If we had to choose the most important component of all those used during our manufacturing process, it would undoubtedly be the PCB. There are other components which are more expensive, cheaper, bigger, smaller, more complex, simpler… but the PCB always features in our circuits. It provides the basis for the other components and connects them up to each other electrically via copper circuit foils. The parts of these foils which are soldered to components are usually called soldering pads.
These pads are hugely important and the quality of the electrical connection that results when the component terminals and pads are soldered together will determine whether the product works correctly. This is where the PCB finish plays a key role. Although copper is a good conductor, it is an element which rusts very easily. This is why it is vital for the copper on the pads to be covered by a protective, conductive layer – the finish.
Many believe that some finishes are better than others and that when it comes to choosing a particular finish, it is merely a case of paying more to ensure a better finish that provides higher quality. But the right finish depends on the circuit, the types of components and the manufacturing process. If we analyse these factors, we’ll end up choosing the finish which best suits the features and manufacturing method of that product, and the best finish is not always the most expensive one. No single finish is better than another, but rather they all have their own advantages and drawbacks
It is essential to choose the finish wisely in order to achieve a higher quality product.The HASL finish is robust and very weldable, but it has little flatness and is not appropriate for components such as BGAs. The immersion tin finish is very flat but cannot withstand as many thermal soldering processes as the HASL or Enig finishes, which is what happens in the case of double reflow. On the other hand, Enig is more fragile and unsuitable for the press-fit process, whereas the opposite is true of immersion tin.
However, not only must we be familiar with the manufacturing process and components, but we also need to bear in mind the timescales for delivery, the minimum quantities that must be purchased and therefore any requirements with regards to environmental conditions or storage periods. These logistical aspects also come into play when choosing the most appropriate finish.
Therefore, such as we do in IKOR, a good initial analysis will enable us to find our ideal finish, helping to prevent many problems over the course of the product’s life cycle.