One of the most important innovations in the information age is the silicon based chip. Every year as technology continues to develop we are able to cram more and more circuits onto a microprocessor chip which brings the possibility of smaller, cheaper and more powerful electronic devices. These days, the chip has now become the size of a thumbtack and printed circuit boards are getting smaller and smaller.
What are Printed Circuit Boards?
A printed circuit board is designed to electrically connect and mechanically support many different electronic components using conductive pathways, signal traces and tracks. These types of printed circuit boards are used in almost all commercially produced electronic devices, as they allow a fully automated assembly process. The PCB consists of a piece of insulating material, such as phenolic resins or epoxy, into which the integrated circuits (chips) and other electronic components can be interconnected and mounted to create a circuit.
When it comes to manufacturing these boards and ensuring that they work as they are intended to, one of the most important factors to control is to reduce exposure to humidity and moisture. PCBs should always be kept clean and dry.
The Damage that Moisture can Cause to a PCB
When printed circuit boards are being assembled, exposure to high humidity can lead to the beginning of microscopic corrosion on the surface of the circuit board. This will cause adhesion failure, decreased performance and surface defects within the printed circuit board. The moisture will become absorbed and will make cuts within the bridging of the tiny microscopic circuit lines. This can result in circuit failures.
This is why the air in rooms where PCB’s are manufactured is kept at a certain controlled level of humidity. The rooms are maintained at a relative humidity level of 20% to 35% and are also kept at a temperature of 20 degrees Celsius.
It is also important to avoid moisture due to the quartz crystals that are often incorporated with PCB’s. These crystals are put through a controlled aging process which controls their humidity level and prevents them from absorbing water vapour.
What Happens in High Humidity?
When printed circuit boards are exposed to high humidity, this is when problems occur. Exposure to high humidity can lead to corrosion occurring upon the surface of the circuits on the board itself. The tiny and imperceptible layers of corrosion will decrease capacitance and increase the electrical resistance. The moisture will cause a huge drop in performance as well as resulting in surface defects and adhesion failures.
The moisture and humidity in the air can also lead to corrosion of metals, as well as resulting in the formation of metal filaments. These can grow between the tracks or pads on flexible or rigid printed circuit boards. These metal ‘dendrites’ can grow very quickly and can cause a failure of the circuit board in only 30 minutes or sometimes slowly over several weeks. Their rate of growth depends on the voltage and the surface moisture. The smaller and denser the circuit is, the more it will be affected by a moisture problem.
What Can You Do?
When manufacturing, assembling or storing printed circuit boards, it is important to create a very low humidity environment that will reduce the risk of damage to the board. This is usually done with a climate control system such as a dehumidifier. A good dehumidifier will be able to keep relative humidity down to as low as 1% or even lower.
Another solution is to use Conformal Coating, which is a material you can apply that will protect the PCB’s from moisture, temperature extremes and other factors. This way you will be able to keep your printed circuit boards working their best for as long as possible.
Ian Appleton is a writer who has a keen interest in the technology sector. He recommends finding a specialist if you require help with PCB repairs, computer maintenance or internet security issues.
