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In electronic engineering, electronic circuits are a surface made up of paths, tracks or buses of conductive material laminated on a non-conductive base. Electronic boards are used to connect through conductive tracks a set of components, all previously designed to cover a function.
Copper is generally used for the tracks, while the bases of the electronic circuits are made of reinforced fiberglass resins, ceramic, Teflon or other non-conductive materials.
For the production of PCBs and the assembly of components can be automated. This allows mass production to be more economical and reliable than other assembly alternatives. But for small series or prototype assemblies the assembly is manual.
Technology for the assembly of electronic circuits
Originally, all PCBs were assembled by hand using only a soldering iron. As technology advanced, components became smaller and more difficult to assemble by hand and the number of components that could fit on a single board increased. Therefore, the need for automatic assembly developed.
Surface mount technology
Surface mount technology, also known by the acronym SMT, is one of the most widely used electronic device assembly methods in use today. It is used for both active and passive components.
Surface mount technology (SMT) is a method in which the components are placed directly on the surface of the printed circuit boards, without using through holes for component attachment.
Nowadays, most electronic devices are manufactured with this technology, since they provide great advantages in terms of manufacturing and performance, allowing to reduce the size and weight of the components on the electronic board, obtaining a better result.
Advantages of SMD
There are many benefits to surface mounting
- Reduction of cost and production time of electronic circuits.
- Smaller components, increasing the space on the board and the amount of copper used.
- Minimizes the length of the tracks.
- Improves inductance and resistance.
- They withstand a multitude of acids, solvents, etc… This means that PCBs can be immersed in solder residue removal products.
Disadvantages of SMD mounting
- Thermal coefficients depend on the material.
- The reduction in size of the plate means that the dissipation surface is smaller. Although these are predictable effects that can be solved with a good design.
- Encapsulation is subject to length variations for thermal reasons.
In Fadesa Ingenieros we have the high precision machinery that is necessary for the assembly of all types of surface components. This machinery allows us great flexibility when making prototypes as well as small and medium series of electronic circuits. Encapsulation is subject to length variations due to thermal reasons.
Through-hole technology
Through-Hole Technology, better known by the acronym THT, is a type of technology that uses the holes made in the printed circuit boards for the assembly of the different electronic elements. In this way, electrical bridges are created between one side of the PCB and the other by means of conductive tubes.
This type of technology is less and less used, but it has a high mechanical performance between the component and the board, so they are currently used for components that require greater strength in assembly or larger size.
We perform the insertion of conventional components, welding on one or both sides and manual finishing.
In FADESA INGENIEROS, we use the selective wave machinery to weld the components once assembled, in this way, a precise welding is achieved without overheating of the components or use of molds.
Advantages of THT technology
Assembly of components that have to withstand high mechanical loads, e.g. terminals, connectors, wiring terminals, etc.
It is also a suitable solution for some components that have to withstand large currents.
- High mechanical and clamping performance.
- Good response with high power components.
- Lower initial cost of automation than SMD assembly.
- Best choice for mounting large components.
- Ideal for components requiring higher assembly strength.
The difference between SMT and THT
The so-called surface assembly technology refers to the chip component structure or suitable for surface assembly of miniaturized components, according to the requirements of the circuit placed on the surface of the printed board, with reflow soldering or wave soldering and other soldering processes assembled, forming a certain function of electronic component assembly technology. The differences between the installation and soldering of SMT and THT components are shown in the figure.
On the traditional THT printed circuit board, the components and solder joints are on both sides of the board. In SMT circuit board, the solder joints and components are on the same surface of the circuit board. Therefore, in the printed circuit board of SMT soldering machine , the through hole is only used to connect the circuit board on both sides of the wire, the number of holes is much smaller, the diameter of the hole is much smaller. In this way, the density of the circuit board assembly can be greatly improved.
Surface-mounted SMT components are functionally no different from plug-in components except in their packaging. Surface mounted packages that undergo high temperatures during soldering must have components and substrates with corresponding coefficients of thermal expansion. These factors must be taken into account in the design of a product.
The characteristics of SMT technology can be reflected in the difference between SMT and THT. From the perspective of assembly technology, the fundamental difference between SMT and THT is “gluing” and “inserting”. The differences are also reflected in the substrate, components, component morphology, solder joint morphology and assembly process.
Tropicalized protection for electronic circuits
The tropicalized protection treatment consists of protecting the cards in humid and/or corrosive environments. In Fadesa Ingenieros we have machinery for the application of varnishes and silicones.
The application of a layer of varnish can cover part or all of the circuit. The purpose of this layer of varnish is to give extra protection to the circuit, mainly against humidity.
It can be applied by spray, either manually or in automatic processes with varnishing machines and coats with a thin layer all parts of the circuit to be protected.
Electronic circuits operating in humid environments and with temperature changes, even when mounted in watertight enclosures, may suffer condensation, which will eventually oxidize and degrade the soldering and electronic components.
When these electronic circuits are mounted in outdoor luminaires, sometimes the sealing gaskets degrade over time and fail, allowing moisture to enter the luminaire. Tropicalization of the circuits, although it will also suffer degradation with moisture, will protect the solder joints and the LED, greatly extending the overall life of the luminaire.
Verification and start-up
At the end of the board assembly process, it is important to verify and test all the boards and electronic equipment that our customers require.
In the case of finished equipment, we have an assembly section to deliver the final products fully assembled, mounted, checked and packed.