PCB Assembly

In English it is Printed Circuit Board (PCB)but in Brazil, it is known as Placas de Circuito Impresso (PCI). In the world of electronics it is widely used and can be considered the most important electronic component because it has the function of integrating all others in the same electrical circuit. It contains the determinations of a circuit according to the way in which the current is traced, in short, an electronic circuit is a set of components grouped on a previously designed board.

The design of the boards is a document called Gerberis an open ASCII vector format for printed circuit board designs. It is the de facto standard used by the PCB to describe the images of the printed circuit board: copper layers, solder mask, caption, drill data, etc.

We can compare this format with a photolithography, it contains the matrix and design of what will be the PCB for large scale and further manufacturing PCB assembly. It is in this assembly that all other components, such as: sockets, processors, capacitors, resistors, varistors, connectors, terminals, gas spark, etc. are positioned and welded.

A bit of the history of electronic boards

The first PCB’s were produced around 1943, according to findings, the boards were initially developed for military purposes, because the vast majority of intelligence systems until then were widely used, the military needed them for their communication radios, to improve contact in any crucial situation. Before the development of PCBThe circuits were composed of the components welded on their own terminals, this method became known as spider, due to its own appearance.

Even before any speculation about the boards, the Austrian engineer Paul Eisler was considered the developer of the boards due to some records of his studies, the vast majority of people claim that he was the creator of the system, a little earlier, in 1925 there was another record on the subject, being him of Charles Ducas. He believed that if he deposited a little conductive paint on an insulating substrate, he would obtain the phenomenon named "Printed Circuit”. After some time, specifically after the Second World War, they began to be used in more common tasks such as transistorized systems, and more common system-oriented tasks.

How is PCB made?

Nowadays, boards are more used in electronic devices, in the construction of integrated circuits, the PCB’s are very useful, due to their meticulous manufacturing, previously in principle a material called phenoliteThe name of the insulating board was known by the brand that manufactured the boards. They carry a mixture of phenolic resin with a small touch of chopped paper or wood sawdust, as after a while the material began to present problems, were perfected with more resistant and reliable types of materials. First of all a board was developed with fiberglass and epoxy resin, these boards are a great choice due to the ability to use several layers reducing the size of the circuit, there is also the board that makes junction with phenolite and fiberglass, and finally we have the one of metalcoreThe base is made of aluminium or copper coated with an insulating material.

The way they are manufactured begins with the development of an electrical schematic via software, which can carry out a simulation of how the circuit will work and the 3D visualization of the board. The software is responsible for generating a document in drawing form, Gerberwhich defines the path along which the current will travel, this process was named "trails". These tracks can be made with only one face, single face, on both sides, i.e., a double face or even in inner layers that are called multi-layers, which in turn each of these layers are known as layer.

Types of PCB assembly

There are two types of PCB assembly:

1. SMT Assembly (Surface Mounting Technology) Assembly using SMD components (Surface Mounting Devices)
2. THT Assembly (Through Hole Technology) Assembly using PTH components (Pin Through Hole)

The PTH PCB assemblyis where the component terminals are inserted into the holes of the PCB and soldiers on the other side, it's usually a manual process. As for SMD PCB assembly is made without the need for holes, the components are positioned millimetrically by machines and welded on the surfaces of the PCB.

The SMD needs a more agile and precise assembly, due to the procedure being carried out mostly by machines, since the components are difficult to handle by people, as they are of a very small size. The first step of the process is to apply a solder paste through a printer, i.e. a printer by means of a stencil, which is a metal plate with precise openings in the places where the paste should be deposited. The paste is a chemical composition that serves to fix the component that will be inserted on the board through the insertion machine, which collects the component from the roller and places it on top of the paste that has been deposited on the board, this is done due to suction made by compressed air. The positions where the components are to be deposited are defined in the form of parameters for the machine, by means of a document almost always in TXT format. The next step is the re-melting, where the board will pass through a very high temperature to melt the solder paste and connect the terminals of the components to the solder area of the board. And to finish this process, the inspection is performed. AOI (Automated Optical Inspection) occurs through a programming made with the model board, to make the comparison with the produced material.

The procedure carried out for PCB assembly PTH is a little different, in this assembly the components are inserted manually into the board in cells, stations or production lines with belts. The boards are placed on the pallets, then they are placed on the conveyor belt of the welding machine, where the board will gain a layer of welding flux and will pass over a tin tank, in waveform, which will have the purpose of welding the inserted components. This tank can be composed of two types of soldering, with lead tin or Lead Free, without lead. Soon after passing through a cooling period, the plates go through the process of visual inspection, or even tests.

How to contract PCB assembly

Currently the Cromatek offers two types of contract to perform PCB assembly, they are Labor, in this method the customer is responsible for logistics and provides all the components needed to supply the assembly line. The other method is called TurnKey, where the Cromatek is responsible for all the logistics, supply, storage and assembly of the PCB ensuring all the components in the assembly line of the boards and their monthly replacement. The method Turn KeyThe assembly company is considered the most advantageous for both sides, especially if the company responsible for the assembly has an infrastructure prepared for the whole process. Together with CromatekYou can choose which option is best for your company, since we are a reference in board assembly. Come visit us and get to know our structure.

Request a quote for electronic board assembly with Cromatek.