves as the guiding principle for an error-free design. To fix electronic elements that would work on the PCB, proper placement of these elements are vital.
When there is an existence of a PCB, components to enable its functionality exist. The significance of bringing these elements together becomes crucial. It enhances the high performance of the Printed circuit board. These components sum up the signals, reliability, and power capacity of the design.
Also, PCB board mounting means the connection of various elements on the circuit board. It provides the mechanical and electrical links on the printed circuit board. Correct placement of the components aids the PCB to function effectively.
Furthermore, mount PCB could be in two variations. The surface mount technology and the through-hole mounting. Each of these methods has its advantages. This article will delve into how each method works. It will also look at their differences, advantages, and disadvantages.
PCB Assembly Fundamentals
To understand the variations on how to mount PCB, it is vital to go through the PCB assembly basics. The guiding principles that aid correct component placements form an aspect of the process.
A survey on the reasons for electronic failures in the marketplace shows several trends. Thus, producing a faultless design is dependent on selecting quality components. The right layout, and software are also helpful factors for consideration. A wrong assembling process could turn a good idea into becoming an unsuccessful product.
Thus, the need to understand the basic principles of PCB assembly is vital. Component placement guidelines. They help to simplify the PCB assembly process. They include the following
- Components on the board must be rightly positioned to enhance good solder flow when wave soldering
- Placing components close to the edge of the board could be detrimental. It could cause damages to the board while breaking it from the panel. Thus, componentplacement should maintain a safe distance.
- Automated pick and place machines could face problems if elements are near each other. It could also slow down the process during mass production.
- Soldering issues could occur when small SMT circuit board components are next to tall components.
- Enough space is essential when placing connectors. It will allow for plugging or unplugging of wires.
- For cost reduction, SMT circuit board components should be on one side of the board. Placements of SMT circuit board components on both sides of the board could be costly. It could also be challenging in the assembly process.
- Unmatched components mounted or an incorrect footprint design on the board creates problems
Variations on how to Mount PCB
Printed circuit boards are indispensable in modern electronic devices. A careful manufacturing process of the circuit board will enhance high functionality. Also, the solid placement of the PCB keeps its components safe. Also, the right positioning of the elements contribute to the efficacy of the device.
There are two basic components placing procedure on the printed circuit board. They include the Through-Hole Mounting Technology and the Surface Mount Technology.
Through-Hole Mounting Technology
The through-hole mounting precedes the surface mount technology. It became popular after the introduction of second-generation computers. Tracks were mostly printed on a side of the PCB before its invention. Drills on the board allow the addition of lead of components inserted.
Furthermore, the components inserted occupy an empty side of the board. The process allows for the soldering of the elements to the copper at the tracked side of the board. As PCB design evolves, the inclusion of tracks becomes visible at the inner layer as well as on both sides of the board. This advancement brought about the introduction of plated through-hole. The through-hole mount technology enables the connection of components to tracks; this includes the inner and outer layer of the circuit board.
Through Hole mounting implies inserting TH elements into the drilled holes on the board. Soldering of the elements to the pads at the opposing side of the board completes the process. This process holds the anchor of electronics assembly for many years. It displaced point to point construction.
Through-hole could also mean circuit board mounting with various elements with chips and lead. They are carefully slotted into the through-holes on the PCB board. The pins go through soldering from underneath to pads in the opposite facet of the board. It is a process done either manually or by inserting mount machines.
This technology gained acceptance in the 50s. Its usage spans through the manufacturing of second generation computers. Each element on the printed circuit board got fixed using the through-hole component. In the late 80s, surface mount technology took control of the manufacturing world.
Axial Lead Components
The axial lead has a shape similar to a wire jumper. It projects out from the end point of the cylindrical or box model elements of the PCB. This projection sets up an ideal geometrical axis of conformity. However, it does not go much higher than the PCB’s surface. Thus, it maintains a flat level when positioned down on the board.
Also, the axial leads are popularly used to link short gaps on the circuit board. They also transverse point-to- point wiring not supported by open space. Using axial element mounting, the lead forming must hold a good distance to the board. This is to ensure that the components are not being mechanically stressed.
The axial lead layout might come in the form of light-emitting diodes. It could also come like carbon resistors fuses and electrolytic capacitors.
Radial Lead Component Mounting
This pcb board mounting format is perfect for use when the board has a limited area of space. The components are to maintain an upright placement position on the PCB. Its name radial originates from the aligned protrusion of the leads. It is from the board surface components.
More so, radial taping could be in various taping formats. However, the vital parameters include the component gradient and lead pitch. They fall within the range of 12.7mm and 5mm respectively. Radial taping also uses spur wheel holes in the paper tape. This will ensure the perfect component process on the tool used for placement.
Also, on the board, radial components maintain a right-angled formation. It has fewer footprints than the axial leads. They are also characterized by plug-in nature due to their side-by- side composition. The through-hole mounting process is best suitable for components that require high automation speed. They are accessible as ceramic disk capacitors.
Benefits of Through-Hole Mounting Technology
With the advent of surface mount technology, through-hole still holds its stand. Its reliability due to the strong connection between components created by soldering helped out. The through-hole technology is perfect for bigger components. These components will pass through high power and voltage.
