Prevent Oxidation in PCB Fabrication Assembly
Various types of corrosion can plague PCBs in the manufacturing process. Understanding the causes of these issues and taking steps to prevent them can help make your circuit boards more durable and functional.
Corrosion happens when oxygen bonds with metals. This reaction creates rust, which flakes off the metal and loses its valuable chemical properties. All metals are prone to oxidation, but some, like gold, silver, and graphite, are highly resistant to it, while others, including copper, nickel, and thin layers of tin, are very susceptible to it. Since circuit boards are largely made of metals, they are prone to this problem.
In a pcb fabrication assembly, the first step in this process involves applying solder paste to the board. This is done with a stencil, similar to the way screen-printing a shirt works. The stencil allows assemblers to only apply the solder paste to specific areas of the would-be PCB where components will sit in the finished product.
This is important because if any of the copper on a PCB is exposed, it can become oxidized and corroded. This leads to short circuits and other problems. To avoid this, you can brush the surface of the PCB with a lint-free cloth soaked in isopropyl alcohol. Then, rinse the surface with water.
How to Prevent Oxidation in PCB Fabrication Assembly
A common type of oxidation in the PCB fabrication assembly process is electrolytic corrosion. This happens when ionic contaminants come into contact with two neighboring copper traces. This can result in the formation of small metal slivers between the traces, which can short out the entire circuit board or a section of it.
Another type of oxidation in the PCB assembly process is chemical etching. This occurs when a mask is used to protect a certain area of the PCB during etching. The chemicals used to etch the PCB can contaminate the copper that isn’t protected by the mask and cause it to become oxidized. The resulting corrosion can be very damaging and can lead to the need to replace a component or even the entire board.
The final kind of oxidation in the pcb fabrication assembly process is creep corrosion. This is caused by sulfur in the air and can be extremely dangerous to the integrity of a circuit board. To avoid this, it’s best to work with a PCB contract manufacturer that is familiar with the dangers of this issue and knows how to prevent it. This can be accomplished by working in a facility with a low-humidity environment and using conformal coatings that can shield against external elements.
In addition to keeping your pcbs in a low-humidity environment, the quality of the materials you use to fabricate them can also play a big role. Choosing a material with a high glass transition temperature and using ENIG or OSP finishes is one way to minimize the risk of corrosion. Another effective measure is to conduct regular inspections and maintenance to ensure that the PCBs are in good shape.
