Technology’s improvements every day has made a lot of things possible through updates on what we currently have, affecting everything from the biggest machines we use to the smallest ones that make up the gadgets we use daily. The process of PCB fabrication has also been subject to many changes that have positively affected its development, essentially allowing people to make smaller and smaller versions of these, and in consequence allowing for the development of smaller, sleeker, and more advanced gadgets.
One of the most important parts of PCB fabrication is the putting of copper finishing on the surface of each board made. Copper finishing is known in the PCB fabrication industry as being as essential to the process as is breathing to us humans. Copper finishing is the main reason why PCBs are not susceptible to deterioration, as it prevents the corrosion of the board regardless of the climate you put it in. In its essence, the finish is used as a protection for the circuitry placed on the bard, and as a way to provide a surface for the soldering process.
In the past, the most used method of soldering used was the HASL, or the Hot Air Solder Leveling. However, as circuitries in each printed circuit board becoming more and more complex, and with each circuit board being required to take up less and less space, the use of this method has been deemed as being too impractical and difficult to maintain. The limitations that this process has given to PCB development has led experts to think of better solutions to solder materials in boards. Alternatives have been introduced recently in order to prevent encountering the problems with HASL.
Let us talk a bit more about HASL for a bit. This method has been the most used one in the industry for a very long time. The HASL process involves the immersion of circuit boards into molten tin or lead, and then removing the excess with the use of an air knife. This air knife will blow the board’s surface and will remove any excess molten tin that may have gotten on the board. The obvious benefit of this process is that since this PCB fabrication process would involve subjecting the boards to temperatures as high as 265 degrees Celsius, it would mean that future issues with delamination will easily be seen before any components that might cost a lot are attached to them.
Just some of the benefits of HASL include low costs given that this PCB fabrication process is both old and common, it is also easily available, can be worked on multiple times, and the process has a very long life span. However, the downsides to this process would include the quality being not so good since the surfaces might come off as uneven, and there will be lead content in the boards since this is the main ingredient in HASL. PTHs or Plated Through Holes are also reduced.
Here are some of the alternatives that have been used by board fabrication companies as a substitute to HASL:
- Immersion Tin.
The benefits of this process includes not having to deal with bumps on the surface given that it results in flat surfaces, as well as being easy to rework with and not having and Pb of any kind. In addition, this has also been considered as the best choice for a Press Fit Pin Insertion.
On the other hand, this Immersion tin can easily cause handling damage, and the process uses thiourea, which is known as a cancer-causing material. The exposed tin during the last stage of the process is also susceptible to corrosion, and the process itself is not reliable when it comes to assembly or multiple reflow.
- OSP or Entek.
This preserves the surface copper and prevents oxidation from touching it with the use of a protective material over the exposed copper. The compound used is water based, and so it is considered as being environmentally friendly.
Just like the immersion tin, it is also re-workable and produces flat surfaces, although this actually costs less to do unlike the other two methods mentioned. On the other hand, the disadvantages include the fact that thickness cannot be exactly measured with this process, and the shelf life tends to be short. It is also not good for plated through holes (PTH), and the products can be difficult to handle due to their sensitivity. Not only that, there are times when PCB produced with this method can actually experience problems with ICT, though this is rare.
PCB fabrication is a multi-step handle that is for the most part conveyed by machines. The printed circuit board are a standout amongst the most vital segments in the realm of hardware today.