It is best suitable for components that will undergo mechanical stress such as:
- Electrolytic capacitors
Through-hole technology allows components to run through the board. Thus they can hold firm against environmental stress. This system had the nod for military and aerospace devices. They are perfect for devices faced with extreme temperatures or accelerations.
Also, durability is another strong hold for through-hole mounted components. It is the best choice for testing and prototyping.
However, it has its limitations as well. Mentioning these limitations will be very crucial to enable full knowledge of the through-hole mounting technology.
Limitations of Through-Hole Technology
The setback with the choice of through-hole technology is the many holes drilled on the board. This increases production time and it is not cost-friendly. Although the holes drilled are to tighten the components on the board, it leaves a very minimal space. The space left is very small to allow for routing and signal tracing.
In addition, through-hole technology mostly mounts its components manually.
Surface Mount Technology
The surface mount technology was initially referred to as “planar mounting”. Its domination in the market began in the late 1990s. Printed circuits in high-tech electronic assemblies found the SMT their preferred choice.
Components got reduced and their placements became common on both sides of the board. This was possible when surface mounting displaced through-hole technology. Surface mount pcb enables higher circuit densities on a small circuit board design.
Furthermore, the modern process of manufacturing standard electronic devices has reached its maximum positive limits. These limits include volume, reliability, cost, and weight. The possibility of producing reliable assemblies at reduced cost came through SMT.
SMT is the mounting process of electrical components on the surface of the PCB. The electrical component mounted through this process is the surface-mount device (SMD). This modern approach displaced the through-hole technique of mounting components.
The general method of PCB mount was through the insertion of components via holes on the board. However, the SMT brought changes to all facets of electronics. This started from the design to assembly of components packages. Materials, substrates, and processes are not excluded. Thus, the quality of production increased, and the cost was reduced. This was achievable through the inclusion of manufacturing automation.
Surface mount technology also enables the fixing of more elements on a small area of the board. It is vital to note that both mounting processes are possible on the same board. Components used for through-hole technology differ from the ones for surface mount technology.
SMT components are smaller in size as compared to its counterpart. The components for surface mount technology entail surface-mount packages. These components possess lead at either little quantity or none at all. Holes are not needed in the surface mount technology to enable track connections.
The Surface Mount Technology Device (SMD)
The components that makeup SMD differ from those in through-hole technology. SMT design endures soldering after the components are set down on the board. The components are broadly categorized into three major types. They include;
Passive SMDs: Passive SMDs are useful to various packages. The bulk of the passive surface mount devices is either SMT capacitors or SMT resistors. Their package dimensions are fairly well standardized. Other components for SMDs include crystals and coils. They possess their separate individual conditions, and their packages differ. Connections to the PCB are through the metalization of the package.
Integrated Circuits: Various packages are the perfect fit for the integrated circuits. The extent of interconnection required is a factor dependent on the packages used. Simple logic chips require a meager amount of 14 to 16 pins. Whereas, other VLSI processors could require 200 or more pins.
With these varying requirements, numerous packages are available. Smaller chips packages that include small outline integrated circuits are usable.
Transistors and Diodes
The surface mount technology diodes and transistors are often held in a small plastic package. Connections through via leads emerge from the packages bent to meet the board. The leads used for this package are three. This allows for easy identification of how the device goes.
Designing Surface Mount Technology
The principal reason for the invention of SMT is to improve reliability, speed, and cost to assemble a PCB. Its impact also goes beyond these improvements solely. It also impacted the development of new electronic circuits, equipment, and design.
Also, these have brought so many benefits to the circuit performance than limitations. To maximize the benefits of the SMT design, there are some precautions to consider. They include:
Lower Power Rating: This is a vital component of the surface mount technology. The standard lead resistor can disperse 0.25 watts at a minimum. However, the resistor on SMT being smaller in size will dissipate less.
Lower spacious capacitance and inductance: Due to the small size of the components, the space for inductance and capacitance is small. Resistors for SMT function when close to the standard resistor. Meanwhile, it does not as per the leaded resistor. Thus, the SMT resistor displays a lower parasitic inductance.
More so, the standard components of the SMT allow for high speed and frequencies. It wouldn’t be possible with lead components.
Smaller Circuits: As the electronic industry experiences growth, SMT contributed by allowing miniaturization. Components are smaller and they are easily mounted on the printed circuit board. The element placement could be closer together on the board than it was on the general lead elements.
Advantages of Surface Mount Technology
- Surface Mount allows for componentplacement on both sides of the board. Higher component density and connections are also possible.
- Electromagnetic compatibility is easily achieved using the SMT.
- A smaller PCB design that allows more components placed closely together is possible. This enhances the production of a compact and lightweight design.
- The production setup is faster using the SMT as compared to through-hole technology.
- SMT enhances high circuit speed due to the compact nature of PCB designed using the SMT.
- SMT allows low resistance and inductance at connection. It helps provide good high-frequency performance.
The mounting of components on the circuit board is an essential factor for consideration. In the manufacturing process, through-hole and surface mount technology drive components placement. This aids the functionality of the circuit. Also, accurate placement of these elements remains very crucial. Thus, manufacturers must pay reasonable attention to the mounting process.