Since IKOR Group was created, electronic components have been evolving constantly until today. At the beginning, all components were big compared to nowadays. And they all were what we call today PTH (Pin Through Hole), that is, components whose terminals are introduced in the PCB holes and welded on the opposite side of the component itself.
Surface mount technology was an important change. It was developed in the 60s, but it was the 80s before it became widely used. This technology is different from the preceding one in which the components are mounted and welded on the same face, without the need for holes in the printed circuit. This kind of technology is called SMT (Surface Mount Technology) and components welded this way are called SMD (Surface Mount Devices). Also, this type of SMD component can be assembled automatically, much more quickly than PTH components. But not all components can make use of SMD technology. This is the case of big size and high power components, such as transformers or power semiconductors with heat sinks.
Within SMD technology, evolution has aimed at making smaller components. On the one hand, it has been pushed on by the necessity to reduce costs and improve the performance of high frequency applications. Also, surface mount machines have improved their precision and allowed an increasing use of very small components.
The most widely-used electronic components, ceramic capacitors and resistances, are used typically in a rectangular format called chip. Some years ago, the most common were the 1026 size (3.2 x 1.6 mm and 1/4 W). But there is an increased use of smaller components, so today the 0402 (1.0 x 0.5 mm and 1/16 W) are very common. Current technology allows the use of even smaller components, almost invisible to the human eye, such as the 01005 (0,.4 x 0.2 mm and 1/32 W).
Integrated circuits have been used in many different formats. Initially, they were used encapsulated, with visible terminals on the plastic encapsulation sides, such as SOP, PLCC and QFP. Later, as test medium evolved, new components with less visible welds started to be used. These were called BTC (Bottom Termination Components), such as QFN and BGAs. The latter have some little balls instead of terminals on the bottom surface which, once welded, are not visible to the human eye, so they need other methods, such as X-rays, to be reviewed.
Smaller still are the components without encapsulation, such as the COB (Chip on Board), where the silicon is directly mounted on the PCB without a plastic encapsulation covering it. In this case, a different type of machine is needed to weld the wires coming directly from the silicon chip to the PCB’s pads, a process which is called wire bonding. They are covered by a drop of insulating material later on.
Another way of saving space is to mount one component on top of another, as it is the case of the POP (Package on Package).
PTH components have also evolved. As an example, one of the very widely-used systems, above all in connectors, is press fit technology, where the component is inserted in the PCB hole, like an ordinary PTH, but instead of being welded, the terminal makes pressure against the PCB hole, thus creating an electrical induction without weld.
A combination of both technologies (PTH and SMD) can be found in the process called Pin in Paste. The PTH component with terminals is inserted together with the SMDs in holes previously covered with welding paste, at the same time the rest of SMD pads have been applied, during the silkscreen marking or paste print. These PTH components are welded in the remelt oven at the same time as the SMD components.
Components have also evolved for ecological reasons and because of the health risks they pose due to some chemical elements which typically were used in some of the materials. The Restriction of Hazardous Substances, known as RoHS, forced the removal of lead terminals in electronic components. Halogen-free components, increasingly used, have eliminated such toxic elements. The halogens, which for example are used as flame retardants in the components’ plastic encapsulations, have been replaced by other elements that perform the same function but are less harmful to human health and the environment.
The components will continue to evolve and the challenges continue to be cost reduction, improved reliability, compliance with environmental laws and regulations, health and safety, and the adaptation to new applications of electronics.
The IKOR Group has been adapting to these changes, acquiring mounting machines capable of mounting size 01005 chip components, PLCC, SOIC or QFNs with a 0.3 mm pitch between pin centres (fine pitch) or BGAs with a 0.3 mm pitch.
IKOR has carried out projects based on Taguchi design experiments in order to optimise the process parameters to achieve the highest quality in the assembly of the most complicated components. We have also participated in R+D+i projects where the assembly of POP components has been tested and the assembly processes with conductive adhesives has been assessed. We are also participating, together with other European companies, in the development and assessment of new lower cost but high reliability materials for aerospace application components.
To detect hidden welds in BGA type components in IKOR, we have X-ray machines ( Xtech, Nordson) that analyse the quality of these welds, as well as test systems such as the boundary scan (Xtag) used to achieve a higher coverage when testing this type component.