What is Outgassing?

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Sep 22, 2020

Outgassing refers to the release of gas which is dissolved or trapped inside materials when the surrounding temperature or pressure changes. Changes in surroundings result in sublimation or evaporation of the trapped volatile substances or chemicals. Usually, the substances that cause outgassing are volatile, which means even small changes in the surrounding can make them convert into their gaseous form.

Outgassing is an unwanted phenomenon that poses some big challenges in the electronics industry. The phenomenon can lead to various complexities and even result in equipment failure. Outgassed substances are nothing but contaminants.

In Printed Circuit Boards (PCB) outgassing commonly occur due to wave or hand soldering. During the soldering processes, moisture near a through hole evaporates due to heat and creates a void on the surface of the PCB. When there is a change in the environment where the PCB is operating, the outgassed material can condense and land on other parts of the board causing short circuits or blocking signal flow. This can cause electronic equipment to malfunction. Click here to learn more about PCB Outgassing.

Outgassing is also a challenge for electronics that are used in Space. Circuit boards and equipment used in space witness rapid and extreme temperature variations, which can result in outgassing. This is a huge challenge, as if happens to a circuit board in space, there is no easy way to repair it. Space agencies such as NASA and ISRO maintain a list of materials that have low-outgassing properties and can be used in space crafts and space missions as outgassed products can condense onto solar cells or optical elements and block them. 

In one such incident, NASA’s Stardust space probe started providing reduced image quality due to outgassing of an unknown substance from the charged-coupled device (CCD) sensor of the navigation camera. The Cassini space probe also faced a similar issue due to outgassing from its narrow angle camera. For components to be space-qualified, they much be tested for outgassing.

Outgassing can be reduced by selecting proper manufacturing methods. Heating of individual components, if possible, before being put to real world applications can also help in reducing outgassing. Space-grade certifications such as MIL-STD-883, MIL-PRF-38534, MIL-PRF-38535, etc. require the components to be tested for outgassing to get certified as “space ready”. Click here to know more about the challenges faced by electronic components in space.

Outgassing can also be observed in our day-to-day lives. For example, the smell of a new car. The combination of outgassed chemicals and a closed environment leads to the smell. The smell goes away after a few days because the volatile materials get outgassed completely.

Lifting and Blistering on the surface due to outgassing of polymers

It is to be noted that although exposure to these outgassed substances don’t cause health issues in the short term, long term exposure can have harmful effects on the human body. Moisture, lubricants, adhesives, etc. are the most common sources of outgassing but metals and glass can also release gas due to impurities.

Another example that we all might have witnessed is the unknown smell while unboxing new products which is, in fact, caused by the outgassed chemicals/substance. As the product remains sealed in a box or package, the outgassed chemical gets trapped and unboxing releases them all at once which makes it noticeable to us. It is easier to witness outgassing in closed environments.